Sensorineural hearing loss (SNHL) results from damage to the inner ear (cochlear hair cells) or the auditory nerve, which hinders the transmission of sound signals to the brain. Unlike other forms of hearing loss, it is not caused by middle ear obstruction or fluid.
Sensorineural hearing loss, caused by ageing, loud noise exposure, genetics, illness, or medication, can be gradual or sudden. It often begins with the fading of high-frequency sounds, making consonants unclear and speech difficult to follow, especially in noisy environments like Singapore. Sound waves travel through the ear canal, eardrum, and middle ear bones to the cochlea, where tiny hair cells convert vibrations into an electrical signal. Damage to these tiny hair cells or the auditory nerve results in louder, less clear sound.
Since the inner ear is inaccessible, SNHL is diagnosed based on patient reports and audiometric testing. SNHL is typically permanent and classified as mild, moderate, severe, profound, or total.
Barrie Tan, ENT Head & Neck Surgery at Gleneagles Hospital, focuses on accurate diagnosis and practical, evidence-based care.
There are three main types of hearing loss, including:
This occurs when the tiny hair cells within the inner ear’s structures (cochlea) or the nerve pathways that transmit sound to the brain are damaged. The condition is typically associated with age-related hearing loss (presbycusis).
This type of hearing loss occurs when a problem in the outer or middle ear hinders sound waves from reaching the inner ear. Potential causes may include ear wax buildup, outer ear blockages, infections, or eardrum perforations.
This is a combination of sensorineural and conductive hearing loss, indicating potential damage in both the inner ear and the middle or outer ear.
Sensorineural hearing loss is usually permanent in gradual, long-term cases because damaged cochlear hair cells do not reliably regenerate, like in noise-induced hearing loss. Permanent hearing loss can also result from specific exposures, like ototoxic drugs, chemicals, or physical injuries, which irreversibly damage the inner ear or auditory nerve. However, sensorineural hearing loss treatment options are available, which are vital to improving auditory understanding, reducing listening strain, and protecting quality of life.
A critical exception is sudden sensorineural hearing loss, a rapid drop in hearing over hours or days. This is a medical emergency. Early sensorineural hearing loss treatment can improve recovery for suitable patients.
Common sensorineural hearing loss symptoms include:
Sensorineural hearing loss can cause associated symptoms like dizziness, anxiety and depression, which significantly lower quality of life. Many people with sensorineural hearing loss report that others seem to mumble. Inner-ear conditions, such as Meniere’s disease, which is linked to fluid pressure, can cause dizziness or imbalance, resulting in episodic vertigo, fluctuating hearing loss, and ear fullness. Patients commonly report ear fullness or pressure.
Understanding the causes of sensorineural hearing loss is essential for prevention and management. For example, is sensorineural hearing loss genetic? While genetics plays a role, noise-induced hearing loss from loud noises is largely preventable.
ENT specialists also look for asymmetry, meaning one ear is significantly worse than the other, which may indicate congenital hearing loss or other underlying causes. In selected cases, imaging, such as magnetic resonance imaging, is used to look for uncommon causes, such as an acoustic neuroma (a benign growth on the vestibulocochlear nerve).
Here are some of the other causes:
Age-Related Hearing Loss
Presbycusis, or age-related hearing loss, is common, usually gradual, and affects both ears. Risk factors include medical, genetic, environmental, and lifestyle factors.
Noise-Induced Hearing Loss
Noise exposure, whether occupational (e.g. construction, workshops) or recreational (e.g. loud music, gyms, extended headphone use, MRT stations), is a major contributor to hearing loss.
Occupational Noise Exposure
Loud, prolonged noise exposure damages delicate cochlear hair cells cumulatively. Occupational noise exposure above normal conversation levels (around 60 dB) increases this risk. Prolonged exposure to loud sounds increases the risk of permanent damage.
Infection
Infections such as meningitis and viral infections can lead to sensorineural hearing loss.
Viral Infections of the Inner Ear
Viruses such as mumps, measles, or herpes viruses can cause sudden, profound sensorineural hearing loss by damaging cochlear hair cells or by inflaming the auditory nerve, necessitating urgent medical evaluation. Viral infection of the inner ear requires immediate attention.
Head Injury or Head Trauma
Traumatic causes of hearing loss include a labyrinthine concussion (severe blow), which disrupts inner ear fluid and damages cochlear hair cells, temporal bone fractures, which can sever/compress the auditory nerve, and perilymph fistulas (ruptured inner/middle ear membranes from sudden pressure changes), causing immediate hearing loss and dizziness.
Certain Ototoxic Medicines
These drugs are known to damage the cochlea or the hearing nerve, leading to sensorineural hearing loss. Close monitoring by healthcare providers is essential.
Autoimmune Inner Ear Disease
This is less common but can cause rapidly progressive or fluctuating hearing loss and requires specialist assessment. This underlying cause benefits from medical therapy.
Other Causes
Systemic diseases such as diabetes, kidney disease, or autoimmune disorders can damage cochlear blood vessels, potentially leading to sensorineural hearing loss. Tumours can also affect the auditory nerve or brain pathways, though they are less common.
Sudden sensorineural hearing loss often feels like a blocked ear in the affected ear, yet the ear examination can be regular. Sudden deafness refers to acute, rapid-onset hearing loss that occurs over a short period, often within hours or days, and requires immediate medical attention. Many people describe waking up and realising that one ear is not hearing clearly, sometimes accompanied by intense tinnitus or dizziness.
If sudden hearing loss is accompanied by neurological symptoms such as facial weakness, limb weakness, severe headache, or double vision, emergency care is essential because stroke can mimic ear-related symptoms. Itis a medical emergency, so it is not a condition to wait out. Early assessment is recommended because time matters. Treatment may include systemic steroids (tablet treatment) and, in selected cases, intratympanic steroid therapy (steroid delivered through the eardrum) to target the inner ear.
If you’re wondering if sudden sensorineural hearing loss is reversible. Some cases may respond to early intervention.
Maps air and bone conduction hearing thresholds across pitches to differentiate between conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
Sensorineural hearing loss audiograms show similarly reduced air-and bone-conduction thresholds, excluding conductive hearing loss. Due to the cochlea’s tonotopic organisation, sensorineural hearing loss often affects specific frequencies, affecting consonants.
A notch at 4 kHz on an audiogram suggests noise-induced hearing loss. Perceived loudness is not proportional to sound pressure level. Age-related loss typically shows a gradual decline in high frequency. However, tone thresholds alone are insufficient; audiograms must be interpreted alongside speech understanding for clarity.
While chronic, irreversible cases stem from permanent hair cell damage, sudden sensorineural hearing loss often responds to urgent treatment. This deafness can cause social isolation and cognitive decline, making early auditory rehabilitation, usually with hearing aids, critically important. This leaves many to ask, “Is sensorineural hearing loss reversible?”
Currently, no cure exists for chronic cases, but the real question is, “Can sensorineural hearing loss get better?” The answer is yes; functional improvements are achievable.
When to See an ENT Specialist for Sudden Sensorineural Hearing Loss
For sudden sensorineural hearing loss, especially in one ear, see an ENT specialist immediately (within 24-72 hours); prompt steroid treatment is vital for recovery. Consult an ENT for persistent muffled hearing, tinnitus, imbalance, or gradual hearing loss that affects your life, as these may indicate inner-ear issues that require expert diagnosis. Early intervention is crucial.
Medical therapy is used to potentially treat underlying causes, particularly sudden sensorineural hearing loss or inner ear inflammation.
Sensorineural hearing loss treatment options vary based on individual needs. For patients with stable, long-term hearing loss, the primary focus is rehabilitation. Goals include improving speech understanding, reducing listening effort, and enhancing quality of life. In Singapore, this rehabilitation must specifically address the acoustic challenges of local environments, such as hawker centres, open-plan offices, and public transport.
For sensorineural hearing loss that impacts daily life, hearing aids are typically the first line of treatment. These hearing devices employ digital processing, directional microphones, and noise-management technology to improve access to speech.
Optimal results depend on a precise fitting process: conventional hearing aids are initially programmed according to the patient’s audiogram and then fine-tuned based on feedback from real-world use. As the brain needs time to adapt, the initial period of wearing hearing aids can feel unusual, making early follow-up appointments and adjustments crucial.
To further improve speech understanding in noisy environments, structured listening practice, known as auditory training, is often recommended. This can help reduce listening fatigue and increase participation both at work and at home. Regular hearing tests help monitor the sensorineural hearing loss prognosis.
Hearing aids amplify sound, but effective clarity depends on the inner ear’s ability to transmit clear nerve signals. Simply increasing volume often fails to restore clarity when a person’s word recognition is poor and they cannot hear soft sounds clearly.
When conventional hearing aids are insufficient, cochlear implants are an alternative. These hearing devices convert sound waves into electrical signals, directly stimulating the auditory nerve and bypassing damaged tiny hair cells. This action often significantly improves access to speech.
Cochlear implantation, a surgical procedure performed under general anaesthesia, involves placing an internal implant and electrode array into the cochlea. Following the healing period, the external sound processor is fitted, programmed (known as mapping), and the patient begins the necessary auditory rehabilitation.
It is essential to understand that a cochlear implant is not an immediate solution. Success requires ongoing programming and auditory therapy to train the brain to interpret the new sounds. For adults with profound hearing loss and profound sensorineural hearing loss, cochlear implants have been shown to significantly improve speech understanding and overall quality of life.
Candidacy is determined through detailed hearing tests and speech tests, typically conducted with appropriate hearing aids. In specific cases, implantation may also be considered for individuals with single-sided deafness or highly asymmetric hearing loss, particularly if they experience intrusive tinnitus.
Achieving the best long-term outcomes requires consistent use of the device, attendance at follow-up appointments, and commitment to rehabilitation. This makes coordinated care among the ENT specialist, audiologist, and speech and hearing therapists essential for success.
Clear hearing is more than sound. It is about confidence, safety, and staying connected. For an assessment at Barrie Tan ENT Head & Neck Surgery at Gleneagles Hospital in Singapore, contact our specialised hearing clinic to arrange appropriate hearing tests and a personalised plan.
Yes. Hearing aids or cochlear implants, when correctly fitted, can significantly improve speech understanding and reduce listening fatigue.
MBBS, MRCS (Edinburgh), MMed (Otorhinolaryngology), FAMS
Dr Barrie Tan is an ENT specialist at Gleneagles Hospital, Singapore, with more than 20 years of clinical and surgical experience. He previously served as Head of ENT and Director of the Centre for Hearing and Ear Implants at Singapore General Hospital. The information provided is not intended as medical advice. More about our medical experts.
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