Background: The pathophysiological mechanisms behind the development, symptoms, operative results, and complications of pituitary tumors are not fully understood. A much-neglected factor is the pressure profile in the sellaturcica (intrasellar pressure) which harbors the pituitary gland.
Hypothesis and Aim: The aim of this thesis is to explore the pathophysiological mechanisms involved in pituitary tumordisease, with special focus on the role of intrasellar pressure (ISP). The underlying hypothesis is that ISP is associated with symptoms and prognosis after pituitary tumor surgery.
Method: The thesis includes four studies of different aspects of pituitary tumor disease, and their associations with ISP. These were single-center, retrospective studies based on the same well-characterized and consecutively collected population, albeit with some differences in exclusion criteria. All subjects were operated on for a pituitary tumor at the Neurosurgical Department, Umeå University Hospital, in 2009–2015, and had their ISP measured intraoperatively. Data on patient and tumor characteristics, symptoms, complications, and recovery were collected from medical files from the preoperative investigation and postoperative follow-up (3 months).
Results: In Paper I, we analyzed the impact of tumor anatomy and growth pattern on ISP. There was a positive correlation between ISP and tumor volume. Coronal tumor diameter (i.e., tumor width) showed stronger correlation with increased ISP than tumor growth in the other planes. Invasive tumors in the parasellar direction (Knosp III–IV) showed higher mean ISP than non-invasively growing tumors.
In Paper II, we evaluated hormonal disturbances pre- and postoperatively in relation to ISP. ISP was positively associated with the risk of preoperative hyperprolactinemia (in non-prolactinoma tumors) and the risk of preoperative thyroidstimulating hormone insufficiency. No association between ISP and the risk of preoperative adrenocorticotropic hormone insufficiency was found. No correlations were found between ISP and the risk of postoperative hormonal insufficiency at 3months after surgery.
In Paper III, the relations of ISP and tumor and patient characteristics to pre- and postoperative visual acuity, visual field,and cranial nerve III, IV, and VI deficits were studied. High ISP and large tumor volume were associated with increased risk of postoperative visual acuity deficits after pituitary surgery. High age was a risk factor for postoperative visual field deficits and decreased the chance of visual acuity improvement after surgery. Large tumor volume, suprasellar tumor extension, and female sex were risk factors for preoperative visual acuity and visual field deficits.
In Paper IV, the risk factors for intra- and postoperative complications in endoscopic transsphenoidal pituitary surgery(ETS) were explored. There was no substantial correlation between ISP and complications. Large tumor volume was a riskfactor for intraoperative complications, and low age a risk factor for postoperative cerebrospinal fluid leakage.
Conclusions: ISP is elevated above expected normal levels in patients with a pituitary tumor. ISP is positively associated with tumor volume. Tumor growth in a parasellar direction gives rise to higher ISP than growth in other directions. High ISP is associated with a higher risk of preoperative hyperprolactinemia and hypopituitarism in the thyroid axis. These results harmonize with the “stalk compression theory.” ISP seems not to affect hormonal recovery at 3 months. Anassociation between ISP and postoperative visual acuity impairment was seen, however, ISP was not identified as an important risk factor for visual symptoms or outcome. ISP does not seem to be a significant risk factor for intra- orpostoperative complications in ETS. ISP is heterogeneously associated with tumor anatomy, symptoms, pathophysiology and surgical outcomes in pituitary tumor disease. This thesis provides no evidence supporting routine ISP measurement during pituitary surgery, unless ISP is the primary variable of interest in research.