A 35 y o male with right side focal seizures.
MRI BRAIN WITH CONTRAST REPORT
Right parietal ~ 20x17mm intra axial lesion with mild peri lesional odema, lesion show thick wall with mild patchy enhancement on post contrast. Restricted diffusion on Dw images. No significant mass effect or mid line shift. On MRS, raised choline, choline / creatinine ratio, markedly reduced NAA, a lactate peak.
Abscess was thought in the differential diagnosis during the discussion with neurosurgeon as there is restricted diffusion. But the pattern of restricted diffusion is not typical of an abscess. In abscess the central necrotic core should show restricted diffusion but here if we see carefully the central core is relatively low signal intensity than the thick wall which show restricted diffusion due to its high cellularity and compact architecture.
Superior sagittal sinus show normal T2 flow voids. No obvious thrombosed right parietal cortical vein or focal bleed on GRE, possibility of CVT ruled out.
So Imaging wise the primary diagnosis given was neoplastic primary, Glioma more likely than Metastasis.
Operated with right posterior parietal craniotomy, complete excision of lesion done. No major intra / extra axial bleed on post operative scans.
And here is...
REPORT OF HISTOPATHOLOGICAL EXAMINATION
Specimen : Excisional biopsy – Right para-saggital SOL.
Gross Appearance : The specimen consists of multiple, irregular pieces of dull grey-tan soft to friable tissue; together measuring 1.0X1.0X0.5 cm. The entire tissue is submitted for processing.
Microscopy : Section shows reactive glial tissue, imperceptibly blending with modestly hypercellular zones of neoplastic astrocytes having hyperchromatic nuclei with irregular chromatin density. The cells have scanty to barely discernible cytoplasm. Few nuclei appears elongated or cigar-shaped with irregular condensed chromatin. The background is uniformly fibrillar with numerous microcystic spaces and variable vascular proliferation. No mitosis nor necrosis is seen. No granulomas seen.
Final Diagnosis : Fibrillary Astrocytoma; Grade 1 to 2 of 4 (as per St. Anne - Mayo grading system).
So take home notes is thinking of an Abscess if restricted diffusion is present on MRI is a good attempt but the pattern of restricted diffusion in the lesion is equally important and can be used in cutting down the list of differential diagnosis.