A positron emission tomography study of cerebral activation associated with essential and writing tremor
A. J. Wills, I. H. Jenkins, P. D. Thompson, L. J. Findley and D. J. Brooks
MRC Cyclotron Unit, Hammersmith Hospital, London, England.
OBJECTIVE: To compare the abnormal patterns of cerebral activation
associated with essential and writing tremors. DESIGN: Positron emission
tomography using oxygen 15-labeled water was utilized to determine regional
cerebral blood flow. Positron emission tomography images that were taken of
the brain in individual patients were coregistered with magnetic resonance
images of the same brain to ascertain accurate localization of cerebral
activation in single patients. Patients with essential tremor underwent
scanning at rest, during involuntary postural tremor, and during passive
wrist oscillation. Normal control subjects underwent scanning at rest and
during voluntary and passive wrist oscillation. Patients with writing
tremor underwent scanning while they were holding a pen to paper with
consequent involuntary tremor and again while they were holding a pen in
the same supinated arm without tremor. SETTING: Research hospital. PATIENTS
OR OTHER PARTICIPANTS: Seven patients with essential tremor, six patients
with writing tremor, and six matched control subjects. INTERVENTIONS: None.
MAIN OUTCOME MEASURES: Regional cerebral blood flow. RESULTS: Essential
tremor was associated with abnormal bilateral cerebellar, red nuclear, and
thalamic activation. Writing tremor was also associated with abnormal
bilateral cerebellar activation. Voluntary wrist oscillation in control
subjects caused only ipsilateral cerebellar activation. These findings were
evident in single patients, when positron emission tomography images were
coregistered with magnetic resonance images and on group analysis of the
pooled positron emission tomography data after transformation into
stereotaxic space. CONCLUSION: These results indicate that both essential
and writing tremors are associated with abnormal bilateral overactivity of
cerebellar connections.