SPECT perfusion patterns distinguish psychogenic from essential tremor

Background: Psychogenic movement disorders pose formidable challenges to diagnosis and treatment reflecting our limited understanding of the basic brain mechanisms that cause them. Recently, functional brain imaging has been utilized to study psychogenic movement disorders. Objectives: To identify characteristic patterns of cerebral perfusion distinguishing psychogenic tremor (PT) from essential tremor (ET). Methods: We studied five patients each with PT, ET and normal controls. SPECT imaging was performed at rest and during a tremor-inducing motor task. Results: In ET, rest imaging revealed increased rCBF (relative cerebral blood flow) in cerebellar hemispheres and left inferior frontal gyrus. During the motor task, ET patients demonstrated increased rCBF in the supplementary motor area (SMA) and contralateral motor cortex and reduced rCBF in the cerebellum and visual cortex. In contrast, PT images at rest revealed increased rCBF in left inferior frontal gyrus and left insula. Motor task imaging revealed increased rCBF in the cerebellum and reduced rCBF in anterior regions of the default mode network. Conclusions: Our study revealed distinct patterns of cerebral perfusion during rest and motor task that distinguish PT from ET. Deactivation of the default mode network may serve as a marker for psychogenic movement disorders.