What causes hyperekplexia?
Most cases of hereditary hyperekplexia are caused by mutations in the GLRA1 gene. The GLRA1 gene provides instructions for making one part, the alpha (α)1 subunit, of the glycine receptor protein. When this protein attaches (binds) to glycine, signaling between cells is stopped.
What causes startle effect?
The activation of the facial motor nucleus causes a jerk of the head while an activation in the spinal cord causes the whole body to startle.
What causes startle myoclonus?
Sensory sensitive: Myoclonus is triggered by a stimulus (eg, sudden noise, movement, light, visual threat), as can occur when a person is suddenly startled (startle response). Spontaneous: Myoclonus occurs without a trigger, as often occurs when the cause is metabolic.
What are the symptoms of hyperekplexia?
Symptoms
- Arching of the head in conjunction with the startle reaction.
- Jerking movements after the startle reaction or when trying to fall asleep.
- Severe muscle tension, which may be most noticeable in infants.
- Lack of movement or slower than normal movements in babies.
- Overactive reflexes.
- Intermittent apnea.
- Unsteady gait.
How common is hyperekplexia?
Hyperekplexia is a rare genetic disorder that is most often present at birth and affects both males and females. In some individuals, onset of the disorder may be delayed until adolescence or adulthood. Hyperekplexia affects approximately one in 40,000 people in the United States.
How do you treat hyperekplexia?
Treatment. Hereditary hyperekplexia is commonly treated with the anti-anxiety and anti-spastic drug clonazepam. Other medications which have been helpful for some people include carbamazepine, phenytoin, diazepam, valproate, 5-hydroxytryptophan, piracetam, phenobarbital, and fluoxetine.
Why do I have an increased startle response?
Increased startle responses are excessive or evoked by stimuli that would not be effective in most people. This is identified most easily by loss of habituation. Increased startle reflexes are characteristic of a variety of disorders, including hereditary hyperekplexia.
What type of disorder is associated with an increase in the startle reflex?
Hyperekplexia, otherwise known as familial startle disease, is an autosomal-dominant disorder characterized by an exaggerated startle reaction in response to sudden, unexpected auditory or tactile stimuli.
What causes the body to jump involuntarily?
A disturbance to the central nervous system (brain and spinal cord) most likely causes these involuntary muscle twitches. For unknown reasons, the central nervous system sends an electrical impulse to muscles. Rarely, myoclonus occurs after an injury to the peripheral nerves outside the central nervous system.
Is hyperekplexia curable?
Hyperekplexia is a treatable neurogenetic disease and clonazepam is the treatment of choice.
Is hyperekplexia genetic?
Affected Populations Hyperekplexia is a rare genetic disorder that is most often present at birth and affects both males and females. In some individuals, onset of the disorder may be delayed until adolescence or adulthood.
What is the genetic cause of hyperekplexia?
Most affected individuals have a mutation in either the GLRA1, SLC6A5 gene and have an affected parent. The genes that cause hyperekplexia are involved in the production of the glycine protein Glycine diminishes the action of nerve cells in the brain and spinal cord. It is known as an “inhibitor transmitter”.
What are the abnormal startle syndromes?
Abnormal startle syndromes are classified into hyperekplexia, stimulus-induced, and neuropsychiatric startle syndromes. Hyperekplexia is attributed to a genetic, idiopathic, or symptomatic cause. Hereditary hyperekplexia is a treatable neurogenetic disorder.
What are the causes of excessive startle after infancy?
The onset of excessive startle after infancy should direct investigations for an acquired cause such as brainstem injury, antibodies against glycine receptors, and neurodegeneration. Finally, one should not forget to evaluate unexplained cases of abnormal gait and frequent falls in adults for underlying undiagnosed startle syndromes.
What is an example of hyperekplexia?
For example, Jumping Frenchmen of Maine is a disorder characterized by an extreme startle reaction consisting of jumping, raising the arms, yelling, hitting, obeying sudden commands, or involuntarily repeating sentences. (People with hyperekplexia do not have the imitative repetition of words or actions,…