Geniospasm 1

Description

Geniospasm is characterized by spontaneous intermittent involuntary quivering or trembling of the chin that is intensified by stress or anxiety. The movements are first noticed in infancy or childhood and usually abate by late adulthood (Wadlington, 1958; Danek et al., 1991).

Clinical Features

Wadlington (1958) found geniospasm (trembling chin) with no associated neurologic or other abnormalities in 8 members of 3 generations of a family. Anxiety or emotional upset was a trigger mechanism and tranquilizing and anticonvulsant agents reduced the attacks. Attacks were observed as early as 2 months of age. There was no instance of male-to-male transmission and all 3 daughters of the 1 male with children were affected. Other families with trembling chin had been reported by Grossman (1957), Frey (1930) and Ganner (1938), and the families reported by Stocks (1922) and by Goldsmith (1927) with facial spasm (134300) probably had trembling chin. Male-to-male transmission occurred in some of these families. The condition was probably first reported by Massaro (1894), who described 26 cases in 5 generations of a Sicilian family. He used the designation geniospasm (in analogy to blepharospasm) for the observed intermittent, sudden, involuntary clonic contractions that were triggered by strong emotion and limited to the transverse muscles of the chin. The contractions never occurred during sleep.

Laurance et al. (1968) described 2 families. The condition ameliorated with age.

Danek et al. (1991) found reports of a total of 18 families since the publication of Massaro (1894). They noted that the quivering of the skin over the chin is intermittent and may be either spontaneous or stress-induced. Danek et al. (1991) described a family from upper Bavaria in which 13 members of 4 generations were affected. They referred to the disorder in German as 'Kinnmuskelzittern.'

The clinical characteristics of 2 British families studied by Jarman et al. (1997) were described by Soland et al. (1996). Affected individuals experienced characteristic involuntary up- and down-movement of the tip of the chin, with a superimposed quivering activity and movement of the lower lip. Episodes of geniospasm frequently were precipitated by stress, concentration, or extremes of emotion or occurred spontaneously, particularly in young children, and usually lasted several minutes. In all cases, the onset of symptoms was in infancy or early childhood, and, in 1 family member, geniospasm was observed as early as hours after birth. Attacks became less frequent as the subjects aged, the highest frequency occurring during childhood and adolescence. Some affected individuals in 1 family suffered from nocturnal involuntary tongue biting during early childhood; the disorder in this family was mapped to chromosome 9 (see MAPPING section). There were no other associated neurologic abnormalities.

Destee et al. (1997) described a French Caucasian family with affected individuals in 4 generations, including 1 instance of male-to-male transmission. In the 35-year-old index case, the anomaly had been present since birth, constantly during childhood, and thereafter episodically, lasting a few minutes. It occurred particularly in stressful situations, such as playing videogames or during working hours when meeting customers. It was described as a tremulous movement of the chin, but the man said that he had once noted abnormal involuntary movement spreading to the upper lip. During periods of severe stress, the abnormal involuntary movement was so great that it was present during sleep and sometimes woke him up. He was unable to initiate or suppress it. Neurophysiologic recording showed that the movement was not sinusoidal and that there was an interval between each movement. Destee et al. (1997) suggested that the involuntary movement cannot be considered a tremor but should rather be classified as hereditary chin myoclonus, i.e., a focal variant of hereditary essential myoclonus.

Diaz et al. (1999) stated that 23 families with chin tremor/myoclonus had been reported. They reported the first affected Latin American family, in which 28 of 63 members were affected in 4 generations. The index case was a 63-year-old woman who first presented with chin quivering in early childhood. Symptoms developed gradually without affecting chewing, swallowing, or speech articulation. Tremor disappeared during sleep and worsened with stress. Tremor was often triggered by gazing at flying objects, as was the case in several other affected family members. The movement disorder improved spontaneously, although not entirely, from ages 15 to 30, only to recur later and plateau in the mid-fifties. Even at peak severity, the tremor represented little more than a cosmetic impairment. Neurologic examination was otherwise normal.

Inheritance

Massaro (1894) noted a 'direct' mode of transmission of geniospasm; when the disorder skipped a generation, it did not appear in subsequent generations.

Reports of male-to-male transmission (e.g., Destee et al., 1997) suggest autosomal dominant inheritance of geniospasm.

Mapping

In a 4-generation British family with hereditary geniospasm, Jarman et al. (1997) conducted a genomewide genetic linkage study and obtained positive 2-point lod scores for 15 microsatellite markers on the pericentromeric region of chromosome 9. A maximum 2-point lod score of 5.24 at theta = 0.0 was obtained for the marker D9S1837. Construction of haplotypes defined the interval of 2.1 cM between flanking markers D9S1806 and D9S175, thus assigning the locus for geniospasm in this family to 9q13-q21. Hereditary geniospasm in a second British family was not linked to this region, indicating genetic heterogeneity.