(Radiographics. 1999;19:826-829.)
© RSNA, 1999
Neuroradiology Case of the Day1
Francis G. Greiner, MD and
Deepak Takhtani, MD
1 From the Department of Radiology, University of South Alabama Medical Center, 2451 Fillingim St, Mastin Bldg 301, Mobile, AL 36617. From the 1998 RSNA scientific assembly. Received November 17, 1998; revision requested December 10 and received January 12, 1999; accepted January 14. Address reprint requests to F.G.G.
Index Terms: Diabetes insipidus, 145.519 • Germ cell neoplasm, 145.369 • Pituitary, neoplasms, 145.369
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HISTORY
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A 12-year-old boy presented with an 18-month history of polyuria, nocturia (two to four times a night), and polydipsia. There was no significant medical history or medication history. The patient was on a normal growth curve and reported that his urine had always been clear. Puberty had started 1 year earlier. A test for diabetes mellitus was reportedly negative.
A review of systems was negative for vision changes, sleep disorders, and headache. There was no evidence of heat or cold intolerance. Results of physical examination were normal. Magnetic resonance (MR) imaging was performed.
Six months later, the patient presented with a 9-day history of nausea, vomiting, and occipital headache of variable intensity. He was somnolent but oriented. At physical examination, the patient was afebrile and lacked meningeal signs. His vision was reported as blurred and was not readily correctable with lenses at ophthalmologic examination. There was no evidence of fundal abnormality or papilledema; visual fields were normal when tested by means of confrontation. Computed tomography (CT) and repeat MR imaging were performed.
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FINDINGS
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The initial MR images showed loss of the area of high signal intensity normally seen in the posterior lobe of the pituitary gland (Fig 1). This finding is often seen in diabetes insipidus, which was consistent with the results of water deprivation tests. Contrast material–enhanced MR images showed thickening of the infundibulum (Fig 2). Normally, it is less than 4 mm in diameter with a mean diameter of slightly more than 2 mm. The pineal gland had an appearance suggestive of a mass and demonstrated an unusual enhancement pattern.
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Figure 1. Figures 1, 2. (1) Sagittal T1-weighted MR image (repetition time msec/echo time msec = 600/20) shows loss of high signal intensity in the posterior pituitary gland (arrow). The gland is of normal size. The infundibulum is enlarged, and the pineal region is prominent and suggestive of a mass. (2) Contrast-enhanced coronal T1-weighted MR image (600/20) shows a normal pituitary gland but a thickened infundibulum (arrow).
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Figure 2. Figures 1, 2. (1) Sagittal T1-weighted MR image (repetition time msec/echo time msec = 600/20) shows loss of high signal intensity in the posterior pituitary gland (arrow). The gland is of normal size. The infundibulum is enlarged, and the pineal region is prominent and suggestive of a mass. (2) Contrast-enhanced coronal T1-weighted MR image (600/20) shows a normal pituitary gland but a thickened infundibulum (arrow).
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Six months later, CT revealed an isoattenuating suprasellar mass 2.5 cm in diameter with two distinct foci of increased attenuation (Fig 3). The mass enhanced in a nearly homogeneous fashion with several cystic-appearing areas that did not enhance (Fig 4). Repeat MR imaging showed that the mass was slightly hypointense relative to the pons and cortical gray matter (Fig 5). The mass had increased signal intensity on intermediate and T2-weighted images with areas of high signal intensity, which may have been cysts or fluid (Fig 6). There were two punctate areas of very low signal intensity, which possibly represented calcium. The mass was above the sella and chiasm and enhanced almost homogeneously with multiple small areas of poor enhancement (Fig 7). The pineal gland was unchanged from the initial MR imaging study (Figs 1, 5, 7), but its appearance was suggestive of an additional mass and it demonstrated enhancement. These findings were not investigated at surgery.
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Figure 3. Figures 3–6. (3) CT scan shows a large, isoattenuating suprasellar mass with areas of higher attenuation that are likely calcifications (arrows). (4) Contrast-enhanced CT scan shows that the mass has a somewhat granular appearance. Within it are several areas of intense enhancement (arrowhead) and poor enhancement (arrow). (5) Sagittal T1-weighted MR image (600/12) shows a suprasellar mass of low signal intensity (small arrows) that contains cystlike areas (large arrow). (6) Coronal T2-weighted MR image (2,500/102 [effective]) shows that the mass has increased signal intensity. There are several areas of high signal intensity, which are consistent with cysts or necrosis.
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Figure 4. Figures 3–6. (3) CT scan shows a large, isoattenuating suprasellar mass with areas of higher attenuation that are likely calcifications (arrows). (4) Contrast-enhanced CT scan shows that the mass has a somewhat granular appearance. Within it are several areas of intense enhancement (arrowhead) and poor enhancement (arrow). (5) Sagittal T1-weighted MR image (600/12) shows a suprasellar mass of low signal intensity (small arrows) that contains cystlike areas (large arrow). (6) Coronal T2-weighted MR image (2,500/102 [effective]) shows that the mass has increased signal intensity. There are several areas of high signal intensity, which are consistent with cysts or necrosis.
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Figure 5. Figures 3–6. (3) CT scan shows a large, isoattenuating suprasellar mass with areas of higher attenuation that are likely calcifications (arrows). (4) Contrast-enhanced CT scan shows that the mass has a somewhat granular appearance. Within it are several areas of intense enhancement (arrowhead) and poor enhancement (arrow). (5) Sagittal T1-weighted MR image (600/12) shows a suprasellar mass of low signal intensity (small arrows) that contains cystlike areas (large arrow). (6) Coronal T2-weighted MR image (2,500/102 [effective]) shows that the mass has increased signal intensity. There are several areas of high signal intensity, which are consistent with cysts or necrosis.
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Figure 6. Figures 3–6. (3) CT scan shows a large, isoattenuating suprasellar mass with areas of higher attenuation that are likely calcifications (arrows). (4) Contrast-enhanced CT scan shows that the mass has a somewhat granular appearance. Within it are several areas of intense enhancement (arrowhead) and poor enhancement (arrow). (5) Sagittal T1-weighted MR image (600/12) shows a suprasellar mass of low signal intensity (small arrows) that contains cystlike areas (large arrow). (6) Coronal T2-weighted MR image (2,500/102 [effective]) shows that the mass has increased signal intensity. There are several areas of high signal intensity, which are consistent with cysts or necrosis.
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Figure 7. Contrast-enhanced sagittal T1-weighted MR image (600/12) shows intense, near-homogeneous enhancement of the mass. There are areas that do not enhance (arrows); these do not correspond to the larger cystic areas seen on the nonenhanced MR images. The pineal gland demonstrates irregular enhancement but is unchanged in size or appearance from the initial study.
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DIAGNOSIS: Malignant mixed germ cell tumor with yolk sac and teratomatous components.
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DISCUSSION
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Loss of high signal intensity in the posterior pituitary gland on MR images without an obvious mass in the gland is consistent with diabetes insipidus (1,2). Diabetes insipidus is often idiopathic. Inflammation and infection, particularly from granulomatous disease, are other common causes. Specific causes include syphilis, sarcoidosis, tuberculosis, and meningitis. In this case, there was no history of trauma, another common cause of diabetes insipidus (3,4).
In addition, prominence of the infundibulum suggests the possibility of cell infiltration as the cause of diabetes insipidus and infundibular enlargement. Histiocytosis X (Langerhans cell histiocytosis), leukemic infiltration, hamartoma, and metastatic disease have all been reported to cause infundibular thickening associated with diabetes insipidus (2). In this case, no evidence of tumor or leukemia was found at the initial hematologic evaluation.
Tumor cell infiltration can cause infundibular enlargement. A pituitary adenoma of the sella turcica may extend along the infundibulum, but such extension is quite uncommon, especially in children. The differential diagnosis for a mass in this area includes craniopharyngioma, hamartoma, glioma, and germ cell tumor, all of which are associated with diabetes insipidus.
Craniopharyngioma is the most common of these lesions. However, craniopharyngiomas are usually slow growing, demonstrate dense calcification in most cases (70%–80%), and have an enhancement pattern inconsistent with the one in this case. Hamartoma also has a very slow growth rate but may demonstrate high signal intensity on T2-weighted MR images, as occurred in this case (Fig 6). Hamartomas do not enhance prominently (5). The rapid growth of the lesion in this case, the absence of visual field deficits or visual field cuts, and the nearly homogeneous enhancement pattern suggest a germ cell tumor. The appearance of the pineal gland suggests a multifocal origin. The CT finding of faint calcification and the small cystic areas on T2-weighted MR images are most consistent with this diagnosis (6,7).
Germ cell tumors of the central nervous system are rare. At histopathologic analysis, pure germ cell tumors are identical to testicular seminomas and are thought to develop from rests of primitive embryonic germ cells. Mixed germ cell tumors are composed of germinomatous, embryonal, choriocarcinomatous, and yolk sac (endodermal sinus) components (8). Suprasellar germ cell tumors are identical histologically to pineal germ cell tumors and testicular seminomas. These can occur concurrently. A review of the Mayo Clinic's neuropathology specimens found 64 germ cell tumors in over 20,000 cases for a frequency of 0.3% (9). Another large study of pediatric tumors demonstrated a slightly higher frequency of 2% (10). In the past, the high morbidity of neurosurgical biopsy may have led to a low estimate of the frequency of germ cell tumors. The pineal gland is the most common location for germinomas with a male predominance of nearly 2:1. The pituitary-infundibular-hypothalamic axis is the second most common site, and tumors in this region demonstrate a slight female predominance (10).
Cerebrospinal fluid metastases are frequent with suprasellar germ cell tumors. The work-up of this case included MR imaging of the spine, the results of which were normal. Levels of human chorionic gonadotropin and 
-fetoprotein were elevated in both cerebrospinal fluid and serum, but the cerebrospinal fluid was otherwise normal. Laboratory values included normal levels of thyroxine, thyroid-stimulating hormone, cortisol, and prolactin at both admissions. The testosterone level was massively elevated at the second admission with suppression of luteinizing hormone and follicle-stimulating hormone levels. The patient underwent surgical resection to debulk the tumor and for a tissue diagnosis. Treatment also involved chemotherapy with cisplatin, vincristine sulfate, methotrexate, and bleomycin sulfate followed by actinomycin D, cyclophosphamide, and etoposide.
Several studies have shown a link between idiopathic diabetes insipidus and infundibular thickening (11–13). Retrospective analysis of cases of germinoma has shown that diabetes insipidus with infundibular thickening is a frequent combination at presentation. In one study, six of nine patients with this combination developed an intracranial germinoma (11). These six cases represented nearly one-third of the total germ cell tumors in the study. The high frequency of progression to germinoma of a thickened infundibulum associated with diabetes insipidus may merit evaluation of cerebrospinal fluid for germ cell tumor and, if the results of this evaluation are negative, frequent MR imaging follow-up.
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References
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Mootha SL, Barkovitch AJ, Grumbach MM, et al. Idiopathic hypothalamic diabetes insipidus, pituitary stalk thickening, and occult intracranial germinoma in children and adolescents. J Clin Endocrinol Metab 1997; 82:1362-1367.[Abstract/Free Full Text]
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Wang LC, Cohen ME, Duffner PK. Etiologies of central diabetes insipidus in children. Pediatr Neurol 1994; 11:273-277.[Medline]
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HISTORY
FINDINGS
