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Multiple system atrophy: natural history, MRI morphology, and dopamine receptor imaging with 123IBZM-SPECT
J B Schulz1, T Klockgether, D Petersen
1Department of Neurology, University of Tübingen, Federal Republic of Germany.
Abstract:
Sixteen patients with a clinical diagnosis of probable multiple system atrophy (MSA) were examined clinically by MRI and by 123I-iodobenzamide single photon emission computed tomography (IBZM-SPECT). The clinical records of another 16 patients were also analysed retrospectively. On the basis of their clinical presentation, patients were subdivided into those with prominent parkinsonism (MSA-P, n = 11) and those with prominent cerebellar ataxia (MSA-C, n = 21). Autonomic symptoms were present in all patients and preceded the onset of motor symptoms in 63% of patients. Calculated median lifetime and the median time to become wheelchair bound after onset of disease were significantly shorter for MSA-P than for MSA-C (lifetime: 4.0 v 9.1 years; wheelchair: 3.1 vs 5.0 years) suggesting a better prognosis for cerebellar patients. A significant loss of striatal dopamine receptors (below 2 SD threshold) was detected by IBZM-SPECT in 63% of the patients (56% below 2.5 SD threshold). There was no difference between patients with MSA-C and those with MSA-P in the proportion with significant receptor loss and the extent of dopamine receptor loss. Planimetric MRI evaluation showed cerebellar and brainstem atrophy in both groups. Atrophy was more pronounced in patients with MSA-C than in those with MSA-P. Pontocerebellar hyperintensities and putaminal hypointensities on T2 weighted MRI were found in both groups. Pontocerebellar signal abnormalities were more pronounced in MSA-C than in MSA-P, whereas the rating scores for area but not for intensity of putaminal abnormalities were higher in MSA-P. MRI and IBZM-SPECT provide in vivo evidence for combined basal ganglia and pontocerebellar involvement in almost all patients in this series.
Insights
Multiple System Atrophy (MSA) patients show combined basal ganglia and pontocerebellar involvement. While cerebellar subtypes (MSA-C) have a better prognosis, parkinsonian subtypes (MSA-P) exhibit more severe atrophy and faster disease progression.
Area of Science:
- Neurology
- Neuroimaging
- Neurodegenerative Diseases
Background:
- Multiple System Atrophy (MSA) is a progressive neurodegenerative disorder.
- Clinical presentation varies, often classified as MSA with prominent parkinsonism (MSA-P) or cerebellar ataxia (MSA-C).
- Understanding the in vivo pathological correlates is crucial for diagnosis and prognosis.
Purpose of the Study:
- To investigate the in vivo involvement of basal ganglia and pontocerebellar structures in patients with probable MSA using MRI and IBZM-SPECT.
- To correlate imaging findings with clinical subtypes (MSA-P vs. MSA-C) and disease progression.
Main Methods:
- Clinical assessment and retrospective chart review of 32 probable MSA patients.
- Magnetic Resonance Imaging (MRI) for evaluating brainstem, cerebellar, and putaminal abnormalities.
- 123I-iodobenzamide (IBZM)-SPECT to assess striatal dopamine receptor binding.
Main Results:
- Autonomic symptoms preceded motor symptoms in 63% of patients.
- MSA-P patients had a significantly shorter median lifetime and time to wheelchair dependency compared to MSA-C patients.
- Both MRI and IBZM-SPECT revealed combined basal ganglia and pontocerebellar involvement in most patients, with distinct patterns of atrophy and signal abnormalities between MSA-P and MSA-C.
Conclusions:
- MRI and IBZM-SPECT provide in vivo evidence for widespread neurodegeneration in MSA.
- Clinical subtypes of MSA (MSA-P and MSA-C) show differential patterns of brain atrophy and signal abnormalities.
- Prognosis appears to be better for MSA-C patients compared to MSA-P patients.