What is dystonia?
Patients experience involuntary and persistent muscle contractions in the body, causing distortions, repetitive movements or postural abnormalities that severely interfere with daily life and activities. Dystonia is a common movement disorder, with about 39 dystonia patients per 100,000 individuals and about 460,000 in China.
How many types of dystonia are there?
According to the muscle groups involved in the patient’s body
1.Focal dystonia: Blepharospasm, spastic dysarthria, spastic slant neck, writing spasm and mouse hand, etc., are single-site muscle groups involved.
2.Segmental dystonia: Meige syndrome, axial dystonia, contains the involvement of two or more adjacent muscle groups.
3.Eccentric dystonia: half of the body is involved, usually secondary to dystonia. Multiple non-adjacent muscle groups are involved.
4, generalized dystonia: the combination of lower limb and any other segmental muscle groups, accompanied by axial direction of involuntary twisting dystonia, is the most common manifestation, called torsional spasm.
Generalized dystonia accounts for about 17%; limited dystonia accounts for about 50%, with spastic squint being the most common; the rest is eccentric or segmental dystonia.
According to the etiology of the disease
1.Primary dystonia: the etiology is not clear, there is no clear structural abnormality of the central nervous system in this group of patients, such as writing spasm, blepharospasm and spastic squint, etc.
2, secondary dystonia: there is a clear etiology, some are genetic diseases, such as hepatomegaly, Huntington’s chorea, echinocytosis, syndrome and gangliosidosis; some are caused by exogenous factors, such as cerebral palsy caused by perinatal injury, delayed dystonia caused by taking psychotropic drugs, etc., and limb spasticity caused by brain injury and spinal cord injury.
Non-surgical treatment of dystonia
Medication acts as a treatment by affecting the neurochemical transmitters in the nervous system that carry out the instructions given by the brain to control muscle movements. There are no curative drugs for dystonia. Sedative drugs can partially improve the symptoms while relieving the patient’s tension; the available drugs are Antan, clonidine, nitroprusside, baclofen, haloperidol, and butorphanol, etc. None of them are very effective, and some of them have significant side effects. For example, high doses of Antan can cause dry mouth, blurred eyes, and memory loss.
For focal dystonia and partial segmental dystonia that have failed to respond to oral medication, Botox injections can be administered and are effective in some patients. However, in some patients, the effects are limited in duration, and even repeated injections still do not satisfactorily control the symptoms.
Functional neurosurgery may be the only treatment for symptoms in most patients with dystonia, especially generalized dystonia and torsional spasms. Treatment options include: peripheral nerve or muscle dissection, deep brain electrical stimulation, thalamic or pallidum destruction and intrathecal baclofen infusion.
Indications for dystonia surgery
1. Who is suitable for peripheral nerve or muscle dissection?
Patients with spastic levator neck are suitable. Electromyography is performed before the dissection, and the spastic contracted muscles are judged by electrical nerve stimulation during the operation, and the nerves causing the neck spasm are partially cut off selectively, or the spastic contracted muscles are partially disconnected.
2.Who is suitable for deep brain electrical stimulation?
Patients older than 7 years old with primary dystonia, including generalized and segmental dystonia, eccentric dystonia with cervical dystonia, DBS can effectively improve symptoms by 40-90%, and the commonly used stimulation targets are medial pallidum or thalamic nucleus basalis. Patients with dystonia have a delayed response to treatment with continuous DBS, and dystonic postures gradually improve over a period of up to 1 year or more after surgical treatment. Deep brain electrical stimulation may also be considered for certain patients with secondary dystonia.
DBS uses an implanted medical device similar to a pacemaker to deliver precise electrical stimulation to targeted areas of the brain. This therapy is reversible and adjustable. It uses an implanted device to stimulate specific areas of the brain to help the circuits that control movement function more profitably. That is, this relieves motor symptoms. For example, muscle spasms, twisting, involuntary contractions, abnormal postures and uncontrolled movements. It is important to understand that DBS therapy for dystonia can hopefully control your symptoms, but it cannot cure them. When the DBS system is turned on, it will begin to provide stimulation to alleviate some or all of your symptoms. However, the symptoms return after the system is turned off.
Who is suitable for thalamic or pallidum disruption: This procedure destroys specific parts of the motor circuitry in the brain and is less safe than DBS, but has the advantages of convenience, affordability and ease of care. Disruption should always be performed in an experienced center that specializes in stereotactic surgery.
(1) For simple limited dystonia such as writing spasms and mouse hand, younger patients are suitable for stereotactic thalamic disruption surgery with less cost, no implant restrictions and more convenience for the patient.
(2) For primary dystonia, if the patient cannot afford the cost of bilateral brain pacemakers, unilateral pallidum destruction surgery with the other side of the brain pacemaker can be used with excellent results and high safety. However, for unilateral brain pacemakers whose cost is still unaffordable, bilateral pallidum destruction surgery can be used, which is relatively riskier than installing a brain pacemaker, however, experienced functional neurosurgeons can still effectively control the risk and ensure safety and long-term good outcome.
(3) For patients suffering from generalized dystonia, who have rejection to the implant and cannot tolerate it, destruction surgery can also be used.
4.Who is suitable for intrathecal baclofen infusion system?
Baclofen infusion into the cerebrospinal fluid is experimented by a pump that is connected to a small thin tube that is surgically implanted under the skin of the patient’s abdomen, wrapped around the back, connected to another thinner tube implanted under the skin of the back and entered into the cerebrospinal fluid through a needle attached to one end of the thin tube. Individuals may also improve shaking, swallowing, communication skills, upper limb and hand function, trunk control and gait.
Baclofen pumps have been shown to improve spasticity, including bilateral lower extremity spasticity due to cerebral palsy, lower extremity spasticity after spinal cord injury, spasticity of cerebral origin, and hereditary spastic paraplegia.