45 Can Surgical Ablation Modify a Developmental Visuospatial Impairment in Periventricular Nodular Heterotopia? A Case Study

Abstract

Objective:Periventricular nodular heterotopia (PVNH) is a malformation of cortical development (MCD) characterized by aggregates of gray matter adjacent to the lateral ventricular walls. Clinical presentation is heterogeneous with higher rates of seizures and reading impairments typically in the setting of average IQ (Felker et al. 2011). The majority of neuropsychological inquiry has focused on reading fluency, though a single case study showed a neurocognitive profile consistent with nonverbal learning deficits in a 7-year old boy with suspected autosomal dominant bilateral heterotopia (McCann et al., 2008). Given the periventricular focus and potential for unilateral presentations, non-linguistic neurocognitive sequelae may be expected in cases affecting the non-dominant hemisphere, yet this remains largely unexplored. Surgical ablation by laser interstitial thermal therapy (LITT) is increasingly used for epilepsy management in PVNH (Thompson et al., 2016, Whiting et al. 2020). However, there are no reported studies exploring cognitive outcomes following LITT of focal PVNH.Participants and Methods:A 46-year-old, right handed, Black female with 16 years of education presented for management of medically refractory epilepsy. Epilepsy monitoring captured intermittent slow waves in the right temporal lobe, interictal polyspikes in the right temporal lobe, and three epileptic events all emanating from the right temporal lobe. MRI showed extensive migrational anomalies involving the right hemisphere posteriorly consistent with PVNH with no associated mesial temporal sclerosis. Pre-surgical neuropsychological evaluation showed a significant split in IQ, with verbal IQ = 99 and performance IQ = 76. Testing indicated circumscribed deficits in visuoperceptual judgement, visuoconstruction, visuospatial reasoning, non-verbal recall, and several executive weaknesses in the context of otherwise average neurocognitive functioning. Fine motor speed was impaired bilaterally. Her profile was suggestive of non-dominant fronto-parieto-temporal dysfunction, concordant with the remainder of her work-up. By history she reported longstanding academic weaknesses in math and organization with strong verbal and reading abilities.Results:The patient underwent partial LITT of right PVNH sparing areas involved in visual function. At 6-month follow-up she was seizure free (Engel outcome 1A). Post-surgical neuropsychological evaluation showed reliable improvements in perceptual reasoning, aspects of learning/memory, and verbal naming. Visuoconstruction remained impaired but qualitatively improved. She also reported subjective experience of improved mental clarity and was applying for jobs after regaining driving privileges.Conclusions:This case demonstrates symptoms and history concerning for a nonverbal learning disorder in an adult woman with epilepsy secondary to right hemisphere PVNH and underscores the importance of exploring the range of neurocognitive profiles in MCD. Her notable neurocognitive and functional improvements following surgical ablation and seizure freedom suggest a possible release of function in the absence of inhibitory neurophysiological influences. This raises interesting questions about the endurance of her developmental profile. This case report contributes to our understanding of neuroanatomical correlates of neurocognitive and neurodevelopmental presentations. Future investigations should explore neuropsychological changes following LITT for PVNH.