What Is Cochlear Ischaemia?
Cochlear ischaemia refers to an inadequate blood supply to the cochlea and other structures of the inner ear, resulting in acute or chronic auditory dysfunction.
It is one of the principal pathophysiological mechanisms underlying several otological conditions, including sudden sensorineural hearing loss, Ménière’s disease and ischaemic tinnitus. It represents the common vascular basis of a range of different clinical presentations.
It occurs more frequently in patients with vascular risk factors such as atherosclerosis, diabetes mellitus, hypertension, hyperlipidaemia and smoking.
Symptoms vary according to the severity of the ischaemia, ranging from mild muffling of hearing and tinnitus to sudden severe hearing loss, vertigo and a sensation of fullness in the ear. In chronic cases, ischaemia contributes to the progressive degeneration of cochlear hair cells, further impairing hearing.
Characteristics, Chronic Forms and Causes
The cochlea is supplied by a single artery with no collateral circulation. The labyrinthine artery, from which the cochlear blood supply arises, is an end artery. Any reduction in blood flow caused by vasospasm, microembolism or atherosclerotic narrowing therefore cannot be compensated for by neighboring vessels.
As a result, the cochlea is immediately affected by ischaemia. The hair cells, particularly those located at the base of the cochlea and responsible for high-frequency hearing, are the first to be compromised.
Chronic cochlear ischaemia progresses insidiously. Patients may notice a gradual decline in hearing, particularly at higher frequencies, which is often attributed to normal ageing.
However, inadequate vascular supply can markedly accelerate the degeneration of cochlear hair cells. Early intervention aimed at improving cochlear perfusion may help slow this process.
Scientific Evidence Supporting the Use of Hyperbaric Oxygen Therapy
The scientific evidence supporting the use of hyperbaric oxygen therapy in cochlear ischaemia is based both on treatment outcomes in sudden sensorineural hearing loss, which is regarded as an acute manifestation of cochlear ischaemia, and on experimental studies demonstrating significant improvements in cochlear perfusion and metabolic function following hyperbaric oxygen therapy.
Studies involving patients with vascular risk factors and chronic hearing impairment have reported stabilisation or modest improvement in audiometric parameters after a course of hyperbaric oxygen therapy. These findings suggest that improving cochlear oxygenation may slow or halt the degenerative process, even in chronic forms of the condition.
The Role of Hyperbaric Oxygen Therapy
In cochlear ischaemia, hyperbaric oxygen therapy is used as an adjunctive intervention aimed at addressing the principal pathological mechanism: inadequate oxygen delivery to cochlear cells because of vascular insufficiency.
It does not replace the management of underlying vascular risk factors, which remains a fundamental component of treatment. Instead, it is used alongside these measures to supply the cochlea with oxygen that cannot be delivered adequately through the compromised vascular system.
The increased amount of oxygen dissolved in the plasma reaches the cochlea through the fluid compartments of the inner ear, helping to overcome the effects of arterial impairment.
Over the longer term, the stimulation of neovascularisation may improve cochlear perfusion, while the antioxidant effects of hyperbaric oxygen therapy help protect hair cells from the oxidative stress that accelerates their degeneration.
The treatment protocol is tailored according to whether the condition is acute or chronic and typically consists of 15 to 30 sessions, always in collaboration with the otorhinolaryngologist.