Dystonia

Definition

Dystonia is a syndrome of CNS lesions manifested by uncoordinated arrhythmic changes in the tone of various muscle groups. It is clinically characterized by focal or generalized involuntary fixed postures or motor acts. Diagnosis is made based on clinical data on the presence of dystonic phenomena. Instrumental examinations are aimed at finding the causative disease. Conservative therapy includes kinesiotherapy, prescription of pharmaceuticals, local injection of botulinum toxin, and physiotherapeutic effects. In generalized forms, neurosurgical treatment is possible.

General information

Muscle tone is necessary to maintain body posture and to perform movements. In contrast to reduced (hypotonus) and increased (hypertonus) muscle tension, muscular dystonia (MD) refers to a violation of the adequate ratio of tone of individual muscles or muscle groups. MD is not a disease itself; it is a syndrome found in various lesions of the central nervous system. According to European studies, muscular dystonia occurs in Western Europe, with a frequency of 11.2 cases per 100,000 population. The onset of manifestations is possible at any age. Earlier onset of symptoms leads to faster progression of the syndrome with subsequent generalization of the process.

Causes

The etiologic factors of MD may be various brain lesions that extend to the structures of the extrapyramidal system responsible for tone regulation. In children in the first year of life, muscular dystonia develops mainly due to abnormalities in the development of the nervous system in the intrauterine period or its damage during childbirth. Possible causes include fetal hypoxia, intrauterine infections, toxic effects (smoking, alcohol intake, drug addiction, drug treatment of the pregnant woman), and birth trauma of the newborn. In older children and adults, the following main etiologic factors are identified:

• Genetic abnormalities. Genetic mutations cause changes in the mediator or receptor part of nerve synapses involved in transmitting tone-regulating influences. Hereditary forms of MD include idiopathic blepharospasm, myoclonic dystonia, and primary torsional dystonia.
• Craniocerebral trauma. Damage to subcortical structures in traumatic brain injury and conductive pathways of the extrapyramidal system causes a disorder of central regulation of muscle tone. In case of incomplete recovery, muscle dystonia persists in the posttraumatic period.
• Brain tumor. By sprouting cerebral tissue, aggressive intracerebral neoplasia destroys neurons and conductive pathways. In non-invasive growth, as the tumor grows, surrounding masses are compressed. MD occurs when extrapyramidal structures are involved in the pathologic process.
• Encephalitis. Inflammatory damage of various levels of the extrapyramidal system in encephalitis leads to a disorder of its regulatory effect on muscle tone. MD may manifest itself against the background of subsiding of the acute inflammatory process and regression of more severe neurological symptoms.
• Drug exposure. Provoke dystonic disorders are capable of antiparkinsonian pharmaceuticals, neuroleptics, antidepressants, and antipsychotics. Risk factors for side effects of therapy are long duration of intake and high dosages.

Classification

According to the localization of dystonic phenomena, there are cranial, paraorbital, oromandibular, cervical, pharyngeal, torsional, and other forms of MD. According to etiology, dystonic syndrome is classified into primary and secondary. The following classification is based on the prevalence of the pathological process in muscle groups. According to this criterion, the following forms of MD are distinguished:

• Focal. The pathologic process covers no more than one muscle group. Focal forms include writing spasm, blepharospasm, and spastic dysphonia.
• Segmental. Tonic contraction extends to several adjacent muscle groups. An example is a combined oromandibular MD.
• Multifocal. Focal dystonic phenomena are observed in several parts of the body. Pathologic muscle contractions in them may occur simultaneously and independently of each other.
• Generalized. Involuntary muscle tension extends to almost the entire skeletal musculature. Starting with focal forms, MD can transform into a generalized form.

As the dystonic syndrome develops, the severity of pathologic changes worsens. In this regard, there are 4 degrees of severity of MD. In clinical practice, they are evaluated as stages of dystonia development.

• I—Changes are expressed minimally. The dystonic syndrome is manifested in a situation of increased mental tension and overwork.
• II—Muscular dystonia regularly occurs during physical activity. There are no dystonic phenomena at rest.
• III—Muscular dystonia has a permanent character and intensifies during voluntary movements. It is difficult to perform actions involving dystonia-prone muscle groups, and professional activities are restricted.
• IV—Pronounced MD, which disables the patient by preventing the patient from independently performing certain movements.

Symptoms of muscular dystonia

The main clinical manifestations are dystonic postures and motor acts. Polymorphism of symptomatology is caused by different localizations of the process, strength, speed, and frequency of muscle contractions. The general pattern for dystonic phenomena is their stereotypical character, occurrence in performing arbitrary motor acts, intensification during fatigue, sleep deprivation, stress, reduction after sleep, rest, and in a hypnotic state.

In most cases, muscular dystonia manifests focal forms. Writing spasms are manifested by spastic contraction of the hand muscles, which makes it impossible to continue writing. 

In infants, muscular dystonia is manifested by unnatural postures, turning the head always to one side, turning over only one side, and lagging static-motor development. In many cases, focal manifestations are gradually transformed into segmental manifestations, spread to other body parts, and a few years later passing into generalized MD. The earlier the debut of dystonia, the faster the generalization occurs. The long-term isolated course of focal dystonias is observed in patients with the manifestation of clinical symptoms after 25-35 years of age.

Complications

Progressive muscular dystonia significantly disturbs the patient’s motor sphere, complicating professional and household activities. Over time, the performance of professional duties becomes impossible, and the patient goes on disability. The cervical form is complicated by the development of torticollis. With torsional MD, spinal curvatures develop; at later stages, respiratory disorders are possible. Blepharospasm leads to entropion and dryness of the anterior segment of the eye. In several cases, neuritis and compression neuropathies of peripheral nerves of the limb performing dystonia-correcting movements are observed.

Diagnosis

Diagnosis is established by a neurologist based on clinical data, considering complaints of dystonic manifestations and examination results. Further diagnostic examinations aim to determine the cause of the dystonic syndrome and verify the underlying disease. The main stages of diagnosis are:

• Collection of anamnesis. The age of symptom onset and the sequence of its development are of diagnostic value. In younger children, attention is paid to the perinatal anamnesis, and in older patients – to the medications taken. The presence of diseases with dystonic manifestations in close relatives is established within the family history. 
• Examination of a neurologist. In the neurological status, a focal or generalized tonus disorder is determined. Muscle strength is preserved or slightly reduced. Reflex and sensory spheres, without pathology, may be disturbed in developing secondary neuropathies.
• Instrumental studies. They are conducted to identify the organic pathology of the nervous system. According to the symptomatology, an X-ray of the spine, MRI of one section of the spine, ultrasound of the head and neck, MRI of the brain, and electroneuromyography may be prescribed. 

Muscular dystonia treatment

Therapy is aimed at reducing symptoms and improving the patient’s well-being. Its component eliminates factors aggravating dystonia (overwork, excessive muscle tension, lack of sleep, stressful situations). To achieve the best result in treatment, a combination of several of the following methods is used:

• Kinesiotherapy is carried out by specialists in rehabilitation medicine: rehabilitation therapists, kinesiotherapists, and massage therapists. Patients are recommended to use both passive methods (massage, mechanotherapy) and active exercises with specially selected corrective gymnastics, such as swimming in the pool.
• Drug treatment. The basic drugs are benzodiazepines that reduce neuronal excitability. They can be combined with myorelaxants, sedatives, and antidepressants. The positive therapeutic effect of cholinolytics is due to their ability to slow the passage of nerve impulses.
• Botulinum therapy is used in focal and segmental forms. Botulinum neurotoxin is injected directly into the muscles involved in pathological phenomena. Botulinum toxin blocks cholinergic transmission in innervating muscle endings. The drug’s effect lasts up to one month.

Surgical treatment is indicated in severe generalized MD when conservative methods are insufficiently effective. Stereotactic destruction of the ventrolateral thalamic nucleus is most often used. Methods of surgical treatment of various forms of the disease continue to be developed; in particular, deep brain stimulation is increasingly used to treat dystonia.

All these treatment options are available in more than 750 hospitals worldwide (https://doctor.global/results/diseases/dystonia). For example, Deep brain stimulation (DBS) can be done in 18 clinics across Turkey for an approximate price of $33.6 K (https://doctor.global/results/asia/turkey/all-cities/all-specializations/procedures/deep-brain-stimulation-dbs). 

Prognosis and prevention

The course of secondary dystonic syndrome depends on the nature of the underlying disease. The prognosis of idiopathic forms is more serious the earlier the manifestation of clinical manifestations occurs. Timely initiated complex therapy can significantly improve the patient’s quality of life and delay disability. Prevention consists of the exclusion of adverse effects on the fetus during intrauterine development, adequate choice of delivery method, prevention of traumatism, infectious and oncologic lesions of the CNS, and careful planning of the timing and dosage of drug therapy.