Pediatric Movement Disorders - Dystonia

Treatment

Dopa-responsive dystonia (DRD) may cause a variety of motor symptoms that mimic other disorders. It is now recommended that any child with unexplained dystonia should receive a trial of L-dopa therapy. If the child does have DRD, the response is often dramatic and further testing may be arranged. L-dopa may also be helpful in some children with dystonia due to cerebral palsy, or perhaps in other metabolic disorders or structural abnormalities.

The most commonly used medication for children with dystonia is trihexyphenidyl (Artane®). Treatment with trihexyphenidyl sometimes requires very high doses of 50 mg or 100 mg per day, or even more in some children. If the dose is raised very slowly, then children seem to tolerate the medicine with relatively few side effects. Other medicines that may have some benefit include diazepam (Valium®), clonazepam (Klonopin®), valproate (Depakote®), baclofen, carbamazepine (Tegretol®), reserpine, or tetrabenazine (Nitoman®, not available in the U.S.). Choice of the best regimen is usually by trial and error. It is difficult to predict which medicine will be most effective for a particular child.

If the dystonia is particularly severe in only a few muscles (as with the focal dystonias), it may be possible to perform injections of botulinum toxin into those specific muscles. This toxin weakens the connection between the nerve and the muscle, thereby weakening the muscle. There is benefit in certain types of dystonia, with only minimal weakening of the muscle. The goal of injections of botulinum toxin is to reduce the symptoms of dystonia, without causing significant muscle weakness. Toxin injections usually need to be repeated every 3 to 6 months. In younger children, the procedure may require sedation or anesthesia.

There is a long history of the use of neurosurgical procedures to improve dystonia. There are reports of some success using deep brain stimulation (DBS), particularly in children who have a mutation in the DYT1 gene. Implantation of the stimulator electrode in the globus pallidus led to gradual resolution of symptoms over 2 to 12 months. In DBS, a pacemaker is implanted under the skin of the chest or abdomen and a wire runs from this pacemaker to a small hole in the skull, where it enters the brain. Pulses from the pacemaker are used to block abnormal activities in the basal ganglia.

Another recent and very promising treatment is implantation of the intrathecal baclofen pump. Although originally developed as a treatment for spasticity, recent results suggest that there may be benefit in dystonia as well. Intrathecal baclofen (ITB) is pumped from a small electric pump under the skin of the abdomen, through a catheter, directly onto the spinal cord. This allows relatively high amounts of the medicine to reach the cord, while not causing side effects on the brain (such as sleepiness). The same technique may be used for medicines other than baclofen, such as clonidine or morphine.

Other surgical procedures for dystonia include cutting muscles or lengthening tendons to help reduce the effect of the dystonic muscles. There have been reports that cutting the sensory nerves from muscles where they enter the spine is helpful (dorsal rhizotomy); however, this procedure is more likely to improve spasticity, rather than dystonia.