HISTORY AND PHYSICAL EXAMINATION

A 36-year-old white man awoke with binocular diplopia; later that day, he noted blurred vision and lid ptosis. The next morning, he had nausea and vomited twice, and then he had slurred speech and difficulty swallowing. He was admitted to the hospital where magnetic resonance imaging (MRI) of the brain and cerebral angiography were normal. By the third day, he had developed complete ophthalmoplegia, severe dysarthria and dysphagia, and upper extremity weakness. Respiratory failure followed; the patient had to be intubated and required assisted ventilation. The Tensilon test was equivocal.

On examination on day 4, the patient was alert and intubated, and followed commands well. He had bilateral complete ophthalmoplegia to all gaze directions with bilateral ptosis (Figure C24-1). Pupils were dilated and unreactive to light or attempted accommodation. Corneal reflexes were depressed. The patient had bilateral peripheral facial weakness. His tongue was extremely weak, with no fasciculations. His palate did not move volitionally or to gagging. Neck flexors and extensors were weak (Medical Research Council [MRC] 3/5), as were proximal pelvic and shoulder girdle muscles (4/5). However, distal muscles were normal. Deep tendon reflexes were depressed (1/4). Sensation was normal. Cerebellar function also was normal.

Figure C24-1 Pupillary dilatation and ptosis in this patient at the time of diagnosis. The patient also had a complete ophthalmoplegia (not shown).

An electrodiagnostic (EDX) examination was requested.

Please now review the Nerve Conduction Studies and Needle EMG tables.

QUESTIONS

EDX FINDINGS AND INTERPRETATION OF DATA

The relevant EDX findings in this case are:

Figure C24-2 Median compound muscle action potential (CMAP) at rest (waveform 1), and after a brief (10 seconds) period of exercise (waveform 2). Note the significant (90%) facilitation following exercise. Sensitivity = 2 mV/division.

Figure C24-3 Slow repetitive stimulation (2 Hz) of the median nerve. Train 1 is at rest, and Trains 2 through 5 are after 1 minute of exercise. The upper tracing shows all five stimulations. Although a decrement of the compound muscle action potential (CMAP) was evident at rest (13%), there is a dramatic facilitation of CMAP immediately after exercise (compare Train 1 to Train 2), with a subsequent return to baseline.

Figure C24-4 Increment of compound muscle action potential (CMAP) (100%) after rapid (50 Hz) repetitive stimulation of the spinal accessory nerve (sensitivity = 1 mV).

The EDX findings are consistent with a neuromuscular junction disorder of the presynaptic type, as supported by the borderline or low-amplitude baseline CMAPs, and the significant increment (>50%) of the CMAP amplitude after brief exercise and rapid repetitive stimulation of motor nerves. This case is consistent with botulism based on subacute progression of a descending muscle paralysis (ocular to bulbar to limbs), the muscarinic involvement (pupillary dilatation), and the EDX findings (presynaptic blockade). It is not consistent with Lambert-Eaton myasthenic syndrome because of the rapid evolution of symptoms, the prominent oculobulbar muscle weakness, and the relatively modest increment on rapid repetitive stimulation and after brief exercise (see electrodiagnosis).

DISCUSSION