Subacute cerebral infarction - with MR spectroscopy
Sudden onset of dysarthia and disturbed conscious level 5 days ago
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An ill defined cortical and subcortical lesion of altered signal is seen involving the left inferior frontal gyrus centered on pars triangularis (Broca's area). The lesion displays low T1, bright FLAIR signal intensity and mixed signal on DWI/ADC. On post contrast study the lesions shows gyral pattern of enhancement. There is no significant mass effect. MRS reveals mild reduction of NAA and marked elevation of lactate peaks. No significant rise of Cho peak.
Conventional MRI sequences suggest infarction, cerebritis versus low grade glioma. DWI and ADC are not conclusive because the scan was done on the subacute stage when re-perfusion masked diffusion restriction effect. MRS is more conclusive as there is mild reduction of NAA consistent with neuronal damage and marked elevation of lactate indicative of anerobic metabolism. The non rise of Cho peak excludes neoplastic activity.