Abstracts

Rationale: Multinodular and vacuolating neuronal tumors (MVNT) of the cerebrum were first described in 2013.1 These nodular lesions behave in a benign fashion and were added in 2016 to the World Health Organization (WHO) Classification of CNS neoplasms as a grade I entity. MVNT are located on the inner surface of otherwise normal cortex and appear hyperintense on MRI FLAIR and T2 weighted sequences.2 Microscopically, cells range from morphologically ambiguous to clearly recognized neurons. Whether these lesions represent a benign tumor or dysplastic early neuronal phenotype remains unclear.4 MNVT may be found in the frontal, temporal, parietal, or occipital lobes. Also, MNVT can be associated with seizures. The clinical and radiographic natural history, and EEG findings associated with this type of lesion remain only partially described. Since the temporal lobes are the most common location for focal seizures, further understanding of temporal lobe MNVT is of importance to the epilepsy community. Methods: This is a retrospective case series on 3 patients with temporal lobe MVNT. Presentation and clinical course, as well as, EEG and MRI findings are reported for all 3 cases. One patient underwent surgical resection and pathology findings are discussed. Results: Case 1: 36-year-old female who presented with deja vu that began after a motor vehicle accident at age 19 years. She is also followed by psychiatry for anxiety and OCD traits. Routine EEG at age 31 years was normal. In-patient video EEG demonstrated no EEG changes during aura and no other seizures or clear interictal discharges. The patient reported symptomatic improvement of auras with lamotrigine. MRI of the brain demonstrated a multicystic lesion with bubbly appearance involving the left mesial temporal lobe in the region of the left amygdala with no associated enhancement. The left mesial temporal lesion has been stable according to serial MRI imaging over the last 17 years. Case 2: 50-year-old male who presented with nocturnal bilateral convulsive seizures at age 48 years. This patient also suffers from anxiety and panic attacks provoked by stress. In-patient video EEG monitoring demonstrated right temporal sharp wave and spike wave discharges. He has been seizure-free for 1 year and 10 months on lamotrigine monotherapy. MRI of the brain demonstrated a cystic lesion along the right mesial temporal lobe with no associated enhancement. The lesion has been stable over 2 years with serial imaging. Case 3: 34-year-old female who presented with seizures beginning 1.5 weeks after a head injury at age 22 years. Seizures had mixed features of focal convulsive seizures and psychogenic seizures. Clinical features included left eyelid drooping and right eye twitching followed by loss of awareness, fists clench, jerking of the head to the left, jerking of the left more than right side of the body, and urinary incontinence. Repeated in-patient video EEG monitoring at age 28 years, 31 years, and 33 years failed to capture a seizure or clearly epileptiform interictal discharges. Seizures were not controlled with trials of oxcarbazepine, levetiracetam, topiramate, or lamotrigine. She has rare breakthrough seizures on zonisamide. MRI of the brain demonstrated foci of abnormal increased T2 signal involving the subcortical white matter of the posterior right middle temporal gyrus with bubbly appearance and no associated enhancement. The lesion has appeared stable over 11 years of serial imaging. However, due to mention of possible dysembryoplastic neuroepithelial tumor in the differential, the patient underwent surgical resection of the lesion. Pathology results included cortex and white matter nodules composed of medium-sized neuronal cells with abundant amphophophilic cytoplasm, round nuclei and prominent nucleoli. Reactive gliosis around these nodules was highlighted by the GFAP immunostain. The neuronal elements were positive for synaptophysin, and negative for chromogranin and NeuN immunostains. The patient continues to have rare postoperative seizures or nonepileptic events. Conclusions: As there are only a few reported case series on MVNT, our goal with this small case series was to add to the general knowledge about this lesion, its presentation, clinical course, EEG, MRI, and pathologic findings when present in the temporal lobes. In our small case series, all patients presented with seizures or auras. However, one of the patient's seizures may be psychogenic. This same patient underwent resection of the lesion and did not experience seizure control after resection. However, the goal of resection was pathologic diagnosis rather than seizure control. Furthermore, all 3 patients had at least mild anxiety and comorbid psychiatric conditions included depression, OCD traits, and panic attacks. Larger case series may be helpful in identifying if temporal MVNT can cause psychiatric symptoms.For our 3 patients, lesions appeared stable on serial MRI ranging 2 to 17 years (mean 10.7 years). We agree with other publications that state these lesions can be followed with serial imaging from an oncologic perspective. Another series by Nunes et al. reported cases of temporal lobe epilepsy due to MNVT with resective surgery performed. The subjects in our small series, had either mild and rare seizures in 1 case (rare déjà vu) or rare convulsive seizures. Again, one of the patients may have psychogenic seizures. It remains unclear whether temporal lobe MNVT results in drug resistant epilepsy. Also, it is unclear whether lesionectomy is sufficient, or if these patients require 2-step epilepsy surgery with invasive monitoring to define epileptic zone margins beyond radiographic margins. Larger multi-center case series would help to answer these questions. Funding: No funding