Deep Brain Stimulation For Tardive Dyskinesia

Dystonia is a movement disorder in which the body’s muscles contract involuntarily, causing repetitive or twisting movements. Mild to severe muscle spasms may be painful and interfere with performing activities of daily living (ADLs) or specific tasks.

Other symptoms of dystonia include vision problems that affect the eyelids, difficulty moving the jaw, swallowing or talking, pain and fatigue due to constant contraction of the muscles, depression, anxiety, and withdrawal from society.

Medical experts don’t know exactly what causes dystonia. Because of this, treatments target only symptoms. Altered nerve-cell communication in several regions of the brain is suspected of playing a part. We do know that some forms of dystonia are inherited through the family genes.

Dystonia can affect one part of the body (focal dystonia), two or more adjacent parts (segmental dystonia) or all parts of the body (general dystonia). Focal dystonia that appears in people aged 21 or older usually begins in the neck, arm or face and tends to remain focal or segmental.

Dystonia may happen during a specific action, such as handwriting. The debilitating condition often gets worse with stress, fatigue or anxiety and becomes more noticeable over time. Dystonia may also signal another disease or condition, including:

  • Parkinson’s disease
  • Huntington’s disease
  • Wilson’s disease
  • Traumatic brain injury
  • Birth injury
  • Stroke
  • Brain tumor or certain disorders that develop in some people with cancer (paraneoplastic syndromes)
  • Oxygen deprivation or carbon monoxide poisoning
  • Infections, such as tuberculosis or encephalitis
  • Reactions to certain medications or heavy metal poisoning

Dystonia is one of the most common types of tardive dyskinesia.

Tardive dyskinesia (TD) is any involuntary, purposeless movement of the tongue, lips, face, trunk, and extremities that occur mainly in patients treated with long-term neuroleptic drugs which are prescribed for psychiatric disorders and certain gastrointestinal and neurological disorders.

TDs may present as grimacing, tongue protrusion, lip-smacking, puckering, and rapid eye blinking. Rapid movements of the arms, legs, and trunk and involuntary finger movements sometimes occur.

TDs are seen in many patients with schizophrenia, schizoaffective disorder or bipolar disorder who have received treatment with antipsychotic medication for long periods. From time to time, TDs strike other patients as well.

People with fetal alcohol syndrome, other developmental disabilities, and other brain disorders are at high risk for the development of TDs, which can begin after taking only one dose of the causative agent.

It is estimated that TDs occur in 30 percent of patients who take neuroleptic drugs. There is no cure for either dystonia or tardive dyskinesia.

The first step in treating TDs is to reduce or stop the use of the neuroleptic medication under a doctor’s supervision. This may not be a suitable option for patients with severe conditions. Substituting drugs for the neuroleptic may help some patients.

Drug treatments include tetrabenazine, benzodiazepines, clozapine, and botulinum toxin injections. Of these, only tetrabenazine is approved for treating tardive dyskinesia – and it has known side effects.

Symptoms of tardive dyskinesia may linger long after stopping the use of neuroleptic drugs. Often, the symptoms stop spontaneously but in some cases, they may persist indefinitely.

Surgery can disable or regulate nerves or certain brain regions in patients with severe dystonia.

Another therapy, deep brain stimulation (DBS) is proving very helpful for people who have an inherited, genetic form of dystonia or for those where an idiopathic (with no identified cause) dystonia who have a severe generalised dystonia, neck (cervical) dystonia or dystonic tremor when other treatment options (such as botulinum toxin injections and oral medications) haven’t provided adequate relief.

DBS is not as effective for most people who acquired dystonias later in life (as, for example, from cerebral palsy, a metabolic disorder or brain damage). Also, the treatment seems to be less effective as the proportion of life lived with dystonia increases – in other words, for children, DBS should be offered early.

During a surgical operation, two thin, insulated electrodes are inserted into the brain. A wire implanted under the skin connects the electrodes to a battery which is usually placed within the chest or the abdomen. Similar to a pacemaker, the battery powers the delivery of targeted electrical pulses which block the neurological signals that cause the symptoms of dystonia.

The battery is implanted beneath the skin on the chest wall – or sometimes the lower abdominal wall – making it barely visible. However, an outline of the shape of the device and the wires connecting it to the brain may be noticeable.

The electrodes are usually implanted in a part of the brain called the Globus Pallidus Interna (GPi). Stimulation of the GPi is known as pallidal stimulation. Sometimes, the thalamus, another brain region, is targeted instead. Minute, regulated electrical currents produced by the electrodes on both sides of the brain can reduce the involuntary muscle contractions caused by dystonia and ease the pain caused by dystonia.

When considering DBS to treat TDs, know that there are risks involved with the surgery, including:

  • Stroke / intracranial bleeding / hemiplegia (below 1% of cases)
  • Seizure (2%)
  • Infection from the implanted device (2-4%)
  • Device malfunction (1.8%)
  • Fracture of the lead (0.7%)

Also, take into account the battery life of the implant. Non-rechargeable batteries typically last 18 months to 2 years. Rechargeable batteries that can last for up to 9 years are an option but the patient has to remember to recharge them regularly.

How effective is DBS in treating dystonia and TDs? For inherited and idiopathic dystonias, DBS reduces the severity of symptoms by slightly more than 50%, on average, but individual experiences vary widely. About one in five patients (20 percent) who try DBS report very little benefit. Other patients say their symptoms were reduced by 80 percent or more.

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