Electrophysiological evidence of a relationship between idiopathic carpal and tarsal tunnel syndromes.

Electrophysiological findings are reported suggesting a relationship between idiopathic tarsal (TTS) and carpal tunnel syndromes (CTS) to explain that the coexistence of both entrapment syndromes in the same patients is not coincidental. Sixty-five patients with idiopathic CTS and 15 with idiopathic TTS were selected. None of the patients with CTS reported any symptoms, nor did they have any signs of TTS, and vice versa. Distal sensory conduction velocity (SCV) of the tibial nerve was reduced in ten of 65 patients with CTS; in five of these ten patients, tibial distal motor latency (DML) was also delayed. Reduced SCV and increased DML were evident in the median nerve of two patients with TTS. The mean of DML and SCV of the tibial nerve in the CTS group and of the median nerve in the TTS group were significantly reduced with respect to the control group without differences in the conduction of the ulnar, deep peroneal and sural nerves. This indicates that there was subclinical involvement of the median and tibial nerves in these patients. Besides having a narrow carpal tunnel, patients with CTS presumably also have a narrow tarsal tunnel and vice versa, and are therefore prone to develop both nerve entrapment syndromes. The different incidence of the two syndromes is explained on the basis of anatomical and functional differences between the two nerves.