1. Answer: C. Multifocal motor neuropathy (MMN) is a rare disorder and is more common in males with a ratio of 2:1. The presenting features are painless, asymmetrical weakness, atrophy, and fasciculations in the arms usually restricted to one or two nerves. Findings on sensory examination are normal, and reflexes are out of proportion to the weakness of the involved muscles. The electrodiagnostic findings are usually conduction block (typically a 50% reduction in CMAP amplitude and area), segmental demyelination, and normal sensory studies.

2. Answer: B. Approximately 30% of AchR-seronegative patients with myasthenia gravis have the MuSK antibody. These patients are phenotypically different in that they have severe ophthalmoparesis, bulbar, facial, and posterior neck symptoms. The other antibodies are related to other neurologic disorders, anti-GAD with stiff-man syndrome, Ant-Hu with paraneoplastic disease, and anti-GQ1b with Guillain-Barré syndrome.

3. Answer: C. Patients with HIV taking zidovudine (AZT) have been found to develop an inflammatory myopathy with mitochondrial involvement. There are no good controlled studies to date that have proven AZT directly causes this. Some patients have shown improvement with the addition of corticosteroids. This treatment produces increased risk of opportunistic infections, however, and there has been no evidence that there is acceleration of the HIV disease.

4. Answer: E. Rabies involves the medullary respiratory centers that usually produce disproportionate respiratory weakness and usually have no GI prodrome. The rest of the diseases or toxins listed are preceded either by hours to weeks with nausea, vomiting, and abdominal pain.

5. Answer: B. Eighty-five percent of patients with HNPP have shown a deletion of the PMP22 gene on chromosome 17p11. The duplication of the same gene results in CMT type 1A. HSAN type V is Strümpell’s disease, which is CMT plus spastic paraparesis, and CMT type 1B is a mutation in the P0 gene on chromosome 1q22-23.

6. Answer: C. Thallium has been shown to produce all of the symptoms listed. Lead toxicity predominately causes motor weakness; mercury poisoning may cause mood change along with gingivitis, and ethylene glycol causes renal failure, metabolic acidosis, and a severe axonal neuropathy with cranial mononeuropathy.

7. Answer: B. Amyloidosis rarely occurs below the age of 40, has primarily sensory and autonomic findings, 40% of the patients have M-protein on their SPEP, the course is slow and steady and is inherited in an autosomal dominant fashion.

8. Answer: D. The mechanism of action is via inactivation of cobalamin, resulting in myeloneuropathy.

9. Answer: A. Patients with CMT type IV, also known as Refsum’s disease, have autosomal recessive inheritance. It is caused by an accumulation of phytanic acid in many systems, results in night blindness, and is associated with a high consanguinity rate.

10. Answer: B. Of the diseases listed, only Shy-Drager syndrome and Bassen-Kornzweig syndrome (abetalipoproteinemia) are inherited. Shy-Drager syndrome causes an autonomic neuropathy. Abetalipoproteinemia primarily affects large fiber sensory modalities.