Colon Cancer Metastasis to the Lateral Skull Base Masquerading as Mastoiditis

Background: Tumor metastasis to the lateral skull base can occur as a late-stage complication of an aggressive malignancy. Prostate, lung, and breast cancer are most commonly identified in this setting, and in many cases, metastasis is preceded by distant spread of disease to other locations. The present report describes a case of colon adenocarcinoma metastatic to the lateral skull base at the transverse-sigmoid junction.

Case Presentation: A 72-year-old Caucasian woman presented to our institution with 5 days of progressively altered mental status. Her history was notable for colon cancer status-post resection and chemotherapy 7 years prior, as well as a left middle cerebral artery aneurysm status-post surgical clipping 4 months prior. On the day of admission, she had a tonic-clonic seizure and was brought to the Intensive Care Unit for further evaluation. At the time of her presentation, she was found to be combative and disoriented. On exam, there was no erythema or fluctuance of the periauricular skin, though there was slight edema and tenderness in the postauricular area on the left. Otoscopy revealed serous appearing fluid in the middle ear on the left. The white blood cell count was 9,200/microliter with 70% neutrophils. C-reactive protein was elevated at 3.55 mg/dL. Electroencephalogram demonstrated an epileptic focus in the left temporal lobe with focal slowing of rhythms in the left cerebellar hemisphere. Computed tomography of the left temporal bone demonstrated complete opacification of the mastoid air cells on the left with associated tegmen tympani erosion. Contrast-enhanced MRI demonstrated an irregular and enhancing extra-axial lesion that involved the transverse-sigmoid sinus junction with thrombosis extending proximally and distally. Asymmetric left dural enhancement and temporal lobe edema were identified. The imaging studies were interpreted by Neuroradiology as a possible intracranial complication of otomastoiditis. The patient was taken to the operating room where a left-sided occipital craniotomy and mastoidectomy were performed. A transdural mass was found to be eroding through the tegmen, invading the transverse-sigmoid junction, and compressing the cortex of the temporal lobe. Frozen section analysis demonstrated intestinal type adenocarcinoma. Restaging and treatment planning is currently ongoing.

Conclusion: Though metastases to the skull base are not as common as benign neoplasms or infectious processes, they are not necessarily rare and should be considered in the setting of previously treated systemic malignancy. As was seen in the present case, lesions that spread hematogenously frequently involve relatively vascular areas of the skull base.