MR of the Diaphragma Sellae

Transcription

1 765 MR of the Diaphragma Sellae David L. Daniels 1 Kathleen W. Pojunas 1 David P. Kilgore 1 Peter Peh 2 Glenn. Meyer lan L. Williams 1 Vitor M. Haughton 1 The appearane of the diaphragma sellae is desribed in ryomirotomi setions and on MR in patients with and without intra- and suprasellar masses. On MR, it appears as a thin band of negligible signal that is best shown when adjaent CSF or a mass has greater signal intensity. Its position or absene an be used to differentiate intrasellar masses with suprasellar omponents from suprasellar masses. Differentiating intrasellar masses with suprasellar omponents from suprasellar masses may be diffiult with CT beause the pituitary gland, diaphragma sellae, and suprasellar masses may enhane equally after intravenous ontrast administration. Theoretially, MR should be able to show the diaphragma sellae beause other dural refletions, suh as the falx erebri and walls of the avernous sinuses, an be differentiated from the adjaent CSF when it has greater signal intensity [1 ]. Materials and Methods Reeived November 8, 1985; aepted February 19, Department of Radiology, Medial College of Wisonsin, Froedtert Memorial Lutheran Hospital, 9200 West Wisonsin ve., Milwaukee, WI ddress reprint requests to D. L. Daniels. 2 Department of Radiology, University Hospital, Uppsala, Sweden. 3 Department of Neurosurgery, Medial College of Wisonsin, Milwaukee, WI JNR 7: , September/Otober /86/ merian Soiety of Neuroradiology Sagittal or oronal anatomi images of the sella were obtained by setioning four fresh frozen adaver heads with a horizontally utting heavy-duty sledge ryomirotome (LK 2250) and then serially photographing the surfaes of the speimens [2]. In the anatomi images, the diaphragma sellae and assoiated blood vessels, the pituitary gland, and the infundibulum were identified using anatomi literature [3-5]. Ten normal volunteers and 22 patients were studied with MR. The patients inluded 12 with pituitary miroadenomas that were verified by surgial findings (four ases) and by CT, linial, and hemial findings [6]; seven with pituitary maroadenomas and two with tuberulum sellae meningiomas that were verified by CT and surgery; and one with a large suprasellar aneurysm that was verified by CT and angiography. The patients and volunteers were studied with T researh MR sanners or with a 1.5-T ommerial MR sanner (General Eletri Signa). The MR tehnique inluded a sagittal loalizer san, sagittal and/or oronal sans, 3- or 5-mm thik slies, 128 x 256 or 256 x 256 matrix, one or two signal aquisitions, a short repetition time (TR) of mse with a mse eho delay (TE), a long TR (2000 or 2500 mse) with 25, 50, 75, and 100 mse TE, and single or multislie data aquisition. The anatomi and MR images were orrelated to identify dural refletions and intra- and suprasellar strutures. Results and Disussion The diaphragma sellae, a dural membrane that forms the upper margin of the pituitary fossa, extends from the dorsum sellae to the tuberulum sellae and between the medial dural walls of the avernous sinuses. The diaphragma has a entral opening of variable size through whih the infundibulum extends from the hypothalamus to the posterior lobe of the pituitary gland. Vasular supply to the diaphragma onsists of interavernous venous onnetions and branhes of the

2 766 DNIELS ET L. JNR :7, September/Otober 1986 Fig. 1.- and, Coronal ryomirotomi setions through sella. In the more anterior setion (), diaphragma sellae (arrows) is straight and intat and has small blood vessels (arrowheads) at its undersurfae. In, diaphragma sellae (straight arrows) is mildly onvex lateral to infundibulum (I), whih extends 8 through the diaphragma's entral opening. Diaphragma is ontiguous with dura (urved arrows) overing pituitary gland and avernous sinuses. ( = internal arotid artery, P = pituitary gland, OC = opti hiasm.) Fig. 2.-Coronal MR images through pituitary gland (P) and a parasellar meningioma (wide solid arrows). In a long TR, short TE image (), note diaphragma sellae appearing as a band of negligible signal (thin arrows) above pituitary gland. In a long TR and TE image (), band is not shown and CSF has high intensity signal. (Open arrow = wall of avernous sinus, = internal arotid artery.) 8 8 Fig. 3.-Variations of normal appearane of diaphragma sellae may our. In, a oronal short TR and TE image, the infundibulum extends to pituitary gland (P). ( = internal arotid artery, OC = opti hiasm.) In, a long TR, short TE image at same loation as, prominent urvilinear strutures (arrows) with negligible signal probably represent a ombination of diaphragma sellae and prominent blood vessels.

3 JNR :7, September/Otober 1985 MR OF DIPHRGM SELLE 767 Fig. 4.-Diaphragma sellae (arrows) appears intat below a tuberulum se llae meningioma in sagittal long TR and TE () and oronal short TR () images. Diaphragma sellae, pituitary gland, avernous sinus, and tumor en- hane equally in an intravenously enhaned oronal CT san (C). t surgery, diaphragma sellae was normal. ( = internal arotid artery.) Fig. 5.-Diaphragma sellae (open urved arrow) is not displaed by suprasellar aneurysm in short TR () and long TR-short TE () oronal images. neurysm has mixed signal intensity, representing small lumen (arrow) and thrombus. Medial temporal lobe enephalomalaia (asterisk) represents infartion. Fig. 5.-Pituitary miroadenoma (M) showing less and the same signal intensity as that of pituitary gland in omparing short TR () and long TR-short TE () oronal images. Diaphragma sellae (arrows) is displaed upward by miroadenoma in.

4 768 DNIELS ET L. JNR:7, September/Otober 1986 Fig. 7.-, Surgially verified tuberulum sellae meningioma (white arrows) extends into left side of pituitary fossa and has a less intense signal than that of pituitary gland (P) in a short TR oronal image., Diaphragma sellae (blak arrows) is displaed downward in sagittal long TR and TE image through left side of tumor but not in sagittal image through right side (C). Fig. 8.-Pituitary adenoma with large suprasellar omponent (white arrows). Edges of diaphragma sellae (blak arrows) are identified in oronal () and parasagittal () long TR images and in midline short TR image (C). inferior hypophyseal and intraavernous internal arotid arteries [3-5]. In sagittal and oronal ryomirotomi setions, the diaphragma sellae appears as a thin transverse dural membrane assoiated with small blood vessels at its inferolateral surfae. In a oronal setion through the posterior part of the pituitary gland, the diaphragma appears slightly onvex lateral to the infundibulum. In a more anterior oronal setion, the diaphragma appears straight (Fig. 1). In most sagittal and oronal MR images of normal volunteers and patients without a sellar mass, a thin band of negligible signal is identified above the sella turia that has the onfiguration of the diaphragma sellae (Fig. 2). Just as other dural refletions produe negligible signals, this band likely represents the diaphragma sellae and adjaent blood vessels. The entral hiatus in the band is best shown in a oronal setion in whih the infundibulum attahes to the pituitary gland. In most ases, the band is better seen in long TR and short TE images than in short TR images or in long TR and TE images, probably beause of partial volume averaging of high-intensity CSF in the latter images. Unommonly, the band appears thikened, probably from prominent blood vessels (Fig. 3). In MR images of patients with intra- or suprasellar masses, the band an be identified (Figs. 4-8). The band is displaed upward in pituitary miroadenomas in 25% of our ases and downward in one of our two ases of tuberulum sellae meningioma. It is not identified entrally in any ase of pituitary maroadenoma. Identifiation of the diaphragma sellae with MR an be used to help define the upper limit of intrasellar pathology, the lower limit of suprasellar pathology, and to help differentiate tuber-

5 JNR:7. September/Otober 1986 MR OF DIPHRGM SELLE 769 ulum sellae meningioma from pituitary maroadenoma when meningiomatous hyperostosis or alifiation may not be as obvious as with CT. REFERENCES 1. Daniels DL. Peh P, Mark L, Pojunas K, Williams L, Haughton VM. Magneti resonane imaging of the avernous sinus. JNR 1985;6: Raushning W, erstrom K, Peh P. Correlative raniospinal anatomy studies by omputed tomography and ryomirotomy. J Comput ssist Tomogr 1983;7: onneville JF, Dietemann JL. Radiology of the sella turia. erlin: Springer-Verlag, 1981 : ergland RM, Ray S, Turak RM. natomial variations in the pituitary gland and adjaent strutures in 225 human embryo ases. J Neurosurg 1968;28 : Renn WH, Rhoton L. Mirosurgial anatomy of the sellar region. J Neurosurg 1975;43: Pojunas KW, Daniels DL, Williams L, Haughton VM. MR imaging of prolatin-sereting miroadenomas. JNR 1986;7: