GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 405 Headache Key Terms Analgesic A medication that relieves pain without causing loss of consciousness; over-the-counter analgesics include aspirin and NSAIDs. Aura A group of visual or other sensations that pre- cedes the onset of a migraine attack. Cephalalgia The medical term for headache. Dura mater The outermost and toughest of the three membranes or meninges that cover the brain and spinal cord. The arteries that supply the dura mater and the portion of the dura mater at the base of the skull are sensitive to pain. Endodontist A dentist who specializes in the treat- ment of diseases and injuries that affect the tooth root, dental pulp, and the tissues surrounding the tooth root. Idiopathic Of unknown cause or spontaneous ori- gin. Some headaches are considered idiopathic. Neurotransmitter Any of a group of chemicals that transmit nerve impulses across the gap (synapse) be- tween two nerve cells. Nociceptor A specialized type of nerve cell that senses pain. Open-label study A type of study in which both the researchers and the subjects are aware of the drug or therapy that is being tested. Pathophysiology The changes in body functions as- sociated with a disorder or disease. Primary headache A headache that is not caused by another disease or medical condition. Prodrome A symptom or group of symptoms that appears shortly before an acute attack of illness. The term comes from a Greek word that means “running ahead of.” Projectile vomiting Forceful vomiting that is not preceded by nausea. It is usually associated with in- creased pressure inside the head. Prophylaxis A measure taken to prevent disease or an acute attack of a chronic disorder. Migraine pro- phylaxis refers to medications taken to reduce the frequency of migraine attacks. Rebound headache A type of primary headache caused by overuse of migraine medications or pain relievers. It is also known as analgesic abuse headache. Secondary headache A headache that is caused by another disease or disorder. Somatoform disorders A group of psychiatric dis- orders in the DSM-IV classification that are charac- terized by external physical symptoms or complaints related to psychological problems rather than or- ganic illness. Spondylosis A general medical term for degenera- tive changes in the spinal vertebrae caused by os- teoarthritis. Status migrainosus The medical term for an acute migraine headache that lasts 72 hours or longer. Temporomandibular joint (TMJ) The small joint in front of the ear in humans where the mandible (lower jaw) is attached to the skull. Causes and symptoms Causes PHYSICAL A person feels headache pain when spe- cialized nerve endings known as nociceptors are stimu- lated by pressure on or injury to any of the pain-sensitive structures of the head. Most nociceptors in humans are lo- cated in the skin or in the walls of blood vessels and in- ternal organs; the bones of the skull and the brain itself do not contain nociceptors. The specific parts of the head that are sensitive to pain include: • the skin that covers the skull and cervical spine • the 5th, 9th, and 10th cranial nerves and the nerves that supply the upper part of the neck • the venous sinuses inside the head • the large arteries at the base of the brain • the large arteries that supply the dura mater, which is the outermost of the three meninges (membranes) that cover the brain and spinal cord • the portion of the dura mater at the base of the skull Tension headaches typically result from tightening of the muscles of the face, neck, and scalp as a result of emo- tional stress; physical postures that cause the head and neck muscles to tense (e.g., holding a phone against the ear with one’s shoulder); depression or anxiety; tem- poromandibular joint dysfunction (TMJ); or degenerative arthritis of the neck. The tense muscles put pressure on the walls of the blood vessels that supply the neck and head, LetterH.qxd 10/1/04 11:05 AM Page 405 406 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Headache which stimulates the nociceptors in the tissues that line the blood vessels. In addition, the nociceptors in patients with chronic tension headaches appear to be abnormally sensi- tive to stimulation. The pathophysiology of migraine headaches has been debated among doctors since the 1940s. Some researchers think that migraines are the end result of a magnesium de- ficiency in the brain or of hypersensitivity to a neuro- transmitter known as dopamine. Another theory holds that certain nerve cells in the brain cortex become unusually excitable and depolarize (lose their electrical potential) spontaneously, releasing potassium and glutamate, an amino acid. These substances then depolarize nearby nerve cells, resulting in a chain reaction known as cortical- spreading depression (CSD). CSD then leads to changes in the amount of blood flowing through the blood vessels and stimulation of their nociceptors, resulting in severe headache. More recently, the discovery of specific genes associated with migraine indicates that genetic mutations are responsible for the abnormal excitability of the nerve cells in the brains of patients with migraine. Little is known about the causes of cluster headaches or changes in the central nervous system that produce them. PSYCHOLOGICAL Chronic headaches are often asso- ciated with anxiety, depression, or a specific group of mental disorders known as somatoform disorders. These disorders include hypochondriasis and pain disorder; they are characterized by physical symptoms (frequently headache) that suggest that the patient has a general med- ical condition, but there is no diagnosable disease or dis- order that fully accounts for the patient’s symptoms. The relationship between psychological and physical factors in headaches is complex in that headaches may be either the cause or result of emotional disturbances, or both. Some patients find that chronic headaches disappear completely after a stressful family- or job-related situation has been resolved. Warning symptoms Most headaches are not associated with serious or life-threatening illnesses. Patients should, however, im- mediately call their primary physician if they have any of the following symptoms: • three or more headaches per week • need for a pain reliever every day or almost every day • need for greater than recommended doses of over-the- counter medications (OTCs) • stiff neck or fever accompanying the headache • shortness of breath, hearing problems, blurry vision, or severe sore throat • dizziness, weakness, slurred speech, mental confusion, or drowsiness • headache following a head injury that is not relieved by OTCs • headache triggered by exercise, coughing, sexual activ- ity, or bending over • persistent or violent vomiting • change in the character of the headaches—for example, persistent severe headaches in a person who has previ- ously had only mild headaches of brief duration • recurrent headaches in a child • recurrent severe headaches, beginning after age 50 Diagnosis Patient history The differential diagnosis of headaches begins with a complete patient history, including a family history. In many cases, a primary care physician can make the diag- nosis on the basis of the history. The doctor will ask the patient about head injuries or surgery on the head; eye problems or disorders; sinus infections; dental problems or extensive oral surgery; and medications that the patient is taking regularly. After taking the history, the doctor will ask the patient to describe the location and type of pain that he or she ex- periences during the headache. People who have tension headaches will typically describe the pain as “viselike,” “tightening,” “pressing,” or as a steady or constant ache. Patients with migraine headaches, on the other hand, will usually say that the pain has a “throbbing” or “pulsating” character, while patients with cluster headaches describe the pain as “penetrating” or “piercing.” About 85% of pa- tients with tension headaches experience pain on both sides of the head, most commonly in the area around the forehead and temples. Patients with migraine or cluster headaches, however, are more likely to feel pain on only one side of the head. Some primary care physicians give the patient a printed questionnaire that consists of 50–55 brief yes/no questions that cover such matters as the timing and fre- quency of the headaches; whether other family members have the same type of headache; whether the patient feels depressed; whether the headaches are related to changes in the weather; and so on. The answers to the questions will usually fall into a pattern that tells the doctor whether the patient has migraines, tension headaches, cluster headaches, or headaches with other causes. The doctor may also ask the patient to keep a headache diary to help identify foods, stress, lack of sleep, weather, and other fac- tors that may trigger headaches. It is possible for patients to have more than one type of headache. For example, patients with chronic tension headaches often have migraine headaches as well. LetterH.qxd 10/1/04 11:05 AM Page 406 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 407 Headache Physical examination The physical examination helps the doctor identify other symptoms and signs that may be relevant to the di- agnosis, such as fever; difficulty breathing; nausea or vom- iting; stiff neck; changes in vision or hearing; watering or inflammation of the nose and eyes; evidence of head trauma; skin rashes or other indications of an infectious disease; and abnormalities in the structure or alignment of the patient’s spinal column, teeth or jaw. In some cases, the doctor may refer the patient to a dentist, oral surgeon, or endodontist for a more detailed evaluation of the patient’s mouth and jaw. Special studies Some laboratory tests are useful in identifying headaches caused by infections or by such disorders as anemia or thyroid disease. These tests include a complete blood count (CBC); erythrocyte sedimentation rate (ESR); and blood serum chemistry profile. Patients who report visual disturbances and other neurologic symptoms may be given visual field tests and have the pressure of the fluid inside their eyes (intraocu- lar pressure) tested to check for glaucoma. A lumbar punc- ture (spinal tap) may be done to confirm a diagnosis of idiopathic intracranial hypertension. Imaging studies may include x rays of the sinuses to check for sinus infections; and CT or MRI scans, which are done to rule out brain tumors and cerebral aneurysms. Patients whose symptoms cannot be fully explained by the results of physical examinations and tests may be referred to a psychiatrist for evaluation of psychological factors related to their headaches. Treatment Medical TENSION HEADACHES Episodic tension headaches are usually relieved fairly rapidly by such over-the-counter analgesics as aspirin (300–600 mg every four hours), acetaminophen (650 mg every four hours), or another non- steroidal anti-inflammatory drug (NSAID), usually ibuprofen (Advil) or naproxen (Naprosyn, Aleve). The doctor may prescribe a tricyclic antidepressant or benzo- diazepine tranquilizer in addition to a pain reliever for pa- tients with chronic tension headaches. A newer treatment for chronic tension headaches is botulinum toxin (Botox type A), which appears to work very well for some pa- tients. As of 2003, however, Botox has not yet been eval- uated in controlled multicenter studies as a treatment for chronic headaches; the data obtained so far are derived from case reports and open-label studies. MIGRAINE HEADACHES Medications can be pre- scribed to prevent migraines as well as to treat the symp- toms of an acute attack. Drugs that are given for migraine prophylaxis (to prevent or lower the frequency of migraine attacks) include tricyclic antidepressants, beta-blockers, and anti-epileptic drugs, which are also known as anti- convulsants. As of 2003, sodium valproate (Epilim) is the only anticonvulsant approved by the Food and Drug Ad- ministration (FDA) for prevention of migraine. Such newer anticonvulsants as gabapentin (Neurontin) and topira- mate (Topamax) are presently being evaluated as migraine preventives. Moreover, a new study reported that three drugs currently used to treat disorders of muscle tone are being explored as possible preventives for migraine— Botox, baclofen (Lioresal), and tizanidine (Zanaflex). Early results of open trials of these medications are positive. Nonsteroidal anti-inflammatory drugs acetamino- phen (Tylenol), ibuprofen (Motrin), and naproxen (Aleve) are helpful for early or mild migraines. More severe or un- responsive attacks may be treated with dihydroergota- mine; a group of drugs known as triptans; beta-blockers and calcium channel-blockers; antiseizure drugs; antide- pressants (SSRIs); meperidine (Demerol); or metoclo- pramide (Reglan). Some of these are also available as nasal sprays, intramuscular injections, or rectal supposi- tories for patients with severe vomiting. Sumatriptan and the other triptan drugs (zolmitriptan, rizatriptan, naratrip- tan, almotriptan, and frovatriptan) should not be taken by patients with vascular disease, however, because they cause narrowing of the coronary arteries. About 40% of all migraine attacks do not respond to treatment with triptans or any other medication. If the headache lasts longer than 72 hours—a condition known as status migrainosus—the patient may be given narcotic medications to bring on sleep and stop the attack. Patients with status migrainosus are often hospitalized because they are likely to be dehydrated from severe nausea and vomiting. CLUSTER HEADACHES Medications that are given as prophylaxis for cluster headaches include verapamil (Calan, Isoptin, Verelan), which is a calcium channel blocker, and methysergide (Sansert), which is a derivative of ergot. A new study indicates that topiramate (Topamax), an anticonvulsant, is also effective in preventing cluster headaches. Sumatriptan (Imitrex) or indomethacin (In- dameth, Indocin) may be prescribed to suppress an attack. REBOUND HEADACHES Continued use of some pain relievers or antimigraine drugs can lead to rebound headaches, which may be frequent or chronic and often occur in the early morning hours. Rebound headache can be avoided by using antimigraine drugs or analgesics under a doctor’s supervision, using only the minimum dose necessary to treat symptoms. Tizanidine (Zanaflex) has been reported to be effective in treating rebound headaches when taken together with an NSAID; Botox has also been used successfully in some patients. LetterH.qxd 10/1/04 11:05 AM Page 407 408 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Headache Diet and lifestyle modifications One measure that people can take to lower the risk of episodic tension headaches is to get enough sleep and eat nutritious meals at regular times. Skipping meals, using unbalanced fad diets to lose weight, and having insuffi- cient or poor-quality sleep can bring on tension headaches. In fact, the common association of tension headaches with hunger, lack of sleep, heat, and sudden temperature ex- tremes has led some researchers to suggest that headaches developed over the course of human evolution as an inter- nal protective response to stress from the environment. Changes in diet may be helpful to some patients with migraine, although some experts think that the role of foods in triggering migraines has been exaggerated. Women with migraines, however, often benefit by switch- ing from oral contraceptives to another method of birth control or by discontinuing estrogen replacement therapy. Patients with cluster headaches are advised to quit smoking and minimize their use of alcohol, because nico- tine and alcohol appear to trigger cluster headaches. Cur- rently, the precise connection between these chemicals and cluster attacks, however, is not completely understood. Surgical Headaches that are caused by brain tumors, post-in- jury hematomas, dental problems, or disorders affecting the spinal disks usually require surgical treatment. Surgery may also be used to treat cases of idiopathic intracranial hypertension that do not respond to treatment with steroids, repeated lumbar punctures, or weight reduction. Some plastic surgeons have reported success in treat- ing patients with chronic migraines by removing some muscle tissue near the eyebrows, cutting a branch of the trigeminal nerve, and repositioning the soft tissue around the temples. Psychotherapy Psychotherapy may be helpful to patients with chronic headaches by interrupting the “feedback loop” be- tween emotional upset and the physical symptoms of headaches. One type of psychotherapy that has been shown to be effective is cognitive restructuring, an ap- proach that teaches people to reframe the problems in their lives—that is, to change their conscious attitudes and re- sponses to these stressors. Some psychotherapists teach re- laxation techniques, biofeedback, or other approaches to stress management as well as cognitive restructuring. Complementary and alternative (CAM) treatments There are a number of different CAM treatments for headache, but most fall into two major groups: those in- tended as prophylaxis or pain relief, and those that reduce the patient’s stress level. CAM therapies intended to prevent headaches or re- lieve discomfort include: • Feverfew (Tanacetum parthenium). Feverfew is an herb related to the daisy that is traditionally used in England to prevent migraines. Published studies indicate that feverfew can reduce the frequency and intensity of mi- graines. It does not, however, relieve pain once the headache has begun. • Butterbur root (Petasites hybridus). Petadolex is a natu- ral preparation made from butterbur root that has been sold in Germany since the 1970s as a migraine preven- tive. Petadolex has been available in the United States since December 1998. • Brahmi (Bacopa monnieri). Brahmi is a herb used in Ayurvedic medicine to treat headaches related to anxiety. • Acupuncture. Studies funded by the National Center for Complementary and Alternative Medicine (NCCAM) have found that acupuncture is an effective treatment for headache pain in many patients. • Naturopathy. Naturopaths include dietary advice and nu- tritional therapy in their approach to treatment, which is often effective for patients with episodic or chronic ten- sion headaches. • Chiropractic. Some patients with tension or migraine headaches find spinal manipulation effective in relieving their pain; however, no controlled studies of the long- term effectiveness of chiropractic in treating headaches have been done as of 2003. CAM therapies that are reported to be effective in re- ducing emotional stress related to headaches include: • yoga and t’ai chi • prayer and meditation • aromatherapy • hydrotherapy, particularly whirlpool baths • Swedish massage and shiatsu • pet therapy • humor therapy • music therapy Clinical trials As of late 2003, there were three National Institutes of Health (NIH) trials recruiting patients with headaches: a study evaluating a new intranasal drug (civamide) for clus- ter headaches; a study of the effectiveness of biofeedback and relaxation training in patients with chronic migraine or tension headaches; and a study of migraine headaches in children. LetterH.qxd 10/1/04 11:05 AM Page 408 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 409 Headache Prognosis The prognosis of primary headaches varies. Episodic tension headaches usually resolve completely in less than a day without affecting the patient’s overall health. Ac- cording to NIH statistics, 90% of patients with chronic tension or cluster headaches can be helped. The prognosis for patients with migraines, however, depends on whether the patient has one or more of the other disorders that are associated with migraine. These disorders include Tourette’s syndrome, epilepsy, ischemic stroke, heredi- tary essential tremor, depression, anxiety, and others. For example, migraine with aura increases a person’s risk of ischemic stroke by a factor of six. The prognosis of secondary headaches depends on the seriousness and severity of their cause. Resources BOOKS American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision. Washington, DC: American Psychiatric Association, 2000. “Headache.” The Merck Manual of Diagnosis and Therapy. Edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2002. Pelletier, Kenneth R. The Best Alternative Medicine, Part II, “CAM Therapies for Specific Conditions: Headache.” New York: Simon & Schuster, 2002. “Psychogenic Pain Syndromes.” The Merck Manual of Diagnosis and Therapy. Edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2002. PERIODICALS Argoff, C. E. “The Use of Botulinum Toxins for Chronic Pain and Headaches.” Current Treatment Options in Neurology 5 (November 2003): 483–492. Astin, J. A., and E. Ernst. “The Effectiveness of Spinal Manipulation for the Treatment of Headache Disorders: A Systematic Review of Randomized Clinical Trials.” Cephalalgia 22 (October 2002): 617–623. Corbo, J. “The Role of Anticonvulsants in Preventive Migraine Therapy.” Current Pain and Headache Reports 7 (February 2003): 63–66. Freitag, F. G. “Preventative Treatment for Migraine and Tension-Type Headaches: Do Drugs Having Effects on Muscle Spasm and Tone Have a Role?” CNS Drugs 17 (2003): 373–381. Guyuron, B., T. Tucker, and J. Davis. “Surgical Treatment of Migraine Headaches.” Plastic and Reconstructive Surgery 109 (June 2002): 2183–2189. Headache Classification Subcommittee of the International Headache Society. “The International Classification of Headache Disorders,” 2nd ed. Cephalalgia 24 (2004) (Supplement 1): 1–150. Lainez, M. J., J. Pascual, A. M. Pascual, et al. “Topiramate in the Prophylactic Treatment of Cluster Headache.” Headache 43 (July-August 2003): 784–789. Lenaerts, M. E. “Cluster Headaches and Cluster Variants.” Current Treatment Options in Neurology 5 (November 2003): 455–466. Lipton, R. B., A. I. Scher, T. J. Steiner, et al. “Patterns of Health Care Utilization for Migraine in England and in the United States.” Neurology 60 (February 11, 2003): 441–448. Marconi, R., M. De Fusco, P. Aridon, et al. “Familial Hemiplegic Migraine Type 2 is Linked to 0.9Mb Region on Chromosome 1q23.” Annals of Neurology 53 (March 2003): 376–381. Mendizabai, Jorge, MD. “Cluster Headache.” eMedicine,26 September 2003. <http://www.emedicine.com/neuro/ topic70.htm>. Sahai, Soma, MD, Robert Cowan, MD, and David Y. Ko, MD. “Pathophysiology and Treatment of Migraine and Related Headache.” eMedicine, April 30, 2002 (February 16, 2004). <http://www.emedicine.com/neuro/topic517.htm>. Singh, Manish K., MD. “Muscle Contraction Tension Headache.” eMedicine, October 5, 2001 (February 16, 2004). <http://www.emedicine.com/neuro/topic231.htm>. Soragna, D., A. Vettori, G. Carraro, et al. “A Locus for Migraine Without Aura Maps on Chromosome 14q21.2–q22.3.” American Journal of Human Genetics 72 (January 2003): 161–167. Tepper, S. J., and D. Millson. “Safety Profile of the Triptans.” Expert Opinion on Drug Safety 2 (March 2003): 123–132. OTHER Migraine Information Page. NINDS. 2003 (February 16, 2004). <http://www.ninds.nih.gov/health_and_medical/ pubs/migraineupdate.htm>. National Institute of Neurological Disorders and Stroke (NINDS). “Headache—Hope Through Research.” Bethesda, MD: NINDS, 2001. (February 16, 2004.) <http://www.ninds.nih.gov/health_and_medical/pubs/ headache_htr>. ORGANIZATIONS American Academy of Neurology (AAN). 1080 Montreal Avenue, Saint Paul, MN 55116. (651) 695-2717 or (800) 879-1960; Fax: (651) 695-2791. memberservices@ aan.com. <http://www.aan.com>. American Council for Headache Education (ACHE). 19 Mantua Road, Mt. Royal, NJ 08061. (856) 423-0258; Fax: (856) 423-0082. achehq@talley.com. <http://www.achenet.org>. International Headache Society (IHS). Oakwood, 9 Willowmead Drive, Prestbury, Cheshire SK10 4BU, United Kingdom. +44 (0) 1625 828663; Fax: +44 (0) 1625 828494. rosemary@ihs.u-net.com. <http://216.25.100.131>. National Headache Foundation. 820 North Orleans, Suite 217, Chicago, IL 60610. (773) 525-7357 or (888) NHF-5552. <http://www.headaches.org>. NIH Neurological Institute. P. O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. <http://www.ninds.nih.gov>. Rebecca J. Frey, PhD LetterH.qxd 10/1/04 11:05 AM Page 409 410 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Hearing disorders ❙ Hearing disorders Definition Hearing disorders range from a temporary, partial loss of hearing to the permanent loss of hearing known as deafness. Description The variety of hearing disorders includes a loss or de- crease in the ability to discern certain frequencies of sound, a ringing or other noise that is unrelated to any actual ex- ternal sound, damage due to physical trauma or infection, and genetically determined structural malformation. Demographics Hearing disorders occur worldwide in all races. The hearing loss that occurs with age is very common, affect- ing an estimated 30% of Americans over 60 years of age and 50% of those older than 75. Tinnitus, a ringing or noisy sensation in the ears, is quite common with an estimated 20% of people affected worldwide. In the United States alone, some 36 million people experience tinnitus. For hearing loss caused by otosclerosis, middle-aged Caucasian women are more prone than others, perhaps as a consequence of hormonal changes. In otosclerosis, ab- normal bone development occurs in the middle ear, re- sulting in progressive hearing loss. Sudden hearing loss happens more often to people ages 30–60 for unknown reasons. Causes and symptoms Presbycusis Presbycusis (or sensorineural hearing loss) is the loss of hearing that occurs with age. The condition results from the long-term assault on the ear structures, particularly on the inner ear, from a lifetime of noise, ear infections, or growths on bones of the outer or middle ear. The inner ear is where the vibrational sound waves are converted to elec- trical signals, courtesy of thousands of tiny hairs that are in a fluid-enclosed space called the cochlea. The hairs are connected to nerve cells, which send the electrical signals to the brain. Most age-related hearing loss is due to damage to the cochlea. The tiny hairs can bend or even break, and the at- tached nerve cells can degenerate. The resulting less-effi- cient transmission of the electrical signal, particularly of higher-pitched tones, causes hearing loss. Symptoms of presbycusis typically include increased difficulty in making out sounds of a certain volume or tone, especially when background sounds are present. Conductive hearing loss In conductive hearing loss, sound is not transmitted efficiently through the outer and middle ears. These re- gions house the eardrum, ear canal, and the trio of tiny bones (ossicles) in the middle ear that transmits sound en- ergy to the inner ear. The hearing loss can be due to mal- formation of structures like the canal or the ossicles, dense buildup of ear wax, or fluid in the ear due to colds, aller- gies, or infections like otitis media. Symptoms include a decreased ability to detect fainter sounds and a general lowering of the sound level that can be detected. Otitis media Otitis media is an inflammation in the middle ear that is usually accompanied by fluid buildup. The condition may be transient in some children, but persistent in others to the point of requiring surgical correction. In developed countries, otitis media is second to the common cold as the most common health problem in preschool-aged children. Hearing loss occurs because of the fluid accumulation and the resulting suppression of sound waves moving to the inner ear. Central auditory processing disorders Central auditory processing disorders result in hear- ing loss when the areas of the brain involved in hearing are damaged. Sources of damage include disease, injury, and tumor growth. Consistent with the variety of causes, the symptoms of the disorders include the inability to hear cer- tain sounds, inability to tell one sound from another, and the inability to recognize a pattern such as speech in sounds. Congenital hearing loss Congenital hearing loss is present from birth and is caused by a genetic defect or disturbance during fetal de- velopment. Genetic factors cause more than half of all such disorders. Depending on the nature of the genetic de- fect, the occurrence of the hearing loss may be common or rare. For example, if both parents have a genetically de- termined hearing deficiency, the chance of passing the trait to their children is high. In other cases, people who have normal hearing carry a second, defective copy of a crucial gene. The chance of passing on the hearing loss is 25%. Hearing loss at birth can also be caused by pre-birth infections such as measles, cytomegalovirus, or herpes simplex virus. Otosclerosis The abnormal growth of the bone of the middle ear prevents the ossicles, particularly the last of the trio of bones (the stapes), from properly transmitting sound LetterH.qxd 10/1/04 11:05 AM Page 410 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 411 Hearing disorders Key Terms Cochlear implant A device used for treating deaf- ness that consists of one or more electrodes surgi- cally implanted inside or outside the cochlea, an organ in the inner ear that transforms sound vibra- tions in the inner ear into nerve impulses for trans- mission to the brain. Ossicles Tiny bones in the middle ear, the incus, malleus, and stapes, that convey sound impulses from the eardrum to the inner ear. Otitis media Inflammation, usually with infection, of the middle ear. Otosclerosis Abnormal bone development in the middle ear, resulting in progressive hearing loss. Presbycusis Loss of hearing that gradually occurs because of age-related changes in the inner or mid- dle ear. Tinnitus Ringing or noisy sensations in the ears when no external sound is present, often associated with hearing impairment and excess noise exposure. waves to the inner ear in otosclerosis. The cause(s) of oto- sclerosis are not clear, although observations that the dis- order spans family generations make a genetic source likely. The diminished hearing that occurs is not sudden. Rather, the change is gradual and is usually recognized when the person becomes aware that she or he can no longer hear a low-pitched sound such as a whisper. Other genetically based hearing losses Usher syndrome affects both the ears and eyes. The defective genes that are at the heart of the malady are passed from parents to children. Depending on the nature of the syndrome, children can be born with moderate to se- vere hearing loss, or can be totally deaf. Others begin life essentially normal, with hearing loss progressively wors- ening to deafness by the teenage years. Waardenburg syndrome affects both the ears and the color of the skin, eyes, or hair. Eyes can be different col- ors and hair can have a patch of white or become prema- turely gray. Hearing can range from normal to severely impaired. At least four genes can produce the syndrome when they undergo mutation. Ménière’s disease Ménière’s disease is a change in the volume of the inner ear that produces swelling, pressure, pain, intermit- tent hearing loss, dizziness, and tinnitus. Swelling may be so pronounced that membranes like the eardrum can rup- ture. As well, some people report that their voice sounds louder than normal. The disease may be caused by a viral or bacterial infection. Tinnitus Tinnitus is a ringing noise or other sound that occurs in the absence of an external source of sound. For some, tinnitus is an infrequent occurrence. Others are very in- convenienced by near-constant tinnitus. The noises experi- enced in tinnitus range in description and include electronic noise, hissing steam, chirping crickets, bells, breaking glass, buzzing, and even the noise of a chainsaw. The noises can be constant or may rise and fall in volume with head motion or with the planting of feet during running. Tinnitus has various known triggers. Foods such as red wine, cheese, and chocolate have been implicated. Over-the-counter drugs such as ibuprofen and extra- strength aspirin, and prescribed drugs, including oral con- traceptives and aminoglycoside antibiotics, can cause tinnitus. Drug-related tinnitus disappears when the dosage is reduced or the drug stopped. The growth of certain tu- mors can cause tinnitus. The aging of the inner ear is also a factor in tinnitus. As nerve cells deteriorate and the many hairs in the cochlea that transmit sound waves to the nerves become damaged and broken with time, the signaling of sound im- pulses to the brain becomes faulty. Nerves may fire when there has been no stimulus. The brain interprets the signal as actual noise. Sudden deafness or sudden sensorineural hearing loss This rapid decrease or complete loss of hearing can occur within minutes or over the course of several days. The hearing loss typically affects one ear and often re- solves with time. Sudden deafness is much more serious and should be treated as a medical emergency requiring immediate medical attention. Causes are unclear and may involve an infection, head injury, reaction to a drug, prob- lems with circulation, and other disorders such as multi- ple sclerosis. Deafness The complete loss of hearing can be due to geneti- cally determined developmental difficulties, a trauma such as a loud noise, physical damage to structures in the ear, nerves, or relevant areas of the brain, and infection during pregnancy (such as rubella). In a great many cases, deaf- ness is permanent. Childhood deafness typically becomes apparent when a child appears inattentive and fails to meet language milestones. LetterH.qxd 10/1/04 11:05 AM Page 411 412 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Hearing disorders A mother and young daughter communicate with sign language. (© Custom Medical Stock Photo. Reproduced by permission.) Diagnosis Presbycusis is usually first detected by a family physi- cian. Diagnosis is subsequently made by a hearing spe- cialist or an audiologist, and involves a hearing test in which sounds of differing frequencies and gradually de- creasing volume are sent to one ear at a time. Tinnitus is self-evident, as the ringing or other sensa- tion is impossible to ignore. In contrast, otitis media can be difficult to diagnose, as it is often not accompanied by pain or a fever. Fluid in the ear can be a sign of otitis media. Also, changes in children’s behavior such as play- ing the television louder, misunderstanding directions, and pulling at the ears can all be indicators of otitis media. Imaging of the inside of the ear using the technique of magnetic resonance imaging (MRI) can be useful in di- agnosing Ménière’s disease. Usher syndrome is diagnosed by the simultaneous appearance of ear and eye problems. Treatment team The varied treatment can involve the family physician and more specialized doctors, including audiologists and otolaryngologists (specialists in ear, nose, and throat dis- orders). As well, speech-language pathologists can be in- volved in the treatment of hearing loss-related speech disorders in children. Treatment Treatment for presbycusis can be as simple as keep- ing the ear canals free from sound-muffling wax buildup. Another fairly common treatment for older people is the use of a hearing aid, which amplifies sound and directs the sound into the ear canal. About 20% of those with age-re- lated hearing loss can benefit from an aid. More severe presbycusis can be treated using a cochlear implant. The device actually compensates for the nonworking parts of the inner ear. Conductive hearing loss can usually be fully corrected by medication or surgery. Similarly, when tin- nitus is caused by overmedication, the condition is allevi- ated by modifying or eliminating the dosage of the drug. Ménière’s disease and Usher syndrome cannot be cured, however, the symptoms can be greatly relieved by release of the buildup of pressure in the inner ear and the use of hearing aids or implants, respectively. Coping strategies and increased knowledge of the conditions can then help a person lead an essentially normal life. Otosclerosis that is more pronounced can be treated by a surgical procedure called a stapedectomy, in which the damaged portion of the middle ear, the stapes, one of the three bones of the middle ear, is bypassed by an im- planted device that routes sound to the inner ear. Milder otosclerosis may be lessened by the use of a hearing aid. LetterH.qxd 10/1/04 11:05 AM Page 412 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 413 Hemianopsia Recovery and rehabilitation Some conditions that can be addressed by surgery or the use of a hearing aid or an implant have varying levels of recovery. Other conditions involving permanent deaf- ness cannot be cured. Clinical trials As of April 2004, at least eight clinical trials were active in the United States. Most focus on deafness, in par- ticular the determination of the genetic factors that con- tribute to or cause deafness. Updated information on these studies can be found at the National Institutes of Health Web site for clinical trials at <http://www. clinicaltrials.gov>. Prognosis Age-related hearing loss can be partially or almost completely compensated for by a change in lifestyle and the development of coping skills (listening to the radio at higher volume, different conversational behavior in crowds, use of hearing aids or implants). Otitis media can cause delayed speech development, if undiagnosed, be- cause of the child’s impaired ability to hear. Sudden hear- ing loss usually resolves on its own within a few days to several weeks. However, in about 15% of cases, the con- dition worsens with time. Special concerns The various surgeries that can be performed all carry some risk, and the quality of sound that is provided by cochlear implants varies greatly among recipients. Additionally, tinnitus can be caused by the buildup of cholesterol in arteries around the ear, high blood pressure, and by malformed arteries or veins. Tinnitus, therefore, may be an indication of a more serious health problem. Resources BOOKS Dugan, Marcia B. Living with Hearing Loss. Baltimore: Gallaudet Press, 2003. Schwartz, Sue. Choices in Deafness: A Parents’ Guide to Communication Options. Bethesda, MD: Woodbine House, 2003. PERIODICALS DeJonckere, P. H., and G. G. de Surgeres. “Acute Tinnitus and Permanent Audiovestibular Damage after Hepatitis B Vaccination.” International Tinnitus Journal (July 2001): 59–61. Waddell, A., and R. Canter. “Tinnitus.” American Family Physician (February 2004): 591–592. OTHER “Hearing Loss.” MayoClinic.com. April 8, 2004 (May 30, 2004). <http://www.mayoclinic.com/invoke.cfm? id=DS00172>. “Tinnitus.” MayoClinic.com. April 8, 2004 (May 30, 2004). <http://www.mayoclinic.com/invoke.cfm?id=DS00365>. ORGANIZATIONS American Academy of Audiology. 8300 Greensboro Drive, Suite 750, McLean, VA 22102. (703) 790-8466 or (800) 222-2336; Fax: (703) 790-8631. info@audiology.org. <http://www.audiology.org>. American Speech-Language-Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (301) 638-8255 or (800) 638-8255; Fax: (301) 571-0457. actioncenter@ asha.org. <http://www.asha.org>. American Tinnitus Association. PO Box 5, Portland, OR 97207-0005. (503) 248-9985 or (800) 634-8978; Fax: (503) 248-0024. tinnitus@ata.org. <http://www.ata.org>. Deafness Research Foundation. 1050 17th Street NW, Suite 701, Washington, DC 20036. (202) 289-5850. <http://www.drf.org>. National Center on Deafness. 18111 Nordhoff Street, Northridge, CA 91330-8267. (818) 677-2145; Fax: (818) 677-7693. ncod@csun.edu. <http://ncod.csun.edu>. National Institute on Deafness and Other Communication Disorders, National Institutes of Health. 31 Center Drive, MSC 2320, Bethesda, MD 20892-2320. (301) 496-7243 or (800) 241-1044; Fax: (301) 402-0018. nidcdinfo@nidcd.nih.gov. <http://www.nidcd.nih.gov>. Brian Douglas Hoyle, PhD ❙ Hemianopsia Definition Hemianopsia is a term that describes a loss of vision that affects half of the visual field of one eye or both eyes. Description Hemianopsia prevents an individual from seeing ob- jects in half of the visual field of a particular eye. As a re- sult, an individual suffering from hemianopsia will not see objects that are in the affected visual field. Causes and symptoms Conditions or injuries that affect the optic nerve can cause hemianopsia. The sequelae (aftereffects) of stroke, brain aneurysm, occlusion of the optic artery, brain tu- mors, or traumatic head injuries can all result in hemi- anopsia. Occasionally, individuals who suffer from LetterH.qxd 10/1/04 11:05 AM Page 413 414 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Hemifacial spasm migraine headaches may experience hemianopsia during a migrainous episode or as part of the prodromal aura that precedes the actual headache; this type of hemianopsia resolves completely upon resolution of the headache. Transient hemianopsia can result from bouts of extremely high blood pressure (as occurs in eclampsia) or during or after a seizure. Other rare causes of hemianopsia include infections, such as encephalitis, brain abscess, progres- sive multifocal leukoencephalopathy, and Creutzfeldt- Jakob disease. Symptoms of hemianopsia involve the inability to see objects in half of the visual field of one or both eyes, which may be manifested by reading difficulties, problems walking through crowded areas, frequent accidents (bumping into objects that are located in the lost visual field), or being startled at what seems to be the sudden emergence of people or objects in the visual field. Diagnosis Diagnosis is usually evident when basic testing re- veals a blind area in half of the visual field of one or both eyes. Further testing will be necessary to uncover the un- derlying causative condition: CT or MRI scanning may re- veal the presence of a stroke, aneurysm, or brain tumor. Treatment team Neurologists, ophthalmologists, and neuroophthal- mologists all work with patients with hemianopsia. Occu- pational therapists and vision rehabilitation specialists can be integral in teaching the individual how to compensate for their vision loss. Treatment Treatment includes therapy to practice techniques that may help an individual overcome the obstacles of hemi- anopsia. For example, changing reading techniques (look- ing at the last part of the word, rather than the first) may improve an individual’s ability to read and enjoy reading. Special scanning techniques may be taught, using a ma- chine called a Dynavision, which will help an individual learn how to turn the head in certain ways to scan the en- vironment and compensate for the lost visual field. Special glasses lenses, some with mirrors or prisms incorporated, may allow an individual with hemianopsia to view a greater visual field. Prognosis Recovery of vision after stroke or head injury is usu- ally maximal within the first three to six months; hemi- anopsia persisting after that point is usually permanent. Special concerns Driving can be a particular concern for people with hemianopsia. By learning new techniques for scanning the environment, some individuals can safely return to driv- ing; others will not be able to drive safely, and will no longer be able to obtain a driver’s license. This can result in significant changes in an individual’s lifestyle, inde- pendence, and employability. Resources BOOKS Liu, Grant T., and Nancy J. Newman. “Cranial Nerve II and Afferent Visual Pathways.” In Textbook of Clinical Neurology, edited by Christopher G. Goetz. Philadelphia: W. B. Saunders Company, 2003. Pulsinelli, William A. “Ischemic Cerebrovascular Disease.” In Cecil Textbook of Internal Medicine, edited by Lee Goldman, et al. Philadelphia: W. B. Saunders Company, 2000. ORGANIZATIONS Lighthouse International. 111 East 59th Street, New York, NY 10022. 212-821-9200 or 800-829-0500. info@ lighthouse.org. <http://www.lighthouse.org/Default.htm>. Rosalyn Carson-DeWitt, MD ❙ Hemifacial spasm Definition A hemifacial spasm is an involuntary contraction of the muscles of facial expression, resulting in eyelid closure and upturning of the corner of the mouth and accompanied by facial weakness. Description Hemifacial spasm results in involuntary contraction of the facial muscles limited to one side of the face. The eyelids are involved, and upturning of the corner of the mouth is observed. The patient may have facial twitching during periods of sleep. If left untreated, the twitching may worsen and extend to other facial muscles. Demographics Females are affected more than males, regardless of race. Typically, patients afflicted with hemifacial spasm are in their 40s or 50s. Causes and symptoms The cause of hemifacial spasm has been linked to overactivity of the seventh cranial nerve nucleus that sig- nals facial muscle movement. In other instances, hemifa- cial spasm may be caused by compression by a mass or LetterH.qxd 10/1/04 11:05 AM Page 414 [...]... NY 10 0 0 1- 5300 ( 212 ) 24 2 19 68 or (800) 345-HDSA (4372); Fax: ( 212 ) 23 9- 3 430 hdsainfo@hdsa.org Huntington Society of Canada 15 1 Frederick Street, Suite 400, Kitchener, Ontario N2H 2M2, Canada ( 5 19 ) 7 497 063 or (800) 99 8-7 398 ; Fax: ( 5 19 ) 74 9- 8 96 5 info@ hsc-ca.org International Huntington Association Callunahof 8, 7 217 St Harfsen, The Netherlands + 3 1- 57 3-4 315 95 ... Hypersomnia American Chronic Pain Association (ACPA) P.O Box 850, Rocklin, CA 95 67 7-0 850 ( 91 6 ) 63 2-0 92 2 or (800) 53332 31; Fax: ( 91 6 ) 63 2-3 208 ACPA@pacbell.net National Spinal Cord Injury Association 67 01 Democracy Blvd #30 0 -9 , Bethesda, MD 20 817 (3 01) 214 -4 006 or (800) 96 2 -9 6 29; Fax: (3 01) 8 8 1- 9 817 info@spinalcord.org Dawn J Cardeiro, MS, CGC Hypercortisolism... intoxication.” Journal of the American Academy of Child and Adolescent Psychiatry 35, no 8 (August 19 96 ): 10 50 -1 0 55 National Center on Sleep Disorders Research Working Group, Bethesda, Maryland “Recognizing Problem Sleepiness in Your People.” American Family Physician (February 15 , 19 99 ): 93 7-3 8 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS American Academy of Sleep Medicine 63 01 Bandel Road NW, Suite 10 1, Rochester,... Executive Boulevard, Bethesda, MD 20 892 (3 01) 49 6-5 7 51 or (800) 35 2 -9 424 430 National Organization for Rare Disorders 55 Kenosia Avenue, Danbury, CT 06 813 -1 9 68 (203) 74 4- 010 0 or (800) 99 96673; Fax: (203) 79 8-2 2 91 orphan@rarediseases.org Brian Douglas Hoyle, PhD S Hydrocephalus Definition The word hydrocephalus derives from the Greek words hydro,... withdrawn, antibodies removed, and the antibody-free liquid put back into the person, has not shown promise for HTLV -1 myelopathy Interestingly, this technique is useful in treating myelin damage caused in other disorders such as Guillain-Barré syndrome National Organization for Rare Disorders P.O Box 19 68, Danbury, CT 06 813 -1 9 68 (203) 74 4- 010 0 or (800) 99 96673; Fax: (203) 79 8-2 2 91 orphan@rarediseases.org ... symptoms HTLV -1 associated myelopathy is the result of infection with the HTLV -1 virus The common routes of transmission are through breast milk, transfused blood (especially prior to 19 89 when donated blood was not tested for HTLV -1 ) , sexual intercourse, and drug injection Until the viral link was established in the mid -1 9 80s, HTLV -1 associated myelopathy was thought to result in the inflammation of the central... Plains, NY 10 605 ( 91 4 ) 42 8- 710 0 or (888) 66 3-4 637; Fax: ( 91 4 ) 42 8-8 203 askus@ marchofdimes.com National Information Center for Children and Youth with Disabilities P.O Box 14 92 , Washington, DC 20 013 -1 4 92 (202) 88 4-8 200 or (800) 69 5-0 285; Fax: (202) 88 4-8 4 41 nichcy@ead.org National Institute for Neurological Diseases and Stroke (NINDS) 60 01 Executive Boulevard,... the symptoms depend on the location and extent of the cavitation (hollowing out) of the cord Over time, the expansion and elongation of the fluid-filled cavity (or cyst) can destroy the center of the spinal cord This damage to the 434 • loss of bowel and bladder control • spasticity and paralysis of the legs • visual disturbances • ataxia GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS Key Terms Dandy-Walker... Institute of Neurological Disorders and Stroke (March 6, 2004) ORGANIZATIONS Carter Centers for Research in Holoprosencephaly c/o Texas Scottish Rite Hospital, P.O Box 19 0567, 2222 Welborn Street, Dallas, TX 75 2 19 -9 98 2 ( 214 ) 55 9- 8 411 ; Fax: ( 214 ) 55 9- 7 835 hpe@tsrh.org Larry Gilman, Ph.D S HTLV -1 . .. children die in their first year of life, although survival past the age of 10 can rarely occur GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 4 29 Hydranencephaly American Epilepsy Society 342 North Main Street, West Hartford, CT 0 611 7-2 507 Hydrocephalus Key Terms Brainstem The stalk of the brain that connects the two cerebral hemispheres with the spinal cord It is involved in controlling . growth of the bone of the middle ear prevents the ossicles, particularly the last of the trio of bones (the stapes), from properly transmitting sound LetterH.qxd 10 /1/ 04 11 :05 AM Page 410 GALE ENCYCLOPEDIA. ex- tremely small head size (microcephaly) and on exami- nation of the face, which is often deformed by the LetterH.qxd 10 /1/ 04 11 :06 AM Page 418 GALE ENCYCLOPEDIA OF NEUROLOGICAL DISORDERS 4 19 HTLV -1 . P.O. Box 19 0567, 2222 Welborn Street, Dallas, TX 75 2 19 -9 982. ( 214 ) 55 9- 8 411 ; Fax: ( 214 ) 55 9- 7 835. hpe@tsrh.org. <http://www. stanford.edu/group/hpe>. Larry Gilman, Ph.D. ❙ HTLV -1 associated myelopathy Definition Damage