EFFECTS OF BODY AND HEAD POSITIONS ON BILATERAL DIFFERENCE IN TYMPANIC TEMPERATURES

We have examined the nonparallel changes in tampanic membrane temperat ures (T(ty)) from the two ears in response to various changes in body and head positions. Upon assuming a lateral recumbent position, the T( ty) on the lower side increased while that on the upper side decreased . Pressure application over a wide area of the lateral chest only caus ed inconsistent and obscure asymmetric changes in T(ty). A lateral fle xion of the head with the subject sitting upright and a rotation of th e head to the side in a supine position induced an increase in the T(t y) on the lower side compared to that on the upper side. The temperatu re and blood flow of the forehead often decreased on the lower side an d increased on the upper side, although such responses were not always concomitant with the asymmetric changes in T(Ty). A dorsal flexion of the head with the subject in a reclining position caused a slight inc rease in the T(ty), whereas raising the head upright induced a slight decrease in them. Two additional experiments were carried out with sin gle photon emission computed tomography using Tc-99m-hexamethylpropyle neamine oxime as tracer, and a slight, relative decrease in counts was noted in the right hemisphere during rotation of the head to the righ t. These results would strongly suggest that unilateral increases and decreases in T(ty) could have been caused by one-sided decreases and i ncreases, respectively, in blood flow to the brain and/or the tympanic membrane, induced by a vasomotor reflex involving vestibular stimulat ion.