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Spinocerebellar ataxia type 7 (SCA7)
  1. Melanie Walker,
  2. Donald Farrell
  1. Melanie Walker, Donald Farrell University of Washington Medical Center, Seattle, WA, USA
  1. Correspondence to:
 Dr M Walker, Department of Neurology, University of Washington School of Medicine, Harborview, Medical Center, Box 359775, 325 9th Avenue, Seattle, WA 98104, USA;
 walkerm{at}u.washington.edu

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In 1937, French physicians described three generations of a family with a particularly aggressive degenerative cerebellar and ophthalmological disease.1 Since then many similar patients have been described with progressive cerebellar ataxia and retinal dystrophy resulting in progressive central visual loss and eventually blindness. Before the availability of genetic classification of the spinocerebellar ataxias, this condition was generally known as olivopontocerebellar ataxia (OPCA) type II or III.2 In 1995, the heritable defect was mapped to chromosome 3p.3 The prevalance of the disease is less than one per 100 000 population, with spinocerebellar ataxia type 7 (SCA7) representing less than 2% of all SCAs.4 Worldwide, SCA7 is among the rarest forms of autosomal dominant cerebellar ataxia that is genetically verifiable, except in Sweden and Finland where it is one of the more common ataxias documented.5

CASE REPORT

An 11 year old girl presented to our clinic for evaluation of developmental delay and neurological symptoms. She had developed normally until the age of five when she was noted to have mild visual loss. At the age of nine, she was found to have pigmentary degeneration of the retina, beginning in the macular region. On neurological examination she had sluggish extraocular movements, normal motor tone and strength, normal sensation, a broad based gait, and flexor plantar responses. An electroencephalographam did not show any epileptiform discharges or focal slowing. Electromyography and nerve conduction velocities were normal. Two skin biopsies showed no evidence of storage disease by electron microscopy. At that time, magnetic resonance imaging was not available for clinical use but the brain CT was normal. A family history of ataxia in her paternal grandmother was obtained at the initial consultation. The patient progressively developed bilateral blindness due to pigmentary retinal degeneration, dementia, and severe ataxia confining her to a wheelchair.

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