Brain abscess and ventriculitis
Headache and fever with left sided weakness. History of malignant scalp lesion with craniectomy and radiotherapy since a year.
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- Status post-operative with right temporo-occipital craniectomy with associated mild meningeal enhancement.
- A right temporo-occipital marginally enhancing cystic lesion is seen. The lesion shows mildly hypeointense T1 and bright T2 signal intensity with T2 hypointense margin. The lesion shows evident restricted diffusion with high DWI and low ADC as well as high exponential ADC signals. The lesion measures 7 X 3 X 4 cm in its main AP, TS and CC diameters respectively.
- The lesion is seen surrounded by moderate vasogenic brain edema with compression of the right lateral ventricle as well as mild contra-lateral midline shift and mild compression of the 3rd ventricle with slight dilatation of the lateral ventricles with mild peri-ventricular transependymal retro-grade CSF permeation. The lesion is seen indenting the right thalamus, basal ganglia and effacing the right perimesencephalic cistern with indentation of right crus cerebri.
- MR spectroscopy shows:
- Significant elevation of the lipid/lactate doublets.
- Marked depression and almost nullification of the neuronal markers; N-acetyl aspartate (NAA) and creatine (Cr) as well as the choline (Cho).
- Elevation of the myoinositol (MI) with increased MI/Cr ratio.
- Associated right lateral ventriculitis with restricted diffusion and marginal enhancement of the occipital horn, trigone and temporal horn of the right lateral ventricle
Right temporo-occipital marginally enhancing lesion; consistent with brain abscess with associated right lateral ventriculitis and right temporo-occipital meningitis as well as mild supra-tentorial hydrocephalic changes with interstitial CSF permeation and mass effect.
The differential diagnosis of marginally enhancing lesion is mainly abscess, cystic glioma and cystic metastatic deposit. The restricted diffusion on DWI and MR spectroscopy criteria are diagnostic of brain abscess and fairly exclude other possibilities.
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