Nerve conduction studies after treatment for carpal tunnel syndrome.

125 cases of carpal tunnel syndrome confirmed electrophysiologically were the subject of longitudinal nerve conduction studies to assess spontaneous improvement and effect of treatment. 36 cases showed a slowly progressive deterioration which became statistically significant only on lengthy follow-up; analysis of interval tests in these cases revealed that definite improvement or rapid worsening can occur in the interim. The 56 cases studied after local corticosteroid injections showed a statistically significant improvement at one month followed by an overall progressive return to the previous abnormal values in six to 12 months, indicating only slight and temporary alteration in the natural progression of the conduction deficit. The 33 cases which underwent surgical release of the median nerve were shown to have obvious and often rapid improvement, which was sustained for at least one year after surgery.