Cortical stimulation in pharmacoresistant focal epilepsies

Surgery for Epilepsy Involving Rolandic and Perirolandic Cortex: A Case Series Assessing Complications and Efficacy

BACKGROUND

Surgical removal of lesions around the rolandic cortex remains a challenge for neurosurgeons owing to the high risk of neurological deficits. Evaluating the risk factors associated with motor deficits after surgery in this region may help reduce the occurrence of motor deficits.

OBJECTIVE

To report our surgical experience in treating epileptic lesions involving the rolandic and perirolandic cortices.

METHODS

We performed a single-center retrospective review of patients undergoing epilepsy surgeries with lesions located in the rolandic and perirolandic cortices. Patients with detailed follow-up information were included. The lesion locations, resected regions, and invasive exploration techniques were studied to assess their relationship with postoperative motor deficits.

RESULTS

Forty-one patients were included. Twenty-three patients suffered from a transient motor deficit, and 2 had permanent disabilities after surgery. Six patients with lesions at the posterior bank of the precentral sulcus underwent resection, and 5 experienced short-term motor deficits. Two patients with lesions adjacent to the anterior part of the precentral gyrus, in whom the adjacent precentral gyrus was removed, experienced permanent motor deficits. Lesions located at the bottom of the central sulcus and invading the anterior bank of the central sulcus were observed in 3 patients. The patients did not experience permanent motor deficits after surgery.

CONCLUSION

The anterior bank of the central sulcus is indispensable for motor function, and destruction of this region would inevitably cause motor deficits. The anterior bank of the precentral gyrus can also be removed without motor impairment if there is a preexisting epileptogenic lesion.

Electrical neurostimulation in glaucoma with progressive vision loss

Background

The retrospective study provides real-world evidence for long-term clinical efficacy of electrical optic nerve stimulation (ONS) in glaucoma with progressive vision loss.

Methods

Seventy glaucoma patients (45 to 86 y) with progressive vision loss despite therapeutic reduction of intraocular pressure (IOP) underwent electrical ONS. Closed eyes were separately stimulated by bipolar rectangular pulses with stimulus intensities up to 1.2 mA sufficient to provoke phosphenes. Ten daily stimulation sessions within 2 weeks lasted about 80 min each. Right before ONS at baseline (PRE), vision loss was documented by static threshold perimetry and compared to the same assessment approximately 1 year afterwards (POST). Mean defect (MD) was defined as primary outcome parameter. Perimetries with a reliability factor (RF) of max. 20% were considered.

Results

Perimetry follow-up of 101 eyes in 70 patients fulfilled the criterion of a max. 20% RF. Follow-up was performed on average 362.2 days after ONS. MD significantly decreased from PRE 14.0 dB (median) to POST 13.4 dB (p < 0.01). 64 eyes in 49 patients showed constant or reduced MD as compared to baseline (PRE 13.4 dB vs. POST 11.2 dB). In 37 eyes of 30 patients, MD increased from PRE 14.9 dB to POST 15.6 dB.

Conclusions

Innovative treatments that preserve visual function through mechanisms other than lowering IOP are required for glaucoma with progressive vision loss. The present long-term data document progression halt in more than 63% of affected eyes after ONS and, thus, extend existing evidence from clinical trials.

Control of epileptic seizures by electrical stimulation: a model-based study

High frequency electrical stimulation of brain is commonly used in research experiments and clinical trials as a modern tool for control of epileptic seizures. However, the mechanistic basis by which periodic external stimuli alter the brain state is not well understood. This study provides a computational insight into the mechanism of seizure suppression by high frequency stimulation (HFS). In particular, a modified version of the Jansen-Rit neural mass model is employed, in which EEG signals can be considered as the input. The proposed model reproduces seizure-like activity in the output during the ictal period of the input signal. By applying a control signal to the model, a wide range of stimulation amplitudes and frequencies are systematically explored. Simulation results reveal that HFS can effectively suppress the seizure-like activity. Our results suggest that HFS has the ability of shifting the operating state of neural populations away from a critical condition. Furthermore, a closed-loop control strategy is proposed in this paper. The main objective has been to considerably reduce the control effort needed for blocking abnormal activity of the brain. Such an energy reduction could be of practical importance, to reduce possible side effects and increase battery life for implanted neurostimulators.