Section XV. Neurologic Disorders Due to General Medical Illness

Answer d.

Rapid correction of hyponatremia may result in central

pontine or extrapontine myelinolysis characterized by

spastic paraparesis, dysarthria, lethargy, and confusion. A

controlled correction of the sodium level (at a rate of <12

mmol/L daily) is most appropriate.

Answer b.

Patients with hypocalcemia often have paresthesias in

the fingers or around the mouth. The Chvostek sign (facial

muscle contraction when tapping the facial nerve) or the

Trousseau sign (flexor carpal spasm with transient

brachial artery compression) may be present. With severe

hypocalcemia, patients may have seizures and stupor

or coma.

Answer b.

The most common cause of elevated magnesium is kidney

failure. Other common causes include magnesium infu-

sion for eclampsia and select antacids and laxatives.

Tumor lysis syndrome may result in elevated magnesium

but less commonly than kidney failure. Rarely, thiazide

diuretics may cause the magnesium level to decrease

rather than increase. Similarly, celiac disease may result in

a low (not high) magnesium level from poor absorption.

ACE inhibition may affect sodium and potassium rather

than magnesium.

Answer b.

This patient presents with fatigue, sensory loss, gait

unsteadiness, and neurologic examination findings consis-

tent with subacute combined degeneration, which is typi-

cal of vitamin B12 deficiency. An important point is that

vitamin B12 deficiency may occur in patients with low-

normal levels of vitamin B12, while methylmalonic acid

and homocysteine levels may be elevated. This patient

takes metformin, which may be a risk factor for vitamin

B12 deficiency. On neurologic examination, this patient

showed pyramidal findings (hyperreflexia and extensor

plantar responses), which would not be typical of a periph-

eral neuropathy due to diabetes mellitus, so initiation of

insulin or a 2-hour glucose tolerance test would not be

indicated. MRI of the brain would not be indicated because

the pattern of pyramidal findings and lower limb sensory

loss on examination would not be expected to localize to

the brain. This patient’s history is not typical of an infec-

tious process, and the examination findings are not typical

of a polyradiculoneuropathy, so CSF studies are not

indicated.

Answer d.

This patient presents with extremity sensory symptoms of

2 months’ duration, and the neurologic findings indicate

lower limb sensory loss and pyramidal involvement. The

patient has a history of celiac disease, and the elevation of

tissue transglutaminase antibodies is consistent with that

diagnosis. Copper deficiency may result from malabsorp-

tion in active celiac disease. The pattern of findings on

examination is most compatible with a myelopathy with

involvement of dorsal columns and corticospinal tracts,

which is consistent with copper deficiency. While the sen-

sory symptoms and findings on examination could be seen

with a peripheral neuropathy or polyradiculoneuropathy,

the pyramidal findings would not be typical of those pat-

terns of peripheral nervous system dysfunction. The

absence of cranial nerve or upper limb findings on neuro-

logic examination would be atypical of a process involving

the brainstem or parasagittal region of the brain.

XV.6.

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Answer b.

The patient’s clinical history, examination findings, and

MRI results are all compatible with thiamine deficiency.

Immediate parenteral administration of thiamine is neces-

sary when thiamine deficiency is suspected, particularly

in those who are at risk. This patient clearly has risk fac-

tors for thiamine deficiency, which include her compro-

mised nutritional status and vomiting. The history and

MRI findings are not typical of a CNS infection, and the

patient is not described as being febrile or having a head-

ache as is typical with an infectious meningitis or enceph-

alitis. The history is not typical for a seizure disorder or for

Guillain-Barré syndrome. The patient’s history of progres-

sive symptoms and the neurologic examination findings

that suggest involvement of multiple cranial nerves, senso-

rimotor nerves or nerve roots, and cerebellar pathways are

not suggestive of cerebrovascular disease, so CT angiogra-

phy is not indicated.

XV.7. Answer e.

The differential diagnosis of thunderclap headache

includes subarachnoid hemorrhage (from aneurysm, rever-

sible cerebral vasoconstriction syndrome [RCVS], or

trauma); pituitary apoplexy; venous thrombosis; arterial

dissection; RCVS; and hypertensive crisis. These entities

were ruled out with the tests performed, although RCVS

can be difficult to diagnose because symptoms often pre-

cede the imaging evidence of vasospasm by several days.

This patient also had sweating and palpitations, so pheo-

chromocytoma must be ruled out. Further evaluation

would include assessing serum and urine levels of cate-

cholamines and considering adrenal gland imaging.

XV.8. Answer c.

Patients with pituitary apoplexy may present with sud-

den, severe headache; visual field defects; ophthalmople-

gia; and hypopituitarism. Hypopituitarism is associated

with profound vasopressor-refractory hypotension due to

the lack of corticotropin and cortisol (adrenal insuffi-

ciency). Blindness or visual field impairment may develop

from involvement of the nearby optic nerve, optic chiasm,

or oculomotor nerve. Coma and death may occur if the

syndrome is not diagnosed promptly.

XV.9. Answer e.

Secondary hypothyroidism due to pituitary dysfunction

results in decreased thyrotropin and subsequently

decreased T3 and T4 levels (see Table 126.1).

XV.10. Answer c.

Dialysis dysequilibrium syndrome is characterized by

headache, nausea, and blurred vision progressing to con-

fusion and, rarely, coma. It typically occurs in patients

who have missed dialysis or are having their first dialysis.

Typically, the SUN is markedly elevated, and patients

often have other neurologic disease (eg, stroke or head

trauma). The syndrome is thought to be due to transient

cerebral edema. Dialysis dysequilibrium syndrome is sus-

pected when the clinical symptoms and risk factors are

present. However, this syndrome is a diagnosis of exclu-

sion, and the patient would most likely have had blood

glucose and other electrolyte levels assessed; computed

tomography of the head may be required.

XV.11. Answer b.

Intracerebral brain aneurysms occur in about 3% of the US

population. If a patient has 2 or more primary relatives

with an aneurysm, the rate increases to 9% without any

known single-gene cause. Patients with autosomal domi-

nant polycystic kidney disease have an increased risk for

cerebral aneurysm compared to the general population.Initial manifestations of von Hippel-Lindau disease,

which is a hereditary cancer predisposition syndrome, are

most likely related to retinal, cerebellar, or spinal cord

hemangioblastomas. Coarctation of the aorta increases the

risk for cerebral aneurysm, but in most cases it is congeni-

tal and not a hereditary cause. Cobb syndrome is a rare,

nonhereditary disorder characterized by a spinal vascular

malformation with a cutaneous vascular lesion at the same

dermatomal level. Sturge-Weber syndrome is associated

with a port-wine stain and a leptomeningeal capillary

venous malformation of the brain.

XV.12. Answer a.

Management of hepatic encephalopathy commonly starts

with use of lactulose or lactitol (which reduces ammo-

nium absorption).

XV.13. Answer a.

Bacillus anthracis, the agent for anthrax, is transmitted

through inhalation, skin exposure, or ingestion and can

cause hemorrhagic meningitis. Plague, caused by Yersinia

pestis, results from the bite of an infected flea or from per-

son-to-person transmission and may be associated with

meningitis, but the meningitis is not usually hemorrhagic.

A person with plague may also have pneumonia and

enlarged, necrotic lymph nodes. Brucellosis, caused by

Brucella, may be contracted from infected cattle, goats,

sheep, and pigs; it rarely affects the central nervous system,

but when it does, it may cause chronic meningitis. Cyanide

poisoning may result in bright red retinal veins, ataxia,

hyperventilation, seizures, and coma. Eastern equine

encephalitis can be acquired through insect bites. Infected

patients may have fever, headache, and myalgia; less com-

monly, aseptic meningitis and seizure may develop.

XV.14. Answer b.

Clinical syndromes resulting from ciguatera poisoning are

associated with the ingestion of thermostable polyether

toxins. These toxins often affect sodium channels along

peripheral nerves and cause altered sensory perceptions,

including the classic paradoxical perception to tempera-

ture (hot feels cold and vice versa). Ciguatera poisoning can

also cause weakness, fatigue, and depressed muscle stretch

reflexes. α-Bungarotoxin (from elapid snakes) irreversibly

binds to the postsynaptic acetylcholine receptor, causing

paralysis, respiratory failure, and death. Organophosphates

inhibit acetylcholinesterase and cause cholinergic toxicity,

which can include nausea, hypersalivation, increased

bronchial secretions, lacrimation, miosis, fasciculations,

seizures, and coma. Cyanide poisoning may result in bright

red retinal veins, ataxia, hyperventilation, seizures, and

coma. Botulinum toxin, by binding to presynaptic termi-

nals, prevents the release of acetylcholine and often causes

cranial neuropathies (facial weakness, diplopia, dysphagia,

and dysarthria) and symmetric descending weakness along

with urinary retention and constipation.

XV.15. Answer e.

Descent to a lower altitude is the definitive therapy for

high-altitude cerebral edema. Supplemental oxygen, dexa-

methasone, and hyperbaric oxygen may temporize symp-

toms, but descent is the definitive treatment.

XV.16. Answer b.

Checking the carboxyhemoglobin level on arterial blood

gas testing can help in the diagnosis of carbon monoxide

exposure.

XV.17. Answer d.

RLS is a movement and sleep disorder that is character-

ized by an unrelenting urge to move the lower extremities

and is sometimes associated with an uncomfortable sensa-

tion. The prevalence of RLS in pregnancy is 10% to 26%,

with peak onset during the third trimester.

XV.18. Answer a.

Neural tube closure occurs within 4 weeks after an embryo

is formed. Supplementation with folic acid before concep-

tion and during pregnancy has been shown to reduce the

risk of neural tube defects. The recommended dosage for

patients with epilepsy is 10-fold higher (4 mg daily) than

for the general population (0.4 mg daily).

XV.19. Answer c.

While tension and migraine headaches are the most com-

mon headaches during pregnancy, secondary headaches

have more serious morbidity. A thorough history should

establish the presence of any red flags that might suggest

preeclampsia or eclampsia or other secondary causes.

Migraines may increase or decrease during pregnancy and

do not by themselves require imaging. Initial conservative

therapies include exercise, hydration, sleep, relaxation,

physical therapy, and biofeedback. Acetaminophen can be

considered. Although triptans (eg, sumatriptan) and anti-

emetics (eg, ondansetron and promethazine) are generally

in US Food and Drug Administration category C, few stud-

ies support adverse outcomes during pregnancy; however,

there are rare reports of an increased risk of spontaneous

abortion with triptan use.