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Show Journal of Neuro- Ophthalmology 16( 3): 199- 203, 1996. © 1996 Lippincott- Ravcn Publishers, Philadelphia Intrasellar Vascular Malformation Mimicking a Pituitary Macroadenoma Todd J. Gould, M. D., Lenworth N. Johnson, M. D., Edward V. Colapinto, M. D., Linda E. Spollen, M. D., and Fabio J. Rodriguez, M. D. We report the case of a 61- year- old man with an unusual intrasellar vascular malformation, who presented with symptoms of hypopituitarism and whose neuroradio-logic evaluation mimicked a pituitary macroadenoma. The histopathologic and radiologic findings are discussed. This rare lesion should be considered in the diagnosis of a sellar mass lesion. Key Words: Arteriovenous malformation- pituitary adenoma- magnetic resonance imaging. Vascular malformations intrinsic to the optic chiasm or optic nerve are rare, with only 29 cases described in the literature ( 1,2). These lesions often present with " chiasmal apoplexy" with the triad of abrupt headache, change of visual acuity, and visual field loss. Even less common are vascular malformations involving the sellar region, of which four cases of cavernous hemangiomas have been described ( 3). We report the case of a patient with an intrasellar vascular malformation that consisted of capillaries, veins, and rare arteries, and had angiographic features suggestive of an arteriovenous malformation. The patient presented with pituitary dysfunction and neuroradiologic evaluation mimicking a pituitary macroadenoma. Manuscript received March 30, 1995; accepted October 20, 1995. From the Neuro- Ophthalmology Unit, Mason Institute of Ophthalmology ( T. J. G., L. N. J.), the Division of Neurosurgery ( E. V. C.), the Department of Pathology ( L. E. S.), and the Department of Radiology ( F. J. R.), University of Missouri- Columbia, Columbia, Missouri, U. S. A. Address correspondence and reprint requests to Dr. Lenworth N. Johnson, M. D., Neuro- Ophthalmology Unit, Mason Institute of Ophthalmology, University of Missouri- Columbia, Columbia, MO 65212, U. S. A. CASE REPORT A 61- year- old man presented with a 12- year history of impotence that had worsened over the past 2 years. He had cold intolerance, but denied galactorrhea or change in body habitus. There was no headache or other neurologic or ophthalmologic symptoms. He was otherwise in excellent health. The general physical, neurologic, and neuro-ophthalmologic examinations were normal. Specifically, his visual acuity was 20/ 20 for each eye and there was no visual field defect on full threshold automated static perimetry. Color vision was normal. Laboratory studies revealed a markedly depressed testosterone level of < 11 ng/ dl ( normal 200- 900 ng/ dl); a low luteinizing hormone level of 0.5 uTU/ ml ( normal 2.4- 5.9 uTU/ ml); and low thyroxine ( T4) of 4.5 p- g/ dl ( normal 5.0- 11.5 p- g/ dl). The ultrasensitive thyroid stimulating hormone level of 2.88 uIU/ ml and prolactin level of 19.2 ng/ ml were both normal. A pituitary lesion was sus- 199 200 T. /. GOULD ET AL. pected. A computed tomography ( CT) scan revealed a 2- cm sellar mass associated with erosion and thinning of the sellar floor. Magnetic resonance imaging ( MRI) showed the lesion to be isointense on Tl- weighted images and hyperin-tense on T2- weighted images ( Fig. 1). There was homogeneous, intense enhancement of the mass after gadolinium administration. The mass extended into the suprasellar cistern with upward displacement (" bowing") and compression of the anterior and middle regions of the optic chiasm. There was no evidence of extension into the cavernous sinuses. CT and MRI scans were suggestive of a pituitary macroadenoma. In retrospect, however, several focal low- signal areas compatible with flow voids were present within the lesion ( Fig. 1). Transsphenoidal resection of a suspected pituitary macroadenoma was undertaken 2 months after initiation of appropriate hormonal replacement therapy for hypopituitarism. The procedure was aborted, however, when it became clear, intraop-eratively, that the mass was very firm, fibrous, and prone to hemorrhaging, thus preventing safe removal via the transsphenoidal approach. Transsphenoidal biopsy specimens were small and failed to reveal a diagnosis. At 1.5 months after the initial transsphenoidal procedure, the patient underwent a right frontal craniotomy, and a round, reddish mass with blood vessels on its surface was seen between the optic nerves. The suprasellar portion of the mass was resected and sent for histopathologic examination. The sellar portion could not be excised safely due to the limited exposure, excessive hemorrhaging, and adherence of the fibrous, vascular mass to the FIG. 1. A: Coronal T1- weighted MRI demonstrating a 2- cm sellar mass ( arrow) that is isointense to brain. There is suprasellar extension and upward displacement of the chiasm. Several small foci of hypointensity, representing flow voids, are present. B: Axial T2- weighted MRI revealing hyperintensity of the sellar mass ( arrow). C: Coronal T1- weighted MRI after gadolinium administration demonstrating homogeneous intense enhancement of the mass and upward displacement of the optic chiasm ( arrow). ; Neuw- Ophthalmol, Vol. 26, No. 3, 2996 INTRASELLAR VASCULAR MALFORMATION 201 sellar walls. Postoperatively, visual acuity and color vision remained normal and unchanged. A bitemporal hemianopsia and a mild right afferent pupillary defect developed. The tissue obtained from the craniotomy procedure was compatible with a vascular malformation. In preparation for radiosurgery, cerebral angiography was performed and revealed a large, homogeneous vascular mass that occupied the sella turcica. The mass was supplied primarily by the meningohypophyseal branches of both cavernous internal carotid arteries, and showed early intense filling of the pterygoid venous plexus in the arterial phase ( Fig. 2). DESCRIPTION OF PATHOLOGY The tiny, mostly crushed tissue fragments obtained from the initial transsphenoidal procedure were nondiagnostic. Multiple small fragments from the frontal craniotomy biopsy were prepared for frozen and permanent sections. Material for light microscopy was fixed in 10% zinc- buffered formalin ( Anatech Corporation, Battle Creek, MI, U. S. A.) and prepared for paraffin embedding. Sections were cut at 2- 3 | xm. Routine staining with hematoxylin and eosin, Liebs and Congo red ( for amyloid), and elastic- trichrome was performed. Immunohistochemical staining for Factor VIII ( Dako Corp., Carpinteria, CA, U. S. A.) 1: 4000; growth hormone ( Dako), prediluted and further diluted 1: 10; and prolactin ( Dako), prediluted and further diluted 1: 10 was also performed. Microscopic examination of sections of the suprasellar tissue revealed a vascular lesion consisting of a mixture of small capillary- sized channels, numerous veins, and only occasional arteries separated by abundant fibrous tissue. Most vessels were surrounded by a thick coat of hyalinized collagen ( Fig. 3). While the lesion did not possess arterialized veins with walls replaced by collagen, it did exhibit venous adventitial " cuffing," in which collagen was deposited within the adventi-tia as well as externally. Further evidence for the vascular nature of this lesion was provided by a positive immunohistochemical stain for Factor VIII of cells lining the vascular spaces, confirming their endothelial nature. No pituitary tissue was seen in histologic sections; in particular, immunohistochemical staining for growth hormone and prolactin was negative. No cellular stroma suggestive of hemangiopericytoma was seen. Additionally, no meningothelial cells were noted in any of the tissue samples. DISCUSSION The differential diagnosis of an intrasellar mass with suprasellar extension includes craniopharyngioma, aneurysm, Rathke's cyst, chiasmal glioma, metastatic tumor, pituitary adenoma, and tubercu-lum sellae meningioma. A combination of features on gadolinium- enhanced MRI may be used to distinguish pituitary adenoma from these other lesions ( 4). However, our case illustrates that despite the resolution of MRI, an intrasellar vascular malformation can be difficult to distinguish from pituitary macroadenoma. High- resolution MRI revealed lucent areas or " flow voids" that corresponded to areas of rapid blood flow in the enlarged feeding arteries and engorged draining veins. Pituitary adenomas, meningiomas, cavernous hemangiomas, and the normal pituitary vasculature do not normally demonstrate flow voids. However, lucent areas on Tl- weighted images representing necrosis or fluid- containing cavities are found within 10- 30% of macroadenomas ( 5). Although these hypointense areas could mimic small flow voids, they will usually have increased signal intensity on T2- weighted images in contrast to flow voids, which remain hypointense. Our patients' vascular lesion had several small hypointense areas that, in retrospect, were consistent with flow voids. Perhaps the compressed nature of this lesion within the sella turcica inhibited the formation of larger vascular channels, thus resulting in failure to demonstrate the large flow voids seen classically with intracranial arteriovenous malformations. Despite the presence of abundant fibrous tissue, the histopathologic features of the vascular lesion in our patient were most consistent with that of an arteriovenous malformation, being comprised of capillaries, collagenized veins, and, rarely, arteries. There was no histopathologic evidence of a vascular meningioma or hemangiopericytoma. The vascular malformation was confirmed by angiography, which demonstrated early venous filling of the cavernous sinus, pterygoid plexus, and venous channels in the deep spaces of the neck bilaterally during the arterial phase. The treatment of intracranial vascular malformations must be individualized. Therapeutic options, either alone or in combination, include microneu-rosurgical excision, endovascular embolization, and stereotactic radiosurgery. In view of the difficulty encountered at surgery, stereotactic radiosurgery was recommended for our patient. Stereotactic radiosurgery of arteriovenous malformations ranging from 10 to 35 mm in diameter has been / Nciiro- Oplithiilmol, Vol. 16, No. 3, 1996 202 T. ]. GOULD ET AL. FIG. 2. A: Cerebral angiography demonstrating a large, homogeneous, vascular sellar mass supplied primarily by the meningohypophyseal branches of both internal carotid arteries. Selective injection of the right internal carotid artery ( large arrow) shows contrast within the intracranial arteries ( arterial phase). The pterygoid plexus and a large venous channel in the deep spaces of the neck ( small arrows) show early filling compatible with an arteriovenous malformation B: The right internal carotid artery ( large arrow) and intracranial vessels are observed during the arterial phase of cerebral angiography. There is early filling of the ipsilateral pterygoid plexus and the deep venous channel ( small arrows), the inferior portion of the left cavernous sinus ( small curved arrow), and the contralateral pterygoid plexus and the venous channel within the deep space of the neck ( large curved arrows), compatible with an arteriovenous malformation. FIG. 3. Arteriovenous malformation with irregular vascular channels and vessels. Hematoxylin and eosin x10. / Natm- Ophlhtilmol, Vol. 16, No. ,3, 7996 INTRASELLAR VASCULAR MALFORMATION 203 associated with complete thrombosis rates of > 80% at years post treatment ( 6). It is difficult to explain why the pituitary gland, a highly vascular structure, has not been previously reported to harbor an arteriovenous malformation. Arteriovenous malformations can go undetected since they do not always give rise to symptoms. However, we believe that intrasellar arteriovenous malformations would come to clinical attention as they enlarge within and outside the confines of the sella turcica, causing hypopituitarism; visual loss; cranial nerve III, IV, or VI dysfunctions; or symptoms identical to those seen with pituitary apoplexy ( 7,8). We suspect that intrasellar arteriovenous malformations are not unrecognized, but, rather, are extremely rare. Acknowledgment: Aided in part by an unrestricted grant from Research to Prevent Blindness, Inc. ( New York). REFERENCES 1. Hwang JF, Yau CW, Huang JK, Tsai CY. Apoplectic opto-chiasmal syndrome due to intrinsic cavernous hemangioma. / Clin Neuro- Ophthalmol 1993; 13: 232- 6. 2. Sibony PA, Lessell S, Wray S. Chiasmal syndrome caused by arteriovenous malformations. Arch Ophthalmol 1982; 100: 438- 42. 3. Mitsuhashi T, Hashimoto R, Nagahama S, Nagata Y. Intrasellar cavernous angioma in neurofibromatosis. Human Pathol 1991; 22: 623^ t. 4. Taylor SL, Barakos JA, Griffith RH, Wilson CB. Magnetic resonance imaging of tuberculum sellae meningiomas: preventing preoperative misdiagnosis as pituitary macroade-noma. Neurosurgery 1992; 31: 621- 7. 5. Hirsch WL, Roppolo HMN, Hayman LA, Hinck VC. Sella and parasellar regions: pathology. In: Latchaw RE, ed. MR and CT imaging of the head, neck, and spine. 2nd ed. St. Louis: Mosby Year Book, 1991: 683- 747. 6. Friedman WA, Bova FJ. LINAC radiosurgery for arteriovenous malformations. / Neurosurg 1992; 77: 832^ 11. 7. Johnson LN, Pack WL. Transient oculomotor nerve misdirection in a case of pituitary tumor with hemorrhage. Arch Ophthalmol 1988; 106: 584- 5. 8. Maccagnan P, Macedo CL, Kayath MJ, Nogueira RG, Abucham J. Conservative management of pituitary apoplexy: a prospective study. / Clin Endocrinol Metab 1995; 80: 2190- 7. / Neuro- Ophthalmol, Vol. 16, No. 3, 1996 |
