Effect of metabolic syndrome on the outcome of corticosteroid injection for carpal tunnel syndrome

Diffuse peripheral nerve impairment is common in metabolic syndrome: in patients with metabolic syndrome and carpal tunnel syndrome this might affect the outcome of treatment by local corticosteroid injection. A total of 55 consecutive patients with carpal tunnel syndrome and metabolic syndrome treated with corticosteroid injection (10 mg triamcinolone acetonide) were age and sex matched with 55 control patients without metabolic syndrome. Grip strength, perception of touch with Semmes-Weinstein monofilaments and Boston Carpal Tunnel Questionnaires were assessed at the baseline and at 6, 12 and 24 weeks follow-up. The two groups had similar pre-operative grip strength and Boston Carpal Tunnel Questionnaire scores. The Boston Carpal Tunnel Questionnaire symptom and function scores of the metabolic syndrome group were significantly greater than the control group at 12 and 24 weeks follow-up. Except for significantly greater grip strength at the 12-week follow-up in the control group, there were no significant differences in grip strength between the groups. Semmes-Weinstein monofilament sensory index for the control group was significantly greater than that of the metabolic syndrome group throughout the 24-week follow-up. After 24 weeks, five patients (13%) in the control group and 13 patients (27%) in the metabolic syndrome group had had carpal tunnel surgery. Patients with metabolic syndrome are at risk for poor functional outcome and failure of treatment after corticosteroid injection for carpal tunnel syndrome.