Lesser Known Disorders
Each issue of this series contains at least three lesser known disorders. Some of these disorders may contain subtypes which will also be presented. You will also notice that each disorder has a code. These codes represent the coding system for all disabilities and disorders listed in the Educator’s Diagnostic Manual(EDM) Wiley Publications.
Disorders in this issue:
HI 7.00- Vestibular Schwannoma (Acoustic Neuroma)
Disability Category: Hearing Impairment
Definition
Vestibular schwannoma (also known as acoustic neuroma, acoustic neurinoma, or acoustic neurilemoma) is a benign, usually slow-growing tumor that develops from the balance and hearing nerves supplying the inner ear. The tumor comes from an overproduction of Schwann cells—the cells that normally wrap around nerve fibers like onion skin to help support and insulate nerves. As the vestibular schwannoma grows, it presses against the hearing and balance nerves, usually causing unilateral (one-sided) or asymmetric hearing loss, tinnitus (ringing in the ear), and dizziness/loss of balance (National Institute on Deafness and Other Communication Disorders, 2005a).
Diagnostic Symptoms
Diagnostic symptoms of Vestibular Schwannoma include (Mayo Clinic, 2004):
- Hearing loss in one ear
- Ringing (tinnitus) in the affected ear
- Dizziness
- Loss of balance
Further Key Points
Scientists are working to better understand how the gene works so they can begin to develop gene therapy to control the overproduction of Schwann cells in individuals with vestibular schwannoma. Also, learning more about the way genes help control Schwann cell growth may help prevent other brain tumors.
HI 7.01 Bilateral Vestibular Schwannomas
Disability Category: Hearing Impairment
Definition
A type of Vestibular Schwannomas that affects both hearing nerves and are usually associated with a genetic disorder called neurofibromatosis type 2 (NF 2). Half of affected individuals have inherited the disorder from an affected parent and half seem to have a mutation for the first time in their family (National Institute and Other Communication Disorders, 2004).
Explanation
Each child of an affected parent has a 50 percent chance of inheriting the disorder. Unlike those with a unilateral vestibular schwannoma, individuals with NF2 usually develop symptoms in their teens or early adulthood. In addition, patients with NF2 usually develop multiple brain and spinal cord related tumors.They also can develop tumors of the nerves important for swallowing, speech, eye and facial movement, and facial sensation (National Institute and Other Communication Disorders, 2004).
OI 3.04 Hydrocephalus ex-vacuo
Disability Category: Orthopedic Impairment
Definition
Hydrocephalus ex-vacuo occurs when there is damage to the brain due to the effects of stroke or traumatic Institute for Neurological Disorders and Stroke, 2005c).
Explanation
What is termed “hydrocephalus ex-vacuo” occurs when there is damage to the brain caused by stroke or injury, and there may be an actual shrinkage of brain substance. “Hydrocephalus ex-vacuo” is essentially only hydrocephalus by default; the CSF pressure itself is normal (Medicine.net, 2004)
OI 3.05 Non-communicating hydrocephalus
Disability Category: Orthopedic Impairment
Definition
Non-communicating hydrocephalus—also called “obstructive” hydrocephalus—occurs when the flow of CSF is blocked along one or more of the narrow pathways connecting the ventricles (National Institute for Neurological Disorders and Stroke, 2005c).
Explanation
In most cases it refers to a blockage between the third and fourth ventricles at the level of the Aqueduct of Sylvius, so called aqueductal obstruction. This can be due to scarring of this passage (aqueductal stenosis), or a tumor (in most cases a tectal glioma). When the obstruction is due to a tectal glioma it is important to realize that the tumor has only a 10% chance for growth and the only treatment required is for the hydrocephalus. Additional treatments for the tumor are only delivered if growth is documented(Hyman-Newman Institute for Neurology and Neurosurgery, 2005).
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