Imaging of Temporal Bone Tumors

Imaging of Temporal Bone Mass Lesions: A Pictorial Review

Tumoral lesions of the temporal bone include benign or malignant tumors and congenital or inflammatory lesions. Temporal bone lesions are difficult to approach. Therefore, making a preoperative diagnosis and considering whether the lesions require treatment are necessary; if they require treatment, then the type of treatment requires consideration. These tumors cannot be observed directly and must be diagnosed based on symptoms and imaging findings. However, the differentiation of temporal bone lesions is difficult because they are rare and large in variety. In this pictorial review, we divided temporal bone lesions by location such as along the facial nerve, along the internal jugular vein, around the endolymphatic sac, in the internal auditory canal/cerebellopontine angle, petrous apex, middle ear, and mastoid, focusing on the imaging findings of temporal bone lesions. Then, we created a diagnostic flowchart that suggested that the systematic separation of imaging findings is useful for differentiation. Although it is necessary to make comprehensive judgments based on the clinical symptoms, patient background, and imaging findings to diagnose temporal bone mass lesions, capturing imaging features can be a useful differentiation method.

External auditory canal and middle ear tumors: characterization by morphology and diffusion features on CT and MRI

PURPOSE

To explore the value of morphology and diffusion features on CT and MRI in the characterization of external auditory canal and middle ear tumors (EAMETs).

METHODS

Forty-seven patients with histologically proved EAMETs (23 benign and 24 malignant) who underwent CT and MRI were retrospectively analyzed in this study. CT and MRI characteristics (including size, shape, signal intensity, border, enhancement degree, and bone changes) and apparent diffusion coefficient (ADC) value were analyzed and compared between benign and malignant EAMETs. Logistic regression, receiver operating characteristic (ROC) curve, and Delong test were performed to assess the diagnostic performance.

RESULTS

Compared with benign tumors, the malignant EAMETs are characterized by irregular shape, ill-defined border, invasive bone destruction, and intense enhancement (all p < 0.05). There were no significant differences on the size and signal intensity between benign and malignant tumors. The ADC value of malignant tumors were (879.96 ± 201.15) × 10^-6 mm²/s, which was significantly lower than benign ones (p < 0.05). Logistic regression demonstrates the presence of ill-defined margin, invasive bone destruction, and low ADC value (≤ 920.33 × 10^-6 mm²/s) have significant relationship with malignant EAMETs. The combination of characterization by morphology and diffusion features on CT and MRI can further improve the diagnostic efficiency when compared with morphology and diffusion features alone (both p < 0.05).

CONCLUSION

Some CT and MRI characteristics are helpful in identifying malignant EAMETs from benign ones (especially ill-defined margin, invasive bone destruction, and low ADC value), and the combination of morphology and diffusion features on CT and MRI has best diagnostic efficiency for discriminating these two entities.

Imaging the External Ear: Practical Approach to Normal and Pathologic Conditions

The external ear (EE) is an osseous-cartilaginous structure that extends from the auricle to the tympanic membrane. It is divided into two parts: the auricle (or pinna) and the external auditory canal (EAC). Given the ease of access to the EE, imaging studies are not always needed to make a diagnosis. However, when lesions block visual access to areas deep to the EE abnormality, complications are suspected, or there is lack of response to treatment, imaging becomes essential. A basic understanding of the embryologic development and knowledge of the anatomy of the auricle and EAC are useful for accurate diagnosis of EE lesions. Congenital, traumatic, inflammatory, neoplastic, and vascular conditions can affect the EE. An overview of the anatomy and embryologic development of the EE is presented, with discussion and illustrations of common and uncommon conditions that affect EE structures and a focus on the CT and MRI features that are of interest to radiologists. CT is usually the first diagnostic modality used to evaluate the EAC and is the superior method for demonstrating bone changes. MRI provides excellent tissue characterization and enables one to better define lesion extension and perineural tumor spread. In addition, a flowchart to facilitate the differential diagnosis of EE abnormalities is provided. Online supplemental material is available for this article. ^©RSNA, 2022.

Neuroendocrine adenoma of middle ear with new bone formation and review of literature

Neuroendocrine adenoma of the middle ear has been described in literature as middle ear adenoma with neuroendocrine differentiation or carcinoid tumor. While there have been several case reports describing imaging features of carcinoid tumors of the ear and middle ear adenomas, in our literature review, we have not found a single case where bone formation is described as a prominent radiological feature. We report a first documented case of middle ear carcinoid tumor with new bone formation demonstrated on CT imaging and performed a review literature regarding the tumor. A differential diagnosis of neuroendocrine adenoma of the middle ear should be considered when there is prominent bone formation with a soft tissue mass in the middle ear on CT imaging.

Temporal bone imaging

Temporal bone imaging is performed for a variety of clinical conditions addressed in the outpatient and acute care setting ranging from hearing loss to trauma. Recent advances in magnetic resonance technology have enhanced the assessment of fine anatomic temporal bone detail and improved the diagnostic sensitivity for important pathology. For example, non-echo planar diffusion weighted imaging increases detection rate and diagnostic confidence of recurrent cholesteatoma. This chapter will focus on relevant temporal bone clinical entities and new MR developments that have come into clinical practice.

Lesions in the external auditory canal

The external auditory canal is an S- shaped osseo-cartilaginous structure that extends from the auricle to the tympanic membrane. Congenital, inflammatory, neoplastic, and traumatic lesions can affect the EAC. High-resolution CT is well suited for the evaluation of the temporal bone, which has a complex anatomy with multiple small structures. In this study, we describe the various lesions affecting the EAC.