196. In Tay-Sachs disease, the enzymatic abnormality responsible for the neurological deficits is deficiency of which of the following?
a. Hexosaminidase A
b. Glucocerebrosidase
c. Phosphofructokinase
d. Glucose phosphorylase
e. Sphingomyelinase
197. An 8-month-old boy develops spasticity, head retraction, and difficulty swallowing. His physician discovers an abnormal accumulation of glucosylceramide and tells the parents their child will continue to deteriorate and likely die within 3 years. This child has which of the following?
a. β-glucosidase deficiency
b. Niemann-Pick disease
c. Krabbe disease
d. Fabry disease
e. Tay-Sachs disease
198. A 53-year-old left-handed man presents with asterixis, esophageal varices, splenomegaly, and abdominal ascites. He is likely to exhibit altered consciousness on the basis of which of the following?
a. Renal tubular acidosis
b. Impaired hepatic detoxification of portal blood
c. Splenomegaly-induced anemia
d. Copper intoxication
e. Vitamin B12 deficiency
199. A patient has had progressive, chronic liver failure for the past 5 years. At the time of death, he would be expected to exhibit changes in which type of brain cells?
a. Oligodendrocytes
b. Striatal neurons
c. Pigmented cells of the substantia nigra
d. Astrocytes
e. Inferior olivary neurons
200. A 42-year-old man presents to the emergency room with seizures, mental status change, and vision difficulties. A magnetic resonance imaging (MRI) reveals an abnormally high T2 signal in the posterior cerebral white matter. There is proteinuria, and blood pressure is 210/120 mm Hg. The cerebrospinal fluid (CSF) protein content of this patient is likely to be which of the following?
a. Abnormally low
b. Normal
c. Elevated, but less than 100 mg/dL
d. Elevated to between 500 and 1000 mg/dL
e. Greater than 2000 mg/dL
201. A 65-year-old man has had many years of deteriorating kidney function caused by diabetes. At age 59, dialysis was begun because of electrolyte abnormalities. Which of the following is the most common neurological complication of chronic renal failure?
a. Peripheral neuropathy
b. Delirium
c. Seizures
d. Dementia
e. Labile affect
202. A 70-year-old woman with end-stage renal disease tends to develop restless legs syndrome as she becomes uremic. This may be controlled with which of the following drugs?
a. Haloperidol
b. L-Dopa
c. Caffeine
d. Nifedipine
e. Rifampin
203. A 56-year-old woman has been on dialysis for the past 10 years owing to chronic renal failure from cystic kidney disease. Which of the following is the most reliable treatment for the peripheral neuropathy associated with her condition?
a. Thiamine supplements
b. Clonazepam
c. Phenytoin
d. Minoxidil
e. Renal transplant
204. A 68-year-old man presents with acroparesthesia, sensory ataxia, memory loss, and impotence. On examination, there are upper motor neuron signs in all four extremities. He also has anemia and a sore tongue. Eventually, a nutrient deficiency is diagnosed. This nutrient, critical for normal neurological function, must be absorbed by binding to which of the following?
a. A cyanide atom and form cyanocobalamin
b. An intrinsic factor
c. The parietal cells of the stomach
d. The ileal mucosa
e. The jejunal mucosa
205. A patient has a borderline low vitamin B12 level. Testing for what compound is a more sensitive test for B12 deficiency?
a. Cysteine
b. Methylmalonic acid
c. Methionine
d. Succinic acid
e. Propionic acid
206. The patient with impaired vitamin B12 absorption is likely to develop a positive Romberg test because of damage to which of the following?
a. Cerebellar vermis
b. Cerebellar hemispheres
c. Spinal cord lateral columns
d. Basal ganglia
e. Spinal cord posterior columns
207. Which of the following types of visual field cuts is most often seen with vitamin B12 deficiency?
a. Centrocecal scotoma
b. Homonymous hemianopsia
c. Bitemporal hemianopsia
d. Binasal hemianopsia
e. Hemianopsia with central sparing
208. A 42-year-old woman is being treated with methotrexate for Wegener granulomatosis. Methotrexate may be associated with the syndrome of reversible posterior leukencephalopathy. She is also at risk for megaloblastic anemia because methotrexate disturbs the metabolism of which of the following?
a. Cobalamin
b. Iron
c. Copper
d. Pyridoxine
e. Folate
209. A 37-year-old woman develops cholecystitis and requires cholecystectomy. Her family advises the physicians involved that she has a long history of alcoholism and benzodiazepine use, including diazepam, lorazepam, and clonazepam. Approximately 7 days after the surgery, the patient becomes increasingly agitated, delusional, and suspicious. Routine investigations reveal no evidence of focal or systemic infection. Hepatic, renal, and hematologic parameters are largely normal. Within 24 hours of these cognitive and affective changes, the patient has a generalized tonic-clonic seizure. MRI and computed tomography (CT) studies of the brain are normal, and her CSF is unremarkable. In consideration of the abuse history provided by the family, medication orders prior to the surgery should have included which of the following?
a. Haloperidol
b. Chlorpromazine
c. Trihexyphenidyl
d. Prochlorperazine
e. Thiamine
210. A 55-year-old right-handed man is admitted to the medical service for pneumonia. The patient normally drinks 4-to-8 beers per day. In anticipation of the seizures, cognitive deterioration, and autonomic instability that might occur during withdrawal, which of the following is the most appropriate measure to take?
a. Consult a “detox center” to start planning the patient’s discharge.
b. Provide intravenous alcohol supplements to blunt the alcohol withdrawal.
c. Provide intramuscular or oral chlordiazepoxide several times daily at a dose dictated by the patient’s level of agitation.
d. Start phenytoin as a single dose nightly.
e. Delay pneumonia treatment until the risk of neurological problems abates.
Questions 211 to 217
For each clinical scenario, select the nutritional deficiency that is most likely responsible. Each lettered option may be used once, more than once, or not at all.
a. Deficiency amblyopia
b. Vitamin B12 deficiency
c. Pyridoxine (vitamin B6) deficiency
d. α-Tocopherol (vitamin E) deficiency
e. Vitamin D deficiency
f. Thiamine (vitamin B1) deficiency
g. Nicotinic acid deficiency
h. Kwashiorkor
i. Vitamin C deficiency
211. A 26-year-old man develops hemoptysis and dyspnea over the course of 3 months. His physician suspects tuberculosis and starts him on triple therapy with isoniazid (isonicotinic acid hydrazide), rifampin, and ethambutol. After 1 month of treatment, the patient’s liver enzymes show slight elevations, but the treatment is continued. The hemoptysis stops by 2 months, but the patient complains of pins-and-needles sensations in his feet. Neurological examination reveals hypoactive deep tendon reflexes in the legs and slightly impaired position sense. Strength is good in all limbs.
212. A 50-year-old woman is found wandering in the street and is brought to the emergency room by the police. She is disoriented to time, place, and person, but has no evidence of head trauma. She staggers when she tries to walk, but she has no detectable alcohol in her blood. Eye movements are abnormal with paresis of conjugate gaze, and horizontal nystagmus is apparent. Relatives are contacted, and they report that this woman has a long history of alcohol abuse.
213. A 46-year-old man complains of progressive visual problems. He notices problems with discriminating objects both up close and far away. His deficits have progressed over the course of 3 months. He has a 12-year history of pipe smoking, a 14-year history of daily aspirin use, and a 20-year history of alcohol intake. He usually drinks 4 oz of gin daily. Examination reveals enlargement of the physiologic blind spot to the point where it extends into central vision.
214. A 32-year-old South African woman develops irritability, sleeplessness, and fatigue. Her family believes that she is depressed, but neurological assessment establishes prominent short- and long-term memory problems. She has anemia and an obvious dermatitis on her face. Her diet is strictly vegetarian and limited almost entirely to grains, such as corn.
215. A 61-year-old man develops progressive cramping of his legs and a pins-and-needles sensation in his feet over the course of 1 year. He consults a physician when he notices paresthesias in his hands and unsteadiness of his gait. His family reports that he has had some urinary incontinence, but was too embarrassed to report it. On examination, he has a spastic paraparesis with severe disturbance of position and vibration sense in his legs. Despite obvious spasticity in the legs, the deep tendon reflexes are absent at the knees and ankles. Peripheral blood smear reveals hypersegmented polymorphonuclear leukocytes.
216. A 4-year-old boy develops progressive gait ataxia and limb weakness over the course of 3 months. Neurological assessment reveals diffusely absent deep tendon reflexes, proximal muscle weakness, ophthalmoparesis, and poor pain perception in the feet. Blood tests reveal elevated creatine phosphokinase levels and abnormally high serum bilirubin levels. Further investigations of hepatic function reveal that the child has a cholestatic hepatobiliary disorder, but there is no evidence of hepatic dysfunction sufficient to cause an encephalopathy.
217. A 9-month-old girl from famine-stricken Ethiopia exhibits profound apathy and indifference to her environment. She is afebrile and appears to have no significant infections at the time of her initial evaluation. Her hair is sparse, and slight edema is evident about her ankles. She is well below the fifth percentile for height in her age group. With handling she becomes irritable, but throughout her examination she exhibits little spontaneous movement. Her mother reports having seen transient tremors in the girl’s hands a few weeks earlier, but these abated after a few days.
Questions 218 to 224
For each clinical scenario, select the most likely diagnosis. Each lettered option may be used once, more than once, or not at all.
a. Postictal state
b. Hypothyroidism
c. Uremic encephalopathy
d. Wernicke encephalopathy
e. Herpes encephalitis
f. Progressive multifocal leukoencephalopathy
g. Meningeal carcinomatosis
h. CNS toxoplasmosis
i. Multiple sclerosis
j. Hepatic encephalopathy
k. Subacute combined systems disease
l. Meningococcal meningitis
m. Subacute sclerosing panencephalitis
n. AIDS encephalopathy
o. Pickwickian syndrome
218. A 23-year-old woman with a history of hemophilia notices progressive memory difficulty. She has required little hematologic support, but she did receive transfusion of factor VIII at least five times over the past 7 years. Neurological examination reveals word-finding difficulty, poor recent and remote memory, gait ataxia, mild dysarthria, and alabile affect. Her right plantar response is extensor, and her left brachioradialis reflex is hyperactive with transient clonus. An MRI of the brain is unrevealing.
219. A 35-year-old businessman has sleep attacks. He runs a chain of dry-cleaning stores, but does not usually work with the cleaning fluids. He reports falling asleep several times during the workday, even at business meetings and during interviews. He has developed the sleep attacks only after gaining more than 100 lb. His weight at the time of the examination is 324 lb.
220. A 19-year-old man develops obvious personality changes over the course of 2 weeks. He becomes agitated with little provocation and abuses his wife both verbally and physically. His behavior is sufficiently atypical for it to prompt his relatives to seek psychiatric assistance for him. While being interviewed by a psychiatrist, he becomes unresponsive and develops generalized convulsions with opisthotonic posturing, tonic-clonic limb movements, and urinary incontinence. He is hospitalized for investigation of his seizure disorder. On initial examination, he is noted to have a low-grade fever and a mild left hemiparesis. His CSF opening pressure is 210 mm H2O. His CSF cultures yield no growth, and his electroencephalogram (EEG) reveals polyspike-and-wave discharges originating in the right temporal lobe. A CT of his brain reveals focal swelling of the right temporal lobe.
221. A previously healthy 25-year-old woman develops acute loss of vision in her left eye. She awakens with pain in the eye and reduction of her acuity to perception of light and dark. She delays seeing a physician for 1 week, during which time her acuity gradually improves sufficiently to allow her to read. On examination, the physician discovers she has slurred speech and poor rapid alternating movements with the left hand. Ocular dysmetria is evident in both eyes. Her tandem gait is grossly impaired. The physician obtains an EEG, which is normal.
222. A 17-year-old man has headache and photophobia on awakening. His physician discovers a low-grade fever and resistance to neck flexion. The physician advises the patient to take acetaminophen and remain in bed for the next 24 hours. Within 12 hours, the patient develops nausea and more intense headache. He seems disoriented and inappropriately lethargic. His family brings him to an emergency room. The emergency room physician notes a petechial rash on the legs and marked neck stiffness. CSF examination reveals a glucose content of 5 mg/dL, protein content of 87 mg/dL, and cell count of 112 leukocytes, with 70% polymorphonuclear cells.
223. A 56-year-old man is struck over the parietal area of the head during a robbery. He loses consciousness for 35 minutes but has no focal weakness or numbness on regaining consciousness. Within 2 days of the incident, his wife finds him unresponsive in bed early in the morning. She calls for an ambulance, but before it arrives her husband becomes more alert and asks for something to eat, saying he wants to have some supper before he goes to bed for the night. The ambulance attendant first on the scene notes that the patient is disoriented to place and time and has weakness of his right arm and leg.
224. A 35-year-old woman is found unconscious on the floor of her apartment. A bottle of cleaning fluid is found on a table near her. One of the contents indicated in the fluid is carbon tetrachloride. The ambulance crew notes that the patient is breathing independently, but her breath has a distinctly fetid odor unlike that associated with the cleaning fluid. Her limbs are flaccid, and she groans when she is moved. She does not respond to inquiries and is poorly responsive to pain. A serum ammonia level obtained at the emergency room is 250 mg/dL, triple the normal level. EEG reveals triphasic waves, most prominently over the front of the head.