Background Sonography is a diagnostic tool with great development in diagnosing entrapment neuropathy. It's an easy, painless, fast, non-invasive technique and can explore how the nerve's morphology and pathologies are associated. An electroneurogram is used to assess the intensity of nerve involvement.
Objectives To determine the relationship between the intensity of nerve involvement by electroneurogram and the measurement of the cross-sectional area (CSA) of the median nerve by sonography in patients with idiopathic carpal tunnel syndrome (CTS) waiting for surgery.
Methods 56 wrists of 39 consecutive patients waiting for surgery were tested, however 5 were excluded because were found to have anatomic variants (4 bifid nerves, 2 median arteries) and 1 fybrolipoma. Therefore, the final sample was 51 wrists of 37 consecutive patients (11 male and 26 females), with a mean age of 59.2 years (26–85), all with electrophysiologically confirmed idiopathic CTS. Patients were classified by their electrophysiologic grade. The median nerve cross-sectional area at proximal and distal carpal tunnel was measured using high frequency ultrasound.
Relationships between CSA, the severity of the electrophysiologic grade and the duration of symptoms were analysed. Also, a median nerve morphological characteristics examination (hipoecogenicity, loss of fascicular structure, Power Doppler signal and anatomical variants) was undertaken.
A comparison between CSA and the severity of the electrophysiologic grade was made using an independent T test and the connection between CSA and the duration of symptoms was calculated using ANOVA test.
Results Patients were classified by their electrophysiologic severity grade (8 mild, 13 moderate, 29 severe and 1 very severe). The mean ultrasound area of distal medial nerve was 8.7 mm2 in mild-moderate and 9.2 mm2 in severe-very severe cases (p=0.52). The average of proximal CSA was 11.6 mm2 in mild-moderate and 14.1 mm2 in severe-very severe cases with statistical signification differences (p=0.026). Relationship between CSA and symptom's duration wasn't identified. In 89.2% of the cases, hipoecogenicity and the loss of fascicular structure were observed but no cases were found to show positive Power Doppler signal.
Conclusions The most valid and relevant parameter regarding the electroneurogram in the diagnosis of CTS is CSA at proximal carpal tunnel by sonography. A cross-sectional area measuring more than 9–10 mm2 has been suggested to be pathologic and our study confirms these results. While the electroneurogram is the gold-standard method in the diagnosis of nerve involvement severity, a sonography could improve the diagnostic sensibility and give information about nerve's morphology and associated pathologies.
Disclosure of Interest None declared