Multidisciplinary Approach to Inflammatory Pseudotumors of the Skull Base

Background: Inflammatory pseudotumor (IPT) of the skull base is a rare, idiopathic, benign fibroinflammatory lesion that often mimics a neoplastic or infectious process due to its aggressive and locally destructive features, both clinically and radiographically. Therefore, tissue biopsy is crucial for definitive diagnosis. Patients with IPT may present a diagnostic challenge to clinicians, often requiring evaluation by numerous specialists and undergoing multiple biopsies, which may lead to delays in proper diagnosis and management. The objective of this study is to review our institution’s experience with IPTs of the skull base and introduce a multidisciplinary approach to the diagnosis and management of these lesions.

Methods: Retrospective case series.

Results: We present seven patients with IPT of the anterior and lateral skull base who were evaluated in our academic otolaryngology department from 2002 to 2016. Six patients with anterior skull base IPT presented with at least one, and up to four, cranial neuropathies. Other common presenting symptoms included pain (headache, otalgia), vision changes (diplopia, blurry vision), hearing loss, facial numbness, and trismus, and correlated with lesion location. Patients had negative rheumatologic and infectious serology work-up but all had elevated inflammatory markers. Diagnostic imaging revealed an infiltrative soft tissue mass in the skull base with bony changes on computed tomography (CT) and enhancement on magnetic resonance imaging (MRI). Three patients had dural enhancement concerning for intracranial extension and two patients had carotid artery encasement. All patients underwent surgical biopsy for definitive diagnosis. One patient with a lateral skull base IPT underwent mastoidectomy while the other six patients with anterior skull base IPT underwent image-guided endoscopic endonasal biopsies. Pathologic work-up included tissue culture, histopathology and immunohistochemistry to exclude infection and malignancy. Six patients were initially treated with high dose steroids alone or a combination of steroids and surgery. One patient underwent primary surgical resection because initial frozen pathology was suspicious for chondrosarcoma and also received adjuvant radiation. Five patients developed disease recurrence. A combination of steroids, radiation therapy and immunosuppressive therapy with methotrexate, rituximab, or azathioprine was used for persistent or recurrent disease. Multidisciplinary teams of providers from otolaryngology, neurosurgery, rheumatology, neurology, infectious disease, neuro-oncology, ophthalmology, and radiation-oncology were involved in the management of the patients. All patients are alive with stable disease or no radiologic evidence of disease at last follow-up (range follow-up between 21 and 120 months).

Conclusion: The diverse symptomatology of skull base IPT makes its diagnosis challenging. Initial laboratory testing including inflammatory markers may be helpful. Its diagnosis requires close cooperation between surgeon, radiologist and pathologist to rule out infection or malignancy. CT and MRI are complementary modalities useful for differential diagnosis, although aggressive imaging characteristics may resemble a neoplasm. Tissue biopsy is mandatory for definitive diagnosis and image-guidance allows anatomic confirmation of occult lesions in the deep skull base. If tolerated, initial therapy with high-dose corticosteroids is advocated for skull base sites that risk high morbidity from surgical resection. A multi-modal and multidisciplinary approach with a combination of steroids, surgery, chemotherapy and radiation may be required for recalcitrant or recurrent disease.