Toxic effects of ultrasound in mice: Damage to central and autonomic nervous systems

Abstract

Whole-body exposure of pregnant Swiss-Webster mice to ultrasound at 37°C, 2 MHz, 1 W/cm 2, continuous wave, for periods ranging from 80 to 200 sec resulted in hindleg dysfunction and a distended bladder syndrome; the latter was often associated with flaccid large intestine and compacted fecal material. Dose-response curves indicated damage thresholds at approximately 140 and 120 sec, respectively. Pathological examination confirmed the presence of damage to spinal cord and spinal ganglia as well as to adjacent bone, bone marrow, and dorsal skeletal muscle. The distribution of damage was consistent with a postulated thermal mechanism of preferential absorption and heating of bone, mediating subsequent damage to adjacent tissues. It is suggested that the distended bladder syndrome results from damage to autonomic nervous system, particularly to the pelvic nerve at the point of its emergence from the sacral region of the spinal column. The hindleg dysfunction presumably follows from the lessions in the spinal cord, due to extensive neural necrosis in the thoracosacral region.