Sensorineural Hearing Loss: Symptoms, Types, Causes and Treatment

Sensorineural hearing loss (SNHL) is the most common type of permanent hearing loss, arising from damage to the inner ear or the neural pathways that connect the ear to the brain. Whether experienced suddenly or gradually, SNHL can profoundly impact communication, quality of life, and social participation. Understanding its symptoms, types, causes, and treatments is essential for early diagnosis and effective management.

Symptoms of Sensorineural Hearing Loss

Sensorineural hearing loss can manifest in various ways, often affecting people differently depending on the underlying cause, severity, and part of the auditory pathway involved. Recognizing these symptoms early can make a significant difference in outcomes, especially since SNHL may be sudden or progressive.

Symptom	Description	Associated Conditions	Sources
Hearing loss	Partial to profound reduction in hearing	Sudden/gradual onset	1 2 3 5
Tinnitus	Ringing, buzzing, or hissing in the ear	Often accompanies SNHL	1 2 3 5
Vertigo	Sensation of spinning/dizziness	May occur with some types	4 5 6
Aural fullness	Feeling of pressure in the ear	Common in sudden SNHL, IIH	2 3 5

Table 1: Key Symptoms

Hearing Loss: The Core Symptom

The most obvious and defining symptom of SNHL is hearing loss itself. This loss can range from mild difficulty hearing faint sounds to complete deafness. It may develop suddenly, as in sudden sensorineural hearing loss (SSNHL)—a medical emergency where hearing drops by at least 30 dB over three adjacent frequencies within 72 hours—or it can be gradual and progressive, as seen in age-related or noise-induced hearing loss 1 2 5 6.

Tinnitus

Tinnitus, the perception of sound without an external source, is frequently reported among those with SNHL. It can manifest as ringing, buzzing, or hissing, and may be constant or intermittent. Tinnitus is particularly common in sudden SNHL and conditions like idiopathic intracranial hypertension (IIH) 1 2 3 5.

Vertigo and Balance Issues

Vertigo—a spinning or dizzy sensation—sometimes accompanies SNHL, especially when the vestibular system is involved. This is more likely in cases with inner ear hemorrhage, Menière’s disease, or acute infections 4 5 6.

Aural Fullness

A feeling of pressure or fullness in the ear, known as aural fullness, is another common symptom. While not always present, it's frequently reported in sudden SNHL and IIH, and can help differentiate SNHL from other types of hearing loss 2 3 5.

Types of Sensorineural Hearing Loss

SNHL is not a single disease, but a group of disorders with diverse presentations, patterns, and underlying mechanisms. Classifying the types of SNHL helps guide diagnosis, management, and prognosis.

Type	Features	Typical Presentation	Sources
Sudden SNHL	Rapid onset, often unilateral	Emergency, acute symptoms	1 2 4 6
Unilateral SNHL	Affects one ear only	Chronic or sudden	5 13
Bilateral SNHL	Both ears affected	Congenital or acquired	1 13
Hereditary	Genetic mutations, often bilateral	Early onset, family history	8 10 13
Syndromic SNHL	Part of a syndrome, multisystem	Other symptoms present	8 13
Acquired SNHL	Non-genetic, e.g., noise, drugs	Any age, varied speed	7 9 11 16

Table 2: Main Types of Sensorineural Hearing Loss

Sudden Sensorineural Hearing Loss (SSNHL)

SSNHL is defined by its rapid onset—usually within 72 hours—and often affects only one ear. It is a medical emergency, requiring prompt evaluation and treatment to maximize the chance of recovery. SSNHL can be idiopathic or have identifiable causes such as infections, vascular events, or autoimmune disorders 1 2 4 6 12.

Unilateral vs. Bilateral SNHL

• Unilateral SNHL: Involves one ear. It can be chronic or sudden and is sometimes linked to structural anomalies, infections, or idiopathic causes. Unilateral SNHL may be harder to detect, especially in children 5 13.
• Bilateral SNHL: Both ears are affected. Bilateral SNHL is often genetic (especially in children) but may also result from systemic diseases, exposure to ototoxic drugs, or noise 1 13.

Hereditary and Syndromic Types

Genetic forms of SNHL may be non-syndromic (affecting just hearing) or syndromic (with additional symptoms such as vision loss, kidney disease, or neurological issues). X-linked, autosomal dominant, and recessive inheritance patterns are seen, with early diagnosis being crucial for appropriate intervention and genetic counseling 8 10 13.

Acquired Sensorineural Hearing Loss

Acquired SNHL develops due to environmental or health-related factors, including:

• Noise exposure (occupational, recreational)
• Ototoxic medications (certain antibiotics, cancer therapies)
• Infections (viral, bacterial)
• Aging (presbycusis)
• Autoimmune conditions
• Trauma 7 9 11 16

Causes of Sensorineural Hearing Loss

Understanding what causes SNHL is key to prevention and tailored treatment. Causes can be broadly grouped into genetic, environmental, and idiopathic (unknown) categories.

Cause	Example Mechanisms	Notes / Risk Factors	Sources
Genetic	Mutations, syndromic/non-syndromic	Early onset, family history	8 10 13
Noise	Hair cell/synapse damage	Occupational/recreational	7 11 19
Ototoxic Drugs	Hair cell, neural toxicity	Aminoglycosides, chemo	9 7 16 19
Aging	Mitochondrial dysfunction	Gradual, bilateral	7 11
Infections	Viral, bacterial	CMV, HSV, EBV, COVID-19	1 2 12 13
Autoimmune	Inflammatory inner ear disease	Rapid progression possible	2 12 14
Vascular	Reduced blood supply to cochlea	Sudden onset, risk factors	2 12
Structural	Cochlear/labyrinth anomalies	Common in children (unilateral)	13
Idiopathic	Unknown	Most SSNHL cases	6 12 17

Table 3: Major Causes of Sensorineural Hearing Loss

Genetic Causes

• Non-syndromic genetic SNHL: Caused by mutations affecting only hearing. Over 100 genes are implicated, including X-linked forms 8 10 13.
• Syndromic SNHL: Hearing loss is part of a broader syndrome, potentially involving vision, balance, or other organs. Early identification aids prognosis and management 8 13.

Environmental and Acquired Causes

• Noise-Induced Hearing Loss: Exposure to loud sounds damages hair cells and synapses within the cochlea, resulting in both immediate and delayed hearing deficits. Notably, some neural degeneration may occur even before hair cell loss is apparent 7 11 19.
• Ototoxicity: Medications like aminoglycoside antibiotics, chemotherapeutic agents (e.g., cisplatin), loop diuretics, and some non-steroidal anti-inflammatory drugs can irreversibly damage hair cells or their supporting structures 9 7 16 19.
• Aging (Presbycusis): Age-related hearing loss is linked to accumulated mitochondrial DNA damage, oxidative stress, and degeneration of cochlear structures 7 11.

Infectious and Autoimmune Causes

• Viral Infections: Cytomegalovirus (CMV), herpes simplex virus (HSV), Epstein-Barr virus (EBV), and even COVID-19 are known infectious triggers, especially in sudden or congenital cases 1 2 12 13.
• Autoimmune Inner Ear Disease: The body’s immune system mistakenly attacks inner ear tissues, leading to rapid, progressive hearing loss that may respond to immunosuppressive therapy 2 12 14.

Vascular and Structural Causes

• Vascular Insufficiency: Sudden loss of blood flow to the cochlea can cause abrupt hearing loss; this is sometimes implicated in SSNHL 2 12.
• Structural Anomalies: Especially in children, malformations of the cochlea or labyrinth are frequent causes of unilateral SNHL 13.

Idiopathic Cases

Despite extensive testing, a large proportion of SNHL cases—especially SSNHL—remain idiopathic, with no identifiable cause. In such cases, treatment is often empirical, and prognosis can be variable 6 12 17.

Treatment of Sensorineural Hearing Loss

Advances in medicine have improved the management of SNHL, yet many forms remain irreversible. Treatment is tailored to the type, cause, and severity of hearing loss, and early intervention is key to optimizing outcomes.

Treatment	Approach/Mechanism	Effectiveness/Notes	Sources
Steroids	Reduce inflammation, immune response	Standard for sudden SNHL	1 6 17
Hearing Devices	Amplify sound (aids, implants)	Mainstay for permanent loss	10 16
Hyperbaric Oxygen	Improves cochlear oxygenation	Adjunct for sudden SNHL	18
Antioxidants	Reduce oxidative stress	Under investigation	7 15
Gene Therapy	Correct genetic defects	Experimental	15
Nanotechnology	Targeted drug delivery	Emerging, preclinical	16
Personalized Medicine	Etiology-driven treatment	More effective outcomes	2 13

Table 4: Treatments for Sensorineural Hearing Loss

Steroid Therapy

Systemic or intratympanic steroids are the gold standard for sudden SNHL, especially when initiated early. They work by reducing inflammation and immune-mediated damage in the inner ear. However, about half of treated patients experience only partial improvement, and the effectiveness may not correlate with duration, side, or severity of the initial hearing loss 1 6 17.

Hearing Devices: Aids and Implants

For irreversible or congenital SNHL, hearing aids and cochlear implants are the primary interventions. Early fitting in children is crucial for language development. Cochlear implants can restore significant hearing in those with profound bilateral SNHL 10 16.

Hyperbaric Oxygen Therapy

As an adjunct to steroids, hyperbaric oxygen therapy (HBOT) can improve cochlear oxygenation and may enhance hearing recovery in sudden SNHL. While generally safe, its use is limited to specialized centers 18.

Antioxidant and Emerging Therapies

Mounting evidence implicates oxidative stress in SNHL pathogenesis, spurring research into antioxidant therapies. Several clinical trials are underway to assess molecules that target cell death pathways and reduce free radical damage. Early results are promising, but translation to clinical practice awaits further validation 7 15.

Gene and Cell-Based Therapies

Cutting-edge research explores gene therapy to correct underlying mutations and cell therapy to regenerate lost hair cells. Virus-delivered transcription factors and nanotechnology-based delivery systems are on the horizon, but these remain experimental 15 16.

Nanotechnology and Targeted Delivery

Innovations in nano-based drug delivery may overcome barriers to effective inner ear treatment. Nanoparticles and nanohydrogels can facilitate noninvasive, targeted therapies, especially for drug-induced SNHL 16.

Personalized and Etiology-Driven Treatment

Identifying the specific cause of SNHL (genetic, infectious, autoimmune, etc.) enables more personalized treatments, improving outcomes and prognoses. Comprehensive diagnostic evaluations—including imaging, genetic testing, and serology—are increasingly used for this purpose 2 13.

Conclusion

Sensorineural hearing loss is a complex and multifaceted condition that can have a profound impact on individuals and society. Understanding its symptoms, types, causes, and treatments is essential for timely diagnosis and effective management.

Key Takeaways:

• Symptoms: SNHL presents with hearing loss, tinnitus, vertigo, and aural fullness, which may be sudden or progressive 1 2 3 5.
• Types: Includes sudden, unilateral, bilateral, hereditary, syndromic, and acquired forms—with variable presentations and prognoses 1 2 4 5 8 10 13.
• Causes: Range from genetic mutations to noise, ototoxic drugs, infections, aging, autoimmune disease, vascular events, and structural anomalies. Many cases remain idiopathic 7 8 9 10 11 12 13.
• Treatment: Early steroids for sudden SNHL, hearing devices for permanent loss, adjunctive therapies like HBOT, and emerging treatments targeting oxidative stress, gene defects, and cell regeneration. Personalized medicine is increasingly important 1 2 6 10 13 15 16 17 18.

Early recognition and intervention remain the cornerstones of effective care for sensorineural hearing loss. Advances in diagnostics and therapeutics promise a future of more targeted and effective treatments for this widespread and impactful condition.