Dystonia

Dystonia is a hyperkinetic movement disorder with repetitive or sustained muscle contractions forcing limbs, face or trunk into twisting, repetitive movements or abnormal postures. This can be focal, segmental (2 or more body areas), unilateral or generalized. Onset can be at any age and some forms are progressive.

There is difficulty performing particular activities rather than a movement; e.g. Normal movement observed in foot while sitting or running but dystonia noted while walking.

Dystonia is thought to originate in the basal ganglia including Caudate, Globus Pallidus, Putamen, Substantia Nigra and Thalamus.

EMG can differentiate from continuous motor unit activity.

Causes

A) Focal– Torticillis, Oculogyric crisis, Blepharospasm, Drug induced, Neuronal storage disorders, Syringomyelia

B) Generalised – HIE at birth, Battens disease, Dopa-responsive dystonia, Glutaric academia type 1, Wilsons disease, Mitochondrial diseases, post brain injury, brain tumour, Drug-induced & Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis

Differentials

Tics, Cramps, Sandifer syndrome, Spasticity, Focal seizures, Stereotypical movements, Spasmus nutans, Congenital torticollis

Presentation

There is a wide variation of underlying neurological disorders with sustained abnormal postures such as twisting of hands, fisting or feet turning. Sometimes torticollis or stridor is seen. Dystonia often present with gait or speech abnormality. These resolve during sleep.

Many cases also have epilepsy and other movement disorders

Developmental delay or regression is common. Microcephaly or Macrocephaly can be seen.

Disturbance of consciousness, sleep or emotional states seen. 

Discomfort or pain may be experienced with neck dystonia or generalised dystonias.

Cases may have hypotonia or spasticity (misleading diagnosis of Cerebral Palsy). Distinguish from spasticity which is associated with hypertonia, noticeable with rapid stretching, other UMN signs and worsening spasms in sleep. 

Investigations

None if there is a known antenatal or birth hypoxia known. Else consider:

– MRI brain to exclude differentials

– Neuro-metabolic investigations- CK, SAA, Blood Gas, Ammonia, Lactate/ Pyruvate, Copper, AFP, VLCFA, Urate, TFT. CSF Glucose, Lactate, Neurotransmitters.

– Chromosomal microarray, Genetic dystonia panels

– Urine Organic Acids & Amino Acids

Management

There is no curative treatment, but symptom management helps improve QOL.

For dopa-responsive types, start Carbidopa-Levodopa at low dose & slowly increase- particularly consider if cause unclear and MRI Brain normal.

Medication that may help include: Trihexyphenidyl, Baclofen, Clonidine, Carbamazepine, Gabapentine or Benzodiazepines.

Selective denervation or Botulinum toxin type A is helpful for focal dystonias such as affecting neck.

Intrathecal Baclofen or Deep Brain Stimulation may help in certain cases

Joint contractions, Postural deformities and mental health issues can arise

Support from Physiotherapy, Occupational Therapy, Speech Therapy and support staff is helpful with daily living activities.