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Multiple System Atrophy: Phenotypic spectrum approach coupled with brain 18-FDG PET
Stephan Grimaldi1, Mohamed Boucekine2, Tatiana Witjas3
1Aix-Marseille Univ, APHM, CHU Timone, Department of Neurology and Movement Disorders, 13385, Marseille Cedex 05, France.
Objective:
The 2008 diagnostic criteria classify Multiple System Atrophy (MSA) patients in a predominantly parkinsonian (MSA-P) or cerebellar (MSA-C) type. Phenotypic descriptions have since highlighted a clinical heterogeneity among patients (e.g., mixed-type, cognitive impairment, atypical longer survival). This study attempts to identify different phenotypes of patients with MSA and to describe corresponding brain 18-FDG Positron Emission Tomography (PET) patterns.
Methods:
Patients with a "probable" MSA diagnosis for whom a brain 18-FDG PET was performed were included. A retrospective analysis (from 2006 to 2017) was conducted using standardized data collection. We used Latent Class Analysis (LCA), an innovative statistical approach, to identify profiles of patients based on common clinical characteristics. Brain metabolism of different groups was studied at rest.
Results:
Eighty-five patients were included. Three different profiles were revealed (entropy = 0.835): 1. extrapyramidal, axial, laryngeal-pharyngeal involvement (LPI) and cerebellar symptoms (n = 46, 54.1%); 2. cerebellar and LPI symptoms (n = 30, 35.3%); 3. cerebellar and cognitive symptoms (n = 9, 10.6%). Brain metabolism analyses (k > 89; p < 0.001) showed hypometabolism of the basal ganglia, frontal/prefrontal, temporal cortices and left posterior cerebellum in profile 1. In profile 2 there was hypometabolism of the medulla, prefrontal, temporal, cingular cortices, putamen and bilateral cerebellar hemispheres. In profile 3 there was hypometabolism of bilateral posterior cerebellar hemispheres and vermis.
Conclusion:
Beyond the two most common phenotypes of MSA, a third and particularly atypical profile with cerebellar and cognitive symptoms but without LPI involvement is described. These profiles are supported by different brain metabolic abnormalities which could be useful for diagnostic purposes.
Insights
This study identified three distinct patient profiles for Multiple System Atrophy (MSA), including an atypical cerebellar and cognitive type. These distinct phenotypes correlate with specific brain metabolism patterns seen on 18-FDG PET scans, aiding in diagnosis.
Area of Science:
- Neurology
- Neuroimaging
- Metabolic Brain Imaging
Background:
- The 2008 diagnostic criteria for Multiple System Atrophy (MSA) define predominantly parkinsonian (MSA-P) and cerebellar (MSA-C) types.
- Clinical heterogeneity in MSA patients, including mixed-type, cognitive impairment, and atypical survival, necessitates refined classification.
- Brain 18-FDG Positron Emission Tomography (PET) can reveal metabolic patterns associated with neurological disorders.
Purpose of the Study:
- To identify distinct patient phenotypes within Multiple System Atrophy (MSA).
- To correlate identified MSA phenotypes with specific brain 18-FDG PET metabolic patterns.
- To explore the utility of these findings for diagnostic purposes in MSA.
Main Methods:
- Retrospective analysis of 85 patients with a "probable" MSA diagnosis and available 18-FDG PET scans (2006-2017).
- Latent Class Analysis (LCA) was employed to identify patient profiles based on clinical characteristics.
- Brain metabolism was assessed at rest using 18-FDG PET to analyze metabolic differences between identified profiles.
Main Results:
- Three distinct MSA patient profiles were identified: Profile 1 (54.1%) with extrapyramidal, axial, laryngeal-pharyngeal involvement (LPI), and cerebellar symptoms; Profile 2 (35.3%) with cerebellar and LPI symptoms; and Profile 3 (10.6%) with cerebellar and cognitive symptoms.
- Profile 1 showed hypometabolism in basal ganglia, frontal/prefrontal, temporal cortices, and left posterior cerebellum.
- Profile 2 exhibited hypometabolism in the medulla, prefrontal, temporal, cingular cortices, putamen, and bilateral cerebellar hemispheres.
- Profile 3 demonstrated hypometabolism in bilateral posterior cerebellar hemispheres and vermis.
Conclusions:
- A third atypical MSA profile characterized by cerebellar and cognitive symptoms without LPI involvement was identified.
- These distinct MSA phenotypes are associated with specific brain metabolic abnormalities.
- The identified metabolic patterns may serve as valuable biomarkers for MSA diagnosis.
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