What is Geniospasm?
Geniospasm is a rare, benign hereditary movement disorder of the mentalis muscle characterized by involuntary, episodic up and down movements (tremors) of the lower lip and chin. Geniospasm is linked to chromosome 9q13-q21. Patients with geniospasm experience rapid trembling or fluttering of the lower lip and chin. The buccal floor muscles and tongue can also be affected; however, to a lesser extent.
What are the Other Names of Geniospasm?
Geniospasm is also known as hereditary geniospasm; GSM 1; Trembling chin; and hereditary chin tremor / myoclonus; and hereditary essential chin myoclonus.
What are the Causes of Geniospasm?
As mentioned before, geniospasm is thought to be inherited in an autosomal dominant pattern; however, the exact gene which causes geniospasm is not known. It is thought that mutations or changes in a gene on chromosome 9 can lead to development of geniospasm in some families.
Geniospasm is an extremely rare condition; however, it is also thought that this condition may be under-reported. The inheritance of Geniospasm is aggressively autosomal dominant.
What are the Symptoms of Geniospasm?
Geniospasm is characterized by tremors which are involuntary movements of the lower lip and chin. The tremors of Geniospasm can be present for a few seconds to a few hours. Geniospasm can also involve buccal floor muscles and tongue, but to a lesser degree.
How Long Does an Episode of Geniospasm Last & At What Age Does Geniospasm Develop?
The movements of Geniospasm are always present in the patient; however, they get exacerbated by any type of emotion, concentration or stress. Geniospasm starts in early childhood of the patient. The episodes of Geniospasm can last from a few seconds to few hours. Geniospasm can develop spontaneously or can be triggered by stress. Geniospasm commonly occurs in infancy or childhood and its frequency tends to decrease as the patient gets older age.
How is Geniospasm Diagnosed?
There are no specific laboratories which offer genetic testing for diagnosis of geniospasm. Geniospasm can be diagnosed by clinical evaluation of the patient by a health care professional, such as a neurologist who is a specialist in movement disorders.
What is the Relationship between Genetics & Geniospasm?
Geniospasm is inherited in an autosomal dominant pattern, which means that if the patient has only one mutated copy of the defected gene, then it is enough to produce symptoms in the patient. People, who have an autosomal dominant condition and go on to have children, will have 50% chances of their child inheriting the mutated gene copy. As there is a 50% chance for the child to inherit Geniospasm, there is a possibility of all the children getting affected with Geniospasm or none of the children will be affected with this disorder.
How is Geniospasm Treated?
Geniospasm is considered a benign disorder; however, this condition can cause embarrassment and treatment anxiety in some patients. Geniospasm improves significantly with age.
Geniospasm responds very well to regular botulinum toxin injections (Botox) given into the mentalis muscle. Botulinum toxin injections are the primary treatment for Geniospasm and these injections are also tolerated well and are effective. These injections will paralyze the muscles and stop the trembling of the lower lip and chin. There is no impairment of speech or facial expression with botulinum toxin injections.
Other than botulinum toxin injections, there are many drugs which can be used for treating Geniospasm, such as anticonvulsants and benzodiazepines. The result of the treatment for Geniospasm varies from patient to patient. Some patients with Geniospasm may not respond to a single drug and can experience considerable side effects if a combination of drugs is used.