Myoclonic dystonia
[1] Myoclonus dystonia results from mutations in the SGCE gene coding for an integral membrane protein found in both neurons and muscle fibers.
Those suffering from this disease exhibit symptoms of rapid, jerky movements of the upper limbs (myoclonus), as well as distortion of the body's orientation due to simultaneous activation of agonist and antagonist muscles (dystonia).
Deep brain stimulation (DBS) is another viable option that can alleviate symptoms without the unwanted side effects of medications, and has been successful in treating other movement disorders.
[5] Dystonia is a response to simultaneous contraction of agonist and antagonist muscles seen as twisting and contorting that affect posture and stance.
Psychiatric issues are clinically diagnosed with the aforementioned symptoms and include depression, anxiety, personality disorders and addiction.
Neurological testing has been performed to determine the origins of these symptoms and multiple parts of the brain have been pinpointed including the brainstem, neocortex, pallidum, and thalamus.
These cause various effects in those diagnosed with myoclonus dystonia including changes in posture and tremors, and very rarely dementia and ataxia.
Epsilon sarcoglycan is a membrane protein that can be found in the liver, lungs, kidney, and spleen, but is most prevalent in muscle and neuronal cells.
Its prevalence in both muscle fibers and the synapses of neurons suggest why symptoms of both myoclonus and dystonia appear from the improperly functioning protein.
[8] Epsilon sarcoglycan itself is part of the dystrophin-associated protein (DAP) complex that binds the sarcolemma of muscle cells to the extracellular connective tissue.
Many drugs used to treat myoclonus dystonia do not have a significant impact individually, but when combined, can work on different brain mechanisms to best alleviate symptoms.
[4][11] Antiepileptics like valproate must act upon GABA receptors and manipulate ionic conductance to reduce tremors and spasms in myoclonus dystonia.
Different antiepileptics vary in sufficiency to control ionic conductance and can also produce seizures or myoclonus symptoms in some patients.
Acetylcholine is usually overactive in dystonia patients and blocking of this neurotransmitter would reduce contortion of the upper body, but can produce side effects of drowsiness, confusion and memory issues in adults.
Studies have also shown possible axon transport of this neurotoxin as well as its function as a pain reliever without effect on overactive muscle movement in myoclonus dystonia patients.
The frequency and intensity of this signal can be changed to monitor the effects on neuronal activity using voltage recordings or neuroimaging, like functional MRIs.
By re-positioning the electrodes in different areas or changing the size or timing of the stimulus, varying effects can be seen on the patient depending on the origin of the disorder.
[3] In one study, five patients with genetically determined epsilon sarcoglycan protein deficiency underwent deep brain stimulation of the internal pallidum.
[17] Other studies examined the effects of DBS to both the ventrointermediate nucleus of the thalamus, Vim, and the globus pallidus interna, GPi.
Following deep brain stimulation of GPi and Vim, the Unified Myoclonus Rating Scale disability score improved 61-66%.
