PMC6310741_01
Mass-like nonenhancing lesion present within the right hippocampal head measuring 1.9 x 1.6 x 1.2 cm. (A) Axial T1 pre-contrast. (B) Axial T1 post-contrast (C) Axial T2/FLAIR. (D) Coronal T2.
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Brain magnetic resonance imaging (MRI) demonstrated a right mesial temporal volume increase with no contrast enhancement, no cystic change, and no demonstration of facilitated diffusion on the ADC map (Fig. 1A-D).
Long-term continuous video EEG. The resting awake background consists of well-modulated, well-sustained, posterior dominant alpha rhythm at 9-10 Hz and 40-50 mV, which attenuated with eye opening and reoccurred with eye closure. There are frequent spike-and-slow waves with phase reversal at F8 and T4, along with intermittent slow waves at 4-5 Hz seen over the right temporal region. There are also independent sharp waves with phase reversal at T3 and T5. Frequent periodic lateralized discharges are seen in the right temporal region with phase reversal at F8 and T4. A focal onset seizure originating from the right mesial temporal region was captured lasting 37 s. This is seen on EEG as sharp waves which build up in the right temporal region before spreading to the right parasagittal region. On video, the patient was asleep. He woke up from sleep without any other clinical motor signs.
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Long-term non-invasive video electroencephalogram (EEG) revealed frequent interictal epileptiform discharges in the right and left temporal lobes independently (Fig. 2).
Intraoperative ECoG (A) Before resection. Frequent high voltage epileptiform discharges from middle inferior temporal region. No epileptiform discharges seen in the temporal cortical convexity. (B) After resection. Epileptiform discharges decreased significantly. Very infrequent small sharp waves seen in the mid temporal region.
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Intraoperative ECoG showed epileptiform discharges derived from the right mesial temporal region (Fig. 3A). Epileptiform discharges on intraoperative ECoG disappeared after gross total tumor resection and mesial temporal resection compromising the right anterior temporal lobe, right amygdaloid, and right hippocampus (Fig. 3B).
Histopathologic features of mtEVN. Scattered GFAP-positive cells in a background of reactive astrocytes with rare neurofilament-positive gangliocytic cells.
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Pathology reported extraventricular neurocytoma WHO grade II (Fig. 4A-B) with positive immunohistochemical staining for synaptophysin, NeuN, and MAP-2.
Follow-up MRI at 1-year post-resection. (A) Sagittal T1. (B) Axial T1.
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Follow-up MRI at one year (Fig. 5A-B) showed stable postoperative changes with no sign of residual or recurrent tumor.