What Is Sensorineural Hearing Loss?
Sensorineural hearing loss is a form of hearing impairment caused by injury to the cochlear hair cells or the auditory nerve, in contrast to conductive hearing loss, which affects the outer or middle ear.
It is the most common form of permanent hearing loss in adults and may have numerous causes, including age-related degeneration, known as presbycusis, exposure to loud noise, ototoxic medication, infections, vascular disorders, autoimmune conditions and genetic factors.
Clinically, it presents as a progressive reduction in hearing acuity, usually affecting the higher frequencies first, difficulty understanding speech in noisy environments, tinnitus and, in some cases, vertigo.
The prognosis depends on the underlying cause. Some forms remain stable, while others progress over time. In cases with a vascular or metabolic basis, interventions aimed at improving cochlear oxygenation may influence the course of the condition.
Characteristics of Sensorineural Hearing Loss
The cochlear hair cells, particularly the outer hair cells that amplify sound before it reaches the inner hair cells, do not regenerate in humans.
Once these cells are lost, the resulting hearing impairment is permanent. Treatment must therefore focus on preserving cells that remain at the limits of viability—those that have not yet undergone irreversible injury but are functioning inadequately because of ischaemia or metabolic stress.
In vascular forms of sensorineural hearing loss affecting patients with atherosclerosis, diabetes, hypertension or microangiopathy, chronic cochlear hypoxia is the predominant pathological mechanism.
In these cases, improving oxygen delivery may slow the progression of hearing loss or restore part of the impaired function.
Scientific Literature on the Use of Hyperbaric Oxygen Therapy in Sensorineural Hearing Loss
The literature on the use of hyperbaric oxygen therapy in sensorineural hearing loss of vascular or metabolic origin has produced encouraging findings, particularly in patients with a subacute course whose hearing loss has not yet become fully established.
Studies have reported improvements in audiometric findings, mainly at middle and high frequencies, as well as subjective improvements in speech comprehension.
The principal mechanism is the direct increase in cochlear oxygenation through the dissolution of oxygen in the endolymph and perilymph, thereby overcoming the vascular insufficiency associated with these forms of hearing loss.
The simultaneous activation of antioxidant mechanisms also protects cochlear hair cells from the oxidative stress caused by chronic ischaemia.
The Role of Hyperbaric Oxygen Therapy
In sensorineural hearing loss, hyperbaric oxygen therapy may be used as an adjunctive option, primarily in cases with a vascular or metabolic basis, in patients with a subacute presentation or in those who have not responded fully to conventional treatment.
It is not a treatment for age-related hearing loss or hereditary forms of the condition.
Improved oxygenation within the fluid compartments of the cochlea provides affected hair cells with the energy required to function more effectively or, in some cases, to recover from a state of functional suppression caused by chronic ischaemia.
The neovascularisation stimulated over the longer term may also improve cochlear blood flow.
A typical treatment course consists of 15 to 30 sessions, planned in collaboration with the otorhinolaryngologist and monitored through audiometric assessment.