Electrical stimulation can be used to treat tinnitus. In general, there are attempts to stimulate the ear itself, and attempts to modulate tinnitus through stimulation of muscles in the head or neck (generally termed "TENS").
Siedman and Jacobson (1996) indicated in a non-peer reviewed journal that ES is a possible treatment modality for patients with severe tinnitus. Hatton et at (1960) reported that only anodal (positive electrode) stimulation produced the suppressive effect. ES is provided through electrodes in the vicinity of the ear. The exact mechanism(s) by which ES suppresses/reduces tinnitus may be that positive electrical current produces hyperpolarization of nerve fibers, which inhibits and reduces spontaneous discharge rates (Portmann et at, 1983). As most tinnitus is thought to be central in origin, acceptance of this mechanism is contrary to general dogma.
Hatton et al (1960) observed that the intensity of tinnitus was reduced in 15 (45.5 %) of 33 patients with ES. Chouard et al (1981) reported that 30 (47 %) of 64 patients achieved success (as determined by reduced intensity that lasted for a few days to more than 1 week) following electrotherapy. None of the 12 patients who received placebo stimulation attained relief. The authors stated that if a patient failed to achieve improvement after 2: to 3 sessions, it is unlikely that this form of therapy will be successful. It would seem to us that reduction of tinnitus for periods greater than a few seconds after discontinuation of stimulation, while certainly desirable, would be very difficult to explain with known neurophysiology.
Engejberg and Bauer (1985) performed two experiments to examine the effects of transcutaneous electrical stimulation (TENS) on tinnitus. Experiment 1 had 10 subjects (18 ears) and improvement (defined as either a complete remission or a decrease in the frequency of tinnitus) was seen in 6 of them with tinnitus being eliminated in 3 ears. Experiment 2 employed a single-blind study design with 20 patients (experimental group, n =10, 17 ears; control group, n = 10, 15 ears). It was found that 9 of 10 patients with 15 (88.2 %) of 17 ears reported improvement following stimulation. These changes lasted from 20 minutes to at least 6 months. On the other hand, only 1 patient (1 ear) in the control group improved (a 13 % decrease in frequency of tinnitus).
A systematic review (n=69 RCTs) by Dobie (1999) reported that based on the results of two RCTs, TENS was found to be ineffective for the treatment of tinnitus compared to an inactive device. However, there have been newer ones.
Steenerson and Cronin (1996) reported their findings at a tinnitus conference (i.e. not a peer reviewed journal) of 246 patients with severe tinnitus of various etiologies treated with ES (a total of 6 to 10 sessions). One hundred and thirty patents (53 %) reported significant benefit (an improvement of at least 2 points in a 1 to 10 subjective rating scale) with 32 patients (13 %) having complete suppression of their tinnitus. At 3-month follow-up, 72 % had continuous benefit.
Herraiz et al (2007) found in 26 patients with the probable diagnosis of somatic tinnitus that TENS could improve the tinnitus in 46% of the participants. Patients used TENS at home for 2h, once per day during 2 weeks (alternating ramped burst, 150 pps, with pulse duration of 100 micro sec, amplitude 0-60 mA; average TENS intensity was 27 mA). Intermittent "typewriter" type of tinnitus was the most responsive.
Kapkin et al. (2008) conducted an RCT of 42 patients with subjective tinnitus who received TENS (n=31), or placebo (n=11). The comparison between the average sensation level of tinnitus before and after treatment in the electrical stimulation group was not statistically significant (p=0.424). A similar comparison for the placebo group was also not statistically significant (p=0.683). The rate of improvement following the therapy was 42.8% (18/42) in the electrical therapy group and 28.5% (4/14) in the placebo group.
Vanneste et al. (2010), in a case series (n=240), applied a real and a sham TENS treatment to patients with tinnitus. The stimulation was applied to the C2 nerve root area, and thus this study is of limited use in evaluating TENS in a general sense. Only 17.9% of the patients responded to treatment with TENS by demonstrating significant tinnitus suppression (p<0.001).
Mielczarek and Olszewski (2013) reported the effects of "direct current stimulation" (rectangular, positive polarization) in 119 patients, there was reduction in tinnitus with current frequencies similar to tinnitus frequency. It seems to us that any stimulus delivered at the same frequency as the tinnitus cannot actually be direct current (DC). We are also puzzled why applying high frequency electrical pulses to the ear should be effective, or different than true DC. Perhaps it is not as painful though. It would seem difficult to provide a true placebo control, with a protocol that involves delivering small electrical shocks. We would be more convinced if the placebo arm was equally painful -- perhaps negative polarization rather than positive, or higher voltage with far lower current Overall, we are not convinced.
Overall, these papers report generally positive results of ES or TENS for tinnitus. We find it hard to understand how this treatment could cause lasting effects. Whether these are placebo effects or organic, they seem worth pursuing.