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USMLE Step 1 High‐Yield Neurology Topics
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Neurology
High Yield USMLE Step 1 Notes
Welcome to the Neurology High-Yield Notes for Step 1.
These are the most commonly tested topics on the exam—ideal for quick review in your last 2 weeks before the exam, when you’re short on time, or when you’re just starting out and want to focus on what is high yield. Created and peer-reviewed by physicians who scored 260+ on Step 1 in a Q&A style to reinforce active learning.
How to use this file
- Read the question ➔ cover the answer ➔ self-quiz before revealing.
- Review the NOTES ➔ they include high-yield details you don’t want to miss.
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- Don’t forget to watch the video lessons that go with this file. Learn more here.
Table of Contents
- Neuroanatomy, Embryology & Neurophysiology
- Cerebrovascular Disorders
- Neurodegenerative disorders
- Peripheral Nerve and Neuromuscular Disorders
- CNS Tumors
- Seizures & Epilepsy
- Headaches, Facial Pain & Cranial Neuralgias
- CNS Infections
- Spinal Cord lesions
- Movement Disorders, Sleep & Metabolic Syndromes
- ENT
- Ophthalmology & Visual Pathway Disorders
Neuroanatomy, Embryology & Neurophysiology
1. A 36-year-old man with a rash and a painful ulcer on the anterior tongue. The lesion is 2 cm in front of the foramen cecum. Which nerve carries pain sensation from this region?
➔ Mandibular division of the trigeminal nerve (CN V₃) (As it provides sensation to the anterior ⅔ of the tongue)
Nerve supply to the tongue
| Function | Region | Nerve |
|---|---|---|
| Motor | All muscles | CN XII (Hypoglossal) |
| Palatoglossus | CN X (Vagus) | |
| General Sensation | Anterior ⅔ | CN V₃ (Mandibular) |
| Posterior ⅓ | CN IX (Glossopharyngeal) | |
| Taste | Anterior ⅔ | CN VII (Facial) |
| Posterior ⅓ | CN IX |
2. A 21-year-old woman has frequent recurrences of painful grouped vesicles. Which motor protein mediates the viral particle transport during reactivation?
➔ Kinesin (Kinesin mediates transport of herpes simplex virus from the sensory ganglion → to the skin during HSV reactivation (anterograde transport).)
- Note: During initial HSV infection → HSV travels along sensory neurons using the dynein motor protein → to reach the sensory ganglia where it becomes latent (called retrograde transport)
- During reactivation, reactivated viral particles are transported back to → the peripheral nerve using the kinesin motor protein (called anterograde transport).
3. A 5-year-old boy has gained excessive weight despite constant hunger. He also reports morning headaches. Which hypothalamic nucleus is likely damaged?
➔ Ventromedial nucleus (The ventromedial nucleus regulates satiety → its damage leads to hyperphagia and obesity.)
- Note: Key Hypothalamic Nuclei:
Ventromedial nucleus → Triggers satiety - Stimulated by leptin
- Lesion leads to → Constant hunger and obesity (occurs in craniopharyngioma)
Lateral nucleus→ Triggers hunger - Stimulated by ghrelin, inhibited by leptin
- Lesion leads to → Loss of appetite, weight loss (occurs in Anorexia)
4. A 4-year-old boy is brought to the clinic during a heatwave. His parents say he has had a high fever and is not sweating, even in hot weather. Examination shows flushed skin and elevated body temperature. A lesion in which hypothalamic nucleus is most likely responsible for his symptoms?
➔ Anterior nucleus (The anterior hypothalamic nucleus controls cooling → its damage impairs sweating and heat dissipation → leading to hyperthermia.)
- Note: Key Hypothalamic Nuclei:
Anterior nucleus → Controls cooling (A/C = Anterior Cooling) - Activates parasympathetic system
Posterior nucleus → Controls heating ( “Hot Pot = Posterior Heating”) - Activates sympathetic system
Suprachiasmatic nucleus (SCN) → Controls circadian rhythm - It gets light input from retina to control circadian rhythm (SCN = Sun-Censing Nucleus)
5. A 39-year-old woman with bipolar disorder delivers a stillborn baby missing much of the scalp and brain. What maternal factor most likely caused this abnormality?
➔ Valproate use (Valproate inhibits folate metabolism → increasing the risk of neural tube defects as anencephaly (which is the absence of brain and calvarium)
- Note: Anencephaly occur due to failure of neuropore closure (by week 4)
- AFP will be increased
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6. A newborn is found to have a small dimple with a tuft of hair over the lower back. There are no neurological deficits, and imaging shows no herniation of neural contents. Which of the following is the most likely diagnosis?
➔ Spina bifida occulta
Neural tube defects:
| NTD type | Herniation | Key Features |
|---|---|---|
| Spina bifida occulta | None | Tuft of hair or skin dimple |
| Meningocele | Meninges only | No neural tissue herniation |
| Myelomeningocele | Meninges + neural tissue | Often with Chiari II, hydrocephalus |
| Myeloschisis | Exposed neural tissue | No skin or meningeal covering |
| All have ↑ AFP except Spina bifida occulta | ||
7. A 21-year-old woman with months of headache and gait instability. MRI reveals cerebellar tonsils herniating through the foramen magnum. The most likely cause?
➔ Chiari I malformation (It is mild herniation of cerebellar tonsils into the spinal canal)
- Note: Adult patient + headache + cerebellar tonsils herniation→ think Chiari I malformation
- VS Chiari II malformation which occurs early in life as a result of herniation of cerebellar vermis and tonsils, often along with the medulla leading to → obstructive hydrocephalus
8. A peripheral nerve injury results in the breakdown of the distal axon and myelin. Which process is responsible for clearing the debris in the PNS?
➔ Wallerian degeneration (It is the process where the distal axon and myelin breakdown after nerve injury → then microglia (in CNS) or Schwann cells (in PNS) clear the debris)
- Note: When a axonal injury occurs:
→ Neuronal cell body undergoes chromatolysis → in effort to repair the axon
→ The axon proximal to the injury retract and the cell body sprouts new protrusions that graw for potential reinnervation.
→ The axon distal to the injury undergoes Wallerian degeneration - Chromatolysis characterised by:
– Nissl dispersion
– Cell swelling
– Nucleus displacement to the periphery
9. A newborn is found to have a developmental brain abnormality involving poor formation of myelin in the central nervous system. The cells affected in this condition normally come from which embryological tissue?
➔ Neuroectoderm (It gives rise to the brain and spinal cord, including glial cells like oligodendrocytes which myelinate CNS axons)
- Note: CNS & PNS Origins
- Neuroectoderm develops into → CNS neurons, astrocytes, oligodendrocytes and ependymal cells.
- Neural crest (S-100+) develops into → PNS neurons, Schwann cells and adrenal medulla.
- Mesoderm develops into → Microglia (macrophage-like).
10. A kid with morning headaches and nausea. Imaging reveals a posterior fossa mass with dilation of the lateral and third ventricles, while the fourth ventricle appears normal. The most likely location of the obstruction?
➔ Cerebral aqueduct (symptoms suggest hydrocephalus, dilation of the third and lateral ventricles indicates cerebral aqueduct obstruction)
- Note: Types of Hydrocephalus:
- Non-communicating (obstructive) → Blockage of CSF flow within the ventricles or at the cerebral aqueduct, foramen of Monro, or fourth ventricle
- This leads to → One or more ventricles are dilated, while others may be spared depending on the location of the blockage
- Communicating occurs due to → ↓ CSF absorption (e.g., arachnoid granulation dysfunction in meningitis).
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Cerebrovascular Disorders
11. A 65-year-old man comes to the ER after severe bleeding. He remains unresponsive after successful resuscitation.Which brain region is most vulnerable to ischemic injury in this setting?
➔ Hippocampus (It is the most sensitive brain region to hypoxia/ischemia due to its high metabolic demand and role in memory processing.)
- Note: Other susceptible regions include → Watershed zones of the gastrointestinal tract → which include the splenic flexure and rectosigmoid junction
12. An 81-year-old woman was found unconscious at home and died during transport to the hospital. Autopsy shows neurons with red cytoplasm and pyknotic nuclei in the right MCA territory. How long ago did the cerebral injury most likely occur?
➔ 12–24 hours (neurons with red cytoplasm and pyknotic nuclei refers to → red neurons which appear 12-24 hrs after ischemic injury)
- Note: Timeline of Ischemic injury to CNS:
- Day 1: red neurons appear, characterized by → eosinophilic cytoplasm + nuclear shrinkage
- Day 2-3: Acute inflammation occurs characterized by → neutrophil infiltration + necrosis
- Day 4-5: Microglia (CNS macrophage) → phagocytose debris
- After 2 weeks: Glial Scar is formed → leads to cystic cavity in the infarcted area
13. A 60-year-old man with sudden right arm and leg weakness. MRI shows a small infarcted area in the internal capsule. What is the most likely underlying cause?
➔ Hypertensive arteriolar sclerosis (Chronic hypertension causes lipohyalinosis and thickening of small penetrating arteries leading to → lacunar infarcts in deep brain structures like the internal capsule)
- Note: Lacunar Stroke:
→ Is a small sized infarct in deep brain structures that leads to pure sensory or pure motor deficits
→ Caused by lipohyalinosis and microatheromas due to chronic hypertension
→ Internal capsule injury is a subtype of lacunar stroke that leads to → pure motor hemiparesis
14. A 60-year-old man presents with sudden weakness in his right arm, more pronounced than in his leg. Neurologic examination reveals contralateral weakness in the right arm and leg, but no facial weakness. What is the most likely cause of this patient’s symptoms?
➔ Middle cerebral artery occlusion (MCA occlusion typically causes contralateral weakness → particularly affecting the upper limb more than the lower limb)
- Note: Key vessel in Cerebrovascular attack (CVA)
If arm weakness > leg weakness → think Middle cerebral artery occlusion (MCA).
If leg weakness > arm weakness → think Anterior cerebral artery occlusion (ACA).
If leg weakness = arm weakness & no facial involvement → think Lenticulostriate (lacunar stroke)
If extremity weakness on the opposite side of face weakness (cross sign) + having additional cranial nerve signs → think brainstem involvement.
15. A 55-year-old woman has a sudden headache and blurred vision. She becomes unconscious en route to the hospital. CT shows a hemorrhage compressing the medial temporal lobe against the tentorium. Which cranial nerve is most likely affected?
➔ Oculomotor nerve (The medial temporal lobe herniates (uncal herniation) and compresses the oculomotor nerve (CN III) → leading to pupillary dilation and eye movement abnormalities)
- Note: Intracranial bleeding + cranial nerve deficit + sudden loss of consciousness → think brain hernia.
Types of Herniation
| Type of Herniation | Cause | Effects |
|---|---|---|
| Uncal | Temporal lobe herniation | Ipsilateral oculomotor nerve compression (fixed and dilated pupil) |
| Subfalcine | cingulate gyrus under the falx cerebri | ACA compression |
| Tonsillar | Cerebellum through foramen magnum | Coma and death |
16. A 60-year-old man with sudden right-sided weakness and confusion. BP is 190/100 mmHg. CT scan shows an intracerebral hemorrhage. What is the most likely underlying cause?
➔ Charcot-Bouchard aneurysm rupture
- Note: Hypertensive patient + Non-traumatic intracerebral hemorrhage in deep brain structure → think Charcot-Bouchard aneurysm rupture. (Usually <1 mm)
- Charcot-Bouchard aneurysm rupture causes intracerebral hemorrhage VS Saccular (berry) aneurysms which result in subarachnoid hemorrhage (Usually 2-25 mm)
- Secular aneurysm most commonly occur at the circle of willis
17. A 75-year-old man presents with sudden visual loss and right-sided sensory deficits. CT shows multiple small bleeds in the occipital and parietal lobes. He had a frontal lobe hemorrhage 2 years ago. He has no history of hypertension. What is the most likely cause?
➔ Cerebral amyloid angiopathy (It is caused by β-amyloid deposition in cerebral vessel walls → leading to recurrent lobar hemorrhages in elderly.)
- Note: This occurs independently of systemic amyloidosis which involves:
→ AL-amyloid deposition rather than β-amyloid deposition in organs like the kidneys, heart, and liver).
18. A 68-year-old man presents with sudden dizziness, headache, and ataxia. CT scan shows a cerebellar vermis hemorrhage. What neurologic finding is most likely seen?
➔ Truncal ataxia (The cerebellar vermis controls axial/truncal coordination)
- Note: Injury to cerebellar vermis hemorrhage → leads to truncal ataxia (wide-based gait) + vertigo + nystagmus.
- VS injury to the cerebellar hemispheres which affects limb coordination, leading to limb ataxia, dysmetria, and intention tremor
19. A 66-year-old man with atrial fibrillation awakens with left lower limb weakness and a positive Babinski sign. Where is the lesion most likely located?
➔ Right anterior cerebral artery (ACA occlusion → leads to Frontal lobe involvement → leads to contralateral leg weakness or sensory loss + urinary incontinence)
- Note: Atrial fibrillation + sudden onset focal neurologic deficit → think embolic Stroke
- Presence of positive Babinski sign indicates upper motor neuron lesion
20. A 61-year-old man with hypertension and a smoking history develops transient right arm weakness and aphasia. Symptoms resolve within an hour. What is the best medication for secondary prevention?
➔ Aspirin + Statin (This patient had a transient ischemic attack (TIA) → antiplatelet therapy (aspirin) and a statin reduce the risk of future strokes)
- Note: Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction with symptoms resolving within 24 hours and no permanent damage.
- Management includes
→ Aspirin + Statin
→ Blood pressure management
→ Diabetes management
→ Carotid Doppler to → check for narrowing - This management is also indicated for patients with ischemic stroke
21. A 66-year-old woman presents with sudden vertigo, right facial numbness, left extremities sensory loss, and ↓gag. Which artery is involved?
➔ Posterior inferior cerebellar artery (PICA)
- Note: Left-sided weakness but right-sided cranial nerve affection → Indicates a “Crossed Signs” pattern, which is classic for brainstem lesions.
- To answer all brainstem ischemia questions
→ You need to use the rule of 4 for localization of affected area:
| Four Cranial Nerves in Each Section | Midbrain: CN III, IV (except this) Pons: CN V, VI, VII, VIII Medulla: CN IX, X, XI, XII |
| Four Midline Structures | 1. Motor pathway (Corticospinal tract) → Contralateral weakness. 2. Medial lemniscus → Contralateral loss of proprioception/vibration. 3. Medial longitudinal fasciculus (MLF) → Internuclear ophthalmoplegia. |
| Four Side (lateral) Structures | 1. Spinocerebellar tract → Ipsilateral ataxia. 2. Spinothalamic tract → Contralateral pain/temp loss. 3. Sensory CN V nucleus → Ipsilateral facial pain/temp loss. 4. Sympathetic tract → Ipsilateral Horner syndrome. |
| Four CNs with Motor Components in the Midline: | CNs that divide evenly into 12: III, IV, VI, XII (3, 4, 6, 12) |
→ Then Identify the supplying artery;
Created with BioRender.com
Here is how it is done for the previous question:
- Is it Lateral vs. Midline lesion?
→ Presence of facial numbness → means Sensory Nucleus of CN V involvement → indicating lateral lesion
→ Presence of extremity sensory loss → means Spinothalamic tract involvement → indicating lateral lesion - What is the Cranial Nerve Affected? (to determine the affected brain stem section)
→ ↓gag → means CN IX, X involvement → which lies in the medulla (specifically lateral medulla) - What artery supplies this area?
→ Lateral medulla is supplied by Posterior inferior cerebellar artery
22. An old man with acute weakness and diplopia. Exam shows left ptosis and dilated pupil, along with right hemiparesis. Which artery is involved?
➔ Left PCA
- Note: Right-sided weakness but left-sided cranial nerve affection→ Indicates a “Crossed Signs” pattern, which is classic for brainstem lesions.
- Again follow the rule of 4 to know the lesion localization then determine the blood supply of the affected area
Here is how it is done:
- Is it Lateral vs. Midline lesion?
→ Body weakness → Corticospinal tract (Motor Pathway) → Medial - What is the Cranial Nerve Affected?
→ Indicates CN III (Oculomotor Nerve) involvement → indicates Midbrain lesion. - Is it left or right?
→ Left ptosis and dilated pupil, along with right hemiparesis. → indicates left sided lesion - What artery supplies this area?
→ Left medial midbrain is supplied by → Left Posterior Cerebral Artery (PCA)
23. A 23-year-old man presents after head trauma. He briefly loses consciousness at the scene, then regains full alertness, but a few hours later becomes unresponsive. Between which structures is the bleeding located?
➔ Bone and dura mater (Transient loss of consciousness followed by → recovery indicates lucid interval → which is a classic sign of epidural hematoma)
- Note: Mechanism includes → injury leading to → skull fracture usually at the pterion → injures the middle meningeal artery (a branch of maxillary artery) → leads to bleeding between skull and dura (Epidural hematomas)
- Appears on imaging as biconvex hematoma
24. A 2-month-old infant with lethargy and a bulging anterior fontanelle. Fundoscopic examination reveals bilateral retinal hemorrhages. What is the most likely cause?
➔ Shaken baby syndrome (infant + Subdural hematomas + bilateral retinal hemorrhages + multiple posterior rib fractures → think shaken baby syndrome)
- Note: Suspect child abuse in cases of Shaken baby syndrome
25. An old woman with altered mental status. Head CT scan shows a crescent-shaped, hyperdense lesion. What vessel injury is the most likely cause?
➔ Cortical bridging veins (These veins traverse the subdural space and are prone to tearing)
- Note: Mechanism of chronic subdural hemorrhage includes
→ Elderly patient with brain atrophy → has fragile cortical bridging veins in the subdural space → then recurrent mild trauma leads to → cortical bridging veins rupture → causing chronic subdural hemorrhage
→ Appears on CT as hypodense crescent shaped lesion that crosses suture lines - VS Acute subdural hemorrhage mechanism which includes;
→ Younger patient → exposed to trauma → cortical bridging veins rupture → leading to acute subdural hemorrhage
→ Appears on CT as hyperdense crescent shaped lesion that crosses suture lines
26. A 27-year-old man involved in a high-speed car accident presents in coma. Brain histopathology shows widespread axonal swelling, especially at the gray-white matter junction. What is the underlying mechanism?
➔ Interruption of the white matter tracts (due to shearing forces from rapid acceleration-deceleration injury → causing diffuse axonal injury)
- Note: Often results in coma or severe disability
27. A 32-year-old man with a subarachnoid hemorrhage (SAH). Five days later, he developed a new right-sided weakness. What medication could have prevented this?
➔ Calcium channel blocker (e.g., nimodipine) (CCBs prevents delayed cerebral vasospasm, a common complication after SAH that can lead to ischemic deficits)
- Note: SAH + focal neurologic deficit → think Cerebral vasospasm (days after SAH)
- Other complications include
– Hydrocephalus → Occurs due to dysfunction of CSF absorption (days after SAH)
– Rebleeding → managed with controlling blood pressure → highest risk in the first hours after SAH
28. A premature infant becomes lethargic and hypotonic. Cranial ultrasound reveals blood in the lateral ventricles. What is the most likely source of bleeding?
➔ Germinal matrix (This highly vascular region in premature infants is prone to hemorrhage due to its fragile capillaries and poor autoregulation of blood flow.)
- Note: Preterm infants + No vitamin K administration at birth + lethargy and hypotonia → think Intraventricular hemorrhage (occurs at the germinal matrix)
Neurodegenerative disorders
29. A 75-year-old man with progressive memory loss and difficulty managing daily activities. Babinski is positive on the right side. What is the most likely diagnosis?
➔ Vascular dementia
- Note: Dementia + one of the following: Stepwise cognitive decline, Focal neurologic deficit, or Imaging shows multiple infarcts → Think Vascular dementia
30. A 65-year-old woman presents with progressively slowing movements, muscle rigidity, and a resting tremor. Her facial expression is decreased, and her gait is shuffling. What is the most likely diagnosis?
➔ Parkinson’s Disease (Tremor + Rigidity + Akinesia + Postural instability (TRAP) → think Parkinson’s Disease)
- Note: It is a progressive neurodegenerative disorder characterized by loss of dopaminergic neurons in the Substantia Nigra pars compacta.
- Histology: Presence of Lewy bodies (eosinophilic cytoplasmic inclusions containing α-synuclein).
- Gross pathology: Depigmentation of the Substantia Nigra due to neuronal loss.
31. A 54-year-old man with behavioral changes over 2 years. He has become disinhibited and irritable, makes inappropriate jokes, and displays poor insight. Which brain regions are most likely affected?
➔ Temporal and Frontal cortices (symptoms indicate frontotemporal dementia)
- Note: Frontotemporal dementia affects regions responsible for personality and social behavior.
- Symptoms include apathy, compulsive behaviors, and executive dysfunction.
32. A 42-year-old woman with choreiform facial and limb movements and recent mood changes. Family history reveals a fatal neurodegenerative disorder. What is the likely diagnosis?
➔ Huntington disease (chorea + aggression + depression + dementia → think Huntington disease)
- Note: Caused by CAG trinucleotide repeat expansion on chromosome 4
- Pathology: Caudate nucleus atrophy → leads to enlarged lateral ventricles on imaging
- Neurotransmitter Changes; ↑ Dopamine, ↓ GABA, ↓ Acetylcholine
33. A 72-year-old woman with increasing forgetfulness. She got lost while driving a year ago. The most likely pathological finding in this patient’s brain?
➔ Neuritic plaques (they are extracellular deposits of beta-amyloid protein that accumulate contributing to Alzheimer’s disease)
- Note: Alzheimer’s dementia: Is the most common cause of Dementia.
- Characterized by:
→ Progressive memory loss
→ Brain atrophy (especially hippocampus)
→ Neurofibrillary tangles
→ Amyloid angiopathy,
→ ↓ Acetylcholine.
→ Neuritic plaques composed of beta-amyloid protein
VS Other causes of dementia; - Dementia + early personality change → Frontotemporal dementia
- Rapid progressive dementia + myoclonus → prion disease (spongiform degeneration)
○ There is ↑ 14-3-3 protein in CSF
34. An 80-year-old man presents with progressive cognitive decline, vivid visual hallucinations, and recent onset of tremor and bradykinesia. His family notes that the cognitive symptoms started several months before the motor findings. What is the most likely diagnosis?
➔ Dementia with Lewy Bodies (Dementia + visual hallucinations + early or concurrent parkinsonism (within 1 year of cognitive decline) → think Dementia with Lewy Bodies)
- Note: If Parkinsonian motor symptoms precede dementia by more than 1 year → think Parkinson’s Disease Dementia (PDD)
- VS Other causes of dementia;
→ Dementia +Ataxia + Urinary incontinence → think normal pressure hydrocephalus
○ Diagnose with imaging and lumbar puncture.
○ Treat with lumbar puncture. - Note: Dementia patients usually try to prove they don’t forget things. If patient is trying cover up or compensate for memory lapses this can be an early clinical clue
35. A 65-year-old woman with Parkinson’s disease started on levodopa and carbidopa. After several weeks, she reports improvement in mobility and a reduction in nausea and lightheadedness. What is the most likely mechanism by which carbidopa enhances therapy?
➔ Inhibits peripheral conversion of levodopa to dopamine (This reduces peripheral side effects (nausea and vomiting) and increases CNS availability of levodopa)
- Note: Carbidopa inhibits peripheral DOPA decarboxylase → reducing dopamine formation outside the CNS.
- This limits nausea, vomiting, and hypotension.
- Does not cross the BBB, so it has no central effect.
36. 70-year-old man with Parkinson’s disease develops compulsive gambling and hypersexuality after starting a new medication. Which drug is the most likely cause?
➔ Pramipexole (a Dopamine agonists which is associated with impulse control disorders)
- Note: Other Parkinson’s medications:
- Amantadine: ↑ Dopamine release, ↓ reuptake.
- Adverse effects : Livedo reticularis.
- Entacapone/Tolcapone: COMT inhibitors. Tolcapone crosses BBB.
- Selegiline/Rasagiline: MAO-B inhibitors (inhibit dopamine breakdown).
- Benztropine/Trihexyphenidyl: Antimuscarinic (improves tremor/rigidity)
37. A 72-year-old man has become combative and confused since this morning. His wife notes mild memory issues over the past year. What best explains his behavior?
➔ Delirium (The acute onset of confusion and combativeness (since this morning) strongly suggests delirium.)
- Note: Delirium is an acute reversible confusional state marked by fluctuating levels of consciousness, inattention, and impaired cognition.
- Commonly, in older adults with infection, medications, electrolyte imbalances, or hospitalization
- In Delirium patients → look for new drugs or diseases → If the question didn’t mention anything → we do thorough lab workup (especially Urine Analysis to look for UTI, a common cause of delirium elderly)
Peripheral Nerve and Neuromuscular Disorders
38. A 60-year-old woman with fatigue and drooping eyelids that worsen in the evening. Normal sensation and reflexes. Chest CT shows anterior mediastinal mass. Most likely mechanism?
➔ Antibodies against acetylcholine receptors (Eye muscle weakness that worsens in the evening → think Myasthenia gravis → Occurs due to autoantibodies against postsynaptic acetylcholine receptors.)
- Note: Myasthenia gravis is associated with Thymus hyperplasia and Thymoma.
- Patient diagnosed with MG → next step is to do → Chest CT Scan to look for Thymoma
- Symptoms worsen with repetition and get better with an ice pack.
- Reflexes are normal.
- Treated with Cholinesterase inhibitors (pyridostigmine)
39. An old man presents with progressive weakness. Absent knee reflexes and symptoms improve after repeated exercise. What lung pathology is associated with this condition?
➔ Small cell lung cancer (symptoms suggestive of Lambert-Eaton Myasthenic Syndrome– a paraneoplastic syndrome commonly associated with small cell lung cancer)
- Note: Lambert-Eaton myasthenic syndrome
- Caused by → autoantibodies against presynaptic voltage-gated calcium channels→ leads to ↓ Ach;
→ Causes Proximal muscle weakness,
→ Absent reflexes
→ Associated with autonomic symptoms (dry mouth, constipation, impotence)
→ Symptoms improve with repeated exercise.
40. A 35-year-old man, progressive weakness that started in his feet and moved upward. Reflexes are absent at the knees. What is the most likely underlying pathology?
➔ Endoneurial inflammatory infiltration (Symptoms suggestive of Guillain-Barré Syndrome (GBS), which is driven by an autoimmune response causing → endoneurial inflammatory infiltration)
- Note: A bloody diarrhea → followed by Neuropathy → think Guillain-Barré syndrome
- Pathophysiology;
→ Infection (Campylobacter jejuni, viral illnesses) → Trigger immune activation
→ Then Autoantibodies target peripheral nerves → causing Endoneurial inflammatory infiltration → leading to Demyelination of peripheral nerves
→ Leading to Symmetrical ascending weakness, areflexia and possible autonomic dysfunction - Facial paralysis and Respiratory failure are a common complications
41. A 22-year-old man with several months of weakness and trouble releasing his grip. Muscle biopsy shows atrophy of type 1 fibers. What is the most likely diagnosis?
➔ Muscular dystrophy (Myotonic dystrophy) (trouble releasing his grip is a Buzzword for Myotonic dystrophy)
- Note: It affects skeletal muscle chloride channels leading to → delayed relaxation
- Other symptoms include frontal balding, cataracts, testicular atrophy, arrhythmias
- Myotonic dystrophy: is caused by CTG trinucleotide repeat expansion
42. An old woman with poorly controlled diabetes has numbness and tingling in her feet. What is the underlying cause of her neuropathy?
➔ Endoneurial arteriolar hyalinization (Symptoms suggestive of Diabetic neuropathy which is caused by Endoneurial arteriolar hyalinization)
- Note: Pathophysiology: chronic hyperglycemia leads to → vascular glycation and hyalinization of endoneurial arterioles leading to → nerve ischemia → causing :
- Peripheral polyneuropathy (stocking-glove paresthesia)
- Autonomic neuropathy (gastroparesis, erectile dysfunction, and neurogenic bladder)
- Motor neuropathy (distal limb weakness)
CNS Tumors
43. A 13-year-old boy with worsening headaches and vision problems over the past year. Brain imaging reveals a suprasellar calcified cystic mass. What embryological structure is this mass most likely derived from?
➔ Rathke’s pouch (anterior pituitary) (symptoms suggestive of Craniopharyngioma)
- Note: Craniopharyngioma: from remnants of Rathke’s pouch (an ectodermal structure that gives rise to the anterior pituitary)-
– Arises in children, as suprasellar masses, with cystic components, and calcifications. - VS pituitary adenoma: Usually occurs in adults, solid (not calcified), and presents with hormonal symptoms.
44. A 47-year-old woman with new-onset seizures. Imaging shows brain imaging reveals a well-circumscribed, extra-axial mass attached to the dura and biopsy reveals whorled cell clusters and calcified concentric structures. What is the most likely diagnosis?
➔ Meningioma (extra-axial tumor + whorled cell clusters on biopsy → think meningioma)
- Note: Meningioma arises from arachnoid cap cells.
- Histology: whorled cell patterns and psammoma bodies (calcified concentric structures).
- Can cause seizures or headaches due to compression of adjacent brain structures.
45. A 62-year-old man with a seizure. Brain CT scan reveals a mass in the right cerebral hemisphere that crosses the midline. What is the most likely diagnosis?
➔ Glioblastoma multiforme (A mass crossing the midline (butterfly glioma) is a Buzzword for Glioblastoma multiforme)
- Note: It is the most common adult brain tumor
- GFAP + as it comes from glial origin.
- Histology: pseudopalisading necrosis with areas of hemorrhage and necrosis
46. An 11-month-old boy, irritable and hypotonic. Exam shows chaotic eye movements, myoclonic jerks and a firm abdominal mass. Urine shows elevated catecholamine metabolites. The most likely diagnosis?
➔ Neuroblastoma (infant <2 years + an abdominal mass + opsoclonus-myoclonus + elevated HVA/VMA → think Neuroblastoma)
- Note: Chaotic eye movements + myoclonic jerks → indecates opsoclonus-myoclonus
- Neuroblastoma: is a neural crest-derived tumor in adrenal medulla or along the sympathetic chain.
- If a Kid presents with an abdominal mass:
If it crosses midline → think of Neuroblastoma
If it doesn’t cross midline → think of Wilm’s Tumor
47. A 16-year-old boy with morning headaches and blurry vision. MRI reveals an intraventricular mass and hydrocephalus. What is the cell of origin for this tumor?
➔ Ependymal cells (symptoms suggestive of Ependymoma which arises from ependymal cells)
- Note: Ependymal cells line the ventricular system and central canal of the spinal cord → a tumor there can obstruct CSF causing → obstructive hydrocephalus
- Can spread via cerebrospinal fluid →causing potential for drop metastases in the spinal cord.
48. A 36-year-old woman with sensorineural hearing loss, facial numbness, and an asymmetric smile. Where is the most likely location of the lesion?
➔ Between the cerebellum and lateral pons (Cerebellopontine angle) (symptoms suggestive of Vestibular schwannoma → which arises at the cerebellopontine angle)
- Note: Vestibular schwannoma: arises at the cerebellopontine angle, leading to compression of:
→ Cranial nerve VIII → leading to hearing loss
→ Cranial nerve V → leading to facial numbness,
→ Cranial nerve VII → leading to facial weakness.
If bilateral vestibular schwannoma → think Neurofibromatosis II
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Seizures & Epilepsy
49. A 6-year-old boy with poor attention and staring spells during the day. He blanks out during TV shows and doesn’t respond to his name. Each episode lasts a few seconds, and he returns to normal immediately. What is the most appropriate treatment?
➔ Ethosuximide (Child with brief staring spells + preserved tone + no postictal confusion → think absence seizure → treated with Ethosuximide)
- Note: Confirmed by 3-Hz spike-and-wave discharges on EEG.
- Ethosuximide (blocks T-type calcium channels).
50. A 4-year-old boy develops a generalized tonic-clonic seizure during a viral illness. Seizure lasts for 3 minutes and he has no neurologic deficits. Most appropriate next step?
➔ Reassurance (children aged 6 months to 5 years + high fever + seizure → think febrile seizure → the first step is reassurance if it is simple)
- Note: Simple febrile seizure:
→ Lasts < 15 minutes
→ Occurs only once in 24 hrs
→ No focal neurologic deficit.
51. A 10-year-old boy is brought to the emergency department while having a generalized tonic-clonic attack. First line of treatment?
➔ Benzodiazepine. (symptoms suggestive of status epilepticus → treated with Benzodiazepine)
- Note: Presenting to the ER with seizure likely meets the definition of status epilepticus (≥5 minutes of continuous seizure activity or repeated seizures without recovery) → treat with abortive therapy → Benzodiazepine
Headaches, Facial Pain & Cranial Neuralgias
52. A 30-year-old man with episodes of severe, sharp headaches behind her left eye, lasting about 30 minutes and associated with left-sided ptosis and nasal congestion.What is the diagnosis?
➔ Cluster headache
- Note: Male smoker + excruciating unilateral headache + ipsilateral autonomic symptoms (ptosis, conjunctival injection, nasal congestion, and lacrimation) → think Cluster headache
- Episodes are brief (15–180 minutes) but recur in clusters.
- Treatment: 100% Oxygen
53. A 30-year-old woman with daily dull headaches. The pain is bilateral, band-like, and she can continue working despite discomfort. What is the most likely diagnosis?
➔ Tension headache (dull, bilateral pain often precipitated by stress and fatigue + not associated with nausea, vomiting → think tension headache)
- Note: Treat with simple analgesics.
54. A 30-year-old woman with a sudden onset “hole” in her right eye visual field, followed by a severe, throbbing headache. Symptoms resolve spontaneously over 5 hours. What is the most likely diagnosis?
➔ Migraine with aura (unilateral, pulsatile headache +/- transient focal neurologic symptoms (aura) → think migraine headache)
- Note: Migraine treatment:
- Abortive medications: triptans, NSAIDs, antiemetics (e.g., metoclopramide), and ergotamine.
- Preventive medications: anticonvulsants (topiramate, valproate), beta blockers, and antidepressants (TCAs like amitriptyline, or venlafaxine).
VS Red flags for headache: - First or worst headache ever → think subarachnoid hemorrhage
- New headache >50 years old → think Giant Cell Arteritis
- Papilledema, altered mental status → ↑ Intracranial pressure
55. A 30-year-old woman with electric shock-like pain on the right side of her face triggered by chewing and brushing her teeth. Each episode lasts a few seconds. Best initial treatment?
➔ Carbamazepine (brief, intense facial pain triggered by minor stimuli → think Trigeminal neuralgia → treat with carbamazepine, a sodium channel blocker)
- Note: If Bilateral trigeminal neuralgia → think of multiple sclerosis.
- Carbamazepine complications include: bone marrow suppression, SIADH
56. A 34-year-old man has difficulty tolerating normal sounds in his right ear. The right side of face feels heavier, and there is asymmetry of her face when she smiles or raises her eyebrow. Which cranial nerve is involved?
➔ Facial nerve (CN VII)
- Note: Facial Nerve Palsy:
- It is caused by dysfunction of the facial nerve (CN VII) after it exits the brainstem.
- Affects entire ipsilateral face (forehead + lower face).
- Causes dry eyes, hyperacusis (stapedius paralysis), loss of taste in the anterior 2/3 tongue
Etiology: - Idiopathic → think Bell’s palsy
- Facial palsy + herpetic lesion on ear → think HSV reactivation
- Facial palsy + target lesion on skin → think Lyme disease
- Facial palsy + Painful Rash in or around the ear + Tinnitus + vertigo → think Ramsy Hunt syndrome (caused by varicella zoster)
- Facial palsy + parotid lesion + lunge symptoms → think sarcoidosis
- VS If forehead spared → think central nervous system lesion (next step is to send for an MRI)
57. A 55-year-old man complains of double vision, particularly when walking down stairs or reading. Which cranial nerve is most likely affected?
➔ Trochlear nerve (CN IV) (It affects the superior oblique muscle leading to → vertical diplopia, especially when looking down and inward)
- Note: Patients may tilt their heads to compensate.
58. A 58-year-old man with poorly controlled diabetes has sudden-onset double vision. He has right-sided ptosis, and the right eye rests in a “down and out” position. Pupils are equal and reactive to light. Most likely the cause of his symptoms?
➔ CN III ischemia (As CN III Palsy → causes the Eye to rest in a down and out position + Ptosis)
- Note: Pupil size can identify the type of the lesion:
– If pupil is normal → it is caused by CN III ischemia (usually due to diabetic mononeuropathy
– If pupil is dilated and non-reactive → it is caused by CN III compression (usually due to aneurysm)
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CNS Infections
59. A 23-year-old man with fever, confusion, and seizures. CSF analysis reveals normal glucose, elevated protein, and increased lymphocytes and erythrocytes. What is the most likely diagnosis?
➔ Herpes simplex virus (HSV) encephalitis
Cerebrospinal fluid analysis results:
| Condition | WBC Type | Glucose | Protein |
|---|---|---|---|
| Bacterial Meningitis | ↑↑ Neutrophils | ↓ | ↑ |
| Viral Meningitis | ↑ Lymphocytes | Normal | Normal / ↑ |
| Fungal/TB Meningitis | ↑ Lymphocytes | ↓ | ↑ |
| Herpes Encephalitis | ↑ Lymphocytes + RBCs | Normal | ↑ |
| Guillain-Barré Syndrome | Normal cells | Normal | ↑ (albuminocytologic dissociation) |
- In Herpes encephalitis MRI shows temporal lobe edema.
60. A 45-year-old man with fever, headache, photophobia, and neck stiffness. Lumbar puncture shows high opening pressure, elevated neutrophils, low glucose, and high protein. What organism is most likely responsible for his condition?
➔ Streptococcus pneumoniae (Neck stiffness + CSF analysis findings → suggest bacterial meningitis→ Strep. Pneumoniae is the most common cause in adults)
61. A 19-year-old college student presents with fever, headache, photophobia, and a petechial rash. He lives in a dormitory. Which organism is the most likely cause of his symptoms?
➔ Neisseria meningitidis (Common cause of meningitis in young adults, especially in close-contact settings like dorms or military barracks)
62. A 74-year-old man undergoing chemotherapy presents with fever, neck stiffness, and altered mental status. His wife reports he recently consumed soft cheese at a family gathering. Which organism is the most likely cause of his condition?
➔ Listeria monocytogenes (Common cause of meningitis in elderly or immunocompromised patients, often linked to unpasteurized dairy)
- Note: Other Causes of meningitis :
- Recent sinus or ear infection + brain abscess → think strep viridans, anaerobes (e.g., Bacteroides)
- HIV/immunosuppressed + ring-enhancing brain lesions → think Toxoplasma gondii
- Neonate (<1 mo) → think Group B Strep, E. coli, Listeria monocytogenes
Spinal Cord lesions
63. A 44-year-old man with progressive gait instability, positive Romberg sign, and absent deep tendon reflexes in both legs. What is the most likely diagnosis?
➔ Tabes dorsalis (symptoms suggestive of demyelination of the dorsal columns and dorsal roots → think Tabes dorsalis)
- Note: It causes damage to:
→ The dorsal columns → causing sensory ataxia and positive Romberg sign
→ Dorsal roots → causing absent reflexes - Tabes dorsalis: is a late manifestation of neurosyphilis caused by Treponema pallidum
- Diagnosis with reactive VDRL in CSF.
- Treatment with IV penicillin G.
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64. A 65-year-old woman with recurrent falls. The Romberg test is positive. Hb = 8.2, MCV = 112. What is the most likely cause of neurologic findings?
➔ Subacute combined degeneration (Loss of proprioception + megaloblastic anemia → think Vitamin B12 deficiency → causes subacute combined degeneration)
- Note: Subacute combined degeneration (Vitamin B12 deficiency) affects both
→ Dorsal columns → causing sensory ataxia)
→ Lateral corticospinal tracts → causing spastic paresis, +ve Babinski sign.
Presents with gait instability, numbness, and weakness. - Risk factors for Vit B12 def : Strict vegan (> 3 years), 2-3 years after gastrectomy or ileal resection, or pernicious anemia.
- If a patient has megaloblastic anemia → Think of vit B9 or vit B12 deficiency → if ↑ methylmalonic acid or neurologic symptoms are present → think B12 deficiency.
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65. A 20-year-old woman with multiple hand burns without feeling pain. She has loss of pain and temperature sensation in her upper limbs, along with hand muscle atrophy and weakness. The most likely diagnosis?
➔ Syringomyelia
- Note: Syringomyelia: central spinal cord cavitation, often at C8-T1 leads to damaging:-
– The ventral white commissure (→ causing bilateral loss of pain and temperature)
– Anterior horns (→ causing lower motor neuron signs).
– Expansion can affect lateral corticospinal tracts ( causing → spasticity) and posterior columns (→ causing proprioceptive loss). - Common presentation: is recurrent hand burns without feeling pain.
- Syringomyelia is associated with Chiari I malformation.
66. A 60-year-old man with progressive muscle weakness and gait abnormalities. He has 3+ knee reflex on the left side and atrophy of the right upper limb. The most likely diagnosis?
➔ Amyotrophic lateral sclerosis (symptoms of Hyperreflexia + atrophy + absence of sensory symptoms → indicate a lesion affecting both UMN and LMN → think ALS)
- Note: ALS: involves both corticospinal tracts (upper motor neuron: Hyperreflexia, spasticity) and anterior horn (lower motor neurons: atrophy and fasciculations.)
– No sensory deficits →it is a key distinguishing feature
– May have dysarthria, dysphagia, and respiratory failure in later stages
Movement Disorders, Sleep & Metabolic Syndromes
67. A young man reports falling asleep during conversations and while reading. He sometimes hears a voice before falling asleep and has brief episodes of muscle weakness triggered by laughter. The most likely diagnosis?
➔ Narcolepsy
- Note: Excessive daytime sleepiness + cataplexy (sudden muscle weakness triggered by emotion) +hallucinations during sleep-wake transitions → think Narcolepsy
- It is caused by loss of hypocretin-producing neurons.
- Shortened REM latency on sleep studies + low hypocretin → is diagnostic of Narcolepsy.
68. A 52-year-old woman with unpleasant sensations in her legs at night and is relieved by walking. What is the treatment?
➔ Iron, Gabapentin (Evening urge to move legs that is worsened by inactivity → think Restless leg syndrome)
- Note: Restless Legs Syndrome is Associated with iron deficiency, CKD, and diabetes.
- Treatment includes Iron, Gabapentin, dopamine agonists.
69. A 22-year-old man with tremor, gait instability, and dysarthria. Labs show elevated liver enzymes. What is the Next step?
➔ Slit lamp examination (neuropsychiatric symptoms + elevated liver enzyme → think Wilson disease → do slit lamp examination to reveal Kayser-Fleischer rings)
- Note: Wilson disease: is caused by ATP7B mutations →leading to copper accumulation in the basal ganglia, liver, and cornea.
- Confirmed by : low ceruloplasmin and increased urinary copper.
70. A 29-year-old woman with a coarse hand tremor that worsens as she reaches for objects. No tremor is seen at rest. Which brain structure is involved?
➔ Cerebellum (worsening as a patient reaches for objects → indicated intention tremor → seen in Cerebellar dysfunction)
- Note: Tremor types;
- Intention tremor
○ Zigzag pointing. Increase when reaching target. Abnormal finger-to-nose.
○ Seen in Cerebellar dysfunction - Essential tremor
○ Often familial
○ Postural tremor that Worsens with movement (e.g., holding objects) and improves with alcohol
○ Treatment: propranolol, primidone - Resting tremor
○ Pill-rolling. Occurs at rest.
○ Seen in Parkinson’s disease
ENT
71. An old diabetic man with severe right ear pain and purulent discharge. Manipulation of the ear causes severe pain. What is the most likely diagnosis?
➔ Malignant otitis externa (elderly diabetics + severe pain + purulent discharge + tenderness being the ear (indicating spread of infection) → think Malignant otitis externa
- Note: Otitis Externa:
→ Inflammation of external auditory canal, often caused by Pseudomonas (swimmer’s ear).
→ Presents with otalgia worsened by manipulation, discharge, and pruritus. - Malignant otitis externa:
→ A severe form of otitis externa that progresses to osteomyelitis of the skull base.
→ Commonly occurs in elderly diabetic patients.
→ May lead to cranial nerve involvement if untreated.
72. A 2-year-old boy has a fever and tugging at his right ear. Otoscopy shows a red, bulging tympanic membrane. What is the most likely diagnosis?
➔ Acute otitis media (Fever + otalgia + erythematous tympanic membrane → think Acute otitis media)
- Note: Common causes: S. pneumoniae, H. influenzae, M. catarrhalis.
- The erythematous tympanic membrane → may rupture.
- A common Complication is Mastoiditis →which is postauricular tenderness/swelling can lead to → brain abscess.
73. A man with difficulty hearing. Lateralization to the right ear on Weber test, and air conduction > bone conduction bilaterally on Rinne test. What is the most likely cause?
➔ Left ear sensorineural hearing loss
- Note: Weber and Rinne are used to differentiate types of hearing loss;
| Test | Normal | Conductive HL | Sensorineural HL |
|---|---|---|---|
| Weber | No localization | Localizes to affected ear | Localizes to unaffected ear |
| Rinne | AC > BC | BC > AC | AC > BC |
Common causes of sensorineural hearing loss:
- Noise-Induced Hearing Loss
→ Occurs as a result of Damage to stereo ciliated cells in the organ of Corti
→ High frequency hearing is affected first
- Presbycusis
→ Is Age-related, bilateral sensorineural hearing loss (especially high frequencies); occurs due to cochlear base hair cell loss.
74. A 43-year-old woman has episodes of dizziness lasting <1 minute when turning her head. No hearing loss or tinnitus. What is the most likely diagnosis?
➔ Benign paroxysmal positional vertigo (BPPV) (It is characterized by brief episodes of vertigo triggered by head movements, without associated hearing loss or tinnitus.)
- Note: Nystagmus in BPPV: Brief, mixed horizontal and torsional (rotary) nystagmus that is provoked by positional changes, lasts <1 minute, and is suppressed with visual fixation
- BPPV is caused by dislodged calcium carbonate crystals (canaliths) in the semicircular canals
VS other causes of peripheral vertigo; - Vestibular neuritis: presents as Persistent dizziness lasting days to weeks, often following an upper respiratory infection (URI).
- VS Ménière disease (Endolymphatic Hydrops): presents with Recurrent episodes of vertigo lasting minutes to hours,+ hearing loss + tinnitus
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Ophthalmology & Visual Pathway Disorders
75. A 7-year-old boy with bilateral eye redness and intense itching. He has a history of seasonal allergies. What is the most likely diagnosis?
➔ Allergic conjunctivitis (bilateral eye itching + redness → think allergic conjunctivitis)
- Note: Conjunctivitis types;
- Allergic: Itchy, bilateral discharge.
- Bacterial: Purulent discharge, treated with antibiotics.
- Viral (adenovirus): Most common. Watery discharge, swollen preauricular node, self-limited.
76. A 64-year-old woman with sudden-onset severe eye pain, blurry vision, and seeing halos around lights after moving to a dark room . Her right eye is red with a mid-dilated non-reactive pupil. The most likely diagnosis?
➔ Acute angle-closure glaucoma
- Note: Eye pain after + moving into a dark room or using naphazoline for seasonal allergy → think Acute Angle-closure Glaucoma
- Acute Angle-closure Glaucoma is a true emergency →treat with laser peripheral iridotomy
Additional treatment: - By ↓ Aqueous humor production with beta blockers, alpha agonists, acetazolamide.
- By ↑ Outflow by M3 agonists (pilocarpine), prostaglandin analogs (latanoprost).
77. A 72-year-old man with gradual loss of central vision in both eyes. Fundoscopy shows drusen deposits under the retina. What is the most likely diagnosis?
➔ Dry age-related macular degeneration (gradual central vision loss +drusen deposits on fundoscopy → think dry AMD.)
- Note: Other fundoscopy findings:
- Age-related Macular Degeneration (AMD):
○ Dry: Gradual vision loss, drusen.
○ Wet: Rapid vision loss, choroidal neovascularization. - Diabetic Retinopathy:
○ Nonproliferative: Microaneurysms, hemorrhages, hard exudates.
○ Proliferative: Neovascularization, vitreous hemorrhage.
78. A 68-year-old man with a history of poorly controlled hypertension presents for routine eye examination. Fundoscopy reveals flame-shaped hemorrhages, arteriovenous nicking, and cotton-wool spots. What is the most likely diagnosis?
➔ Hypertensive Retinopathy (Flame hemorrhages + AV nicking + cotton-wool spots → think Hypertensive Retinopathy)
- Note: Other fundoscopy findings:
- Retinal Artery Occlusion: Painless vision loss, “cherry-red spot.”
- Retinal Vein Occlusion: Retinal hemorrhage, edema (“blood and thunder”).
79. A 3-year-old child with a white pupillary reflex on left eye. What is the most likely underlying cause?
➔ Retinoblastoma due to RB1 mutation (unilateral white reflex → think Retinoblastoma)
- Note: White reflex can be due to:
→ Cataract (usually bilateral)
→ Retinoblastoma (usually unilateral, Bilateral in familial form)
Retinoblastoma - Most common intraocular tumor in children.
- Caused by RB1 gene mutation (chromosome 13).
- Presents with leukocoria (white reflex), and strabismus.
- Patients have increased risk of osteosarcoma.
80. A 22-year-old man with facial trauma. On exams, he has difficulty looking up with the affected eye. What is the most likely explanation?
➔ Inferior rectus entrapment from orbital fracture (Orbital floor (blowout) fractures + impaired upward gaze →indicates inferior rectus entrapment.)
- Note: It can be associated with inferior orbital nerve injury → causing hypoesthesia of the cheek.
81. A 55-year-old woman presents with bilateral galactorrhea and progressive difficulty seeing objects on the sides of her visual field. Visual field testing reveals bitemporal hemianopia. What is the most likely location of the lesion?
➔ Optic chiasm (Compression of the optic chiasm disrupts crossing nasal fibers → loss of lateral visual fields in both eyes → Bitemporal hemianopia)
- Note: Optic chiasm most commonly occurs due to pituitary adenoma (e.g., prolactinoma).
Visual Field Defects by Lesion Location
| Lesion Location | Visual Field Defect | Key Features |
|---|---|---|
| Optic nerve / macula | Monocular vision loss | Affects one eye only |
| Optic chiasm | Bitemporal hemianopia | Loss of lateral fields in both eyes |
| Meyer loop (temporal lobe) | Contralateral upper quadrantanopia | ‘Pies in the sky’ |
| Dorsal optic radiation (parietal lobe) | Contralateral lower quadrantanopia | ‘Pie on the floor’ |
| Occipital cortex (PCA infarct) | Contralateral homonymous hemianopia with macular sparing | Macula spared due to dual blood supply (MCA & PCA) |
82. A 29-year-old woman presents with double vision. On leftward gaze, her left eye abducts with nystagmus, but her right eye fails to adduct. Where is the lesion?
➔ Right medial longitudinal fasciculus (Disruption of the MLF impairs coordination between CN VI and CN III nuclei)
- Note: The MLF connects:
- CN VI nucleus (abducens) in the pons (controls lateral rectus for abduction)
- CN III nucleus (oculomotor) in the midbrain (controls medial rectus for adduction)
- Internuclear ophthalmoplegia (INO) is caused by a lesion in the MLF
→ On attempted lateral gaze:
○ Ipsilateral eye fails to adduct.
○ Contralateral eye abducts with nystagmus. - Common causes:
○ Stroke → typically unilateral INO.
○ Multiple sclerosis → often bilateral INO in young women.
🏁 Final Thoughts
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Disclaimer
Version 1.0 May 2025. No part of this document may be reproduced or distributed without written permission. For personal study only. Medical information herein is for educational purposes and does not constitute clinical advice. Always confirm with current guidelines and your institution’s policies.
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