Abstracts

Rationale: Deep brain stimulation of the Anterior Nuclei of the Thalami (ATN-DBS) is a neuromodulation therapy used in patients with therapy-resistant epilepsy (TRE). Accurate surgical DBS lead placement is critical for an optimal clinical outcome, but it can be difficult to identify the ATN in some patients. We want to analyse the outcome of our patients implanted with ATN-DBS, establish the exact localization of each electrodes and determine the variability between neurosurgeons.  Methods: We identified all patients with TRE epilepsy, who underwent ATN-DBS implantation in our Epilepsy program at Western University, since this treatment became available in Canada, until March 2019. The planning of the DBS lead placement was analyzed by three expert neurosurgeons. Results: Six patients were implanted with ATN-DBS. The median age was 30.5 years (IQR=17.8-28.5) and five were males. The most common etiologies were non-lesional and malformation of cortical development. The median number of antiseizure medications (ASM) was 3(IQR=3-4) at the time of the implantation. Vagus nerve stimulation failed to control seizures previously in all of the patients. The median follow up time after implantation was 36.5 months (IQR24-55.8m) and the therapeutic output current was 6.216mA(IQR=5.314-9.5mA) in the right side and 6.67mA(IQR=5.1445-11.65mA) on the left side electrode. The median rate of seizure reduction at the time of last follow up was -3.5%(IQR=[-52.8]-[86]) and only one patient had a seizure reduction greater than 50%. The optimal implantation coordinates for each patient was determined by an expert surgeon. In the only responder, the Euclidean distances from the optimal target point were 3.23 mm in the left and 4.7 mm in the right. In the non-responders, the average Euclidean distances from the optimal point were 4.43 mm in left and 4.50 mm in the right. There was a difference of Euclidean distances between neurosurgeons, 6.20 mm in the left and 4.74 in the right. The transventricular and extraventricular approaches were the most commonly used.But, in posterior planning, extraventricular and posterior parietal approaches were selected.  Conclusions: DBS-ANT may help some patients with TRE. There is an inter-neurosurgeon variability with regards to the approach and location of electrodes. More data is required to localize the most effective target in ATN. Funding: No funding