My grandson is 12 and was diagnosed with large vestibular aqueduct syndrome some years ago. What is it? What treatments are available? He loves sports -- are there any dangers from falls or bumps to the head?

G.W.

The vestibular aqueduct is a very narrow channel that connects two spaces in the head: the inner ear ("vestibule") and the cranial cavity. "Enlarged vestibular aqueduct (EVA) syndrome" is defined as a vestibular aqueduct larger than 1.5mm (about 1/17 inch) as seen on a CT scan of the skull base.

EVA syndrome is usually associated with some degree of hearing loss in the affected ear. The hearing loss may be present at birth, or it may develop later in childhood. A typical story is that of a child who sustains a sudden loss of hearing following head trauma (which may be relatively minor), strenuous exertion or a sudden change in barometric pressure. Hearing worsens gradually, and profound deafness is, unfortunately, a fairly common end result. EVA in both ears (bilateral) is twice as common as EVA in only one ear. If the child has bilateral EVA, the parents must anticipate the possibility of a serious hearing disability in their child's future.

Given the frequent reports of hearing loss associated with head trauma in EVA syndrome, I recommend that children with EVA syndrome avoid contact sports. The exception to this would be the child with EVA on one side only who has already lost all useful hearing in the affected ear. Such a child has nothing left to lose, and thus does not need to restrict his or her activities. On the other hand, if the child has bilateral EVA and still has useful hearing in one (or both) ears, activity restriction is prudent.

What treatments are available? Attempts have been made to surgically alter the inner ear in these children, in the hope of preventing further hearing loss. The results of these attempts have been dismal. One promising development has been the use of cochlear implantation for persons with EVA who have a profound hearing loss in the affected ear. (Cochlear implantation is an operation in which an electrode is placed into the patient's cochlea, in the inner ear. In response to sound, the electrode directly stimulates the cochlea. This operation does nothing to "cure" the basic defect of EVA, but it does address the hearing loss.) In August 1999, a group of doctors in the United Kingdom published the results of cochlear implantation in five adults and two children with EVA syndrome. Their results were very promising.