Dystonia is defined as a neurological disorder characterized by involuntary, sustained, repetitive, similar muscule contractions that result in twisting movements or abnormal postures of the affected body areas.
The ethiology of different types of dystonia is not entirely clear; however, a significant number of genetic loci have been discovered attributed to the disease. The occurrence of dystonia is due to degenerative changes in different brain structures and tracts, mainly in substantia nigra, nucleus caudatus, thalamus, locus ceruleus, damage to the strio-palido-thalamic links with the premotory cortex. Glutamatergic stimulation and dopaminergic afferentation from substantiа nigra to striatum are important mediatory systems.
Classification of dystonia:
A) By etiology:
1) Primary dystonia (idiopathic)
2) Secondary dystonia (symptomatic)
3) Dystonia-plus syndromes
Primary dystonias are the most common dystonias. They can be of spontaneous or hereditary nature. Secondary dystonias are less common. They are associated with inflammatory and autoimmune diseases, structural and vascular CNS disorders, medication intake, toxins, mental factors. The have a sudden onset and rapid progression. Dystonia-plus syndromes demonstrate additional symptoms, including Parkinson’s syndrome, myoclonic seizures, etc.
B) By the age of onset:
1) Childhood-onset dystonia (0 to age of 12)
2) Adolescent-onset dystonia (age 13 to 20)
3) Adult-onset dystonia (older than the age of 21)
The younger one is at onset, the greater the chance that the disease will be severe and symptoms will spread.
C) By anatomic areas affected:
1) Focal
2) Segmental
3) Multifocal
4) Generalized
Focal dystonia symptoms are limited to one area of the body, i.e. upper or lower limbs, neck, facial muscles, etc. Focal dystonia oalso includes cervical dystonia (tirticollis), professional dystonias (of typewriters, tailors, artists, piano players): graphospasm, blepharospasm, oromandibular, lingual, pharyngeal and laryngeal (spasmodic) dystonia.
Segmental dystonia affects two connected parts of the body. Examples include craniocervical, brachial and axial dystonia.
Multifocal dystonia affects two or more parts of the body which are not connected.
Generalized dystonia affects several parts of the body. Hemidystonia affects only one half of the body.
Some common dystonias include:
Blepharospasm: Belongs to the group of focal dystonias. When combined with oromandibular dystonia, it may be referred to as the Meige’s syndrome. It is characterized with involuntary, bilateral, synchronic muscle contractions around the eye, and is more common in women at the mean age of 50. Contractions increase when watching televisions, reading and driving and will resolve after a period of rest.
Oromandibular dystonia: Affects the muscles of the lower face and jaw. It is more common in women of middle and advanced age. It includes involuntary movements of the lower jab, tongue, lips. Patients tend to shift their lower jaw to the side, make grimaces and often have lip or tongue biting, and difficulty with speaking and chewing.
Cervical dystonia (torticollis spastica): The most common of the focal dystnonias. It begins with neck muscle constriction or pulling the head forwards or backwards, which later affects the position of the head causing it to tilt towards the opposite shoulder. The process affects different groups of muscles. In the event of long-term progression of the disease, muscle contractures and spondylosis changes can be observed in the neck region of the spine accompanied by severe pain. The so called sensory tricks can be used to suppress dystonia, i.e. applying pressure to certain areas of the neck and chin. Cervical dystonia disappears during sleep.
Graphospasm: This is the strong grip of the pen or pencil while writing or strong muscular spasms of fingers. This causes arm contractions and pain, and difficulty with writing.
Acute neuroleptic dystonia: This form belongs to the secondary dystonias and occurs with patients receiving neuroleptic agents immediately after treatment onset. It is more common in young women. Acute neuroleptic dystonia causes muscle spasms and abnormal postures of the body. In most cases it affects the cranial muscles, neck and torso. It can be influenced by the administration of anticholinergic agents and antihistamines.
Late dyskinesia or dystonia: It occurs months or years after neuroleptic treatmet or upon sudden discontinuation of treatment. Similarly, it is more common in women at the age of 50 and more. It involves involuntary movements, such as protruding tongue, making faces, sucking lips, blepharospasm, cervical dystonia, etc. In 50-90% of the cases it disappears spontaneously within one or two years after the end of neuroleptic therapy but it is also possible to persist and progress.
Dyskinesia and dystonia with levodopa treatment: One of the most common complication following continuous levodopa treatment in patients with Parkinson’s disease. There are several types of dyskinesia and dystonia. Dyskinesias at ‘peak concentration of levodopa’ occur with the maximum drug concentration in the blood. Usually they are choreiform movements. With the so called two-phase dyskinesias, changes can be observed immediately upon increase, or decrease, respectively, of the plasma concentration of levodopa. They seem to reduce and even disappear at peak plasma concentrations. Such dyskinesias are very hardly tolerated by patients; they are also a therapeutic issue for neurologists.
Treating them is not easy. However, different groups of medicines can be used: anticholinergic agents, dopamine receptor antagonists, GABAergic and noradrenergic agonists, tricyclic antidepressants, botulinum toxin, stereotaxic thalamotomy, etc.
Botulinum toxin is the most effective treatment of focal dystonias.