RED NUCLEAR AND CEREBELLAR BUT NO OLIVARY ACTIVATION-ASSOCIATED WITH ESSENTIAL TREMOR - A POSITRON EMISSION TOMOGRAPHIC STUDY

There has been debate as to whether essential tremor has a central ori gin and over the possible role of the inferior olivary nucleus in its genesis. We used positron emission tomography with radioactive water ( (H2O)-O-15) to detect abnormal patterns of cerebral activity associate d with this condition, at rest, without tremor, and on posture when th e tremor was present. At rest, cerebellar blood flow was significantly increased bilaterally in the group with essential tremor (30-40%) but no increased olivary activity was evident. Essential tremor during ar m extension was associated with further abnormal increases in bilatera l cerebellar and abnormal red nuclear activation. Again, no olivary ov eractivity was evident. Voluntary wrist oscillation in control subject s caused only ipsilateral cerebellar activation. We conclude that esse ntial tremor is associated with abnormal bilateral overactivity of cer ebellar and red nuclear connections but found no evidence of intrinsic overactivity of the inferior olivary nucleus, as evidenced by raised blood flow.