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.