A study of median nerve cross sectional area in patients with mild to moderate idiopathic carpal tunnel syndrome

Abstract

Introduction: Carpal tunnel syndrome is the most common entrapment neuropathy and is caused by median nerve compression at the wrist as it passes through carpal tunnel. Aim: To detect cross sectional area (CSA) of median nerve at the level of distal palmar crease and ratio of cross sectional area at level of proximal carpal tunnel to area 5 cm proximal to carpal tunnel using ultrasound. Materials and Methods: Consecutive patients of age between 18 and 70 years, who presented with paraesthesia of hands (aggravated by holding or keeping hand elevated or with history of nocturnal worsening) and electrophysiological confirmed as mild to moderate idiopathic cases of carpal tunnel syndrome were included in the study. Baseline nerve conduction study was done as per standard protocol for carpal tunnel syndrome. Nerve ultrasound was done with high frequency linear-array transducer (7-14 Hz). Results: 50 wrists in 30 Patients with CTS were studied. Females were more involved with a male: female ratio of 1:5. Mean age was 56.8 years (range 25–82 years). Majority of the cases were bilateral (67%). Dominant hand was involved more (80%) than non-dominant one. Most common symptoms were numbness (100%) and paraesthesia on holding (90.91%). On nerve ultrasound, all patients had CSA of median nerve at proximal carpal tunnel more than 10 square millimetre .The wrist fore-arm CSA ratio was more than 1 in all cases. Majority of the hands were having a cross sectional area 10-11.9 square millimetre and more than 16 square millimetre. We found correlation between CSA at distal palmar crease and median sensory conduction studies. Conclusion: Our study affirms previous studies in demonstrating the usefulness of ultrasonography in diagnosing CTS. Median nerve Cross-sectional area can be used for clinical screening of Carpal tunnel syndrome patients. Keyword: Carpal tunnel syndrome, Cross sectional area, Wrist-ultrasound.