Abstracts

Rationale:

Brain stimulation use for medically intractable epilepsy has increased following the approval of the responsive neurostimulator(RNS) in 2013 and Deep Brain Stimuli(DBS) in 2018.

Despite the rapid surge in use of RNS/DBS stimulation for intractable epilepsy, little is known about neuroanatomic or neurochemical changes induced by chronic brain stimulation for the treatment of epilepsy. The purpose of this abstract is to report the first ever reported case of post-mortem neuroanatomical findings following chronic neurostimulation with a responsive neurostimulator in epilepsy.




Methods: A case report

Results:
A 26-year-old male with intractable epilepsy underwent RNS for 20 months with stimulation activated for 19 months. The patient’s generalized epilepsy characterized by focal features consistently showed a maximal right frontal temporal ictal pattern. Two depth electrodes were placed, one in the right and another in the left central median, along with cortical stripps on the right frontal regions and one on the left. The right central median and cortical strips were connected for stimulation. Autopsy was limited to the brain and the patient ‘s cause of death was likely probable SUDEP a previously reported outcome in some patients with RNS (Devinsky O, 2018).









Upon macroscopic examination, cerebral hemispheres were symmetric without edema or atrophy without uncal, subfalcine or tonsillar herniation. A slight distortion and irregularity of the cortex subjacent to the left cortical strip electrode while a slight darkening of the right superior frontal cortex was noted. Beyond the above, other macroscopic evaluation was generally normal.









Microscopically: The cerebrum shows neuronal loss, reactive gliosis, and scattered hemosiderin in the left frontal region, likely due to electrode placement. The neuronal count was normal, but some hyper eosinophilic neurons seen suggest possible autolysis and/or mild acute injury. White matter showed minimal thickened vascular walls and hemosiderin laden macrophages.









The thalamus showed small cavitary foci, reactive gliosis (GFAP immunostain), mild edema, and scattered hemosiderin around the bilateral central median nucleus consistent with depth electrode placement. Despite the occasional hyper-eosinophilic neurons and minimal artery thickening, the thalami structure appeared generally normal









The lack of abnormal neuroanatomic findings in this patient are consistent with one report of neurostimulation in the cerebellum in epilepsy (Wright G, 1983) and in Parkinson’s disease (Mallach, 2019) (Reddy GD, 2017)

Histopathology slides are going to be made available after 3 pm on 6/10/2024 . I will be happy to upload them when available. Sincere apologies





Conclusions: Our investigation revealed no discernible disparities or abnormal findings in the left and right cortical and thalamic nuclei, regardless of right sided stimulation. This may indicate that cortical stimulation in epilepsy patients is safe. These observations are similar to prior reports of deep brain stimulation in Parkinson's disease. However, to substantiate this inference, larger scale and longer duration studies are warranted.





Funding: None