The Correlation Between Petrous Part of the Temporal Bone Density and the Internal Auditory Canal Diameter in Sensorineural Hearing Loss Patients with Chronic Renal Failure

Abstract

Patients with chronic renal failure often suffer from hearing loss and the most common cause is sensorineural hearing loss. Sensorineural hearing loss can be caused by cochlear otosclerosis with early symptoms such as decreased petrous part of the temporal bone density due to narrowing of the internal auditory canal. Finding a correlation between the petrous part of the temporal bone density and the anteroposterior diameter of the internal auditory canal in sensorineural hearing loss in patients with chronic renal failure. An observational analytic, cross-sectional study, using a consecutive sampling technique. The petrous part of the temporal bone density decreased in patients with chronic renal failure. The anteroposterior diameter of the internal auditory canal remained normal, there was no association with sensorineural loss. There is a significant correlation between the petrous part of the temporal bone density and sensorineural hearing loss in patients with chronic renal failure. High-resolution CT scans of the mastoid can assist clinicians in determining cochlear otosclerosis and the subsequent detection of the early presence of sensorineural hearing loss.

Introduction

Hearing loss can degrade the quality of life of a patient [1]. In the last few years, it has been determined that there is a relationship between chronic renal failure and the incidence of sensorineural hearing loss. Chronic renal failure is a global health concern with increasing incidence and prevalence [2–5]. In patients with renal failure, uremia, which causes disturbances in almost every organ system in the human body, may occur [3–7]. Hearing loss is found in 45–75% of patients with chronic renal failure, which is a significant number compared to the general population. Cochlea lesions are the suspected cause of sensorineural hearing loss [6]. Computed tomography scan examinations show bone remodeling as a result of bone and mineral metabolism disorders [7] and the narrowing of the internal auditory canal [8, 9]. To date, there has been no research linking the two with the occurrence of a sensorineural hearing loss in patients with chronic stage III and IV renal failure stage. It is expected that this research could serve as a methodology and tool to diagnose early sensorineural hearing loss in patients with renal failure stage III and IV renal failure.

Audiometry is a diagnostic tool for hearing loss, it is semi-objective and not all health centers have this capability. It is different from CT scan, which is objective and owned by almost all health centers. Radiological examination is performed to assist clinicians in diagnosis, therapy, and prognosis of a patient. Essentially all of the organs in the human body can be examined using CT scans. In the case of patients with sensorineural hearing loss, high-resolution CT scans of the mastoid are performed, and the petrous part of the temporal bone density assessed, namely Hounsfield Unit (HU) value to determine the anteroposterior diameter of the internal auditory canal [7, 10–12].

This study is part of a major research effort examining the levels of vitamin D in patients with stage III and IV renal failure that experience sensorineural hearing loss.

Research Purpose

This research aims to analyze the correlation between the petrous part of the temporal bone and the anteroposterior diameter of the internal auditory canal in patients with sensorineural hearing loss who suffer from chronic stage III and IV renal failure.

Research Design

This was an observational analytic cross-sectional approach conducted on 26 patients with chronic stage III and IV renal failure. The study passed an ethics assessment in Saiful Anwar General Hospital Malang.

• Inclusion Criteria Patients with chronic stage III and IV renal failure that were diagnosed with sensorineural hearing loss in the audiometric examination, aged between 19 and 65 years old and were willing to participate in the study.

• Exclusion Criteria Patients with abnormal ear anatomy, patients with trauma, ear infections, congenital hearing loss/hearing loss at birth and the presence of disease in the outer and middle ear that could lead to permanent hearing loss as determined by otoscopy and audio-tympanometry examination.

Statistical Analysis

All data obtained from the research results were recorded in a special research book (log book) and stored as computer files. Data of patient characteristics were analyzed using descriptive statistics and presented in the form of frequency distribution tables and central tendency [mean value ± SD, med (min–max)], and analyzed using Pearson’s test. If data distribution was not normal, Spearman’s test was carried out (Tables 1, 2).

Table 1.

Table and central tendency of research sample

Variables	Mean	SD	Median	Minimum	Maximum
ROI1 dextra	2004	361	2018	1197	2500
ROI2 dextra	1998	309	2011	1568	3147
Diameter of internal auditory canal dextra	4.3	0.6	4.3	2.9	5.6
Audiometry dextra	30	9.4	27.85	11.25	90
ROI1 sinistra	2008	313	2007	1417	2616
ROI2 sinistra	1952	235	1914	1484	2394
Diameter of internal auditory canal sinistra	5.6	6.4	4.4	2.8	5.7
Audiometry sinistra	30	9.4	27	16.25	57.50
Age	57	9.2	55	25	64

Table 2.

Table of Pearson and Spearman correlation

Correlation	p	r
ROI 1 dextra—audiometry dextra	0.035 (b)*	− .362
ROI 2 dextra—audiometry dextra	0.002 (b)*	− .542
Anteroposterior diameter of internal auditory canal dextra—Audiometry dextra	0.409 (b)	.048
ROI 1 sinistra—audiometry sinistra	0.006 (a)*	− .489
ROI 2 sinistra—audiometry sinistra	0.055 (a)*	− .321
Anteroposterior diameter of internal auditory canal sinistra—audiometry sinistra	0.162 (a)	.201

Description of the table. Pearson Test (a). Spearman test (b). Statistically significant correlation, if the value is p < 0.05 (*). 0–0.2 very weak. > 0.2–0.4 weak, > 0.4–0.6 moderate, > 0.6–0.8 strong and > 0.8 very strong

Results

Sampling of the temporal bone of pars petrosa density using high-resolution CT scan of the mastoid of 26 patients were used in this study from June 2016 to September 2016 in the Radiology division of Dr. Saiful Anwar General Hospital Malang. The results show that 17 patients were diagnosed with sensorineural hearing loss, while the rest were normal. Descriptive statistical analyses were then performed and presented in tabular form with averages [mean value ± SD, med (min–max)].

The average age was 52 years (± 9 years), minimum age 25 years and maximum age of the sample was 64 years old. The highest average bone density value was 2008 HU ± 313 (ROI1 sinistra), the minimum value and the highest mean were 1197 HU and 2018 HU (ROI1 dextra), while the highest maximum value was 3147 HU (ROI2 dextra). The average result for the audiometric dextra sinistra test was 30 dB, with a minimum value of 11.25 dB and a maximum of 90 dB. The average and the highest median of the diameter of internal auditory canal sinistra was 5.6 mm (± 4.4) and 2.8 mm. The largest diameter was 5.6 mm for internal auditory canal dextra. There was a significant correlation between ROI1 dextra and audiometry dextra with a weak relationship, while ROI2 dextra and audiometry dextra had a significant correlation with a moderate relationship. A significant relationship occurs when the audiometry has high value and the bone density value is low. There was no correlation between the anteroposterior diameter of the internal auditory canal dextra and the audiometry dextra.

There was a significant correlation between ROI1 sinistra and audiometry sinistra with a moderate relationship, while ROI2 sinistra and audiometry sinister had a significant correlation with a weak relationship. A significant relationship occurs when the audiometry has high value, thus the bone density value is low. There was no correlation between the anteroposterior diameter of the internal auditory canal sinistra and audiometry sinistra, which had a weak relationship. A negative correlation is defined here as the inverse relationship between one variable and another.

Discussion

The ear is divided into the outer ear, the middle ear and the inner ear: The outer ear consists of two parts: the auricle and the ear canal up to the tympanic membrane. The auricle is composed of cartilage and skin. The ear canal is S-shaped and formed from cartilage on one-third of the outer region while two-thirds of the inner skeleton are composed of bone [13]. The middle ear is located inside the air-filled cavity in the petrous part of the temporal bone. The tympanic membrane is the boundary between the outer ear and the inner ear. The ossicles are three bones: the malleus, incus, and stapes. These bones transmit the vibration of the tympanic membrane to the vestibule, which separates the middle ear from the inner ear [11–16]. The inner ear consists of two parts: the vestibular system (dedicated to balance) and the cochlea (dedicated to hearing). The inner ear is located within the petrous part of the temporal bone and is commonly called the labyrinth because of its’ complex structure. At birth, the shape of the inner ear is already perfect, it only enlarges in size along with the growth of the temporal bone. The inner ear consists of two parts: bony labyrinth and membranous labyrinth [11–17].

There are several types of hearing loss. If there is damage in the outer ear or middle ear inhibiting sound wave transmission and vibration of the fluid in the inner ear, there will be conductive hearing loss [14]. Mixed hearing loss is a combination of conductive and sensorineural hearing loss. In sensorineural hearing loss sound, waves can be transmitted to the inner ear, but they are not translated into nerve signals, which are then interpreted by the brain. Sensorineural hearing loss is usually caused by damage or lesions in the organ of Corti [14]. Based on the location of the lesion, sensorineural hearing loss is divided into sensorineural cochlea hearing loss and retrocochlear hearing loss [15].

Chronic renal failure is a pathophysiological process with different causes, which will result in a progressive decline in renal function and generally ends with a clinical condition characterized by an irreversible decline in kidney. Circumstances, it requires dialysis or kidney transplantation [16].

The Relationship Between Sensorineural Hearing Loss and Chronic Renal Failure

As many as 45–75% of patients with the chronic renal failure experience sensorineural hearing loss. Several studies using audiometry and kidney function tests on 2564 patients conducted in 1997–2004 gave the result that glomerular filtration rate (GFR) < 60 mL/min/1.73 m² is an independent risk factor for the occurrence of hearing loss [6]. In patients with renal failure, the cochlea is the predominantly affected part of the auditory system. Research in animals that are subjected to acute kidney injury, shows that the cochlea is the location of the lesion causing sensorineural hearing loss in these animals [15, 16].

Erkoç et al. [7] suspects that bone remodeling occurred in the petrous part of the temporal bone as a cause of sensorineural hearing loss in patients with chronic renal failure. Erkoc’s research reports that the density of the petrous part of the temporal bone in patients with sensorineural hearing loss and chronic renal failure is lower than that of the control population, especially in a 1 mm area in the anterior foramen ovale and 1 mm in the anterior of the internal auditory canal. Erkoc states that the normal HU value of the petrous part of the temporal bone is around 1909 ± 54 HU in axial sections [7, 17, 18]. LFG decreases cause phosphate retention that stimulates the synthesis of FGF23 and parathyroid hormone. Increased FGF23 lowers the production of vitamin D, which causes bone remodeling, a response to the secondary hyperparathyroidism in the form of reduced bone mineral density and bone resorption.

Density in Hounsfield Units (HU)

Density is a measure of the concentration of a substance expressed in the number of molecules (mass) per unit volume. Conventional X-ray tubes rotate physically in a circular shape, but in electron beam tomography (EBT) the flow of electrons rotates. The generated data will show the density of various layers. When X-rays pass through a layer, the layer will absorb light and the unabsorbed particles will pass through the layer to be captured by a detector that is sensitive to electrons [19]. In this research, high-resolution CT scan of the mastoid was performed. The radiation dose received by the patient during CT is 0.66 mSv [20]. On average each person receives a dose of 2.8 mSv (280 mrem) per year, meaning study participants would only receive about half of the safe dose limit [19].

Of the 26 patients in this study, 17 were diagnosed with sensorineural hearing loss and nine patients were normal. This is consistent with previous research showing that the incidence of sensorineural hearing loss in patients with chronic renal failure is equal to 45–75% [6].

There was a weak correlation with the weak–moderate level of confidence between the petrous part of the temporal bone density and the audiometric value. This is consistent a relationship between the petrous part of the temporal bone density and audiometric values, especially in patients with chronic renal failure. The lower the ROI1 and ROI2 sinistra values, the higher the hearing threshold upon audiometric examination of these patients (normal ≤ 25 dB). This is consistent with the theory that early signs of sensorineural hearing loss are characterized by a decrease in the density of the petrous part of the temporal bone, and not a cause of sensorineural hearing loss itself. Sensorineural hearing loss usually occurs in patients with chronic renal failure [1]. The relationship identified in this study is weak–moderate and it is very likely to due to the small sample size in this study (Figs. 1, 2, 3).

Fig. 1.

High-resolution CT scan of mastoid, axial cut. A decrease in the density of pars petrosa of temporal bone on 2 ROI

Fig. 2.

High-resolution CT scan of mastoid, axial cut. Measuring the anteroposterior diameter of internal auditory canal

Fig. 3.

Classification of cochlear otosclerosis in radiology. High-resolution axial CT scan of mastoid (axial cut) of a patient with cochlear otosclerosis [9]

The earliest radiological sign of sensorineural hearing loss in patients with chronic renal failure is a decrease in the petrous part of the temporal bone density, called cochlear otosclerosis (cochlear otospongiosis). Cochlear otosclerosis is a unique condition in the temporal bone, characterized by bone resorption and abnormal deposition of the petrous part of the temporal bone and ossicles. The radiological examination can help diagnose cochlear otosclerosis, but it is not sensitive enough to diagnose the inactive state because the radiological images will appear normal [20]. Cochlear otosclerosis is different from clinical otosclerosis [1, 7]. In CT scans, the presence of a pericochlear hypodense double ring shows demineralization of the petrous part of the temporal bone and it usually occurs in patients with cochlear otosclerosis. There are three stages of cochlear otosclerosis, stage 1 is the most moderate and stage 3 is the most severe. The CT scan will show hypodense lesions in the cochlea [18, 19]. Lee divides cochlear otosclerosis into several grades based on high-resolution CT scans of the mastoid namely Grade 0: normal. Grade 1: punctate hypodense lesion on fistula ante fenestram. Grade 2A: the presence of sclerotic and narrowing of basal turn. Grade 2B: hypodense lesion in the middle turn cochlea. Grade 2C: hypodense lesion around the lateral aspect of basal, middle, apical turns of the cochlea. Grade 3: Advanced and visible phase of hypodense lesions in the cochlea [9].

The narrowing of the internal auditory canal is a rare condition, often accompanied by a variety of other disorders such as temporal bone malformations and systemic disorders (cardiac, renal). The incidence is small, about 9% of all congenital abnormalities of temporal bone, and it is usually unilateral. There are two hypotheses to explain the relationship between the narrowing of the internal auditory canal and sensorineural hearing loss. The first occurs when the embryonic cochlea and vestibule, which induces the growth of N. 8 and the bones around the internal auditory canal, develop around N. 8 and N. 7 through the process of mesoderm bone formation at 8 weeks of gestation. When N. 8 disturbances such as hypoplasia or aplasia occur, it is usually accompanied by a narrowing of the internal auditory canal. Another hypothesis states that there is a primary defect of the bone, thus inhibiting the transmission of N. 8. High-resolution CT scan of the mastoid are useful in assessing the internal auditory canal but have limitations in assessing nerve structures contained in the internal auditory canal. MRI has superiority in assessing nerve structures. The above theory supports the hypothesis that the narrowing of the internal auditory canal is a congenital abnormality, not due to degenerative and metabolic diseases [1, 7, 9].

Conclusions

1. There is a significant correlation with weak–moderate confidence level between the petrous part of the temporal bone density and sensorineural hearing loss in patients with chronic renal failure.

2. There is no correlation with a weak–moderate confidence level between the diameter of the internal auditory canal and sensorineural hearing loss in patients with chronic renal failure.

3. High-resolution CT scans of the mastoid can assist clinicians in determining cochlear otosclerosis and the subsequent detection of the early presence of sensorineural hearing loss.

Funding

This work was supported by grants from Saiful Anwar General Hospital Malang, Indonesia (Grant No. 2016).

Compliance with Ethical Standards

Conflict of interest

The authors declare that there is no conflict of interests regarding the publication of this paper.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.