Presentation
Brought to the ED after a 3-hour episode of impaired awareness, left upper extremity tightness and stuttering.
Patient Data
Crescentic fluid density collection along the right temporal pole in line with an arachnoid cyst. No other abnormalities are visible on the initial non-contrast head CT.
A “bubbly“ or nodular lesion is visible in the posterior right temporal lobe. The lesion is hyperintense on T2-weighted and FLAIR sequences, mainly affecting the deep cortical ribbon and subcortical white matter. It is isointense to surrounding grey and white matter on T1-weighted sequences and does not enhance with contrast.
Incidental crescentic fluid collection along the temporal pole likely represents an arachnoid cyst.
Case Discussion
Given the patient's clinical presentation and findings on imaging, the most likely diagnosis is a multinodular and vacuolating neuronal tumor (MVNT).
MVNTs are a type of benign neuronal brain tumor with specific histopathological and radiologic findings 1. They are included within the category of glioneuronal and neuronal tumors in the WHO classification of central nervous system tumors (5th Edition) 2.
These lesions have typically been detected in patients with non-focal headaches and seizures, both present in this patient, though have more often been observed as incidental findings in patients without these symptoms 1. On imaging, these lesions have almost exclusively appeared as small clusters of nodules in the juxtacortical or subcortical white matter, with normal-appearing cortex 3. These lesions are typically hyperintense on T2-weighed and FLAIR imaging 4.
Management:
Case series with patient follow-up over time have not seen lesion progression or worsening of symptoms, which has led to the recommendation against a biopsy or lesion resection; MRI surveillance is generally sufficient 1. Excision can be recommended if the lesion is considered causative of a seizure disorder 3.
This case was submitted with supervision and input from:
Matt McCann, M.D.
Mayo Clinic, Jacksonville
Department of Diagnostic and Interventional Radiology
Resident Radiologist