Imaging of the pituitary

Recommendations for the diagnosis and radiological follow-up of pituitary neuroendocrine tumours

Pituitary neuroendocrine tumours (PitNETs) constitute a heterogeneous group of tumours with a gradually increasing incidence, partly accounted for by more sensitive imaging techniques and more extensive experience in neuroradiology in this regard. Although most PitNETs are indolent, some exhibit aggressive behaviour, and recurrence may be seen after surgical removal. The changes introduced in the WHO classification in 2017 and terminological debates in relation to neuroendocrine tumours warrant an update of the guidelines for the diagnosis, preoperative and postoperative management, and follow-up of response to treatment of PitNETs. This multidisciplinary document, an initiative of the Neuroendocrinology area of the Sociedad Española de Endocrinología y Nutrición [Spanish Society of Endocrinology and Nutrition] (SEEN), focuses on neuroimaging studies for the diagnosis, prognosis and follow-up of PitNETs. The basic requirements and elements that should be covered by magnetic resonance imaging are described, and a minimum radiology report to aid clinicians in treatment decision-making is proposed. This work supplements the consensus between the Neuroendocrinology area of the SEEN and the Sociedad Española de Anatomía Patológica [Spanish Society of Pathology] (SEAP) for the pathological study of PitNETs.

Adrenal insufficiency

Adrenal insufficiency (AI), first described by Thomas Addison in 1855, is characterised by inadequate hormonal production by the adrenal gland, which could either be primary, due to destruction of the adrenal cortex, or secondary/tertiary, due to lack of adrenocorticotropic hormone or its stimulation by corticotropin-releasing hormone. This was an invariably fatal condition in Addison's days with most patients dying within a few years of diagnosis. However, discovery of cortisone in the 1940s not only improved the life expectancy of these patients but also had a dramatic effect on their overall quality of life. The diagnosis, easily confirmed by demonstrating inappropriately low cortisol secretion, is often delayed by months, and many patients present with acute adrenal crisis. Sudden withdrawal from chronic glucocorticoid therapy is the most common cause of AI. Currently, there remains a wide variation in the management of this condition across Europe. As primary AI is a relatively rare condition, most medical specialists will only manage a handful of these patients in their career. Despite many advances in recent years, there is currently no curative option, and modern cortisol replacement regimens fail to adequately mimic physiological cortisol rhythm. A number of new approaches including allograft of adrenocortical tissue and stem cell therapy are being tried but remain largely experimental.

Imaging of the sellar and parasellar regions

Although a wide variety of pathologies can occur in the limited anatomic space within and surrounding the sella turcica only a few are common. This review aims to briefly summarize pituitary and parasellar anatomy and provide a focused description of the imaging features of both common and rare pituitary pathologies. Diagnoses of imaging findings with important implications for clinical management are highlighted. MR is the primary diagnostic modality for evaluation of this anatomic region. CT supplements MR in the evaluation of pathologies involving the bony sella turcica while angiography or nuclear medicine plays a limited clinical role. Despite the wide array of pathologies, imaging and basic clinical history will frequently yield a specific diagnosis or narrow differential. In certain pathologies such as hypophysitis or pituitary hyperplasia, proper imaging interpretation may obviate the need for surgical biopsy or resection. The two key elements to diagnosis in the pituitary region are localization of the abnormality and recognition of characteristic imaging features for different pathologies. Localization is particularly important in separating parasellar masses such as meningiomas, skull base tumors, carotid aneurysms, craniopharyngiomas, or sphenoid sinus tumors from pituitary masses. Imaging features are often variable and in some cases such as craniopharyngioma or epidermoid, can be almost pathognomonic. In cases of neoplastic pathology, imaging both provides diagnostic information and guides planning of surgical biopsy or resection. In most cases, biopsy or resection is performed though a trans-sphenoidal endoscopic route, and identifying invasion or the suprasellar cistern, skull base, or cavernous sinuses is critical.

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.

Pituitary Adenomas and Invasiveness from Anatomo-Surgical, Radiological, and Histological Perspectives: A Systematic Literature Review

Invasiveness in pituitary adenomas has been defined and investigated from multiple perspectives, with varying results when its predictive value is considered. A systematic literature review, following PRISMA guidelines, was performed, searching PubMed and Scopus databases with terms that included molecular markers, histological, radiological, anatomical and surgical data on invasiveness of pituitary adenomas. The results showed that differing views are still present for anatomical aspects of the sellar region that are relevant to the concept of invasiveness; radiological and histological diagnoses are still limited, but might improve in the future, especially if they are related to surgical findings, which have become more accurate thanks to the introduction of the endoscope. The aim is to achieve a correct distinction between truly invasive pituitary adenomas from those that, in contrast, present with extension in the parasellar area through natural pathways. At present, diagnosis of invasiveness should be based on a comprehensive analysis of radiological, intra-operative and histological findings.

Evaluation of Clinical and Magnetic Resonance Imaging Profile of Pituitary Macroadenoma: A Prospective Study

Background

Pituitary macroadenoma is a common tumor of middle-aged people. Magnetic resonance imaging (MRI) is the investigation of choice for its evaluation. Various parameters regarding the extent, consistency, and contrast uptake can be studied and a noninvasive diagnosis is possible.

Aims and Objectives

To study the MRI features and extent of pituitary macroadenomas.

Materials and Methods

We studied clinical and MRI features of 33 patients of all age groups and both sexes with pituitary macroadenomas who presented to Dayanand Medical College and Hospital, Ludhiana from January 2014 to June 2015. MRI was carried out on MAGNETOM Avanto 18 Channel 1.5 Tesla Machine by Seimens India Ltd. The dedicated sellar protocol consisted of sagittal and coronal T1-weighted image (TI-WI) and T2-WI without intravenous contrast using thin slices (3 mm) and a field of view of <200 mm.

Results

On analysis of the 33 cases, we observed that patients of pituitary macroadenoma showed an almost equal sex incidence and average age group of 50-60 years. The common presenting complaints were headache and decreased vision. Superior and inferior extent of the lesion was beyond the defined boundaries of sella in most cases, but the lateral extent was limited, resulting in characteristic "snowman-like" appearance. The imaging characteristics showed solid to predominantly solid consistency, appearing mostly heterogeneously hyperintense on T2-WI, and hypo to isointense on T1-WI with intense postcontrast enhancement. Hemorrhage is less common. Pituitary apoplexy is rare and can result in spontaneous resolution.

Conclusions

We conclude that the knowledge of clinical and imaging profile of pituitary macroadenoma can help the radiologists to diagnose these sellar lesions, and hence their therapeutic approach can be defined timely.

Assessment of the extent of pituitary macroadenomas resection in immediate postoperative MRI

OBJECTIVE

To evaluate if it is possible to determine the extent of pituitary macroadenomas resection in the immediate postoperative pituitary magnetic resonance imaging (MRI).

MATERIAL AND METHODS

MRI of patient with pituitary macroadenomas from January 2010 until October 2014 were reviewed. Those patients who had diagnostic MRI, immediate post-surgical MRI and at least one MRI control were included. We evaluate if the findings between the immediate postsurgical MRI and the subsequent MRI were concordant. Cases which didn't have evolutionary controls and those who were reoperation for recurrence were excluded. The degree of tumor resection was divided into groups: total resection, partial resection and doubtful. All MRI studies were performed on a1.5T machine following the same protocol sequences for all cases. One morphological part, a dynamic contrast iv and late contrast part.

RESULTS

Of the 73 cases included, immediate postoperative pituitary MRI was interpreted as total resection in 38 cases and tumoral rest in 28 cases, uncertainty among rest or inflammatory changes in 7 cases. Follow- up MRI identified 41 cases total resection and tumoral rest in 32. Sensitivity and specificity of 0.78 and 0.82 and positive and negative predictive value (PPV and NPV) 0.89 and 0.89 respectively were calculated.

CONCLUSION

Immediate post-surgery pituitary MRI is useful for assessing the degree of tumor resection and is a good predictor of the final degree of real resection compared with the following MRI studies. It allows us to decide the most appropriate treatment at an early stage.

Neuroendocrine disorders: pituitary imaging

Significant advances in pituitary imaging have taken place in the past several decades, including the introduction of magnetic resonance imaging (MRI). This imaging modality has vastly improved our ability to detect and characterize sellar masses and more accurately characterize the extent and spread of lesions in and around the sella. Intraoperative MRI may help improve the completeness of resection of sellar masses. Other imaging modalities, including magnetic resonance angiography, computed tomography (CT), and CT angiography, have an important role in specific cases. Interventional methods, including bilateral inferior petrosal sinus sampling, may establish the pituitary origin of corticotropin (ACTH) excess in patients with ACTH-dependent Cushing's syndrome. Pituitary imaging should be obtained in patients with pituitary hormone excess, hypopituitarism, or mass effect in the sella. Despite rapid advances in pituitary imaging, there are several diagnostic challenges remaining. Future research may help improve the radiographic detection of small sellar lesions, such as ACTH-secreting adenomas causing Cushing's disease, accurately characterize the type and extent of sellar pathologies, and provide prognostic information regarding their growth potential.

Adrenal insufficiency

Adrenal insufficiency is the clinical manifestation of deficient production or action of glucocorticoids, with or without deficiency also in mineralocorticoids and adrenal androgens. It is a life-threatening disorder that can result from primary adrenal failure or secondary adrenal disease due to impairment of the hypothalamic-pituitary axis. Prompt diagnosis and management are essential. The clinical manifestations of primary adrenal insufficiency result from deficiency of all adrenocortical hormones, but they can also include signs of other concurrent autoimmune conditions. In secondary or tertiary adrenal insufficiency, the clinical picture results from glucocorticoid deficiency only, but manifestations of the primary pathological disorder can also be present. The diagnostic investigation, although well established, can be challenging, especially in patients with secondary or tertiary adrenal insufficiency. We summarise knowledge at this time on the epidemiology, causal mechanisms, pathophysiology, clinical manifestations, diagnosis, and management of this disorder.

Advances in understanding pituitary tumors

Pituitary tumors are common in the general population. Since neuroimaging techniques have improved, pituitary tumors are more often diagnosed incidentally. About 16.7% of the general population show changes in the pituitary gland. Predominantly, pituitary tumors are benign pituitary adenomas. Pituitary carcinomas or aggressive pituitary tumors are extremely rare. They might develop from benign adenomas. New genetic and epigenetic abnormalities help us to understand pituitary tumorigenesis and might lead to therapeutical targeting drugs in the future. Macroadenomas (>1 cm) can lead to visual field disturbances, compression of cranial nerves, hypopituitarism, and infiltration of the cavernous sinuses. The functional status of the pituitary tumor is important. About half to one third of all pituitary tumors are non-functioning pituitary adenomas. The other pituitary tumors show a specific pattern of hormone secretion. About 25% to 41% of all pituitary tumors are prolactinomas, acromegaly with production of growth hormone represents 10% to 15% of adenomas, Cushing's disease with production of adrenocorticotropic hormone accounts for 10%, and other hormonal characteristics are less common. Transsphenoidal resection and total adenomectomy are desirable. Radiosurgery has enriched the surgical treatment options. Surgical treatment is the intervention of choice except for prolactinomas, where pharmaceutical treatment is recommended. Pharmaceutical treatment consists of dopamine agonists such as cabergoline and somatostatin analogues that include octreotide and pasireotide; retinoic acid is of theoretical interest while peroxisome proliferator-activated receptor-gamma-ligands are not clinically useful. In acromegaly, pegvisomant is a further treatment option. Temozolomide should be considered in aggressive pituitary tumors. In general, pharmaceutical options developed recently have extended the repertoire of treatment possibilities of pituitary tumors.

Principles of endocrinology

The endocrine system plays a major role in human survival. Endocrine glands secrete chemical messengers or hormones that affect every tissue of the body, including the periodontium, during the life of the individual. As the endocrine system influences a broad assortment of biological activities necessary for life, a general understanding of the principal components and functions of this system is essential. A fundamental assessment of hormone structure, mechanism of action and hormone transport, as well as influence on homeostasis is reviewed. A concise evaluation of the functions of the central endocrine glands, the functions of the major peripheral endocrine glands (other than gonadal tissues) and the known relationships of these hormones to the periodontium is examined.

Congenital Growth Hormone Deficiency - A Review with a Focus on Neuroimaging

Growth hormone deficiency is an important cause of short stature in childhood. It is characterised by low growth velocity in childhood and is diagnosed by stimulation testing. Individuals with growth hormone deficiency may have other pituitary hormone deficits in addition to growth hormone deficiency. When multiple pituitary hormone deficiencies are present, abnormal pituitary anatomy, as visualised on magnetic resonance imaging (MRI), is a frequent finding. The classic triad (ectopic posterior pituitary, hypoplastic or aplastic anterior pituitary and absent/thin pituitary stalk) or variants of the classic triad are commonly seen in these patients. Volumetric sequencing allows all three planes of visualisation to be reconstructed in post-processing, allowing the radiologist to more fully evaluate pituitary anatomy. The normal dimensions of the pituitary gland vary by age and precise definitions of what constitutes a hypoplastic gland are not clearly defined in the medical literature. Having an experienced neuroradiologist interpret the MRI in patients with pituitary dysfunction is very important.

Pituitary incidentalomas

The widespread use of sensitive neuroradiological imaging studies (i.e. computed tomography scan and magnetic resonance imaging) over the last years lead to the diagnosis of an increased number of asymptomatic pituitary lesions. The management of these so-called "pituitary incidentalomas" is still controversial, due to the limited data so far available on both the clinical relevance and the natural history of such incidentally discovered pituitary masses. Most pituitary incidentalomas are less than 1 cm in diameter (microincidentalomas) and are pituitary adenomas. Although these tumours are in general hormonally inactive, all the patients with incidentalomas should be screened for pituitary hypo- or hyper-function. Macroincidentalomas have greater growth potential and, when associated with hypopituitarism and/or visual disturbances, should be surgically removed. Conversely, incidentalomas not associated with hormonal alterations and dimensionally stable could be managed conservatively. This review will focus on the last data on the natural history and clinical management of pituitary incidentalomas.

A retrospective review of pituitary MRI findings in children on growth hormone therapy

BACKGROUND

Patients with congenital hypopituitarism might have the classic triad of pituitary stalk interruption syndrome, which consists of: (1) an interrupted or thin pituitarys talk, (2) an absent or ectopic posterior pituitary (EPP), and (3) anterior pituitary hypoplasia or aplasia.

OBJECTIVE

To examine the relationship between pituitary anatomy and the degree of hormonal dysfunction.

MATERIALS AND METHODS

This study involved a retrospective review of MRI findings in all children diagnosed with congenital growth hormone deficiency from 1988 to 2010 at a tertiary-level pediatric hospital.

RESULTS

Of the 52 MRIs reviewed in 52 children, 26 children had normal pituitary anatomy and 26 had one or more elements of the classic triad. Fourteen of fifteen children with multiple pituitary hormone deficiencies had structural anomalies on MRI. Twelve of 37 children with isolated growth hormone deficiency had an abnormal MRI.

CONCLUSION

Children with multiple pituitary hormone deficiencies were more likely to have the classic triad than children with isolated growth hormone deficiency. A normal MRI was the most common finding in children with isolated growth hormone deficiency.

Cushing's disease presenting with pituitary apoplexy

Pituitary tumour apoplexy is a rare but life threatening condition. Cushing's disease usually presents with clinical features of Cushing's syndrome. We report a 30-year-old male patient with Cushing's disease who presented with severe headache and right third nerve palsy. MRI of the pituitary gland revealed a pituitary adenoma with infarction suggestive of apoplexy. After a transsphenoidal surgery he developed pan-hypopituitarism with diabetes insipidus. We also review the relevant literature.