Ultrasonographic and functional changes of the ulnar nerve at Guyon’s canal after carpal tunnel release

ObjectiveTo describe morphologic and functional modifications of the ulnar nerve at the wrist in carpal tunnel syndrome (CTS) after carpal tunnel release (CTR).MethodsUltrasonography was used to study the cross sectional area (CSA) of the ulnar nerve at Guyon’s canal, before and 1 and 6 months after CTR, in 18 CTS patients. A parallel electrophysiological and clinical analysis was also conducted.ResultsCSA of the ulnar nerve significantly increased 6 months after CTR. Ten (55%) cases showed abnormal CSA values compared to a control group before surgery and five (28%) at 6 month follow-up. In addition, there were improvements in the motor and sensory ulnar axon recruitment properties and the conduction values in sensory ulnar fibres. Patients with extra-median distribution of paresthesia (4 subjects) were free from symptoms.ConclusionsCTR has a significant effect not only on the anatomical geometry of Guyon’s canal, but also on the morphology and function of the ulnar nerve.SignificanceIn CTS, high pressure in the carpal tunnel may result in anatomical changes of ulnar nerve, thus causing functional impairment to the ulnar fibres. CTR appears to reverse some of this damage.