Role of imaging in chronic otitis media and its complications

Abstract

Chronic otitis media (COM) is a long-standing inflammatory condition affecting the middle ear and mastoid cavity, often resulting in progressive structural damage and functional deficits. Radiological imaging is fundamental in diagnosing the disease, assessing its severity, and identifying possible complications. The literature indicates that the prevalence rates of extracranial and intracranial complications range from 0.69% to 5%, while the mortality rate for intracranial complications is 26%. While magnetic resonance imaging is particularly useful in distinguishing soft tissue abnormalities and detecting intracranial extensions like meningitis, brain abscess, and sigmoid sinus thrombosis, high-resolution computed tomography remains the preferred modality for evaluating bony erosion, cholesteatoma, and mastoid involvement. Key complications such as ossicular chain destruction, facial nerve damage, and labyrinthine fistulae can be precisely identified using advanced imaging modalities, allowing for timely and effective surgical intervention. This minireview underscores the essential role of radiology in both diagnosing and managing COM, highlighting critical imaging findings that facilitate early detection and inform treatment decisions. A collaborative approach among radiologists, otolaryngologists, and infectious disease specialists is crucial for improving clinical outcomes in affected patients.

Key Words: Otomastoiditis; Intracranial complications; Temporal bone; Computed tomography; Magnetic resonance imaging; Diffusion-weight imaging

Core Tip: Chronic otitis media is a long-term inflammatory disease affecting the middle ear, which, if not properly managed, can result in both extracranial and intracranial complications. Magnetic resonance imaging is particularly valuable in assessing soft tissue involvement and distinguishing cholesteatomas from other inflammatory conditions, especially through the use of diffusion-weighted imaging (DWI). Recently, sensitivity of DWI in the diagnosis of cholestatoma was shown to be 88% and specificity of 96%. Meanwhile, high-resolution computed tomography remains the primary imaging modality for evaluating bony erosion, ossicular chain damage, and mastoid pathology, providing essential details for diagnosis and treatment planning.

INTRODUCTION

Chronic otitis media (COM) is a long-standing inflammatory condition of the middle ear and mastoid cavity, often arising from untreated acute otitis media. It is typically characterized by a perforated tympanic membrane, persistent ear discharge, and gradual hearing loss. If left untreated, COM may lead to severe complications, both extracranially and intracranially. Early diagnosis and timely intervention are crucial to preventing these outcomes[1]. COM and its complications are still an important cause of mortality and morbidity. The latest research reveals that the prevalence of extracranial and intracranial complications varies between 0.69% and 5%. The mortality rate in patients with complications is 16.1% and in patients with intracranial complications is 26.3%[2,3]. The morbidity rate in patients who developed complications was 11.8%[3]. COM persists as a significant worldwide health problem, being the primary cause of preventable hearing impairment in developing nations. Global epidemiological studies indicate that around 300 million individuals are afflicted by COM, with over 85% of cases arising in low-income nations[4].

Extracranial complications of COM include mastoid abscess, Bezold abscess, facial nerve palsy, and labyrinthitis. Intracranial complications include brain abscess, meningitis, lateral sinus thrombophlebitis and extradural abscess[2,3]. While brain abscess is the most common intracranial complication, mastoid abscess is the most common extracranial complication[5]. Incidence of most seen intracranial and extracranial complications of COM depicted in Table 1.

Table 1 Incidence of intracranial and extracranial complications of chronic otitis media.

Complication	Type	Incidence (%)1
Brain abscess	Intracranial	18-42
Meningitis	Intracranial	21-72
Lateral sinus thrombosis	Intracranial	2-26
Extradural abscess	Intracranial	7-16
Mastoid abscess	Extracranial	40-68
Facial nerve paralysis	Extracranial	13-58
Labyrinthitis	Extracranial	7-34
Bezold abscess	Extracranial	5-10

¹Data were obtained from Lin et al[2], Ahmad et al[3], and Penido Nde et al[5].

Radiological imaging is indispensable in the comprehensive assessment of COM. The use of high-resolution computed tomography (HRCT) for examining the temporal bone remains the preferred method for evaluating bony changes in patients with COM[5,6]. HRCT is particularly effective in detecting bony erosions, cholesteatomas, scutum defects, and mastoid involvement, all of which play a significant role in surgical planning. Several studies emphasize the diagnostic value of HRCT in identifying cholesteatomas and assessing the extent of bony damage, which is critical for determining appropriate surgical interventions[6,7]. On the other hand, magnetic resonance imaging (MRI) is essential for evaluating soft tissue abnormalities and detecting complications extending to the intracranial space, such as brain abscesses and meningitis. Among its various techniques, diffusion-weighted imaging (DWI) stands out for its ability to differentiate cholesteatomas from other inflammatory or post-surgical changes. MRI also offers superior resolution for assessing facial nerve involvement and labyrinthine conditions, which are critical factors in treatment decisions. The combination of DWI and MRI with conventional computed tomography has been shown to significantly enhance diagnostic accuracy in cases of COM and its complications[8]. The pathophysiology of COM involves chronic bacterial infection, biofilm formation, and dysfunction of the Eustachian tube, all contributing to progressive tissue destruction. Complications, including ossicular chain erosion, labyrinthine fistulae, and facial nerve damage, can be precisely identified through HRCT and MRI. Early detection of these complications is essential for prompt intervention, ultimately improving patient outcomes[9].

ROLE OF HRCT IN DIAGNOSING COM AND ITS COMPLICATIONS

If left untreated, COM can lead to severe complications, including both extracranial and intracranial sequelae. Early diagnosis and intervention are crucial to prevent these adverse outcomes[6]. HRCT of the temporal bone is considered the gold standard for evaluating bony structures in patients with COM. It effectively detects ossicular chain erosion, cholesteatoma, scutum defects, and mastoid involvement, providing vital information for surgical planning. HRCT is particularly useful in identifying cholesteatoma and other bony abnormalities associated with COM[7]. Additionally, HRCT aids in assessing the extent of disease involvement, which is essential for determining the appropriate surgical approach. By providing detailed imaging of the temporal bone, HRCT enables clinicians to plan surgeries more effectively, potentially improving patient outcomes[10]. HRCT is instrumental in identifying complications such as mastoiditis, labyrinthitis, and facial nerve involvement. It can detect complications like facial nerve erosion and labyrinthine fistulae, which are critical for surgical planning[11]. While HRCT provides detailed bony imaging, it has limitations in assessing soft tissue involvement and intracranial complications. Therefore, combining HRCT with other imaging modalities, such as MRI, can offer a more comprehensive evaluation[12]. The HRCT protocol, thin sections (usually 0.625 to 1.25 mm) should be taken and the generation of images should be performed using a sharp algorithm (e.g. bone algorithm). HRCT plays a pivotal role in the diagnosis and management of COM, offering detailed insights into bony structures and facilitating informed surgical decisions. Its ability to detect complications and assess the extent of disease involvement makes it an indispensable tool in the clinical evaluation of COM[10-12].

ROLE OF MRI IN DIAGNOSING COM AND ITS COMPLICATIONS

MRI has become a pivotal tool in evaluating soft tissue involvement in COM and detecting intracranial complications that may arise due to the disease. Unlike HRCT, which focuses on bony structures, MRI is particularly effective in assessing soft tissue changes, such as cholesteatoma and inflammation[8,12]. MRI, especially with the use of DWI, plays a crucial role in distinguishing between benign and malignant forms of cholesteatoma, which is critical for appropriate management[13]. The high sensitivity of DWI allows for the detection of cholesteatoma with great accuracy, even in cases where it might not be apparent on HRCT scans[12,13]. Additionally, MRI is indispensable for detecting intracranial complications, including brain abscesses, meningitis, and sigmoid sinus thrombosis, which can arise due to the spread of infection from the middle ear[14]. For patients with COM, MRI also assists in evaluating facial nerve involvement, labyrinthine fistulae, and ossicular chain erosion[15]. MRI can provide a comprehensive overview of both soft tissue and bony structures, allowing clinicians to assess the extent of disease and plan surgical interventions accordingly. This multidimensional capability of MRI helps in both preoperative planning and in monitoring post-treatment outcomes[12]. The signal-to-noise ratio of images obtained using multi-channel phased array coils is significantly improved. MRI offers significant advantages in diagnosing and managing COM and its complications. Its ability to assess soft tissue structures, detect cholesteatomas, and identify intracranial and extracranial complications makes it an essential modality in the comprehensive management of this condition[12-15].

ROLE OF COMBINED IMAGING APPROACH IN DIAGNOSING COM AND ITS COMPLICATIONS

In routine practice, the majority of centers employ a multimodal imaging strategy for diagnosing complications of COM. HRCT excels in evaluating the condition of the ossicular chain, mastoid ventilation, and bone degradation, whereas diffusion-weighted MRI sequences are particularly adept at distinguishing soft tissue lesions like cholesteatoma. A combined imaging technique integrates the advantages of both modalities to enhance diagnostic precision. As a result, the rationale for surgical planning is established with greater confidence. Unnecessary operations are prevented. The combined method yields significant success, particularly in identifying recurrent or persistent cholesteatomas. The integration of HRCT and MRI for the early detection and appropriate therapy of COM and its consequences is a crucial diagnostic approach in modern otological practice[12,16].

Figure 1 shows otomastoiditis and cholesteatoma in the right mastoid cells and middle ear cavity on contrast-enhanced temporal MRI of a 27-year-old male. Additionally, Figure 2 shows intracranial abscess, meningitis and subcutaneous abscess detected in the MRI examination of the same patient. Figure 3 shows findings consistent with labyrinthitis on T2W temporal MRI in a 38-year-old male patient diagnosed with COM. Figure 4 shows MRI of a 43-year-old female patient with COM showing findings of lateral sinus thrombosis extending to the sigmoid sinus.

Figure 1 Otomastoiditis and accompanying cholesteatoma. A: The axial pre-contrast T1W; B: Post-contrast T1W; C: 3D-constructive interference in a steady state MR images show hyper-enhanced inflammatory alterations in the mastoid cells and middle ear on the right side (orange arrows); D: The axial diffusion-weighted; E: Apparent diffusion coefficient map; F: Coronal post-contrast T1W magnetic resonance images show the presence of cholesteatoma in the right inferior mastoid cells, which was not enhanced, but had significant diffusion restriction (blue arrows).

Figure 2 Meningitis with subcutaneous and intracranial abscess. A: The axial post-contrast T1W; B: Coronal post-contrast T1W; C: Axial post-contrast T1W; D: Axial diffusion-weighted; E: Apparent diffusion coefficient map; F: Coronal post-contrast T1W magnetic resonance images show abscesses in the subcutaneous adipose tissue (yellow asterisks) and intracranial (orange arrows) area with a thick and hyperenhanced wall and centrally restricted diffusion. The axial post-contrast T1W and coronal post-contrast T1W magnetic resonance images show meningeal enhancement compatible with meningitis in the right parietotemporal area (yellow arrows).

Figure 3 Labyrinthitis. A: The axial 3D-constructive interference in a steady state (CISS) magnetic resonance image showing focal signal loss in the vestibule (orange arrow) on right side; B: The axial 3D-CISS magnetic resonance image showing focal signal loss in the horizontal semicircular canal (orange arrow) on left side.

Figure 4 Lateral sinus thrombosis. A: The coronal post-contrast T1W cerebral magnetic resonance venography image shows loss of signal along the right transverse sinus (orange arrow); B: The coronal post-contrast T1W cerebral magnetic resonance venography image shows loss of signal along the right sigmoid sinus (blue arrow); C: The coronal T2W magnetic resonance image shows hyperintensity due to flow void loss in the right transverse sinus (green arrow); D: Axial T2W magnetic resonance image shows hyperintensity due to flow void loss in the right sigmoid sinus (yellow arrow).

CONCLUSION

COM and its complications pose significant challenges in both diagnosis and management, necessitating precise imaging techniques to ensure timely intervention. HRCT remains the preferred modality for evaluating bony erosion, mastoid involvement, and ossicular chain destruction, providing essential details for surgical planning. Meanwhile, MRI plays a crucial role in differentiating soft tissue abnormalities, particularly in distinguishing cholesteatomas from other inflammatory lesions, as well as identifying extracranial and intracranial complications. Early detection of these complications is vital in preventing severe morbidities, including hearing loss, facial nerve paralysis, and life-threatening infections such as meningitis and brain abscess. The integration of advanced imaging techniques, such as improved DWI sequences (e.g., RESOLVE DWI), holds promise for further increasing diagnostic accuracy, reducing the need for unnecessary surgical interventions, and improving patient outcomes. As research continues to refine imaging protocols and enhance the sensitivity and specificity of radiological tools, the role of HRCT and MRI in the evaluation of COM is expected to become even more precise and indispensable. Future studies should focus on optimizing imaging methodologies to facilitate earlier diagnosis, better disease characterization, and more effective treatment planning, ultimately minimizing complications and improving the quality of life for affected individuals.

Finally, we recommend routine HRCT in all suspected unsafe CSOM cases and reserved MRI for suspected intracranial spread.