Classically, an Idiopathic Sudden Sensorineural Hearing Loss (ISSHl), is defined as a hearing loss of 30 dB or more that occurs within three days and over at least three frequencies. One common clinical presentation is sudden unilateral hearing loss.
The symptoms can be subtle enough, such as "fullness/block", that both patient and clinician often overlook until a severe hearing loss occurs. In the United States, there are approximately 0 to 20 cases per 100,000 people. This is approximately 4,000 new cases per year in the United States. The incidence of the disease may be higher as some cases go unreported. It has been suggested that up to 65% of cases can be resolved spontaneously, but this has been questioned recently.
It is not clear what causes ISSHl. Many pathophysiological mechanisms can lead to ISSHl, including vascular occlusions, viral infections, labyrinthine skin breaks, immune-associated disease, abnormal cochlear response, trauma, abnormal tissue and growth, toxins, toxic drugs, and cochlear membrane injury.
A hearing loss can cause severe social and economic problems for both the individual and the community. Patients with hearing loss in the mild range (26dB40dB) can hear and repeat words at 1 meter. They may not need therapy. Hearing aids are recommended for moderate hearing loss (41 dB-60 or severe (61dB-80) and lip-reading and signing when necessary.
Hyperbaric oxygen therapy is shown to improve hearing in severe hearing loss patients and 19.3 dB in moderate hearing impairment sufferers. This can bring the impairment back to the normal range and improve the quality of life.
There is less evidence to support the use of HBo2 for chronic hearing loss than there is for acute ISSHl. There is evidence that it might be beneficial. Patients who have suffered from hearing loss for more than three months are less likely to benefit.
Schumann and his coworkers examined 557 patients suffering from chronic hearing loss and administered 10 sessions of HBo2 to them. They found a significant improvement in their hearing in 27.8%. In 1997, Kau et al. Kau et al. analyzed 359 patients suffering from refractory hearing loss. Patients with hearing loss that lasted more than one month, but less than three months, showed a noticeable improvement or complete recovery in 13% (20dB in at minimum three frequencies); 25% showed improvement of 10 to 20%. HBO2 had a markedly lower benefit for patients with hearing loss that lasted more than three months. While 30% experienced a decrease of more than 10 dB overall, only 2% had a normal hearing function. Lamm et. al. found similar results.
HBO2's efficacy in treating chronic hearing loss is promising for patients who have not had success with other treatments. It is still recommended that it be used routinely, but more controlled, randomized studies are needed.
It has been thoroughly studied how HBo2 can be used in conjunction with other medical and procedural therapies. Vitamins, corticosteroids (reduction in edema, inflammation), vasodilatory drugs (vasoactive agents or stellate-ganglion blocks), and antiviral agents (herpes virus may be a causative factor for a subset ISSHl), as well as agents that lower hematocrit (volume expanders and normovolemic haemodilution), antibiotics and diuretics, osmotic and anticoagulants, and carbogen
One of the earliest studies compared medical treatment, stellate ganglion blocks (SGB), and HBo2. Research showed that 100% of patients treated with HBo2 and SGB achieved > 10 dB PTA improvements. These patients also recovered hearing to within 20 decibels of their normal levels.
Numerous studies were conducted by the French to evaluate the efficacy of HBo2 when combined with other medical treatments. Both studies showed that HBo2 is a valuable adjunct to other medical therapies and that twice-daily sessions reduce the treatment time.
Aslan and his co-workers published a study on patients who received medical therapy with either SGB, HBo2, or both. The addition of HBo2 led to a significant increase in hearing gains. Racic et al. Comparing HBo2 to pentoxifylline injections. The HBo2 group had statistically significant improvements in overall hearing, physiological hearing values, and moderate hearing gains.
Nabozny, along with colleagues, reviewed two historical ISSHl patient groups treated with a combination of medical therapy and corticosteroids. The HBo2 group had statistically superior hearing gains over all frequencies, and in four frequency ranges for relative and absolute values. Combining high-dose corticosteroids with HBo2 led to statistically better clinical outcomes. Poor clinical outcomes were predicted by delays in treatment and lat hearing impairment. Nabozny and colleagues also did linear regression analyses to determine prognostic factors for hearing improvement. This was done using objective change in gain, PTA, and high-tone average, as well as pure middle-tone and pure mid-tone average. Two favorable factors were identified for ISSHL by Narozny and co-workers: early treatment (within 10 days) and high-dose corticosteroids/HBo2. The following factors were associated with poor prognosis: delayed treatment, labyrinth-responsiveness disorders, and lower TSH levels.
Fujimura et al. Their work was reported by Fujimura et al. Statistics showed that the HBo2 group had a higher rate of recovery. A subset analysis of people with severe hearing loss (>80 dB), showed that the HBo2 groups had a statistically superior rate for hearing improvement.
Dundar et al. Prospectively, patients receiving HBo2 and medical therapy were compared. Statistics showed that the HBo2 group saw statistically significant hearing gains at all frequencies.
Suzuki and his colleagues analyzed 196 ISSHl patients consecutively, comparing IV PGE1 with HBo2. There were no differences noted, implying that PGE1 and corticosteroid therapy are equally effective when combined with HBo2 therapy and that PGE1 is a potential alternative in the corticosteroid-intolerant patient (diabetes, peptic ulcer disease, or viral hepatitis).
Suzuki and his coworkers also compared patients who received IV PGE1 or SGB with HBo2. The results were identical for patients with less severe hearing loss (80 dB). For those with hearing loss greater than 80 dB, however, the hearing rate in patients who received SGB or HBo2 was statistically superior.
Ohno and coworkers reported on patients who received medical therapy or HBo2 treatment. They found that, while the overall mean hearing gain was not significantly different among groups, patients with severe hearing loss experienced significant hearing improvement with HBo2.
Korpinar and his co-workers looked at the treatment of patients who received medical therapy and HBo2 to determine factors that could affect their treatment. These gains were significant for patients with early HBO2; higher HBo2 treatment; use of corticosteroids; low-frequency-ascending and complete audiogram configuration; profound hearing loss. Corticosteroid therapy was the most favorable treatment.
Liu et al. Liu et al. reported on patients who were treated with or without medical therapy within two weeks. Overall, HBo2 was statistically and clinically more effective than medical therapy without it. This difference was most evident for patients with severe or moderate deafness as well as those with audiograms with descending and lat types.
Suzuki and his colleagues also did simple and multiple regression analyses of 174 ISSHl patients who were treated with hydrocortisone or HBo2. They wanted to create a regression model that could predict the hearing outcome for ISSHL patients. There was a significant correlation between hearing improvement rate, days from onset of treatment, patient age, and vertigo.
Alimoglu and his co-workers examined the treatment of patients who received a variety of combinations of IT or oral corticosteroids, and HBo2. Statistics showed that patients who received HBo2 and oral corticosteroids had statistically greater hearing gains and higher proportions of complete recovery.
Holy and his colleagues treated patients with IV vasodilation therapy, and HBo2. Improvement was observed in 59.7%. 65.9% of patients experienced complete or significant recovery if HBo2 treatment was initiated within 10 days. Only 38.9% of patients who received HBo2 within 10 days experienced improvement.
Liu and his co-workers presented their research on patients who were treated with corticosteroids or corticosteroids plus HBo2. In patients with severe hearing loss, the addition of HBo2 was beneficial. However, corticosteroid therapy did not include dextran.
Sources:
https://pubmed.ncbi.nlm.nih.gov/23076907/
https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2704029
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