Geniospasm is movement disorder of the mentalis muscle.
| Geniospasm | |
|---|---|
| Other names | Hereditary geniospasm |
 | |
| Mentalis muscle | |
| Specialty | Neurology |
It is a benign genetic disorder linked to chromosome 9q13-q21[1] where there are episodic involuntary up and down movements of the chin and lower lip. The movements consist of rapid fluttering or trembling at about 8 Hz superimposed onto a once per three seconds movement of higher amplitude and occur symmetrically in the V-shaped muscle. The tongue and buccal floor muscles may also be affected but to a much lesser degree.[citation needed]
The movements are always present but extreme episodes may be precipitated by stress, concentration or emotion and commence in early childhood.[citation needed]
The condition is extremely rare and in a study in 1999 only 23 families in the world were known to be affected,[citation needed] although it may be under-reported. Inheritance is aggressively autosomal dominant. In at least two studies the condition appeared spontaneously in the families.[citation needed]
The condition responds very well to regular botulinum toxin injections into the mentalis muscle[2] which paralyse the muscle but cause no impairment of facial expression or speech.
References
edit- ^ Jarman PR, Wood NW, Davis MT, et al. (1997). "Hereditary geniospasm: linkage to chromosome 9q13-q21 and evidence for genetic heterogeneity". Am. J. Hum. Genet. 61 (4): 928–33. doi:10.1086/514883. PMC 1715984. PMID 9382105.
- ^ Gonzalez-Alegre P, Kelkar P, Rodnitzky RL (2006). "Isolated high-frequency jaw tremor relieved by botulinum toxin injections". Mov. Disord. 21 (7): 1049–50. doi:10.1002/mds.20878. PMID 16602105. S2CID 34811999.
External links
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