Cerebral glucose metabolism in oculopalatal tremor

No study adopted the statistical parametric mapping (SPM) analyses of (18)F-fluorodeoxy glucose (FDG) PET in a large number of patients with oculopalatal tremor (OPT). To determine regional cerebral glucose metabolism in patients with OPT, nine patients with OPT underwent FDG-PET of the brain. Their glucose metabolism was compared with that of 50 normal controls (NC) by using SPM analyses. Three patients had bilateral and six showed unilateral pseudohypertrophic degeneration of the inferior olivary nucleus (ION) on MRI. Compared with NC, OPT patients did not show any metabolic derangement in the anterolateral medulla where the pseudohypertrophic ION locates. Instead, six patients with unilateral ION changes had hypometabolism in ipsilesional pontine tegmentum and hypermetabolism in contralesional thalamus. Their metabolic changes did not depend on the lateralization of ION changes. Our study failed to present any metabolic evidence for the role of ION in the generation of OPT. In part, the failure might originate from the different pathomechanism between OPT and pure palatal tremor or sensitivity/specificity issues of PET and SPM analyses. But, our results suggest that impaired cell groups of the paramedian tract and thalamic tremor cells may contribute to the generation of OPT.