Weber Test

Anatomy and Physiology

To understand the Weber test, one has to understand the basic anatomy of hearing.

The ear anatomically consists of the sound-conducting system (outer and middle ear) and the sound-transducing system (the cochlea).

• The outer ear: Pinna and external ear canal
• The middle ear: Tympanic membrane, ossicular chain (malleus, incus, stapes), and middle ear space[5]
• The inner ear: Cochlea (organ of hearing), vestibular labyrinth (organ of balance)

The purpose of the outer ear is to direct sounds onto the tympanic membrane. The sound vibrations are then transmitted through the middle ear via the ossicular chain before reaching the cochlea. The cochlea plays a vital role in transducing these vibrations into nerve impulses via the auditory nerve (vestibulocochlear nerve), which is then delivered along the central pathways to the auditory cortex, where it is processed and perceived as sound. This pathway is termed air conduction. However, sound can also be transmitted via bone conduction, where vibrations are transmitted via the skull and delivered directly to the cochlea, buried within the temporal bone.[6][7]

Hearing loss may occur due to interruption at any point along these pathways. 

The Weber test, along with its paired Rinne test, is commonly used to distinguish the site and likely cause of hearing loss. Conductive hearing loss is due to problems with the sound-conducting system, while sensorineural hearing loss is due to problems with the sound-transducing system, the auditory nerve, or its central pathways. Occasionally, one can get a mixed hearing loss, which is a combination of the two types of hearing loss.[8]

Indications

In normal hearing, an individual will hear equally on both sides of the ear. The Weber test is a test of lateralization and is most useful in those with asymmetrical hearing loss.

Weber Test Principles

The inner ear is more sensitive to sound via air conduction than bone conduction (in other words, air conduction is better than bone conduction).

In the presence of a purely unilateral conductive hearing loss, there is a relative improvement in the ability to hear a bone-conducted sound. This can be explained by the following:

• Masking effect: The sound heard via the affected ear has less environmental noise reaching the cochlea via air conduction (for example, the environmental noise is masked) compared to the unaffected ear, which receives sounds from both bone conduction and air conduction. Therefore, the affected ear is more sensitive to bone-conducted sound.[9]
• Occlusion effect: Most of the sound transmitted via bone conduction travels to the cochlea. However, some of the low-frequency sounds dissipate out of the canal. A conductive hearing loss (in other words, when an occlusion is present) will prevent external dissipation of these frequencies and lead to increased cochlear stimulation and loudness in the affected ear.[10]

In the presence of sensorineural hearing loss, the sound will be perceived louder in the unaffected ear, which has a better cochlea.

Equipment

An ideal tuning fork of choice for the Weber test would be one that has a long period of tone decay; in other words, the tone maintains/lasts long after the tuning fork has been struck and cannot be detected by the sense of bone vibration, therefore preventing misinterpretation of the vibration as sound.

512-Hz Tuning Fork

In clinical practice, the 512-Hz tuning fork has traditionally been preferred. At this frequency, it provides the best balance of time of tone decay and tactile vibration. Lower-frequency tuning forks like the 256-Hz tuning fork provide greater tactile vibration. In other words, they are better felt than heard. Higher-frequency tuning forks, for example, the 1024-Hz tuning fork, have a shorter tone decay time.

256-Hz Tuning Fork: An Alternative

The 256-Hz tuning fork and the 128-Hz tuning fork are commonly used as part of neurological examination due to their greater tactile vibration characteristic. However, evidence suggests that the 256-Hz provides better reliability when compared to the 512-Hz.[11][12]

Preparation

• Ideally, the test should be carried out in a quiet room
• Verbal consent should be gained before performing the test
• Clear instructions should be given to the patient to avoid misinterpretation of the test

Technique or Treatment

Tuning Fork

The audiometric tuning fork generally consists of the tines (the U-shaped prongs), the stem, and the footplate.

Striking the Tuning Fork 

1. Hold the tuning fork by the stem between the thumb and the first finger.
2. Strike the tines one-third of the way from the free end of the prong onto a firm but elastic object (e.g., the clinician's knee or elbow). This will produce a relatively pure tone.
3. Avoid striking the tines onto a hard surface, as this may damage the tuning fork and produce multiple overtones.

Performing Weber Test 

1. Place the vibrating tuning fork on the vertex (other common sites used are the midline of the forehead, bridge of the nose, and chin), equidistant from both ears. These vibrations will be conducted through the skull and reach the cochlea.
2. Ask the patient whether it is heard loudest in either one side or the midline (e.g., "Is the sound louder in your right ear, left ear, or the middle?")[13]

Interpretation

Normal Hearing

• Weber test does not demonstrate lateralization: In a normal subject, the sound should be heard in the middle and equally on both sides.
• Rinne test: Normal/positive in both ears (AC greater than BC)

Unilateral Sensorineural Hearing Loss

• Weber test lateralizes to the unaffected ear. In other words, it is heard louder in the better ear.[14]
• Rinne test: Normal/positive on the affected ear (AC greater than BC); normal/positive on the unaffected ear (AC greater than BC)

Note: an abnormal/negative response on the affected ear (BC greater than AC) can also occur in a severe sensorineural hearing loss, also called a dead ear. This is termed a "false negative." Rinne test "true negative" only occurs if there is a conductive hearing loss element. However, when testing a dead ear, the bone conduction is perceived to be heard louder than air conduction due to a cross-over of bone conduction detected by the opposite normal-functioning cochlear, resulting in a Rinne false negative.

Unilateral Conductive Hearing Loss

• Weber test lateralizes to the affected ear. In other words, it is heard louder in the poorer ear.
• Rinne test: Abnormal/negative on the affected ear (BC greater than AC); normal/positive on the unaffected ear (AC greater than BC)[15]

Symmetrical Conductive Hearing Loss

• Weber test does not demonstrate lateralization.
• Rinne test: Abnormal/negative on the affected ear (BC greater than AC)

Complications

The Rinne test is a complement to the Weber test. They are screening tests and do not replace formal audiometry. It is important to note that further examinations and investigations such as otoscopy, audiometry, tympanometry, and imaging may be required to correctly diagnose the cause of the hearing loss and allow appropriate management. Generally, this procedure has no complications as it is a relatively non-invasive method of screening patients for hearing loss.

Clinical Significance

Clinical Use

• In the primary care setting, it is useful to use the Weber and Rinne tests to help the clinician differentiate between conductive hearing loss and sensorineural hearing loss. This will guide the clinician to the need for further examination, investigation, and management.
• In the postoperative setting, the test is commonly used as a quick bedside test for examining a complication of a dead ear (complete sensorineural hearing loss).
• The Weber and Rinne tuning fork tests can be used to confirm audiometric findings, particularly when the audiogram is not consistent with clinical findings.
• In assessing a patient with bilateral conductive hearing loss, the Weber test is a quick and useful test for the otorhinolaryngology (ENT) surgeon to help determine which side of the ear to operate on first. Usually, the ear with the more significant conductive hearing loss is preferred.[16][15][17]

Possible Causes (Non-Exhaustive) of Hearing Loss

Conductive Hearing Loss

Outer Ear Causes

• Impacted wax[18]
• Infection affecting the outer ear (otitis externa)[19]
• A foreign body within the external ear canal
• Squamous cell carcinoma
• Congenital microtia[20]

Middle Ear Causes

• Tympanic membrane trauma
• Infection affecting the middle ear (acute otitis media)[21]
• Glue ear (otitis media with effusion)[22]
• Otosclerosis
• Cholesteatoma[23]
• Congenital malformation
• Temporal bone trauma

Sensorineural Hearing Loss

Inner Ear Causes

• Hereditary hearing loss
• Presbycusis[24]
• Labyrinthitis
• Meniere disease
• Viral cochleitis
• Vascular insult
• Autoimmune conditions
• Noise exposure
• Vestibular schwannoma[25]
• Ototoxic drugs
• Trauma

Enhancing Healthcare Team Outcomes

The Weber test is used by multiple health professionals operating as an interprofessional team, including primary care providers, physician associates (PAs) and nurse practitioners (NPs), otorhinolaryngologists, neurologists, internists, and chiropractors, to evaluate the patient's hearing. The test is almost always used along with the Rinne test to differentiate between conductive hearing loss from a sensorineural hearing loss. This will guide the clinician to the need for further examination, investigation, and management. Also, the Weber and Rinne tuning fork tests can be used to confirm audiometric findings, particularly when the audiogram is inconsistent with clinical findings. In assessing a patient with bilateral conductive hearing loss, the Weber test is a quick and useful test for the otorhinolaryngologist to help determine which side of the ear to operate on first. Usually, the ear with the more significant conductive hearing loss is preferred.

All interprofessional team members need to accurately record their examination findings, including Weber test results, so that all team members can access accurate, updated patient information to guide their decision-making, leading to improved patient care and outcomes.