Дистонії

This rare dystonia is progressive and characterized by sustained, often bizarre postures. It is often inherited as an autosomal dominant disorder with partial penetrance due to mutations in the DYT1 gene (TOR1A pathogenic variant); in some family members, the gene is minimally expressed. For example, some carriers have no symptoms (a forme fruste of the disorder) or only dystonic tremor.

Symptoms of primary generalized dystonia usually begin in childhood with inversion and plantar flexion of the foot while walking. At first, the dystonia may affect only the trunk or leg but often progresses to affect the whole body, usually moving cephalad. Patients with the most severe form may become twisted into grotesque, nearly fixed postures and ultimately be confined to a wheelchair. Symptoms that begin during adulthood usually affect only the face or arms.

Mental function is usually preserved.

This rare dystonia (also called Segawa disease) is inherited as an autosomal dominant (DYT5a, GTP cyclohydrolase 1 gene [GTPCH1]) disorder or an autosomal recessive (DYT5b) disorder (tyrosine hydroxylase deficiency).

Symptoms of dopa-responsive dystonia usually begin during childhood. Typically, one leg is affected first. As a result, children tend to walk on tiptoes. Symptoms worsen at night. Walking becomes progressively more difficult, and arms and legs are affected. However, some children have only mild symptoms, such as muscle cramps after exercise. Sometimes symptoms appear later in life and resemble those of Parkinson disease. Movements may be slow, balance may be difficult to maintain, and a tremor may occur in the hands during rest.

Symptoms lessen dramatically when low doses of levodopa are used. If levodopa relieves the symptoms, the diagnosis is confirmed.

Focal dystonias affect a single body part. They typically start during adulthood, after age 20 to 30 years.

Initially, the posturing may be intermittent or task-specific (and thus is sometimes described as spasms). The movements tend to be more prominent during action and less so at rest, but these differences lessen over time, often resulting in distortion of the affected body part and severe disability. However, pain is uncommon except in focal primary dystonia of the neck (cervical dystonia) and in the dystonias that occur when response to levodopa starts to wear off in Parkinson disease (most often affecting the lower limb, eg, causing inversion of the foot).

Occupational dystonia consists of task-specific focal dystonic spasms triggered by performing skilled acts (eg, writer’s cramp, musician´s dystonia, the yips in golfers).

Spasmodic dysphonia consists of a strained, hoarse, or creaky voice due to focal dystonia of the laryngeal muscles.

Cervical dystonia manifests with involuntary tonic contractions or intermittent spasms of neck muscles. It has two forms:

• Caput: When the most proximal cervical vertebrae (C1 or C2) are involved

• Collis: When any of the lower cervical vertebrae (C3 to C7) are involved

The caput form (torticaput) involves muscles that move the skull or head joints; it is further described as anterocaput, laterocaput, or retrocaput. The collis form involves muscles that control the lower cervical vertebrae and is further described as anterocollis, laterocollis, retrocollis, or torticollis.

These dystonias affect ≥ 2 contiguous body parts.

Meige syndrome (blepharospasm plus oromandibular dystonia) consists of involuntary blinking, jaw grinding, and grimacing, usually beginning during late adulthood. It must be distinguished from the buccal-lingual-facial chorea of tardive dyskinesia and tardive dystonia (a variant of tardive dyskinesia).