Hyperekplexia

Hyperekplexia, also known as startle disease or startle syndrome, is a rare neurological condition where a person has an exaggerated startle response to unexpected stimuli such as sudden noises, touches, or movements. While everyone startles to some degree, people with hyperekplexia have a much stronger and more prolonged reaction. This can include sudden stiffening of the body (especially in newborns), jerking movements, and sometimes falling down without losing consciousness. In newborns, the condition often presents as severe stiffness (hypertonia) that can be so intense it may be mistaken for seizures. Babies may have episodes of stiffness that can interfere with breathing, which can be dangerous if not recognized and managed quickly. As children grow, the stiffness typically improves, but the excessive startle response usually continues into adulthood. Some individuals may also experience unsteadiness when walking and occasional falls triggered by the startle episodes. The condition is caused by problems with glycine receptors or glycine transport in the brain and spinal cord. Glycine is a chemical messenger that helps calm nerve signals. When this system does not work properly, the nervous system overreacts to stimuli. Treatment is available and often very effective. The medication clonazepam, a benzodiazepam, is the most commonly used treatment and can significantly reduce startle episodes and stiffness. Early diagnosis and treatment are important, especially in infants, to prevent complications from breathing difficulties during stiffness episodes.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Bring these to your next appointment

• Q1.Is my child's startle response consistent with hyperekplexia, and has epilepsy been ruled out?,Should we pursue genetic testing, and which genes should be tested?,What is the correct dose of clonazepam for my child's age and weight, and how should it be adjusted over time?,Can you teach me the Vigevano maneuver for emergency stiffness episodes?,What should I do if my child stops breathing during an episode?,Will the symptoms improve as my child gets older?,Are there any activities or environments my child should avoid to reduce startle triggers?

Common questions about Hyperekplexia

Related conditions

Other rare diseases commonly researched alongside Hyperekplexia.

• Hereditary spastic paraplegia→