Hyperekplexia
Hyperekplexia
Hyperekplexia (literally, to jump excessively) is an involuntary movement disorder in which there is a pathologically exaggerated startle response, usually to sudden unexpected auditory stimuli, but sometimes also to tactile (especially trigeminal) and visual stimuli. The startle response is a sudden shock-like movement which consists of eye blink, grimace, abduction of the arms, and flexion of the neck, trunk, elbows, hips, and knees. The muscular jerk of startle satisfies the definition of myoclonus.
Ideally for hyperekplexia to be diagnosed there should be a physiological demonstration of exaggerated startle response, but this criterion is seldom adequately fulfilled.
Hyperekplexia syndromes may be classified as:
- Idiopathic: the majority
- Hereditary/familial:
An autosomal dominant disorder with muscular hypertonia in infancy, leg jerks and gait disorder. Familial cases have been associated with mutations in the α1 subunit of the inhibitory glycine receptor gene
- Symptomatic:
perinatal ischemic-hypoxic encephalopathy brainstem lesions (encephalitis, hemorrhage) thalamic lesions (inflammation, vascular) drugs (cocaine, amphetamines)
Gilles de la Tourette syndrome
Attacks may respond to the GABA agonist clonazepam.
References
Matsumoto J, Hallett M. Startle syndromes. In: Marsden CD, Fahn S (eds.) Movement disorders 3. Boston: Butterworth, 1994: 418-433
Shiang R, Ryan SG, Zhu Y-Z, et al. Mutational analysis of familial and sporadic hyperekplexia. Annals of Neurology 1995; 38: 85-91
Cross References
