Pituitary corticotroph adenoma surgery
Transsphenoidal surgery is the treatment of choice for most (medical therapy is inadequate as initial therapy since there is no effective pituitary suppressive medication). Cure rates are ≈ 85% for microadenomas, but are lower for larger tumors.
Various diagnostic modalities are used when conventional magnetic resonance imaging (MRI) is negative or inconclusive. Potts et al. sought to analyze the use of two such modalities in the surgical management of Cushing’s disease: (1) Cavernous/Inferior petrosal sinus sampling(central venous sampling, CVS) for adrenocorticotropic hormone and (2) dynamic MRI (dMRI).
Potts et al. conducted a single-center, retrospective review of all patients with Cushing’s disease treated by a single neurosurgeon with endonasal transsphenoidal surgery. Accuracy of adenoma localization with CVS and dMRI was analyzed. Ninety-one consecutive patients were included. Pathology confirmed an adenoma in 66. Preoperative dMRI and CVS were performed in 40 and 37 patients, respectively, with 20 undergoing both studies. Surgical pathology was positive for adenoma in 31 dMRI patients, 25 CVS patients, and 13 who underwent both. Among patients with pathology confirming an adenoma, dMRI identified a lesion in 96.8 % and correctly lateralized the lesion in 89.7 %, while CVS correctly lateralized in 52.2-65.2 % (depending on location of sampling). Among patients with both studies, dMRI and CVS correctly lateralized in 76.9 and 61.5-69.2 %, respectively. Accuracy of CVS improved if only patients with symmetric venous drainage were considered. In this mixed population of Cushing’s disease patients, dMRI was more accurate than CVS at localizing adenomas, supporting the use of advance MRI techniques in the work-up of Cushing’s disease. CVS, however, remains an important tool in the workup of Cushing’s syndrome 1).
In 2002 Perrin et al., published the technical aspects and surgical strategy for removal 2).
Even with microadenomas, hemihypophysectomy on the side of the tumor is usually required for cure (the tumor is diffcult to completely extirpate) with attendant increased risk of CSF leak. If this fails, consideration should then be for total hypophysectomy. Failure of total hypophysectomy prompts consideration for bilateral adrenalectomy (total hypophysectomy virtually eliminates risk of Nelson’s syndrome following adrenalectomy).
If no tumor is identified on pre-op MRI:
● if Inferior petrosal sinus sampling (IPS) sampling showed a lateralizing ACTH gradient: start with a paramedian incision on the side of the higher ACTH gradient; if no adenoma is encountered, the contralateral paramedian and then midline incisions are used to explore the pituitary gland
● if IPS sampling and MRI do not suggest tumor location: the gland is explored sequentially with 2 paramedian incisions and then a midline incision
● if the adenoma cannot be found, a hemihypophysectomy is performed on the side of higher ACTH levels if IPS sampling shows a lateralizing gradient, or on the side with more suspicious tissue on frozen section. Total hypophysectomy is not routinely performed 4).