The use of intravenous lignocaine in the diagnosis and treatment of tinnitus

Review of Pharmacotherapy for Tinnitus

Various medications are currently used in the treatment of tinnitus, including anesthetics, antiarrhythmics, anticonvulsants, antidepressants, antihistamines, antipsychotics, anxiolytics, calcium channel blockers, cholinergic antagonists, NMDA antagonists, muscle relaxants, vasodilators, and vitamins. To date, however, no medications have been specifically approved to treat tinnitus by the US Food and Drug Administration (FDA). In addition, medicines used to treat other diseases, as well as foods and other ingested materials, can result in unwanted tinnitus. These include alcohol, antineoplastic chemotherapeutic agents and heavy metals, antimetabolites, antitumor agents, antibiotics, caffeine, cocaine, marijuana, nonnarcotic analgesics and antipyretics, ototoxic antibiotics and diuretics, oral contraceptives, quinine and chloroquine, and salicylates. This review, therefore, describes the medications currently used to treat tinnitus, including their mechanisms of action, therapeutic effects, dosages, and side-effects. In addition, this review describes the medications, foods, and other ingested agents that can induce unwanted tinnitus, as well as their mechanisms of action.

Current Validated Medical Treatments: Pharmacologic Interventions

The search for an effective medication that will eliminate tinnitus has a long history. Currently, no drugs exist that universally cure tinnitus. Pharmacologic interventions that have been investigated can be divided into those that attempt to eliminate the perception of tinnitus, and those that are designed to treat the negative comorbidities associated with tinnitus, thereby mitigating tinnitus' negative impact on quality of life. A third category of drugs can also be considered that addresses an identified pathologic condition that has tinnitus as an associated symptom (for example, Meniere's disease, otosclerosis, migraine-associated vertigo). This third category is not addressed.

Tinnitus and sound intolerance: evidence and experience of a Brazilian group

Introduction

Tinnitus and sound intolerance are frequent and subjective complaints that may have an impact on a patient's quality of life.

Objective

To present a review of the salient points including concepts, pathophysiology, diagnosis and approach of the patient with tinnitus and sensitivity to sounds.

Methods

Literature review with bibliographic survey in LILACS, SciELO, Pubmed and MEDLINE database. Articles and book chapters on tinnitus and sound sensitivity were selected. The several topics were discussed by a group of Brazilian professionals and the conclusions were described.

Results

The prevalence of tinnitus has increased over the years, often associated with hearing loss, metabolic factors and inadequate diet. Medical evaluation should be performed carefully to guide the request of subsidiary exams. Currently available treatments range from medications to the use of sounds with specific characteristics and meditation techniques, with variable results.

Conclusion

A review on tinnitus and auditory sensitivity was presented, allowing the reader a broad view of the approach to these patients, based on scientific evidence and national experience.

The Management and Outcomes of Pharmacological Treatments for Tinnitus

Tinnitus, a phantom sensation experienced by people around the world, currently is endured without a known cure. Some find the condition tolerable, while others are tortured on a daily basis from the incessant phantom noises. For those who seek treatment, oftentimes, they have a comorbid condition (e.g., depression, anxiety, insomnia), which is treated pharmaceutically. These products aim to reduce the comorbities associated with tinnitus thereby minimizing the overall burden present. Because of the phantom nature of tinnitus, it is often compared to neurologic pain. Since pain can be managed with pharmaceutical options, it is reasonable to assume that similar agents might work to alleviate tinnitus. The effects of antidepressants, benzodiazepines, anticonvulsants, and glutamate antagonists are reviewed in this paper. Table 1 summarizes the pharmaceutical products discussed. Due to the variety of comorbid factors and potential causes of tinnitus, there may not be one pharmaceutical treatment that will combat every type of tinnitus. Nevertheless, a product that finally addresses the true cause of tinnitus, and not just its comorbidities, will benefit millions of people worldwide.

Pathophysiology of Tinnitus

The hypothesis is presented that certain forms of tinnitus are related to abnormal phase-locking of discharges in groups of auditory nerve fibers. Recent developments in auditory neurophysiology have shown that neural coding of the temporal pattern of sounds plays an important role in the analysis of complex sounds. In addition, it has been demonstrated that when some other cranial nerves are damaged, artificial synapses can occur between individual nerve fibers such that ephaptic transmission between nerve fibers is facilitated. Such “crosstalk” between auditory nerve fibers is assumed to result in phase-locking of the spontaneous activity of groups of neurons which in the absence of external sounds creates a neural pattern that resembles that evoked by sounds.

Treatment of Tinnitus with Tocainide Hydrochloride

Intravenous (IV) injection of lidocaine was used in patients with tinnitus for combined treatment with oral anticonvulsants carbamazepine (Tegretol) and primidone (Mysoline). In most cases, the high complication rate with these drugs precluded their long-term use. Tocainide hydrochloride (HCI), a primary amine analog of lidocaine, can be taken orally and was evaluated for the use in the treatment of tinnitus. A double-blind study in which one group received 200 mg tocainide HCI four times a day and one group received a placebo revealed no significant differences in tinnitus relief between the two groups. A single-blind study in which 600 mg tocainide HCI four times a day was administered showed 80% to 90% tinnitus relief in five of the six patients who tolerated the drug. Tocainide HCI treatment of tinnitus is promising.

Muscle Contractions and Auditory Perception in Tinnitus Patients and Nonclinical Subjects

Evidence has been accumulating linking subjective tinnitus to the somatosensory system. Most subjective tinnitus patients can change the psychoacoustic attributes of their tinnitus with forceful head and neck contractions. This study assessed the significance of such somatic modulation of tinnitus by testing nonclinical subjects. Like tinnitus patients, about 80% of nonclinical subjects, who had ongoing tinnitus at the time of testing (whether or not they were previously aware of it), could modulate their tinnitus with head and neck contractions. Over half of those with no tinnitus at the time of testing could elicit a tinnitus-like auditory perception with head and neck contractions. The finding that forceful head and neck contractions, as well as loud sound exposure, were significantly more likely to modulate ongoing auditory perception in people with tinnitus than in those without tinnitus supports the concept of a neural threshold for tinnitus. Somatic influences upon auditory perception are not limited to tinnitus sufferers but appear to be a fundamental property of the auditory system.

Chronic tinnitus: an interdisciplinary challenge

BACKGROUND

Tinnitus is defined as the perception of sound in the absence of a corresponding external acoustic stimulus. It is a common problem that markedly impairs the quality of life of about 1% of the general population.

METHODS

We selectively reviewed the pertinent literature to provide an overview of the current treatment options for chronic tinnitus.

RESULTS

Cognitive behavioral therapy is effective and is the best studied of all currently available treatments. All patients should have a therapeutic interview for counseling. Auditory stimulation can also lessen tinnitus: It is used in tinnitus maskers and hearing aids, as well as in tinnitus retraining therapy. An improved understanding of the neural mechanisms of tinnitus has led to the development of innovative techniques of neuromodulation and neurostimulation, but these are still experimental. Drugs are indicated only for the treatment of tinnitus-associated symptoms such as depression, sleep disturbances, and anxiety.

CONCLUSION

There are many ways to treat chronic tinnitus, and new treatments are now being developed. As tinnitus has many causes and can be associated with many different comorbid disturbances, multidisciplinary diagnostic evaluation and treatment are important. For many tinnitus patients, long-term therapeutic success depends on the maintenance of a therapeutic relationship with the treating physician, so that the physician and the patient can work together to give careful consideration to each newly proposed diagnostic test or treatment step.

Anticonvulsants for tinnitus

BACKGROUND

Tinnitus is the perception of sound or noise in the absence of an external or internal acoustic stimulation. It is a common and potentially distressing symptom for which no adequate therapy exists.

OBJECTIVES

To assess the effectiveness of anticonvulsants in patients with chronic tinnitus.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, CENTRAL (2010, Issue 2), MEDLINE, EMBASE, bibliographies and additional sources for published and unpublished trials. The date of the most recent search was 26 May 2010.

SELECTION CRITERIA

We selected randomised controlled trials in patients with chronic tinnitus comparing orally administered anticonvulsants with placebo. The primary outcome was improvement in tinnitus measured with validated questionnaires. Secondary outcomes were improvement in tinnitus measured with self-assessment scores, improvement in global well-being or accompanying symptoms, and adverse drug effects.

DATA COLLECTION AND ANALYSIS

Three authors assessed risk of bias and extracted data independently.

MAIN RESULTS

Seven trials (453 patients) were included in this review. These studies investigated four different anticonvulsants: gabapentin, carbamazepine, lamotrigine and flunarizine. The risk of bias of most studies was 'high' or 'unclear'. Three studies included a validated questionnaire (primary outcome). None of them showed a significant positive effect of anticonvulsants. One study showed a significant negative effect of gabapentin compared to placebo with an increase in Tinnitus Questionnaire (TQ) score of 18.4 points (standardised mean difference (SMD) 0.82, 95% confidence interval (CI) 0.07 to 1.58). A second study showed a positive, non-significant effect of gabapentin with a difference compared to placebo of 2.4 points on the Tinnitus Handicap Inventory (THI) (SMD -0.11, 95% CI -0.48 to 0.25). When the data from these two studies are pooled no effect of gabapentin is found (SMD 0.07, 95% CI -0.26 to 0.40). A third study reported no differences on the THI after treatment with gabapentin compared to placebo (exact numbers could not be extracted from the article).A meta-analysis of 'any positive effect' (yes versus no) based on a self-assessment score (secondary outcome) showed a small favourable effect of anticonvulsants (RD 14%, 95% CI 6% to 22%). A meta-analysis of 'near or total eradication of tinnitus annoyance' showed no effect of anticonvulsants (risk difference (RD) 4%, 95% CI -2% to 11%). Side effects of the anticonvulsants used were experienced by 18% of patients.

AUTHORS' CONCLUSIONS

Current evidence regarding the effectiveness of anticonvulsants in patients with tinnitus has significant risk of bias. There is no evidence from studies performed so far to show that anticonvulsants have a large positive effect in the treatment of tinnitus but a small effect (of doubtful clinical significance) has been demonstrated.

Medical treatment of tinnitus

One of the most frustrating clinical problems for both otolaryngologist and patient is having to deal with the symptom of tinnitus. From the patient's point of view, frustration stems from the fact that this often unrelenting symptom can lead to a total disruption of a productive lifestyle, and in a number of instances, proves to be a tragically fatal symptom as the patients turn to suicide as a final solution. The otolaryngologist has been frustrated because until recently he has had little more than sympathy to offer the patient. This has led to a helpless feeling between both parties.

Emerging pharmacotherapy of tinnitus

Tinnitus, the perception of sound in the absence of an auditory stimulus, is perceived by about 1 in 10 adults, and for at least 1 in 100, tinnitus severely affects their quality of life. Because tinnitus is frequently associated with irritability, agitation, stress, insomnia, anxiety and depression, the social and economic burdens of tinnitus can be enormous. No curative treatments are available. However, tinnitus symptoms can be alleviated to some extent. The most widespread management therapies consist of auditory stimulation and cognitive behavioral treatment, aiming at improving habituation and coping strategies. Available clinical trials vary in methodological rigor and have been performed for a considerable number of different drugs. None of the investigated drugs have demonstrated providing replicable long-term reduction of tinnitus impact in the majority of patients in excess of placebo effects. Accordingly, there are no FDA or European Medicines Agency approved drugs for the treatment of tinnitus. However, in spite of the lack of evidence, a large variety of different compounds are prescribed off-label. Therefore, more effective pharmacotherapies for this huge and still growing market are desperately needed and even a drug that produces only a small but significant effect would have an enormous therapeutic impact. This review describes current and emerging pharmacotherapies with current difficulties and limitations. In addition, it provides an estimate of the tinnitus market. Finally, it describes recent advances in the tinnitus field which may help overcome obstacles faced in the pharmacological treatment of tinnitus. These include incomplete knowledge of tinnitus pathophysiology, lack of well-established animal models, heterogeneity of different forms of tinnitus, difficulties in tinnitus assessment and outcome measurement and variability in clinical trial methodology.

PHARMACOLOGICAL TREATMENTS FOR TINNITUS: NEW AND OLD

Subjective tinnitus, the phantom ringing or buzzing sensation that occurs in the absence of sound, affects 12-14% of adults; in some cases the tinnitus is so severe or disabling that patients seek medical treatment. However, although the economic and emotional impact of tinnitus is large, there are currently no FDA-approved drugs to treat this condition. Clinical trials are now underway to evaluate the efficacy of N-methyl-d-aspartate (NMDA) and dopamine D(2) antagonists, selective serotonin reuptake inhibitors (SSRIs), γ-aminobutyric acid (GABA) agonists and zinc dietary supplements. Previous off-label clinical studies, while not definitive, suggest that patients with severe depression may experience improvement in their tinnitus after treatment with antidepressants such as nortriptyline or sertraline. A small subpopulation of patients with what has been described as "typewriter tinnitus" have been shown to gain significant relief from the anticonvulsant carbamazepine. Preliminary studies with misoprostol, a synthetic prostaglandin E1 analogue, and sulpiride, a dopamine D(2) antagonist, have shown promise. Animal behavioral studies suggest that GABA transaminase inhibitors and potassium channel modulators can suppress tinnitus. Additionally, improvements in tinnitus have also been noted in patients taking melatonin for significant sleep disturbances. Like other complex neurological disorders, one drug is unlikely to resolve tinnitus in all patients; therapies targeting specific subgroups are likely to yield the greatest success.

Ototoxic drugs and noise

Drugs that produce tinnitus can be subdivided into those which produce temporary or permanent hearing loss and those which apparently do not cause any hearing loss. The tinnitus occurring with drugs of the first group is probably secondary to the hearing loss. However, most of the drugs that produce tinnitus without an accompanying hearing loss probably do so because of their effect on biogenic amines in the central nervous system and/or as an extension of their proconvulsant side-effects. A pre-existing cochlear impairment is the underlying factor in most patients who experience tinnitus. Not only can ototoxic drugs or high levels of noise produce cochlear impairment but the interaction of the two can place humans in more jeopardy than when exposed to either agent alone. Chloramphenicol has little ototoxic potential when administered systemically in humans. However, our studies show that when chloramphenicol is combined with noise exposure in rats, considerably more cochlear damage results than from the noise alone (chloramphenicol alone does no produce any cochlear damage). We are presently conducting more detailed studies of this ototoxic interaction to determine whether it occurs with other antibiotics (such as erythromycin) which are also commonly considered to have minimal ototoxicity.

Drugs in the treatment of tinnitus

Many drugs and some foods can cause or aggravate tinnitus in some patients. These substances should be identified and withdrawn. Tinnitus may be improved by the treatment of associated conditions, infections, or hearing loss with appropriate drugs--hypotensives, antibiotics, vasodilators, fluoride or thyroxine. Intravenous lignocaine can temporarily reduce or abolish tinnitus in many patients but can aggravate existing tinnitus in some and may have no effect on others. Analogy with pain of central origin suggests that the beneficial effects of lignocaine (lidocaine) may be due to its anticonvulsant action. Lignocaine is used as a test to distinguish between different mechanisms of tinnitus and to predict responses to oral anticonvulsants. Dramatic responses with lignocaine are usually associated with cochlear hearing loss and often with comparable though less marked responses to oral anticonvulsants. Patients who do not benefit from lignocaine do not respond to oral anticonvulsants. The action of anticonvulsants is often potentiated by tricyclic antidepressants. The majority of patients who respond to lignocaine can also have their tinnitus effectively masked, as predicted, on a tinnitus synthesizer. A small proportion respond to masking and not to lignocaine and a small proportion to lignocaine and not to masking. Beneficial effects of masking and anticonvulsants are cumulative. Anticonvulsants may also produce subjective improvement in clarity, improved tolerance of hearing aids and increased masking benefit when a hearing aid is worn.

Tinnitus treatment: state of the art

Clinical and scientific research has opened up a wide range of options for treating patients with tinnitus. Many of these options are sophisticated and are delivered through specialist tinnitus clinics. However tinnitus is a very common complaint. Most patients with tinnitus need to be satisfactorily cared for by front line clinicians. This chapter describes how one clinician who has looked after some thousands of patients with tinnitus looks after them now. It describes the model I use to explain tinnitus to the patient and develop a management plan. It describes how I assess patients with tinnitus. It lists the treatment options available. It describes the management provided at the first (and usually only) encounter. It stresses the value of a written report. It describes further management and onward referral. It describes my use of drugs in those patients for whom the tinnitus remains overwhelming.

General review of tinnitus: prevalence, mechanisms, effects, and management

Tinnitus is an increasing health concern across all strata of the general population. Although an abundant amount of literature has addressed the many facets of tinnitus, wide-ranging differences in professional beliefs and attitudes persist concerning its clinical management. These differences are detrimental to tinnitus patients because the management they receive is based primarily on individual opinion (which can be biased) rather than on medical consensus. It is thus vitally important for the tinnitus professional community to work together to achieve consensus. To that end, this article provides a broad-based review of what is presently known about tinnitus, including prevalence, associated factors, theories of pathophysiology, psychological effects, effects on disability and handicap, workers' compensation issues, clinical assessment, and various forms of treatment. This summary of fundamental information has relevance to both clinical and research arenas.

The Inhibitory Effect of Intravenous Lidocaine Infusion on Tinnitus after Translabyrinthine Removal of Vestibular Schwannoma: A Double-Blind, Placebo-Controlled, Crossover Study

OBJECTIVE

Intravenous infusion of lidocaine has previously been demonstrated to have a transient inhibitory effect on tinnitus in 60% of individuals. The site of action has variously been proposed as the cochlea, the cochlea nerve, and the central auditory pathways. To determine whether a central site of action exists, this study investigated the effect of intravenous infusion of lidocaine in individuals with tinnitus who had previously undergone translabyrinthine excision of a vestibular schwannoma, which involves division of the cochlear nerve.

STUDY DESIGN

Double-blind, placebo-controlled, crossover study.

SETTING

University hospital.

PATIENTS

Patients who had undergone translabyrinthine removal of a unilateral, sporadic, and histologically proven vestibular schwannoma in the last decade and who had reported postoperative tinnitus at follow-up were identified from a departmental database. Sixteen patients participated (12 men and 4 women). The mean age (+/- standard deviation) of the patients was 58 +/- 8.6 years, and the meantime since operation was 24.3 +/- 7.3 months.

INTERVENTION

Solutions of 2% lidocaine hydrochloride and sodium chloride 0.9% were prepared in identical randomized vials. The volume required for 1.5 ml/kg body weight lidocaine was calculated, and this volume was given over 5 minutes for either vial. Blood pressure, pulse oximetry, and cardiac monitoring were set up and performed throughout the infusions. All investigators were blinded.

OUTCOME MEASURES

Patient-completed visual analogue scale measures of tinnitus intensity, pitch, and distress, performed before infusion, 5 minutes after infusion onset, and 20 minutes after infusion onset.

RESULTS

A significant difference (Wilcoxon signed-rank test, p < 0.05) between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 5 min postinfusion) of tinnitus loudness (p = 0.036), pitch (p = 0.026), and distress (p = 0.04). No significant difference between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 20 min postinfusion) of tinnitus loudness (p = 0.066), pitch (p = 0.173), and distress (p = 0.058). The indication is of a short-lasting inhibitory effect on tinnitus of lidocaine infusion compared with saline placebo in patients who have undergone translabyrinthine excision of a vestibular schwannoma.

CONCLUSION

Intravenous infusion of lidocaine has a statistically significant inhibitory effect on tinnitus in patients who have previously undergone translabyrinthine removal of a vestibular schwannoma. The site of action of lidocaine in this instance must be in the central auditory pathway, as the cochlear and vestibular nerves are sectioned during surgery, and this finding has important implications for the task of identifying other agents that will have a similar tinnitus-inhibiting effect.

Objective evaluation of the effects of intravenous lidocaine on tinnitus

OBJECTIVE

Tinnitus is one of the most common and distressing otological symptoms. Although numerous therapeutic modalities have been tried, there is no consensus regarding effective therapeutic agents up to now. The effects of lidocaine on tinnitus have been reported in literature using either subjective or audiologic tests. Nevertheless, the otoacoustic emissions (OAEs) have not been utilized to demonstrate lidocaine's effect on the cochlea in the English literature. The aim of this study was to evaluate the effect of lidocaine on tinnitus by considering the alterations with tinnitus, it induces on OAEs and subjective symptoms.

METHODS

This study was performed in 30 patients with tinnitus. Twenty-eight of the patients had normal hearing and two of them evidenced mild sensorineural hearing loss. To determine the severity of tinnitus, the patients were required to fill out a tinnitus scoring scale before lidocaine infusion on the same day. Then, lidocaine was administered intravenously to each patient at a dose of 1.5 mg/kg body weight over a period of 30 min. Spontaneous otoacoustic emissions (SOAEs) and distortion product otoacoustic emissions (DPOAEs) were measured three times; namely before lidocaine injection, at 25 min after injection and on the next day. The severity of tinnitus was scored again 1 d, 1 wk and 1 mo after lidocaine administration.

RESULTS

Immediately after infusion, four patients (13.3%) declared total suppression of tinnitus, whereas three patients (10%) reported only partial relief in tinnitus subjectively. The patients, who had a subjective improved response (group 1) were compared with the patients, who had no response (group 2). Statistically significant changes (p<0.05) in DPOAE response/growth or input/output (I/O) functions were observed at 1, 2, 3, 4 and 6 kHz frequencies in lidocaine responders and at 1, 2, 3, 4 and 5 kHz frequencies in no responders at different primary stimulus levels. Statistically significant changes (p<0.05) were seen at 2 kHz for 53 dB and at 3 kHz for 62 dB SPL primaries in both groups. When the significant results of these two groups were compared with each other, differences were found insignificant.

CONCLUSION

Systematic OAE measurements revealed that no changes occurred in SOAE and DPOAE levels in that alterations disappeared the next day. Subjective relief from tinnitus was stated in some of the patients and lasted for 4 wk at longest.

Effects of lidocaine on basilar membrane vibration in the guinea pig

The effects of lidocaine on basilar membrane (BM) vibration and compound action potential (CAP) were studied in guinea pigs in order to elucidate the site of lidocaine action in the cochlea. BM vibration was measured with a laser Doppler vibrometer through an opening made in the lateral bony wall of the scala tympani at the basal turn. Ten min after local administration of lidocaine (250 microg) into the scala tympani, the velocity of BM vibration and the CAP amplitude decreased significantly at around the characteristic frequency of the stimulus sound (p < 0.05). The maximum decreases were 4 dB in the velocity of the BM vibration and 40 dB in the CAP amplitude. In contrast, such changes were not observed after i.v. injection of lidocaine (1.5 mg/kg). These results suggest that when lidocaine is administered locally in the cochlea it acts not only on the cochlear nerve but also on the outer hair cells.

Lidocaine test in patients with tinnitus: rationale of accomplishment and relation to the treatment with carbamazepine

OBJECTIVES

There is strong evidence in the literature about the effect of local anesthetics such as lidocaine in controlling tinnitus; these agents act by stabilizing hair cell membrane and cochlear nerve fibers. However, the effect of intravenous lidocaine is transient, and its oral analog (tocainide) does not have the same efficacy for long-term treatment in patients with tinnitus. Some oral anti-epileptic drugs (carbamazepine, for instance) have been used alternatively in several studies. The aim of this work is to evaluate the response to intravenous lidocaine in patients with intractable tinnitus and the effect of oral carbamazepine in long-term maintenance of tinnitus relief.

PATIENTS AND METHODS

We studied prospectively 50 patients (28 females and 22 males; mean age 50.9 years) who underwent the lidocaine test, performed by a 3-min intravenous infusion of 2% lidocaine chloridrate. The patients who experienced any relief after the test started treatment with oral carbamazepine in ascending dosages (50-600 mg/day).

RESULTS

The results were classified as tinnitus abolition (18%), marked relief (32%), partial relief (26%), unchanged (22%), or worsening (2%). The lidocaine test showed favorable results in 76% of patients, especially those with bilateral tinnitus (P < 0.001). Afterwards, 50% of patients treated with carbamazepine maintained the improvement of tinnitus (P = 0.0034).

CONCLUSION

The authors conclude that intravenous lidocaine is effective in reducing intractable tinnitus and that there is a close association between lidocaine and oral carbamazepine effects. Therefore, carbamazepine can be used for the treatment of tinnitus when the patient achieves improvement of symptom after the lidocaine test.

Micromechanical effects in the cochlea of tetracaine

Local anesthetics applied in the tympanic cavity have earlier been shown to affect the gross receptor potentials in reducing the cochlear microphonics and increasing the positive summating potential. To study the effects of this drug on the mechanical responses in the cochlea, vibrations were measured using laser heterodyne interferometry in an isolated in vitro temporal bone preparation from the guinea pig. Measurements were made at a set of frequencies in the fourth cochlear turn from the Hensen's cells and the outer hair cells in response to sound applied to the ear. The tuning curves of the fundamental and the second harmonic components of the vibratory responses were plotted. When 2 mM tetracaine was applied, the high frequency slope of the second harmonic curve shifted down in frequency, this caused the frequency of the maximum of second harmonic tuning to shift down. These changes were reversible when tetracaine was washed out. Observations were also made in the temporal bone preparation in vitro with a confocal microscope. Fluorescent probes were used to label various structures in the organ of Corti. Optical sections were obtained by tilting the organ permitting a view from the side like a radial section through the organ. Images were acquired before, during and after application of tetracaine and were later analyzed with a computer program. Simultaneously, cochlear microphonics and the summating potential were obtained to monitor the electrical response of the preparation. Although the cochlear microphonics and summating potential decreased when 2 mM tetracaine was applied, structural changes were not measurable in the organ of Corti. The decrease was reversible when tetracaine was washed out. It is concluded that tetracaine affected the high frequency part of the non-linear second harmonic component, possibly by lowering the stiffness of the stereocilia bundle or the body of the outer hair cells.

Positron emission tomography of cortical centers of tinnitus

Tinnitus is associated with a wide variety of disorders in the auditory system. Whether generated peripherally or centrally, tinnitus is believed to be associated with activity in specific cortical regions. The present study tested the hypothesis that these cortical centers subserve the generation, perception and processing of the tinnitus stimulus and that these processes are suppressed by lidocaine and masking. Positron emission tomography was used to map the tinnitus-specific central activity. By subtracting positron emission tomography images of regional cerebral blood flow distribution obtained during suppression of the tinnitus from positron emission tomography images obtained during the habitual tinnitus sensation, we were able to identify brain areas concerned with the cerebral representation of tinnitus. Increased neuronal activity caused by tinnitus occurred predominantly in the right hemisphere with significant foci in the middle frontal and middle temporal gyri, in addition to lateral and mesial posterior sites. The results are consistent with the hypothesis that the sensation of tinnitus is associated with activity in cortical regions functionally linked to subserve attention, emotion and memory. For the first time, the functional anatomy of conditions with and without the habitual tinnitus sensation was obtained and compared in the same subjects.

Alterations in average spectrum of cochleoneural activity by long-term salicylate treatment in the guinea pig: a plausible index of tinnitus

Salicylate, one of the most widely used drugs, produces at repetitive high doses reversible tinnitus and hearing loss. Neural correlates of hearing loss have long been established, whereas they remain elusive for tinnitus. The average spectrum of electrophysiological cochleoneural activity (ASECA), a measure of spontaneous auditory nerve activity, was monitored in guinea pigs over weeks of salicylate administration. Auditory nerve compound action potential (CAP) was also recorded to monitor acoustic sensitivity. In the first days of treatment, ASECA decreased acutely during hours after salicylate administration; after several days this decrease could be reduced. Over weeks of treatment the level of ASECA increased progressively. No change in CAP threshold was observed. The ASECA decrease induced by a contralateral broadband noise remained unchanged. At the end of treatment, acoustic tuning of ASECA showed a partially decreased sensitivity. After cessation of treatment the ASECA level returned progressively to initial values. In control animals delivery of an ipsilateral acoustic noise could reproduce the ASECA increase observed in long-term salicylate-treated animals. This white noise was of moderate sound pressure level and it elevated slightly CAP thresholds at high frequencies. These data provide evidence for salicylate-induced ASECA alterations without changes in CAP thresholds, in accord with clinical reports of tinnitus being the first subjective sign of salicylate ototoxicity. The similarities in occurrence, development, reversibility, frequency content, and acoustic level support the idea that ASECA changes, which indicates alterations of spontaneous eighth nerve activity and reflects the presence of salicylate-induced high-pitch tinnitus.

The mechanism and site of action of lidocaine hydrochloride in guinea pig inner ear

Lidocaine was applied to the round window (RW) in order to localize its site of action in the cochlea. Cochlear microphonic (CM), summating potential (SP), and compound action potential (CAP) input/output functions were measured to a 16 kHz tone burst to assess the functional changes of the cochlea. In separate experiments, the effect of lidocaine on the whole cell current of isolated outer hair cells (OHC) was studied. A dose of 2 microliters of 40 mM lidocaine in saline solution, when applied to the RW, caused a small change in all measured variables, indicating a passage of the drug through the RW membrane to sites of action. However, 160 mM of lidocaine further decreased CM, SP, and CAP by a total of 40% from the control. A partial recovery occurred for CM during the 30 min follow-up period. CAP and SP continued to decline. In isolated OHCs, lidocaine decreased the whole cell current in a dose-dependent fashion. The KD for lidocaine effect on OHCs was 7 mM. Our in vivo results indicate that lidocaine affects OHCs and reduces CM, causing a subsequent reduction in SP and CAP. The increased effect of lidocaine on CAP and SP, while CM is recovering, suggests an additional specific effect of lidocaine on the cochlear nerve and/or on inner hair cells. Considering that lidocaine alters OHC current (in isolated hair cells) and that lidocaine does not affect endocochlear potential [Laurikainen et al. Acta Otolaryngol (Stockh) 1991: 112: 800-9], the observed CM changes are most likely due to an in vivo effect on OHCs. Thus, the early effect of lidocaine on the cochlea appears to be due to a significant change in organ of Corti function, rather than to direct anesthesia of the cochlear nerve. Later, an independent effect of the drug may occur on neural tissues in the inner ear.

Effects of lidocaine on salicylate-induced discharge of neurons in the inferior colliculus of the guinea pig

Using the extracellular recording method, the effects of lidocaine (a local anesthetic known to relieve tinnitus) on discharge of inferior colliculus (IC) neurons of the guinea pig were studied before and after salicylate (200 mg/kg) administration. The salicylate-induced discharge was inhibited by intravenous injection of lidocaine at a concentration (1 mg/kg) clinically used for treating tinnitus. IC neurons could be classified into two groups according to the difference in sensitivity to lidocaine: (1) weakly-sensitive neurons and (2) highly-sensitive neurons. In weakly-sensitive neurons, the duration of the lidocaine effect lasted for less than 5 min, and the inhibitory action on the discharge of neurons was greater when the latency to sound stimulus became longer. In highly-sensitive neurons, on the other hand, the activity of neurons was almost completely inhibited for longer than 30 min, irrespective of the latency to sound stimulus. The clinical relevance of these types of neurons is discussed.

Effects of local anaesthetics on the gross receptor potentials in the guinea pig cochlea

Local anaesthetics have been used intravenously and intratympanally to reduce tinnitus. In order to clarify its action in the periphery, we applied 0.5 mM tetracaine in the scala tympani in 18 cochleae and studied the effects on the receptor potentials. We used a temporal bone preparation of the guinea pig ear in vitro exposing the fourth cochlear turn where the cochlear microphonics (CM) and the summating potential (SP) were recorded. The perfusion was kept at a rate of 50 microliters/min. The frequency response of the cochlea was determined at the beginning of each experiment and the responses were recorded at the best frequency of the preparation. In another five cochleae an accumulated dose-response relationship was determined by increasing the tetracaine concentration in steps (50, 100, 300, 500, 1000 and 2000 microM), measuring the difference in amplitude of the receptor potentials. The CM decreased significantly (p < 0.001; mean 0.37 mV; SD 0.29). In 12 cochleae the SP was initially positive and did not increase significantly (p = 0.16; mean 0.07 mV; SD 0.16). In six cochleae the SP was initially negative and all changed polarity to positive and increased significantly (p < 0.05; mean 0.36 mV; SD 0.28). The effects on both the CM and the SP were reversible. Owing to the inter-individual variation between the cochleae the SP/CM ratio was determined and it increased significantly (p < 0.001; mean 0.18; SD 0.11). In the accumulated dose-response experiments the CM decreased significantly (p < 0.05) in a dose-dependent way, whereas the SP did not increase significantly. The SP/CM ratio increased significantly (p < 0.05) at 300 microM and 500 microM. We hypothesize that the peripheral tinnitus-reducing action of local anaesthetics is in part due to a reversal of the SP, but also to a reduction of the CM. The difference in effect of tetracaine on the receptor potentials, the CM and the SP, suggests that the SP is not dependent on the CM.

Effects of intratympanically delivered lidocaine on the auditory system in humans

Since lidocaine is used to relieve the symptoms of Meniere's disease and tinnitus, its effects on the human cochlea is of specific interest. In experimental animals, topically administered lidocaine affects cochlear electrophysiology in a specific, dose-dependent manner. In the current study, lidocaine (40 mg in 1 ml of saline) was delivered intratympanically in six patients with essentially normal hearing in an attempt to alleviate tinnitus. Auditory function was assessed by pure tone audiometry, auditory evoked brain stem responses (ABR), and transiently evoked otoacoustic emissions (TEOAE) to observe possible drug effect in the auditory system. In five patients, saline was injected prior to lidocaine for control purposes. Saline injection did not create significant changes in any of the measures. After a 2 hr follow-up period, intratympanic injection of lidocaine caused a 2 to 10 dB reduction in TEOAE level at 1 to 3 kHz frequencies. This reduction was at its maximum at the 30 min post-injection sampling point, and was followed by a slow recovery. At 2 hr post-injection, TEOAE amplitude was still 2 to 4 dB below baseline level. Pure tone thresholds were slightly affected 30 min after intratympanic lidocaine injection, but were fully recovered 1 hr after the injection. Lidocaine injection did not cause any changes in ABR latencies or amplitudes in any of the patients. These results suggest that the dose of intratympanically administered lidocaine used here has a specific effect on the organ of Corti structures in human subjects, without significantly affecting the auditory nerve or central auditory pathways. The relationship of the drug effect in conjunction with a possible effect on inner ear disorder might help to localize the site of disorder.

Retest stability of the tinnitus handicap questionnaire

The test-retest stability of the Tinnitus Handicap Questionnaire was assessed for a sample of 32 tinnitus patients. The questionnaire is a self-report measure that quantifies the physical, emotional, and social consequences of tinnitus (factor 1), the interfering effects of tinnitus on the hearing ability of the patient (factor 2), and the patients' view of tinnitus (factor 3). Retest stability estimates were obtained in order to determine the applicability of using the questionnaire as an outcome measure following tinnitus management. High test-retest correlations emerged for factors 1 and 2, whereas factor 3 yielded inadequate retest reliability. Therefore, it is recommended that only factors 1 and 2 be used for documenting changes in self-perceived tinnitus handicap following medical, surgical, or rehabilitative intervention.

Effect of lidocaine injection of EOAE in patients with tinnitus

In the present study, evoked otoacoustic emissions (EOAEs) were measured in 30 patients with tinnitus before and after intravenous lidocaine injection (1 mg/kg). For EOAE recordings, 1 kHz tone burst stimuli were used. Intravenous lidocaine injection resulted in suppression of tinnitus in 22 (73%) ears, and changes of EOAE amplitude (increase or decrease) in 18 (60%) ears. Of the 18 ears with EOAE amplitude changes, tinnitus disappeared or decreased in 17 (94%) ears. In 12 ears without changes of EOAE amplitude, tinnitus was suppressed in only 5 (42%). Changes in latency were not detected in any of the ears. These results indicate that there is a relationship between the effect of lidocaine in tinnitus suppression and changes in cochlear micromechanics caused by lidocaine.

Changes in auditory evoked responses during intravenous lidocaine

Auditory evoked responses in 21 cases with tinnitus were recorded before and after the administration of intravenous lidocaine. A dosage of 1 mg/kg body weight was diluted with 20% glucose (20 ml) and administered intravenously over a one-min period. The loudness of tinnitus was evaluated during electrocochleography (ECochG) or auditory brain-stem response (ABR) recordings using a score between 0 and 11. The stimulus sound was a tone burst in a frequency that corresponded to the pitch of tinnitus. AP latency on ECochG and the inter peak latency (IPL) of wave I-III and wave III-V on ABR were prolonged momentarily and tinnitus was reduced. These findings reveal that the sites of action for lidocaine are both the inner ear and the brain-stem.

A possible masking effect of tinnitus. Evaluation of CNV audiometry

To determine whether tinnitus has a masking effect similar to that of general external sounds, the hearing threshold shift when the tinnitus was changed by intravenous administration of lidocaine was measured by contingent negative variation (CNV) audiometry. In a preliminary study, the reliability of CNV audiometry was evaluated in 12 patients with tinnitus. The reproducibility of CNV audiometry was confirmed, based on repeated measurements of CNV audiometry at the tinnitus frequency. The threshold difference between CNV audiometry and pure tone audiometry was -0.76 +/- 1.35 dB, and a high statistical correlation between the threshold of CNV audiometry and pure tone audiometry was evident. The CNV threshold shift at tinnitus frequency after lidocaine injection was measured in 89 ears. In the tinnitus-decreased group, the CNV threshold decreased (4-6 dB) in 22% of cases; however, in the tinnitus-unchanged group, the CNV threshold was little changed. These findings suggest that tinnitus may have a masking effect as is the case with external sounds.

Experimental basis for lidocaine therapy in cochlear disorders

In order to further our basic understanding of the effects of lidocaine hydrochloride in the inner ear, cochlear potentials and blood flow (CBF) were assessed after intravenous (i.v.), anterior inferior cerebellar artery (AICA), and local round window (RW) lidocaine administrations in guinea pigs and rats. Lidocaine RW applications produced a dose dependent decrease in compound action potentials (CAP) and cochlear microphonics (CM). The sensitivity changes were more pronounced at high frequencies. These findings suggest that lidocaine has specific pharmacological action in the inner ear other than simple anesthesia of the auditory nerve. The basal turn endocochlear potentials (EP) were not altered by topical lidocaine, implicating altered organ of Corti function following local application of lidocaine. RW applications of lidocaine had no effect on CBF or systemic blood pressure (BP). I.v. infusions caused substantial reductions in BP. In the case of systemic infusions the percent changes in CBF were equal to and accountable by the BP changes. The microinfusions (50 mg/ml, 100 nl/min) through AICA produced a 30%, long lasting increase in CBF. However, neither systemic lidocaine nor AICA infusions had an effect on CAP or CM. These findings indicate that systemically given lidocaine may not cross the blood-cochlear barrier and that the cochlear electrophysiological effects due to lidocaine when given locally are partly mediated by direct influence on cochlear hair cell function; they also suggest that lidocaine-induced interference with active ion transport in the lateral wall or an influence on CBF are not contributing factors.

A survey of tinnitus management in National Health Service hospitals

This paper reports the results of a postal questionnaire survey to ascertain the current status of NHS hospital services for patients with tinnitus. Statistics are given on the various managements used, e.g. about two-thirds of consultants prescribe tinnitus maskers. A total of 66 tinnitus clinics have been identified. The data are interpreted as illustrative of the steady improvements in the last 10-15 years in tinnitus management services.

Intra-tympanic injections in the treatment of tinnitus

Prolonged reduction or abolition of tinnitus has been reported in about two-thirds of patients treated with a single or weekly-repeated injection through the tympanic membrane of either dexamethasone or lignocaine. In a small-scale trial of these treatments, dexamethasone gave 6 patients little benefit but few side-effects. Lignocaine gave 5 patients no lasting benefit but violent vertigo for several hours. A. Axelsson (personal communication) had similar experience with 6 patients treated with intra-tympanic lignocaine. It is concluded that this form of treatment does not seem sufficiently effective to offset its low acceptability.

Systemic lidocaine silences ectopic neuroma and DRG discharge without blocking nerve conduction

Systemic application of lidocaine in rats suppressed ectopic impulse discharge generated both at sites of experimental nerve injury and in axotomized dorsal root ganglion (DRG) cells. ED50 for DRGs was significantly lower than for the injury site. Lidocaine doses effective at blocking ectopic discharge failed to block the initiation or propagation of impulses by electrical stimulation, and only minimally affected normal sensory receptors. This selectivity may account for the effectiveness of systemic local anesthetics and other drugs that share the same mechanism of action (notably certain anticonvulsants and antiarrhythmics), in the management of neuropathic paresthesias and pain. In addition, it may account for the prolonged analgesia sometimes obtained using regional local anesthetic block.

Acupuncture for tinnitus management

Fifty-six patients with continuous and severe tinnitus as their major complaint were treated with traditional Chinese acupuncture. After a pre-treatment period with baseline evaluation of tinnitus, 10 treatments were given during a period of 20 days, followed by a post-treatment period in order to obtain indications of prolonged treatment effects. Assessments were made using visual analogue scales (VAS) and a verbal retrospective rating scale. Three patients reported improvement which lasted for at least 10 days after the last treatment, indicating a possible long-term effect in some cases. Twenty-one percent of the patients reported transient intensity reductions lasting for hours/days. Estimated 'substantial' improvement rate by VAS, consistent for all three parameters involved (intensity, annoyance, awareness), was 20%, while the corresponding deterioration rate was 25%. Statistical analysis of the whole group did not show any significant general treatment effects. Interactions between treatment evaluations by verbal rating and VAS are discussed as well as interactions with psychological components.

Tinnitus

Tinnitus, a common complaint, reportedly affects more than 37 million Americans. Most often, it is associated with a sensorineural hearing loss in the high-frequency range. Tinnitus, however, is a symptom and not a disease. Complacency about this symptom complex may cause physicians to overlook a severe underlying pathologic process. Patients with unilateral tinnitus, pulsatile tinnitus, fluctuating tinnitus, or tinnitus associated with vertigo should undergo thorough assessment, including elicitation of a complete history, physical examination, and audiologic analysis. In many instances, treatment is effective. Masking of tinnitus, medical therapy, and biofeedback and counseling are some measures that have been used in the management of tinnitus.

Trial of flecainide acetate in the management of tinnitus

A two-phase trial of flecainide acetate in the management of tinnitus has been carried out in 22 patients with severe long-term tinnitus resistant to other treatments. Although 5 (23%) patients reported some limited benefit the results are not conclusive but suggest that, for such patients, flecainide deserves a place as a drug worth considering as a last resort, with the prospect of it occasionally giving a worthwhile degree of relief.

Evaluation of amino-oxyacetic acid as a palliative in tinnitus

Amino-oxyacetic acid (AOAA) was evaluated as a palliative in tinnitus. Sixty-six patients with tinnitus presumed to be of cochlear origin were given either a placebo or 75 mg of AOAA four times a day for 1 week. Response was evaluated by both audiometric measurement of tinnitus loudness and subjective rating by patients of change or no change in tinnitus severity. Because loudness measurements and self-rating have not been shown to be independent, and since the aim of clinical treatment of tinnitus is the alleviation of subjective distress, greater weight was given to the patient's self-rating. A total of 21% of all patients reported a subjective decrease in tinnitus severity, usually within 3 to 4 days after the start of AOAA use. Patients with tinnitus caused by presbycusis or Meniere's disease were the most likely to respond to AOAA treatment with a reduction in tinnitus severity, whereas those with drug-induced tinnitus were the least likely to respond. Nausea and dysequilibrium were the most common side effects of AOAA use. Of the 21% of patients who responded to AOAA, 71% developed some type of side effect. Amino-oxyacetic acid produces a reduction in the severity of tinnitus in about 20% of patients; however, the incidence of side effects makes the drug unacceptable for clinical use.

Vestibular effects of intravenous lidocaine used in the treatment of tinnitus

Intravenous lidocaine is known to have an effect on the auditory system in that it is useful for suppressing tinnitus, albeit temporarily. We have used intravenously administered lidocaine as one of the treatment modalities for refractory, disturbing, tinnitus. Its effects on the vestibulo-ocular system were determined by electronystagmography performed before and immediately after injecting lidocaine: smooth pendular stimulus tracking was unaffected; spontaneous and positional nystagmus tended to be suppressed; directional preponderance was reduced or reversed; and the difference between the nystagmus responses in the two directions during the pendular rotation chair test was also reduced or reversed. These changes in the caloric and rotation tests were statistically significant. Lidocaine also appeared to have altered the balance between the two sides in the vestibulo-spinal system as indicated by the results of the stepping test during craniocorpography. The results lend support to the hypothesis that intravenous lidocaine acts at the level of the central nervous system rather than at the periphery.

Electrocochleographic findings and the effects of lidocaine on tinnitus in non-hearing ears

In the preceeding report (Jackson, 1985) the author produced evidence which brought into question the widely held view that, in abolishing tinnitus, lidocaine was acting 'centrally'. This present investigation is another approach to attempt to narrow the site of action of lidocaine in abolishing tinnitus. During a four-year period, patients suffering from strictly unilateral tinnitus which was referred to, and therefore apparently arising from, an ipsilateral 'dead' ear, underwent electrocochleography. Additionally, the subjective effect on the tinnitus of a bolus injection of lidocaine was recorded. Nine patients were available for this study, which appears to show a correlation of the results of the electrocochleogram and the effects of the lidocaine injection, although the numbers are small.