Correlation between Magnetic Resonance Imaging of Posterior Pituitary and Neurohypophyseal Function in Children with Diabetes Insipidus
| Title: | Correlation between Magnetic Resonance Imaging of Posterior Pituitary and Neurohypophyseal Function in Children with Diabetes Insipidus |
|---|---|
| Authors: | Maghnie, Mohamad; Villa, Andrea; Arico, Maurizio; Larizza, Daniela; Pezzotta, Stefano; Beluffi, Giampiero; Genovese, Eugenio; Severi, Francesca |
| Publisher: | Journal of Clinical Endocrinology and Metabolism |
| Date Published: | April 01, 1992 |
| Reference Number: | 307 |
The posterior pituitary lobe and stalk were studied by magnetic resonance imaging in 20 children with diabetes insipidus of different origins: primary familial autosomal dominant (n = 2) or idiopathic (n = 2), and secondary to craniopharyngioma (n = 6, resected in 5), to Langerhans cell histiocytosis (n = 5), to excessive water intake (dipsogenic; n = 3), to renal vasopressin insensitivity (n = 1), and to osmoreceptor dysfunction (n = 1). Of the four children with primary diabetes insipidus, the posterior bright signal was recognizable in two with the familial autosomal dominant form and one with the idiopathic form; in the latter, the pituitary stalk was thin, while it was normal in the first two patients; no posterior hyperintense signal with enlarged and gadolinium-enhanced pituitary stalk was observed in the fourth. The posterior hyperintense signal was absent without evidence of ectopic posterior pituitary tissue regeneration in five children with surgically removed craniopharyngioma and was doubtful in the child with unresected craniopharyngioma; the stalk was unrecognizable in all patients. In the five children with Langherans cell histiocytosis, the posterior bright signal was absent, while the stalk was normal in two and unexpectedly enlarged in three (uniformly in two and mainly at the level of median eminence and hypothalamus in one). All five patients with dipsogenic or nephrogenic diabetes insipidus or osmoreceptor dysfunction had normal images of posterior pituitary lobe and stalk. Normal posterior pituitary bright signal and stalk were found in all 25 healthy control children. Plasma vasopressin was undetectable in all patients except in nephrogenic one, in the child with osmoreceptor dysfunction, and in two of three dipsogenic children, the third mimicking partial neurogenic diabetes insipidus.
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This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)
The antidiuretic hormone, arginine vasopressin (AVP) is formed by the neuronal cells of the hypothalamic nuclei and stored in the posterior lobe of the pituitary gland (neurohypophysis). AVP is necessary for the urine concentrating process. Diabetes insipidus (DI) is a condition where the normal urine concentrating process does not occur. As a result, patients with DI experience polyuria (chronic passage of large volumes of urine) and polydipsia (chronic, excessive thirst).
There are three different types of DI: pituitary D.I. (PDI), caused by a lack of AVP, often due to an injured hypothalamic-neurohypophyseal system. (Acquired PDI is most frequently due to surgical removal of a tumor in the hypothalamic-pituitary area. An organic lesion in this region may be due to inflammatory diseases.); nephrogenic DI (NDI), due to the inability of the kidneys to respond to AVP; primary polydipsia (PP), where the patient continually drinks excessive amounts of water for no known reason.
Maghnie, et al., performed MRI on a group of 20 children with DI and a control group of 25 normal children. They also monitored the subjects' AVP blood levels. Of the 20 DI patients: two had inherited PDI, two had PDI of unknown origin, 11 had PDI as a result of another disorder, three had PP, one had NDI and one had an osmoreceptor dysfunction. The authors wanted to describe the MR images of the 20 DI subjects, assess the role of MRI in diagnosing DI, and see if the functional hypothalamic-neurohypophyseal defect associated with PDI has an anatomical basis.
The bright spot recognizable as the posterior pituitary lobe could be detected in the two patients with inherited PDI and the one patient with PDI from unknown causes. The pituitary stalk was normal in the first two and thin in the third. The bright spot (i.e. the hyperintensive signal on the MRI) was undetectable in five of the patients with PDI due to craniopharyngioma and doubtful in the sixth patient with PDI due to this disease. The pituitary stalk was undetectable in all six. The five patients with PDI due to Langerhans cell histiocytosis (LCH) showed no bright spot. The pituitary stalk was enlarged in three of them and normal in two. The bright spot was observed in the three PP patients, the NDI patient, the subject with osmoreceptor dysfunction and the 25 controls. In these cases, the pituitary stalk was also normal.
The authors conclude that:
- The absence of the bright spot in PDI patients is associated with lesions in the hypothalamic-neurohypophyseal axis.
- The absence of the bright spot correlates closely with undetectable plasma AVP only if there is an organic lesion in the hypothalamic-neurohypophyseal tract.
- Even when a bright spot is registered through MRI in DI patients, it does not indicate that the hypothalamic-neurohypophyseal axis is functioning.
- The release of stored AVP may be impaired in some cases of inherited PDI as well as in the DI of unknown origin.
- Evidence of isolated enlarged stalk in children with acute onset of diabetes insipidus suggests that MRI may be useful for the recognition of a preclinical phase of systemic disorders affecting the hypothalamic-neurohypophyseal tract.
This might help clarify both the natural history of anatomical and functional alterations in the course of DI and the origin of some cases of DI of unknown causes. In some cases, MRI, by providing a clear definition of pituitary stalk alteration as a precocious manifestation of LCH, could provide noninvasive diagnosis and lead to early specific treatment in such patients.