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Deep Brain Stimulation (DBS) therapy is a type of surgery that can be used to help children with movement disorders. Its primarily use in children is for the treatment of dystonia. Dystonia is a type of movement disorder in which faulty brain signals cause involuntary muscle contractions. These lead to abnormal movements, which typically are repetitive twisting or contorting of the arms, legs, neck or other body parts.
Dystonia’s are disorders that involve involuntary sustained muscle contraction, which result in repetitive, patterned movements causing abnormal posture and can be severely debilitating and painful. Dystonia is a chronic disorder, but the vast majority of dystonia’s do not impact cognition or intelligence. Most children with dystonia have a normal life expectancy.
Dystonia may begin in childhood or young adulthood, and may be genetic (often called “primary dystonia”) or be acquired secondarily to an insult to the brain such as hypoxia, premature delivery or a perinatal brain injury resulting in cerebral palsy (“secondary dystonia”). Some children with dystonia need detailed genetic investigations if no obvious cause can be found on brain imaging or looking at the clinical history.
Dystonia may occur only in a specific part of the body, like the eyelid or hand, or it may affect many body regions.
There are five main types of dystonia:
Focal dystonia – a single region, such as the hand or eyes, is affected e.g. cervical dystonia, writer's cramp, blepharospasm and laryngeal dystonia.
Segmental dystonia – two or more connected regions of the body are affected e.g. hemifacial spasm
Multifocal dystonia – two or more unconnected regions of the body are affected e.g. left arm and left leg
Hemidystonia – one entire side of the body is affected
Generalised dystonia – the trunk and at least two other parts of the body are affected
Dystonia may be present at rest, but often becomes much worse when the child is doing a specific task or motion, such as writing or walking. As a result, dystonia can become highly disabling. Dystonia is often painful, and the abnormal movements and postures may embarrass the child and make it difficult to perform well in school. Some children become wheelchair-dependent, and if dystonia is left untreated for years, it can cause permanent damage to joints and muscles as limbs become fixed into an abnormal position.
Deep Brain Stimulation therapy involves the very precise implantation of small wires/leads deep into the brain, into the centres that help to control movement. These implanted stimulating leads are tunnelled under the skin and connected via lead extensions to a battery/neurostimulator which sits under the skin on the chest or abdomen. This small device is similar to a pacemaker and sends small electrical pulses to the parts of the brain that are responsible for the involuntary movements. When the neurostimulator is active it can give children with dystonia more control over their body movements. The settings of the neurostimulator are adjustable, with a handheld wireless device, to maximise the benefit for the child’s individual needs.
The entire system is under the skin and no components can be directly seen. The battery is recharged remotely much like a modern mobile phone. Rechargeable batteries have a lifespan of 15-25 years but require recharging on a regular basis, sometimes daily. At the end of the lifespan of the battery the patient has to undergo a surgical procedure to replace the battery.
The commonest target for DBS in dystonia is an area of the basal ganglia called the Globus Pallidus Internus (GPi). GPi DBS is particularly effective in primary (genetic) dystonia’s, although it may take up to 2 years to gain significant effect. Secondary dystonia’s tend to be less responsive to GPi DBS than the primary dystonias, although our experience is that the impact on the quality of life can be significant.
DBS is considered for patients who have a movement disorder which fails to be adequately treated by medical therapy which includes anticholinergic, dopaminergic or benzodiazepine medications and botulinum toxin injections.
All possible surgical candidates go through a multidisciplinary pre-operative assessment process involving neurosurgeons, neurologists, specialist nurses, physiotherapists and other allied health professionals.
After surgery, postoperative outpatient assessments are conducted regularly, particularly over the first year, by specialist movement disorder/DBS nurses and/or neurologists/neurosurgeons who optimise the stimulation parameters on the basis of patient feedback and objective measurements.
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