This study will try to identify the genetic causes of hereditary hearing loss or balance
People with a hearing or balance disorder that affects more than one family member may be
eligible for this study. They and their immediate family members may undergo some or all of
the following procedures:
- Medical and family history, including questions about hearing, balance and other
ear-related issues, and review of medical records.
- Routine physical examination.
- Blood draw or buccal swab (brushing inside the cheek to collect cells) Tissue is
collected for DNA analysis to look for changes in genes that may be related to hearing
- Hearing tests The subject listens for tones emitted through a small earphone.
- Balance tests to see if balance functions of the inner ear are associated with the
hearing loss In one test the subject wears goggles and watches moving lights while cold
or warm air is blown into the ears. A second test involves sitting in a spinning chair
in a quiet, dark room.
- Photograph A photograph may be taken as a record of eye shape and color, distance
between the eyes, and hair color.
- Computed tomography (CT) and magnetic resonance imaging (MRI) scans These tests show the
structure of the inner ear. For CT, the subject lies still for a short time while X-ray
images are obtained. For MRI, the patient lies on a stretcher that is moved into a
cylindrical machine with a strong magnetic field. The magnetic field and radio waves
produce images of the inner ear. The radio waves cause loud thumping noises that can be
muffled by the use of earplugs.
Hereditary hearing impairment is a genetically heterogeneous disorder that can be caused by
mutations in any one of hundreds of different genes. Approximately 20 genes have now been
identified in which mutations can cause nonsyndromic sensorineural hearing loss. The
identification and analysis of these genes and their mutations are providing critical
insights into the development, structure, and function of the auditory system, as well as the
molecular mechanisms associated with disruption of these processes. In contrast, the
molecular mechanisms underlying familial disorders affecting peripheral vestibular function
appear to be more rare, have not been well described, and are less well understood. The
peripheral auditory and vestibular systems share many common features in both health and
disease, and many hereditary hearing loss disorders also affect vestibular function. The
purpose of this study is to identify genes and mutations causing hereditary disorders of
hearing, balance, or both. Members of families segregating hereditary disorders of hearing or
balance will be enrolled in the proposed study in order to: (1) define and characterize the
phenotypes and natural histories; (2) identify the underlying causative mutations and genes
by linkage, positional cloning, and/or candidate gene mutation analyses; (3) and correlate
observed phenotypes with the corresponding mutations and functions of the underlying genes.
- INCLUSION CRITERIA:
Persons with known SNHL and/or peripheral vestibular dysfunctions caused by genetic
Family members of persons with known SNHL and/or peripheral vestibular dysfunction caused
by genetic etiology
Adults must be able to provide informed consent
Minors must have a parent or guardian able to provide informed consent
Subjects must be 0-99 years of age
For Nigeria subjects with non-syndromic hearing loss, their hearing loss must be
early-onset, before 10 years of age, to be eligible.
Persons with SNHL and/or peripheral vestibular dysfunction caused by a nongenetic etiology
such as trauma, infection, metabolic or immunologic disorders, or exposure to ototoxic
agents such as noise or aminoglycoside antibiotics will not be included in this protocol.