Myoclonus

Clinic

• Myoclonus is an entity, characterized with a brief, involuntary, irregular (Lacking rhythm) twitching of one or more muscles.
• It is an entity belongs to Hyperkinetic movement disorders
• Myoclonus has CNS origin.
• It could be considered as Jerking or Myoclonic jerking.
• Question: Which entity, it belongs to? The answer maybe Myoclonic seizure.

Types

• Positive myoclonus: Sudden muscle contractions
• Negative myoclonus: Brief lapses of contraction
• Hypnic jerk: The most common circumstance under which they occur is while falling asleep. It occur in healthy persons and are experienced occasionally by everyone. However, when they appear with more persistence and become more widespread they can be a sign of various neurological disorders.
• Stimulus-sensitive myoclonus: It is triggered by a variety of external events, including noise, movement, and light.
• Sleep myoclonus occurs during the initial phases of sleep, esp at falling sleep. Some forms appear to be stimulus-sensitive. Some persons with sleep myoclonus are rarely troubled by, or need treatment for, the condition. However, myoclonus may be a symptom in more complex and disturbing sleep disorders, such as restless legs syndrome.
• Hiccups are a kind of myoclonic jerk specifically affecting the diaphragm.
• Provoked spasm: When a spasm is caused by another person it is known as a provoked spasm. Shuddering attacks in babies fall in this category.
• Essential myoclonus: It occurs in the absence of epilepsy or other apparent abnormalities in the brain or nerves. It is not increasing in severity over time.

Related disease

• Juvenile myoclonic epilepsy (JME) usually consists of jerking and muscle twitches of the upper extremities. JME is among the most common types of epilepsy and can affect one of every 14 people with the disease. These seizures typically occur shortly after waking up. Onset for JME can be seen around puberty for most patients.
• Lennox-Gastaut syndrome (LGS), or childhood epileptic encephalopathy, is a rare epileptic disorder accounting for 1–4% of childhood epilepsies. The syndrome has much more severe symptoms ranging from multiple seizures daily, learning disabilities, abnormal findings in electroencephalogram (EEG). Earlier age of seizure onset is correlated with higher risk of cognitive impairment.
• Progressive myoclonus epilepsy (PME) is a group of diseases characterized by myoclonus, epileptic seizures, tonic-clonic seizures, and other serious symptoms such as trouble walking or speaking.

• Reticular reflex myoclonus is thought to be a type of generalized epilepsy that originates in the brainstem. Myoclonic jerks usually affect the whole body and sometimes locally

• Cortical reflex myoclonus is thought to be a type of epilepsy that originates in the cerebral cortex. In this type of myoclonus, jerks usually involve only a few muscles in one part of the body, but jerks involving many muscles may occur.

Related Sign / Symptoms

• Clonus: Both are involuntary twitching but clonous is rhythmic and Myoclonous is irregular.
• Fasciculation

Note:

• Hypnic jerk is the most common Myoclonus, which occur while falling asleep

• Myoclonic jerks occur in healthy people, however, when they appear frequently or generally, they can be a sign of various neurological disorders.
• Hiccup is a kind of myoclonic jerk affecting diaphragm. When a spasm is caused by another person it is known as a provoked spasm. Shuddering attacks in babies fall in this category.

Related entities

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Causes

Myoclonus as a symptom of

• MS
• Parkinson's disease
• Alzheimer's disease
• Opsoclonus myoclonus
• CJD
• Lyme disease
• lupus.
• Seizures: MERRF (Myoclonic Epilepsy with Ragged Red Fibers)
• Rare mitochondrial encephalomyopathy.

Related disease

• Dystoni
• Gaucher's disease
• Subacute sclerosing panencephalitis
• Serotonin syndrome
• Huntington's disease
• Cerebral palsy

Pathophysiology

• Most myoclonus is caused by a disturbance of the central nervous system.
• Some are from peripheral nervous system injury.
• 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.

Miasms

• CJD
• FFI
• HTLV-1
• NPH
• NVCJD