Page "Carpal tunnel syndrome" Paragraph 35

Other conditions may also be misdiagnosed as carpal tunnel syndrome.

Thus, if history and physical examination suggest CTS, patients will sometimes be tested electrodiagnostically with nerve conduction studies and electromyography.

The goal of electrodiagnostic testing is to compare the speed of conduction in the median nerve with conduction in other nerves supplying the hand.

When the median nerve is compressed, as in CTS, it will conduct more slowly than normal and more slowly than other nerves.

There are many electrodiagnostic tests used to make a diagnosis of CTS, but the most sensitive, specific, and reliable test is the Combined Sensory Index ( also known as Robinson index ).

Electrodiagnosis rests upon demonstrating impaired median nerve conduction across the carpal tunnel in context of normal conduction elsewhere.

Compression results in damage to the myelin sheath and manifests as delayed latencies and slowed conduction velocities However, normal electrodiagnostic studies do not preclude the presence of carpal tunnel syndrome, as a threshold of nerve injury must be reached before study results become abnormal and cut-off values for abnormality are variable.

Carpal tunnel syndrome with normal electrodiagnostic tests is very, very mild at worst.