Neurology

1 In what common situation is a lumbar puncture contraindicated?

In the setting of acute head trauma, signs of intracranial hypertension (e.g., papilledema), or suspicion for subarachnoid hemorrhage. Do a lumbar tap only after you have a negative computed tomography (CT) or magnetic resonance imaging (MRI) scan of the head in these settings. Otherwise, you may cause uncal herniation and death.

2 Cover all but the left-hand column and describe the classic findings of cerebrospinal fluid (CSF) analysis in the following conditions

CONDITION	CELLS (ML)^∗	GLUCOSE (MG/DL)	PROTEIN (MG/DL)	PRESSURE (MM HG)
Normal CSF	0-3 (L)	50-100	20-45	100-200
Bacterial meningitis	>1000 (PMN)	<50	Around 100	>200
Viral/aseptic meningitis	>100 (L)	Normal	Normal/slightly increased	Normal/slightly increased
Pseudotumor cerebri	Normal	Normal	Normal	>200
Guillain-Barré syndrome	0-100 (L)	Normal	>100	Normal
Cerebral hemorrhage^†	Bloody (RBC)	Normal	>45	>200
Multiple sclerosis^‡	Normal/slightly increased (L)	Normal	Normal/slightly increased	Normal

CSF, cerebrospinal fluid; L, lymphocytes; PMN, neutrophils; RBC, red blood cells.

^∗Main cell type is in parentheses after number.

^†Think of subarachnoid hemorrhage, but this pattern may also occur after an intracerebral bleed.

^‡On electrophoresis of CSF, look for oligoclonal bands as a result of increased IgG production and an increased level of myelin basic protein in the CSF during active demyelination.

Note: Tuberculous and fungal meningitis have low glucose (<50) with increased cells (>100), which are predominantly lymphocytes. In patients with fungal meningitis, a positive India ink preparation equals Cryptococcus neoformans.

3 Give a classic case description of multiple sclerosis

Multiple sclerosis classically presents with an insidious onset of neurologic symptoms in white women aged 20 to 40 years with exacerbations and remissions. Common presentations include paresthesias and numbness, weakness and clumsiness, visual disturbances (decreased vision and pain caused by optic neuritis, diplopia as a result of cranial nerve involvement), gait disturbances, incontinence and urgency, and vertigo. Also look for emotional lability or other mental status changes. Internuclear ophthalmoplegia (a disorder of conjugate gaze in which the affected eye shows impairment of adduction) and scanning speech (spoken words are broken up into separate syllables separated by a noticeable pause and sometimes with stress on the wrong syllable) are classic; the patient may have a positive Babinski sign.

4 What is the most sensitive test for diagnosis of multiple sclerosis? How is it treated?

MRI is the most sensitive diagnostic tool and shows demyelination plaques. Also look for increased IgG/oligoclonal bands and possibly myelin basic protein in the CSF. Treatment is not highly effective but includes interferon, glatiramer, mitoxantrone, natalizumab, cyclophosphamide, and methotrexate. Acute exacerbations are treated with glucocorticoids.

5 Define Guillain-Barré syndrome

Guillain-Barré syndrome is a postinfectious polyneuropathy. Look for a history of mild infection (especially upper respiratory infection) or immunization roughly 1 week before onset of symmetric, distal weakness or paralysis with mild paresthesias that start in the feet and legs with loss of deep tendon reflexes in affected areas. The hallmark of the disease is that motor function is often affected with intact or only minimally impaired sensation. As the ascending paralysis or weakness progresses, respiratory paralysis may occur. Watch carefully; usually spirometry is performed to follow inspiratory ability. Intubation may be required. Diagnosis is by clinical presentation. CSF is usually normal except for markedly increased protein. Nerve conduction velocities are slowed. The disease usually resolves spontaneously. Plasmapheresis (for adults) and intravenous immune globulin (for children) reduce the severity and length of disease. Do not use steroids; they no longer have a role in the treatment of Guillain-Barré syndrome.

6 What causes nerve conduction velocity to be slowed?

Demyelination. Watch for Guillain-Barré syndrome and multiple sclerosis as causes.

7 What causes an electromyography (EMG) study to show fasciculations or fibrillations at rest?

A lower motor neuron lesion (i.e., a peripheral nerve problem).

8 What causes an EMG study with no muscle activity at rest and decreased amplitude of muscle contraction upon stimulation?

Intrinsic muscle disease such as the muscular dystrophies or inflammatory myopathies (e.g., polymyositis). You now know enough about EMG for the USMLE.

9 What is the most common cause of syncope? What other conditions should you consider?

Vasovagal syncope is the most common cause and classically is seen after stress or fear. Arrhythmias and orthostatic hypotension are also common. Consider hypoglycemia as a cause. The other main categories include:

Cardiac problems (arrhythmias, hypertrophic cardiomyopathy, valvular disease, tamponade). Always check an electrocardiogram (ECG). Further testing with echocardiography or treadmill stress testing can be performed based on the ECG findings and degree of suspicion.

Neurologic disorders (e.g., seizures, migraine headache, brain tumor). Consider an electroencephalogram or CT/MRI scan if history suggests seizures or intracranial lesion.

Vascular disease (consider transient ischemic attacks (TIAs) or carotid stenosis, which can be ruled out with carotid artery ultrasound/duplex scanning, although this is not a common cause of syncope).

Medication effects (e.g., anticholinergic agents, beta blockers, narcotics, vasodilators, alpha-agonists, antipsychotics).

As many as half of patients have syncope of unknown cause after a standard diagnostic evaluation.

10 Cover the right-hand column and localize the neurologic lesion for each of the following symptoms and signs

SYMPTOM/SIGN	AREA
Decreased or no reflexes, fasciculations, atrophy	Lower motor neuron disease (or possibly muscle problem)
Hyperreflexia, clonus, increased muscle tone	Upper motor neuron lesion (cord or brain)
Apathy, inattention, disinhibition, labile affect	Frontal lobes
Broca (motor) aphasia	Dominant frontal lobe^∗
Wernicke (sensory) aphasia	Dominant temporal lobe^∗
Memory impairment, hyperaggression, hypersexuality	Temporal lobes
Inability to read, write, name, or do math	Dominant parietal lobe^∗
Ignoring one side of body, trouble with dressing	Nondominant parietal lobe^∗
Visual hallucinations/illusions	Occipital lobes
Cranial nerves III and IV	Midbrain
Cranial nerves V, VI, VII, and VIII	Pons
Cranial nerves IX, X, XI, and XII	Medulla
Ataxia, dysarthria, nystagmus, intention, tremor, dysmetria, scanning speech	Cerebellum

^∗The left side is dominant in more than 95% of the population (99% of right-handed people and 60% to 70% of left-handed people).

11 For delirious or unconscious patients in the emergency department with no history of trauma, for what three common causes should you think about giving empirical treatment?

Hypoglycemia (give glucose)

Opioid overdose (give naloxone)

Thiamine deficiency (give thiamine before giving glucose in a suspected alcoholic patient)

Other common causes are alcohol, illicit drugs, prescription drugs, diabetic ketoacidosis, stroke, and epilepsy or postictal state.

12 What are the classic differential points between delirium and dementia?

	DELIRIUM	DEMENTIA
Onset	Acute and dramatic	Chronic and insidious
Common causes	Illness, toxin, withdrawal	Alzheimer disease, multi-infarct dementia, HIV/AIDS
Reversible	Usually	Usually not
Attention	Poor	Usually unaffected
Arousal level	Fluctuates	Normal