Non-neoplastic lesions of the cranial base

Introduction: Non-neoplastic lesions of the cranial base (or pseudotumors) are a challenging diagnostic and therapeutic problem. Their radiological characteristics may mimic other more common cranial base lesions that require surgery. Pathology can be nonspecific and definitive treatment may be empirical. Methods: During a three year period 16 patients with cranial base pseudotumours were treated in our institution. Twelve of them underwent surgery. Preoperative diagnosis, radiological and clinical characteristics, treatment modality and clinical outcome were reviewed. Results: There were 10 female patients and 6 males. Age ranged from 13 to 67 years. Seven lesions were located in the posterior cranial base, six in the middle cranial base and three in the anterior cranial fossa. The lesions were as follows: neurosarcoidosis = four cases, degenerative articular tissue = three cases, tuberculous granuloma = two cases, Tolosa-Hunt syndrome, syphilitic granuloma. vestibular neuritis, facial nerve inflammation, reactive lymphocytic proliferation, inflammatory hypophysitis and Aspergillus infection one case each. Twelve patients underwent surgery. The incidence of pseudotumors among patients undergoing surgery for cranial base tumors was 1.6% ( 12/750). The postoperative diagnosis corresponded to the preoperative diagnosis in only three of these patients: two patients with degenerative pannus and one patient with a cerebellopontine granuloma who had undergone biopsy elsewhere. These lesions simulated meningiomas most frequently on preoperative studies (six patients). Granulomas were encountered in five operated patients: two patients had tuberculosis granuloma, and one had a syphilitic granuloma and were treated with appropriate antibiotics. The other two patients had neurosarcoidosis without systemic manifestations on preoperative evaluation. Both received steroids as treatment. One patient had a vestibular neuritis that simulated an intracanalicular schwannoma. Another patient had hypophysitis that simulated a pituitary adenoma. The radiological, serological and clinical characteristics are reviewed to delineate a differential diagnosis. Conclusion: Although uncommon, inflammatory lesions of the cranial base present a diagnostic challenge, both preoperatively and postoperatively. Only 1.6% of patients with a preoperative diagnosis of skull base tumor will have a nonneoplastic lesion as final diagnosis. This small percentage does not justify preoperative stereotactic biopsy.