Hereditary chin tremors or geniospasm indicates a hereditary condition in which you suffer from a twitching muscle in the chin and in some cases the lower lip also twitches. Hereditary geniospasm is a movement disorder that comes and goes; you experience episodes of involuntary twitching of the chin (and lower lip). The complaints can last from a few seconds to hours and can occur spontaneously or be triggered by stress and tension. Chin tremors usually first appear in childhood and usually diminish with age. Geniospasms are inherited in an autosomal dominant pattern. Although the exact gene that causes the condition is still unknown in 2023, it is known that it is caused by an error in the hereditary material of chromosome 9. It appears that botulinum toxin can reduce the symptoms.
- Hereditary chin tremors or geniospasm
- Synonyms
- Prevent
- Causes
- Symptoms
- Examination and treatment
- Therapy
- Prognosis
- Prevention
Chin muscle (mentalis muscle) / Source: Anatomography, Wikimedia Commons (CC BY-SA-2.1)
Hereditary chin tremors or geniospasm
Geniospasm refers to an involuntary tremor of the mentalis muscle or chin muscle. Tremor means shaking, trembling, and it refers to a rhythmic, trembling, involuntary movement that occurs when muscles repeatedly contract and then relax. It usually occurs in childhood and is inherited as an autosomal dominant trait. Each child has a 50% chance of inheriting the condition if one of the parents has the condition. This shaking of the chin muscle looks like shaking of the chin.
Synonyms
Hereditary chin shaking is also known as hereditary geniospasm or chin myoclonus. Myoclonus refers to a brief, involuntary contraction of a muscle or group of muscles.
Prevent
In 2023 it is not known how often this condition occurs. It is a rare condition and not everyone with this complaint will visit their GP.
According to Orphanet, the condition has been described in fewer than 25 families in Europe and the US, with a slightly higher incidence in men than women (male to female ratio of 1.3:1).[1]
Causes
Geniospasm is inherited as an autosomal dominant trait and has been attributed in the literature to chromosome 9q13-q21.[2] However, there are also cases where the condition occurred spontaneously.
Symptoms
Geniospasm is manifested by involuntary trembling of the chin and sometimes also the lower lip (twitching lower lip). It can be triggered or aggravated by stress and emotions and can also occur during sleep but usually does not. The shaking comes and goes and it is not always clear why it occurs or recurs at a certain time. Other neurological disorders or complaints are not part of the clinical picture. However, the tremors can be felt by others and may cause the person to withdraw from social activities. You can usually eat and talk normally despite your chin (and lower lip) shaking.
Examination and treatment
Hereditary chin tremors can be diagnosed based on a clinical evaluation performed by a doctor, for example a neurologist who specializes in movement disorders.
Therapy
Hereditary chin tremors or geniospasm do not always need to be treated with medication; Many people benefit from knowing what causes the shaking and learning to live with it. If desired, medications can be prescribed that reduce shaking, such as benzodiazepines and anticonvulsants. However, you may not respond to the medications. Significant side effects may be experienced if a combination of medications is used. Very good results have been achieved with botulinum toxin injections into the mentalis muscle or chin muscle, which paralyze the muscle but do not restrict facial muscles or speech in any way.
Prognosis
Most geniospasms occur in childhood. Improvement may occur with age.
Prevention
In 2023, there is no known way to prevent it.
Notes:
- Orphanet. Hereditary geniospasm. https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=53372 (accessed on 11-10-2020)
- Jarman, P. R., Wood, N. W., Davis, M. T., Davis, P. V., Bhatia, K. P., Marsden, C. D., & Davis, M. B. (1997). Hereditary geniospasm: linkage to chromosome 9q13-q21 and evidence for genetic heterogeneity. American journal of human genetics, 61(4), 928–933. https://doi.org/10.1086/514883