Clinical Reasoning: A 79-year-old man with polyneuropathy and dysautonomia

A 79-year-old man was referred to the neuromuscular clinic for evaluation of severe polyneuropathy. Four years ago, he noted bilateral lower extremity numbness below the knee, particularly in his shins. At the time he also had a right transcarpal ligament release at an outside institution for a diagnosis of carpal tunnel syndrome. This procedure did not provide any relief of his right-hand numbness. He also had numbness in his left hand. One year ago, he began tripping over his feet due to ankle weakness, resulting in falls on several occasions. Concurrently, he complained of burning in the hands more than in the feet, and treatment with gabapentin and a topical Lidoderm patch was started. Six months ago, he started having bilateral hand weakness with trouble opening jars or manipulating buttons. At the same time, he developed near-syncope and was found to have orthostatic hypotension, and treatment with midodrine was started. A Foley catheter was placed 1 year ago because of urinary retention and bilateral hydronephrosis, attributed at the time to benign prostatic hypertrophy. He also noted erectile dysfunction and constipation for a few years. The patient reported an involuntary 25-pound weight loss in the last year. His medical history included bilateral cataract surgery at 75 years but was otherwise negative. He denied any family history of neuropathy. He was a heavy smoker but did not drink or use illicit drugs. There were no toxic exposures. His general examination showed a drop of 20 mm Hg in his systolic blood pressure when standing without an increase in pulse rate. His mental status and cranial nerves were normal. His intrinsic hand muscles were atrophic. He had bilateral mild proximal and severe distal weakness in his arms and legs. He had loss of sensation to pinprick up to the knees and midforearms bilaterally …