Entrapment neuropathy of the palmar cutaneous branch of the median nerve in carpal tunnel syndrome.
OBJECTIVE
The aim of this study is to elucidate the significance of electrophysiological data of the palmar cutaneous branch of the median nerve (PCBm) in the diagnosis entrapment of the PCBm concomitant with carpal tunnel syndrome (CTS).


METHODS
Clinical and electrophysiological studies were conducted for abnormal sensation of the thenar eminence in eight CTS patients. Sensory nerve action potentials (SNAPs) of the PCBm were recorded from bipolar surface electrodes over the forearm using an orthodromic method. The preoperative SNAP evaluation was compared with the operative findings.


RESULTS
The eight patients were divided into two groups based on the characteristics of SNAPs of the PCBm; five patients had normal SNAPs of the PCBm and three patients had delayed or absent SNAPs. Open surgery confirmed entrapment of the PCBm in one patient in the first group and all patients in the latter group.


CONCLUSIONS
Although clinical symptoms were not always reliable to diagnose entrapment of the PCBm in CTS, electrophysiological study of the PCBm was highly sensitive (75%) and entirely specific (100%) to demonstrate the entrapment of the PCBm preoperatively.
Department of Neurology, Sapporo Medical University School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido 060-8543, Japan. toimai@sapmed.ac.jp
Tomihiro
T
Imai
Takuro
T
Wada
Hiroyuki
H
Matsumoto
D000200:Action Potentials; D000328:Adult; D002349:Carpal Tunnel Syndrome / Q000150:complications*; D004568:Electrodiagnosis / Q000379:methods; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D009408:Nerve Compression Syndromes / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D009431:Neural Conduction; D009475:Neurons, Afferent; D012680:Sensitivity and Specificity; D012867:Skin / Q000294:innervation*