Authors :
Presenting Author: Fernanda Ortiz, Neuropsycholgist – Clinica Cukiert
Julia Vieira, MD – Clinica Cukiert
Cristine Cukiert, MD – Sao Paulo Epilepsy Clinic
Vanessa Colares, MD – Sao Paulo Epilepsy Clinic
Rafael Guimaraes, MD – Clinica Cukiert
Jose Burattini, MD – Clinica Cukiert
Pamela Capitao, MD – Clinica Cukiert
Arthur Cukiert, MD – Sao Paulo Epilepsy Clinic
Rationale:
Hippocampal DBS (Hip-DBS) is a therapeutic option for patients with temporal lobe epilepsy who are otherwise not good candidates for resective surgery (due to memory concerns, bilateral foci, previous surgery, etc).
Memory is a major concern during Hip-DBS, as it is in any other procedure performed to treat temporal lobe epilepsy (resective, ablative, modulatory). We report on the memory function in patients with unilateral or bilateral temporal lobe epilepsy undergoing Hip-DBS .
Methods:
Nine patients with temporal lobe epilepsy who underwent Hip-DBS, had at least one year of follow-up and performed pre-and post-implantation full neuropsychological evaluation were studied. Bipolar, continuous stimulation was carried out using a duration of 300usec and a frequency of 130Hz. Mean stimulation intensity was 2.8mA for those patients with left unilateral foci. Mean stimulation intensity for patients with bilateral independent foci was 2.7mA (left) and 3.1mA (rightResults:
Five patients had unilateral left temporal lobe epilepsy and 4 had bilateral independent temporal lobe foci. Mean age was 37 years. Mean follow-up time was 68 months. Five patients had normal MRI and 3 patients had bilateral mesial temporal sclerosis. All patients were evaluated using RAVLT. Eight patients were evaluated by means of Wechsler Memory Scale (WMS) and one by Nepsy (Memory). Four patients are seizure-free during Hip-DBS (Engel I) and 5 were classified as Engel II (mean seizure frequency reduction= 83%). Mean General IQ was 111 and 110 preoperatively and during Hip-DBS, respectively ; Verbal IQ was 107 and 109 preoperatively and during Hip-DBS, respectively and Performance IQ was 112 and 109 preoperatively and during Hip-DBS, respectively. Global RAVLT mean results (n=9) were 7.7 and 7.6 preoperatively and during Hip-DBS, respectively; no patient disclosed memory changes according to RAVLT results. In those patients (n=8) who performed WMS, global mean results were 104 and 102 preoperatively and during Hip-DBS, respectively. One patient with left temporal lobe epilepsy showed a 15% decline in verbal memory during WMS, with no decline in RAVLT. She was high-functioning pre-operatively, is still functioning within normal limits and showed a proportional decline in general IQ during that period. She had severe depression before implantation and the IQ drop was likely related to an increase in psycho-active drugs post-operatively. The patient evaluated using Nepsy did not show any memory change during Hip-DBS.
Conclusions:
This is the first report on the effect of chronic, continuous Hip-DBS in memory functions. Hip-DBS was safe regarding memory function. There were no significant memory changes during bipolar, continuous hippocampal stimulation using the above-mentioned stimulation parameters. The net result of hippocampal neuromodulation in patients with both unilateral or bilateral foci is not a complete block of hippocampal activity. Hip-DBS likely modifies hippocampal physiological dynamics leading to higher epileptogenic thresholds.
Funding: none