Nonorganic Functional Hearing Loss

Etiology

Nonorganic functional hearing loss may result from conscious or unconscious motives along a spectrum from malingering to conversion disorder. The Austen-Lynch model describes the causative factors of nonorganic functional hearing loss based on the patient’s level of intent in demonstrating the hearing deficit.[2] 

The three categories described are conversion disorder (low level of intent), factitious disorder (moderate level of intent), and malingering (high level of intent). These three entities exist on a continuum. The lower the level of intent, the more internal and unconscious the rewards of the hearing deficit.

The frequency of the etiologies of nonorganic functional hearing loss differs between children and adults. Etiologies also differ among subpopulations within these groups. In adults, nonorganic functional hearing loss is frequently due to malingering motivated by monetary gains or compensatory claims.[3] Conversion disorder is less common and mainly occurs after traumatic experiences.[4] 

In children, emotionally or physically traumatic events may cause nonorganic functional hearing loss to present as conversion disorder.[5][6][7] Malingering in children is also known to occur because of below-average academic achievement.[8] 

The Austen-Lynch model also hypothesizes that the motives behind nonorganic functional hearing loss may not remain static. It posits movement up the continuum, from greater to lesser intention, or movement down the continuum from lesser to greater intention. An example of movement down the continuum would be an individual that begins with a conversion disorder; however, the increased sympathy shown by peers may cause conscious awareness of the external gains.

These gains serve as motivations for the perpetuation of the symptoms. Depending on whether the gains are internal or external, the individual may begin to feign the symptoms, progressing from a conversion disorder to malingering or a factitious disorder.

Epidemiology

Marked differences exist between centers in the reported frequency of the diagnosis of nonorganic functional hearing loss.[9] Most authors agree that the prevalence of nonorganic functional hearing loss is underestimated, most likely due to a lack of awareness and misdiagnosis.[10][11][12] 

Nonorganic functional hearing loss incidence varies from 2% to 7%. Nonorganic functional hearing loss is more prevalent in children when compared to the general population.[8] A 2009 study by Psarommatis et al. found that nonorganic functional hearing loss was the most common cause of sudden hearing loss in children.[13] The peak incidence of nonorganic functional hearing loss in children is at 10 to 12 years of age.[14] 

In 1965, Berger et al. suggested that the increased prevalence of nonorganic functional hearing loss in this group may be due to educational stress resulting from a transfer to secondary school.[15]

This is especially true for children with below-average intelligence because they may manage primary school with few or no problems, but transfer to more challenging secondary school may serve as a trigger for nonorganic functional hearing loss.[16] 

In 2010, Holenweg et al. found that the age distribution of nonorganic functional hearing loss was greater even in adults between 19 and 57 years of age compared to children.[17] In their study, no individual above 57 years presented with nonorganic functional hearing loss. Bilateral ear involvement is more common in nonorganic functional hearing loss, and females are more commonly affected than males.[10][11][13][17]

Pathophysiology

Nonorganic functional hearing loss implies an absence of anatomical or physiological pathology within the auditory system. In malingering, the symptoms are intentionally feigned or grossly exaggerated. The driving force behind these behaviors is secondary gain, such as financial compensation.[18] 

In factitious disorder, symptoms are intentionally feigned or exaggerated for psychological gains, such as care or compassion from others. The driving force behind these behaviors is the benefits obtained from assuming a sick role.[2] 

In conversion disorder, symptoms are unintentionally produced. This psychological change is often preceded by stresses such as interpersonal conflicts.[2][10] 

Conversion disorder represents a psychological defense mechanism in which emotional trauma is unconsciously translated into physical disability. The somatic symptom represents the resolution, although symbolic, of a psychological conflict.

History and Physical

Obtaining a thorough history and physical examination is paramount when attempting to identify nonorganic functional hearing loss or exclude any underlying organic pathology. Many behaviors and clinical clues may be revealed during history taking and physical examination, guiding the examiner to suspect nonorganic functional hearing loss. Therefore, the examiner must observe the patient's behaviors keenly throughout the examination and history-taking process. The patient may cup the ear and rely excessively on lip reading and yet be able to answer the examiner when he turns away from the patient. Other patients may speak softly (patients with hearing loss often speak loudly as they cannot hear their own voices well) and appear nervous.[19] 

Such behaviors are important clues suggesting nonorganic functional hearing loss. In cases of unilateral hearing loss, however, reactions to sounds and communication abilities cannot be used to suggest nonorganic functional hearing loss.[20] 

The examiner should also note the source of the patient's referral, as insurance/compensatory claims companies often refer malingerers for evaluation.[21] A complete audiological history of the hearing loss, including onset, rapidity of progression, whether the hearing loss fluctuates or not, laterality of symptoms, and other associated symptoms such as vertigo, aural fullness, pain, and tinnitus should be taken. Histories of noise exposure, barotrauma, head trauma, ototoxic drug exposure, and previous ear surgery are elicited.[22] The hearing loss is often sudden, bilateral, with no accompanying symptoms, and is preceded by some emotional conflict.[10][14][23] 

A thorough history of any cause of emotional conflict or distress must be taken. Family problems, difficulties at work or school, recent psychological trauma, a sense of a lack of attention by parents (in the case of children), or a recent diagnosis of a life-threatening illness may be present.[13][14][24][25] 

History of psychiatric illness is important to note, as is a history of previous hearing loss or ear disease. Concomitant non-audiological symptoms such as unexplained weight loss and insomnia should be considered possible indicators of underlying psychological stress contributing to nonorganic functional hearing loss.[26] 

Anxiety over new school environments (e.g., skipping a grade, transferring to secondary school) may cause nonorganic functional hearing loss in children. In other cases, some children of higher than average intelligence may feel burdened by expectations to excel academically.[14] 

In contrast to this, children of less than average intelligence and those with learning difficulties may feel distressed that they cannot keep up with their peers. Many children with nonorganic functional hearing loss know people who are hard of hearing or may have suffered from hearing loss previously due to organic causes.[25][27] Signs of child abuse must be assessed in all children.[7] In adults, a history of financial troubles must be taken subtly; many malingerers will try to hide their financial difficulties.

An otological examination should include careful inspection of the pinna, external auditory canal, and tympanic membrane. Tympanic membranes are generally normal in patients with nonorganic functional hearing loss. Occasionally, findings such as dulling of the tympanic membrane, tympanic membrane retractions, wax, and healed tympanic membrane perforations may be seen. In these cases, although a pathology does exist, the hearing loss exhibited is far greater than what would be expected if the patient does have nonorganic functional hearing loss.[6][28][29] Cranial nerves may also be examined, although these are typically normal.

Evaluation

Lack of consistency in audiological testing is the mainstay of nonorganic functional hearing loss diagnosis.[12][13][21] Cross-checking objective and subjective audiological assessments allow for a reliable diagnosis of nonorganic functional hearing loss.[13][25][30] 

An objective audiological assessment is necessary to establish a diagnosis. In the nonorganic functional hearing loss, the objective audiological tests show significantly better hearing thresholds than what would be expected from the subjective audiological assessment.[31][32] The challenge in diagnosing nonorganic functional hearing loss lies in the fact that objective audiometry is not performed during routine physical examination.

Subjective audiological tests include tuning fork tests (Rinne and Weber tests), pure tone audiometry (PTA), and speech audiometry.

Rinne and Weber Tests

Rinne and Weber tests may not align with the results obtained with PTA testing; i.e., a sensorineural hearing loss type curve may be seen on PTA with Rinne and Weber tests' findings suggesting conductive hearing loss and vice versa.[26] 

Pure Tone Audiometry

The test-retest variability of hearing thresholds determined by PTA is often greater than expected in cases of nonorganic functional hearing loss. Variability in excess of 15 dB HL is highly suspicious for a nonorganic etiology.[33][34] PTA curves are usually flat or saucer-shaped and show hearing loss of sensorineural type in patients with nonorganic functional hearing loss.[35] 

The lack of a shadow curve in the PTA of the normal ear, in the case of unilateral hearing loss, and the lack of occasional false-positive button presses by the patient during PTA are suggestive of nonorganic functional hearing loss.[36] Encouraging behaviors and reassurance techniques during repeat PTA may be enough to significantly improve thresholds, making nonorganic functional hearing loss highly likely.[19] 

Diagnosis is usually easier in children as they are likely to produce consistently inaccurate results on repeated testing.[13] However, uncooperative children can make detection of nonorganic hearing loss with conventional audiological procedures difficult.[37] In addition, problems may arise when children do not understand what is expected of them during PTA due to a lack of familiarity with the testing procedure. More accurate results can be obtained by repeating PTA testing.[25]

Speech Audiometry

In cases of nonorganic functional hearing loss, speech audiometry usually shows better hearing thresholds than those predicted from PTA values.[38][39] Children are especially more likely to have good speech audiometry thresholds inconsistent with the degree of hearing loss shown on PTA; there should typically be less than a 5 to 8 dB difference between thresholds obtained by PTA and speech audiometry testing.[17] 

Objective audiological tests used to confirm the diagnosis of nonorganic functional hearing loss include auditory brainstem responses (ABR), otoacoustic emissions (OAE), and auditory steady-state responses (ASSR).[40][41] Stapedial reflexes are helpful in the evaluation of nonorganic functional hearing loss but are not diagnostic.[37] 

Auditory Brainstem Response

In ABR testing, five electrical waves are produced by signal transmission through different anatomical structures within the auditory pathway:[21]

• Waves I and II: proximal and distal cochlear nerve, respectively
• Wave III: second-order neurons near or in the cochlear nucleus
• Wave IV: third-order neurons near or in the superior olivary complex
• Wave V: termination of the lateral lemniscus in the inferior colliculus

The presence of these waves at normal auditory thresholds suggests that the corresponding structure is functioning adequately and, therefore, helps rule out organic pathology.

Otoacoustic Emissions

OAEs determine the integrity of the outer hair cells.[21] OAEs can be as reliable as ABRs while being relatively more convenient, inexpensive, and time-saving to test.[12][37] OAEs should not be performed in patients with otitis media with effusion. 

Other Audiological Tests

Auditory steady-state response (ASSR) is rarely used to diagnose nonorganic functional hearing loss.

Stapedial reflexes are generally elicited at values much higher than the threshold determined by PTA in cases of organic hearing loss. In the nonorganic functional hearing loss, stapedial reflexes are present within 10 dB of the patient's threshold or at values much lower than expected.[14][17]

The Stenger test is also used to help diagnose unilateral nonorganic functional hearing loss, but it is of limited usefulness in children.[42] The Stenger technique involves providing a test signal to both of the patient's ears simultaneously and at the same frequency but with a greater amplitude (volume) in the ear with suspected nonorganic hearing loss.

Because the auditory system is programmed to recognize only the louder of the two identical sounds, patients with nonorganic hearing loss will often fail to press the response button, while patients with organic unilateral hearing loss will still hear the sound in the normal ear and signal response. Other tests include the delayed auditory feedback speech test and Lombard reflex test.

Treatment / Management

After establishing the diagnosis of nonorganic functional hearing loss, management strategies range from observation to counseling and psychiatric intervention.[5] 

A few patients recover without any intervention; however, pursuing this tack without a thorough evaluation runs the risk of failing to recognize possible underlying psychiatric conditions, which may lead to a relapse or worsening of symptoms. Appropriate counseling includes highlighting the inconsistencies in audiological testing in a nonconfrontational manner. Explanation, reassurance, and encouragement are often effective techniques.[35][43] (B3)

The hearing loss should be acknowledged as real; the patient should not be held accountable for the hearing loss.[13][19] Confrontational interactions should be avoided, and the patient should receive reassurance of a high likelihood of recovery.[2][14][21] (B2)

Assessing which patients need psychiatric intervention and which patients do not is a clinical challenge. Psychiatric needs must be evaluated on an individual basis.[2] If there is a strong suspicion of underlying psychological conflicts, it is better that any behavioral health concerns be identified and addressed. [5][8][18] (B3)

Austen and Lynch suggest that the underlying need motivating the hearing loss must be elucidated and treated. This prevents the nonorganic hearing loss from returning or being converted to another nonorganic behavior.[2] Providing placebo medications may serve as positive reinforcement of the behavior and must be avoided.[11][21](B2)

Differential Diagnosis

The diagnosis of nonorganic functional hearing loss can only be made when other organic pathologies have been excluded. Subjective audiological testing usually reveals a pattern coherent with sensorineural hearing loss.

Causes of organic sensorineural hearing loss include:

• Noise exposure
• Trauma
• Infection
• Ménière disease
• Autoimmune disease
• Perilymph fistula
• Otosclerosis
• Genetically-inherited hearing loss
• Tumor
• Exposure to ototoxic agents
• Metabolic dysfunction[44]

As the onset of nonorganic functional hearing loss is often sudden, causes of sudden sensorineural hearing loss must also be excluded. Sudden sensorineural hearing loss can be due to ototoxicity, vascular occlusion, autoimmune diseases, viral infection, and even acoustic neuroma.

Auditory processing disorders, auditory neuropathy, and cortical auditory disorders should also be considered in the differential diagnosis.[21]

The diagnosis of nonorganic functional hearing loss is likely to be made when there is great variability in audiological test results, with objective audiological tests showing an absence of pathology in the auditory system. A history of recent psychological stress usually precedes the onset of symptoms. Inconsistent and suspicious behaviors during the examination may alert the clinician to suspect nonorganic functional hearing loss.

Prognosis

Nonorganic functional hearing loss has a generally good prognosis if the diagnosis is made and appropriate treatment is initiated. Spontaneous recovery has been noted in many studies.[20] 

However, in those patients with spontaneous recovery, relapse can occur in up to 25% of patients within a year. Factors indicating a better prognosis include prompt recognition, appropriate treatment, assessment of predisposing stress, and the absence of comorbid medical or psychiatric illness.[45]

Complications

The complications of nonorganic hearing loss arise most often due to misdiagnosis or delay in diagnosis. Unnecessary investigations, medical treatments, and even surgeries may result.[17] 

Enrollment of patients with nonorganic functional hearing loss in cochlear implant programs has been reported. In these cases, the actual cause of the hearing loss remains undiagnosed and leads to the prolongation of the patient’s suffering. Nonorganic functional hearing loss may present similarly to sudden sensorineural hearing loss. Given that an important treatment for sudden sensorineural hearing loss is systemic or intratympanic corticosteroids, nonorganic functional hearing loss should be ruled out before administering medications.[36] 

Steroids are not indicated in nonorganic functional hearing loss, and they may produce harmful side effects, particularly in children. In some cases, if nonorganic hearing loss is diagnosed but the underlying conflict is not resolved, later presentations of other nonorganic conditions such as visual disturbances may occur.[46]