What is the role of MRI in the diagnosis of multiple system atrophy (MSA)?

Updated: Sep 24, 2018
  • Author: Stephen M Bloomfield, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Correlations between MRI and histopathologic findings support the theory that iron deposition, microgliosis, astrocytosis, and severe neuronal loss may contribute to the abnormal hyperintensities. The most reliable findings specific to MSA are putaminal atrophy, hyperintensity in the rim of the putamen, and infratentorial changes. However, these findings are not observed in all patients with MSA. Altered size of the inferior olivary nuclei and putaminal isointensity or hypointensity relative to the globus pallidus are not useful findings. [8, 9, 10]

While the sensitive detection of putaminal iron deposition by T2*-weighted imaging (T2*-WI) is of dianostic value for MSA, the diagnostic significance of the pontine hot-cross bun (HCB) sign remained unknown. Deguchi et al found that T2*-WI is of value for detecting the HCB sign, which might improve the diagnosis of MSA. [11]

Reduced metabolic activity in the putamen and decreased dopaminergic function in the striatonigral system have been demonstrated on positron emission tomography (PET) in patients with the parkinsonian subtype of MSA. However, these findings also are observed in idiopathic PD. Decreased metabolic activity in the cerebellum has been noted in the cerebellar subtype of MSA. PET studies may be useful in the differential diagnosis of MSA, PSP, and CBD. [12]

Routine MRI can be somewhat helpful in distinguishing MSA, PSP, and CBD. Putaminal involvement and vermian cerebellar atrophy are significantly most common in MSA, but cortical atrophy, midbrain atrophy, and third ventricle enlargement are most common in PSP and CBGD. The role of transcranial sonography in the investigation of these disorders is described in Management of Parkinson-Plus Syndromes.


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