225. Post-Hemispherectomy Cerebrospinal Fluid Shunt Placement Exacerbates Brain Shift In Pediatric Epilepsy Patients

Authors: Aria Fallah, MD, FAANS; Aria Fallah, MD; H. Westley Phillips, MD; Cassia Maniquis; Shannon Duby; Jia-Shu Chen (Los Angeles, CA)

Introduction:

Hemispherectomy and its modern variants are effective surgical treatments for medically intractable epilepsy confined to one hemisphere. While effective for seizure control, complications of hemispherectomy such as postoperative hydrocephalus are not uncommon necessitating Cerebrospinal Fluid (CSF) shunt placement. A less-studied phenomenon of brain shift towards the surgical cavity following hemispherectomy has also been described.  We aim to assess the natural history of brain shift in a large single-center hemispherectomy series and test the hypothesis that CSF shunts exacerbate this shift.

Methods:

We performed a retrospective review of consecutive pediatric patients undergoing hemispherectomy for medically refractory epilepsy at the University of California, Los Angeles between 1987 and 2019. Patients were stratified by general demographics, type of hemispherectomy (anatomic versus functional), pathology, type of shunt valve, criteria for shunting, seizure outcome, and overall post-hemispherectomy Midline Shift (MLS).

Results:

In our cohort, 232 patients were identified. Of these patients, 64% did not require a CSF shunt while 36% received a CSF shunt for treatment of hydrocephalus. Majority of CSF shunts were placed ipsilateral to the side of surgery. Shunted patients were found to have an increased median magnitude of MLS (7.0mm) compared to non-shunted patients (1.7mm), (p-value 0.018, 95% Confidence Interval [0.091, 0.904]). Additionally, patients with porencephalic cysts demonstrated increased MLS compared to patients with malformations of cortical development (p-value 0.043). Among the shunted cohort, Delta valves were associated with increased MLS when compared to programmable valves.

Conclusion:

Following hemispherectomy, the brain shifts minimally towards the side of surgery.  This shift is exacerbated by CSF shunting of the post-surgical cavity. The amount of shift is dependent on the etiological substrate and the type of CSF shunt used. Future studies regarding the clinical significance of MLS is warranted. This has not been systematically studied to date.