Causes of Myoclonus

Cause details for Myoclonus: Although some cases of myoclonus are caused by an injury to the peripheral nerves (defined as the nerves outside the brain and spinal cord, or the central nervous system), most myoclonus is caused by a disturbance of the central nervous system. Studies suggest that several locations in the brain are involved in myoclonus. One such location, for example, is in the brainstem close to structures that are responsible for the startle response, an automatic reaction to an unexpected stimulus involving rapid muscle contraction.

The specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement. These parts are interconnected in a series of feedback loops called motor pathways. These pathways facilitate and modulate communication between the brain and muscles. Key elements of this communication are chemicals known as neurotransmitters, which carry messages from one nerve cell, or neuron, to another. Neurotransmitters are released by neurons and attach themselves to receptors on parts of neighboring cells. Some neurotransmitters may make the receiving cell more sensitive, while others tend to make the receiving cell less sensitive. Laboratory studies suggest that an imbalance between these chemicals may underlie myoclonus.

Some researchers speculate that abnormalities or deficiencies in the receptors for certain neurotransmitters may contribute to some forms of myoclonus. Receptors that appear to be related to myoclonus include those for two important inhibitory neurotransmitters: serotonin, which constricts blood vessels and brings on sleep, and gamma-aminobutyric acid (GABA), which helps the brain maintain muscle control. Other receptors with links to myoclonus include those for opiates, drugs that induce sleep, and for glycine, an inhibitory neurotransmitter that is important for the control of motor and sensory functions in the spinal cord. More research is needed to determine how these receptor abnormalities cause or contribute to myoclonus.¹

Underlying condition causes of Myoclonus: The list of possible underlying conditions (see also Misdiagnosis of underlying causes of Myoclonus) mentioned in various sources as possible causes of Myoclonus includes:

• Infection
• Head injury
• Spinal cord injury
• Stroke
• Brain tumors
• Kidney failure
• Liver failure
• Lipid storage disease
• Chemical poisoning (type of Poisoning)
• Drug poisoning (type of Poisoning)
• Hypoxia - causing posthypoxic myoclonus.
• Other causes of symptoms seizures or spasms

Myoclonus as a complication: Other conditions that might have Myoclonus as a complication might be potential underlying causes of Myoclonus. The list of conditions listing Myoclonus as a complication in our database includes:

• Sandhoff Disease

Myoclonus as a symptom: Conditions listing Myoclonus as a symptom may also be potential underlying causes of Myoclonus. The list of conditions listing Myoclonus as a symptom in our database includes:

• Alpers Syndrome
• Corticobasal Degeneration
• Creutzfeldt-Jakob Disease
• Hydranencephaly
• Opsoclonus Myoclonus
• Prion diseases
• Ramsay Hunt Syndrome Type 2
• Sandhoff Disease

Related information for causes of Myoclonus: Further relevant information on causes of Myoclonus may be found in the risk factors for Myoclonus and underlying causes of Myoclonus.

Footnotes:
1. excerpt from Myoclonus Fact Sheet: NINDS

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