RADIOANATOMY OF SELLA TURCICA

Transcription

1 RADIOANATOMY OF SELLA TURCICA O.BAKKACHA, H.MALAJATI, M.RHISSASSI, H. BENCHAABOUNE, N.CHAKIR, My R. EL HASSANI,M.JIDDANE Department of Neuroradiology specialties Hospital. Rabat

2 Objective: New imaging modalities permits detailed knowledge of the radioanatomy of Sella turcica. For Adenoma (90 % of the pituitary tumours). Magnetic resonance imaging (MRI) not only contributes to diagnosis but is particularly important to assess extension, detect possible complications and follow-up after treatment. Normal anatomical variants must also be considered: location, volume and signal of posterior pituitary, morphology of the superior margin of the pituitary tissue, shape of the bony sella, number and position of parasellar veins...

3 Techniques MRI has been considered as the modality of choice for evaluation of the sellar and juxtasellar regions. The studies of the pituitary gland were performed with a 1.5-T imaging unit (slice: 1 to 2 mm) with sagittal and coronal views, using T1 and T2-weighted sequences before and after contrast injection, followed by coronal dynamic acquisition. MRA could be used to recognize the anatomical variations of the vessels.

4 Embryology The anterior adenohypophysis develops from the upward migration of the Rathke pouch, an ectodermal-lined diverticulum from the embryonic mouth.

5 The neurohypophysis, infundibulum, and supraoptic and paraventricular nuclei of the hypothalamus derive from the downgrowth of neuroectoderm of the diencephalon.

6 physiology 1) adenohypophysis The adenohypophysis is responsible for the synthesis of growth hormone, adrenocorticotrophic hormone(acth), and prolactin. Release of these hormones is mediated by the hypothalamus. The adenohypophysis is isointense relative to gray matter on Ti-weighted images.

7 physiology 2) neurohypophysis Antidiuretic hormone and oxytocin are synthesized in the hypothalamus and stored in the neurohypophysis until their release is dictated by the hypothalamus. It is probably the neurosecretory material that produces the high signal intensity evident on most T1-weighted images with normal findings. Absence of this high signal is often, but not always, associated with compression lesions of the pituitary gland

8 Physiology MRI sagittal: T1 weighted images without contrast normal radiology aspect of the sella turcica Normal anatomy of the sella turcica and in the sagittal plane.

9 Blood supply The neurohypophysis and adenohypophysis receive blood from the inferior and superior hypophyseal arteries respectively; The capillary plexus of the inferior hypophyseal artery drains into the dural sinus although some of these capillaries in the neural stalk form short' portal veins that drain into the anterior pituitary gland; MRA could be used to recognize the anatomical variations of the vessels.

10 Imaging Results MRI has enabled the anatomical study of sella turcica especially of the pituitary gland and its pathology: 1. in Sagittal plane. 2. in Coronal plane.

11 In sagittal plane Sella turcica is a midline, shallow depression in the posterior sphenoid bone that contains the pituitary gland. The floor of the sella turcica is variable in appearance, depending largely on the degree of aeration of the underlying sphenoid sinus.

12 In sagittal plane The cortical bone and air-filled sinus may merge imperceptibly on MRI images. The dorsal most aspect of the sphenoid bone descends to form the clivus. The roof of the sella turcica is formed by a dural reflection, the diaphragma sellae. This thin membrane is inconsistently visualized on MRI images but is best seen on long TR/short TE images. sagittal T2 weighted MR image shows the normal anatomic structures:pituitary salk (arrow)

13 a) b) D L A C B (a) Drawing illustrates normal anatomy of the sella turcica and juxtasellar region in the parasagittal plane. A = adenohypophysis, B = neurohypophysis, C=pituitary salk, D = optic chiasm, E = tuber cinereum, F = anterior third ventricle, G = mamillary bodies, H = interpeduncular cistern, I = prepontine cistern,j = clivus, K = sphenoid sinus L=infundibulum(1) (b)sagittal Ti-weighted MR image shows the normal anatomic structures: A=adenohypophysis,B=neurohypophysis,C=pituitary salk and C D=optic chiasm, L=infundibulum.

14 In coronal plane Supra sellar cistern include the infundibulum, which extends from the cephalic surface of the pituitary gland to the tuber cinereum-its junction with the hypothalamus. The optic chiasm lies anterior to the infundibulum. The mamillary bodies are located posterior to the tuber cinereum, and the midline third ventricle is cephalad to both. The contents and borders of the suprasellar cistern are well depicted in the coronal plane. Non depiction of the medial dural wall may suspect cavernous sinus invasion by pituitary adenoma.

15 a) b) F E D B C I (a)drawing illustrates normal anatomy of the sella turcica in the coronal plane through the middle of the sella turcica and juxtasellar region. A = adenohypophysis, B = neurohypophysis, C=pituitary salk, D = optic chiasm, E = third ventricle, F =internal carotid artery, G = occulomotor nerve, H = trochlear nerve, I =cavernous carotid artery,j = abducens nerve, K = ophtalmic nerve L=maxillary nerve,m=temoral lobe,n=cavernous sinus,o=sphenoid sinus (b)coronal uncontrast Ti-weighted MR image shows the normal anatomic structures:

16 a) B b) M G a)drawing illustrates normal anatomy of the sella turcica in the coronal plane through the middle of the sella turcica and juxtasellar region. A = adenohypophysis, B = neurohypophysis, C=pituitary salk, D = optic chiasm, E = third ventricle, F =internal carotid artery, G = occulomotor nerve, H = trochlear nerve, I =cavernous carotid artery,j = abducens nerve, K = ophtalmic nerve L=maxillary nerve,m=temoral lobe,n=cavernous sinus,o=sphenoid sinus (b)coronal Ti-weighted MR image after contrast injection shows the normal anatomic structures:

17 In coronal plane Sella turcica is bordered laterally by thin dural reflection of the cavernous sinus. Cavernous sinus content : Third cranial nerve. Ophtalmic, maxillary divisions of the fifth nerve and sixth cranial nerves: are identified as hypointense structures within the lateral wall, from superior to inferior, respectively. Intra-cavernous Carotid Artery. The best imaging finding for definitive diagnosis of invasion remains complete encasement of the cavernous carotid artery by the tumor.

18 B G A H C Drawing illustrates normal anatomy in the coronal plane through the anterior portion of the sella turcica and juxtasellar region. A adenohypophysis, B = optic chiasm, C = supraclinoid internal carotid artery, D = oculomotor nerve, E = cavernous internal carotid artery, F = fifth nerve, G = cavernous sinus, H = sphenoid sinus. Coronal T1 without contrast: A adenohypophysis, B = optic chiasm, C = supraclinoid internal carotid, G = cavernous sinus,

19 In coronal plane In T1 and T2 Weighted Images: - The infundibulum, tuber cinereum, and mamillary bodies are isointense relative to gray matter on T1- weighted images. - Hypersignals in T2 weighted images of the lateral pituitary veins should not be confused with microprolactinomas. In Dynamic Imaging: - it can be used routinely for the diagnosis of ACTH secreting microadenomas. In this case, dynamic imaging can demonstrate absence or a delay in the enhancement in the pituitary adenoma as compared to the normal pituitary gland.

20 In coronal plane After contrast injections: The hypophysis and infundibulum enhance homogenously. The cavernous sinus enhances to the same degree as the pituitary gland, rendering the transmitted cranial nerves and cavernous carotid artery more conspicuous than on the unenhanced images; Demarcation between the pituitary gland and the cavernous sinus is more apparent on the unenhanced images.

21 A H B D E F Drawing illustrates normal anatomy in the coronal plane through the anterior portion of the sella turcica and juxtasellar region. A adenohypophysis, B = optic chiasm, C = supraclinoid internal carotid artery, D = oculomotor nerve, E = cavernous internal carotid artery, F = ophthalmic nerve, G = cavernous sinus, H = sphenoid sinus. Coronal T1 after contrast injection: -hypophysis and pituitary salk (red arrow) enhance homogenously. -cavernous sinus enhances to the same degree as the pituitary gland

22 In coronal plane Anatomic variant: A convex aspect of the upper margins of the pituitary gland is an anatomic variant. In this case the pituitary gland may get into contact with the optic chiasm. This is due to either: 1. an inadaptation of the container-content. 2. secretion hyperactivity during pregnancy or adolescence.

23 CONCLUSION Recognition of the anatomy of sella turcica helps to understand the pathological lesions wich may affect the pituitary gland. MRI imaging of the sella turcica is very effective for diagnosis of pituitary adenoma and follow-up after treatment. MRI Is the modality of choice for exploration of sella turcica.

24 REFERENCES 1) DavidE.Jobnsen, MD. William W. Woodruff MD Ira S. Allen, MD PeterJ MR Imaging of the Sellar and Juxtasellar regions. RadloGraphics ) Cully CM, Rosenfield.. Pituitary development: regulatory codes in mammalian organogenesis. Science ) F. Bonneville, F.Cattin, Kathlyn Marsot-Dupuch, D. Dormont, JF.Bonneville, J.Chiras T1 Signal Hyperintensity in the Sellar Region: Spectrum of Findings RadioGraphics ) J.-F. Bonneville, F. Bonneville and F. Cattin.MRI of the pituitary gland: indications and results in gynaecology and in obstetrics. Gynecol Obstet Fertil ) Cattin F,Bonneville JF. MRI study of the hypophysis. J Neuroradiol ) F. Cattin, J.-F. Bonneville, F. Bonneville. About enhancement of the presellar dura. J Neuroradiol. 2003