Abstracts

Rationale: It has long been established that reorganization of brain function is not uncommon in persons with epilepsy, particularly in the context of early developmental damage or dysfunction. The crowding hypothesis, the idea that reorganization of function from the dominant to non-dominant hemisphere "crowds out" the typical function of that region, has been demonstrated. A paucity of research exists regarding the crowding hypothesis, especially in the transition from right to left. Neuropsychological evaluations can contribute meaningfully to understanding the patient's cognitive abilities in the context of knowledge about neurological functioning from structural and functioning imaging, thus elucidating clinical manifestation of such phenomenon as the crowding hypothesis.Our goal is to examine, from a multidisciplinary perspective including neurology and neuropsychology, the evidence of potential crowding in a case of right hemisphere epilepsy believed to stem from maldevelopment of the right hemisphere.  Methods: Case study Results: SF is a 43-year-old right-handed Caucasian lady with seizure onset in 1991 at age 17. She was found to have an epidermoid tumor in right posterior temporo-occipital area and underwent lesion resection in 1992. Seizures recurred in a few years, and she underwent epilepsy surgical evaluation in 1999. MRI brain showed a focal area of cortical dysplasia in right frontal area and known encephalomalacia. Wada revealed impaired recall with left sided injection. Neuropsychological evaluation (NPE) results were interpreted as associated with right temporal lobe dysfunction and her pattern of performance suggested that right medial temporal structures were not significantly compromised. In 2000, seizures were localized to right temporal lobe with subsequent right temporal lobectomy (confirmed hippocampal sclerosis) and resection of the recurrent epidermoid tumor.She had seizure recurrence in 2006 and MRI showed known right sided encephalomalacia with a small right medial temporal structure remnant. She continued to be intractable on further AEDs. In 2016, epilepsy monitoring unit failed to capture seizures, but frequent interictal epileptiform discharges were noted in the right temporo-occipital region.Repeat NPE was done in 2016 as part of surgical workup. She demonstrated similar performances across verbal and visual memory tasks as well as verbal versus perceptual reasoning abilities. Given right temporal lobectomy with hippocampal sclerosis, the expectation would be for visual memory decline after surgery, which was not seen, although there was a mild decline in learning and memory overall (possibly related to increased experience of seizure). Overall, her pattern of performance indicates probable early reorganization (Table 1).  Conclusions: This case clearly demonstrates the resiliency of cognitive functioning secondary to neuroplasticity. It also exhibits the importance of neuropsychological assessment and integration of results into the decision-making processes of epilepsy management.This case example provides evidence of the crowding hypothesis in the left hemisphere, i.e., visuospatial functioning relocating from right to left in the context of a right hemisphere developmental abnormality, "crowding out" verbal functioning to some degree. Although the crowding hypothesis has been previously discussed in the literature, it has only referenced left to right reorganization but not the reverse, as believed to be present in this case. This is notable in that crowding in either direction is theoretically possible, and understanding reorganization of cognitive abilities is essential to minimize risk and maximize outcome in the context of clinical practice.  Funding: None