Presentation
Head and generalized tonic-clonic seizures for one week. No neurological deficit. History of chemoradiation for squamous cell carcinoma esophagus one year ago.
Patient Data
An irregular lobulated lesion with hyperdense ring configuration and central hypodensity, measuring roughly 3 x 3 cm, surrounded by vasogenic edema is seen in the right frontal region, which is likely a neoplastic process (primary vs metastatic); another possibility can be an infective process. No hydrocephalus, midline shift, acute infarction, or acute intracranial hemorrhage is seen. No significant abnormality seen in the visualized bones.
FINDINGS: A focal lesion measuring about 3 x 3 cm with surrounding marked vasogenic edema is seen in the right frontal lobe. Mild mass effect is seen over the frontal horn of the right lateral ventricle. The lesion has irregular lobulated outlines with vividly enhancing walls and a central cystic non-enhancing matrix. On DWI, the lesion shows central diffusion restriction and on long TR MRS, the lesion displays high lipid/lactate peaks with reduced choline/creatine and NAA peaks. No other intra or extra-axial lesion is noted.
CONCLUSION: The above described MRI and MRS features are slightly more in favor of brain abscess; however, considering the current clinical context; prime differential diagnosis would be necrotic brain metastasis.
Status post right frontoparietal craniotomy. Post-surgical changes are seen in the underlying brain parenchyma. The lesion has likely been partially resected/biopsied.
Case Discussion
Procedure: Craniotomy and resection of the right frontal lobe space-occupying lesion.
Diagnosis: Metastatic squamous cell carcinoma, compatible with the known esophageal primary.
Diffusion-weighted imaging (DWI) is being used in the evaluation of cystic cerebral neoplasms; these neoplasms are of low signal intensity on the DWI sequence and of high signal intensity on the ADC sequence. However, high signal on the DWI sequence and low signal on the ADC sequence, mimicking restricted diffusion of an abscess (like this case), has been reported in ring-enhancing metastases of adenocarcinoma & squamous cell carcinoma, radiation necrosis, and high-grade gliomas. Therefore, diffusion-weighted imaging should be carefully interpreted, and correlated with the clinical history of the patient and other additional imaging findings if present.
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