What is Norrie Disease and what are the audiologic and/or vestibular findings associated with this disorder?
Norrie Disease is a rare medical condition primarily known for its ocular symptoms. This X-linked recessive inherited disease causes irreversible blindness at or very soon after birth. Partial or complete retinal detachment usually occurs first with a variety of other ocular conditions following. A vascular mass behind the lens results from immature retinal cells filling up space at the back of the eye. Cataracts, iris atrophy, adhesions, corneal opacification, and reduction of globe size are typical during the course of the disease. Eye pain may result. Hearing impairment, as well as cognitive, developmental, mental, behavioral, and medical problems are also known to occur in some individuals diagnosed with this condition.
Mutations or deletions in the NDP gene are believed to cause Norrie Disease. The gene provides instructions to a protein called norrin. Norrin protein is thought to regulate the vascularization of the retina, cochlea, and other systems. Interference with the norrin protein affects the systems and the development and health of supporting structures.
Sensorineural hearing loss occurs in 30% or more of individuals with Norrie Disease. The vasculature to the cochlea is believed to be affected resulting in stria vascularis dysfunction and hearing loss. The loss typically begins in childhood. It often begins as a mild, asymmetric loss progressing to a more severe, symmetrical loss by the individual's third decade of life. Though vestibular disorders have not been reported in the literature, it is plausible that the vascular and development issues described for the eye and hearing systems may also impact the vestibular system.
Appropriate medical care and early intervention can help assist the individual with Norrie Disease make gains in development. Communication options, hearing aids, cochlear implants, and aural rehabilitation can be explored in relation to the patient's current needs and prognosis.
Websites related to Norrie Disease: www.norries.org and ghr.nlm.nih.gov/condition=norriedisease
Cindy B. Pichler, Au.D., has been an audiologist for more than 20 years. She specializes in pediatric diagnostic audiology in Chicago, Illinois and works with many families who have children with diseases and syndromes that effect hearing and balance. Dr. Pichler serves on the advisory boards of the Healthy Hearing Journal and AudiologyOnline and the Review Board for Audiology Online. She can be contacted via the Audiology Online website.