Skull Base Infections: Pearls and Pitfalls

Objective: Infections of the skull base are uncommon and their course can range from insidious to aggressive. Undiagnosed or untreated patients can suffer from detrimental long-term effects. The etiology of these infections can come from a variety of sources especially affecting the immunocompromised, the elderly, or diabetics; making imaging pivotal in diagnosis and management. However, radiologic findings are often subtle requiring high index of suspicion and detailed inspection.

Purpose: Early diagnosis of skull base infections can significantly alter patients’ morbidity, mortality and lower the risk for subsequent complications. The purpose of this abstract is to review anatomy and imaging characteristics of different skull base infections.

Method: A retrospective search was performed of the radiology database for studies conducted between 2010 and 2021 at MedStar and associate network sites using the Nuance mPower search engine. Both CT and MRI images, as well as clinical documents were reviewed.

Results: Several imaging modalities can be used to determine diagnosis. Non-contrast CT is best for evaluating osseous changes such as demineralization or erosion and often used as a first step in evaluation. Contrast-enhanced CT is utilized for evaluation of soft tissue swelling and vascular complications. MRI is best for evaluating extend of disease such as intracranial and soft tissue involvement. Repeat imaging is useful for follow up or treatment response evaluation. Characteristics of imaging and anatomic location may help in establishing a differential diagnosis, which then dictates management.

Conclusion: Given the subtle and nonspecific signs and symptoms of skull base infections, it is important to be aware of critical imaging findings that can alert the skull base surgeon of aggressive processes that need prompt attention. We provide multiple pearls and pitfalls in the imaging of skull base infections.

Case: A 70-year-old male with decreased visual acuity, puffiness, tearing, and diplopia in the right eye had a non-contrast head CT performed at an outside hospital showing a right sphenoid wing mass. Surgical resection was planned ([Figs. 1]–[3]).[1]-[3]

Fig. 1 CT shows abnormal soft tissue in the right orbital apex and lateral rectus muscle.

Fig. 2 The patient presented 2 weeks later with worsening symptoms. Axial T1W (A) T1W post contrast (B) image shows increased abnormal enhancing soft tissue in the right orbital apex with mass effects on the optic nerve extending into the middle cranial fossa.

Fig. 3 MR perfusion shows increased rCBV of the enhancing mass with associated restricted diffusion (not shown). Given findings, initial interpretation was lymphoma/aggressive malignancy. However, rapid rate of growth should have prompted an alternate diagnosis. Post resection pathology was actinomyces infection.

Publication History

Article published online:
15 February 2022

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