Cremasteric reflexes of boys with descended, retractile, or undescended testes: An electrophysiological evaluation

Background/Purpose: Retractile testis traditionally has been regarded as su prascrotal location of testis resulting from hyperactivity of the cremaster ic reflex (CR). However, the activity of CR is evaluated poorly in the lite rature. Electrophysiological characteristics of CR in boys with various tes ticular localizations have been evaluated comparatively. Methods: Cremasteric responses that were evoked by electrical stimulation o f the upper-inner aspect of thigh were recorded using a concentric needle e lectromyography (EMG) electrode inserted into the cremaster muscle. Evoked EMGs of groups, each consisting of 10 boys with bilateral descended (DT), u nilateral retractile (RT), or unilateral undescended testes (UT) were compa red for response latencies and durations. Results:Three components with different onset latencies (R1, R2, and R3) we re identified in EMG responses. In patients with UT, the latency of the R1 was shorter than that of the patients with DT, and the duration of R2 was l onger than those of the patients with DT and RT. The differences between pa tients with RT and DT regarding the latency and duration of R1 and R2, alth ough similar to those differences between UT and DT, were not significant. There were no significant differences of the latencies of R3 between groups , in patients with RT and UT, response latency and duration in the descende d and retractive-undescended sides were similar. Conclusions: Defined by shortened latency and prolonged activity of cremast eric responses, which probably reflect a diminished neuronal inhibitory con trol, CR is hyperactive in UT. Dysinhibited motor neurons leading to overac tivity of cremaster muscle might have hampered the descent of testis. Our r esults do not provide a definite support for or against the hypothesis of C R hyperactivity in RT. Copyright (C) 1999 by W.B. Saunders Company.