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Tinnitus
Cranial Nerves and Brain Stem CHAPTER 16
Tinnitus Ulrich Biittner and Alan H. Lockwood
Tinnitus is the false perception of tones and noises without an appropriate external stimulus. It is a common phenomenon. According to investigations in England, 17% of the population without noise-induced trauma had tinnitus that lasted more than 5min (Coles, 1987). The American Tinnitus Association estimates 50 million Americans have experienced the disorder. Tinnitus occurs largely in adults and becomes more frequent in old age. About 1 % of the population suffers from tinnitus with men more often affected than women. Acute tinnitus stops spontaneously in 60-80% of the cases. The chances of spontaneous recovery are small when the tinnitus lasts more than 3 months (chronic tinnitus). Most patients (85%) with continuous or intermittent tinnitus are relatively untroubled by the phenomenon (compensated tinnitus). For the remaining 1 5 % , the disorder may be a source of substantial disability (decompensated tinnitus). This is usually manifested by anxiety, inattentiveness, insomnia, depression, and/or other relatively nonspecific complaints. Some patients with depression have suicidal thoughts (2%). However, suicidal attempts without a history of depression are rare (Lewis et aL, 1994). Clinically, it is important to distinguish between subjective and objective tinnitus. In patients with objective tinnitus, the sounds are real, and may be heard with a stethoscope placed over the external auditory meatus or adjacent to the ear. Thus, objective tinnitus is not a phantom perception.
Souffle during Inspiration/Expiration Etiology This condition is due to an abnormally wide tuba auditiva eustachii, often caused by considerable weight loss. Treatment In individual cases a tube in the tuba Eustachii can lead to a narrowing (Robinson and Hazell, 1989).
Series of Sharp Clicks (Lasting Several Seconds to Minutes) Etiology This is called palatal myoclonus. It is a form of segmental myoclonus and is characterized by rhythmic contractions of the soft palate. There are often synchronous contractions of other voluntary muscles of the pharynx, larynx, face, neck, eyes, and occasionally the muscles of respiration. It is usually caused by a lesion in the pathways connecting the inferior olivary nucleus and the dentate nucleus. These lesions are usually seen on MRI scans where hypertrophy of the inferior olive may also be evident. Therapy
OBJECTIVE TINNITUS A distinction is made between the various noise types with etiological indications. Neurological Disorders: Course and Treatment, Second Edition Copyright 2003, Elsevier Science (USA). All rights reserved.
The disorder, once estabhshed, usually persists and is resistant to treatment. However, there are reports of responses to tetrabenazine, 5-HTP, trihexaphenadyl, and carbamazepine (Williams et al., 1998). Botulinum 165
166
CRANIAL NERVES AND BRAIN STEM
toxin injections may be tried in selected cases (Bryce and Morrison, 1998; Saeed and Brookes, 1993). The tensor veli palatini or the stapedius muscle can be transected surgically (Badia et al., 1994).
Vascular Bruit (Pulsatile Tinnitus) Etiology Vascular bruit is caused by (1) vascular stenoses or malformations of the head and neck, such as carotid stenosis and dural arteriovenous fistulas of the sigmoid or rarely other locations, or (2) vascular tumors of the petrous bone such as glomus tumor. Treatment
Spontaneous Otoacoustic Emissions (SOAE) Etiology Rarely, patients with SOAE will hear these sounds and complain of tinnitus (Penner, 1992). SOAEs are produced by movement of the cilia of the outer hair cells. While many normal people have SOAEs, most are unaware of their presence. These sounds are usually inaudible to others, but they are occasionally loud enough to be heard by an examiner. SOAEs can be detected by inserting very small microphones into the external auditory meatus and examining the spectra of recorded sounds.
SUBJECTIVE TINNITUS
Carotid stenoses are treated by endovascular dilatation or stenting or by open surgery. Dural arteriovenous fistulas are eliminted by transvenous or transarterial embolization or by surgical methods (Olteanu-Nerbe et aL, 1997). With dural fistulae more than 80% of the patients can achieve clinical resolution. The therapeutic outcome is better in less severe cases (Shah et aL^ 1999). Glomus tumors usually require surgical removal, possibly after transarterial embolization to reduce surgical blood loss.
Subjective Tinnitus with Rotational Vertigo
Continual Swishing Noise (Disappears when Pressure Is Applied to the Jugular Vein)
Sudden Hearing Loss
Etiology This has a venous origin, such as stenosis or external compression of the sigmoid sinus, high jugular bulb, aneurysm of the sigmoid sinus, or rarely intracranial hypertension. Treatment If compression by a tumor is identified as the cause, treatment depends on the nature of the neoplasm. The most common tumor, meningioma, requires surgery. Radiosurgery, an alternative method for small meningiomas using convergent X-ray beams does commonly not result in a dramatic shrinkage of the tumor volume and is therefore not a primary consideration in cases with a disturbing noise. High located jugular bulbs leading to Meniere's disease associated with a pulsatile component can be lowered surgically (Couloigner et aL, 1999). For other venous anomalies, venous obliteration by endovascular technique can be considered. The effect and tolerance of treatment can be tested by balloon test occlusion beforehand.
See information on Meniere's disease (Chapter 15).
Subjective Tinnitus with Hearing Defects Otosclerosis (Mostly Low-Frequency Tinnitus) Tinnitus subsides after surgery only in 30-50% of cases (House, 1989). It even might worsen.
ENT physicians use low-molecular-weight dextran, pentoxiphyllin, and nicotinic acid, although their success rate has not been established by controlled studies. Therapeutic effects have been reported with prednisolone (Lamm, 1995). Head Trauma (High Frequency, Ringing Tinnitus) Tinnitus after head trauma usually lasts only a couple of hours but can persist for years with inner ear lesions. There is no known treatment. Noise-Induced Trauma as a Result of Acute or Chronic Exposure After acute exposure therapeutic effects for cortisone in combination with hyperbaric oxygen have been reported (Lamm, 1995). Acoustic Neuroma Tinnitus is often continuous and high-frequency, on one side. It can precede the hearing defect. About 4 % of the neuromas present initially with tinnitus. Treat-
TINNITUS
merit options include surgery, after which tinnitus may persist (see below). Ototoxic
Medication
Certain aminoglycosides (especially canamycine, streptomycine, neomycine, bycomycine), heavy metals, and cisplatine can cause tinnitus. Treatment involves withdrawl from medication. Permanent deficits may persist.
Subjective Tinnitus without Hearing Defects Clinical Aspects Approximately only 10-20% of patients who complain of tinnitus do not suffer from concurrent hypacusis. Causing factors for tinnitus are often emotionally disturbing situations. About 10% of the patients complain about hyperacusis before the onset of tinnitus (Hazell and Sheldrake, 1992). Irrespective of its origin, tinnitus frequently causes major disturbance, particularly in quiet surroundings and at night (Fichter and Goebel, 1996). Patients react by becoming depressed and, in some cases, suicidal. Sleep is disturbed and patients complain about impaired memory and lack of concentration. Hearing loss, particularly in the high frequencies in the worse ear (often maximal at or about 4.0 kHz) is the most important risk factor or predictor for the development of sustained subjective tinnitus (Davis and Refaie, 2000). Some patients with tinnitus have hearing thesholds that are reportedly in the normal range. In these individuals, it is usually not possible to determine whether hearing thresholds have shifted toward the impaired range. Since thresholds are measured in dB, a logarithmic scale, substantial differences in sound energy may translate into a relatively small shift in thresholds. The exact location (central or peripheral) of the lesion is not known. An altered relation between the activity of outer and inner hair cells in the cochlea has been discussed (Jastreboff, 1990). Since tinnitus still persists after severance of the acoustic nerve, a central accentuation after primary peripheral lesion is likely (House and Brackmann, 1981). In the rat, abnormal activity has been recorded in the inferior colliculus with salicylate levels causing tinnitus (Jastreboff and Sasaki, 1994). This abnormal activity can be influenced by lidocaine. Lidocaine also affected the abnormally increased perfusion in the auditory cortex of a patient with chronic tinnitus using the SPECT method (Staffen et aL, 1999). In patients who could affect their tinnitus loudness by oral facial movements, PET studies suggest that the tinnitus
167
experience arises in the central auditory system and not the cochlea (Lockwood et aL, 1998). In these patients, who all had unilateral tinnitus, changes in neural activity that paralleled changes in the loudness of tinnitus were found unilaterally in auditory cortical sites. This unilaterality contrasted with bilateral activation of auditory cortex that was associated with tonal stimuli delivered to the ear that the patients said their tinnitus was heard. Since cochlear activation was associated with bilateral activation whereas tinnitus was associated with unilateral activity, the investigators deduced that tinnitus was not of cochlear origin. In this same group of patients, who all had sensorineural hearing loss, tonal stimuli activated a more extensive portion of auditory cortex than was activated by identical stimuli delivered to control subjects with normal hearing. This expansion of cortical sites responsive to the stimuli demonstrated plastic changes in the central auditory system. This led to the hypothesis that tinnitus is due to plastic transformations of the central auditory system due to deafferentation, a condition that may be analogous to phantom pain sensations that may follow somatosensory deafferentation. In analogy to trigeminal neuralgia, the possibility of ephaptic stimulation of neighboring, partially demyelinized axons through vascular loop compression of the nerve entry zone at the brainstem is discussed. In this cases a therapeutic effect of carbamazepine should be expected, although this could not be confirmed by a double-blind study against placebo in a random selection of patients (Hulshof and Vermaj, 1985). In individual cases with paroxysmal tinnitus due to a meningeoma (Espir et al., 1997) or with paroxysmal vertigo and tinnitus (Brandt and Dieterich, 1994), effective treatment has been achieved. Also surgery (microvascular decompression) has been performed in some patients (Moller et aL, 1993). Etiology This type of tinnitus can be caused by medication (many of the drugs can also lead to hearing defects), such as quinine, salicylate (dose dependent, reversible after 2-3 days), indometacine, carbamazepine, propranolol, levodopa, aminophyllin, coffeine, tetracycline, doxycycline, or salbutamol (for detailed review, see Brown et aL, 1981). Most cases remain etiologically unclear. Natural
Course
Drug-induced tinnitus disappears when the drug in question is withdrawn. Ototoxic drugs are exceptions to this rule. These drugs damage the cochlea and cause hearing loss that, in turn, leads to tinnitus. As a rule, if
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CRANIAL NERVES AND BRAIN STEM
the etiology is not clear, the tinnitus subsides spontaneously after a matter of weeks or months, recurring only during times of fatigue and stress. Courses of highly irritative tinnitus over many years are not unusual. For only 8-13% of the patients with chronic tinnitus the tinnitus increases with time. As a rule after IV2 years the tinnitus gets less loud and is no longer of central importance.
the brainstem (in analogy to trigeminus neuralgia) has been performed with the Gardner-Jannetta method (Moller et aL, 1993). Careful indication is mandatory. About half of the patients report some improvement. The surgery can deteriorate hearing, since the acoustic nerve is very vulnerable. The general lethality for the Gardner-Janetta operation is 1%. Ineffective or Obsolete
Practical Treatment A conclusive and generally accepted form of treatment is not known. However, the following approaches should be given careful consideration, which sometimes prove successful also after various attempts. They are almost exclusively prescribed by the ENT physician or at least implemented under her/his guidance. Counseling, Behavioral Therapy. In many instances simple psychotherapeutic measures improve the situation for the often highly disturbed, insecure, and suffering patients. They range from simple tinnitus counselling (Preyer and Booth, 1995) to relaxation programs (Goebel, 1992; Lindberg et aL, 1989) for patients in specialized hospitals. Masking. Many tinnitus patients perceive some relief when other sources of noise drown out the tinnitus. In straightforward cases, this can be achieved by listening to the radio before falling asleep. Sometimes also wide frequency noise is used in this context. Hearing aids often lead to suppression of tinnitus by intensifying audibility (House, 1989). Tinnitus Retraining Therapy. This a relatively new form of therapy for patients with tinnitus, hyperacusis, or both (Jastreboff and Jastreboff, 2000; Mattox et aL, 1997). This is a multidisciplinary approach to the patient utilizing didactic informational sessions, counseling, and the use of a device that presents constant low-level noise to the affected ear. Although the practitioners of TRT report 70-80% success rates, the treatment has the disadvantage of being lengthy, requiring up to 2 years. TRT is available in only a few centers that specialize in tinnitus, and therapists require specialized training. Cochlear Implants. Cochlear implants can lead to tinnitus reduction (Hazell et al., 1993; Souliere et aL, 1992). This therapy can be used only in deaf patients, since electrical stimulation damages the healthy cochlea (Portmann et ai, 1979). Vascular Decompression. A microvascular decompression at the root entry zone of the acoustic nerve in
Drug Therapy. Although there are numerous anecdotal responses to a variety of medications, a completely reliable and generally accepted form of treatment is not known (Dobie, 1999). The U.S. Food and Drug Administration has not approved any drug for the treatment of tinnitus. Although infusions of lidocaine reduce the loudness of tinnitus in most patients, this treatment has not been pursued due to considerable side effects. The same applies for oral analog tocanide HCl (Dobie, 1999). Lidocaine applications by means of local iontophoresis showed no effects (Dobie, 1999). A specific effect in tinnitus treatment has not been established for the following drugs: carbamazepine (Hulshof and Vermeij, 1985), cinnarizine, clonazepam, cyclandelate (a vasodolating agent) (Hester etal.^ 1998), flunarizine, nicotinic acid and derivatives, meclofenoxate, oxazepam, sulpuride, pentoxyphyllin, vitamine A, Gingko (von Wedel et al, 1995), baclofen (Moller, 1997; Westerberg et ai, 1996), betahistine, lamotrigine (Simpson et al., 1999), melatonin (Rosenberg et aL, 1998), caraverine (a quinoxaline derivative) (Domeisen et aL, 1998). A positive effect of sodium valproate (400 mg daily) in individual cases needs further examination (Menkes and Larson, 1998). Biofeedback. Either no or insignificant effects were achieved with biofeedback (Tonkin, 1985; Dobie, 1999). Surgical Measures. Surgery is not indicated for treatment of tinnitus alone. If for other reasons (e.g., tumor) a nerve must be severed, tinnitus is abated in only 4 5 % of patients and either remains or becomes even worse in 55% (House and Brackmann, 1981; Parving et al., 1992; Pulec, 1995). Miscellaneous. Acupuncture (Park et ai, 2000; Vilholm et at., 1998) and hyperbaric oxygen have not been shown to be successful (Lenarz et a/., 1999).
REFERENCES Badia, L., Parikh, A., and Brookes, G. B. (1994). Management of middle ear myoclonus. J. Laryngol. OtoL 108, 380-382.
TINNITUS Brandt, T., and Dieterich, M. (1994). Vestibular paroxysmia: Vascular compression of the eighth nerve? Lancet 1, 798-799. Bryce, G. E., and Morrison, M. D. (1998). Botulinum toxin treatment of essential palatal myoclonus tinnitus. / . Otolaryngol. 17, 213-216. Brown, D. R., Penny, J. E., Henley, C. M., Hodges, K. B., Kupetz, S. A., Glenn, D. W., and Jobe, P. C. (1981). Ototoxic drugs and noise. In "Tinnitus" (D. Evered and G. Lawrenson, Eds.), Ciba Foundation Symposium 85, pp. 151-171. Pitman, London. Coles, R. R. A. (1987). Epidemiology of tinnitus. In "Tinnitus" (J. W. P. Hazell, Ed.), pp. 46-70. Churchill-Livingstone, Edinburgh. Couloigner, V, Grayeli, A. B., Boccara, D., Julien, N., and Sterkers, O. (1999). Surgical treatment of the high jugular bulb in patients w^ith Meniere's disease and pulsatile tinnitus. Eur. Arch. Otorhinolaryngol 256, 224-229. Davis, A., and Refaie, A. E. (2000). Epidemiology of tinnitus. In "Tinnitus Handbook" (R. S. Tyler, Ed.), pp. 1-24. Singular, San Diego, CA. Dobie, R. A. (1999). A review of randomized clinical trials in tinnitus. Laryngoscope 109, 1202-1211. Domeisen, H., Hotz, M. A., and Hausler, R. (1998). Caroverine in tinnitus treatment. Acta Otolaryngol. (Stockh.) 118, 606607. Espir, M., lUingworth, R., Ceranic, B., and Luxon, L. (1997). Paroxysmal tinnitus due to a meningioma in the cerebellopontine angle. /. Neurol. Neurosurg. Psychiatry 62, 401-403. Fichter, M., and Goebel, G. (1996). Psychosomatische Aspekte des chronischen komplexen Tinnitus. Deutsches Arzteblatt. 93, A1771-A1776. Goebel, G. (1992). "Ohrgerausche: Psychosomatische Aspekte des komplexen chronischen Tinnitus: Vorkommen, Auswirkungen, Diagnostik und Therapie." Quintessenz Verl., Miinchen. Hazell, J. W. (1990). Tinnitus III: The practical management of sensorineural tinnitus./. Otolaryngol. 19, 11-18. Hazell, J. W., Jastreboff, P. J., Meerton, L. E., and Conway, M. J. (1993). Electrical tinnitus suppression: frequency dependence of effects. Audiology 32, 68-77. Hazell, J. W. R, and Sheldrake, J. B. (1992). Hyperacusis and tinnitus. In "Proceedings, IVth International Tinnitus Seminar Bordeaux, France," pp. 245-248. Kugler, Amsterdam/New York. Hester, O., Theilman, G., Green, W., and Jones, R. O. (1998). Cyclandelate in the management of tinnitus: A randomized, placebo-controlled study. Otolaryngol. Head Neck Surg. 118, 329-332. House, J. W. (1989). Therapies for tinnitus. Ann. J. Otol. 10, 163-165. House, J. W., and Brackmann, D. E. (1981). Tinnitus: Surgical treatment. In "Tinnitus" (D. Evere and G. Lawrenson, Eds.), Ciba Foundation Symposium 85, pp. 204-216. Pitman, London. Hulshof, J. H., and Vermeij, P. (1985). The value of carbamazepine in the treatment of tinnitus. ORL 47, 262-266. Jastreboff, P. J. (1990). Phantom auditory perception (tinnitus): Mechanisms of generation and perception. Neurosci. Res. 8, 221-254. Jastreboff, P. J., and Jastreboff, M. M. (2000). Tinnitus Retraining Therapy (TRT) as a method for treatment of tinnitus and hyperacusis patients./. Am. Acad. Audiol. 11, 162-177. Jastreboff, P. J., and Sasaki, C. T. (1994). An animal model of tinnitus: A decade of development. Ann. J. Otol. 15, 19-27. Jastreboff, P. J. (1995). A neuropsychological approach to tinnitus theory and practice. Whurr, London. Lamm, K. (1995). Rationale Grundlagen einer Innenohrtherapie. Otorhinolaryngol. Nova 5, 153-160. Lenarz, T. et al. (Eds) (1999). Tinnitus. HNO 47, 14-18.
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Lewis, J. E., Stephens, S. D., and McKenna, L. (1994). Tinnitus and Suicide. Clin Otolaryngol 19, 50-54. Lindberg, P., Scott, B., Melin, L., and Lyttkeus, L. (1989). The psychological treatment of tinnitus: an experimental evaluation. Behav. Res. Then 27: 593-603. Lockwood, A. H., Salvi, R. J., Coad, M. L., Towsley, M. L., Wack, D. S., and Murphy, B. W. (1998). The functional neuroanatomy of tinnitus. Evidence for limbic system links and neural plasticity. Neurology 50, 114-120. Mattox, D. E., Jastreboff, R, and Gray, W. (1997). Tinnitus Habituation Therapy: The University of Maryland Tinnitus and Hyperacusis Center Experience. Int. Tinnitus J. 3, 31-32. Menkes, D. B., and Larson, P. M. (1998). Sodium valproate for tinnitus. / . Neurol. Neurosurg. Psychiatry 65, 803. Moller, M. B., Moller, A. R., Jannetta, R J., and Jho, H. D. (1993). Vascular decompression surgery for severe tinnitus: Selection criteria and results. Laryngoscope 103, 421-427. Moller, A. R. (1997). A double-blind placebo-controlled trial of baclofen in the treatment of tinnitus. Am. J. Otol. 18, 268-269. [Comment] Olteanu-Nerbe, V., Uhl, E., Steiger, H.-J., Yousry, T , and Reulen, H.-J. (1997). Dural arteriovenous fistulas including the transverse and sigmoid sinuses: Results of treatment in 30 cases. Acta Neurochir. (Wien) 139, 307-318. Park, J., White, A. R., and Ernst, E. (2000). Efficacy of acupuncture as a treatment for tinnitus. Arch. Otolaryngol. Head Neck Surg. 126, 489-492. Parving, A., Tos, M., Thomsen, J., Miller, H., and Buchwald, C. (1992). Some aspects of life quality after surgery for acoustic neuroma. Arch. Otolaryngol. Head Neck Surg. 118, 1061-1064. Penner, M. J. (1992). Linking spontaneous otoacoustic emissions and tinnitus. Br. } . Audiol 26, 115-123. Portman, M., Cazals, Y., Negrevergne, M., and Aran, J. M. (1979). Temporary tinnitus suppression in man through electrical stimulation of the cochlea. Acta Otolaryngol. 87, 294-299. Preyer, S., and Booth, F. (1995). Tinnitusmodelle zur Verwendung bei der Tinnituscounsellingtherapie des chronischen Tinnitus. HNO 43, 338-351. Pulec, J. L. (1995). Cochlear nerve section for intractable tinnitus. Ear Nose Throat J. 74, 470-476. Robinson, P. J., and Hazell, J. W. (1989). Patulous eustachian tube syndrome: The relationship with sensorineural hearing loss. Treatment by eustachian tube diathermy. / . Laryngol. Otol. 103, 739-742. Rosenberg, S. I., Silverstein, H., Rowan, P. T , and Olds, M. J. (1998). Effect of melatonin on tinnitus. Laryngoscope 108, 3 0 5 310. Saeed, S. R., and Brookes, G. B. (1993). The use of Clostridium botulinum toxin in palatal myoclonus. A preliminary report. / . Laryngol. Otol. 107, 208-210. Shah, S. B., Lalwani, A. K., and Dowd, C. R (1999). Transverse/ sigmoid sinus dural arteriovenous fistulas presenting as pulsatile tinnitus. Laryngoscope 109, 54-58. Simpson, J. J., Gilbert, A. M., Weiner, G. M., and Davies, W. E. (1999). The assessment of lamotrigine, an antiepileptic drug, in the treatment of tinnitus. Am. J. Otol. 20, 627-631. Souliere, C. R. Jr., Kileny, P. R., Zwolan, T. A., and Kemink, J. I. (1992). Tinnitus suppression following cochlear implantation. A multifactorial investigation. Arch. Otolaryngol. Head Neck Surg. 118, 1291-1297. Staffen, W., Biesinger, E., Trinka, E., and Ladurner, G. (1999). The effect of lidocaine on chronic tinnitus: A quantitative cerebral perfusion study. Audiology 38, 53-57. Tonkin, J. P. (1985). Tinnitus: Clinical approaches to management. Curr. Ther. 37-40.
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Vilholm, O. J., Moller, K., and Jorgensen, K. (1998). Effect of traditional Chinese acupuncture on severe tinnitus: A double-blind, placebo-controlled, clinical investigation with open therapeutic control. Br. J. Audiol. 32, 197-204. V. Wedel, H., v. Wedel, U. C , Streppel, M., and Walger, M. (1997). Zur Effektivitat partieller und kompletter apparativer Maskierung beim chronischen Tinnitus. HNO 45, 690-694.
Westerberg, B. D., Roberson, J. B. Jr., and Stach, B. A. (1996). A double-blind placebo-controlled trial of baclofen in the treatment of tinnitus. Am. J. Otol. 17, 896-903. Williams, A., Goodenberger, D., and Calne, D. B. (1998). Palatal myoclonus following Herpes Zoster ameliorated by 5hydroxytryptophan and Carbidopa. Neurology 28, 358.
Tinnitus Ulrich Biittner and Alan H. Lockwood
Tinnitus is the false perception of tones and noises without an appropriate external stimulus. It is a common phenomenon. According to investigations in England, 17% of the population without noise-induced trauma had tinnitus that lasted more than 5min (Coles, 1987). The American Tinnitus Association estimates 50 million Americans have experienced the disorder. Tinnitus occurs largely in adults and becomes more frequent in old age. About 1 % of the population suffers from tinnitus with men more often affected than women. Acute tinnitus stops spontaneously in 60-80% of the cases. The chances of spontaneous recovery are small when the tinnitus lasts more than 3 months (chronic tinnitus). Most patients (85%) with continuous or intermittent tinnitus are relatively untroubled by the phenomenon (compensated tinnitus). For the remaining 1 5 % , the disorder may be a source of substantial disability (decompensated tinnitus). This is usually manifested by anxiety, inattentiveness, insomnia, depression, and/or other relatively nonspecific complaints. Some patients with depression have suicidal thoughts (2%). However, suicidal attempts without a history of depression are rare (Lewis et aL, 1994). Clinically, it is important to distinguish between subjective and objective tinnitus. In patients with objective tinnitus, the sounds are real, and may be heard with a stethoscope placed over the external auditory meatus or adjacent to the ear. Thus, objective tinnitus is not a phantom perception.
Souffle during Inspiration/Expiration Etiology This condition is due to an abnormally wide tuba auditiva eustachii, often caused by considerable weight loss. Treatment In individual cases a tube in the tuba Eustachii can lead to a narrowing (Robinson and Hazell, 1989).
Series of Sharp Clicks (Lasting Several Seconds to Minutes) Etiology This is called palatal myoclonus. It is a form of segmental myoclonus and is characterized by rhythmic contractions of the soft palate. There are often synchronous contractions of other voluntary muscles of the pharynx, larynx, face, neck, eyes, and occasionally the muscles of respiration. It is usually caused by a lesion in the pathways connecting the inferior olivary nucleus and the dentate nucleus. These lesions are usually seen on MRI scans where hypertrophy of the inferior olive may also be evident. Therapy
OBJECTIVE TINNITUS A distinction is made between the various noise types with etiological indications. Neurological Disorders: Course and Treatment, Second Edition Copyright 2003, Elsevier Science (USA). All rights reserved.
The disorder, once estabhshed, usually persists and is resistant to treatment. However, there are reports of responses to tetrabenazine, 5-HTP, trihexaphenadyl, and carbamazepine (Williams et al., 1998). Botulinum 165
166
CRANIAL NERVES AND BRAIN STEM
toxin injections may be tried in selected cases (Bryce and Morrison, 1998; Saeed and Brookes, 1993). The tensor veli palatini or the stapedius muscle can be transected surgically (Badia et al., 1994).
Vascular Bruit (Pulsatile Tinnitus) Etiology Vascular bruit is caused by (1) vascular stenoses or malformations of the head and neck, such as carotid stenosis and dural arteriovenous fistulas of the sigmoid or rarely other locations, or (2) vascular tumors of the petrous bone such as glomus tumor. Treatment
Spontaneous Otoacoustic Emissions (SOAE) Etiology Rarely, patients with SOAE will hear these sounds and complain of tinnitus (Penner, 1992). SOAEs are produced by movement of the cilia of the outer hair cells. While many normal people have SOAEs, most are unaware of their presence. These sounds are usually inaudible to others, but they are occasionally loud enough to be heard by an examiner. SOAEs can be detected by inserting very small microphones into the external auditory meatus and examining the spectra of recorded sounds.
SUBJECTIVE TINNITUS
Carotid stenoses are treated by endovascular dilatation or stenting or by open surgery. Dural arteriovenous fistulas are eliminted by transvenous or transarterial embolization or by surgical methods (Olteanu-Nerbe et aL, 1997). With dural fistulae more than 80% of the patients can achieve clinical resolution. The therapeutic outcome is better in less severe cases (Shah et aL^ 1999). Glomus tumors usually require surgical removal, possibly after transarterial embolization to reduce surgical blood loss.
Subjective Tinnitus with Rotational Vertigo
Continual Swishing Noise (Disappears when Pressure Is Applied to the Jugular Vein)
Sudden Hearing Loss
Etiology This has a venous origin, such as stenosis or external compression of the sigmoid sinus, high jugular bulb, aneurysm of the sigmoid sinus, or rarely intracranial hypertension. Treatment If compression by a tumor is identified as the cause, treatment depends on the nature of the neoplasm. The most common tumor, meningioma, requires surgery. Radiosurgery, an alternative method for small meningiomas using convergent X-ray beams does commonly not result in a dramatic shrinkage of the tumor volume and is therefore not a primary consideration in cases with a disturbing noise. High located jugular bulbs leading to Meniere's disease associated with a pulsatile component can be lowered surgically (Couloigner et aL, 1999). For other venous anomalies, venous obliteration by endovascular technique can be considered. The effect and tolerance of treatment can be tested by balloon test occlusion beforehand.
See information on Meniere's disease (Chapter 15).
Subjective Tinnitus with Hearing Defects Otosclerosis (Mostly Low-Frequency Tinnitus) Tinnitus subsides after surgery only in 30-50% of cases (House, 1989). It even might worsen.
ENT physicians use low-molecular-weight dextran, pentoxiphyllin, and nicotinic acid, although their success rate has not been established by controlled studies. Therapeutic effects have been reported with prednisolone (Lamm, 1995). Head Trauma (High Frequency, Ringing Tinnitus) Tinnitus after head trauma usually lasts only a couple of hours but can persist for years with inner ear lesions. There is no known treatment. Noise-Induced Trauma as a Result of Acute or Chronic Exposure After acute exposure therapeutic effects for cortisone in combination with hyperbaric oxygen have been reported (Lamm, 1995). Acoustic Neuroma Tinnitus is often continuous and high-frequency, on one side. It can precede the hearing defect. About 4 % of the neuromas present initially with tinnitus. Treat-
TINNITUS
merit options include surgery, after which tinnitus may persist (see below). Ototoxic
Medication
Certain aminoglycosides (especially canamycine, streptomycine, neomycine, bycomycine), heavy metals, and cisplatine can cause tinnitus. Treatment involves withdrawl from medication. Permanent deficits may persist.
Subjective Tinnitus without Hearing Defects Clinical Aspects Approximately only 10-20% of patients who complain of tinnitus do not suffer from concurrent hypacusis. Causing factors for tinnitus are often emotionally disturbing situations. About 10% of the patients complain about hyperacusis before the onset of tinnitus (Hazell and Sheldrake, 1992). Irrespective of its origin, tinnitus frequently causes major disturbance, particularly in quiet surroundings and at night (Fichter and Goebel, 1996). Patients react by becoming depressed and, in some cases, suicidal. Sleep is disturbed and patients complain about impaired memory and lack of concentration. Hearing loss, particularly in the high frequencies in the worse ear (often maximal at or about 4.0 kHz) is the most important risk factor or predictor for the development of sustained subjective tinnitus (Davis and Refaie, 2000). Some patients with tinnitus have hearing thesholds that are reportedly in the normal range. In these individuals, it is usually not possible to determine whether hearing thresholds have shifted toward the impaired range. Since thresholds are measured in dB, a logarithmic scale, substantial differences in sound energy may translate into a relatively small shift in thresholds. The exact location (central or peripheral) of the lesion is not known. An altered relation between the activity of outer and inner hair cells in the cochlea has been discussed (Jastreboff, 1990). Since tinnitus still persists after severance of the acoustic nerve, a central accentuation after primary peripheral lesion is likely (House and Brackmann, 1981). In the rat, abnormal activity has been recorded in the inferior colliculus with salicylate levels causing tinnitus (Jastreboff and Sasaki, 1994). This abnormal activity can be influenced by lidocaine. Lidocaine also affected the abnormally increased perfusion in the auditory cortex of a patient with chronic tinnitus using the SPECT method (Staffen et aL, 1999). In patients who could affect their tinnitus loudness by oral facial movements, PET studies suggest that the tinnitus
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experience arises in the central auditory system and not the cochlea (Lockwood et aL, 1998). In these patients, who all had unilateral tinnitus, changes in neural activity that paralleled changes in the loudness of tinnitus were found unilaterally in auditory cortical sites. This unilaterality contrasted with bilateral activation of auditory cortex that was associated with tonal stimuli delivered to the ear that the patients said their tinnitus was heard. Since cochlear activation was associated with bilateral activation whereas tinnitus was associated with unilateral activity, the investigators deduced that tinnitus was not of cochlear origin. In this same group of patients, who all had sensorineural hearing loss, tonal stimuli activated a more extensive portion of auditory cortex than was activated by identical stimuli delivered to control subjects with normal hearing. This expansion of cortical sites responsive to the stimuli demonstrated plastic changes in the central auditory system. This led to the hypothesis that tinnitus is due to plastic transformations of the central auditory system due to deafferentation, a condition that may be analogous to phantom pain sensations that may follow somatosensory deafferentation. In analogy to trigeminal neuralgia, the possibility of ephaptic stimulation of neighboring, partially demyelinized axons through vascular loop compression of the nerve entry zone at the brainstem is discussed. In this cases a therapeutic effect of carbamazepine should be expected, although this could not be confirmed by a double-blind study against placebo in a random selection of patients (Hulshof and Vermaj, 1985). In individual cases with paroxysmal tinnitus due to a meningeoma (Espir et al., 1997) or with paroxysmal vertigo and tinnitus (Brandt and Dieterich, 1994), effective treatment has been achieved. Also surgery (microvascular decompression) has been performed in some patients (Moller et aL, 1993). Etiology This type of tinnitus can be caused by medication (many of the drugs can also lead to hearing defects), such as quinine, salicylate (dose dependent, reversible after 2-3 days), indometacine, carbamazepine, propranolol, levodopa, aminophyllin, coffeine, tetracycline, doxycycline, or salbutamol (for detailed review, see Brown et aL, 1981). Most cases remain etiologically unclear. Natural
Course
Drug-induced tinnitus disappears when the drug in question is withdrawn. Ototoxic drugs are exceptions to this rule. These drugs damage the cochlea and cause hearing loss that, in turn, leads to tinnitus. As a rule, if
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the etiology is not clear, the tinnitus subsides spontaneously after a matter of weeks or months, recurring only during times of fatigue and stress. Courses of highly irritative tinnitus over many years are not unusual. For only 8-13% of the patients with chronic tinnitus the tinnitus increases with time. As a rule after IV2 years the tinnitus gets less loud and is no longer of central importance.
the brainstem (in analogy to trigeminus neuralgia) has been performed with the Gardner-Jannetta method (Moller et aL, 1993). Careful indication is mandatory. About half of the patients report some improvement. The surgery can deteriorate hearing, since the acoustic nerve is very vulnerable. The general lethality for the Gardner-Janetta operation is 1%. Ineffective or Obsolete
Practical Treatment A conclusive and generally accepted form of treatment is not known. However, the following approaches should be given careful consideration, which sometimes prove successful also after various attempts. They are almost exclusively prescribed by the ENT physician or at least implemented under her/his guidance. Counseling, Behavioral Therapy. In many instances simple psychotherapeutic measures improve the situation for the often highly disturbed, insecure, and suffering patients. They range from simple tinnitus counselling (Preyer and Booth, 1995) to relaxation programs (Goebel, 1992; Lindberg et aL, 1989) for patients in specialized hospitals. Masking. Many tinnitus patients perceive some relief when other sources of noise drown out the tinnitus. In straightforward cases, this can be achieved by listening to the radio before falling asleep. Sometimes also wide frequency noise is used in this context. Hearing aids often lead to suppression of tinnitus by intensifying audibility (House, 1989). Tinnitus Retraining Therapy. This a relatively new form of therapy for patients with tinnitus, hyperacusis, or both (Jastreboff and Jastreboff, 2000; Mattox et aL, 1997). This is a multidisciplinary approach to the patient utilizing didactic informational sessions, counseling, and the use of a device that presents constant low-level noise to the affected ear. Although the practitioners of TRT report 70-80% success rates, the treatment has the disadvantage of being lengthy, requiring up to 2 years. TRT is available in only a few centers that specialize in tinnitus, and therapists require specialized training. Cochlear Implants. Cochlear implants can lead to tinnitus reduction (Hazell et al., 1993; Souliere et aL, 1992). This therapy can be used only in deaf patients, since electrical stimulation damages the healthy cochlea (Portmann et ai, 1979). Vascular Decompression. A microvascular decompression at the root entry zone of the acoustic nerve in
Drug Therapy. Although there are numerous anecdotal responses to a variety of medications, a completely reliable and generally accepted form of treatment is not known (Dobie, 1999). The U.S. Food and Drug Administration has not approved any drug for the treatment of tinnitus. Although infusions of lidocaine reduce the loudness of tinnitus in most patients, this treatment has not been pursued due to considerable side effects. The same applies for oral analog tocanide HCl (Dobie, 1999). Lidocaine applications by means of local iontophoresis showed no effects (Dobie, 1999). A specific effect in tinnitus treatment has not been established for the following drugs: carbamazepine (Hulshof and Vermeij, 1985), cinnarizine, clonazepam, cyclandelate (a vasodolating agent) (Hester etal.^ 1998), flunarizine, nicotinic acid and derivatives, meclofenoxate, oxazepam, sulpuride, pentoxyphyllin, vitamine A, Gingko (von Wedel et al, 1995), baclofen (Moller, 1997; Westerberg et ai, 1996), betahistine, lamotrigine (Simpson et al., 1999), melatonin (Rosenberg et aL, 1998), caraverine (a quinoxaline derivative) (Domeisen et aL, 1998). A positive effect of sodium valproate (400 mg daily) in individual cases needs further examination (Menkes and Larson, 1998). Biofeedback. Either no or insignificant effects were achieved with biofeedback (Tonkin, 1985; Dobie, 1999). Surgical Measures. Surgery is not indicated for treatment of tinnitus alone. If for other reasons (e.g., tumor) a nerve must be severed, tinnitus is abated in only 4 5 % of patients and either remains or becomes even worse in 55% (House and Brackmann, 1981; Parving et al., 1992; Pulec, 1995). Miscellaneous. Acupuncture (Park et ai, 2000; Vilholm et at., 1998) and hyperbaric oxygen have not been shown to be successful (Lenarz et a/., 1999).
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