**1. Introduction**

Because individuals with unilateral hearing loss have normal hearing in the opposite ear, impairment of auditory communication is less severe than in those with bilateral hearing loss. Therefore, interventions for these patients may not always be indicated. Unilateral hearing loss that is profound is known as singlesided deafness (SSD). Patients with SSD suffer from impaired hearing of sounds coming from the deaf side, lack of sound localization, and deteriorated comprehension of speech in noisy environments. These disorders and related problems can affect academic performance in children. Kuppler et al. reviewed that some children with SSD have significantly decreased self-esteem and increased level of exhaustion and stress because of the effort required to hear, and the tenfold increase of incidence (35%) of poor performer will be estimated [1]. It was also inferred that SSD have adverse effects on quality of life (QOL) and social life of both children and adults.

The causes of unilateral hearing loss include congenital and acquired diseases. Diseases inducing acquired unilateral hearing loss include idiopathic sudden sensorineural hearing loss (ISSHL), Meniere's disease, mumps, vestibular schwannoma, otosclerosis, otitis media with effusion, chronic otitis media, and cholesteatoma, among others. Hearing loss caused by otosclerosis, chronic otitis media, and cholesteatoma can be improved by surgery, but inner ear damage resulting in SSD can rarely be reversed. Meniere's disease usually presents with mild-to-moderate hearing loss. Vestibular schwannoma presents with a wide range of hearing loss, from normal to total deafness, and if the tumor grows, surgical treatment is required, but the possibility of inducing SSD is relatively high after surgery. Though mumps is a disease that can acutely cause SSD, the incidence of hearing complications in mumps patients is quite low. ISSHL is quite a common condition, and it is estimated to produce the most patients with irreversible unilateral hearing loss.

Patients with ISSHL have an extremely dramatic clinical course in which unilateral hearing loss suddenly develops from normal hearing on both sides. In addition to the hearing-related problems that patients with congenital unilateral hearing loss or gradually worsening unilateral hearing loss face, there are other subsequent health issues that arise; therefore, ISSHL could be considered the most significant cause of acquired unilateral hearing loss. This chapter focuses on ISSHL as a representative condition that induces acquired unilateral hearing loss. First, the symptoms and health issues of patients with ISSHL based on the results of a nationwide survey of patients with ISSHL in Japan will be described. Next, the therapeutic interventions for patients with irreversible unilateral hearing loss caused by ISSHL will be considered.

## **2. Epidemiology and frequency of ISSHL**

ISSHL is the sudden or acute onset of sensorineural hearing loss of unknown origin. The hearing loss is unilateral in most cases with bilateral involvement reported in <5% of cases [2]. The lesion is most often cochlear in origin, and less frequently retrocochlear. Although the cause of ISSHL has not been identified, several pathogenic possibilities have been proposed, such as vascular disorders, viral infections, and membrane breaks. Many treatment regimens have been investigated, including corticosteroids, vasoactive drugs, antiviral drugs, and hyperbaric oxygenation therapy, but none have proven effective. ISSHL is expected to improve on its own or with treatment; however, hearing levels become fixed ~2 months from the onset, and if it is not cured by then, permanent hearing loss remains.

The incidence of ISSHL is reported to be 3-30 per 100,000 population per year [2], but a recent report in Japan reported 60 per 100,000 population per year [3]. According to the population of Japan, about 78,000 new cases occur annually. For the hearing performance of 1113 patients with ISSHL in the author's hospital during the past 20 years during the persistent phase after treatment, 35% were completely cured, 27% had mild hearing loss, 26% had moderate hearing loss, 8% had severe hearing loss, and 4% had profound to total deafness. When this is considered with the above-estimated incidence, it is estimated that 21,000 patients with mild hearing loss, 20,000 patients with moderate hearing loss, 6200 patients with severe hearing loss, and 3100 patients with profound hearing loss develop unilateral hearing loss each year in Japan. Although vestibular schwannoma is also a relatively common disease inducing SSD, the number of surgeries performed annually in Japan to remove the tumors is estimated to be approximately 700 [4, 5], considerably less than the number of patients with SSD caused by ISSHL.

### **3. Symptoms and QOL in patients with ISSHL**

Not many reports have investigated the symptoms or QOL in patients with ISSHL. Chiossoene-Kerdel et al. used the Hearing Handicap Inventory for Adults to

**5**

*Associated Health Issues of Patients with Acquired Unilateral Hearing Loss*

investigate the degree of handicap in patients with ISSHL [6], and most patients had a handicap associated with hearing loss and tinnitus. Carlsson et al. investigated QOL in patients with ISSHL using the EuroQoL-5D, Problems Impact Rating Scale, and the Hospital Anxiety and Depression Scale [7]. They reported that all three indicators were significantly influenced by the presence of tinnitus and vertigo. However, patients with Meniere's disease may have been included in that report, because the incidence of vertigo at the time of investigation was quite high (34%). Two main symptoms were reported to affect QOL in ISSHL patients with persistent hearing problems: difficulty in hearing and tinnitus [6, 7]. Unilateral hearing loss is a sudden change for patients who have never experienced hearing problems before the onset of ISSHL. Other problems, such as hearing-related discomfort and anxiety about recurrence, may also affect QOL. These problems may differ from those in

I and a few others conducted a multicenter clinical study by the Acute Profound Deafness Research Committee of the Ministry of Health, Labour and Welfare in Japan to investigate the symptoms and QOL in the patients with ISSHL in their

A total of 140 patients with ISSHL (64 males, 76 females; mean age 59.1 years; range 21–85 years) and 24 patients with congenital SSD (13 males, 11 females; mean age 30.5 years; range 20–77 years) were investigated to determine their symptoms. In the patients with ISSHL, hearing levels of the affected ear were widely distributed from normal to profound, with a peak distribution of 70 dBHL. The distribution of time intervals from the onset of hearing loss varied widely from 30 days to 62 years (mean 5.5 years; median 2.7 years). The majority of patients with congenital SSD (71%) were between 20 and 29 years of age [8]. A symptom questionnaire was newly created to assess the patients' symptoms. In a previous investigation, information on symptoms was elicited from 104 patients with ISSHL using a freewriting method. These symptoms were rewritten and organized to create a new questionnaire comprising 17 questions that covered seven categories: hearing difficulty (three questions), spatial hearing (two questions), hearingrelated discomfort (four questions), tinnitus (two questions), vertigo (one question), attitude to communications (two questions), and anxiety (three questions). We also asked patients with congenital SSD to answer the same questionnaire and compared the results with those patients with ISSHL [8]. The results of four major hearing-related symptoms, hearing difficulty, disability of spatial hearing, discomfort, and tinnitus, are shown in **Figure 1**. In response to questions regarding hearing difficulty, patients in both groups reported that they frequently had problems. With regard to the items "conversation with several people" and "conversation in noisy place," significantly more patients with ISSHL than with congenital SSD reported difficulty in hearing. In response to all questions regarding hearing-related discomfort, significantly more patients with ISSHL than with congenital SSD experienced symptoms. With respect to tinnitus, few patients with congenital SSD and many patients with ISSHL reported this symptom. In response to questions regarding

persistent phase [8, 9]. The results from that study are described below.

spatial hearing, no difference between the groups was identified.

The health-related QOL in the patients with ISSHL and congenital SSD was investigated using the short-form health survey version 2 (SF-36). SF-36 provides scores for eight health-related QOL domains and two more comprehensive scores: the physical component summary (PCS) and the mental component summary (MCS). The scores for the eight domains and the two component summaries were standardized (norm-based scoring, Japanese average of 50, standard deviation of 10) for comparison with the scores of people in the general population or those reported in other studies. When the average scores for the two summary components in patients with ISSHL and those with congenital

*DOI: http://dx.doi.org/10.5772/intechopen.88200*

patients with congenital SSD.

#### *Associated Health Issues of Patients with Acquired Unilateral Hearing Loss DOI: http://dx.doi.org/10.5772/intechopen.88200*

*Advances in Rehabilitation of Hearing Loss*

will be considered.

**2. Epidemiology and frequency of ISSHL**

number of patients with SSD caused by ISSHL.

**3. Symptoms and QOL in patients with ISSHL**

cholesteatoma can be improved by surgery, but inner ear damage resulting in SSD can rarely be reversed. Meniere's disease usually presents with mild-to-moderate hearing loss. Vestibular schwannoma presents with a wide range of hearing loss, from normal to total deafness, and if the tumor grows, surgical treatment is

required, but the possibility of inducing SSD is relatively high after surgery. Though mumps is a disease that can acutely cause SSD, the incidence of hearing complications in mumps patients is quite low. ISSHL is quite a common condition, and it is estimated to produce the most patients with irreversible unilateral hearing loss. Patients with ISSHL have an extremely dramatic clinical course in which unilateral hearing loss suddenly develops from normal hearing on both sides. In addition to the hearing-related problems that patients with congenital unilateral hearing loss or gradually worsening unilateral hearing loss face, there are other subsequent health issues that arise; therefore, ISSHL could be considered the most significant cause of acquired unilateral hearing loss. This chapter focuses on ISSHL as a representative condition that induces acquired unilateral hearing loss. First, the symptoms and health issues of patients with ISSHL based on the results of a nationwide survey of patients with ISSHL in Japan will be described. Next, the therapeutic interventions for patients with irreversible unilateral hearing loss caused by ISSHL

ISSHL is the sudden or acute onset of sensorineural hearing loss of unknown origin. The hearing loss is unilateral in most cases with bilateral involvement reported in <5% of cases [2]. The lesion is most often cochlear in origin, and less frequently retrocochlear. Although the cause of ISSHL has not been identified, several pathogenic possibilities have been proposed, such as vascular disorders, viral infections, and membrane breaks. Many treatment regimens have been investigated, including corticosteroids, vasoactive drugs, antiviral drugs, and hyperbaric oxygenation therapy, but none have proven effective. ISSHL is expected to improve on its own or with treatment; however, hearing levels become fixed ~2 months from

The incidence of ISSHL is reported to be 3-30 per 100,000 population per year [2], but a recent report in Japan reported 60 per 100,000 population per year [3]. According to the population of Japan, about 78,000 new cases occur annually. For the hearing performance of 1113 patients with ISSHL in the author's hospital during the past 20 years during the persistent phase after treatment, 35% were completely cured, 27% had mild hearing loss, 26% had moderate hearing loss, 8% had severe hearing loss, and 4% had profound to total deafness. When this is considered with the above-estimated incidence, it is estimated that 21,000 patients with mild hearing loss, 20,000 patients with moderate hearing loss, 6200 patients with severe hearing loss, and 3100 patients with profound hearing loss develop unilateral hearing loss each year in Japan. Although vestibular schwannoma is also a relatively common disease inducing SSD, the number of surgeries performed annually in Japan to remove the tumors is estimated to be approximately 700 [4, 5], considerably less than the

Not many reports have investigated the symptoms or QOL in patients with ISSHL. Chiossoene-Kerdel et al. used the Hearing Handicap Inventory for Adults to

the onset, and if it is not cured by then, permanent hearing loss remains.

**4**

investigate the degree of handicap in patients with ISSHL [6], and most patients had a handicap associated with hearing loss and tinnitus. Carlsson et al. investigated QOL in patients with ISSHL using the EuroQoL-5D, Problems Impact Rating Scale, and the Hospital Anxiety and Depression Scale [7]. They reported that all three indicators were significantly influenced by the presence of tinnitus and vertigo. However, patients with Meniere's disease may have been included in that report, because the incidence of vertigo at the time of investigation was quite high (34%). Two main symptoms were reported to affect QOL in ISSHL patients with persistent hearing problems: difficulty in hearing and tinnitus [6, 7]. Unilateral hearing loss is a sudden change for patients who have never experienced hearing problems before the onset of ISSHL. Other problems, such as hearing-related discomfort and anxiety about recurrence, may also affect QOL. These problems may differ from those in patients with congenital SSD.

I and a few others conducted a multicenter clinical study by the Acute Profound Deafness Research Committee of the Ministry of Health, Labour and Welfare in Japan to investigate the symptoms and QOL in the patients with ISSHL in their persistent phase [8, 9]. The results from that study are described below.

A total of 140 patients with ISSHL (64 males, 76 females; mean age 59.1 years; range 21–85 years) and 24 patients with congenital SSD (13 males, 11 females; mean age 30.5 years; range 20–77 years) were investigated to determine their symptoms. In the patients with ISSHL, hearing levels of the affected ear were widely distributed from normal to profound, with a peak distribution of 70 dBHL. The distribution of time intervals from the onset of hearing loss varied widely from 30 days to 62 years (mean 5.5 years; median 2.7 years). The majority of patients with congenital SSD (71%) were between 20 and 29 years of age [8]. A symptom questionnaire was newly created to assess the patients' symptoms. In a previous investigation, information on symptoms was elicited from 104 patients with ISSHL using a freewriting method. These symptoms were rewritten and organized to create a new questionnaire comprising 17 questions that covered seven categories: hearing difficulty (three questions), spatial hearing (two questions), hearingrelated discomfort (four questions), tinnitus (two questions), vertigo (one question), attitude to communications (two questions), and anxiety (three questions). We also asked patients with congenital SSD to answer the same questionnaire and compared the results with those patients with ISSHL [8]. The results of four major hearing-related symptoms, hearing difficulty, disability of spatial hearing, discomfort, and tinnitus, are shown in **Figure 1**. In response to questions regarding hearing difficulty, patients in both groups reported that they frequently had problems. With regard to the items "conversation with several people" and "conversation in noisy place," significantly more patients with ISSHL than with congenital SSD reported difficulty in hearing. In response to all questions regarding hearing-related discomfort, significantly more patients with ISSHL than with congenital SSD experienced symptoms. With respect to tinnitus, few patients with congenital SSD and many patients with ISSHL reported this symptom. In response to questions regarding spatial hearing, no difference between the groups was identified.

The health-related QOL in the patients with ISSHL and congenital SSD was investigated using the short-form health survey version 2 (SF-36). SF-36 provides scores for eight health-related QOL domains and two more comprehensive scores: the physical component summary (PCS) and the mental component summary (MCS). The scores for the eight domains and the two component summaries were standardized (norm-based scoring, Japanese average of 50, standard deviation of 10) for comparison with the scores of people in the general population or those reported in other studies. When the average scores for the two summary components in patients with ISSHL and those with congenital

#### **Figure 1.**

*Four major categories of symptoms reported by patients with ISSHL and congenital SSD. This figure was created from the results of Sano et al. [8]. "Hearing difficulty" consists of three items, "disability of spatial hearing" consists of two items, and "hearing-related discomfort" consists of four items in the questionnaire. P-values are presented as a comparison of the incidence between ISSHL and congenital SSD: \*p < 0.05, \*\*p < 0.01.*

SSD were compared with average Japanese scores matched by decade of age, the PCS scores in all age groups for both ISSHL and congenital SSD patients were not significantly different from the Japanese average scores, and MCS scores for patients in their 20s for both ISSHL and congenital SSD and in their 30s for ISSHL were not significantly different from Japanese average scores. However, the MCS scores for patients with ISSHL in their 40–70s were significantly lower than the age-matched average Japanese scores (**Figure 2**).

Next, multiple linear regression analysis was used to investigate confounders influencing MCS scores in patients with ISSHL. The effects of age, hearing level at the time of investigation, time from onset, and responses to three items of the symptom questionnaire (hearing difficulty in general, discomfort in noisy places, and tinnitus) were evaluated. Unexpectedly, the results showed that the response to the item of discomfort in noisy places was the sole significant confounder.

"Hearing-related discomfort" was not a particularly notable symptom before this study; therefore, we further investigated this finding. When the relationship between the response to the item "discomfort in noisy places" and the hearing level in the affected ear was investigated, the response was not associated with hearing level [8]. A high incidence of this symptom was reported by ISSHL patients with moderate to profound hearing loss in the affected ear. We can infer that people with moderate hearing loss feel discomfort from noise because they hear noisy sounds in the affected ear, which can be too loud as a result of recruitment phenomenon and can be distorted by impairment of frequency selectivity. But why do patients with profound hearing loss in their affected ear feel this discomfort? In the direct expression of the discomfort by the patients, some of them described it as "It feels very noisy because the noise around me spreads all over the space around me." We proposed that the reason for this symptom in patients with unilateral profound hearing loss was sudden loss of the ability to localize the sounds coming from various directions, and we called this condition "collapse of spatial hearing perception."

**7**

**Table 1.**

*Associated Health Issues of Patients with Acquired Unilateral Hearing Loss*

Individuals who had normal hearing in both ears before the onset of ISSHL suddenly lose the ability of spatial hearing, and they instantly begin and remain to feel discomfort in noisy environment. This symptom is important for understanding the

*group of ISSHL or congenital SSD and the age-matched Japanese average: \*p < 0.05, \*\*p < 0.01.*

*Mental component summary (MCS) scores of SF-36 in patients with ISSHL and congenital SSD. The graph was created using the data from Sano et al. [8]. "Japanese" indicates age-matched Japanese average scores. The results of 20s group of ISSHL and other than 20s groups of congenital SSD (CSSD) are not indicated because their numbers of patients were too small. P-values are presented as a comparison of scores between each age* 

**4. Therapeutic interventions for irreversible unilateral sensorineural** 

The degree of unilateral hearing loss caused by ISSHL varies from mild to profound, and the selection of interventions depends on the degree of hearing loss. The interventions for ISSHL patients with severe-to-profound hearing loss can be considered the same as those for SSD patients, which include cochlear implant (CI), bone-anchored hearing aids (BAHAs), and contralateral routing of signals (CROS)

Hearing difficulty Speech discrimination test SSQ/APHAB/GHABP

*SSQ, speech, spatial and qualities of hearing scale; APHAB, abbreviated profile of hearing aid benefit; GHABP,* 

Spatial hearing Sound localization SSQ

Discomfort Not available Not available Tinnitus Not available THI/VAS

*Glasgow hearing aid benefit profile; THI, tinnitus handicap inventory; VAS, visual analog scale.*

*Evaluation methods for four major problems in patients with ISSHL.*

**Objective evaluation Subjective evaluation**

As mentioned earlier, patients with ISSHL have several hearing-related symptoms, which can be divided into four categories: hearing difficulty, disability of spatial hearing, discomfort, and tinnitus. Hearing difficulty includes several situations, such as conversation with several people and speech perception in noise. The efficacy of therapeutic interventions for patients with ISSHL needs to be evaluated against those four categories. The available methods for evaluating those four

*DOI: http://dx.doi.org/10.5772/intechopen.88200*

QOL problems associated with ISSHL.

**Figure 2.**

**hearing loss caused by ISSHL**

categories are summarized in **Table 1**.

*Associated Health Issues of Patients with Acquired Unilateral Hearing Loss DOI: http://dx.doi.org/10.5772/intechopen.88200*

#### **Figure 2.**

*Advances in Rehabilitation of Hearing Loss*

SSD were compared with average Japanese scores matched by decade of age, the PCS scores in all age groups for both ISSHL and congenital SSD patients were not significantly different from the Japanese average scores, and MCS scores for patients in their 20s for both ISSHL and congenital SSD and in their 30s for ISSHL were not significantly different from Japanese average scores. However, the MCS scores for patients with ISSHL in their 40–70s were significantly lower

*Four major categories of symptoms reported by patients with ISSHL and congenital SSD. This figure was created from the results of Sano et al. [8]. "Hearing difficulty" consists of three items, "disability of spatial hearing" consists of two items, and "hearing-related discomfort" consists of four items in the questionnaire. P-values are presented as a comparison of the incidence between ISSHL and congenital SSD: \*p < 0.05,* 

Next, multiple linear regression analysis was used to investigate confounders influencing MCS scores in patients with ISSHL. The effects of age, hearing level at the time of investigation, time from onset, and responses to three items of the symptom questionnaire (hearing difficulty in general, discomfort in noisy places, and tinnitus) were evaluated. Unexpectedly, the results showed that the response to

"Hearing-related discomfort" was not a particularly notable symptom before this study; therefore, we further investigated this finding. When the relationship between the response to the item "discomfort in noisy places" and the hearing level in the affected ear was investigated, the response was not associated with hearing level [8]. A high incidence of this symptom was reported by ISSHL patients with moderate to profound hearing loss in the affected ear. We can infer that people with moderate hearing loss feel discomfort from noise because they hear noisy sounds in the affected ear, which can be too loud as a result of recruitment phenomenon and can be distorted by impairment of frequency selectivity. But why do patients with profound hearing loss in their affected ear feel this discomfort? In the direct expression of the discomfort by the patients, some of them described it as "It feels very noisy because the noise around me spreads all over the space around me." We proposed that the reason for this symptom in patients with unilateral profound hearing loss was sudden loss of the ability to localize the sounds coming from various directions, and we called this condition "collapse of spatial hearing perception."

the item of discomfort in noisy places was the sole significant confounder.

than the age-matched average Japanese scores (**Figure 2**).

**6**

**Figure 1.**

*\*\*p < 0.01.*

*Mental component summary (MCS) scores of SF-36 in patients with ISSHL and congenital SSD. The graph was created using the data from Sano et al. [8]. "Japanese" indicates age-matched Japanese average scores. The results of 20s group of ISSHL and other than 20s groups of congenital SSD (CSSD) are not indicated because their numbers of patients were too small. P-values are presented as a comparison of scores between each age group of ISSHL or congenital SSD and the age-matched Japanese average: \*p < 0.05, \*\*p < 0.01.*

Individuals who had normal hearing in both ears before the onset of ISSHL suddenly lose the ability of spatial hearing, and they instantly begin and remain to feel discomfort in noisy environment. This symptom is important for understanding the QOL problems associated with ISSHL.
