Frontotemporal and striatal SPECT abnormalities in myoclonus-dystonia: phenotypic and pathogenetic considerations.

BACKGROUND AND PURPOSE: Myoclonus-dystonia (MD) is a rare movement disorder characterized by myoclonic jerks, dystonia and a variety of psychiatric symptoms. Neuroimaging and electrophysiologic studies have not been able to detect any specific central nervous system abnormality. We report for the first time a well-characterized case with MD and abnormal brain perfusion imaging using single photon emission computed tomography (SPECT) with (99m)Tc-ethyl cysteinate dimer (ECD). A review of the literature on the phenotypic and pathogenetic considerations for MD is also presented. METHODS: To better define the functional regional central nervous system involvement in MD, we conducted a brain perfusion SPECT with (99m)Tc-ECD in a patient diagnosed with typical disease. RESULTS: Analysis of the SPECT data revealed significantly reduced regional cerebral blood flow (rCBF) in both temporal lobes (left > right and medial > lateral). Reduced rCBF was also observed in both frontal lobes and the right caudate nucleus. CONCLUSIONS: Our findings of reduced frontotemporal and striatal rCBF in the absence of other neuroimaging and electrophysiologic findings correlate well with the clinical manifestations in our patient and suggest possible functional/metabolic involvement of these areas in the etiopathogenesis of MD.

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.

The metabolic topography of posthypoxic myoclonus.

Posthypoxic myoclonus (PHM) is a syndrome of action and intention myoclonus that occurs in some patients who survive a cardiac arrest. Using PET and statistical parametric mapping, the authors observed a significant bilateral increase in glucose metabolism in the ventrolateral thalamus and pontine tegmentum in patients relative to controls. Interventions such as deep brain stimulation that interrupt networks that involve these structures may be useful in patients with severe PHM.