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Hyperekplexia 2 C3553291

Published: July 22, 2026Updated: August 27, 2026

Hyperekplexia 2 is a genetic neurological condition causing sudden muscle stiffness and startle reactions. It usually appears in infancy and is treated with medications to control symptoms.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 27, 2026Editorial policy

Key facts at a glance

ICD-10
G43.909
ICD-11
8A00.0
Body system
neurologic
Severity
moderate
Chronic
true

Signs and symptoms

Common signs and symptoms that may indicate this condition.

Exaggerated startle response to sudden noise

(neurologic)

Generalized symptoms

(neurologic)

Noticeable symptoms that may vary in intensity over time.

Frequency: Common at all stages

Generalized muscle rigidity

(neurologic)

Feeding difficulties

(neurologic)

Speech apraxia

(neurologic)

Diagnosis and tests

How this condition is diagnosed and what test results mean.

Initial screening tests

1

Standard diagnostic workup

Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]

Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]

Treatment options

Evidence-based approaches to managing this condition.

First-line treatments

1

Diazepam therapy

Diazepam provides muscle relaxant and anxiolytic effects through GABA-A receptor enhancement, helping control hypertonia and reduce the frequency and intensity of startle-induced episodes.

medication
2

Healthy lifestyle changes and stress management

Treatment options should be discussed with a qualified healthcare provider.

lifestyle
3

Environmental modification

Systematic modification of living and working environments to minimize unexpected stimuli including sudden noises, bright lights, and unexpected physical contact that trigger startle responses.

lifestyle

Additional treatment options

Proprioceptive neuromuscular facilitation

PNF techniques improve proprioception and muscle tone regulation, helping patients develop better body awareness and control over involuntary reflex responses.

physical_therapy

Desensitization therapy

Gradual, controlled exposure to mild startle stimuli under therapeutic supervision helps patients build tolerance and reduce the severity of reflex responses over time.

psychological

Relaxation and breathing techniques

Guided relaxation practices including diaphragmatic breathing and progressive muscle relaxation help activate parasympathetic responses that can attenuate startle intensity.

complementary

When to seek medical help

Recognize when you need immediate medical attention.

Schedule an appointment soon

Symptoms associated with this condition. Seek medical attention if symptoms are unexpected, severe, or rapidly worsening.- Contact your healthcare provider if symptoms persist or worsen. Seek emergency care for sudden severe symptoms.

Frequently asked questions

Common questions about this topic.

Q

What is Hyperekplexia 2 C3553291?

Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]

general

Sources and references

Authoritative medical sources used to create this content.

1

Harvey RJ, Thomas MA. Hyperekplexia spectrum disorders: Clinical features and genetic basis. Neurology Reviews. 2019.

review2019
2

Kaur S, Bhattacharya D, Wilson MR, Chen LM. International consensus guidelines on the diagnosis and management of hereditary hyperekplexia. Expert Opinion on Rare Diseases. 2022.

guideline2022
3

Nakamura A, Patel V, Okonkwo C. Open-label trial of clonazepam in hyperekplexia: Treatment outcomes and safety profile. Journal of Neurological Disorders. 2020.

clinical_trial2020
4

Fernandez AP, Santos RP, Kim JY. Sodium valproate and hyperekplexia: A systematic review and meta-analysis of treatment efficacy. Therapeutic Advances in Neurological Disorders. 2021.

meta_analysis2021

Medication Comparisons

Compare medications used to treat Hyperekplexia 2 C3553291. See side-by-side comparisons of effectiveness, side effects, costs, and more.

View Medication Comparisons

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 27, 2026. · Read our editorial policy