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 the Robinson index). Electrodiagnosis rests upon demonstrating impaired median nerve conduction across the carpal tunnel in context of normal conduction elsewhere. It is often stated that normal electrodiagnostic studies do not preclude the diagnosis of carpal tunnel syndrome. The rational for this is that a threshold of neuropathy must be reached before study results become abnormal and also that threshold values for abnormality vary. Others contend that idiopathic median neuropathy at the carpal tunnel with normal electrodiagnostic tests would represent very, very mild neuropathy that would be best managed as a normal median nerve. Even more important, notable symptoms with mild disease is strongly associated with unhelpful thoughts and symptoms of worry and despair. Notable CTS with unmeasurable IMNCT should remind clinicians to always consider the whole person, including their mindset and circumstances, in strategies to help people get and stay healthy. Imaging
The role of MRI or ultrasound imaging in the diagnosis of idiopathic median neuropathy at the carpal tunnel (IMNCT) is unclear. Their routine use is not recommended. MRI has high sensitivity but low specificity for IMNCT. High signal intensity may suggest accumulation of axonal transportation, myelin sheath degeneration or oedema. Differential diagnosis
There are few disorders on the differential diagnosis for carpal tunnel syndrome. Cervical radiculopathy can also cause paresthesia abnormal sensibility in the hands and wrist.
There is notable variation in such estimates based on how one defines the problem, in particular whether one studies people presenting with symptoms vs. measurable median neuropathy (IMNCT) whether or not people are seeking care. It accounts for about 90% of all nerve compression syndromes. The best data regarding IMNCT and CTS comes from population-based studies, which demonstrate no relationship to gender, and increasing prevalence (accumulation) with age. Symptoms
The characteristic symptom of CTS is numbness, tingling, or burning sensations in the thumb, index, middle, and radial half of the ring finger. These areas process sensation through the median nerve. Numbness or tingling is usually worse with sleep. People tend to sleep with their wrists flexed, which increases pressure on the nerve. Ache and discomfort may be reported in the forearm or even the upper arm, but its relationship to IMNCT is uncertain. Symptoms that are not characteristic of CTS include pain in the wrists or hands, loss of grip strength, minor loss of sleep, and loss of manual dexterity.Median nerve symptoms may arise from compression at the level of the thoracic outlet or the area where the median nerve passes between the two heads of the pronator teres in the forearm, although this is debated. Signs
Severe IMNCT is associated with measurable loss of sensibility. Diminished threshold sensibility (the ability to distinguish different amounts of pressure) can be measured using Semmes-Weinstein monofilament testing.