Brain glucose metabolism in neuropathologically confirmed multiple system atrophy

Abstract

The second consensus statement on the diagnosis of multiple system atrophy (MSA) [1] suggests clinical diagnostic criteria for the assessment of the disease with predominantly parkinsonian features (MSA-P) or cerebellar ataxia (MSA-C). Hypometabolism on [F]fluorodeoxyglucose positron emission tomography (FDG-PET) in the putamen, the brainstem or the cerebellum was listed as an additional feature supporting the diagnosis of MSA-P, whereas hypometabolism in the putamen and presynaptic nigrostriatal dopaminergic denervation on single-photon emission computed tomography (SPECT) or PET were considered as supporting features for MSA-C [2]. The recommendations were based on clinical imaging studies involving patients with probable/possible MSA-P and MSA-C without autopsy confirmation of the diagnoses [1]. Although there are reported studies of decreased striatal dopamine transporter binding with [I]FP-CIT SPECT (CIT-SPECT) in autopsy-confirmed cases of MSA [4], there are no reported cases of ante mortem FDG-PET with post mortem confirmation of the diagnosis. Here we report a patient with neuropathologically confirmed MSA examined with both FDG-PET and CITSPECT during the course of the disease. A 50-year-old man was referred to a neurologist in 2008 due to general fatigue, weakness in the lower extremities, difficulties in turning in bed and severe urinary incontinence that had lasted for 2 years. Family history was unremarkable. Clinical examination showed mild rigidity in the right upper extremity and right-sided dysdiadochokinesia, mild general bradykinesia, mild hypomimia and hyperreflexia in the right lower extremity. Brain magnetic resonance imaging (MRI) showed a slightly decreased T2 signal bilaterally in the dorsolateral putamen, but no atrophy or other pathology of olivopontocerebellar structures was found, such as pontine hot cross bun sign. Levodopa was initiated without a clear treatment response. One year later, the clinical examination showed additional features of dysarthria, axial dystonia and severe postural instability. The levodopa dose was increased to 600 mg/day with modest subjective benefit for rigidity. Brain CIT-SPECT and FDG-PET were performed in 2009 approximately 3 years after the first symptoms appeared. CIT-SPECT showed clearly reduced binding in the striatum (region-tooccipital ratio in the left caudate nucleus, the left putamen and the right putamen = 1.1, region-to-occipital ratio in the right caudate nucleus = 1.4). FDG-PET imaging with an ECAT HRRT high-resolution scanner (Siemens Medical Solutions) (frame of 25 min) was performed 55 min after injection of FDG (injected dose 328 MBq). Visual examination showed clear bilateral reductions in putamen and V. Kaasinen (&) Division of Clinical Neurosciences, University of Turku and Turku University Hospital, POB 52, 20521 Turku, Finland e-mail: valtteri.kaasinen@tyks.fi