Cerebral glucose metabolism in Fisher syndrome

Background: Fisher syndrome (FS) is characterised by a triad of ophthalmoplegia, ataxia and areflexia. The lesion sites responsible for ataxia and ophthalmoplegia in FS require further exploration. The aim of this study was to determine the involvement of the central nervous system in FS using F-18-fluorodeoxyglucose-positron emission tomography (FDG-PET). Methods: Cerebral glucose metabolism in 10 patients with FS was compared with that of 60 age and sex matched normal controls using PET. For individual analyses, 15 age and sex matched controls were selected from the control group. Patients also underwent MRI of the brain and measurement of serum anti-GQ1b antibody. Results: Group analyses revealed increased metabolism in the cerebellar vermis and hemispheres, pontine tegmentum, midbrain tectum, left thalamus and right inferior frontal cortex (p < 0.001, uncorrected). In contrast, the visual association cortices (Brodmann areas 18 and 19) showed decreased metabolism bilaterally. Individual analyses disclosed hypermetabolism in the cerebellar vermis or hemispheres (n = 7), inferior frontal cortex (n = 5) and brainstem (n = 4, p < 0.005, uncorrected). A negative correlation between the cerebellar hypermetabolism and the interval from symptom onset to PET (r = 20.745, p = 0.013) was also found. Hypermetabolism was normalised on follow-up PET with an improvement in ophthalmoplegia and ataxia in one patient. Conclusions: These findings indicate involvement of the central nervous system in FS, and the hypermetabolism in the cerebellum and brainstem suggests an antibody associated acute inflammatory process as a mechanism of this autoimmune disorder.