Sympathetic dysfunction in idiopathic carpal tunnel syndrome : an electrophysiological and power doppler ultrasonographic study

Abstract EN

Background : Vasomotor instability presented by change in hand temperature, color and sometimes Reynaud’s phenomenon seen in Carpal tunnel syndrome CTS patients raise the possibility of sympathetic fiber involvement in such patients.

This might occur with increasing severity of median nerve entrapment.

Studies that investigate sympathetic disturbances in CTS are lacking.

Objective : To investigate sympathetic involvement in idiopathic CTS through evoked sympathetic skin response (SSR) and Power Doppler Ultrasound (PD-US) and correlate it with the severity of median nerve compression.

Methodology : Twenty four idiopathic CTS female patients according to the criteria proposed by the AANEM were the subjects of this study.

They were classified into 3 groups of increasing severity.

Twenty matching apparently healthy volunteers were included as a control group.

The electrically evoked SSR was recorded from the median nerve territory for each patient's hand.

The digital arterial blood flow and the Plasticity Index (PI) in the radialis indicis artery were evaluated.

Results : Eighteen patients had unilateral and 6 had bilateral CTS.

The right side was affected in 19 patients (79.1 %).

The duration of symptoms ranged between 3 and 36 months.

Twenty three hands had sympathetic disturbance manifestations (76.6 %).

Ten hands had mild, 8 hands had moderate and 12 hands had severe CTS.

Those patients showed significant delay of SSR latency (1.62 ± 0.21 sec) and decrease of amplitude (31.53 ± 7.50 µV) as compared to control subjects.

Similarly, a significant delay was detected in the SSR latency (1.62 ± 0.21 sec) and decreased amplitude (30.95 ± 7.66 µV) in the affected hand of CTS patients compared to the unaffected side.

PI of the radialis indicis artery was significantly higher in the hands of CTS group (5.96 ± 1.74) than in the healthy controls (p = 0.05).

PI was found to be significantly higher on the affected side of CTS group (5.56 ± 1.15) than on the unaffected side (p = 0.03).

SSR latency and PI correlated significantly with the sensory nerve conduction velocity, motor distal latency and compound muscle action potential amplitude of the median nerve among patients.

Patients with severe CTS had significantly prolonged SSR latency and higher PI compared to moderate and mild CTS.

Moderate CTS had significantly prolonged SSR latency and higher PI compared to mild CTS.

Conclusions : Abnormal SSR and PI described in the present study indicated that sympathetic dysfunction in idiopathic CTS may be attributed to the involvement of sudomotor and vasomotor sympathetic fibers.

The latter involvement correlated with the severity of median nerve entrapment at the carpal tunnel.

PD-US is an inexpensive and accessible technique in the assessment of vasomotor changes in CTS and could be used as a possible diagnostic tool for the confirmation of CTS.