FDG- and Dopa-PET in postencephalitic parkinsonism

We report a case of a 74-year old woman who following an acute virus enceph alitis developed an akinetic-rigid Parkinson syndrome with tremor, hypokine sia, hypomimia, rigidity and cogwheel phenomenon in all four extremities, b rady-dysdiadochokinesia as well as myoclonic jerks of the arms. Many of the clinical features of this postencephalitic parkinsonism (PEP) suggested th e diagnosis of sporadic encephalitis lethargica, first described by von Eco nomo 1917. Cerebral spinal fluid showed signs of a viral. encephalitis, and a positive influenza A IgA-antibody titer (1:>160) in the viral serologic screen was found. Positron emission tomography (PET) showed an altered patt ern of glucose- and dopa-metabolism clearly different from findings in idio pathic Parkinson syndrome (IPS). The acute lack of inhibitory input from th e substantia nigra pars compacta to the striatum could explain the differen t metabolic patterns in our case in comparison to IFS patients. Our finding s indicate that PEP may also be caused by influenza A and furthermore that PET clearly distinguishes PEP from IPS.