Carpal tunnel syndrome is the most common compressive neuropathy in the upper limb with a prevalence of 3–5% in the general population and a cost exceeding $500 million annually in the USA.1 ,2 It significantly impacts upon quality of life, and especially on a person's ability to do manual labour or any task involving repetitive wrist movement.

The diagnosis of carpal tunnel syndrome is currently clinical and through an electrodiagnostic evaluation that includes nerve conduction studies and needle electromyography.2 Nerve conduction measurements include peak latencies, conduction velocities and amplitudes of motor, sensory and mixed nerve responses, providing information as to the likely localisation and severity of a median neuropathy. In particular, comparing median with ulnar mixed nerve palmar responses is highly sensitive, as these fibres are affected early.3 The addition of needle electromyography helps to assess for cervical radiculopathy, proximal median neuropathy or polyneuropathy, as well as identifying axonal loss; it helps especially if the presenting symptoms are atypical. Identifying axonal loss influences clinical management as it suggests the need to bypass conservative therapy and proceed to surgical release. The disadvantages of electrodiagnostic studies are their cost, the inability to assess the surrounding anatomy and patient discomfort.2 While such studies are largely considered as the gold standard for diagnosing carpal tunnel syndrome, they can be …