ARMS tends to form more often in the extremities, trunk, and peritoneum. It is also typically more aggressive than ERMS. Pleomorphic
Pleomorphic rhabdomyosarcoma (undifferentiated) rhabdomyosarcoma), also known as anaplastic rhabdomyosarcoma, is defined by the presence of pleomorphic cells with large, lobate hyperchromatic nuclei and multipolar mitotic figures. These tumors display high heterogeneity and extremely poor differentiation. The pleomorphic cells may be diffuse or localized, with the diffuse variation correlating to a worse prognosis. It occurs most often in adults, rarely in children, and is often discovered in the extremities. Due to the lack of discernible separation among cancers of this type, clinicians will often label undiagnosed sarcomas with little to no discernible features as anaplastic RMS. It is the most aggressive type of RMS, and will often require intensive treatment. Spindle cell/sclerosing
Spindle cell/sclerosing rhabdomyosarcoma is an added subtype listed in the 2020 WHO classification of soft tissue sarcomas.This subtype is very similar to that of leiomyosarcoma (cancer of the smooth muscle tissue), and it has a fascicular, spindled, and leiomyomatous growth pattern with notable rhabdomyoblastic differentiation . It occurs most commonly in the paratesticular region, and the prognosis for this particular form of RMS is excellent with a reported five-year survival rate of 95%. The sclerosing aspect of this subtype has a hyaline sclerosis and pseudovascular development.Multiple classification systems have been proposed for guiding management and treatment, and the most recent and widely used classification system is the "International Classification of Rhabdomyosarcoma" or ICR.
The chemical messenger responsible for triggering the involuntary muscle contractions is blocked by the Botulinum toxins of the Botox.Surgery is also a viable option for treatment if the symptoms are caused by a tumor or lesion in the brain or spinal cord. Surgery may also correct symptoms in those where myoclonus affects parts of the face or ear. While DBS is still being studied for use with myoclonus, Deep Brain Stimulation has also been tried in those with this and other movement disorders. Prognosis
The effects of myoclonus in an individual can vary depending on the form and the overall health of the individual. In severe cases, particularly those indicating an underlying disorder in the brain or nerves, movement can be extremely distorted and limit ability to normally function, such as in eating, talking, and walking. In these cases, treatment that is usually effective, such as clonazepam and sodium valproate, may instead cause adverse reaction to the drug, including increased tolerance and a greater need for increase in dosage. However, the prognosis for more simple forms of myoclonus in otherwise healthy individuals may be neutral, as the disease may cause few to no difficulties. Other times the disease starts simply, in one region of the body, and then spreads. Research
Research on myoclonus is supported through the National Institute of Neurological Disorders and Stroke (NINDS). The primary focus of research is on the role of neurotransmitters and receptors involved in the disease.