Myokymia is defined as involuntary (uncontrolled), continuous, and slow movement of muscles. Depending on the muscles that are affected and the fat content under the skin, it may visible on the skin surface as continuous rippling movements. This is sometimes described as a worm-like motion and some patients may believe that that there are living organisms within the body. Myokymia can be seen during sleep and when the muscles are at rest.
Myokomia can be of four types which broadly describes its distribution:
- eyelid myokomia – affecting the muscles that control the eyelid.
- facial myokymia – affecting the muscles of the face.
- segmental or focal myokymia – affecting the muscles in one part of the body.
- generalized myokymia – affecting any part of the body either simultaneously or consecutively.
Myokymia is a rare clinical condition. It can be seen in patients suffering from different medical and neurological conditions and sometimes even in healthy people.Most of these diseases conditions are not life threatening. In healthy people the myokymia is sometimes observed after exercise is often harmless.
Myokomia affects many muscles of the body. In this condition, the involved muscles quiver but there is no movement in the nearby joints. Cranial or spinal nerves come from brain and spinal cord, respectively. These nerves go to different muscles and regulate their functions and movements. When the nerves are stimulated then the muscles contract. At rest, the muscles relax. Myokymia is seen in most muscles regulated by spinal and cranial nerves. In normal individuals also, it can sometime be seen briefly, usually after exercising.
The exact mechanism of myokymia is not completely known. The nerves from brain and spinal cord innervate many muscles simultaneously. The nerves are covered with a protective layer around them, called myelin. If myelin is damaged, there may be a problem in the transmission of signals through the nerves. This may result in involuntary, uncontrolled movements of muscles. Similarly, damage to nerves can also result in uncontrolled muscular movements. The reason why this may occur is not clear.
Common symptoms of all three types of myokomia may include the following:
- Muscular pain
- Spasms / cramps
- Muscle and joint stiffness
- Muscle weakness
The nerves associated with movements are called motor nerves, whereas sensory nerves carry sensations. In patients of myokomia, rarely a sensory nerve is involved. Therefore most of the symptoms are just movement-related and do not involve sensation-related complaints. Specific symptoms can be grouped according to the different types of myokymia.
In eyelid myokymia, the muscles of the lower eyelid contract and twitch. Other symptoms are shaking of the vision in one eye, a sensation of trembling, or tilted or vertical vision. Eyelid myokymia can occur at any point of time and may disappear suddenly.
In facial myokomia, surface muscles of the face are involved. Symptoms of facial myokomia are fine, slow, and worm-like movements of affected muscles and facial weakness. The voluntary activities of the muscles do not change the movements associated with facial myokomia.
Focal (segmental) myokymia
Focal or segmental myokymia, as the name suggests, affects only certain segments. It is seen mainly in the hands and feet.
Also known as Isaacs syndrome, generalized myokymia shows symptoms like uncontrolled involuntary movements, stiffened muscles, and decreased reflex actions of tendons. Muscle weakness, wasting, and excessive sweating are also seen. Generalized myokomia does not affect heart muscles and other smooth muscles (which are under involuntary control). It also does not produce sensory symptoms.
Transient myokymia seen in hand or calf muscles is sometimes caused by strenuous exercise. It can occur in any person and is not a cause for concern. Recurrent or persistent myokomia may be due to different causes depending on the type.
- Eyelid myokymia results from compression of a cranial nerve called the trochlear nerve. This nerve controls the action of eye muscles (superior oblique muscles) and therefore pressure on it causes twitching of eyes. Stress and fatigue can also precipitate eyelid myokymia.
- Facial myokymia is the most common of three sub-types. An inflammation resulting in loss of myelin (demyelination), tumors in the brainstem areas, damage in brain areas like pons and medulla, and medical conditions like Guillain-Barré syndrome can result in facial myokomia. Facial myokymia is sometime seen in some patients with history of radiotherapy.
- Focal/segmental myokymia is associated with a history of radiation therapy. Some neuropathies (damaged nerves resulting in pain and other symptoms) may also cause focal myokomia.
- Generalized myokomia or Isaacs syndrome occurs for as yet unknown reasons. It can be of two sub-types : congenital (present from birth) or acquired.While there may be a history of certain of the risk factors listed below, the reason why it persists in some people is still unexplained.
Myokymia Risk factors
Myokymia is associated with certain risk factors.
- Industrial toxins
- Natural poisons like snake venom
- Therapies like gold therapy
- Excessive caffeine intake
- Various medical conditions, such as myasthenia gravis
- Altered biochemistry like uremia and thyrotoxicosis
- Autoimmune diseases that affect the nervous system
Although the symptoms of myokymia are fairly characteristic, further tests are needed to exclude other conditions that may present in a similar manner. The following tests can be used to diagnose myokomia:
Urine and blood samples are tested for complete blood count (CBC), thyroid functions, and levels of creatine kinase, alcohol, and other toxins. Cerebrospinal fluid (CSF) surrounding the brain and spinal cord can be checked for infections or inflammations.
A computed tomography (CT) or magnetic resonance imaging (MRI) scan may be used to detect damage or presence of tumors in different regions.
Nerve conduction velocity (NCV) study
This test measures the speed of electrical signals through a nerve. In case of damaged nerves, speed of signals is slow. NCV test can detect neuropathies and demyelination.
This test is perfored along with NCV study. An electromyogram measures health of the muscles and the nerves that control the muscles. EMG confirms the presence of myokymic activites in muscles.
Transient myokymia that develops after exercising resolves on its own within few weeks or months. Treatment aims at treating the underlying cause. This strategy works for patients who develop myokomia due to conditions like thyrotoxicosis, poisoning, and alcoholism.
Facial myokymia or focal myokymia are not particularly troublesome. Similarly, eyelid myokymia is a harmless condition and goes away on its own in the majority of the patients.
- Immunomodulatory therapy: Immunomodulatory therapy helps patients with myokymia resulting from neuropathies.
- Medications: Drugs called phenytoin and carbamazepine are effective in treating patients with generalized myokymia or Isaacs syndrome. Carbamazepine provides relief from pain and cramps of involved muscles.
- Antiepileptic agents: These drugs stop seizures and stop seizure activity.
Surgery is performed for eyelid myokymia affecting the superior oblique muscles and inferior oblique muscles. Surgical options include cutting the tendons (tenectomy) and muscles (myectomy).