Pituitary Abscess: A Challenging Preoperative Diagnosis-A Multicenter Study

Abstract

Background and Objectives: Pituitary abscess (PA) is a rare occurrence, representing less than 1% of pituitary lesions, and is defined by the presence of an infected purulent collection within the sella turcica. Pas can be classified as either primary, when the underlying pituitary is normal prior to infection, or secondary, when there is associated a pre-existing sellar pathology (i.e., pituitary adenoma, Rathke's cleft cysts, or craniopharyngioma), with or without a recent history of surgery. Preoperative diagnosis, owing to both non-specific symptoms and imaging features, remains challenging. Treatment options include endonasal trans-sphenoidal pus evacuation, as well as culture and tailored antibiotic therapy. Methods: A retrospective multicenter study, conducted on a prospectively built database over a 20-year period, identified a large series of 84 patients harboring primary sellar abscess. The study aimed to identify crucial clinical and imaging features in order to accelerate appropriate management. Results: The most common clinical presentation was a symptom triad consisting of various degrees of asthenia (75%), visual impairment (71%), and headache (50%). Diagnosis was achieved in 95% of cases peri- or postoperatively. Functional recovery was good for visual disturbances and headache. Pituitary function recovery remained very poor (23%), whereas the preoperative diagnosis represented a protective factor. Conclusions: In light of the high prevalence of pituitary dysfunction following the management of PAs, early diagnosis and treatment might represent a crucial issue. Currently, there are no standard investigations to establish a conclusive preoperative diagnosis; however, new, emerging imaging methods, in particular nuclear imaging modalities, represent a very promising tool, whose potential warrants further investigations.

Keywords: 18-FDG PET scan; nuclear medicine; pituitary abscess; pituitary adenoma; sellar abscess; sellar pathology.

Figure 1

Preoperative T1 weighted enhanced MRI coronal (a), sagittal (b), and axial (c), demonstrating a ring enhancing intra-sellar mass with supra-sellar extension in a 14-year-old boy with a 4 day history of sudden headache, nausea and vomiting associated with thyroid insufficiency. The patient underwent an endoscopic endonasal surgery and the perioperative findings consisted of a primary PA. Bacteriologic investigation revealed a Staphylococcus Aureus infection that was treated by targeted therapy with a favorable outcome. The patient came back 4 months later complaining of progressive headache; an enhanced MRI showed the recurrence of the ring-like intra-suprasellar SOL; on this occasion an 18-FDG PET scan (d) showed a hyper-metabolism in the right anterior part of sella, favoring a diagnosis of recurrent PA. Re-do surgery and antibiotic therapy allowed a good outcome without further recurrence at 2-year FU; (e) histopathological analysis: the pituitary parenchyma appears fully necrotic and contains an intense pyogenic inflammatory infiltration (hematoxylin eosin × 10).

Figure 2

Algorithm for clinical decision-making process in lesions diagnosed as PAs. SOL: space occupying lesion; MRI: Magnetic Resonance Imaging; DI: Diabetes Insipidus; DWI: Diffusion Weighted Images; 18 FDG PET: fluorodesossiglucose positron emission tomography.