Anatomy & Physicology

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The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and balance information from the inner ear to the brain. This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain. It consists of the cochlear nerve, carrying information about hearing, and the vestibular nerve, carrying information about balance. It emerges from the medulla oblongata and exits the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone. ...

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Nội dung Text: Anatomy & Physicology

Anatomy & Physicology The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and balance information from the inner ear to the brain. This is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain. It consists of the cochlear nerve, carrying information about hearing, and the vestibular nerve, carrying information about balance. It emerges from the medulla oblongata and exits the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone.
Cause: An acoustic neuroma, sometimes called a vestibular schwannoma is a benign tumor that is located on the 8th cranial nerve which leads from the inner ear to the brain. The auditory nerve cells, like many nerve cells in the brain and spinal cord, are wrapped or insulated by layers of specialized cells called Schwann cells. A gene on chromosome 22 directs Schwann cells to produce merlin, a protein which is also called schwannomin. Merlin acts as a tumor suppressor preventing Schwann cells from rapidly dividing in an uncontrolled manner. When there is an abnormality or mutation of the gene, the merlin which is produced is nonfunctional and this enables the Schwann cells to rapidly multiply and form a tumor. Symptoms: The early symptoms of an acoustic neuroma may include one or more of the following:
• Hearing loss • Tinnitus • Vertigo • Facial numbness When the tumour keep growing. Once it runs out of space in side the small canal that links the inner ear to the brain, it begins to grow into the skull cavity. The tissue at the base of the brain, including a structure called the brain stem, may become squashed by the growing tumour. Symptoms of advanced acoustic neuroma can include: • Headache • Vomiting • Pain in the face • Facial numbness • Facial twitches • Visual disturbances, such as double vision • Dysphagia
Diagnosis: The earlier the tumour is detected and treated, the greater the odds of a full recovery. Acoustic neuroma can be diagnosed using a variety of tests, including: • Computed tomography (CT) scan – a specialised x-ray that takes three- dimensional pictures of the inner ear. However, small tumours may be missed by this method. • Magnetic resonance imaging (MRI) scan – pictures of the inner ear are taken, using radio waves in a strong magnetic field instead of x -rays. MRI scans can usually detect smaller acoustic neuromas than CT scans. A dye may be injected to further highlight the tissues under investigation.