Branchial Myoclonus With Spastic Paraparesis And Cerebellar Ataxia

De Yebenes et al. (1988) described a syndrome of branchial myoclonus, spastic paraparesis, and cerebellar ataxia in 6 members of 2 generations of a family that lived in the province of Toledo in Spain. Male-to-male transmission occurred. Rhythmic myoclonus involving the palate, pharynx, larynx, and face was followed by truncal ataxia and spastic paraparesis. Age of onset ranged from 40 to 50 years. Computerized tomography and magnetic resonance imaging showed mild atrophy of the cerebral and cerebellar cortex and severe atrophy of the medulla and spinal cord. The pons appeared normal, and the olives did not seem hypertrophic. Reduction of the serotonin metabolite 5-hydroxyindoleacetic acid was found in the cerebrospinal fluid. Treatment with 5-hydroxytryptophan and carbidopa at maximal tolerated doses improved ataxia mildly but did not modify the myoclonus. Treatment with other agents was unsuccessful. The clinical symptoms were progressive, leading to death or severe disability 5 to 10 years after onset of the disease. Branchial myoclonus is rare but has been observed with a variety of disorders including demyelinating disease, infarction, arteritis, neoplasm, and trauma involving the lower brainstem or the dentato-rubro-olivary pathways. Sperling and Hermann (1985), Leger et al. (1986), and Sasaki et al. (1987) described branchial myoclonus in patients with spinocerebellar degeneration and olivopontocerebellar atrophy, but de Yebenes et al. (1988) thought that the disorder in their family was different from that reported in any of these 3 publications.

Howard et al. (1993) described a Kuwaiti family that came to attention because of 2 sisters and a brother, out of a sibship of 10, who presented with a progressive neurologic disorder beginning in the third decade of life and characterized by palatal myoclonus, nystagmus, bulbar weakness, and spastic tetraparesis. There was no evidence of intellectual deterioration or seizures. CT scan showed marked brainstem atrophy in 2 patients and basal ganglia calcification in 1. MRI scan in 1 showed high signal in the brainstem and periventricular region, and cerebral biopsy in this patient showed myelin loss and the presence of Rosenthal fibers, which are particularly characteristic of Alexander disease (203450). A similar disease affected the mother, who died at age 45, a maternal aunt, who died at age 50, and 2 daughters of the aunt who were still living. Howard et al. (1993) suggested autosomal dominant inheritance. It may be noteworthy that the parents of the 3 sibs were consanguineous, as were also the parents of the 'mother' and 'maternal aunt.' Palatal myoclonus, which also occurs in Machado-Joseph disease (109150) and in spinocerebellar ataxia type 2 (183090), is characterized by rhythmic oscillations of the soft palate. It is also called branchial myoclonus because it may be associated with synchronous contractions of muscles derived from the branchial arches, including the diaphragm, tongue, and sternomastoids.