Stroke-Induced Hearing Loss: Understanding The Unexpected Risk

Strokes can affect all levels of the auditory pathway and lead to hearing loss. Sudden-onset hearing loss after a stroke is one of the less frequent neurologic impairments, while cortical or central deafness is even rarer. However, studies indicate that hearing loss is very common in populations with stroke, and a past history of stroke increases the likelihood of hearing loss. Hearing loss may hinder communication between patients and healthcare professionals, restricting participation in rehabilitation programs and limiting improvements in physical performance.

The risk of stroke development among patients with sudden sensorineural hearing loss (SSNHL) was investigated in a 2008 study based in Taiwan. The study evaluated 7,115 patients over five years, finding that the hazard for having a stroke was 1.64 times greater for SSNHL patients than the control group. This indicates that sudden hearing loss may serve as an early warning sign for a stroke.

Another study, published in 2021, reviewed 46 cases of stroke-associated cortical deafness, caused by bilateral lesions within the central auditory pathway. The review found that stroke-associated cortical deafness is rare and severe, resulting from combinations of cortical and subcortical lesions within the central auditory pathway.

Sudden Sensorineural Hearing Loss (SSNHL)

SSNHL can hinder communication between patients and healthcare professionals, thereby restricting participation in rehabilitation programs and limiting physical performance improvements. The relationship between stroke and SSNHL is unclear, but studies have shown that patients with stroke had a higher risk of subsequent SSNHL compared with patients without stroke. A study based in Taiwan found that the hazard for having a stroke was 1.64 times greater for SSNHL patients than the control group, indicating that sudden hearing loss may serve as an early warning sign for a stroke.

The prognosis for hearing recovery for idiopathic SSNHL depends on several factors, including the severity of hearing loss, age, presence of vertigo, and shape of the audiogram. The majority of patients with idiopathic SSNHL will regain some degree of hearing, and natural history and placebo-controlled studies have shown hearing recovery rates of 32% to 65% without treatment. Treatment for SSNHL currently consists of early initiation of steroids with antivirals as a possible adjunct, but the effectiveness of these treatments is poorly understood, and there is no national standard or guidance for the management of idiopathic SSNHL.

Cortical Deafness

Patients with cortical deafness cannot hear any sounds and are not aware of sounds, including non-speech, voices, and speech sounds. Although patients appear and feel completely deaf, they can still exhibit some reflex responses, such as turning their head towards a loud sound. Cortical deafness can be difficult to diagnose as it shares similarities with auditory agnosia, and its causes can vary significantly.

The treatment options for cortical deafness are limited. Cochlear or auditory brainstem implantation may be considered, as electrical stimulation of the peripheral auditory system may improve sound perception or cortical remapping. Rehabilitation and speech therapy are recommended to improve the patient's communication skills.

Auditory Processing Deficits

The exact incidence of auditory processing deficits after a stroke is unknown, but it is believed to be underrecognized and underinvestigated. Studies have found that a substantial proportion of stroke patients may experience and report severe auditory functional limitations.

The impact of auditory processing deficits on an individual's functioning and quality of life can be significant. These deficits can lead to challenges in communication, social interaction, and participation in rehabilitation programs.

There is a need for early identification and intervention for individuals with auditory processing deficits after a stroke. This may include comprehensive audiological assessments, rehabilitation plans, and the use of assistive devices, such as personal frequency-modulated (FM) systems, to improve speech perception and reduce the negative impact on everyday life.

Hearing Loss as a Warning Sign

Hearing loss can be a frightening experience, especially when it occurs suddenly. Sudden Sensorineural Hearing Loss (SSNHL) is defined as a hearing impairment of at least 30 dB in three sequential frequencies. While there are no known causes for sudden hearing loss, vascular occlusion is often listed as a possible cause, along with viral and bacterial infections, ruptured inner ear membranes, tumours, and autoimmune diseases.

The Link Between Hearing Loss and Stroke

The vascular system's role in sudden hearing loss has led researchers to study a possible connection between hearing loss and strokes. A stroke occurs when there is an obstruction in the blood supply to the brain, resulting in brain damage. A study based in Taiwan sought to determine whether there was a link between SSNHL episodes and an increased risk of stroke. The study evaluated 7,115 patients over five years, finding that SSNHL patients had a 150% increased chance of having a stroke compared to a control group. This indicates that sudden hearing loss may serve as an early warning sign of a stroke.

Hearing Loss After a Stroke

Hearing loss after a stroke is also a possibility, with studies indicating that hearing loss is very common in stroke populations. Furthermore, individuals with a history of stroke have an increased likelihood of experiencing hearing loss. Post-stroke hearing loss can hinder communication between patients and healthcare professionals, impacting rehabilitation and physical performance.

Recommendations

It is recommended that individuals who have experienced sudden hearing loss undergo a comprehensive neurological exam and schedule routine follow-ups, even years after the initial event. Additionally, clinicians should carefully investigate the possibility of subsequent hearing impairments in stroke patients. Close monitoring of hearing status can facilitate early detection and timely management of hearing deficits. Enhancing communication can help relieve psychological burdens and facilitate rehabilitation.

Stroke and Hearing Loss Treatment

Sudden sensorineural hearing loss (SSHL) is a frightening experience where hearing loss occurs instantly or over several days. It can affect one or both ears and range in severity, sometimes becoming permanent. While the causes of SSNHL are not always known, vascular occlusion is often listed as a possible cause, along with viral and bacterial infections, ruptured inner ear membranes, tumours, and autoimmune diseases. As SSNHL is linked to vascular issues, researchers have studied the connection between sudden hearing loss and strokes.

Treatment

If you experience sudden hearing loss, it is important to seek urgent medical treatment to prevent permanent hearing loss. Doctors will first examine your ear to rule out any obstruction, such as earwax or fluid. If your ear is clear, they will perform a pure tone audiometry test to identify sensorineural hearing loss. This involves playing different frequencies of sound at varying volumes to determine your hearing threshold.

If SSNHL is diagnosed, further tests may be ordered to determine the cause. Corticosteroids are the standard treatment for SSNHL and help to reduce inflammation and swelling, thereby restoring hearing. These can be administered orally or injected into the middle ear to allow the medication to flow directly into the inner ear. Treatment should be started as soon as possible, as delaying treatment may result in permanent hearing loss.

In addition to corticosteroids, other treatments may be required depending on the underlying cause of SSNHL. For example, if it is caused by a particular medication, switching medications may be recommended. If hearing loss is severe or does not respond to treatment, hearing aids or cochlear implants may be necessary.

Stroke Prevention

As SSNHL has been identified as a possible early warning sign of stroke, it is important to monitor your health and look for signs of an impending stroke. A comprehensive neurological exam and routine follow-ups are recommended, even years after the initial event. According to a 2008 study, the average time between SSNHL hospitalization and the onset of stroke was 804 days, with most strokes occurring within the first two years.

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