Dystonia

Surgical Treatment of Dystonia

Thalamotomy and Pallidotomy
Surgical intervention may be considered in those patients with severe dystonia who have not responded or become non-responders to drug therapy. Thalamotomy and pallidotomy, which are surgeries used to treat individuals with Parkinson's disease, are now used to treat those with dystonia. During these two forms of surgery, specific areas deep within the brain that are involved with the initiation and generation of movement are targeted for destruction.

During a stereotaxic thalamotomy, a selected portion of the thalamus is surgically destroyed (ablated). The thalamus is a paired structure deep within the brain that is involved in the control of movement. In this procedure, neurosurgeons use specialized equipment, enabling them to use three-dimensional coordinates to precisely locate an area of the thalamus. Extreme care is exercised this structure is deep within the brain and located near other important structures. The possible complications of thalamotomy include contralateral weakness (hemiparesis), confusion, or dysarthria. Although these symptoms are relatively common during the postoperative period, they are usually short-lived and recede within a short period.

A pallidotomy involves destruction of part of the globus pallidus (GPi), a region of the brain involved with the control of movement. Destroying part of the GPi may help to restore the balance that normal movement requires. Pallidotomy is performed by insertion of a wire probe into the GPi. Once its placement has been confirmed by electrical tests, the probe heats surrounding tissue by emission of radio waves. The heat destroys nearby tissue. This procedure does involve risk and complications occur in about 10 percent of patients. For example, the surgical probe may strike a blood vessel during insertion, causing a slight stroke. Damage to non-target brain areas is also possible.

The goal of surgery for individuals with dystonia is to attempt to "rebalance" movement and posture control by destroying one or the other of these regions deep within the brain. These procedures have been performed in relatively few patients with dystonia as compared to their widespread use in those with Parkinson's disease. However, studies have shown these surgeries to be effective in most patients. Adverse effects may be considerable and include swallowing and speech difficulties as well as bleeding into the brain (cerebral hemorrhage).

Deep Brain Stimulation
Deep Brain Stimulation (DBS) is an invasive surgical procedure that seems to mimic the positive effects of surgical ablation performed during a thalamotomy or pallidotomy. During this procedure, electrodes are implanted in a specific area of the brain (i.e., thalamus or, more recently, globus pallidus). In addition, a device known as an implantable pulse generator (IPG) is placed under the skin in the area of the collarbone. After appropriate postoperative testing, leads from the implanted electrodes are connected to the pulse generator, which then delivers continuous high frequency electrical stimulation to the thalamus via the implanted electrodes. This form of stimulation helps the thalamus "rebalance" the control messages in the movement control centers of the brain. Patients may turn the pulse generator off and on by passing a hand-held magnet over the device. The batteries that power the pulse generator need to be surgically replaced every 3 to 5 years.

Adverse events due to thalamic stimulation are generally mild. The severity of complications and side effects usually correlate with the intensity of stimulation. The possible complications of DBS include mild speech impairment (dysarthria), weakness on one or both sides of the body, or disturbance of normal balance (dysequilibrium). In most patients, unusual sensations (paresthesias) such as numbness or tingling in the head and hands may occur after surgery; however, these sensations typically resolve with ongoing adjustment of the stimulator settings. About six percent of patients experience marked speech impairment or permanent, though tolerable, paresthesias. To date, deep brain stimulation has been performed on very few patients with dystonia. Generally, moderate improvement has been reported. Several clinical centers are currently conducting studies on DBS of the pallidum in patients with dystonia. Another feasibility study is being performed in those patients with intractable dystonia. See E-MOVE Article: Surgery for Dystonia.

Myectomy (Myotomy)
Selective myectomy or myotomy is a surgical procedure during which a portion of an overactive muscle is removed. This procedure was a common treatment for blepharospasm; however, with the advent of botulinum toxin treatment, selective myectomies are only rarely performed.

Ramisectomy and Rhizotomy
Ramisectomy and rhizotomy are surgical procedures that involve the cutting of a nerve(s) that innervates an overactive muscle. These types of surgeries are rarely performed; however, they may be effective in certain, properly chosen patients. They are most commonly performed on patients with cervical dystonia who have developed resistance to BTX-A. Possible adverse effects include permanent muscle weakness as well as difficulty swallowing. See E-MOVE Article Dystonia surgery (AAN report).

Peripheral Denervation
During selective peripheral denervation (SPD) or the Bertrand Procedure, nerves are removed at the point where they enter the selected, hyperactive muscle. Nerve supply (innervation) to uninvolved muscles is maintained. This procedure may be an option for some patients who were not successfully treated or have not responded to toxin therapy.