Pre- and postoperative magnetic resonance imaging appearance of the normal residual pituitary gland following macroadenoma resection: Clinical implications

Abstract

Background: To assess the relationship between the preoperative magnetic resonance imaging (MRI) appearance of the normal residual pituitary gland (NRPG) and pituitary functional outcome following transsphenoidal resection of pituitary macroadenomas.

Methods: We retrospectively reviewed the medical records of 100 consecutive patients with a pituitary macroadenoma, who underwent transsphenoidal resection. The preoperative configuration of the displaced NRPG was stratified as superior, superolateral or lateral. The extent of postoperative restitution of the NRPG was divided into four groups: Group 1 - normal residual gland or almost normal; Group 2 - more than 50% restitution; Group 3 - less than 50% of the normal residual gland; and Group 4 - barely visible or absent residual gland. The pre- and postoperative NRPG appearance was correlated with pituitary functional status.

Results: Preoperatively, the NRPG was identifiable in 79 patients, with extrasellar displacement in 53%. The displacement pattern was superior in 8%, superolateral in 32%, and lateral in 58% of the patients. If the NRPG was displaced laterally, the ipsilateral cavernous sinus was not invaded by the pituitary macroadenoma. Partial or complete pituitary function was lost in 6 / 23 (26.1%) patients with superior or superolateral displacement of the NRPG, compared to only 1 / 36 (2.8%) patients without superior displacement of the NRPG (P = 0.025). Progressive postoperative reconstitution of the NRPG was related to the preservation of the pituitary hormonal axis (Pearson Chi-Square P < 0.001).

Conclusions: Progressive displacement of the NRPG preoperatively, and lack of restitution of the NRPG on postoperative MRI appeared to correlate with the postoperative pituitary functional loss.

Keywords: Endoscopic resection; MRI; macroadenoma; pituitary gland; transsphenoidal surgery.

Figure 1

Schematic of observed preoperative distortion patterns of the normal residual pituitary gland, with corresponding examples on coronal post-contrast T1-weighted magnetic resonance imaging. Lateral (a), superior (b) and superolateral (c) displacement of the normal residual pituitary gland (NRPG) was observed in 58, 8, and 32%, respectively. Superior displacement of the NRPG was defined as a symmetrical upward displacement of the NRPG, relative to the macroadenoma, typically outside of the sella turcica. Superolateral displacement was defined as a residual pituitary gland visible along the superior border and the lateral border of the macroadenoma, also typically outside of the sella turcica. Lateral displacement of the gland was defined as a pituitary tissue along a single lateral border of the macroadenoma, often with both a sellar and suprasellar component. Inferior displacement of the NRPG was not observed in our series of macroadenomas

Figure 2

Schematic of the postoperative position of the normal residual pituitary gland (NRPG). Patterns of postoperative reconstitution of the normal pituitary gland are shown in the right hand column, with common corresponding preoperative morphologies of the gland on the left. Group 1 (a): Complete or near-normal reconstitution of the NRPG; group 2 (b): Reconstitution greater than or equal to 50%; group 3 (c): Less than 50%; and group 4 (d): NRPG barely visible or absent on postoperative magnetic resonance imaging

Figure 3

Case illustrations of pituitary macroadenomas (left) with varying degrees of reconstitution of the normal residual pituitary gland (NRPG) on postoperative magnetic resonance imaging (right). Group 1 example (a) in a patient with an acidophilic stem cell macroadenoma. The NRPG is displaced superiorly in a rim-like fashion (left); group 1 (near-normal) reconstitution of the gland (right) with intact pituitary function postoperatively. Group 2 example (b) in a non-functioning macroadenoma, with superior focal displacement of the NRPH (left); Group 2 (> 50%) reconstitution (right), with normal pituitary function postoperatively. Group 3 illustration (c) in a 31-year-old female with lateral gland displacement (left); Group 3 (< 50%) NRPG reconstitution (right), with normal endocrine function. Group 4 example (d) in a non-functioning macroadenoma with thin rim-like superior displacement of the NRPH preoperatively (left); Group 4 (barely visible) reconstitution of the gland postoperatively (right), with associated hypopituitarism

Figure 4

Proportion of patients with normal, partial or no postoperative pituitary function according to the type of postoperative magnetic resonance imaging restitution of the normal residual pituitary gland.