Metastasis to the External Auditory Canal: A Systematic Review.

Objective: To systematically review the literature and understand the behavior, diagnosis, management, and mortality of metastasis to the external auditory canal (EAC).

Databases reviewed: PubMed/Medline, EMBASE, Web of Science.

Methods: Studies from 1948 to June 2023 describing metastasis to the EAC were included. Non-English literature was excluded. Data extraction: Study design, age, sex, pathology, primary site, staging, additional sites of metastasis, time to EAC metastasis from diagnosis, time from diagnosis of EAC metastasis to death, symptoms, exam and imaging findings, and management.

Results: Data were synthesized qualitatively with means calculated. Thirty-two studies met the criteria, totaling 37 patients with EAC metastasis. Mean age was 58 years; 73% were male. The most common pathologies were adenocarcinoma (37.8%), acute myelogenous leukemia (8.1%), and renal cell carcinoma (8.1%). Sites of primary malignancy were hematologic (10.8%), breast (8.1%), esophagus (8.1%), renal (8.1%), and prostate (8.1%). Within the temporal bone, 73% had isolated EAC metastasis. Median time to EAC metastasis from the diagnosis of primary malignancy was 18 months. Metastasis to the EAC was the first presentation of malignancy in 21.6% of patients. Median time to death was 4.5 months. Symptoms included hearing loss (59.5%), otalgia (27.0%), otorrhagia (24.3%), facial paralysis (21.6%), otorrhea (16.2%), and aural fullness (13.5%). On imaging, bony erosion was present in 50% of cases. Treatment was primarily palliative with excision and radiation.

Conclusions: EAC metastasis has a distinct presentation from other temporal bone subsites. Early biopsy to establish a diagnosis and intervene is critical.