Thenar eminence quantitative sensory testing in the diagnosis of proximal median nerve compression

Diagnosis of proximal median nerve compression (PMNC) remains a clinical challenge. The authors hypothesized that measurement of the sensibility of the thenar eminence might identify PMNC by demonstrating abnormal function in the palmar cutaneous branch of the median nerve. This hypothesis was evaluated by means of quantitative sensory testing of the thenar eminence in 33 healthy volunteers, 14 patients with carpal tunnel syndrome, and 35 patients with PMNC. The cutaneous pressure thresholds for one-point static touch (1PS) and two-point static touch (2PS) were measured with the Pressure-specified Sensory Device (Sensory Management Services, Baltimore, Maryland). There was no significant difference in thenar eminence sensibility between the healthy volunteers and the patients with carpal tunnel syndrome. In contrast, patients with PMNC had higher cutaneous pressure thresholds for 1PS (p<0.001), 2PS-pressure (p<0.001), and 2PS-distance (p<0.001) than did patients with carpal tunnel syndrome. The p values were less than 0.001 for each of these three comparisons between the healthy volunteers and the patients with PMNC. For the diagnosis of PMNC, quantitative sensory testing of the thenar eminence has a sensitivity of 90.3%, a specificity of 83.3%, and a positive predictive value of 87.5%.