Magnetic resonance imaging in diabetes insipidus

Imaging of the sella in the syndrome of inappropriate secretion of antidiuretic hormone

OBJECTIVE

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) results either from ectopic production or inappropriate release of antidiuretic hormone from the neurohypophysis. Although magnetic resonance imaging (MRI) has provided new insights into the morphological changes of the hypophysis in health and disease, no previous studies have evaluated its use in SIADH: The aim of this study was to evaluate the MRI appearance of the neurohypophysis in patients with SIADH:

DESIGN

Retrospective case-control study.

SETTING

Tertiary care teaching hospital.

SUBJECTS

We studied retrospectively eight patients with SIADH who had been hospitalized in Boston's Beth Israel between 1984 and 1994 and who had MRI scans including the sella turcica. We also evaluated prospectively the MRIs of the heads of 23 consecutive control patients who had no pituitary pathology and no serum osmolality or electrolyte abnormalities.

INTERVENTIONS

Clinical evaluation as well as sagittal and axial T1-MR images.

MAIN OUTCOME MEASURES

Presence or absence of the high intensity signal of the neurohypophysis.

RESULTS

In seven out of eight patients (87.5%) the normal high intensity signal of the neurohypophysis was not present. In one patient (12.5%), two interpreting radiologists disagreed about its presence. The high intensity signal was present in the neurohypophysis of 20 out of 23 controls (87.5%).

CONCLUSIONS

Our data indicate an association of SIADH with the absence of the normal hyperintense signal of the neurohypophysis, confirming the usefulness of MRI as a tool to visualize ADH processing. These data also raise the possibility that the absence of the high intensity signal may be useful diagnostic tool in cases of SIADH that are difficult to diagnose clinically. Additional studies to correlate this signal with various forms of SIADH will be needed.

Imaging of the sella: anatomy and pathology

The hypophysis cerebri, or pituitary gland, is a complex neuroendocrine organ involved in the control of a variety of homeostatic mechanisms. Subtleties in the internal anatomy of this gland are now becoming appreciated, such as the topographic arrangements of pituitary cell types and specializations in its regional microcirculation. A large number of potential lesions may affect the pituitary, including tumors (adenomas, Rathke cleft cysts, and craniopharyngiomas), inflammatory processes (adenohypophysitis, infections), and vascular lesions (apoplexy, infarction). Diseases isolated to the posterior lobe and stalk (eg, pituitary dwarfism, choristoma, diabetes insipidus) are also well recognized. Modern radiologic techniques like computed tomography (CT) and magnetic resonance (MR) imaging have provided new insights into the morphologic changes of the gland that occur both in health and in a variety of diseases. The picture of the gland that has emerged from this research is a dynamic one: The pituitary undergoes dramatic changes in size and shape throughout life that must be recognized when assessing it for pathologic change.

Pituitary stalk thickening with diabetes insipidus preceding typical manifestations of Langerhans cell histiocytosis in children

In up to 25% of cases of children with central diabetes insipidus no organic cause can be documented. We present three boys (age 2.2, 2.3 and 6 years at diagnosis) with acute onset central diabetes insipidus, in whom the only pathological finding using MRI was a thickened central part of the pituitary stalk (> 2.5 mm). Recent reports demonstrate similar MRI findings in adults with Langerhans cell histiocytosis (LCH), sarcoidosis, or tuberculosis, and in children with proven LCH and diabetes insipidus. In those adults with LCH, the pituitary stalk lesion has been histologically verified as a sequela of LCH. In contrast, in two of our three patients pituitary stalk thickening preceded the typical peripheral lesions of LCH by several months, whereas in the third patient there is as yet no evidence of systemic disease. We conclude that thickening of the central part of the pituitary stalk might represent the first manifestations of LCH clinically presenting with diabetes insipidus. MRI investigation of the pituitary stalk in children with unexplained central diabetes insipidus and accurate follow up in patients with thickening of the pituitary stalk in necessary to avoid missing other manifestations of a systemic disease.

Anterior pituitary function and computed tomography/magnetic resonance imaging in patients with Langerhans cell histiocytosis and diabetes insipidus

In order to document anterior pituitary dysfunction in patients with biopsy-proven Langerhans cell histiocytosis (LCH) and diabetes insipidus and to correlate this with structural changes on imaging, we performed an insulin tolerance test, enhanced computed tomography (CT), and unenhanced magnetic resonance imaging (MRI) in nine patients. Six of the nine patients had growth hormone deficiency, which in two patients was part of panhypopituitarism and in one was associated with poor cortisol response to insulin hypoglycemia. One patient had an exaggerated growth hormone response and one who had had neck irradiation as an infant, had a high resting thyroid stimulating hormone (TSH) suggesting compensated primary hypothyroidism. All enhanced CTs were abnormal, bony defects being the only abnormality in two patients and opaque mastoids in one. The remaining six patients all had structural changes in the hypothalamic/pituitary region. Unenhanced MRI confirmed the CT findings except in one child who had been treated with radiotherapy in the intervening period, but, in addition, confirmed diabetes insipidus by showing absence of the posterior pituitary bright signal and picked up white matter changes in a child with clinical neurological dysfunction. Our findings indicate that the development of diabetes insipidus in LCH is commonly associated with anterior pituitary dysfunction and is usually associated with structural changes in the hypothalamic/pituitary axis.

Alobar holoprosencephaly, diabetes insipidus and coloboma without craniofacial abnormalities: a case report

An infant is described with coloboma of the right eye, holoprosencephaly and diabetes insipidus without craniofacial malformations. The association is discussed in view of the development of the prosencephalon and its relation to the development of craniofacial structures.

Growth hormone deficiency in children: role of magnetic resonance imaging in assessing aetiopathogenesis and prognosis in idiopathic hypopituitarism

To search for the presence of morphostructural abnormalities of the hypothalamus-pituitary region in growth hormone deficient (GHD) children magnetic resonance imaging (MRI) was performed in 30 GHD patients (age 10.09 +/- 3.5 years) and in 15 healthy age-matched controls. MRI demonstrated a significantly small sella and pituitary volume compared to controls and normal literatures values. In 20 patients the structures were extremely small and an abnormal development of the pituitary stalk was observed, and in 18 of these patients the bright spot indicating the neurohypophysis was dislocated to the distal part of the maldeveloped stalk, although these children had a normal fluid balance. From a functional point of view hypothalamus and pituitary defects were equally distributed between the two morphological groups. The patients with multiple endocrine defects had the smallest pituitary volume and abnormal stalk. A possible pathogenetic role of perinatal trauma or dysembryogenic events are discussed. A careful follow up of patients with isolated GHD presenting MRI abnormalities of the pituitary is suggested for the possible evolution in panhypopituitarism.

Hypothalamic-pituitary dwarfism: comparison between MR imaging and CT findings

Magnetic Resonance (MR) imaging was carried out on 33 patients with idiopathic growth hormone deficiency, in 22 of whom CT scan had been carried-out previously. Twenty-one patients presented some complications at birth. Both MR and CT were positive in the evaluation of the sella. MR imaging exhibited a higher degree of accuracy than CT in the evaluation of pituitary gland, pituitary stalk and brain anomalies. On the basis of pituitary morphology demonstrated by MR imaging, and perinatal histories, a classification is proposed which divides our patients into three group: A) a first group of 13 patients presenting severe hypoplasia of the anterior pituitary lobe, hypoplasia of the stalk and ectopia of posterior lobe. The underlying cause of these anatomic defects might be developmental in origin, and date from early intrauterine life, probably worsened at birth. B) a second group of 10 patients presenting severe hypoplasia of the anterior pituitary lobe. A perinatal event and birth trauma might be responsible for pituitary damage. C) a third group of 10 patients with no morphological abnormalities of the pituitary gland. A derangement of the neuroendocrine mechanism which control the growth hormone secretion might account for these patients.

The frequency and natural history of diabetes insipidus in children with Langerhans-cell histiocytosis

Diabetes insipidus is a well-recognized complication of Langerhans-cell histiocytosis (histiocytosis X), but its frequency and natural history are not well defined. Of 52 children with histiocytosis whom we studied, 12 (23 percent) had diabetes insipidus. Only two children had diabetes insipidus at presentation with histiocytosis, but the cumulative risk that it would develop during the first four years after the presentation and diagnosis of histiocytosis was found to be 42 percent. Diabetes insipidus occurred most often among children with multisystem disease and those with proptosis. To determine the natural history of diabetes insipidus in children with histiocytosis, we measured the response of urinary arginine vasopressin to water deprivation every six months in 21 children who did not have diabetes insipidus and who had had histiocytosis for less than four years. Five of the 21 children (24 percent) had subnormal responses during the initial test. One subsequently had spontaneous improvement in the functioning of the posterior pituitary, and diabetes insipidus subsequently developed in two, as it did in one of the children who initially had normal function of the posterior pituitary. Two of the children received irradiation to the pituitary within two to four weeks after diabetes insipidus developed, but they had no improvement in pituitary function. However, diabetes insipidus improved transiently during prednisolone therapy in one of these children and improved permanently after etoposide therapy in another child. We conclude that prospective study with the use of a simple water-deprivation test will allow partial defects of posterior-pituitary function to be detected in patients with histiocytosis and will permit a more appropriate evaluation of the effects of therapeutic intervention.