Anterior and posterior lobes of the pituitary gland: assessment by 1.5 T MR imaging

MRI atlas of the pituitary gland in young female adults

The probabilistic topography and inter-individual variability of the pituitary gland (PG) remain undetermined. The absence of a standardized reference atlas hinders research on PG volumetrics. In this study, we aimed at creating maximum probability maps for the anterior and posterior PG in young female adults. We manually delineated the anterior and posterior parts of the pituitary glands in 26 healthy subjects using high-resolution MRI T1 images. A three-step procedure and a cost function-masking approach were employed to optimize spatial normalization for the PG. We generated probabilistic atlases and maximum probability maps, which were subsequently coregistered back to the subjects' space and compared to manual delineations. Manual measurements led to a total pituitary volume of 705 ± 88 mm³, with the anterior and posterior volumes measuring 614 ± 82 mm³ and 91 ± 20 mm³, respectively. The mean relative volume difference between manual and atlas-based estimations was 1.3%. The global pituitary atlas exhibited an 80% (± 9%) overlap for the DICE index and 67% (± 11%) for the Jaccard index. Similarly, these values were 77% (± 13%) and 64% (± 14%) for the anterior pituitary atlas and 62% (± 21%) and 47% (± 17%) for the posterior PG atlas, respectively. We observed a substantial concordance and a significant correlation between the volume estimations of the manual and atlas-based methods for the global pituitary and anterior volumes. The maximum probability maps of the anterior and posterior PG lay the groundwork for automatic atlas-based segmentation methods and the standardized analysis of large PG datasets.

Structure-function relationship of the pituitary gland in anorexia nervosa and intense physical activity

Patients with Anorexia Nervosa (AN) and athletes share intense physical activity and pituitary hormonal disturbances related to absolute (AN) or relative (athletes) undernutrition. Pituitary gland (PG) structure evaluations in those conditions are scarce, and did not differentiate anterior from posterior lobe. We evaluated the structure-function relationship of anterior and posterior PG in AN and athletes, and potential reversibility of this alteration in a group of weight-recovered patients (AN_Rec). Manual delineation of anterior (AP) and posterior (PP) PG was performed on T1-weighted MR images in 17 women with AN, 15 women with AN_Rec, 18 athletes women and 25 female controls. Anthropometric, hormonal, and psychometric parameters were explored and correlated with PG volumes. AP volume (APV) was lower in AN (448 ± 82 mm3), AN_Rec (505 ± 59 mm3), and athletes (540 ± 101 mm3) vs. Controls (615 ± 61 mm3, p < 0.00001, p < 0.00001 and p = 0.02, respectively); and smaller in AN vs. AN_Rec (p = 0.007). PP volume did not show any differences between the groups. APV was positively correlated with weight (R = 0.36, p = 0.011) in AN, and luteinizing hormone (R = 0.35, p = 0.014) in total group. In AN, mean growth hormone (GH) was negatively correlated with global pituitary volume (R = 0.31, p = 0.031) and APV (R = 0.29, p = 0.037). Absolute and relative undernutrition led to a decreased anterior pituitary gland volume, which was reversible with weight gain, correlated with low bodyweight, and blockade of gonadal hypothalamic-pituitary axis. Intriguing inverse correlation between anterior pituitary gland volume and GH plasma level could suggests a low storage capacity of anterior pituitary gland and increased reactivity to low insulin-like growth factor type 1.

Dorsoventral splitting of the infundibulum in a child with pituitary hypoplasia

Pituitary development arises from ectodermal tissue creating Rathke's pouch and ultimately the adenohypophysis anteriorly whereas neuroectodermal tissue arising from the diencephalon creates the neurohypophysis posteriorly. Alterations in pituitary development can lead to hormonal dysregulation and dysfunction. Following clinical suspicion of pituitary endocrinopathy, MRI plays a vital role in identifying and characterizing underlying structural abnormalities of the pituitary gland, as well as any associated extrapituitary findings. Here we report a case of an 18-month-old female presenting with short stature and growth hormone deficiency. MRI was notable for a shallow sella turcica, a hypoplastic adenohypophysis, thin pituitary stalk, and ectopic neurohypophysis. Interestingly, the pituitary stalk was noted to split dorsoventrally with a split pituitary bright spot and T1 hypointense lobe hypothesized to represent separation of the posterior pituitary lobes.

Pituitary Stalk Interruption Syndrome: A Case Report

Pituitary stalk interruption syndrome is a congenital abnormality. The triad of this syndrome comprises a thin pituitary stalk, an ectopic posterior pituitary gland, and an absent or hypoplastic anterior pituitary gland. The patient typically presents with a spectrum of symptoms secondary to anterior pituitary hormonal deficiency. The etiology of this syndrome is not established but is likely due to a genetic mutation. The prognosis is good if the syndrome is diagnosed early and hormonal therapy is started promptly. Early diagnosis is crucial in preventing adverse effects on growth and development. The diagnosis of pituitary stalk interruption syndrome is based on magnetic resonance imaging (MRI) findings. This study presents the case of a young girl who presented with complaints of short stature and amenorrhea and was diagnosed with pituitary stalk interruption syndrome following an MRI.

A Novel Missense Mutation in Human Receptor Roundabout-1 (ROBO1) Gene Associated with Pituitary Stalk Interruption Syndrome

Pituitary stalk interruption syndrome (PSIS) is characterized by the association of an absent or thin pituitary stalk, an absent or hypoplastic anterior pituitary lobe and an ectopic posterior pituitary (EPP) lobe. The causes of this anatomical defect include both genetic and environmental factors. Molecular genetic defects have been indentified in a small number of patients with PSIS. A 4-year-old boy presented with hypoglycemia and hyponatremia associated with growth hormone, thyroid stimulating hormone, and adrenocorticotropic hormone deficiencies. The patient had right sided strabismus. magnetic resonance imaging images showed pituitary hypoplasia, EPP and absent pituitary stalk. A novel Receptor Roundabout-1 (ROBO1) missense mutation (c.1690C>T, p.Pro564Ser) that may contribute to the disorder was found in this patient and his mother, who also exhibited pituitary abnormalities.

Study of Pituitary Morphometry Using MRI in Indian Subjects

AIM

To establish normative measurements of pituitary gland in Indian population.

MATERIAL AND METHODS

In this cross-sectional study, we measured dimensions of pituitary gland in 482 (213 females and 269 males) Indian subjects with apparently normal pituitary gland function. Mid-sagittal T1-weighted image (T1-WI) on magnetic resonance imaging (MRI) was used to measure height and length of pituitary gland. Pituitary gland width was measured using coronal T1-WI and pituitary gland volume was calculated.

RESULTS

Mean height, length and calculated volume of pituitary gland was significantly higher in females compared to males (p = <0.001, P = 0.03 and P = <0.001, respectively) when all age groups were combined but pituitary gland width was not statistically different in male and female subjects. When subjects were divided into different age groups, except for 10-14 years age group where pituitary height was significantly higher in females as compared to male, no significant difference was observed between male and female in any of the parameters (height, length, width and volume). The mean pituitary gland height was 5.80 ± 1.32 mm and 5.37 ± 1.25 mm in female and male subjects, respectively. Females achieved peak pituitary gland height in 10 to 14-year age group, while males achieved their peak pituitary gland height in 15 to 19-year age group.

CONCLUSION

Our study provides age and sex wise normative data for pituitary measurements derived from Indian population.

Pituitary Stalk Interruption Syndrome: From Clinical Findings to Pathogenesis

Pituitary stalk interruption syndrome (PSIS) is a rare congenital defect manifesting with varying degrees of pituitary hormone deficiency. The signs and symptoms of PSIS during the neonatal period and infancy are often overlooked and therefore diagnosis is delayed. The typical manifestations of PSIS can be detected by magnetic resonance imaging. Several genes in the Wnt, Notch and Shh signalling pathways related to hypothalamic-pituitary development, such as PIT1, PROP1, LHX3/LHX4, PROKR2, OTX2, TGIF and HESX1, have been found to be associated with PSIS. Nevertheless, the aetiology in the majority of cases still remains unknown. In the present review, we provide an overview of clinical features of PSIS and summarise our current understanding of the underlying pathogenic mechanisms for this rare syndrome. Furthermore, we propose future research directions that may help our understanding of the aetiology of PSIS.

Pituitary Microadenoma

Twenty surgically proven pituitary microadenomas were examined with MR imaging and CT. MR demonstrated 20 of 20 microadenomas: 90% of the tumors were hypointense on T1-weighted images before Gd-DTPA administration and in 45% the tumors were more clearly delineated postcontrast. CT demonstrated 19 of 20 diagnosed microadenomas: showing low attenuation in 85% of the tumors precontrast. Iohexol facilitated delineation of the tumors in 45%. Focal enlargement of the gland and diaphragma sellae convexity were more useful than infundibular tilting and sellar—floor erosion as ancillary findings supporting the diagnosis. In general, CT and MR agreed regarding the microadenomas' size and location, measurement of enlarged intrasellar contents, detection of the diaphragma sellae bulge, and demonstration of infundibulum abnormality. CT was more sensitive than MR in identifying sellar—floor erosion. We suggest that CT be the first method for demonstration of microadenomas.

Magnetic resonance imaging of sellar and juxtasellar abnormalities in the paediatric population: an imaging review

The sellar and juxtasellar regions in the paediatric population are complex both anatomically and pathologically, with magnetic resonance imaging (MRI) being the "gold standard" imaging modality due to the high contrast of detail. Assessment requires a detailed understanding of the anatomy, embryology, pathophysiology and normal signal characteristics of the pituitary gland and surrounding structures in order to appropriately characterise abnormalities. This article aims to provide an overview of the imaging characteristics of developmental/congenital and acquired disease processes which affect the sellar and juxtasellar region in the paediatric population. Main Messages • The sellar region is anatomically complex and covers a wide pathology spectrum. • MRI is the key imaging modality to assess sellar and juxtasellar pathology. • Numerous developmental anomalies may not be discovered until adulthood. • Knowledge of pathology alerts and guides the clinician towards appropriate management.

Three-dimensional magnetic resonance volumetry of the pituitary gland is effective in detecting short stature in children

The aim of the present study was to obtain standard reference values for the pituitary gland volumes of healthy children and to analyze the potential diagnostic values of pituitary gland volumetry for growth hormone deficiency (GHD) and idiopathic short stature (ISS). The volume of the pituitary gland was measured using a thin-section three-dimensional (3D) magnetic resonance imaging (MRI) sequence of magnetization-prepared rapid gradient echo imaging with a section thickness of 1 mm. A group of 75 healthy children aged between 1 and 19 years were recruited to obtain normal volumetry values of the pituitary gland. These individuals demonstrated no evidence of abnormalities to the central nervous or endocrine systems prior to the study. An additional group of 55 children with GHD (n=32) or ISS (n=23) aged between 0 and 14 years were included in the measurement of pituitary gland volume and height. The Student’s t-test was used to evaluate the repetition test, while Pearson’s correlation coefficient and regression analyses were performed to examine the correlations between the volume and height of the pituitary glands. Pituitary gland volume and height demonstrated an increasing trend with age in the healthy children. In addition, the pituitary gland volume exhibited a growth spurt in the early teenage years (10–14 years-old), which was more prominent in females. The growth spurt was not observed for pituitary gland height. When compared with the healthy children, 65.6% of the children with GHD and 34.8% of the children with ISS had smaller pituitary gland volumes. Similarly, 37.5% of the children with GHD and 26.1% of the children with ISS had a smaller pituitary gland height compared with the healthy children. The pituitary gland volume performed significantly better compared with height with regard to the detection rate. Therefore, the results indicated that 3D MRI volumetry was useful for understanding the developmental characteristics of the pituitary gland in healthy children, and that the reference data provided by 3D MRI were effective in the diagnosis of short stature following associations with neuroimaging and clinical functional abnormalities of the pituitary gland.

Normal dimensions of the posterior pituitary bright spot on magnetic resonance imaging

Object

The normal pituitary bright spot seen on unenhanced T1-weighted MRI is thought to result from the T1-shortening effect of the vasopressin stored in the posterior pituitary. Individual variations in its size may be difficult to differentiate from pathological conditions resulting in either absence of the pituitary bright spot or in T1-hyperintense lesions of the sella. The objective of this paper was to define a range of normal dimensions of the pituitary bright spot and to illustrate some of the most commonly encountered pathologies that result in absence or enlargement of the pituitary bright spot.

Methods

The authors selected normal pituitary MRI studies from 106 patients with no pituitary abnormality. The size of each pituitary bright spot was measured in the longest axis and in the dimension perpendicular to this axis to describe the typical dimensions. The authors also present cases of patients with pituitary abnormalities to highlight the differences and potential overlap between normal and pathological pituitary imaging.

Results

All of the studies evaluated were found to have pituitary bright spots, and the mean dimensions were 4.8 mm in the long axis and 2.4 mm in the short axis. The dimension of the pituitary bright spot in the long axis decreased with patient age. The distribution of dimensions of the pituitary bright spot was normal, indicating that 99.7% of patients should have a pituitary bright spot measuring between 1.2 and 8.5 mm in its long axis and between 0.4 and 4.4 mm in its short axis, an interval corresponding to 3 standard deviations below and above the mean. In cases where the dimension of the pituitary bright spot is outside this range, pathological conditions should be considered.

Conclusions

The pituitary bright spot should always be demonstrated on T1-weighted MRI, and its dimensions should be within the identified normal range in most patients. Outside of this range, pathological conditions affecting the pituitary bright spot should be considered.

Imaging of the pituitary and sella turcica

The pituitary gland is housed in the sella turcica and has vital endocrinologic functions. It lies in close proximity to numerous vital structures, including the optic chiasm, sphenoid sinus, cavernous sinus and hypothalamus. An understanding of the function, anatomy and embryology of the pituitary gland and its surrounding structures is vital to understanding its normal appearance, as well as in evaluating the broad spectrum of pathology that can involve the pituitary gland. Imaging of pathology in the sellar region, including pituitary adenomas, meningiomas, craniopharyngiomas and aneurysms, plays an important role in guiding treatment decisions. Modern imaging techniques are also important in evaluating the pituitary gland after surgery.

Pituitary volume in schizophrenia spectrum disorders

INTRODUCTION

There is converging evidence supporting hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in schizophrenia spectrum disorders (SSD), such as schizotypal personality disorder (SPD), first-episode schizophrenia (FESZ) and chronic schizophrenia (CHSZ). Such an aberrant HPA activity might have volumetric consequences on the pituitary gland. However, previous magnetic resonance imaging (MRI) studies assessing pituitary volume (PV) in SSD are conflicting. The main objective of this study was to examine further PV in SSD.

METHODS

PV were manually traced on structural MRIs in 137 subjects, including subjects with SPD (n = 40), FESZ (n = 15), CHSZ (n = 15), and HC (n = 67). We used an ANCOVA to test PV between groups and gender while controlling for inter-subject variability in age, years of education, socioeconomic status, and whole brain volume.

RESULTS

Overall, women had larger PV than men, and within the male sample all SSD subjects had smaller PV than HC, statistically significant only for the SPD group. In addition, dose of medication, illness duration and age of onset were not associated with PV.

CONCLUSION

Chronic untreated HPA hyperactivity might account for smaller PV in SPD subjects, whereas the absence of PV changes in FESZ and CHSZ patients might be related to the normalizing effects of antipsychotics on PV. SPD studies offer a way to examine HPA related alterations in SSD without the potential confounds of medication effects.

Influence of age and sex on signal intensities of the posterior lobe of the pituitary gland on T1-weighted images from 3 T MRI

PURPOSE

To elucidate the influence of age and sex on the signal intensity (SI) of the posterior lobe of the pituitary gland (PPG) on T1-weighted images (T1WI) from 3 T MRI.

MATERIALS AND METHODS

Sagittal T1WI acquired from three-dimensional fast spoiled gradient recalled acquisition in the steady state in 1,634 subjects without conditions affecting antidiuretic hormone were evaluated retrospectively. The presence or absence of a bright signal in the PPG was assessed qualitatively. The SI ratio of the PPG to the pons (SIR) was obtained from quantitative measurements. We statistically analyzed these data, creating 14 subject groups categorized according to age and sex, and applied a Poisson generalized linear model to the SIR data.

RESULTS

The characteristic bright signal was absent in 47 subjects (2.8 %), with no significant difference in incidence among the groups. The SIR was inversely related to age in both males (r > 0.7) and females (r > 0.9), and was significantly higher in females in the third to the eighth decades (p < 0.05). Analysis of the whole SIR dataset using a generalized linear model showed that the estimated SIR decreased by 1.7 % per decade and is higher in females.

CONCLUSION

Age and sex influence the SI of the PPG on T1WI. These findings may aid the recognition of PPG signal abnormalities on T1WI.

Imaging of the pituitary: Recent advances

Pituitary lesions, albeit relatively infrequent, can significantly alter the quality of life. This article highlights the role of advanced imaging modalities in evaluating pituitary-hypothalamic axis lesions. Magnetic resonance imaging (MRI) is the examination of choice for evaluating hypothalamic-pituitary-related endocrine diseases. Advanced MR techniques discussed in this article include dynamic contrast-enhanced MRI, 3T MRI, magnetization transfer (MT) imaging, diffusion-weighted imaging (DWI), proton MR spectroscopy, fluorine-18 fluorodeoxyglucose-positron emission tomography, single-photon emission computed tomography, intraoperative MRI, and intraoperative real-time ultrasonography.

A reappraisal of the hypophysial region of the floor of the sella turcica

While studying the detailed anatomy of the cranial sella turcica, an additional fossa in its floor, which has not previously been described, was noted. A survey for this fossa, therefore, was conducted on 205 adult crania from the Raymond A. Dart Collection of Human Skeletons, University of the Witwatersrand. To confirm the survey observations, the sella turcica region of 10 adult cadavers was also dissected. A larger anterior depression and a smaller posterior concave fossa, often extending on to the anterior surface of the dorsum sellae, were evident in the hypophysial region and occurred in 21.5% of crania and in six of the 10 dissected specimens. An anterior depression alone or a posterior fossa alone occurred in 2.4% and in 72% of the crania, respectively, indicating that the posterior fossa occurs most commonly in this series. The more commonly occurring presence of a posterior fossa abutting on to the anterior surface of the dorsum sellae is described for the first time.

Central diabetes insipidus after transsphenoidal surgery in dogs with Cushing's disease

Transsphenoidal surgery (TSS) is an effective treatment for canine Cushing's disease, as well as human Cushing's disease. In humans, only the pituitary adenoma tissue is resected by TSS. However, in dogs, the whole pituitary including normal tissue is resected. Hence, central diabetes insipidus (CDI) may complicate the postoperative course in almost all dogs with Cushing's disease treated by TSS. However, it is difficult to assess the duration of the postoperative CDI, and whether it may be transient or permanent. In this study, postoperative CDI in 21 dogs with Cushing's disease and its predicted prognosis by preoperative parameters was investigated. In this study, CDI after TSS was classified as either transient or permanent based on the requirement for desmopressin. Preoperative circulating serum cortisol concentrations and pre- and post-operative plasma AVP concentrations were not significantly different between the transient CDI dogs and permanent CDI dogs. The duration of postoperative CDI was not correlated to the signal intensity ratio (posterior lobe of the pituitary/cerebral cortex), which is obtained from preoperative magnetic resonance imaging (MRI). However, the pituitary height/brain area (P/B) ratio of the permanent CDI dogs was significantly greater than that of the transient CDI dogs. In addition, there was a significant difference between the enlarged-pituitary (P/B ratio > 0.31) transient CDI dogs and the permanent CDI dogs. These results suggest that the incidence of postoperative permanent CDI is strongly influenced by the pituitary size.

Relationship between arginine vasopressin and high signal intensity in the pituitary posterior lobe on T1-weighted MR images in dogs

The posterior lobe of the pituitary gland (PL) normally shows characteristic high signal intensity (SI) on T1-weighted MR images (T1WI) in humans. The high SI is thought to represent storage of arginine vasopressin (AVP) in the PL. Normal dogs also show a high SI on T1WIs, but the origin is unclear. In the present study, we investigated whether the high SI in the PL on T1WIs in normal dogs is caused by AVP. We examined the SI in the PL on T1WIs, plasma AVP concentrations and plasma osmolality in normal dogs after excessive AVP secretion was induced by hypertonic saline overload. In addition, functional changes in the supraoptic nucleus and paraventricular nucleus of the hypothalamus under AVP secretion-stimulated conditions were examined immunohistologically. Under hypertonic saline overload, plasma osmolality and plasma AVP concentrations gradually increased, while the SI of the PL gradually decreased. This suggests that AVP secretion was stimulated by elevated osmolality. Moreover, there was a significant negative correlation between plasma AVP concentrations and the SI ratio of the PL. An immunohistochemical study of the hypothalamus nucleus revealed that AVP-immunopositive cells significantly increased in the hypertonic saline loaded dogs. We concluded that the high SI in the PL in T1WIs in normal dogs was caused by AVP stored at the site, and examination of the SI in the PL using MRI is useful for diagnosis of abnormal pituitary glands.

Normal pituitary volumes in chronic schizophrenia

Pituitary volumes were shown to be abnormally large in pre- or first-psychotic episode patients and abnormally reduced in established schizophrenia by magnetic resonance imaging (MRI) studies. We present here the results of the second ever published MRI study exploring pituitary size in a large population of patients with chronic schizophrenia recruited from the geographically defined catchment area of South Verona, Italy. No significant differences for pituitary volumes were reported between 65 subjects with chronic schizophrenia and 65 normal individuals (mean age+/-S.D.=42.31+/-11.44 and 40.54+/-11.12 years). In contrast to Pariante et al. (2004), normal pituitary size was found in our population of chronic schizophrenia. Discrepancies between these two studies may partially be accounted by sample age and gender. Considering increased pituitary volumes in pre- or first-psychotic episode patients, we put forward the hypothesis that pituitary size may normalize or reduce with the progression of the illness as a result of reduced numbers of acute episodes and consequent diminished hypothalamus-pituitary-adrenal axis activity. To better test this hypothesis, future large MRI studies should investigate pituitary volumes in chronic schizophrenia longitudinally, also collecting pituitary hormones and cortisol, and comparing the effects of typical and atypical antipsychotics on pituitary size in a randomized trial.

Thin-slice three-dimensional gradient-echo magnetic resonance imaging of the pituitary gland in healthy dogs

OBJECTIVE

To evaluate thin-slice 3-dimensional gradient-echo (GE) magnetic resonance imaging (MRI) of the pituitary gland in healthy dogs.

ANIMALS

11 healthy dogs.

PROCEDURES

By use of a 0.2-Tesla open magnet, MRI of the skull was performed with T1-weighted GE sequences and various protocols with variations in imaging plane, slice thickness, and flip angle before and after administration of contrast medium; multiplanar reconstructions were made. The pituitary region was subjectively assessed, and its dimensions were measured. Image quality was determined by calculation of contrast-to-noise and signal-to-noise ratios.

RESULTS

Best-detailed images were obtained with a T1-weighted GE sequence with 1-mm slice thickness and 30 degrees flip angle before and after administration of contrast medium. Images with flip angles > 50 degrees were of poor quality. Quality of multiplanar reconstruction images with 1-mm slices was better than with 2-mm slices. The bright signal was best seen without contrast medium. With contrast medium, the dorsal border of the pituitary gland was clearly delineated, but lateral borders were more difficult to discern.

CONCLUSIONS AND CLINICAL RELEVANCE

MRI of the canine pituitary gland with a 0.2-Tesla open magnet should include a T1-weighted GE sequence with 1-mm slice thickness and flip angle of 30 degrees before and after administration of contrast medium. The neurohypophysis was best visualized without contrast medium. The MRI examination permitted differentiation between the pituitary gland and surrounding structures.

T1 signal hyperintensity in the sellar region: spectrum of findings

T1 signal hyperintensity is a common finding at magnetic resonance imaging of the sellar region. However, this signal intensity pattern has different sources, and its significance depends on the clinical context. Normal variations in sellar T1 signal hyperintensity are related to vasopressin storage in the neurohypophysis, the presence of bone marrow in normal and variant anatomic structures, hyperactive hormone secretion in the anterior pituitary lobe (eg, in newborns and pregnant or lactating women), and flow artifacts and magnetic susceptibility effects. Pathologic variations in T1 signal hyperintensity may be related to clotting of blood (in hemorrhagic pituitary adenoma, pituitary apoplexy, Sheehan syndrome, or thrombosed aneurysm) or the presence of a high concentration of protein (Rathke cleft cyst, craniopharyngioma, or mucocele), fat (lipoma, dermoid cyst, lipomatous meningioma), calcification (craniopharyngioma, chondroma, chordoma), or a paramagnetic substance (manganese, melanin). After treatment, T1 signal hyperintensity may result from the presence of materials used for surgical packing (gelatin sponge, fat); from compression of the cavernous sinus and reduction of the venous flow, caused by overpacking of the operative bed; or from hormone hypersecretion by a remnant of normal tissue in the anterior lobe of the pituitary gland.

Long-Term Evolution of Endocrine Disorders and Effect of GH Therapy in 35 Patients with Pituitary Stalk Interruption Syndrome

We report long-term evolution of endocrine functions and the results of GH treatment in 35 patients (26 male and 9 female) with pituitary stalk interruption. At diagnosis, mean chronological age was 4.8 +/- 2.7 years, mean SDS for height -3.1 +/- 0.8 with a bone age retardation of 2.3 +/- 1.3 years and a mean SDS for growth velocity of -0.5 +/- 1.1; 80% presented complete GH deficiency (GHD) and 20% partial GHD; thyroid deficiency was present in 47.1% of children with complete GHD but absent in all partial GHD. Diagnosis was made during the first months of life in only 2 patients while 23% presented with severe neonatal distress; neonatal signs were only observed in the group with pituitary height below 2 mm (45.7% of patients). GHD was isolated in 40.6% of patients below 10 years while multiple hormone deficiencies was consistent at completion of growth in all patients. Height gain was significantly higher in patients who started GH treatment before 4 years (p = 0.002). GH treatment is very effective: in 13 patients, final height was -0.4 +/- 1.0, total height gain 3.2 +/- 1.2 and distance to target height -0.3 +/- 1.6 SDS.

MRI of the hypothalamic-pituitary axis in children

In childhood, the MR characteristics of the normal pituitary gland are well established. During the first 2 months of life the adenohypophysis demonstrates high signal. Pituitary gland height (PGH) decreases during the 1st year of life and then increases, reaching a plateau after puberty. The magnetization transfer ratio (MTR) increases in both sexes up to the age of 20 years. On dynamic contrast-enhanced studies, the posterior pituitary lobe enhances simultaneously with the straight sinus, and the adenohypophysis later, but within 30 s. In genetically determined dysfunctional states, the adenohypophysis may be normal, hypoplastic, or enlarged. Pituitary enlargement, observed in Prop 1 gene mutations, is characterized by a mass interposed between the anterior and posterior lobes. An ectopic posterior lobe (EPP), associated with a hypoplastic or absent pituitary stalk, may be observed in patients with hypopituitarism. Tumors of the hypothalamic-pituitary (HP) axis may be the origin of adenohypophyseal deficiencies. A small hypo-intense adenohypophysis is found in iron overload states and is often associated with hypogonadotrophic hypogonadism. Absence of the posterior lobe bright signal, with or without a thick pituitary stalk or a mass at any site from the median eminence to the posterior pituitary lobe, may be found in diabetes insipidus. Hydrocephalus, suprasellar arachnoid cysts, hypothalamic hamartomas and craniopharyngiomas may result in central precocious puberty (CPP). Increased PGH in girls with idiopathic CPP is useful for its differential diagnosis from premature thelarche (PT). Pituitary adenomas, observed mainly in adolescents, present the same MR characteristics as those in adults.

The Pituitary Gland: Changes on MR Images During the 1st Year after Delivery

PURPOSE

To longitudinally and prospectively investigate changes in the volume and signal intensity on T1-weighted magnetic resonance (MR) images of the pituitary gland up to 1 year after delivery and evaluate whether termination of lactation has an effect on these parameters.

MATERIALS AND METHODS

All participants provided informed consent for participation in the study, which was approved by the institutional review board. Thirteen volunteers (mean age, 28 years; age range, 26-32 years) underwent MR imaging 2 and 4 weeks after delivery and then at intervals of 0.5-2.0 months until 1 year after delivery. Eight participants terminated lactation during the study period. Sagittal and coronal T1-weighted images were obtained. Signal intensities of the anterior and posterior lobes of the pituitary were calculated relative to that of the pons. The volume of the pituitary was also calculated. Two-tailed paired Student t tests and separate simple linear regression analyses were used to test for statistically significant differences.

RESULTS

The mean pituitary volume was 544 mm3 at 2 weeks, 523 mm3 at 4 months, 512 mm3 at 8 months, and 511 mm3 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .002) and between 4 and 8 months (P = .003) after delivery. The mean ratio of the signal intensity of the anterior lobe of the pituitary to the signal intensity of the pons was 1.11 at 2 weeks, 1.07 at 4 months, 1.03 at 8 months, and 1.00 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .004) and between 4 and 8 months (P = .0001) after delivery. Termination of lactation had no statistically significant effect on pituitary volume or the ratio of the signal intensity of the anterior or posterior lobe of the pituitary to the signal intensity of the pons.

CONCLUSION

The volume of the pituitary gland decreases up to 8 months after delivery, and the T1-weighted signal intensity of the anterior lobe of the pituitary decreases; termination of lactation has no statistically significant effect on these parameters.

Pituitary gland signal in pre-term infants during the first year of life: an MRI study

Our purpose was to determine the pituitary gland signal of premature neonates and infants. We retrospectively measured, in a midline sagittal T1-weighted MRI scan, the pituitary signal of 121 premature infants (mean gestational age: 32.8 weeks, mean chronological age: 6.9 months, mean corrected age: 5.2 months). The relative signal intensity of the adenohypophysis and neurohypophysis was measured as (A-V)/V and (P-V)/V, respectively (where A, P, V are the mean signal intensities of the adenohypophysis, neurohypophysis and vermis white matter, respectively). On visual inspection the adenohypophysis was rated relative to the vermis white matter (VWM) and scored as hyperintense (grade 3), isointense (grade 2) and hypointense (grade 1). (A-V)/V and (P-V)/V had a negative correlation with chronological age (r=-0.38, r=-0.35, respectively, P<0.01) and corrected age (r=-0.42, r=-0.40, respectively, P<0.01). The (A-V)/V was different in the three grade groups; significant difference was found between grades 3 and 2 and grades 3 and 1. The adenohypophysis was bright in 93% of babies under 2 months of chronological age. In five babies of mean gestational age 29.1 weeks a hyperintense adenohypophysis was observed at 2.9-3.7 months of chronological age (corrected age 0.37-2 months). We conclude that in pre-term babies the adenohypophysis appears in hypersignal that may persist up to 2 months of corrected age. The adenohypophyseal and neurohypophyseal signals decrease with age.

Serial MR intensity changes of the posterior pituitary in patients with diabetes insipidus after transsphenoidal surgery for pituitary adenomas: report of two cases

This is the first report describing magnetic resonance (MR) intensity changes of the posterior pituitary gland in the patients suffering from the classical "triphasic" diabetes insipidus (DI) after transsphenoidal surgery for pituitary adenomas. A 21-year-old female and a 54-year-old female were admitted to our hospital with the diagnosis of Cushing's disease and acromegaly due to pituitary microadenomas, respectively. No evidence of DI was found, and T1-weighted MR images exhibited "bright spot" corresponding to the posterior pituitary in both cases. Both experienced the classical "triphasic" pattern of water metabolism disturbance after successful transsphenoidal resection of pituitary adenomas, that is, polyuria-oliguria-polyuria. The MR signal hyperintensity in posterior pituitary was detected during the first polyuric phase, but the hyperintensity disappeared during the second polyuric phase. In addition, "bright spot" was restored along with the recovery from DI in the chronic phase. These findings of serial MR images supported that the first DI phase of the classical triphasic course of water metabolism disturbance was caused by secretional dysfunction of stored vasopressin from the posterior gland, whereas the second DI phase was due to impairment in the functional integrity producing vasopressin-containing granules after depletion of vasopressin in the oliguric phase.

Bright pituitary stalk on MR T1-weighted image: damming up phenomenon of the neurosecretory granules

Characteristic findings of the pituitary stalk on magnetic resonance (MR) imaging, which suggest a damming-up phenomenon of neurosecretory granules, were reported. Neurosecretory granules containing vasopressin influence the signal intensity on MR T1-weighted image (T1WI). The normal posterior lobe of the pituitary gland appears as a bright signal on T1WI. The bright signal of the posterior lobe represents the normal content of neurosecretory granules and disappears in patients with central diabetes insipidus. The normal pituitary stalk appears as a low-intermediate intensity signal on sagittal and coronal T1WIs with 3 mm-slice thickness. The pituitary stalk appeared as a bright signal in 20 patients; 13 with pituitary adenoma, 4 with an intrasellar cystic lesion, one with cavernous sinus mass, and 2 with no abnormal MR findings. The pituitary stalk was not severed in any of the cases. The normal bright signal of the posterior lobe disappeared in 17 patients. No patients suffered from symptoms of central diabetes insipidus when the bright pituitary stalk appeared. It is suggested that the origin of the bright signal in the pituitary stalk is the damming up and accumulation of neurosecretory granules in the nerve fibers of the hypothalamohypophyseal tract obstructed by adenoma, postoperative scarring, cystic mass and so on. Probably, the damming-up phenomenon on MR imaging represents the functional integrity of the hypothalamo-neurohypophyseal system, and should be distinguished from an ectopic posterior lobe formation which is caused by stalk transection.

High signal intensity of the posterior pituitary gland on T1-weighted MR images. Correlation with plasma vasopressin concentration to water deprivation

PURPOSE

To evaluate the effect of water deprivation on the signal intensity of the posterior pituitary gland on T1-weighted MR images and correlate the signal intensity with the plasma vasopressin concentration.

MATERIAL AND METHODS

Fifteen rabbits were studied: Group 1 (n=10) was deprived of water for 9 days and Group 2 (n=5) was replenished water for 7 days after 7-day water deprivation. MR imaging and plasma vasopressin measurement by radioimmunoassay were made before and after water deprivation and replenishment. Sequential changes of the signal intensity ratio of the posterior lobe to the pons and plasma vasopressin concentration were correlated.

RESULTS

Before water deprivation, the hyperintense posterior lobe was demonstrated in all rabbits. During water deprivation, the signal intensity ratio decreased and vasopressin concentration increased gradually. On the contrary, the signal intensity ratio increased and vasopressin concentration decreased with water replenishment. The signal intensity ratio correlated well with the plasma vasopressin concentration (p<0.05).

CONCLUSION

There was a negative, linear correlation between the signal intensity ratio of the posterior pituitary gland on T1-weighted MR images and plasma vasopressin concentration to water deprivation. The results support that the high signal intensity of the posterior pituitary gland on T1-weighted MR images is attributed to the normal content of vasopressin-neurosecretory granules.

Analysis of indirect signs of microprolactinoma at MR imaging

OBJECTIVE

To evaluate the diagnostic reliability/value of microprolactinoma indirect signs at MRI.

METHODS AND MATERIAL

A prospective study was carried out over 3 years on 26 women with microprolactinoma (MiP group) and 106 healthy female volunteers as a control group. Size, glandular morphology, pituitary stalk inclination and sellar bony floor erosion were measured and a comparative statistical analysis between both groups was performed.

RESULTS

Patients from the MiP group showed a significantly bigger glandular size than women in the control group, although the glandular morphology did not present significant differences between both groups. Only 5% of normal glands measured over 7.5 mm in height and none of them reached 9 mm, while up to 42.3% of the MiP group scored over 7.5 mm and 19.2% over 9 mm. Mean stalk inclination for the MiP group was 4.6 +/- 3.1 degrees and 3.5 +/- 2.7 degrees for the control group with no significant differences. Five microprolactinomas were located on the glandular midline, 11 on the left side and ten on the right side. No relationship between the microadenoma location inside the gland and stalk inclination was found. From 21 microprolactinomas with eccentric location, 17 coincided with the sellar floor excavation; eccentric excavation presented significant differences between both groups, but not the central excavation.

CONCLUSION

From all indirect sings of microprolactinoma analyzed in this study, only a gland height over 9 mm, and an eccentric sellar excavation of at least 3 mm are reliable signs to support its diagnosis.

[Pituitary stalk transection syndrome]

BACKGROUND

Pituitary stalk transection is a non-negligible cause of growth hormone (GH) deficiency.

POPULATION AND METHODS

We studied 22 children (13 boys, nine girls) aged at the first clinical manifestations from 2 days to 10 years (average = 5.33 +/- 2 years). Pituitary stalk transection was assessed by the means of magnetic resonance imaging (MRI). The children's past history showed fetal distress in 12 cases (54.5%), cranial trauma in three (13%) and a midline anomaly in three (13%). The first clinical manifestations were neonatal hypoglycemia (two cases), decreased growth velocity (18 cases) and diabetes insipidus (two cases).

RESULTS

GH deficiency was complete, present from the onset in 19 of 22 cases and isolated in four. Fifteen of 22 cases had adreno-corticotrophic hormone (ACTH) and thyroid stimulating hormone (TSH) deficiency. Diabetes insipidus was present in six cases and revealed the syndrome in two. All children older than normal age of puberty (n = 10) had gonadotropin deficiency. In our study, these hormonal anomalies progressed from isolated GH deficiency to multiple hormonal deficiencies.

CONCLUSION

The recently described stalk transection syndrome is relatively frequent and should be suspected after cranial trauma or fetal distress syndrome. The outcome is progressive evolution towards panhypopituitarism and these patients require regular clinical survey and hormonal controls.

Magnetization transfer imaging of the pituitary: further insights into the nature of the posterior "bright spot"

PURPOSE

After more than a decade of investigation, the chemical nature of the posterior pituitary "bright spot" remains elusive. Speculations into the source of this high signal have included relaxation of water by phospholipid vesicles, vasopressin, paramagnetic substances, and membrane-associated proteins. We hypothesized that if the T1 shortening observed in this structure were caused by water/macromolecular interactions, this interaction could be modulated by the use of magnetization transfer (MT) saturation.

METHOD

Twenty-five normal subjects were recruited over a 2 month period who were identified on routine T1 sagittal head images to have pituitary bright spots with cross-sectional area of > 2 mm2. Thin section (4 mm), T1-weighted (SE 450/20) sagittal MR images were obtained both with and without the use of an MT suppression pulse (1,000 Hz offset, 200 Hz bandwidth, peak amplitude 7.3 microT). Region-of-interest measurements were made of the posterior pituitary lobe, anterior pituitary lobe, genu of corpus callosum, and pons, with MT ratios (MTRs) calculated for each structure.

RESULTS

Relatively low (and similar) MTRs were observed in both parts of the pituitary gland: anterior lobe, 12.3%; posterior lobe 10.8%. Paired t test analysis demonstrated no statistically significant difference between the MTRs of the anterior and posterior pituitary lobes (p = 0.23). Considerable suppression of signal was noted in the genu (MTR = 25.0%) and pons (MTR = 21.9%). The MTRs of both portions of the pituitary differed significantly from those of the genu and pons (p < 0.00001).

CONCLUSION

The high signal of the posterior pituitary gland suppresses only slightly on MT images, having a behavior similar to that in the anterior lobe but significantly different from the rest of the brain. These findings suggest that direct water/macromolecule, water/membrane, or water/phospholipid interactions are not likely to be responsible for the appearance of the bright spot. The experimental results are more consistent with water interacting with a paramagnetic substance or low molecular weight molecule (e.g., vasopressin, neurophysins).

Optic nerve hypoplasia: absence of posterior pituitary bright signal on magnetic resonance imaging correlates with diabetes insipidus

PURPOSE

Magnetic resonance imaging has been used to examine children with optic nerve hypoplasia for pituitary abnormalities who may be at risk for anterior pituitary hormonal deficiencies. We correlated the sellar and optic pathway anatomic findings on magnetic resonance imaging in children with optic nerve hypoplasia with findings from their endocrinologic and ophthalmologic examinations to determine whether magnetic resonance imaging findings predict anterior and posterior pituitary dysfunction.

METHODS

A retrospective review identified five children with optic nerve hypoplasia and endocrinopathy who also underwent high resolution volumetric magnetic resonance imaging.

RESULTS

All children had severe bilateral optic nerve hypoplasia and anterior pituitary hormone deficiencies. Three children had no recognizable intrasellar or ectopic posterior pituitary bright spot on magnetic resonance imaging; all had clinical evidence of diabetes insipidus. Two patients with a recognizable but ectopic posterior pituitary did not have diabetes insipidus.

CONCLUSION

Children with optic nerve hypoplasia and no recognizable posterior lobe of the pituitary gland on magnetic resonance imaging are at risk for both anterior and posterior pituitary dysfunction, whereas those with a posterior lobe on magnetic resonance imaging appear to have intact posterior pituitary function.

The pituitary gland in nocturnal enuresis: MR findings

Nocturnal enuresis is considered a benign condition partially explained by a defect circadian rhythm of vasopressin. An organic cause may be responsible for an abnormal pituitary function, when enuresis persists into adulthood. In the present study the pituitary gland and surroundings of 8 adults suffering from primary monosymptomatic nocturnal enuresis were studied by magnetic resonance imaging. The pituitary gland appeared normal in all, except from a Rathke's cleft cyst observed in one patient. This cleft cyst was not considered to be clinically important. It was concluded, that severe nocturnal enuresis persisting into adulthood is not likely to be combined with detectable pathology on magnetic resonance imaging of the pituitary gland.

Displacement of the normal pituitary gland by sellar and juxtasellar tumours: surgical-MRI correlation and use in differential diagnosis

We compared the position of the normal pituitary gland as estimated by gadolinium (Gd)-DTPA-enhanced MRI, with its position at surgery in 40 patients with intra- and juxtasellar tumours: 22 pituitary adenomas, 4 craniopharyngiomas, 7 meningiomas, 2 germinomas, and 5 Rathke cleft cysts. In 37 of these, the normal gland showed more intense contrast enhancement than the adjacent tumour, from which it could be differentiated by Gd-DTPA-enhanced MRI, especially in the sagittal plane. The direction of displacement of the normal pituitary gland correlated well with tumour type, so that its position proved helpful in the differential diagnosis. The normal gland was typically displaced superiorly by pituitary adenomas, inferiorly by craniopharyngiomas, and anteriorly by germinomas. It showed variable displacement by Rathke cleft cysts, and was not usually displaced by meningiomas.

MRI of pituitary adenomas: the position of the normal pituitary gland

The position of the normal pituitary gland, assessed using gadolinium - enhanced MRI was compared with the position found at surgery for pituitary adenoma in 25 patients. The tumours were five microadenomas and 20 macroadenomas. Using T1-weighted imaging, the anterior lobe could be differentiated on the sagittal image in five patients (20%) and on the coronal image in four (16%). The high intensity of the posterior lobe could be differentiated using T1-weighted sagittal imaging in 13 patients (52%). The normal pituitary gland, which enhanced more strongly than tumour, could be differentiated using Gd-DTPA-enhanced MRI on the sagittal images in 22 cases (88%) and on the coronal image in 17 (68%). In seven patients, the normal pituitary gland surrounded the tumour; it was displaced superiorly in 14 cases and superioposterorly in two but in no case was it displaced anteriorly or downwards.

A clinical and histopathological study of factors affecting MRI signal intensities of pituitary adenomas

Our aim was to elucidate the factors which determine the MRI signal intensities of pituitary adenomas. We examined 51 patients with surgically-confirmed pituitary adenomas. Using a spin-echo pulse sequence (SE 500/15), coronal and sagittal images (3 mm slices) were obtained. Signal intensities on T1-weighted images were measured in the parenchyma of the adenoma and in normal grey matter. The relative intensity of the adenoma was assessed by calculating the ratio of its signal intensity to that of the normal grey matter of the same patient. Paraffin-embedded sections were used for haematoxylin and eosin staining. The number of cells in a prescribed area was counted, and the mean of five such counts was taken as the cell density. Immunohistochemically stained sections using antibodies for various pituitary hormones were similarly examined; the ratio of the total number of hormone-positive cells to the overall total number of adenoma cells was calculated. Four independent variables were used in the analysis: the age of the patient, the maximum diameter of the adenoma, the cell density and the proportion of hormone-positive cells in the adenoma and, with the signal intensity ratio as the dependent variable, a multiple regression analysis was performed. This revealed that the the greatest influence upon the signal intensities on T1-weighted images was the proportion of hormone positive cells.

Lymphocytic infundibuloneurohypophysitis as a cause of central diabetes insipidus

BACKGROUND

Central diabetes insipidus may be familial, secondary to hypothalamic or pituitary disorders, or idiopathic. Idiopathic central diabetes insipidus is characterized by selective hypofunction of the hypothalamic-neurohypophysial system, but its cause is unknown.

METHODS

We studied 17 patients with idiopathic diabetes insipidus, in whom the duration of the disorder ranged from 2 months to 20 years. Only four patients had been treated with vasopressin before the study began. All the patients underwent endocrinologic studies and magnetic resonance imaging (MRI) with a 1.5-T superconducting unit, and two patients had biopsies of the neurohypophysis or the pituitary stalk.

RESULTS

Nine of the 17 patients had thickening of the pituitary stalk, enlargement of the neurohypophysis, or both and lacked the hyperintense signal of the normal neurohypophysis. In the remaining eight patients, the pituitary stalk and the neurohypophysis were normal, although the hyperintense signal was absent. The abnormalities of thickening and enlargement were seen on MRI only in the patients who had had diabetes insipidus for less than two years, and the abnormalities disappeared during follow-up, suggesting a self-limited process. In addition to vasopressin deficiency, two patients had mild hyperprolactinemia and nine had impaired secretory responses of growth hormone to insulin-induced hypoglycemia. The two biopsies revealed chronic inflammation, with infiltration of lymphocytes (mainly T lymphocytes) and plasma cells.

CONCLUSIONS

Diabetes insipidus can be caused by lymphocytic infundibuloneurohypophysitis, which can be detected by MRI. The natural course of the disorder is self-limited.

Magnetic resonance and the diagnosis of short stature of hypothalamic-hypophyseal origin

Magnetic resonance imaging was performed in 23 patients with short stature (7 had multiple pituitary hormone defect, 11 had isolated growth hormone deficiency and 5 had normal variant short stature) to investigate if there is a relation between magnetic resonance findings and results of endocrine tests. Magnetic resonance imaging of patients with multiple pituitary hormone deficiency or with serious isolated growth hormone deficiency (growth hormone < 3 micrograms/l) revealed an interrupted pituitary stalk and ectopic neurohypophysis or a mass. In patients with less serious isolated growth hormone deficiency (growth hormone > 3 micrograms/l) or with normal variant short stature, the technique revealed a normal or hypoplastic hypophysis. Magnetic resonance appears to be a useful second-level diagnostic tool in defining the type of alteration in growth defects of endocrine origin.

Smith-Lemli-Opitz syndrome type II: report of a case with additional radiographic findings

A phenotypically female infant with 46-XY chromosomes was found to have Smith-Lemli-Opitz syndrome, type II a rare congenital malformation syndrome with many features of the more common classic Smith-Lemli-Opitz syndrome. The patient's skeletal survey revealed characteristic and previously undescribed skeletal anomalies which are reported. In addition a lipoma of the pituitary gland was found on magnetic resonance imaging. This lesion is particularly interesting given the hypothesized steroid abnormality in Smith-Lemli-Opitz, type II syndrome, the sexual ambiguity of males with this syndrome and the similarity of this syndrome to the Pallister-Hall syndrome which characteristically has a hamartoblastoma of the hypothalamus.

Magnetic resonance imaging in patients with hypopituitarism

In patients with hypopituitarism, magnetic resonance (MR) imaging of the hypothalamus and pituitary has disclosed a high incidence of hypoplasia of the anterior pituitary lobe, attenuation or transection of the pituitary stalk, and formation of an "ectopic" posterior pituitary lobe at the base of the hypothalamus. These anatomic abnormalities may be associated with other congenital malformations of the central nervous system, or may be due to an in utero toxic or infectious insult, perinatal trauma, neonatal asphyxia and hypoxia, head injury, or hemorrhage into a pituitary adenoma. The progressive development of defects in pituitary hormone secretion in such patients is probably due to continued atrophy of an anterior pituitary remnant with a limited vascular supply unstimulated by hypothalamic neuropeptides. By contrast, in patients with isolated hypogonadotropic hypogonadism, hypothalamic pituitary anatomy is normal, although abnormalities of the olfactory sulcus are present in patients with anosmia and hypogonadotropism (Kallmann syndrome). In most patients with central diabetes insipidus, the neurohypophysis is absent on MR scan.

MRI in diabetes insipidus due to metastatic breast carcinoma

Magnetic resonance imaging (MRI) has been established as a valuable imaging modality in the evaluation of pituitary disorders. We describe three women with known carcinoma of the breast, who presented acutely with biochemically proven diabetes insipidus (DI), in whom MRI was used as the primary investigative tool. The patients were studied using a 1.5T superconducting system, with gadolinium enhancement in two cases. All three had thickened pituitary stalks and two had complete loss of the normal high signal from the posterior lobe of the pituitary gland. Two also had enlargement of the anterior pituitary gland. One subject was also noted to have other metastases to the brain. All three had multiple secondary deposits elsewhere in the body and one had metastases to the clivus but without evidence of extension to the pituitary fossa. DI is uncommon in systemic cancers and anterior pituitary dysfunction much more so, due to the separate blood supply of the two lobes. Thickening of the stalk has not been found frequently in large autopsy series. In the clinical context of DI in a patient with a known primary tumour the loss of high signal from the posterior lobe and stalk thickening are indicative of infiltration by metastases. A pituitary mass or metastases to adjacent bones are not necessary for diagnosis.

Central diabetes insipidus resulting from a nonneoplastic tiny mass lesion localized in the neurohypophyseal system

With the advent of magnetic resonance imaging (MRI), the neurohypophyseal system can be clearly delineated and its functional integrity can be predicted. The authors describe seven cases of central diabetes insipidus (DI) that occurred spontaneously. MRI revealed that the normal hyperintensity of the pituitary posterior lobe, which has been thought to be the neurosecretory material containing antidiuretic hormone, was absent in all cases. In addition, enlargement of a part of the neurohypophyseal system was recognized in five of seven cases on MRI. Three of the five patients with enlargement of a part of the neurohypophyseal tract underwent biopsy and were demonstrated to have chronic inflammation of the neurohypophyseal system. It was demonstrated that the enlarged parts of the neurohypophyseal system had shrunk either spontaneously or after the biopsy in four of the five cases. All patients are alive and have not experienced progression or remission of the disease. This study indicates that some cases of idiopathic DI result from a tiny mass lesion, usually nonneoplastic, localized in the neurohypophyseal system.