Neuroendocrine disorders: pituitary imaging

Pituitary incidentaloma

Pituitary incidentalomas (PI) are lesions of the pituitary region discovered fortuitously by imaging for reasons unrelated to pituitary disease. They range from small cysts to large invasive adenomas. All over the world, improvements in the quality and availability of radiological examinations are leading to an increase in the discovery of PI. In the last four decades, significant advances have been made in the understanding of PI. Autopsy studies have shown that about 10% of deceased individuals harbour a PI, most often a non-functioning microadenoma. In contrast, modern patient series showed that among PIs that come to endocrinological attention, a significant proportion are macroadenomas, and many patients suffer from asymptomatic or pauci-symptomatic endocrine or ophthalmologic disturbances. Other than adenomas, empty sella, Rathke's cleft cyst, craniopharyngioma and meningioma are the most frequent types of PIs. About 10% of micro-incidentalomas and 25% of macro-incidentalomas grow over time. Most cases can be managed conservatively by mere surveillance. Follow-up is necessary in all patients with macroadenoma, but uncertainty remains for microadenomas as to the extent of endocrinological work-up as well as the necessity and duration of follow-up. Visual and endocrine anomalies constitute the most common indications for surgery. When needed, surgery yields better outcome in PIs than in symptomatic pituitary lesions.

Magnetic resonance imaging of the hypothalamo-pituitary region

The diagnosis and management of mass lesions in the sellar and parasellar areas remain challenging. When approaching patients with possible sellar or hypothalamic masses, it is important not only to focus on imaging but also detect possible pituitary hormone deficits or excess, in order to establish an appropriate diagnosis and initiate treatment. The imaging modalities used to characterize hypothalamic and pituitary lesions have significantly evolved over the course of the past several years. Computed tomography (CT) and CT angiography play a major role in detecting various sellar lesions, especially in patients who have contraindications to magnetic resonance imaging (MRI) and can also yield important information for surgical planning. However, MRI has become the gold standard for the detection and characterization of hypothalamic and pituitary tumors, infections, cystic, or vascular lesions. Indeed, the imaging characteristics of hypothalamic and sellar lesions can help narrow down the differential diagnosis preoperatively. In addition, MRI can help establish the relationship of mass lesions to surrounding structures. A pituitary MRI examination should be obtained if there is concern for mass effect (including visual loss, ophthalmoplegia, headache) or if there is clinical suspicion and laboratory evidence of either hypopituitarism or pituitary hormone excess. The information obtained from MRI images also provides us with assistance in planning surgery. Using intraoperative MRI can be very helpful in assessing the adequacy of tumor resection. In addition, MRI images yield reliable data that allow for noninvasive monitoring of patients postoperatively.

Obesity and pituitary gland volume - a correlation study using three-dimensional magnetic resonance imaging

PURPOSE

Obesity has become a major health problem and is associated with endocrine disorders and a disturbed hypothalamic-pituitary axis. The purpose of this study was to correlate pituitary gland volume determined by routine magnetic resonance imaging with patient characteristics, in particular body mass index and obesity.

MATERIAL AND METHODS

A total of 144 'healthy' patients with normal findings in cerebral magnetic resonance imaging were retrospectively included. Pituitary gland volume was measured in postcontrast three-dimensional T1-weighted sequences. A polygonal three-dimensional region of interest covering the whole pituitary gland was assessed manually. Physical characteristics (gender, age, body height and body mass index) were correlated with pituitary gland volume. Multiple subgroup and regression analyses were performed.

RESULTS

Pituitary gland volumes were significantly larger in females than in males (p<0.001) and young individuals (<35 years) versus middle-aged patients (35-47 years) (p=0.042). Obese patients (body mass index ≥30) had significantly larger pituitary gland volumes than overweight (25<body mass index<30; p=0.011) and normal-weight (body mass index <25; p=0.005) patients. In males, pituitary gland volumes of body mass index subgroups showed significant differences (p=0.038). Obese males had larger pituitary gland volumes than overweight patients (p=0.066) and significantly larger volumes than normal-weight (p=0.023) patients. Obese females also had larger pituitary gland volumes but without statistical significance (p>0.05). Regression analysis showed that increased pituitary gland volume is associated with higher body mass index independent from gender, age and body height.

CONCLUSION

Pituitary gland volume is increased in obese individuals and a high body mass index can be seen as an independent predictor of increased pituitary gland volume. Therefore, gland enlargement might be an imaging indicator of dysfunction in the hypothalamus-pituitary axis. Besides gender and age, body mass index should be considered by radiologists when diagnosing abnormal changes in pituitary gland volume.

Folate Receptor Near-Infrared Optical Imaging Provides Sensitive and Specific Intraoperative Visualization of Nonfunctional Pituitary Adenomas

BACKGROUND

Surgical resection is the primary treatment for nonfunctional (NF) pituitary adenomas, but gross-total resection is difficult to achieve in all cases. NF adenomas overexpress folate receptor alpha (FRα).

OBJECTIVE

To test the hypothesis that we could target FRα for highly sensitive and specific intraoperative detection of NF adenomas using near-infrared (NIR) imaging.

METHODS

Fourteen patients with NF pituitary adenoma were infused with the folate analog NIR dye OTL38 preoperatively. NIR fluorescence signal-to-background ratio (SBR) was recorded for each tumor during resection of the adenomas. Extent of surgery was not modified based on the presence or absence of fluorescence. Immunohistochemistry was performed to assess FRα expression in all specimens. Magnetic resonance imaging (MRI) was performed postoperatively to assess residual neoplasm.

RESULTS

Nine adenomas overexpressed FRα and fluoresced with a NIR SBR of 3.2 ± 0.52, whereas the 5 non-FRα-overexpressing adenomas fluoresced with an SBR of 1.5 ± 0.21. Linear regression demonstrated a significant correlation between intraoperative SBR and the FRα expression (P-value < .001). Analysis of 14 margin samples revealed that the surgeon's impression of the tissue had 83% sensitivity, 100% specificity, 100% positive predictive value, and 89% negative predictive value, while NIR fluorescence had 100% for all values. NIR fluorescence accurately predicted postoperative MRI results in 78% of FRα-overexpressing patients.

CONCLUSION

Preoperative injection of folate-tagged NIR dye provides strong signal and visualization of NF pituitary adenomas. It is 100% sensitive and specific for detecting margin neoplasm and can predict postoperative MRI findings. Our results suggest that NIR fluorescence may be superior to white-light visualization alone and may improve resection rates in NF pituitary adenomas.

Pituitary Disease in Pregnancy: Special Aspects of Diagnosis and Treatment?

The diagnosis and treatment of pituitary disease in pregnancy represents a special clinical challenge. Not least because there is very little data on the treatment of pregnant patients with pituitary disorders. A selective search of the literature was carried out with the aim of compiling evidence about the diagnosis and treatment of pituitary disease in pregnancy. The search covered the databases PubMed/MEDLINE including PubMed Central and also used the Livivo (ZB MED) search engine. Recent studies were evaluated for recommendations about the care of pregnant patients with hormone-inactive and hormone-active pituitary adenomas (prolactinoma, acromegaly and Cushing's disease), pituitary insufficiency, pituitary apoplexy and hypophysitis. The most well-established forms of treatment are for prolactinoma, due to the incidence of this disease and its impact on fertility. When pregnancy has been confirmed, prolactinoma treatment with dopamine agonists should be paused. Although microprolactinomas rarely increase significantly in size after the administration of dopamine agonists is discontinued, symptomatic tumor growth of macroprolactinomas can occur. In such cases, treatment with dopamine agonists can be resumed. If the primary tumor is large and the risk that it will continue to grow is high, it may be necessary to continue medical treatment from the start of pregnancy. If one of the partners has a pituitary disorder, it is often still possible for many couples to achieve their wish of having children if they receive medical support to plan and the pregnancy is carefully monitored. Given the complexity of pituitary disease, pregnant patients with pituitary disorders should be cared for and treated by a multidisciplinary team in centers specializing in the diagnosis and treatment of pituitary disease.

Folate receptor overexpression can be visualized in real time during pituitary adenoma endoscopic transsphenoidal surgery with near-infrared imaging

OBJECTIVE Pituitary adenomas account for approximately 10% of intracranial tumors and have an estimated prevalence of 15%-20% in the general US population. Resection is the primary treatment for pituitary adenomas, and the transsphenoidal approach remains the most common. The greatest challenge with pituitary adenomas is that 20% of patients develop tumor recurrence. Current approaches to reduce recurrence, such as intraoperative MRI, are costly, associated with high false-positive rates, and not recommended. Pituitary adenomas are known to overexpress folate receptor alpha (FRα), and it was hypothesized that OTL38, a folate analog conjugated to a near-infrared (NIR) fluorescent dye, could provide real-time intraoperative visual contrast of the tumor versus the surrounding nonneoplastic tissues. The preliminary results of this novel clinical trial are presented. METHODS Nineteen adult patients who presented with pituitary adenoma were enrolled. Patients were infused with OTL38 2-4 hours prior to surgery. A 4-mm endoscope with both visible and NIR light capabilities was used to visualize the pituitary adenoma and its margins in real time during surgery. The signal-to-background ratio (SBR) was recorded for each tumor and surrounding tissues at various endoscope-to-sella distances. Immunohistochemical analysis was performed to assess the FRα expression levels in all specimens and classify patients as having either high or low FRα expression. RESULTS Data from 15 patients (4 with null cell adenomas, 1 clinically silent gonadotroph, 1 totally silent somatotroph, 5 with a corticotroph, 3 with somatotrophs, and 1 somatocorticotroph) were analyzed in this preliminary analysis. Four patients were excluded for technical considerations. Intraoperative NIR imaging delineated the main tumors in all 15 patients with an average SBR of 1.9 ± 0.70. The FRα expression level of the adenomas and endoscope-to-sella distance had statistically significant impacts on the fluorescent SBRs. Additional considerations included adenoma functional status and time from OTL38 injection. SBRs were 3.0 ± 0.29 for tumors with high FRα expression (n = 3) and 1.6 ± 0.43 for tumors with low FRα expression (n = 12; p < 0.05). In 3 patients with immunohistochemistry-confirmed FRα overexpression (2 patients with null cell adenoma and 1 patient with clinically silent gonadotroph), intraoperative NIR imaging demonstrated perfect classification of the tumor margins with 100% sensitivity and 100% specificity. In addition, for these 3 patients, intraoperative residual fluorescence predicted postoperative MRI results with perfect concordance. CONCLUSIONS Pituitary adenomas and their margins can be intraoperatively visualized with the preoperative injection of OTL38, a folate analog conjugated to NIR dye. Tumor-to-background contrast is most pronounced in adenomas that overexpress FRα. Intraoperative SBR at the appropriate endoscope-to-sella distance can predict adenoma FRα expression status in real time. This work suggests that for adenomas with high FRα expression, it may be possible to identify margins and to predict postoperative MRI findings.