Abstracts

Rationale: Periventricular nodular heterotopia (PVNH) is a neuronal migration disorder characterized by subependymal gray matter nodules and associated with drug-resistant epilepsy. Epileptiform activity in heterotopia was previously reported, but the role of heterotopia in the pathophysiology of epilepsy remains unclear. PVNH may be independently epileptogenic or may generate from the overlying cortex, posing a challenge for surgical resection. Previous studies showed interictal spikes from the heterotopic nodule, but ictal onset was concurrent with neocortex/mesial temporal structures. Intracranial electroencephalogram (EEG) is key to delineate the epileptic focus in the setting of PVNH and its signature EEG correlate has rarely been reported. Similarly, only a few studies have discussed the utility of magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in PVNH epilepsy. Methods: We reviewed clinical, radiographic, and EEG reports of our patient. We searched PubMed for literature using terms “periventricular nodular heterotopia & refractory epilepsy,” “periventricular nodular heterotopia & laser ablation,” and “periventricular nodular heterotopia & intracranial evaluation.” Results: Twenty-one-year-old left-handed African American male presented with medically refractory focal epilepsy with secondary generalization on Carbamazepine, Lacosamide, Lamotrigine, and Clobazam. First seizure occurred at age 15, with recurrent seizures occurring in sleep. Semiology was marked by flashing lights in right eye, followed by generalized tonic-clonic activity. No myoclonus/twitching. Family history and FLNA gene mutation were negative. Mild cognitive delay was present. MRI brain (Figure 1) showed periventricular heterotopic gray matter (L>R) and intraventricular nodules. Ictal single-photon emission computed tomography (SPECT) showed diffuse and focal hyperperfusion in the left and right temporal lobes, respectively. Intracranial EEG consisted of 58 electrodes (3 depth; 6 subdural strips); 8-contact depth electrodes over the left PVNH and left hippocampus, 4-contact depth electrodes over the right PVNH, 8-contact subdural strips over the anterior temporal and posterior subtemporal areas, 6-contact subdural strips over the anterior and medial subtemporal and superolateral temporal areas, and 4-contact subdural strips over the inferolateral temporal area. Patient was monitored over 6 days and 8 electrographic seizures were characterized by a burst of spike-wave activity, followed by immediate desynchronization across all electrodes of the left PVNH spreading to the right PVNH and left hippocampus before generalizing (Figure 2). Left PVNH resection via MRgLITT was performed with no complications. Antiepileptic drugs were tapered 6 months after MRgLITT with no seizure recurrences. Searching terms, “periventricular nodular heterotopia & refractory epilepsy” on PubMed yielded 54 results, while “periventricular nodular heterotopia & laser ablation” and “periventricular nodular heterotopia & intracranial evaluation” yielded only 5 and 3 results, respectively. Conclusions: Intracranial EEG is a key diagnostic study for PVNH management. EEG correlate characterized by a burst of spike-wave activity followed by immediate desynchronization was seen in 8 electrographic seizures in our patient and is a signature finding of PVNH which has rarely been reported in literature. Identifying this electrographic finding has diagnostic utility and can guide definitive treatment. While MRgLITT has extensively been studied in mesial temporal lope epilepsy, its utility in PVNH has been described in only a few studies and holds promise in PVNH epilepsy. Funding: No funding