Repetitive Transcranial Magnetic Stimulation for Tinnitus: An Evolving Therapy
Repetitive Transcranial Magnetic Stimulation for Tinnitus: An Evolving Therapy
Abstract & Commentary
By Douglas Labar, MD, PhD, Director of the Comprehensive Epilepsy Center, Professor of Neurology and Neuroscience, Weill Cornell Medical College; Attending Neurologist, NewYork-Presbyterian Hospital. Dr. Labar reports no financial relationship relevant to this field of study.
Synopsis: Transcranial magnetic stimulation of the brain may be a promising new therapy for the treatment of chronic tinnitus.
Source: Khedr E, et al. Contralateral versus ipsilateral rTMS of temporoparietal cortex for the treatment of chronic unilateral tinnitus: Comparative study. European J Neuro 2010; DOI 10.1111/j.1468-1331.2010.02967.x. (Published online 3/3/10.)
Chronic tinnitus may be disabling, and always is difficult to treat. In some patients, this symptom may be analogous to phantom limb pain, in that hearing loss produces functional de-afferentation of auditory cortex and leads to excess cortical excitation. Focal repetitive transcranial magnetic stimulation (rTMS) of cerebral auditory areas may disrupt abnormal neuronal excitatory circuitry and reduce tinnitus symptoms.
Which side of the brain should receive magnetic stimulation? Increased left-side cortical activity has been shown in one study, employing positron emission tomography in tinnitus cases.1 On the other hand, functional MRI revealed greater reactivity to auditory stimuli in the hemisphere ipsilateral to lateralized tinnitus symptoms.2 This suggests that the hemisphere contralateral to the tinnitus is abnormally active at baseline, and less reactive to exogenous stimuli. Khedr and colleagues set out to study whether contralateral or ipsilateral rTMS of temporoparietal cortex provided superior relief of unilateral tinnitus.3
Sixty-two patients affected with unilateral tinnitus for up to 10 years were treated with two consecutive five-day courses of rTMS. They were randomized to receive treatment on the side of the brain ipsilateral or contralateral to their symptoms. The patients were unaware that laterality of the therapy was under investigation, and neurologist investigators were blinded as to the patients' treatment groups. Patients were assessed with the tinnitus handicap inventory (THI) and the Hamilton ratings of depression and anxiety prior to the 10 days of treatment, after treatment, and monthly for the next 10 months.
There was an immediate significant reduction in the THIs seen in the first assessments at the end of the 10-treatment therapy period. This occurred only with stimulation contralateral to the unilateral tinnitus. Contralateral stimulation was superior to left-side stimulation, and there was no difference between left- and right-side stimulation. Depression and anxiety severity scores, which correlated with THI severity at baseline, improved correspondingly.
Remarkably, after only 10 treatment sessions over two weeks, the clinical improvement persisted unabated for the next 10 months without further therapy. This contrasts with results of rTMS for seizures, where the antiepileptic effects wear off after two months.4
Commentary
The time course of these rTMS results for tinnitus also can be compared with outcomes of rTMS for treatment-resistant depression, which recently has been cleared by the U.S. Food and Drug Administration for clinical use.5 In a large clinical trial, 53/136 initial responders required additional therapy within 24 weeks.6 A small early study suggested antidepressant effects last less than 14 days.7
Thus, a single course of rTMS of temporopatietal cortex contralateral to chronic unilateral tinnitus symptoms may permanently reorganize underlying abnormal auditory cortex functions. It may not just temporarily suppress the patients' symptoms, as seems to occur in other conditions where rTMS therapy has been tried. Several editorials have suggested rTMS is rapidly approaching being an accepted avenue of care for this illness.8,9
Finally, electrical stimulation of auditory cortex via chronic implanted electrodes may be even more efficacious for pure tone tinnitus than rTMS (97% vs. 77% reduction in 12 patients).10 If supported by larger follow-up clinical trials, direct electrical brain stimulation for tinnitus may become an even more effective treatment than rTMS for this sometimes disabling condition.
References
1. Plewnia C, et al. Moderate therapeutic efficacy of positron emission tomography-navigated repetitive transcranial magnetic stimulation for chronic tinnitus: A randomized, controlled pilot study. J Neurol Neurosurg Psychiatry 2007;78:152-156.
2. De Ridder D, et al. Theta, alpha and beta burst transcranial magnetic stimulation: Brain modulation in tinnitus. Int J Med Sci 2007;4:237-241.
3. Khedr E, et al. Contralateral versus ipsilateral rTMS of temporoparietal cortex for the treatment of chronic unilateral tinnitus: Comparative study. European J Neuro 2010; DOI 10.1111/j.1468-1331.2010.02967.x. (Published online 3/3/10.)
4. Fregni F, et al. A randomized clinical trial of repetitive transcranial magnetic stimulation in patients with refractory epilepsy. Ann Neurol 2006; 60:447-455.
6. Janicak P, et al. Transcranial magnetic stimulation in the treatment of major depressive disorder: A comprehensive summary of safety experience from acute exposure, extended exposure, and during reintroduction treatment. J Clin Psychiatry 2008;69:222-232.
7. Pascual-Leone A, et al. Rapid-rate transcranial magnetic stimulation of left dorsolateral prefrontal cortex in drug-resistant depression. Lancet 1996;348:233-237.
8. Dornhoffer J, et al. Transcranial magnetic stimulation and tinnitus: Implications for theory and practice. J Neurol Neurosurg Psychiatry 2007;78:113.
9. De Ridder D. Should rTMS for tinnitus be performed left-sided, ipsilaterally or contralaterally, and is it a treatment or merely investigational? European J Neurol 2010; DOI 10.1111/j.1468-1331.2010.02967.x. (Published online 3/3/10.)
10. De Ridder D, et al. Primary and secondary auditory cortex stimulation for intractable tinnitus. ORL J Otorhinolaryngol Relat Spec 2006;68:48-55.
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