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The anterior interosseous nerve is a pure motor nerve supplying the flexor pollicis longus, flexor digitorum profundus to the index and middle finger, and the pronator quadratus. A relatively uncommon neuropathy of this nerve, called the anterior interosseous syndrome (AIS), sometimes occurs. This paper reports 2 cases of AIS which developed from unusual etiologies. The first patient developed AIS after some difficulty drawing blood from the cubital vein, while the second patient developed symptoms following bypass surgery involving intravenous injection in the cubital vein. Although the diagnosis of AIS can be made clinically by noting muscle weakness in the absence of sensory deficits, electrodiagnosis is helpful for confirming diagnosis and predicting prognosis.

Four intrinsic muscles were studied with electromyography (EMG) in asymptomatic feet in 70 individuals to ascertain the percentage having abnormal potentials (positive sharp waves and/or fibrillation potentials). The number having positive sharp waves ranged from 6(8.6%) in the 1st dorsal interosseous to 11(15.7%) in the extensor digitorum brevis. The number showing fibrillation potentials ranged from 0 for the abductor hallucis to 4(5.7%) for the abductor digiti minimi. The authors concluded that using positive sharp waves as a diagnostic criterion in using EMG of intrinsic foot muscles in the evaluation of certain neuromuscular problems such as radiculopathy and tarsal tunnel syndrome may be misleading, but using the presence of fibrillation potentials as a criterion may be useful. Differences in the pattern of abnormalities in males and females are also discussed.

The purpose of this study was to determine and standardize an easy and convenient method of studying the orthodromic latencies of the medial and lateral plantar nerves for clinical purposes using conventional equipment. Forty-one able-bodied adult subjects ranging in age from 20 to 76 years were tested orthodromically to establish normal values over fixed distances. The temperatures of the feet ranged from 26C to 32C. A standard TECA bipolar surface electrode fixed in a plastic mount was placed on the posterior tibial nerve proximal to the flexor retinaculum. The medial plantar nerve was stimulated with a bipolar surface stimulator at a distance of 10, 14, and 18cm, and at the great toe. The lateral plantar nerve was stimulated at a distance of 14 and 18cm, and at the little toe. Orthodromic latencies for the medial plantar nerve for distances of 10, 14 and 18cm, and the great toe were 2.4 +/- SD 0.15msec, 3.2 +/- SD 0.26msec, 4.0 +/- SD 0.22msec, and 5.0 +/- SD 0.38msec, respectively. Lateral plantar nerve latencies for 14 and 18cm segments were 3.2 +/- SD 0.25msec and 4.0 +/- SD 0.27msec, respectively. These standard values should allow more accurate assessment of tarsal tunnel syndrome (TTS) and peripheral neuropathies because the orthodromic method involves a mixed motor and sensory nerve action potential and should be more sensitive to early changes than a pure motor nerve action potential.

A serendipitous observation that many individuals with carpal tunnel syndrome have square wrists led to this study which correlates wrist dimensions with median sensory latencies. Results suggest that the squarer the wrist the longer the latencies.