Presentation
Syncopal episode 5 days ago, no known history of malignancy
Patient Data
1) Intra-axial, ring enhancing mass with areas of nodular thickening located at the grey-white matter junction of the right frontal lobe. T2 hyper- and central T1 hypointense signal suggests the presence of necrosis. Ring enhacing component shows low ADC values, whereas centrally facilitated diffusion is seen. No adjacent cortical thickening, no surrounding edema present.
2) Moderate T2 hyperintensity and thickening of the left hippocampus with restricted diffusion and gyral enhancement of the hippocampial head.
4 months followup (comparison)
Significant atrophy of the left hippocampal head (second image) in comparison to the initial study (first image).
Case Discussion
1) With the suspicion of brain metastasis the patient underwent further checkup. Lung infilitration were found on chest CT which proved to be small cell lung cancer.
2) Taking into consideration the new finding of small cell of lung cancer, autoimmune (limbic) encephalitis is included in the imaging differential diagnosis.
There are specific criteria that must be met for the diagnosis of possible autoimmune encephalitis such as memory deficits, altered mental status or psychiatric syptoms, CSF pleocytosis and MRI findings suggestive of encephalitis.
These criteria were not met in this patient.
Furthermore the unilateral hippocampal head involvement with gyral enhancement and low ADC values favor the case of infarction in the subacute phase.
Patient underwent radio- and chemotherapy. The 4 months followup MRI shows significant atrophy of the affected left hippocampal head, supporting the diagnosis of infarction.
Hippocampal blood is suplied by branches of posterior cerebral artery and anterior choroidal artery, but can frequently vary.