ROSA (Robotic Stereotactic Assistance)
Epilepsy surgery remains vastly underutilized, in large part because many patients with epilepsy who might potentially benefit from diagnostic or therapeutic surgery are not referred to a comprehensive epilepsy center. A comprehensive evaluation by a multidisciplinary group of epilepsy physicians is recommended for patients who are not completely seizure-free after having tried two medications, for those who have lesional epilepsy, and for those who have medication side effects that reduce their quality of life. The evaluation process can be complex and may be daunting to both referring physicians and patients, who in addition may fear the possibility of surgery. Recent advances in epilepsy surgery, however, are making both diagnostic and therapeutic surgeries less invasive and more effective.
Diagnostic surgery most often has been accomplished in the United States though open craniotomy for subdural grid placement. Four years ago, R. Mark Richardson, MD, PhD, director of the Epilepsy and Movement Disorders Surgery Program at the University of Pittsburgh, began performing stereo-electroencephalography (SEEG), the percutaneous placement of multiple depth electrodes, in order to diagnosis the seizure onset zone in appropriate patients. This minimally invasive approach is more comfortable for patients but it traditionally requires a lengthy operation due to the use of a stereotactic frame, which can also limit electrode placement.
The ROSA robotic arm in the “home” position, after placement of several right temporal depth electrodes during a recent SEEG case.
UPMC Presbyterian recently became the first hospital in western Pennsylvania to use robotic assistance to improve this procedure. The Robotic Stereotactic Assistance (ROSA) system has a robot arm with six degrees of freedom — an architecture that simulates movements of a human arm, allowing the rapid and precise alignment of multiple trajectories for electrode placement (see image above). The robot does not do anything to the patient, but it reduces the operative time by half while removing frame-based geometrical limitations for electrode placement.
At UPMC, we are using these advanced SEEG capabilities to inform decisions on traditional resective surgery, as well as two other minimally invasive options: laser thermal ablation (LTA) and responsive neurostimulation (RNS). LTA is a procedure, like open resection, that may potentially cure a patient’s epilepsy. Rather than removing the seizure focus, however, the focus is ablated, using heat generated from laser light concentrated at the tip of a very thin probe. Several months ago, UPMC Presbyterian became the first hospital in western Pennsylvania to perform LTA for epilepsy.
Dr. Richardson now routinely employs the Monteris NeuroBlate® System for LTA via an interventional-MRI approach. Procedurally similar to the placement of electrodes during asleep DBS surgery, MRI scans are used to guide alignment of the trajectory and insertion of the probe in real time. Additionally, the ablation itself occurs under MRI guidance: special MRI scans are used to report the temperature of the target tissue and to create a continuous visual representation of the ongoing ablation. In mesial temporal lobe epilepsy, for instance, the ablation is confined to the hippocampus and amygdala, without affecting adjacent brain tissue (see image below). In this way, appropriate patients can leave the hospital the next day with a single absorbable stitch closing a tiny entry site in the scalp. Although the rates of cognitive side effects in our resection cases are low, an additional benefit of LTA over traditional open resection is to further reduce the chance of cognitive side effects from surgery.
Postoperative MRI image demonstrating selective ablation of the hippocampus. The contrast-enhancing border of the ablated tissue is delineated with red arrows
Robotic-assisted SEEG is also being used at UPMC Presbyterian to map an individual patient’s seizure circuit for RNS electrode placement. RNS is a brain modulation device that detects seizure activity and delivers therapeutic stimulation in response. This treatment option is appropriate for patients who have one or two localized seizure foci that are not amenable to resection, such as seizure onset in the eloquent cortex or bitemporal seizure onset. More efficacious than vagal nerve stimulation, the RNS device provides a personalized window into the brain for each patient by constantly recording brain activity. When a seizure is detected, the device immediately delivers safe levels of electrical current to disrupt seizure spread and reduce seizure duration.
Cutting-edge, minimally invasive, and personalized approaches are a cornerstone of the epilepsy surgery program within the UPMC Comprehensive Epilepsy Center, the only such comprehensive program in western Pennsylvania. Individuals with recurring seizures, their families, and/or their physicians, are encouraged to contact the program for more information regarding the modern standards of diagnostic and therapeutic epilepsy care.