Neurobiological effects of extensive transcranial electromagnetic stimulation in an animal model

The effects of transcranial electromagnetic stimulation (TEMS) on the cellular morphology of the cortex, cerebellum, and brain-stem were systematically investigated in rabbits exposed to 1000 pulsed stimuli at 100% maximum stimulation level (2.0 Tesla at the skull) over a 12 month period with a 5 cm circular magnetic coil positioned over the cranium. Also, the acute effects of TEMS on heart rate and respiration were examined. (1) T1 and T2 weighted magnetic resonance images (MRI) of 1-3 mm sections in both sagittal and axial planes revealed no evidence of gross morphological changes or subtler tissue damage to the cerebrum, cerebellum, or brain-stem. (2) Light microscopic examination of 60 microns hematoxylin-eosin/Cresyl Violet Luxol Fast Blue stained sections of the brain-stem, cerebellum, and cerebral cortex showed no TEMS-related changes in cellular organization or histological damage. (3) Autonomic activity as reflected by heart rate was also unaffected by high intensity TEMS. Normal heart rate was maintained during repeated TEMS at 100% of maximum. (4) Respiration rate was briefly altered at the time of the stimulus, but returned to normal immediately after the stimulus. These findings in experimental animals revealed no biohazardous effects on the brain following extensive exposure to high intensity, low frequency time-varying magnetic field stimulation from the coil of a clinical instrument.