The Relationship between Nerve Conduction Study and Clinical Grading of Carpal Tunnel Syndrome.

INTRODUCTION: Carpal Tunnel Syndrome (CTS) is the most common nerve entrapment. Subjective sensory symptoms are common place in patients with CTS, but sometimes they are not supported by objective findings in the neurological examination. Electrodiagnostic (EDx) studies are a valid and reliable means of confirming the diagnosis. The amplitudes along with the conduction velocities of the sensory nerve action potential and motor nerve action potential reflect the functional state of axons, and are useful parameters and complement the clinical grading in the assessment of severity of CTS.

AIM: To conduct median nerve sensory and motor conduction studies on patients with carpal tunnel syndrome and correlate the relationship between nerve conduction study parameters and the clinical severity grading.

MATERIALS AND METHODS: Based on clinical assessment, the study patients were divided into 03 groups with mild CTS, moderate CTS and severe CTS respectively as per Mackinnson's classification. Median and ulnar nerve conduction studies were performed on bilateral upper limbs of 50 patients with symptoms of CTS and 50 age and sex matched healthy control subjects. The relationship between the clinical severity grade and various nerve conduction study parameters were correlated.

RESULTS: In this prospective case control study, 50 patients with symptoms consistent with CTS and 50 age and sex matched healthy control subjects were examined over a 10 month period. A total of 30 patients had unilateral CTS (right upper limb in 19 and left upper limb in 11) and 20 patients had bilateral CTS. Female to male ratio was 3.54 to 1. Age ranged from 25 to 81 years. The mean age at presentation was 49.68±11.7 years. Tingling paresthesias of hand and first three fingers were the most frequent symptoms 48 (98%). Tinel's and Phalen's sign were positive in 36 (72%) and 44 (88%) patients respectively. The mean duration of symptoms at presentation was 52.68±99.81 weeks. 16 patients (32%) had mild CTS, 25 (50%) had moderate CTS and 9 (18%) had severe CTS clinically. Prolongation of motor latency, latency difference between median and ulnar amplitudes, motor and sensory nerve conduction velocities, sensory latency between median and ulnar nerves, sensory nerve conduction velocities showed significant changes in comparison with controls. Among them sensory latency difference between median and ulnar nerves and sensory nerve conduction velocities are the most sensitive and specific for diagnosing CTS.

CONCLUSION: In this study, there was a graded deterioration of electrophysiological parameters along with the clinical severity grades, thus reiterating the fact that NCS provide additional, independent objective evidence in the diagnosis and severity assessment of CTS. The sensory conductions were more sensitive than motor conductions in assessing CTS.