Hemidystonia-Hemiatrophy Syndrome

Hemidystonia-hemiatrophy (HD-HA) is a rare dystonia, usually caused by a static cerebral injury occurring at birth or during infancy, that is characterized by a combination of hemidystonia (HD), involving one half of the body, and hemiatrophy (HA) on the same side as the HD.

Epidemiology

The prevalence is unknown but between 30 to 100 cases of HD-HA have been described to date.

Clinical description

The mean age of HD onset is 14.9 years (range 1-46 years). HD (sustained and repetitive muscle contractions resulting in abnormal movements or posture involving a single side of the body) is preceded in 90 % of cases by hemiparesis with a marked improvement before the onset of HD. Pyramidal syndrome and seizures may also be observed. In HD-HA, dystonia is associated with ipsilateral somatic atrophy.

Etiology

Common causes of HD-HA are childbirth or perinatal complications, delayed sequelae of stroke or head trauma. The causative injury generally occurs at birth or during early infancy.

Diagnostic methods

Diagnosis of HD-HA is clinical, based on a careful anamnesis of the patient's birth and early childhood period and physical examinations, as well as brain imaging. Cerebral hemiatrophy, nonspecific diffuse atrophy, lesions involving the basal ganglia and thinning of the periventricular white matter with ipsilateral ventricular dilatation may be observed with magnetic resonance imaging (MRI). Brain imaging is characterized by lesions involving the basal ganglia or by cerebral hemiatrophy contralateral to the HD. Cerebral HA can lead to ipsilateral skull thickening and hyperpneumatization of paranasal sinuses, resulting in Dyke-Davidoff syndrome.

Differential diagnosis

HD-HA syndrome should be differentiated from other causes of primary dystonia or dystonia secondary to inherited disorders or neurodegenerative diseases.

Management and treatment

HD responds poorly to medical therapy and drugs such as anticholinergics, baclofen, benzodiazepines, and levodopa, in monotherapy or in combination, result in a modest or transient response. Botulinum toxin injections may be useful for HD if a relevant focal target can be identified. Deep brain stimulation mainly targeting the globus pallidus is not a routine treatment of HD-HA syndrome, but may be discussed in the most severe cases on an individual basis.

Prognosis

The younger the age of the offending cerebral insult, the longer is the delay in the onset of dystonia. The symptoms of delayed HD usually diminish and attain a plateau a few years after initial presentation; while HA of the affected body part usually remains stationary as the patient approaches the second decade of life.