Inferior Petrosal Sinus Sampling Versus Dynamic Magnetic Resonance Imaging in the Surgical Management of Cushing's Disease

Keywords: Cushing's disease, Imaging, pituitary adenoma, magnetic resonance imaging, petrosal sinus sampling

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     Inferior petrosal sinus sampling (IPSS) and dynamic magnetic resonance imaging (dMRI) are important tools in the diagnosis and management of Cushing’s disease.  
     It is not known how these modalities compare in localization of corticotropic adenomas.
     Ninety-one patients underwent transsphenoidal pituitary surgery for Cushing’s disease. Of these, thirty-seven received preoperative IPSS, forty-one had preoperative dMRI, and 21 underwent both. IPSS confirmed a central source in all cases. IPSS showed lateralization in 32 (86.5%) patients, while dMRI detected an abnormality in 38 patients (92.7%), 12 of whom had a prior conventional MRI that was negative. An adenoma was identified intraoperatively in 71 (78%) cases (21 IPSS patients, 28 dMRI patients, and 11 receiving both studies). Among patients with an identified adenoma, IPSS correctly lateralized the lesion in 13 (61.9%). Six hemi-hypophysectomies were performed in patients with negative explorations based on IPSS results, with pathology showing corticotropic adenoma in 3.
     We retrospectively reviewed our surgical experience with Cushing’s disease from 2000-2008 with particular attention to the use of IPSS and dMRI as preoperative diagnostic and localization tools.
      Overall sensitivity and specificity for dMRI were 89.7% and 25%, respectively, with a positive-predictive value of 74.3%. Among patients undergoing both IPSS and dMRI, IPSS correctly lateralized the adenoma in 6 (54.5%) while dMRI correctly lateralized in 10 (90.9%, p=0.149).
     This is a retrospective study.
     In this series of Cushing’s disease patients, dMRI trended towards improved lateralization of corticotropic adenomas.
     IPSS remained important, however, for confirmation of a central ACTH source and lateralization when no adenoma was identified in surgery.


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