Opsoclonus
Encyclopedia
Opsoclonus refers to uncontrolled eye movement. Opsoclonus consists of rapid, involuntary, multivectorial (horizontal and vertical), unpredictable, conjugate
fast eye movements without intersaccadic
intervals. It is also referred to as saccadomania or reflexive saccade
. The movements of opsoclonus may have a very small amplitude
, appearing as tiny deviations from primary position.
Possible etiologies of opsoclonus include neuroblastoma
and encephalitis
in children, and breast, lung, or ovarian cancer in adults. Other considerations include multiple sclerosis
, toxins, or medication effects. It can also be caused by a lesion in the omnipause neurons which tonically inhibit initiation of saccadic eye movement (until signaled by the superior colliculus
) by blocking paramedian pontine reticular formation
(PPRF) burst neurons in the midbrain. It frequently occurs along with myoclonus
in opsoclonus myoclonus syndrome
.
Conjugate eye movement
Conjugate eye movement refers to motor coordination of the eyes that allows for bilateral fixation on a single object. Several centers in the brainstem are involved. Horizontal conjugate gaze is controlled by the nuclei of CN III and CN VI, the paramedian pontine reticular formation, and the...
fast eye movements without intersaccadic
Saccade
A saccade is a fast movement of an eye, head or other part of an animal's body or device. It can also be a fast shift in frequency of an emitted signal or other quick change. Saccades are quick, simultaneous movements of both eyes in the same direction...
intervals. It is also referred to as saccadomania or reflexive saccade
Saccade
A saccade is a fast movement of an eye, head or other part of an animal's body or device. It can also be a fast shift in frequency of an emitted signal or other quick change. Saccades are quick, simultaneous movements of both eyes in the same direction...
. The movements of opsoclonus may have a very small amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
, appearing as tiny deviations from primary position.
Possible etiologies of opsoclonus include neuroblastoma
Neuroblastoma
Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an annual incidence of about 650 cases per year in the US , and 100 cases per year in the UK . Close to 50 percent of neuroblastoma cases occur in children younger than two years old...
and encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
in children, and breast, lung, or ovarian cancer in adults. Other considerations include multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
, toxins, or medication effects. It can also be caused by a lesion in the omnipause neurons which tonically inhibit initiation of saccadic eye movement (until signaled by the superior colliculus
Superior colliculus
The optic tectum or simply tectum is a paired structure that forms a major component of the vertebrate midbrain. In mammals this structure is more commonly called the superior colliculus , but, even in mammals, the adjective tectal is commonly used. The tectum is a layered structure, with a...
) by blocking paramedian pontine reticular formation
Paramedian pontine reticular formation
The paramedian pontine reticular formation, or PPRF, is part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons. It is involved in the coordination of eye movements, particularly horizontal gaze and saccades.- Input, Output, and Function...
(PPRF) burst neurons in the midbrain. It frequently occurs along with myoclonus
Myoclonus
Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...
in opsoclonus myoclonus syndrome
Opsoclonus myoclonus syndrome
Opsoclonus Myoclonus Syndrome is a rare neurological disorder of unknown causes which appears to be the result of an autoimmune process involving the nervous system. It is an extremely rare condition, affecting as few as 1 in 10,000,000 people per year. It affects 2 to 3% of children with...
.
See also
- ClonusClonusClonus is a series of involuntary muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, and is particularly associated with upper motor neuron lesions such as in stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy...
- EpilepsyEpilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
- Pathologic nystagmus
- Physiologic nystagmus
- Psychogenic non-epileptic seizuresPsychogenic non-epileptic seizuresPsychogenic non-epileptic seizures , also known as Non-Epileptic Attack Disorders, are events superficially resembling an epileptic seizure, but without the characteristic electrical discharges associated with epilepsy. Instead, PNES are psychological in origin, and may be thought of as similar to...
- SaccadeSaccadeA saccade is a fast movement of an eye, head or other part of an animal's body or device. It can also be a fast shift in frequency of an emitted signal or other quick change. Saccades are quick, simultaneous movements of both eyes in the same direction...