Neuroscience Test 1 — Questions and Answers

Question 1: A 43-year-old man sustains a wound to the lateral neck. This results in weakness of elevation and retraction of the shoulder on the ipsilateral side and difficulty turning the head up and toward the contralateral side. No sensory changes are present. Which of the following nerves most likely has been injured?

Axillary
Lateral cord of the brachial plexus
Phrenic
Spinal accessory (Correct answer)
Suprascapular

Correct answer: Spinal accessory

The spinal accessory nerve (cranial nerve XI) is a pure motor nerve that innervates the sternocleidomastoid and trapezius muscles. Injury to this nerve would cause weakness in elevating and retracting the ipsilateral shoulder (trapezius) and difficulty turning the head up and toward the contralateral side (sternocleidomastoid). The absence of sensory changes is consistent with a pure motor nerve injury. The other nerves listed have different motor or sensory distributions.

Question 2: An investigator is studying normal sleep patterns in healthy men and women. Saccadic motions of the eyes are seen approximately 90 minutes after the volunteers fall asleep. Which of the following is most likely to be observed in the volunteers during this period of saccadic eye movements?

Difficulty awakening
An EEG pattern resembling that of the walking state (Correct answer)
Hyperactive muscle tone
Increased movements
Irregular respiratory rhythm

Correct answer: An EEG pattern resembling that of the walking state

Saccadic eye movements approximately 90 minutes after falling asleep are characteristic of Rapid Eye Movement (REM) sleep. During REM sleep, the brain is highly active, and the electroencephalogram (EEG) pattern strikingly resembles that of an awake person, characterized by low-amplitude, mixed-frequency waves. Despite this brain activity, there is a paradoxical muscle atonia (paralysis), making it difficult to awaken. Respiration can also be irregular during this stage.

Question 3: Drug X applied to a nerve axon decreases the duration of the action potential without affecting the resting potential or peak amplitude of the action potential. Which of the following is the most likely mechanism of action of Drug X?

Block of voltage-dependent Na + permeability
Decrease in the rate of Na + inactivation
Decrease in voltage-dependent Na + permeability
Increase in the rate of voltage-dependent changes in K + permeability (Correct answer)
Inhibition of the Na + –K + pump

Correct answer: Increase in the rate of voltage-dependent changes in K + permeability

The action potential's duration is primarily determined by the repolarization phase, which is mediated by the efflux of potassium ions through voltage-gated K+ channels. An increase in the rate of voltage-dependent changes in K+ permeability means these channels open faster or more extensively, accelerating K+ efflux and thus shortening the repolarization time and the overall action potential duration. Options affecting Na+ permeability (A, B, C) would alter depolarization or peak amplitude, which are stated to be unaffected, while inhibition of the Na+-K+ pump (E) affects resting potential maintenance, not action potential duration.

Question 4: A 65-year-old man has loss of pain and temperature sensation on the right side of the face and from the neck down on the left. Examination shows partial paralysis of the soft palate, larynx, and pharynx, and ataxia, all on the right. The most likely cause of these findings is thrombosis to which of the following arteries?

Basilar
Right posterior inferior cerebellar (Correct answer)
Left posterior inferior cerebellar
Right superior cerebellar
Left superior cerebellar

Correct answer: Right posterior inferior cerebellar

The patient's symptoms—ipsilateral facial pain/temperature loss, contralateral body pain/temperature loss, ipsilateral ataxia, and ipsilateral cranial nerve deficits (soft palate, larynx, pharynx paralysis)—are classic for Lateral Medullary Syndrome (Wallenberg Syndrome). This syndrome results from ischemia of the lateral medulla, which is supplied by the posterior inferior cerebellar artery (PICA). Since the ipsilateral deficits are on the right side, the lesion must be in the right lateral medulla, indicating thrombosis of the right PICA. Other arteries would cause different patterns of neurological deficits.

Question 5: A 45-year-old man has a progressively severe headache. Funduscopic examination discloses blurred margins and bulging of the optic discs. The retinal veins are engorged and show no pulsatile flow. Which of the following is the mechanism most likely to explain these findings?

Acute occlusion of the retinal artery
Demyelination of the optic nerve
Increased intracranial pressure (Correct answer)
Inflammation of the anterior chamber
Inflammation of the optic nerve

Correct answer: Increased intracranial pressure

Blurred margins and bulging of the optic discs (papilledema), along with engorged retinal veins and absent venous pulsations, are hallmark signs of increased intracranial pressure (ICP). Elevated ICP compresses the optic nerve sheath, impeding axoplasmic flow and venous return from the retina, leading to swelling of the optic disc. Other options like retinal artery occlusion or optic nerve inflammation would present with different funduscopic findings and clinical courses.

Question 6: A 4-month-old boy is brought to the physician by his mother for a well-child examination. He is at the 98th percentile for head circumference. Physical examination shows dilation of the scalp veins and spasticity of the lower extremities. The physician suspects excessive cerebrospinal fluid accumulation in the ventricular system of the brain. The source of this fluid is most likely which of the following?

Choroid plexus (Correct answer)
Dura mater
Pia mater
Roof of the third ventricle

Correct answer: Choroid plexus

The choroid plexus, located within the brain's ventricles, is the primary site for the production of cerebrospinal fluid (CSF). The symptoms of increased head circumference, dilated scalp veins, and spasticity in an infant suggest hydrocephalus, which is an excessive accumulation of CSF. Therefore, the source of this fluid is the choroid plexus. The dura mater, pia mater, and the roof of the third ventricle are not responsible for CSF production.

Question 7: A 68-year-old woman is brought to the physician by her husband because of strange behavior. The previous evening, she had gotten up suddenly from the dinner table and started to undress in front of guests. Further questioning discloses a 1-year history of a progressive change in behavior. She writes everything down on a notepad; otherwise, she forgets. She cannot remember the names of her four grandchildren or the date of her wedding anniversary. These symptoms are most likely associated with a deficit in which of the following?

Acetylcholine (Correct answer)
Dopamine
Glucose 6-phosphate dehydrogenase
Insulin
Serotonin

Correct answer: Acetylcholine

The patient's progressive memory loss, behavioral changes (e.g., undressing inappropriately), and difficulty with recall are characteristic symptoms of Alzheimer's disease. This neurodegenerative condition is primarily associated with a significant deficit in acetylcholine, due to the degeneration of cholinergic neurons in the nucleus basalis of Meynert. While other neurotransmitters can be affected, acetylcholine is the most prominent deficit linked to the cognitive decline in Alzheimer's. Dopamine, insulin, and serotonin deficits are associated with different neurological or metabolic conditions.

Question 8: A 50-year-old man has had gradually progressive hand weakness. He has atrophy of the forearm muscles, fasciculations of the muscles of the chest and arms, hyperreflexia of the lower extremities, and extensor plantar reflexes. Sensation is not impaired. Which of the following is the most likely diagnosis?

Amyotrophic lateral sclerosis (Correct answer)
Dementia, Alzheimer type
Guillain-Barré syndrome
Multiple cerebral infarcts
Multiple sclerosis

Correct answer: Amyotrophic lateral sclerosis

The combination of gradually progressive hand weakness, forearm muscle atrophy, and fasciculations (lower motor neuron signs) with hyperreflexia and extensor plantar reflexes (upper motor neuron signs), all without sensory impairment, is pathognomonic for Amyotrophic Lateral Sclerosis (ALS). ALS is a neurodegenerative disease that selectively affects both upper and lower motor neurons. Other conditions listed do not present with this specific combination of UMN and LMN signs without sensory involvement.

Question 9: An 8-year-old boy is brought to the physician by his mother because he is not paying attention in class. His mother says that his teacher has described his in-school behavior as “frequently stopping what he is doing and then blinking and making chewing movements.” His mother has noticed that he sometimes “stares off into space” and seems to be daydreaming. Physical examination shows no abnormalities. An EEG during one of the episodes shows generalized spike-and-wave bursts at 3 Hz per second. This patient most likely has which of the following types of seizures?

Absence (Correct answer)
Akinetic
Complex partial
Generalized tonic-clonic
Myoclonic

Correct answer: Absence

The description of brief episodes of 'staring off into space,' 'blinking and chewing movements,' and 'stopping what he is doing' without post-ictal confusion, especially in a child, is classic for absence seizures (petit mal). The characteristic 3 Hz generalized spike-and-wave pattern on EEG confirms this diagnosis. Other seizure types, such as generalized tonic-clonic or complex partial seizures, involve different clinical presentations and EEG findings.

Question 10: A previously healthy 18-year-old man is brought to the emergency department because of fever, a poorly localized headache, and a stiff neck for 12 hours. The symptoms were preceded by nasal congestion, muscle aches, and chills 3 days ago. His temperature is 38.7°C (101.6°F). Physical examination shows nuchal rigidity and photophobia. There is no papilledema. Neurologic examination shows no focal findings. Which of the following is the most likely diagnosis?

Acute meningitis (Correct answer)
Classic migraine
Cluster headache
Idiopathic intracranial hypertension
Subarachnoid hemorrhage
Temporal arteritis
Tension-type headache

Correct answer: Acute meningitis

The patient's presentation of fever, headache, nuchal rigidity (stiff neck), and photophobia, preceded by a viral prodrome, is the classic clinical triad for acute meningitis. Nuchal rigidity and photophobia are signs of meningeal irritation. The absence of focal neurological findings or papilledema is consistent with early, uncomplicated meningitis. Other headache types or conditions like subarachnoid hemorrhage would present with different symptom profiles or lack the infectious context.

Question 11: A 36-year-old woman comes to the physician because of a 10-month history of difficulty falling asleep due to a crawling sensation in her legs. She has to get up several times during the night to relieve the feeling. The symptoms started shortly after she delivered her son 1 year ago. She says her husband complains because she has become a “jumpy” sleeper, and her movements sometimes wake him up. Physical examination shows no abnormalities. Which of the following is the most likely diagnosis?

Amyotrophic lateral sclerosis
Multiple sclerosis
REM sleep behavior disorder
Restless legs syndrome (Correct answer)
Sleep myoclonus

Correct answer: Restless legs syndrome

The patient's symptoms—an irresistible urge to move the legs, often with uncomfortable 'crawling' sensations, worse at rest/night, and relieved by movement—are the cardinal features of Restless Legs Syndrome (RLS). The onset during pregnancy/postpartum is common, and the 'jumpy' sleep likely refers to periodic limb movements in sleep (PLMS), which frequently co-occur with RLS. Other conditions like ALS or MS do not present with this specific constellation of sensory discomfort and urge to move.

Question 12: A 53-year-old woman dies 4 days after an automobile collision. She sustained multiple injuries including a femoral fracture. Widespread petechiae are found in the cerebral white matter at autopsy. Which of the following is the most likely cause of these findings?

Acute respiratory distress syndrome
Contrecoup injury
Fat embolization (Correct answer)
Septicemia
Subdural hematoma

Correct answer: Fat embolization

A femoral fracture, a long bone injury, is a common cause of fat embolism. Fat globules released from the bone marrow can enter the bloodstream and travel to the brain, causing widespread microvascular occlusion and petechial hemorrhages in the cerebral white matter. This is a characteristic finding of cerebral fat embolization, often occurring days after the initial injury. Other options like contrecoup injury or subdural hematoma are direct traumatic brain injuries, while septicemia would have different systemic manifestations.

Question 13: A 23-year-old woman with chronic hepatic disease is brought to the physician because of a 6-month history of progressive behavioral and personality changes, difficulty walking, clumsiness of her arms and legs, and slurred speech. Physical examination shows facial dystonia and dysarthria. There is intention tremor, rigidity, and ataxia of all extremities. Slit-lamp examination shows a brownish ring around the cornea of both eyes. Which of the following abnormalities in plasma is most likely in this patient?

Decreased calcium concentration
Decreased ceruloplasmin concentration (Correct answer)
Decreased transferrin concentration
Increased ammonium concentration
Increased ketones
Increased lactate concentration

Correct answer: Decreased ceruloplasmin concentration

The patient's symptoms, including chronic hepatic disease, progressive neurological dysfunction (dystonia, tremor, ataxia, dysarthria), and Kayser-Fleischer rings (brownish corneal rings), are classic for Wilson's disease. This is an autosomal recessive disorder of copper metabolism characterized by impaired copper excretion and reduced synthesis of ceruloplasmin, the primary copper-carrying protein in plasma. Therefore, a decreased ceruloplasmin concentration is the most likely abnormality.

Question 14: A new drug is developed that prevents the demyelinization occurring in the progress of multiple sclerosis. The drug protects the cells responsible for the synthesis and maintenance of myelin in the central nervous system. These cells are most likely which of the following?

Astrocyte
Ependymal cell
Microglial cell
Oligodendrocyte (Correct answer)
Schwann cell

Correct answer: Oligodendrocyte

Multiple sclerosis is a demyelinating disease of the central nervous system (CNS). Oligodendrocytes are the glial cells specifically responsible for synthesizing and maintaining the myelin sheath around axons within the CNS. Protecting these cells would directly prevent the demyelination seen in MS. Schwann cells, in contrast, produce myelin in the peripheral nervous system.

Question 15: A 47-year-old man with Down syndrome is brought to the physician by his sister because of an 8-month history of regression in his abilities. The sister describes a gradual decline in his language skills and progressive fearfulness. The patient no longer remembers songs that he has known for years, and he does not wish to participate in family activities anymore. Pathologic examination of the brain would most likely show which of the following in this patient?

Deposits of long-chain fatty acids
Intracellular arylsulfatase A
Lewy bodies and nigral atrophy
Neuronal plaques and tangles
Perivenular inflammatory cells (Correct answer)

Correct answer: Perivenular inflammatory cells

While individuals with Down syndrome are highly predisposed to developing Alzheimer's pathology (neuronal plaques and tangles) at an earlier age, the description of an '8-month history of regression' and 'progressive fearfulness' can also point to a distinct 'Down syndrome regression disorder' (DSRD). Some forms of DSRD are associated with inflammatory or autoimmune processes in the brain, which could manifest as perivenular inflammatory cells on pathological examination. This suggests an inflammatory encephalopathy rather than typical slow-onset Alzheimer's progression.

Question 16: A 29-year-old man who emigrated from Scotland 3 years ago is brought to the emergency department because of severe shortness of breath for 2 hours. He has a debilitating condition that began 2 years ago with an odd sticky feeling of his skin, but physical examination at that time showed no abnormalities. His condition has progressed to include severe major depressive disorder, dementia, unsteady gait, difficulty walking, and impaired coordination. He now is confined to a wheelchair and has severe dementia and the inability to speak. There is no family history of a similar condition. On arrival, his respirations are 24/min, and he dies shortly thereafter. At autopsy, examination of the brain shows a spongiform encephalopathy. Which of the following is the most likely diagnosis?

Dementia, Alzheimer type
Frontotemporal dementia
Parkinson disease
Pick disease
Variant Creutzfeldt-Jakob disease (Correct answer)

Correct answer: Variant Creutzfeldt-Jakob disease

The patient's young age, rapid progression of psychiatric symptoms (severe depression), sensory complaints ('sticky feeling'), neurological decline (dementia, ataxia), and spongiform encephalopathy on autopsy are highly characteristic of variant Creutzfeldt-Jakob disease (vCJD). His emigration from Scotland is also relevant, as vCJD is linked to the consumption of beef products contaminated with bovine spongiform encephalopathy (BSE) prions, which was prevalent in the UK.

Question 17: A 52-year-old woman comes to the physician because of gradual loss of feeling in her feet during the past 6 months. She is a portrait painter. She has a 23-year history of hypertension and a 20-year history of type 2 diabetes mellitus. Menopause occurred 1 year ago. She has smoked 2 packs of cigarettes daily for 30 years. She took an oral contraceptive for 20 years. Current medications include hormone replacement therapy, diuretics, and an oral hypoglycemic agent. Her blood pressure is 135/85 mm Hg. Sensation to pinprick is decreased over both feet. Which of the following is the strongest predisposing risk factor of this new finding?

Hypertension
Long-term exposure to paint fumes
Long-term use of exogenous hormones
Long-term use of tobacco
Type 2 diabetes mellitus (Correct answer)

Correct answer: Type 2 diabetes mellitus

The patient's symptoms of gradual loss of feeling in her feet, particularly decreased pinprick sensation in a 'stocking-glove' distribution, are classic for peripheral neuropathy. Her 20-year history of type 2 diabetes mellitus is the strongest predisposing risk factor, as chronic hyperglycemia leads to microvascular damage and nerve dysfunction, making diabetic neuropathy a very common complication.

Question 18: A 49-year-old woman comes to the physician because of a 3-month history of waking at night because of pain and numbness of her right hand. She reports that shaking her hand decreases the severity of the pain. She has been cutting hair at a beauty salon 6 days weekly for 35 years. Examination of the right hand shows tenderness with palpation and distal tingling on percussion of the volar wrist. Prolonged forcible palmar flexion of the right wrist produces tingling. Which of the following is the most likely diagnosis?

Carpal tunnel syndrome (Correct answer)
Early rheumatoid arthritis
Osteoarthritis
Stress fracture
Tendinitis

Correct answer: Carpal tunnel syndrome

The patient's symptoms, including nocturnal hand pain and numbness, relief with shaking the hand, and positive physical examination findings (Tinel's sign on percussion of the volar wrist and Phalen's maneuver with forced palmar flexion), are pathognomonic for carpal tunnel syndrome. This condition is caused by compression of the median nerve as it passes through the carpal tunnel, often exacerbated by repetitive hand movements, as seen in her occupation.

Question 19: A 65-year-old woman has had double vision, difficulty keeping her eyes open, and diffuse weakness for the past several months. She has bilateral ptosis that worsens with sustained upward gaze, limited horizontal and vertical movements in both eyes, and nasal speech. Her symptoms and signs improve transiently following intravenous injection of edrophonium. An abnormality is most likely to be found in which of the following structures?

Anterior horn cell
Motor cortex
Neuromuscular junction (Correct answer)
Peripheral nerve
Skeletal muscle

Correct answer: Neuromuscular junction

The patient's fluctuating weakness, bilateral ptosis worsening with sustained gaze, limited eye movements, and nasal speech are classic signs of myasthenia gravis. The transient improvement following intravenous edrophonium (an acetylcholinesterase inhibitor) confirms a defect in neuromuscular transmission. Myasthenia gravis is an autoimmune disorder where antibodies attack acetylcholine receptors at the postsynaptic membrane of the neuromuscular junction.

Question 20: A 21-year-old woman comes to the physician 2 weeks after being involved in a motor vehicle collision that occurred when she fell asleep while driving. She says that during the past 2 years she has had several incidents of falling asleep at inappropriate times, including while walking. She also reports intermittent loss of muscle tone while awake and occasional sleep paralysis. She does not snore. Physical examination shows no abnormalities. Polysomnography shows a sleep latency of less than 5 minutes and four sleep-onset REM periods. Which of the following is the most likely diagnosis?

Chronic insomnia
Narcolepsy (Correct answer)
Restless legs syndrome
Sleep apnea
Sleep bruxism

Correct answer: Narcolepsy

The patient's constellation of symptoms—excessive daytime sleepiness with inappropriate sleep episodes, intermittent loss of muscle tone while awake (cataplexy), and occasional sleep paralysis—constitutes the classic triad of narcolepsy. The polysomnography findings of short sleep latency and multiple sleep-onset REM periods further confirm this diagnosis, which is characterized by dysregulation of the sleep-wake cycle.

Neuroscience Test 1

A 43-year-old man sustains a wound to the lateral neck.
This results in weakness of elevation and retraction of the shoulder on the ipsilateral side and difficulty turning the head up and toward the contralateral side.
No sensory changes are present.
Which of the following nerves most likely has been injured?