Does measuring the median nerve at the carpal tunnel outlet improve ultrasound CTS diagnosis?

INTRODUCTION: Nerve conduction is often regarded as more sensitive than ultrasonography (US) for diagnosing carpal tunnel syndrome (CTS). The diagnostic value of US derives from median nerve enlargement occurring at both ends of the carpal tunnel resulting in a dumbbell-like swelling from carpal tunnel pressure. An important reason for the inferior sensitivity of US may be because measurements are restricted to the carpal tunnel inlet. We investigate the value of including median nerve enlargement at the carpal tunnel outlet for diagnosing CTS. METHODS: Retrospective cohort study of nerve conduction verified CTS, determining sensitivity, specificity, and positive and negative predictive values of carpal tunnel inlet and outlet median nerve cross sectional area as determined by US for the diagnosis of CTS. Nerve conduction graded CTS severity. RESULTS: 127 hands from 77 patients with CTS and 35 control healthy hands were assessed. US sensitivity for diagnosing CTS increased from 65% to 84% by including outlet enlargement of the median nerve. Specificity changed from 94% to 86%, positive predictive value from 98% to 96% and the negative predictive value from 43% to 60%. 25 hands out of the 127 from CTS patients showed enlargement restricted to the outlet and mainly occurred in moderate CTS. CONCLUSION: In our population, the use of carpal tunnel outlet median nerve enlargement in addition to inlet median nerve size increases sensitivity for diagnosing CTS by 19%.

Combined Doppler and B-mode sonography in carpal tunnel syndrome.

An intraoperatively enlarged engorged median nerve has been described as typical of patients with carpal tunnel syndrome (CTS). Although many studies of CTS have addressed median nerve enlargement, little is known about the usefulness of Doppler methods in detecting median nerve engorgement combined with nerve cross-sectional area (CSA). In a retrospective study of hands referred for evaluation of possible CTS, patients were clinically graded into Highly-likely or Indeterminate CTS. Nerve conduction studies (NCS), CSA, and Doppler analysis were compared. Median nerve blood flow was detected in 29 of 30 Highly-likely CTS hands (mean 13.3m/s (8.2) SD) and in 25 of 30 with Indeterminate CTS (mean 8.5m/s (4.5) SD). These were significantly higher than our laboratory normal values (mean 1.9 m/s (2.8) SD). Raised intraneural blood flow showed the highest test sensitivity in diagnosing Highly-likely carpal tunnel syndrome (83%) and combined with CSA reached 90%. NCS sensitivity was 83%. In the group of Indeterminate CTS, combined blood flow and CSA showed abnormality in 77% and NCS 47%. All nerve conduction parameters and median nerve cross sectional area showed linear correlation to intraneural blood flow velocity (P<0.05; Spearman's r=0.362 to 0.264). This study suggests that adding measures of intraneural blood flow to CSA further improves the sonographic evaluation of CTS and may be of particular use in patients with negative NCS.

Sonography versus nerve conduction studies in patients referred with a clinical diagnosis of carpal tunnel syndrome.

PURPOSE: To compare the diagnostic value of high-resolution ultrasound (US) with nerve conduction studies (NCS) in patients with clinically defined carpal tunnel syndrome (CTS). METHODS: A prospective study was conducted on 66 consecutive patients investigated for sensory hand symptoms. The gold standard was the clinical diagnosis of CTS. RESULTS: NCS showed greater diagnostic sensitivity (82%) than US (62%) in supporting a diagnosis of CTS. With increasing neurophysiologic severity of median neuropathy, there was increasing convergence of the two test methods. Abnormal US as the only diagnostic supportive evidence of CTS was rare. However, the positive predictive value of US for CTS was 100%. CONCLUSION: NCS show better sensitivity than US in supporting a diagnosis of CTS. However, because of its high positive predictive value, one may consider using US as a screening test, eliminating the need for NCS in the majority of clinical suspicion of CTS and reserving NCS for cases in which US is negative.

Sonography as an aid to neurophysiological studies in diagnosing tarsal tunnel syndrome.

Diagnosing tarsal tunnel syndrome can be difficult because of varying clinical diagnostic criteria and equivocal physical signs. We present a case of tarsal tunnel syndrome where nerve conduction identified distal tibial neuropathy and high-resolution sonography was able to show nerve swelling within the tarsal tunnel.

Sensory distribution indicates severity of median nerve damage in carpal tunnel syndrome.

OBJECTIVE: Sensory symptoms within the median nerve distribution are a primary clinical diagnostic criterion for the diagnosis of carpal tunnel syndrome (CTS). However, the distribution of the sensory symptoms in CTS varies from patient to patient. This study identifies the clinical and electrophysiological findings that correlate with the distribution of sensory symptoms in an Asian population with CTS. METHODS: In a prospective study of 105 patients with electrophysiologically confirmed CTS, clinical and educational data were correlated with sensory symptom distribution. RESULTS: Median nerve distribution was strongly associated with more severe nerve conduction abnormality, male gender, and relief by movement. Patients with a complete median sensory distribution had more electrophysiological abnormality than those with an incomplete median distribution. Extra-median distribution was associated with the least nerve conduction abnormality. Educational qualification, age, symptom duration and body mass index were not associated with the pattern of sensory symptoms. CONCLUSIONS: In carpal tunnel syndrome, sensory symptom distribution is strongly dependant on the degree of electrophysiological median nerve damage. Median nerve sensory distribution is associated with severe nerve damage. SIGNIFICANCE: This study provides clinicians with a simple clinical rule for assigning the degree of median nerve damage in patients with CTS based on sensory distribution patterns.