Magnetic Resonance Imaging Characteristics of Pituitary Abscess: A Review of 51 Cases.

OBJECTIVE: To investigate pituitary abscess (PA) magnetic resonance imaging (MRI) features to improve the neuroradiologic and diagnostic knowledge of this rare disease and guide follow-up treatments.

METHODS: Clinical data were collected for 51 patients with PA, and MRI data were quantitatively reviewed in a retrospective analysis. Clinical factors were analyzed to investigate their relevance.

RESULTS: PA neuroimaging showed special radiologic features, including hypointensity or isointensity on T1-weighted imaging (30 patients, 58.8%), isointensity or hyperintensity on T2-weighted imaging (39 patients, 76.5%), and disappearance of the posterior pituitary bright spot in most patients (44 patients, 86.3%). After gadolinium injection, rim or rimlike enhancement was observed in 82.4% of patients (n = 42). Half of those patients showed typical rim enhancement (profound peripheral enhancement with internal hypointensity); others showed atypical rim enhancement with special signs, such as enhanced, thick abscess wall and hyperintense flocculent or cottonlike foci within the internal hypointense region. Almost all patients (96.1%) presented at least 1 sign of adjacent anatomic structure invasion, including peripheral meninges enhancement, pituitary stalk thickening, and paranasal sinus mucosa enhancement. Rank correlation analysis of the clinical time course and MRI characteristics of PA showed a Spearman correlation coefficient of 0.270, indicating borderline significance (P = 0.055).

CONCLUSIONS: Classic MRI characteristics of PA show T1 signal hypointensity or isointensity, T2 signal isointensity or hyperintensity, and peripheral rim enhancement after gadolinium injection. The MRI appearance of PA may reflect the abscess liquefaction and formation. Despite its profound significance for differential diagnosis, adjacent structure invasion is generally ignored by clinicians.