[Treatment of tinnitus with lidocaine? A report of clinical experiences]

The effect of lidocaine iontophoresis for the treatment of tinnitus: a systematic review

PURPOSE

Tinnitus is a common symptom with multiple causes and treatment options. Previous studies have investigated the effect of lidocaine iontophoresis. The aim of this review is to systematically present the effects on tinnitus and to derive possible effects.

METHODS

In accordance to the PRISMA statement, the search and analysis were performed. An abstract in German or English and a performed intervention with lidocaine iontophoresis for the treatment of tinnitus, independent of the study design, were considered as inclusion criteria. Due to the heterogeneity of the studies, only a narrative synthesis was performed.

RESULTS

The search yielded 179 studies of which 170 were excluded. Six full-texts and three abstracts were included. In total, 957 patients were treated with lidocaine iontophoresis. The percent improvement in symptoms after lidocaine iontophoresis ranged from 4% to 62%. The qualitative assessment of the studies resulted in an overall "weak" rating for all of them.

CONCLUSIONS

Due to the heterogeneity and the limited quality of the studies found, no clear statement can be made about the efficacy. The number of those who benefited from therapy varied widely. In addition, it cannot be ruled out that the effect was merely due to electrical stimulation of the cochlea.

Results and Quality of Life after Implantation of Active Middle Ear Implants

The provision of implantable hearing aids represents an area with high development and innovation potential. On the one hand, this review article provides an overview of current indication criteria for the treatment with active middle ear implants. On the other hand, outcome parameters as well as functional results after implantation of active middle ear implants are demonstrated and discussed. The focus is mainly placed on audiological results as well as the subjective health status. "Patient Reported Outcome Measures" (PROMs) have become an integral part of the evaluation of hearing implant treatment. Due to low evidence level criteria, the study situation regarding audiological as well as subjective outcome parameters is not satisfactory. The lack of an international consensus on accepted outcome parameters makes a meta-analytical analysis of results immensely difficult. In the studies published to date, patients with sensorineural hearing loss and patients with conductive or mixed hearing loss offered better speech recognition after implantation of an active middle ear implant compared to conventional hearing aids. Current analyses show a significant improvement in general as well as hearing-specific quality of life after implantation of an active middle ear implant. To date, no validated, hearing-specific quality-of-life measurement instruments exist for assessing the success of fitting in children. Especially in children with complex malformations of the outer ear and the middle ear, excellent audiological results were shown. However, these results need to be substantiated by quality-of-life measurements in future.

[State of the art of quality-of-life measurement in patients with chronic otitis media and conductive hearing loss]

The evaluation of results after middle ear reconstruction has been mainly based on functional parameters. In clinical practice as well as in otological research, the pure tone audiogram represents the gold standard in the assessment of the postoperative outcome. In order to assess the patient's subjective outcome, outcome analyzes focus increasingly on the health-related quality of life (HRQOL). However, the evaluation of HRQOL requires reliable and validated measuring instruments. A modest number of validated questionnaires for determination of the disease-specific HRQOL in patients with chronic otitis media and/or conductive hearing loss are currently available. Three of seven available questionnaires were developed and validated in the German-speaking countries, the Zurich Chronic Middle Ear Inventory 21 (ZCMEI-21), the Chronic Otitis Media Outcome Test 15 (COMOT-15) and the Stapesplasty Outcome Test 25 (SPOT-25). In this review, all seven available disease-specific measuring instruments as well as the generic questionnaires, which were used in previous clinical trials, are explained and current findings of quality-of-life research in patients with chronic otitis media and/or conductive hearing loss are presented.

Sensorineural Tinnitus: Its Pathology and Probable Therapies

Tinnitus is not a single disease but a group of different diseases with different pathologies and therefore different treatments. Regarding tinnitus as a single disease is hampering progress in understanding of the pathophysiology of tinnitus and perhaps, more importantly, it is a serious obstacle in development of effective treatments for tinnitus. Subjective tinnitus is a phantom sound that takes many different forms and has similarities with chronic neuropathic pain. The pathology may be in the cochlea, in the auditory nerve, or, most commonly, in the brain. Like chronic neuropathic pain tinnitus is not life threatening but influences many normal functions such as sleep and the ability to concentrate on work. Some forms of chronic tinnitus have two components, a (phantom) sound and a component that may best be described as suffering or distress. The pathology of these two components may be different and the treatment that is most effective may be different for these two components. The most common form of treatment of tinnitus is pharmacological agents and behavioral treatment combined with sound therapy. Less common treatments are hypnosis and acupuncture. Various forms of neuromodulation are becoming in use in an attempt to reverse maladaptive plastic changes in the brain.

Human Brain Imaging of Tinnitus and Animal Models

Because subjective tinnitus is typically localized to the ear with hearing loss, tinnitus was traditionally thought to originate from neural hyperactivity in the damaged ear. However, most studies have found that hearing loss reduces the neural outputs from the damaged cochlea. These negative findings led to the hypothesis that rinnitus arises from aberrant neural activity in the central auditory system. Positron emission tomography imaging studies performed on tinnitus patients that could modulate their tinnitus provide evidence showing that the aberrant neural activity that gives rise to tinnitus resides in the central auditory pathway. To investigate the biological basis of tinnitus in more detail, an animal model was developed that allowed behavioral measures of tinnitus to be obtained from individual rats after inducing tinnitus with high doses of salicylate or high-intensity noise. This behavioral model was used to test the efficacy of memantine, an N-methyl-D-aspartate antagonist, and scopolamine, an anticholinergic, in suppressing salicylate-induced tinnitus. Neither drug completely suppressed salicylate-induced tinnitus. To detect the physiological changes associated with tinnitus, chronic microwire electrodes were implanted in the auditory cortex and measurements were obtained from the auditory cortex before and after salicylate and noise exposures known to induce tinnitus. High doses of salicylate or high-level noise exposure generally resulted in sound-evoked hyperactivity in the electrophysiological responses recorded from the auditory cortex of awake-animals. However, anesthetic tended to suppress or abolish the hyperactivity.

Effects of salicylate on voltage-gated sodium channels in rat inferior colliculus neurons

To investigate the effects of the tinnitus inducer, sodium salicylate, on voltage-gated sodium channels, we studied freshly dissociated inferior colliculus neurons of rats by the whole-cell voltage clamp method. Salicylate blocked sodium channels in concentration-dependent manner (0.1-10 mM), and the IC50 value of salicylate was estimated to be 1.43 mM after application. The sodium conductance-voltage curve did not shift along the voltage axis with salicylate application. In contrast, the steady-state sodium channel inactivation curve was shifted by about 9 mV in the hyperpolarizing direction. In addition, salicylate delayed the sodium channel recovery from inactivation by increasing the slow time constant. It was concluded that salicylate bound to the resting and inactivated sodium channels to cause blocking, with a higher affinity for the latter state. Our results suggest that salicylate causes a concentration-dependent blockade of voltage-gated sodium channels and shifts the inactivation curve to more hyperpolarized potentials, which could be related to the mechanism of salicylate-induced tinnitus.

Tinnitus

Tinnitus is a common otologic symptom secondary to numerous etiologies, such as noise exposure, otitis, Meniere's disease, otosclerosis, trauma, medications, and presbycusis. A thorough evaluation is necessary to rule out less common causes, which may include acoustic neuromas, glomus tumors, atherosclerosis of the carotid arteries, arteriovenous fistulae (AVFs), arteriovenous fistulae malformations (AVMs), and intracranial hypertension. Treating physicians need to have a very compassionate attitude towards these patients, and statements such as "there is nothing that can be done" are very inappropriate and should be strongly condemned. Reassurance, hearing aids, masking devices, retraining methods, antidepressants, intratympanic medications, and management of underlying pathologies such as carotid artery atherosclerosis, skull base tumors, intracranial hypertension, and AVMs/AVFs provide relief for the majority of these patients.

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.

Recent advances in the pharmacological treatment of tinnitus

Tinnitus is an extremely prevalent condition that impinges on the lives of sufferers to varying degrees. In some people, it is a fairly minor irritation but, for many, the tinnitus intrudes to such a degree that it affects their ability to lead a normal life, and in some very extreme cases has resulted in suicide. Insomnia, inability to concentrate and depression are commonly reported to accompany the condition. Relief can be reliably obtained using intravenous lignocaine, which indicates that pharmacology can provide a route for effective alleviation of the condition. In this article, Julie Simpson and Ewart Davies review the potential pharmacological therapies, and emphasize that clinical research has been hampered by the absence of a reliable objective assessment of the tinnitus and by the variable nature of the complaint.