In imaging median nerve syndromes, ultrasound is useful in examining carpal tunnel syndrome, potentially revealing, in fully developed cases, a triad of: a Gantzer muscle), recognizing pathological muscle signal patterns on MRI can point to the affected nerve. Next to directly visualizing direct causes and anatomical variants (e.g. Ultrasound and MRI are the two imaging modalities that best lend themselves to investigating entrapment syndromes. Synovial hypertrophy in rheumatoid arthritisīifid median nerve due to increased cross-sectional area 14Ī useful mnemonic to remember these causes is MEDIAN TRAP. ganglion cysts, primary nerve sheath tumorsĭeposition of foreign material, e.g. Mechanical overuse (considered the most common association)ĭisease states leading to change of carpal tunnel contents: There is a wide spectrum of causative pathologies, converging on two mechanisms of disease, both of which lead to entrapment 5:Ī decrease in the size of the carpal tunnel caused by such conditions as: Sensory and pain symptoms of the pronator teres syndrome (PTS) and carpal tunnel syndrome can overlap one can distinguish the two by examining for numbness of the forearm, which does not occur in carpal tunnel syndrome and ask about nocturnal exacerbation, which is atypical in PTS. Provocation tests as detailed above can help further. The clinical presentation can harbor some pitfalls. The dominant hand is affected more frequently, and bilateral involvement has been reported to occur in ~30% (range 8-50%) of cases. Hand weakness, as a rule, is a late and often functionally irrelevant symptom 5. Positive Phalen test: paresthesias caused by wrist flexion over 30-60° Positive Tinel test: paresthesias elicited by tapping the median nerve at the wrist Sensory symptoms affect the first three digits and, depending on innervation patterns, the radial aspect of the fourth digit Clinical presentationĬarpal tunnel syndrome is primarily defined by pain and sensory symptoms:īrachialgia paraesthetica nocturna, or nocturnal ascending pain emanating from the wrist, is typical The prevalence of carpal tunnel syndrome is estimated to be 2.7-5.8% of the general adult population, with a lifetime incidence of 10-15%, depending on occupational risk 4.Ĭarpal tunnel syndrome usually occurs between ages 36 and 60 and is more common in women, with a female-to-male ratio of 2-5:1.
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