[MIM 159 900, 616 398]

(Myoclonic dystonia)

Prevalence: 1 to 9/1.106. Dominant autosomal transmission with maternal imprinting (the child does not develop the disease if it inherits the gene from his mother) of a mutation of the SCGE gene (epsilon sarcoglycan) (7q21.3) coding for a transmembrane protein that is part of the glycoprotein-dystrophin complex in the cardiac and striated muscles but also in the monoaminergic neurons, the hippocampus, the cortex and the Purkinje cells.

Clinical presentation:

-        onset in the first or second decade

-        jerky movements resembling myoclonus ("in flash") usually caused by a complex task (writing, drawing) and dystonia. They are usually limited to the neck, upper limbs and trunk. Sometimes the clinical expression is limited to a spasmodic torticollis, a tremor or a writer's cramp. These movements are often attenuated by alcohol intake.

-        in 2/3 of cases, there is also focal or cervical dystonia.

-        there may be associated psychiatric problems: depression, panic attacks, obsessive-compulsive disorder, alcoholism.

Treatments: for localized dystonias: local injections of botulinic toxin; for severe cases: bilateral internal stimulation of the pallidum or the intermediate central nucleus of the thalamus

Anesthetic implications:

in the presence of a brain stimulator: stop it at induction of anesthesia and preferably use a bipolar electrocautery with short times of use; do not perform MRI without neurosurgical advice. The fact that the mutation may compromise the functioning of the dystrophin complex in the striated muscle implies that it is probably prudent to avoid succinylcholine and halogenated agents (see Duchenne's disease).

References:

-        Nemeth AH.
The genetics of primary dystonias and related disorders.
Brain 2002; 125: 695-721.

-        Yeoh TY, Manninen P, Kalia SK, Venkatraghavan L.
Anesthesia considerations for patients with an implanted deep brain stimulator undergoing surgery: a review and update.
Can J Anaesth 2017; 64: 308-19.

Updated: December 2019