What Is It? An acoustic neuroma is a type of benign
(noncancerous) brain tumor that grows on the vestibular nerve as
it travels from the inner ear to the brainstem. It is one of the
most common types of benign brain tumors. The first sign of one
is usually hearing loss. The cochleo-vestibular nerve (also
called the eighth cranial nerve) is made up of three nerves that
connect the inner ear to the brain. One branch -- the cochlear
nerve -- carries hearing information. The other two branches --
the inferior and superior vestibular nerves -- carry balance
information to the brain. The nerves are wrapped in a layer of
specialized cells called Schwann cells. An acoustic neuroma --
also called a vestibular schwannoma -- is a tumor of those
cells. If an acoustic neuroma is not diagnosed or treated, it
can grow large enough to press on important structures in the
brainstem and cause major life-threatening problems. The main
symptoms of an acoustic neuroma are hearing loss and tinnitus
(ringing in the ears). They are