High signal intensity of the infundibular stalk on fluid-attenuated inversion recovery MR.

PURPOSETo determine the MR imaging characteristics of the pituitary stalk with a fluid-attenuated inversion recovery (FLAIR) technique.METHODSWe retrospectively studied the prevalence of a high-signal infundibular stalk on FLAIR MR images of the brain in 133 patients and compared this finding with the patients'' ages. To understand the cause of the high signal intensity of the pituitary stalk on FLAIR images, we calculated the T1, T2, and proton-density values in regions of gray matter, white matter, and the pituitary stalk in nine cases.RESULTSFLAIR images showed the pituitary stalk as having high signal intensity in 97 (73%) of 133 cases; however, in 11 of 16 patients less than 10 years old, the infundibular stalk was not of high signal intensity. In patients with a high-signal pituitary stalk on FLAIR images, the T2 value of the pituitary stalk was longer than that of gray or white matter.CONCLUSIONHigh signal intensity of the infundibular stalk was frequently seen on FLAIR MR images of the brain at all ages. A prolonged T2 value of the pituitary stalk caused the high signal intensity, presumably reflecting the fluid component of the pituitary stalk.     

Pituitary stalk meningioma: case report

We report a 45-year-old woman with a meningioma which was in contact with only the pituitary stalk on MRI. As the pituitary stalk has no dura mater, we suggest this tumour may have originated from the arachnoid membrane of the pituitary stalk. Though some reports have shown that meningiomas can arise from sites lacking a dural component, this is the first report of a meningioma originating from the pituitary stalk. Received: 21 December 1995 Accepted: 26 February 1996     

CT of the normal pituitary stalk

A prospective study assessed the size and frequency of visualization of the normal pituitary stalk on high-resolution computed tomography (CT). The normal pituitary stalk can be seen on the vast majority of high-resolution scans obtained with thin sections and intravenous contrast material. The upper size limit of the normal pituitary stalk is 4 mm at the level of the dorsum sellae and 4.5 mm above the dorsum. Stalks larger than this should be viewed with suspicion. Comparison of the size of the pituitary stalk with that of the nearby basilar artery is possible on most CT scans, providing a convenient and reliable visual check of the size of the stalk.     

Ectopic neurohypophisis in a boy: A case report and review

Ectopic neurohypophysis is rare anomaly which is characterized by ectopic location of posterior pituitary lobe (neurohypophysis), pituitary stalk abnormalities and association with dysfunction of anterior lobe related with growth hormone or with multiple dysfunction of the same.We present a rare case of posterior ectopic pituitary and pituitary stalk hypoplasia isolated in 2 year-old male patient.     

MR imaging of the pituitary stalk: size, shape, and enhancement pattern.

The size, shape, signal intensity, and enhancement pattern of the normal pituitary stalk were determined retrospectively by review of MR images of 58 patients. The pituitary stalk was measured at the level of the optic chiasm and at its insertion on the pituitary gland. The contour of the stalk was smoothly tapering, measuring 3.25 +/- 0.56 mm in transverse diameter at the optic chiasm and 1.91 +/- 0.40 mm at its pituitary insertion. The signal intensity of the pituitary stalk on unenhanced T1-weighted images was less than that of the neurohypophysis in all cases and less than that of the optic chiasm in 84% of the cases. After the administration of contrast material, enhancement of the pituitary stalk occurred in all cases. A central area of nonenhancement in an otherwise uniformly enhancing stalk was variably present, depending on the size of the infundibular recess. Our study defines the size, contour, and MR signal characteristics of the normal pituitary stalk. These criteria can be used to distinguish the normal from the abnormal stalk.     

Normal pituitary stalk size in children: CT study

A retrospective study was undertaken of 1005 normal contrast-enhanced head computed tomographic (CT) scans in children to determine normal standards for pituitary stalk diameter, basilar artery diameter, and their ratio for age and gender. The pituitary stalk enlarges with age, and girls have larger stalks than do boys after age 8. The pituitary stalk-to-basilar artery ratio is easily estimated visually. Ratios greater than or equal to 1 are unusual in normal children. A ratio greater than or equal to 1 should prompt direct measurement of the stalk and comparison with age-matched normal values. If the stalk measurement is greater than 2 SD above the age-matched mean, it is presumably abnormal and deserves further evaluation for numerous possible pathologic conditions including histiocytosis X, pituitary adenoma, hypothalamic lesions, Rathke cleft cysts, metastases, sarcoidosis, hypothyroidism, and infection.     

垂体柄阻断综合征的MRI表现

目的讨论垂体柄阻断综合征的MRI特点。资料与方法回顾性分析临床及MRI诊断的18例垂体柄阻断综合征患儿的影像及临床资料。结果 18例患者垂体前叶明显变薄,垂体柄缺如16例,2例垂体柄纤细,垂体后叶短T1信号未见,下丘脑漏斗处有短T1信号。实验室检查均有生长激素和(或)其他激素的缺乏。结论垂体柄阻断综合征多发生于男性,有典型的MRI表现。     

MR of the hypothalamic-pituitary axis in Langerhans cell histiocytosis.

PURPOSE: To describe the MR findings in the hypothalamic pituitary area in children with Langerhans cell histiocytosis and to define those MR alterations especially associated with the risk of developing diabetes insipidus. METHODS: The hypothalamic-neurohypophyseal axis was studied by sagittal and coronal 1.5 T1-weighted MR imaging in 14 children with Langerhans cell histiocytosis (five with diabetes insipidus) and in 28 low-stature controls, ages 6-14 years. RESULTS: The pituitary stalk was thicker in seven/14 patients (three with diabetes insipidus) than in controls (P less than .05). Bright posterior pituitary signal was undetectable in children with diabetes insipidus and in one/9 without diabetes insipidus. CONCLUSIONS: Thickening of the hypothalamus and/or the pituitary stalk in the absence of the posterior pituitary bright signal is seen in children with Langerhans cell histiocytosis with overt diabetes insipidus. Those Langerhans cell histiocytosis patients without diabetes insipidus but showing thickened stalk with or without posterior pituitary bright signal could be at high risk to develop diabetes insipidus.     

3D dynamic pituitary MR imaging with CAIPIRINHA: Initial experience and comparison with 2D dynamic MR imaging

Objectives

To evaluate the validity of 3D dynamic pituitary MR imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), with special emphasis on demarcation of pituitary posterior lobe and stalk.

Methods

Participants comprised 32 patients who underwent dynamic pituitary MR imaging due to pituitary or parasellar lesions. 3D dynamic MR with CAIPIRINHA was performed at 3 T with 20-s-interval, precontrast, 1st to 5th dynamic images. Normalized values and enhanced ratios (dynamic postcontrast image values divided by precontrast ones) were compared between 3D and 2D dynamic MR imaging for patients with visual identification of posterior lobe and stalk.

Results

In 3D, stalk was identified in 29 patients and unidentified in 3, and posterior lobe was identified in 28 and unidentified in 4. In 2D, stalk was identified in 26 patients and unidentified in 6 patients, and posterior lobe was identified in 15 and unidentified in 17. Normalized values of pituitary posterior lobe and stalk were higher in 3D than 2D (P < 0.001). No significant difference in enhancement ratio was seen between 3D and 2D.

Conclusions

3D dynamic pituitary MR provided better identification and higher normalized values of pituitary posterior lobe and stalk than 2D.     

Correlation of high signal intensity of the pituitary stalk in macroadenoma and postoperative diabetes insipidus

BACKGROUND AND PURPOSE: High signal intensity (HSI) at the pituitary stalk is reported in pituitary adenomas. Our purpose was to clarify how and when this HSI formed, its long-term fate, and its relation to the function of infundibuloneurohypophyseal (INH) system. METHODS: Twenty-two patients with pituitary adenoma and supradiaphragmatic extension underwent 1.5-T MR imaging. Patients were assigned to two groups A (n = 18; those with stalk tip HSI) and B (n = 4; those without HSI) on postoperative T1-weighted images. Endocrine status was postoperatively evaluated and compared in both groups. RESULTS: Group A patients did not have postoperative permanent diabetes insipidus (DI). Preoperative images in 17 patients revealed linear or ovoid HSI on the adenoma surface immediately above the diaphragma sellae. Of these, two with a poorly developed diaphragma sellae had HSI near the median eminence and inside the sella turcica. HSI was not apparent in the remaining patient with a giant, irregularly shaped adenoma. In group B, three patients had permanent DI. No patient had HSI on preoperative images. CONCLUSION: Postoperative pituitary stalk HSI is derived from preoperative supradiaphragmatic HSI on the adenoma surface. The suspected mechanism is blockage of the hypophyseal-pituitary axis, with an accumulation of neurosecretory granules at the diaphragmatic level. Diaphragmatic shape may influence the location of HSI. The shape and location of HSI are essentially stable for years after surgery. No patients with permanent DI had HSI before or after surgery. HIS at the pituitary stalk tip is a useful landmark for predicting functional integrity of the INH system in patients with a large pituitary adenoma.     

中枢性尿崩症的MR影像诊断(附65例分析)

目的：分析中枢性尿崩症（ＣＤＩ）的ＭＲ表现，探讨ＭＲ在ＣＤＩ的影像诊断中的价值及限度。材料与方法：对１９９６－０６～１９９６－０７间所确诊的６５例ＣＤＩ患者的ＭＲ资料和临床资料进行了回顾性分析。结果：１、ＭＲ表现：鞍内／鞍上肿块１６例；垂体柄断裂或显示不清１４例；垂体柄增粗１０例；垂体柄结节５例；垂体后叶高信号消失５８例。２、引起ＣＤＩ的病因：头颅损伤６例；颅内肿瘤１７例；Ｌａｎｇｅｒｈａｎ＇ｓ组织细胞增生症２例；特发性ＣＤＩ１７例。有２３例继发性ＣＤＩ的病因未经病理证实。结论：低场强（０．３Ｔ）的ＭＲ机器能够清楚地显示下丘脑－垂体区的病变，对ＣＤＩ病因的诊断和治疗具有重要的价值，但对肿瘤及炎性病变的定性诊断有一定的限度，同时认为临床上划分的部分性ＣＤＩ和完全性ＣＤＩ的ＭＲ影像表现不存在差别。     

Enlargement of the proximal pituitary stalk associated with spontaneous recovery from multiple pituitary hormone deficiencies

We report the case of a child with multiple pituitary hormone deficiencies and a truncated pituitary stalk on MR imaging who had recovery of normal secretion of pituitary hormones in early adulthood. Follow-up MR imaging examination after recovery revealed marked enlargement of the proximal pituitary stalk. The case of our patient helps to explain the mechanism whereby some patients experience recovery of hormonal function.     

Dynamic enhancement MRI of anterior lobe in pituitary dwarfism

We examined 23 patients with pituitary dwarfism by dynamic MRI; with a repetition time of 150 or 50 ms. The time-enhancement difference curves of selected regions in the anterior lobes were plotted. Another 48 patients with no definite clinical pituitary disfunction were examined with the same technique. We found that the intensity of maximum enhancement in both groups was similar, but the time to achieve maximum enhancement was delayed in pituitary dwarfism with or without stalk transection; the time seemed longest with stalk transection. There was little difference in enhancement between patients with multiple hormone deficiency or isolated growth hormone deficiency. Dynamic MRI of the anterior lobes may be an important functional imaging study, and our results imply that poor perfusion is a useful finding in pituitary dwarfism, especially in patients without stalk transection and normal pituitary height.     

CT of the abnormal pituitary stalk

Seven cases are presented in which enlargement of the pituitary stalk was demonstrated by computed tomography (CT). Histiocytosis X, sarcoidosis, and metastatic cancer were the proven or presumed causes. The discovery of pituitary stalk enlargement prompted radiation treatment in three patients and led to the diagnosis of previously unsuspected diabetes insipidus in one.     

垂体柄阻断综合征的影像学诊断

目的分析垂体柄阻断综合征的CT及MRI表现,提高对其的认识及诊断水平。方法回顾性分析4例垂体柄阻断综合征患者的影像学及临床资料。结果4例患者中,2例CT及4例MRI垂体柄均未见显示,垂体窝内垂体后叶高信号均消失,4例均在第三脑室漏斗隐窝可见高信号小结节。结论MRI是确诊垂体柄阻断综合征最有效的影像学检查方法。     

Magnetic resonance imaging in patients with panhypopituitarism

Primary panhypopituitarism consists of functional deficiency of the anterior pituitary lobe, which appears during infancy or adolescence. The magnetic resonance findings in 10 patients with a history of primary hopopituitarism are presented. The findings include: reduced pituitary size in all cases: partially (8 cases) or totally (2 cases) empty sella; thin (4 cases), partially visible (3 cases) or absent (2 cases) pituitary stalk; absence of the posterior lobe in 9 cases: bright spot corresponding to an ectopic posterior lobe in 8 cases. These findings are similar to those already reported in pituitary dwarfism and may help under-genesis of the pathogenesis of the disease: which seems to he related to a pituitary stalk lesion.     

Thin section CT of normal pituitary glands

In order to better understand the CT appearance of the normal pituitary gland, we scrutinized the pituitary glands of 55 patients who had no clinical indication of pituitary abnormality. The superior surface of the pituitary gland was convex in 9 cases (16.4%), flat in 16 (29.1%), and concave in 30 (54.5%). All but one of the glands with upward convexity belonged to patients less than 40 years old. The height of the pituitary glands was from 2 mm to 7 mm in 48 (87.3%) and 7 mm to 9.1 mm in 7 (12.7%); all but one case was less than 40 years old. Although earlier reports have suggested the presence of a pituitary microadenoma when the gland has a convexity of its superior surface or is more than 7 mm in height, these findings can be seen in normal pituitary glands, particularly in younger individuals. Therefore, pituitary microadenoma should be diagnosed carefully in younger patients. The low density area frequently seen in the superior aspect of pituitary glands on axial scans was found to result from the concave superior surface of the gland. The pituitary stalk was off the midline in five patients (9%). Shifting of the pituitary stalk can be seen in the normal pituitary gland and is not always characteristic of microadenoma.     

Normal pituitary gland: coronal MR imaging of infundibular tilt

To determine the prevalence of pituitary infundibular deviation or tilt as a normal variant, coronal magnetic resonance (MR) images of 50 patients who had been examined for reasons other than pituitary disease were evaluated retrospectively. Forty-six percent of the patients had a more or less pronounced tilt of the pituitary stalk. This tilt was due to developmental lateral eccentricity of the pituitary gland in relationship to the midline of the brain in 34% and to ontogenic eccentric insertion of the pituitary infundibulum off the midline of the gland in the other 12%. This high frequency of stalk deviation in patients without pituitary disease suggests that such displacement by itself should not be used to support the presence of pituitary microadenoma on MR images or computed tomograms.     

MR of pituitary metastasis in a patient with diabetes insipidus.

We present a case of acute-onset diabetes insipidus in a 69-year-old man who had been treated for lung cancer. T1-weighted MR images showed a thickened pituitary stalk and absence of the normal high intensity of the posterior pituitary lobe. Dynamic imaging demonstrated poor enhancement in the posterior lobe, whereas the anterior lobe was strongly enhanced. Autopsy revealed that metastatic tumor from lung cancer had infiltrated the posterior lobe as well as the pituitary stalk.     

MR imaging of the posterior hypophysis in children

The posterior lobe of the pituitary gland was studied by MR imaging in 30 children without pituitary gland disease and compared with studies from a group of 13 children with central diabetes insipidus, including eight cases of primary diabetes insipidus and five cases of diabetes insipidus secondary to suprasellar tumors (four proved germinomas, one still unknown tumor). Two components in the sella turcica were identified in all 30 children without pituitary gland disease, and the posterior lobe was identified as a high-intensity structure on T1-weighted images. In all 13 patients with diabetes insipidus, the normal hyperintense signal of the posterior hypophysis was absent on T1-weighted images. Three patients with suprasellar tumors presented with a progressively enlarging pituitary stalk on follow-up. Our findings show that absence of the normal hyperintense signal of the posterior lobe is closely related to a loss of function of the neurohypophysis. Size or signal modification of the pituitary stalk should suggest the development of a suprasellar tumor.