Make Way for the NexFrame!
A New Frameless Approach to Deep Brain Stimulation Surgery
When the regimen of existing medications and the various rehabilitation strategies become less effective in managing symptoms, surgical intervention can be considered. Such an intervention is deep brain stimulation (DBS). This is a relatively new surgical intervention used to treat movement disorders such as essential tremor, Parkinson’s disease and dystonia. It received approval from the Food and Drug Administration (FDA) to treat essential tremor and tremor in Parkinson’s disease in July 1997 and for advanced motor symptoms in Parkinson’s disease in January 2002. It is currently approved for the treatment of dystonia through a humanitarian device exemption. It appears to be most effective in those with primary or hereditary dystonic conditions such as torticollis or cervical dystonia and generalized dystonia. It can also help tardive dyskinesia which is a movement disorder caused by certain medications. The level of benefit from DBS is not as significant in secondary dystonia that is associated with cerebral palsy and/or other types of damage to the brain. More research is needed to determine how best to treat these conditions.
DBS for the treatment of dystonia involves administering a well-controlled electrical current into the globus pallidus (GPi), the malfunctioning portion of the brain. The electrical current functions as an “off switch” by disrupting abnormal brain signals that are responsible for the abnormal physical movement. This disruption helps restore more normal activity in the GPi thus enabling more controlled movement. DBS does not involve destruction of brain tissue and its effects are reversible and adjustable. It is now preferred over the pallidotomy, a surgical technique that involves the actual destruction of the brain cells that are “misfiring.”
The effectiveness of the DBS procedure depends on accurate placement of a brain lead or wire. Electrical impulses generated from an implanted battery, which looks very similar to a cardiac pacemaker, pass through the lead and into the GPi, the malfunctioning area of brain tissue. This area is approximately the size of a grape. However, the target area within the GPi is approximately the size of a grain of rice! Special imaging techniques and the placement of a metal, stereotactic head frame to the patient’s skull guide the positioning of the leads. Microelectrode recording (MER) is also conducted during surgery and involves “listening” to the brain cells. Certain areas of the brain have a characteristic sound and MER helps to identify these specific areas. The patient is awake during this and other portions of the surgery and becomes an important member of the team. The patient helps in determining whether side effects occur when the stimulation is applied during surgery.
DBS surgery is time consuming, usually lasting four to six hours per side of the brain being operated on. The most common complaints from patients include back and neck pain and fatigue. These complaints occasionally can become so disabling that the patient has a difficult time participating in the surgery and/or requests to have the surgery prematurely stopped. The traditional approach to DBS surgery involves attaching a large, metal halo device to the patient’s skull and securing it to the surgical table. Although the effectiveness of this frame has been proven during its use for decades, it creates complete immobilization of the patient’s head and neck and it obscures one’s line of vision.
In an effort to simplify the DBS procedure and enable greater patient comfort and participation during surgery, a frameless stereotaxy technique has been developed. In this technique, the heavy frame has been replaced with five small bone screws and the NexFrame, a disposable guidance device (picture). This new device, originally developed by Image Guided Neurologics (IGN), does not require that the head and neck be kept in a fixed position and the patient can move or adjust his/her position if needed. Importantly, the accuracy of the frameless and framed techniques has been found to be equal. (J.Neurosurg/Volume 103/ September, 2005).
In August 2005, Medtronic Neurological, the world-wide leader in DBS therapy acquired IGN and the NexFrame technology. This acquisition demonstrates the confidence this company is placing in this “frameless” approach to brain surgery. The implications of DBS therapy are far-reaching not only in the treatment of movement disorders but for disorders such as epilepsy and depression. DBS and this new frameless option offer much promise to those suffering from certain forms of dystonia that are refractory to medical therapies.
Dr. Kathryn Holloway
Associate Professor. Dept. of Neurosurgery and Neurosurgical Director for the Southeast Parkinson’s Disease Research Education and Clinical Center, McGuire Veterans Affairs Medical Center, Richmond, VA.
Miriam L. Hirsch, M.S., R.N.
Neurosurgical Nurse Coordinator
Virginia Commonwealth University Medical Center
Movement Disorders Program
Harold F. Young Neurosurgical Center
Ambulatory Care Center
417 N 11th Street, 6th Floor
P.O. Box 980631
Richmond, VA 23298-0631
My mom and I wanted to thank you for hosting such a great symposium this year. This was our third year and we are looking forward to next years. E. Mathews