When is needle examination of thenar muscle necessary in the evaluation of mild and moderate carpal tunnel syndrome?

Objectives: This study aims to evaluate the predictors of standard nerve conduction study (NCS) parameters in determining the presence of axonal loss by means of spontaneous activity in patients with mild and moderate carpal tunnel syndrome (CTS). Patients and methods: Between May 2015 and April 2018, a total of 118 patients (11 males, 107 females; mean age: 52.3±10.6 years; range, 27 to 79 years) who underwent electrophysiological studies and were diagnosed with CTS were included. Demographic data of the patients including age, sex, and symptom duration were recorded. Electrodiagnostic studies were performed in all patients. All the needle electromyography (EMG) findings were recorded, but only the presence or absence of spontaneous EMG activities was used as the indicator of axonal injury. Results: In 37 (31.4%) of the patients, spontaneous activity was detected at the thenar muscle needle EMG. No spontaneous activity was observed in any of 43 (36.4%) patients with normal distal motor latency (DML). There were significant differences in DMLs, compound muscle action potential (CMAP) amplitudes, sensory nerve action potentials amplitudes, and sensory nerve conduction velocities between the groups with and without spontaneous activity (p<0.05). The multiple logistic regression analysis revealed that DML was a significant independent risk variable in determining presence of spontaneous activity. The most optimal cut-off value for median DML was calculated as 4.9 ms. If the median DML was >4.9 ms, the relative risk of finding spontaneous activity on thenar muscle needle EMG was 13.5 (95% CI: 3.6-51.2). Conclusion: Distal motor latency is the main parameter for predicting the presence of spontaneous activity in mild and moderate CTS patients with normal CMAP. Performing needle EMG of the thenar muscle in CTS patients with a DML of >4.9 ms may be beneficial to detect axonal degeneration in early stages.

Prolonged distal motor latency of median nerve does not improve diagnostic accuracy for CIDP

Compression of the median nerve at the carpal tunnel can give demyelinating features and result in distal motor latency (DML) prolongation fulfilling the EFNS/PNS demyelinating criteria for chronic inflammatory demyelinating polyneuropathy (CIDP). Accordingly, being carpal tunnel syndrome (CTS) common in the general population, the EFNS/PNS guidelines recommend excluding the DML of the median nerve when DML prolongation may be consistent with median neuropathy at the wrist from CTS. The main aims of this study were to verify whether the inclusion of DML of the median nerve (when consistent with CTS) could improve electrophysiological diagnostic accuracy for CIDP and if the median nerve at the carpal tunnel was more prone to demyelination. We analyzed electrophysiological data from 499 patients included consecutively into the Italian CIDP Database. According to the EFNS/PNS criteria, 352 patients had a definite, 10 a probable, and 57 a possible diagnosis of CIDP, while 80 were not fulfilling the diagnostic criteria. The inclusion of DML prolongation of median nerve did not improve significantly the diagnostic accuracy for CIDP; overall diagnostic class changed in 6 out of 499 patients (1.2%) and electrodiagnostic class of CIDP changed from not fulfilling to possible in only 2 patients (2.5% of not-fulfilling patients). In conclusion, we can infer that excluding DML prolongation of median nerve does not increase the risk of missing a diagnosis of CIDP thus corroborating the current EFNS/PNS criteria.

Cervical spondylosis as a possible hidden reason beyond delayed phrenic nerve distal motor latency

Background Cervical spondylosis is a chronic degenerative condition of the cervical spine that can affect the cervical nerve roots. The origin of the phrenic nerve makes it vulnerable to injury. The purpose of this study is to investigate possible subtle phrenic nerve affection in patients with cervical spondylosis using nerve conduction studies (NCS). This study was conducted on 30 patients with cervical spondylosis above C5 and on 30 healthy volunteers. Nerve conduction studies of both phrenic nerves were performed in all cases. Results The patients with cervical spondylosis showed a statistically highly significant prolongation of phrenic nerve distal motor latency (DML) than the control group (P < 0.01). There was no significant difference regarding amplitude (P > 0.05). There was a significant correlation between DML and X-ray score (r < 0.05). Conclusions Cervical spondylosis is an underestimated cause of phrenic nerve delayed DML. There is a correlation between the delay of phrenic nerve DML and the severity of cervical spondylosis.

A Single-Center Prospective Observational Study of Ultrasonography for 6 Months after Surgical Decompression of the Median Nerve at the Carpal Tunnel

Objective To determine the natural history of the morphology of the median nerve after carpal tunnel decompression. Methods Between October and December 2014, patients with suspected carpal tunnel were prospectively enrolled and underwent pre- and postoperative (3 and 6 months) high-definition ultrasonography, electrophysiology, and clinical testing. Results A total of 81 patients were enrolled in the study; 75 (93%) could be reached for the 6-month follow-up, and 100% were clinically better at the 6-month follow-up. The mean cross-sectional area decreased from 14.3 ± 4.4 mm2 to 9.6 ± 2.3 mm2 (mean ± standard deviation [SD]). The mean distal motor latency decreased from 6.5 ± 2.2 msec to 4.4 ± 0.8 msec (mean ± SD). Distal motor latency improved statistically significantly after surgical decompression as well, but sooner. Conclusion We present the second largest series of patients with sonographic follow-up after surgical decompression of the carpal tunnel.

Sonographic short-term follow-up after surgical decompression of the median nerve at the carpal tunnel: a single-center prospective observational study

OBJECT Carpal tunnel syndrome causes increased cross-sectional area (CSA) of the median nerve, which can be assessed by high-definition ultrasonography. It is unclear today, however, whether high-definition ultrasonography may play a role in the postoperative period. This prospective study aimed to determine the natural history of the morphology of the median nerve at the carpal tunnel after surgical decompression assessed by high-definition ultrasonography. METHODS Between October and December 2014, patients with suspected carpal tunnel syndrome who were referred to the authors’ center for peripheral neurosurgery were prospectively enrolled and underwent pre- and postoperative (3 months) high-definition ultrasonography, electrophysiology, and clinical testing. RESULTS Eighty-one patients were enrolled in the study, and 100% were clinically better at the 3-month follow-up. The mean CSA decreased from 14.7 ± 4.9 mm2 to 12.4 ± 3.4 mm2 (mean ± SD, p < 0.0001). The mean distal motor latency decreased from 6.6 ± 2.4 msec to 4.8 ± 1.0 msec (mean ± SD, p < 0.0001). Ninety-eight percent of patients who were available for electrodiagnostic follow-up showed an improvement of the distal motor latency; only 80% had a reduction in the CSA. CONCLUSIONS The authors present the second-largest series of patients with sonographic follow-up after surgical decompression of the carpal tunnel reported in the literature so far. This study, which showed a decrease in size of the median nerve after surgical decompression, suggests that the preoperative increase in median nerve CSA at the carpal tunnel may be due to compression and that enlargement of the median nerve is (partially) reversible.