Usher Syndrome

A genetically heterogeneous condition associating retinitis pigmentosa and deafness. The age of onset varies. Multiple subtypes have been described.

Retinitis Pigmentosa-Deafness Syndrome.

Prevalence in the general population varies from 1:20,000 to 1:30,000 in Europeans.

This medical entity was described by Charles Usher, a British ophthalmologist, in 1914, who emphasized the hereditary nature. However, the earliest description was given by Albrecht von Graefe in 1858, who commented on a relatively high frequency in Jews in Berlin.

Autosomal recessive.

Magnetic resonance imaging (MRI) has demonstrated characteristic morphological abnormalities of the central nervous system. These abnormalities vary according to the syndrome subtype. Twelve independent loci with six known genes have been reported.

The combination of retinitis pigmentosa, sensorineural deafness, abnormal vestibular function, mental retardation, psychosis, and cerebellar ataxia lead to the diagnosis of Usher syndrome. Age of onset of visual disturbance is variable depending on the subtype.

It should be emphasized that this is a heterogeneous condition and mental retardation is variable from normal to severe. Vision may be lost in late or early childhood.

Type I (USH I) is characterized by a congenital severe to profound preverbal deafness present at birth, absent vestibular deterioration function, and early onset of retinitis pigmentosa-like deterioration (typically by the age of 5 or 6 years and almost always by the age of 10 years). Different entities of USH I have been described, but cannot be currently differentiated on a clinical basis. It is also known as the French-Acadien (“Cajun”) of Louisiana (chromosome 11p) and the French variety (chromosome 11q).

Type II (USH II) has a milder postverbal hearing loss, apparently present from birth and slowly evolutive (some suggests 1 decibel/per decade of life) and a later onset of retinitis pigmentosa-like retinal degeneration (typically between the ages of 10 and 20 years). Vestibular functions are normal and stable.

Type III (USH III) is a controversial form of Usher syndrome. It is more frequent (40% of patients) in eastern Finland, and is distinguished from USH II by its later onset with rapid and progressive hearing loss and retinal degeneration. There is good genetic evidence that the gene for USH III is located on a different chromosome than the genes for USH I and USH II.

In view of the variety of presentations, each case has to be treated individually. In all cases, hearing and visual function have to be evaluated.

Patients may be profoundly deaf and blind, and this combination makes communication potentially very difficult, especially during induction of anesthesia and for the immediate postoperative care. There are no specific anesthetic techniques to recommend.

Consideration must be given to medication, particularly the use of aminoglycosides in patients affected with Usher syndrome types II and III. Psychosis and bipolar affective disorder are common in this group of patients, and many will be receiving psychotropic medication, including major tranquilizers, lithium, or antidepressants. Considerations for potential interactions with anesthetic agents must be reviewed.