​​​Pharmacologic Therapy of Dystonia In Children

​​​Pharmacologic Therapy of Dystonia In Children
Dystonia refers to a syndrome of involuntary sustained or spasmodic muscle contractions involving co-contraction of the agonist and the antagonist. The movements are usually slow and sustained, and they often occur in a repetitive and patterned manner; however, they can be unpredictable and fluctuate.

The frequent abnormal posturing and twisting can be painful, and the functional impact of dystonia can vary from barely noticeable to severely disabling. Consequently, dystonias can have a profound effect on the personal, vocational, and emotional life of a patient and can impact his/her ability to live independently.

The options to medically manage dystonic movements have traditionally been 4-fold; they consist of the following:

  1. Rehabilitative therapies
  2. Oral medications
  3. Neurochemolytic interventions
  4. Surgery
  • Psychological counseling and participation in support groups are vital adjuncts to medical and physical approaches in the multidisciplinary management of dystonia.
  • Surgical options for intractable dystonias include altering the location or length of problematic muscles, but this is rarely successful. Other techniques include transection of the spinal accessory nerve for cervical dystonia, stereotactic thalamotomy or pallidotomy for generalized dystonia, and deep brain stimulation (DBS). 
  • Thorough neurologic, physiatric, neuropsychologic, and physical therapy evaluations are important prior to consideration for surgery. Because of the risk of significant comorbidity, surgical approaches are reserved for patients with disabling dystonia in whom other treatment modalities have been exhausted.

    Common Types of Dystonias

    Cervical dystonia

    • Cervical dystonia, or torticollis, is the most common focal dystonia. It has an insidious onset in people aged 30-50 years, although it can begin earlier. Cervical dystonia commonly affects women.
    • Intermittent spasms of the neck muscles or abnormal head movements occur because of contractions of the sternocleidomastoid, trapezius, and posterior cervical muscles. This effect results in a patterned, repetitive, and spasmodic movement that causes the head to twist (rotational torticollis), extend (retrocollis), flex (anterocollis), or tilt toward the shoulder (laterocollis). The patient may display more than 1 of these head movements simultaneously.
    • Patients may report psychiatric symptoms associated with depression or anxiety. These may be due to the chronic course of the illness rather than to real psychopathology.

    Upper limb dystonia

    • Upper limb dystonia causes cramping and posturing of the elbows, hands, and fingers that lead to the inability to perform certain occupational tasks. The literature describes at least 55 occupations in which individuals are affected by this condition. Men and women are affected with equal frequency. Onset is in persons aged 10-50 years.
    • A common upper limb dystonia is known as writer’s cramp, occupational cramp, or graphospasm. This task-specific dystonia, manifesting as hyperextension or hyperflexion of the wrist and fingers, may be triggered by repetitive activities such as writing and attempting to play the piano or other musical instruments.  After cessation of the task, the spasm disappears. Although torticollis, tremor, and pain are accompanying symptoms, the spasm itself usually limits further activities.
    • The results of general physical and neuromusculoskeletal examinations are usually unremarkable. Some clinicians inadvertently label these conditions as occupational neuroses.

    Lower limb dystonia

    • This may occur in stroke or dystonia-parkinsonism syndrome and lead to painful positioning of the leg, impaired gait, and altered bone development.
    • A study by Martino et al indicated that lower limb dystonia is an uncommon condition in adulthood. Evaluating 579 patients with adult-onset primary dystonia, the investigators found 11 patients (8 women, 3 men) with lower limb dystonia, with the condition existing either alone (4 patients) or as part of a segmental/multifocal dystonia (7 patients). In 63.6% of the patients, the dystonia spread to the lower limb from another site, while in the remaining patients, the condition originated in the lower limb. The authors noted that 64% of the patients required treatment.

    Oromandibular and lingual dystonia

    • Oromandibular, facial, and lingual dystonias are grouped together because of their possible coexistence. Cranial dystonia, commonly known as Meige syndrome, is the most common craniocervical dystonia. Women are more commonly affected, and onset is in the sixth decade of life.

    Dystonia musculorum deformans (torsion dystonia)

    • Dystonia musculorum deformans, or torsion dystonia, is the term used to describe a generalized form of dystonia that involves the trunk and limbs. There are at least 2 types, and onset may begin in childhood or adolescence, infrequently occurring as abnormal movement of a limb after an activity. The movements progress in severity and frequency until they become a continuous spasm, resulting in contortion of the body.
    • At first, rest relieves the spasms, but as the disease progresses, the level of activity and positioning have no effect. The shoulder, trunk, and pelvic muscles undergo spasmodic twisting, as do the limbs. The hands are seldom involved. The orofacial muscles also may be affected, leading to dysarthria and dysphagia.
    • The pathology of dystonia musculorum deformans has yet to be described. In some cases, genetics appear to play a role. Autosomal dominant and recessive patterns of inheritance have been reported. A rare, sex-linked form associated with parkinsonism has been described in the Philippines.

    Tardive dyskinesia (tardive dystonia)

    • This is a common complication of long-term antipsychotic drug treatment due to dopamine receptor antagonism. The precise mechanism is unknown, but the risk appears to increase with advancing age. When medication is withdrawn relatively early in a patient’s treatment, the dyskinesia may reverse, whereas after 6 months of exposure, the movement disorder may persist indefinitely. The clinical features of tardive dyskinesia include abnormal choreoathetoid movements, especially involving, in adults, the face and mouth (ie, blepharospasm, torticollis, oromandibular dystonia), and in children, the limbs.

      Pharmacologic Therapy

      • Medications can be somewhat effective in controlling dystonic movements, but the lack of knowledge about the exact pathophysiology of dystonia has made the development of specific pharmacologic therapies difficult. Systemic medications benefit about one third of patients and consist of a wide variety of options, including the following  :
      1. Cholinergics
      2. Benzodiazepams
      3. Antiparkinsonism drugs
      4. Anticonvulsants
      5. Baclofen
      6. Carbamazepine
      7. Lithium
      • Successful drug therapy often requires combinations of several medications, with choices generally guided by empirical trials and adverse effect profiles. Doses should be slowly increased over the course of weeks or months until the therapeutic benefit is optimized or until adverse effects occur. In most patients, discontinuation of the drugs requires tapering to prevent withdrawal symptoms.
      • Baclofen, given intrathecally by an implanted pump, can be very effective in certain types of dystonia, especially if spasticity coexists. Due to the low prevalence of side effects when the medicine is delivered into the cerebrospinal fluid, the ability to deliver the medicine continuously, and the ability to test the therapeutic effect prior to proceeding with surgery, this option may provide effective treatment for many patients.

      Neurochemolytic procedures or muscle blocks

      • Neurochemolysis of dystonic muscles is another important therapeutic option. Botulinum toxins or phenol/alcohol injections have become powerful tools in improving the symptomatic treatment of focal dystonias.  These injections temporarily reduce the ability of the muscles to contract and may be the treatment of choice for blepharospasm, cervical dystonia, and hemifacial spasm.
      • Botulinum toxins are produced by the gram-negative bacterium Clostridium botulinum and act by inhibiting the presynaptic release of acetylcholine at the neuromuscular junction. Of the 7 immunologically distinct botulinum toxin serotypes, only types A and B are approved for clinical use. The onset of effect takes several days after injection.
      • The local injection of botulinum toxins into the offending muscles (often the sternocleidomastoid, trapezius, and splenius capitis) reduces muscle contraction for approximately 3 months. The treatment is not associated with significant complications, although dysphagia and dry mouth can occur. The medications can be used effectively for years, and although they are expensive, their cost is typically reimbursed by insurance. Most patients require repeated injections.
      • Phenol and alcohol nerve blocks also are temporary, but they last approximately 6 months and are significantly less expensive. However, only selected nerves can be injected, and a skilled practitioner is needed in order to avoid side effects.
      • The selection of appropriate muscles should be based on careful clinical assessment of the maximally involved muscles and on a clear delineation of the goals (eg, improved function, hygiene, pain relief). Initial needle placement in the chosen muscle, often with the aid of electromyelographic localization, is based on anatomic landmarks. The number of injection sites and overall dose vary depending on the size of the muscle, the degree of dystonia present, and the functional change desired.


       

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