Tapetoretinal Degenerations in Spinocerebellar Degenerations (Heredoataxias)

Late-onset cerebellar degeneration in mice induced transplacentally by methylnitrosourea

A late-onset degenerative disease in the cerebellum was produced in the offspring of mice exposed to 1 mg/kg of the direct-acting DNA alkylating agent methylnitrosourea (MNU) on day 16 of gestation. This intrauterine exposure to MNU also provoked a progressive retinal degeneration that was described elsewhere. Mild ataxia in the MNU-exposed animals was expressed by 20 weeks of age. Although animals appeared normal in the immediate post-natal period, quantitative histological evaluation of cerebellar coronal sections indicated that MNU-exposed animals had a significantly greater number of pyknotic Purkinje cells than age-matched controls. The number of pyknotic Purkinje cells declined with age in the drug exposed animals; however, the percentage of pyknotic Purkinje cells to total number of Purkinje cells still was greater in MNU-induced animals at 36 weeks than in controls, suggesting that a slow degenerative process was ongoing in the MNU-exposed animals. Furthermore, the folia were grossly disrupted in 90% of the older MNU-exposed animals (ages greater than 12 weeks), suggesting permanent cerebellar disruption macroscopically. Such intrauterine exposure to low doses of alkylating agents may be potentially useful in modeling degenerative neuronal diseases.

A syndrome of congenital retinal dystrophy and saccade palsy--a subset of Leber's amaurosis

Three children who presented in infancy with a severe visual defect and absent or barely recordable electroretinograms, with relatively well preserved visually evoked cortical potentials, were subsequently found to have vertical and horizontal saccade palsies with head thrusts but relatively good visual acuity. These children, who were clearly different from other infants with congenital retinal dystrophy, were also developmentally delayed and had systemic motor and speech defects, but their visual prognosis was relatively good. The recognition of their saccade palsy was delayed because their poor visual attention in infancy was ascribed purely to the tapetoretinal degeneration. We consider these patients represent a clear subset of those patients who are diagnosed as having congenital retinal dystrophy or Leber's amaurosis.

Charcot-Marie-Tooth disease associated with retinal pigment dystrophy and protanopia. Neurological, ophthalmological and genetic study of a family

Neurological, ophthalmological and genetic investigations were performed on a family, a member of which presented with a rare association of tapeto-retinal degeneration, protanopia and Charcot-Marie-Tooth disease (CMT), and asked for genetic counseling. The neurological enquiry was completed by measurement of motor nerve conduction velocity in several completed by measurement of motor nerve conduction velocity in several members of the family. The propositus was submitted to a muscle biopsy. The ophthalmological examination included ophthalmoscopy, fluorescein angiography, electroretinogram and electrooculogram. The propositus, a woman aged 40, had typical CMT disease and her father also had a mild form of it. She had protanopia as had her father, her son and her nephew. In addition she had large macular pigmented changes, described as retinal dystrophy, "flavus flavimaculatus." Her mother had only senile pigmented modification of the fundus and her three daughters had mild macular pigmented changes, like "salt and pepper." Two genes are probably involved: one for protanopia with X linked recessive inheritance, the other responsible of CMT and tapeto-retinal degeneration, with an autosomal dominant inheritance, giving a 50% risk of recurrence.

Retinitis pigmentosa

The authors review the symptomatic and genetic aspects of the various entities of isolated retinitis pigmentosa (R.P), both in its typical form and in the forms associated with the affection of other ocular tissues. Syndromes in which R. P. is associated with the affection of other organs and systemic disorders are also cconsidered. Origin, diagnosis and the course of the disease are discussed with regard to electrophysiology, histopathology, fluorescein angiography and biochemistry. Animal research has provided new realizations about the ultrastructure and physiological mechanisms of retinal photoreceptors, and better understanding of abnormal changes. The possible pathogenesis of the human disease, based on research findings, is onsidered. Although R.P. is generally thought to be to be an "untreatable" disease, therapy may be effective in several pathological entities. Methods and results of therapy with vitamins, light deprivation and vision aids are discussed.