The metabolic topography of essential blepharospasm - A focal dystonia with general implications

Objective: To determine the metabolic topography of essential blepharospasm (EB). Background: EB is a cranial dystonia of unknown etiology and anatomi c localization. The authors have used F-18-fluorodeoxyglucose (FDG) and PET with network analysis to identify distinctive patterns of regional metabol ic abnormality associated with idiopathic torsion dystonia (ITD), as well a s sleep induction during PET imaging to suppress involuntary movements, the reby reducing this potential confound in the analysis. Methods: Six patient s with EB and six normal volunteers were scanned with FDG-PET. Scans were p erformed twice: once in wakefulness and once following sleep induction. The authors used statistical parametric mapping to compare glucose metabolism between patients with EB and control subjects in each condition. They also quantified the expression of the previously identified ITD-related metaboli c networks in each subject in both conditions. Results: With active involun tary movements during wakefulness, the EB group exhibited hypermetabolism o f the cerebellum and pens. With movement suppression during sleep, the EB g roup exhibited superior-medial frontal hypometabolism in a region associate d with cortical control of eyelid movement. Network analysis demonstrated a specific metabolic covariance pattern associated with ITD was also express ed in the patients with EB in both the sleep and wake conditions. Conclusio n: These findings suggest that the clinical manifestations of EB are associ ated with abnormal metabolic activity in the pens and cerebellum, whereas t he functional substrate of the disorder may be associated with abnormalitie s in cortical eyelid control regions. Furthermore, ITD-related networks are expressed in patients with EB, suggesting a functional commonality between both forms of primary dystonia.