- Division of Neurosurgery, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
Division of Neurosurgery, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
DOI:10.4103/2152-7806.97534Copyright: © 2012 Di Maio S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Maio SD, Biswas A, Jean Lorrain Vézina, Hardy J, Gérard Mohr. Pre- and postoperative magnetic resonance imaging appearance of the normal residual pituitary gland following macroadenoma resection: Clinical implications. Surg Neurol Int 19-Jun-2012;3:67
How to cite this URL: Maio SD, Biswas A, Jean Lorrain Vézina, Hardy J, Gérard Mohr. Pre- and postoperative magnetic resonance imaging appearance of the normal residual pituitary gland following macroadenoma resection: Clinical implications. Surg Neurol Int 19-Jun-2012;3:67. Available from: http://sni.wpengine.com/surgicalint_articles/pre-and-postoperative-magnetic-resonance-imaging-appearance-of-the-normal-residual-pituitary-gland-following-macroadenoma-resection-clinical-implications-2/
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
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, macroadenoma, MRI, pituitary gland, transsphenoidal surgery
Functional preservation of the normal residual pituitary gland (NRPG) during removal of pituitary macroadenomas remains a challenge in certain cases. Since the first description of microscope-assisted selective adenoma removal first introduced by Hardy,[
Several authors have investigated the MR appearance of the normal pituitary gland, including size and shape, as a function of patient age,[
The objectives of the present study were, (1) to assess the detectability, location, and configuration of the NRPG on MRI before and after resection of pituitary macroadenomas, and (2) to correlate the NRPG appearance with postoperative pituitary function, in patients with pituitary macroadenomas.
Study design and patient population
The study design is a retrospective chart review of consecutive patients operated at the Sir Mortimer B. Davis-Jewish General Hospital from 1991 to present, for pituitary macroadenomas. The inclusion criteria included, (1) surgery via a transsphenoidal approach for pituitary macroadenoma with histological confirmation; (2) adequate MRI imaging was performed preoperatively; and the available clinical and endocrinological data were collected both (3) pre- and (4) postoperatively at follow-up. A macroadenoma was defined as having a maximal diameter of at least 10 mm. A postoperative MRI was performed at a minimum of four to six months from the time of surgery, to minimize artifacts related to residual hemostatic materials, fat graft, and scar tissue. Patients were excluded if they had previously received radiation therapy or had undergone surgical resection elsewhere. All patients were operated via the transsphenoidal approach, using either microscopic or endoscopic visualization, and had sellar floor reconstruction with bone fragments, without fat packing. Postoperative lumbar drainage was done in cases with intraoperative cerebrospinal fluid (CSF) leak.
Clinical and Endocrinological Evaluation
All patients underwent neuro-ophthalmological examination and evaluation of the endocrinological function before and after surgery and at the last follow-up. Based on the hypophyseal-adrenocortical axis integrity and need for corticosteroid replacement therapy, the postoperative anterior pituitary functions were classified as ‘eupituitary’ (normal function), ‘hypopituitary’ (partial function), and ‘panhypopituitary’ (no function). The posterior pituitary function was assessed based on a clinical diagnosis of diabetes insipidus. All patients received hydrocortisone parenterally prior to surgery, which was rapidly tapered over four-to-five days postoperatively. Evaluation of endocrinological function was performed using conventional stimulation tests by injection of the adrenocorticotropic hormone (ACTH), with continued oral administration over a time period of six weeks after surgery. Basal and stimulated (30 minutes) cortisol and basal thyroid-stimulating hormone (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured in the serum, as well as the basal levels of prolactin, insulin-like growth factor 1, total or free T3 and T4, and also estradiol or testosterone. The basal values for the hormones tested were assigned according to the manufacturers’ instructions for the hormone assays used.
The MRI studies were performed using a 1.5 Tesla magnet (Gyroscan Philips Netherlands and Signa General Electric USA). T1-weighted images (372 – 548 / 16 – 20 TR / TE) were obtained before and after the Gd-DTPA injection. Section thickness was 2.0 mm with a matrix size of 256 × 256 and a field of view of 16 – 18 cm. The pre- and postoperative MR images were independently evaluated by two observers (GM, JLV), including a neuroradiologist (JLV), and the data were ultimately classified by consensus. In all the patients, the axial, sagittal, and coronal series were evaluated, to specifically identify the NRPG including the neurohypophyseal bright spot (BS) and the residual adenohypophysis (RAH) on the pre- and post-gadolinium images, respectively. The maximal diameters in each plane were used to calculate the NRPG volume, which was compared with a database of 102 normal controls,[
The configuration of the pituitary gland was assessed in coronal projection. It was considered normal when the infundibulum was medially located in a gland of symmetric shape. Displacement and the shifts of the BS and the NRPG were classified as superior, superolateral or lateral in position [
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
In the postoperative MRI, the appearance of the NRPG was subdivided into four groups, based on the extent of morphological restitution: Group 1 — complete or near normal, Group 2 — more than 50% restitution, Group 3 — less than 50% of the expected normal residual volume, Group 4 — barely visible or absent residual gland [
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
Outcome analysis and statistics
The patients were reviewed for the improvement in their vision and endocrine function restoration in the functionally active tumor, and remission was noted in the nonfunctioning tumors. The preoperative location of the pituitary gland was correlated with the postoperative topographic restitution of the NRPG and the functional endocrine outcome.
The pituitary functional status based on residual gland appearance was analyzed using the Chi-square test. A P value of < 0.05 was considered to be statistically significant. The statistics software used for data analysis was the IBM SPSS version 19 (SPSS: An IBM Company, 2008).
Clinical Symptoms and Endocrinological function:
From 1997 to present, 100 patients (55 males and 45 females) underwent transsphenoidal removal of a pituitary macroadenoma. The baseline characteristics are presented in
Magnetic resonance imaging characterization of the normal residual pituitary gland
Preoperative visualization of the NRPG on MRI was possible in 76 cases, and the BS was visible in 67 of these patients. In all cases where the NRPG was identified, it enhanced more than the macroadenoma; 56.9% of the 76 cases with a visible NRPG also had a positive ‘sign of the stalk,’ and in 84.8% the BS was also visible. In 53.2% of these patients the NRPG was completely displaced to an extrasellar location. Preoperatively, distortion of the NRPG was noted in 75 of the 79 cases (94.9%). The most frequent pattern of displacement of the NRPG was lateral in 47 cases (58.3%;
Postoperative magnetic resonance imaging
Postoperatively, the location of the pituitary gland could be identified in 85 cases. In 34 / 40 (85.0%) patients with preoperative extrasellar displacement of the NRPG, the pituitary gland descended from the extrasellar to the intrasellar space following surgery. Postoperative re-expansion of the gland was seen, documented from an increase in its shortest diameter on the coronal images, in 85% of the cases. The pattern of postoperative restitution of the NRPG is shown in
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
Postoperative pituitary function was analyzed according to the preoperative displacement pattern of the NRPG. 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 (Pearson Chi-Square P = 0.025). The type of postoperative appearance of the residual pituitary gland grouped by endocrine status is shown in
MRI is universally used in the postoperative surveillance of pituitary adenomas, for the detection of residual or recurrent tumors. There are, however, no established reproducible criteria for the assessment of postoperative studies, particularly for differentiating implanted material from the residual or recurrent tumor, or for correlating the MRI findings with the clinical and endocrine status.[
This study investigated the detectability, location, and configuration of the pituitary gland on pre- and postoperative unenhanced and Gd-DTPA-enhanced T1-weighted MRI, and also assessed the relationship between the MRI appearance of the NRPG and pituitary functional status.
The NRPG was identified in 79% of the patients on preoperative MRI, and in all cases showed a stronger enhancement pattern than the pituitary adenoma. The gadolinium uptake significantly improved the detectability of the pituitary gland, particularly in cases of severe deformation of the pituitary gland. The improved detectability of the pituitary gland, after contrast administration, was due to the rapid and marked contrast enhancement of the pituitary gland, which exceeded that of an adenoma in most cases.[
Detectability of the NRPG was better on postoperative MRI, due to postoperative re-expansion of the pituitary gland and the high contrast between the pituitary gland and the surrounding cerebrospinal fluid, after tumor resection. Furthermore, the functional preservation of the pituitary gland appeared to be related to the extent of postoperative re-expansion of the NRPG on MRI.
The expansive growth of pituitary macroadenomas leads to compression, displacement, and deformation of the pituitary gland, and is dependent of the size, location, and extension of the adenoma. Most macroadenomas showing suprasellar extension tend to gradually displace the pituitary gland up to the extrasellar space possibly due to a pulsion phenomenon, resulting in an eccentric rim of normal gland, which forms a capsule in 53.2% of the cases. In a study by Bonneville et al., extrasellar displacement of the NRPG was observed in nearly all macroadenomas greater than 20 mm in diameter.[
Preoperative identification of a laterally displaced normal pituitary gland played an important role in the evaluation for cavernous sinus invasion. Cavernous sinus infiltration is not uncommon, and is reported in 35 – 85% of the cases,[
Following resection of the pituitary macroadenomas, repositioning and re-expansion of the pituitary gland is generally seen and appears to occur physiologically. Postoperative repositioning of the pituitary gland, evidenced by lowering from extrasellar to intrasellar and / or shifting from lateral to medial, depends partly on the degree of preoperative displacement. In cases of suprasellar displacement of the pituitary gland, postoperative lowering into the intrasellar location occurs if the tumor has been adequately decompressed. Re-expansion, evidenced by a change of configuration from crescentic and cap-like to nearly normal, was found in 32% of the patients. Repositioning and re-expansion of the pituitary gland, after tumor resection, was found to be a slowly progressive process in most cases, as demonstrated on serial postoperative MR images, however, in some cases the pituitary gland could move back into the intrasellar resection cavity as soon as the tumor was removed. Furthermore, hemostatic materials left in the endosellar space, such as gelatin foam and oxidized cellulose, could acutely conceal the residual pituitary gland.[
In spite of the extreme preoperative displacement of the NRPG in macroadenomas, some patients in our series retained normal pituitary function. The superior hypophyseal arteries, which arise from the supraclinoid portion of the internal carotid and posterior communicating arteries, supply the median eminence and the infundibulum via the primary portal system. The blood is then collected into vessels of various lengths within the infundibulum, which open into vascular sinusoids within the anterior lobe of the pituitary gland.[
The visibility of either the pituitary bright spot or the distorted residual pituitary gland on a preoperative MRI is a favorable sign for intraoperative identification and functional preservation of the normal residual gland. Postoperative pituitary hypofunction was more frequent in cases where the NRPG was displaced superiorly or superolaterally, preoperatively. Progressive postoperative restitution of the NRPG correlated with the functional preservation of the pituitary gland. Perioperatively, these MRI features could thus contribute toward predicting the endocrine functional outcome following pituitary macroadenoma surgery.
Dr. Biswas was a McGill Postdoctoral Research Fellow in Neurosurgery under the supervision of Dr. Gérard Mohr from October 1st, 2006 to March 31st, 2008 (‘Jules Hardy Fellowship in Pituitary Research’ funded by the Jewish General Hospital Foundation).
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