Anatomy of sellar suprasellar region

Vomer, pterygoid process, medial and lateral pterygoid plates directed downwards from body

1. ANATOMY OF SELLAR AND SUPRASELLAR REGION

2. SELLAR REGION SPENOID BONE SPENOID SINUS DIAPHRAGM SELLAE PITITUARY GLAND CAVERNOUS SINUS

3. SPHENOID BONE Located - center of cranial base Resembles bat with wings outstretched Central portion-called body Lesser wing- spread from superolateral part of body has frontal lobe and olfactory tract 2 greater wings-spread upward from lower part of body Superior orbital fissure-between greater and lesser wings -passes-oculomotor, trochlear, abduscens, ophthalmic div of trigeminal

4. Sphenoid bone continue Body- contains sphenoid sinus-communicate to nasal cavity through sphenoid ostia Vomer, pterygoid process, medial and lateral pterygoid plates directed downwards from body Pitituary occupies central part of body Anteriorly tuberculum sellae, posterior-dorsum sellae.

5. The anterior clinoid processes are located at the medial end of the lesser wings the middle clinoid processes are lateral to the tuberculum sellae, posterior clinoid processes- situated at the superolateral margin of dorsum sellae. The dorsum sellae is continuous with the clivus. The upper part of the clivus is formed by the sphenoid bone and the lower part by the occipital bone. The carotid sulcus extends along the lateral surface of the body of the sphenoid.

6. pterion is located over the upper part of the greater wing “keyhole” - located behind the junction of the temporal line and the zygomatic process of the frontal bone anterior to the pterion. Significance- A burr hole placed over the pterion will be located at the lateral end of the sphenoid ridge. A burr hole placed at the keyhole will expose the orbit at its lower margin and dura over the frontal lobe at its upper margin.

7. Sphenoid sinus Present as minute cavities at birth,main development after puberty 3 types of sphenoid sinus in the adult: conchal, presellar, and sellar types, (depending on pneumatization extent) conchal- area below the sella is a solid block of bone without an air cavity. presellar - air cavity does not penetrate beyond a vertical plane parallel to the anterior sellar wall. sellar type - is the most common, and air cavity extends into the body of sphenoid below the sella and posteriorly as the clivus.

8. Sphenoid sinus The cavities within the sinus are subdivided by irregular minor septae. The septae are located off the midline as they cross the floor of the sella. CT or MRI of the sella provide the definition of the relationship of the septae to the floor of the sella needed for transsphenoidal surgery. Major septae may be found as far as 8 mm off the midline . The carotid artery produces prominence into the sinus wall below the floor and along the anterior margin of the sella

9. Diaphragma sellae Forms roof of sella turcica covers the pituitary gland, except in its center, which transmits the pituitary stalk thin, tenuous structure not an adequate barrier for protecting the suprasellar structures during transsphenoidal operation deficiency of the diaphragma sellae assumed to be a precondition to formation of empty sella. outpouching of the arachnoid protrudes through the central opening in the diaphragma into the sella turcica in about half of the patients. This outpouching represents a potential source of postoperative CSF leakage

10. PITUITARY GLAND 2 lobes- anterior and posterior anterior lobe wraps around the lower part of the pituitary stalk to form the pars tuberalis posterior lobe is more densely adherent to the sellar wall than the anterior lobe. anterior lobe is separated from the posterior lobe, there is a tendency for the pars tuberalis to be retained with the posterior lobe. Intermediate lobe cysts are frequently encountered during separation of the anterior and posterior lobes

11. The distance separating the medial margin of the carotid artery and the lateral surface of the pituitary gland varies from 1 to 3 mm Heavy arterial bleeding during transsphenoidal surgery has been reported to be caused by carotid artery injury.

12. Intrasellar tumors are subjected to the forces (like carotids passing closely ) These prevent them from being spherical, and the increased pressure within the tumor increases the degree to which the tumor insinuates into surrounding crevices and tissue planes. Separation of these extensions from the main mass of gland or tumor may explain cases in which the tumor persist or recur after adenoma removal

13. Intracavernous venous connection Venous sinuses may be found in the margins of the diaphragma and around the gland Intercavernous connections within the sella are named on the basis of their relationship to the pituitary gland the anterior intercavernous sinuses pass anterior to the hypophysis, posterior intercavernous sinuses pass behind the gland If anterior and post connections coexist- circular sinus Anterior sinus may extend downward in front of gland during transsphenoidal approach produces bleeding

14. Basilar sinus- posterior to dorsum sellae and upper clivus Connects posterior aspect of both cavernous sinuses Largest and most constant intercavernous connection across midline Superior and inferior petrosal sinus join basilar sinus Abduscens nerve enter posterior part of cavernous sinus by passing through basilar sinus.

15. Cavernous sinus Positioned either side of sella and sphenoid body Surrounds horizontal portion of carotid artery and part of abduscens Lateral wall of cavernous sinus extends from superior orbital fissure to apex of petrous part of temporal bone Occulomotor , trochlear and ophthalmic div of trigeminal nerve-in roof and lateral wall of cavernous sinus Branches of intracavernous portion of carotid artery- meningophyseal trunk, artery of inferior cavernous sinus and McConell’s artery

16. SUPRASELLAR AND THIRD VENTRICLE REGION This part deals with neural, arterial, and venous relationships in the suprasellar and third ventricular regions that are important in planning surgery for pituitary adenomas.

17. THIRD VENTRICLE Third ventricle located in center of head It is above sella, pituitary and midbrain Between- cerebral hemispheres, thalami and walls of hypothalamus Below the corpus callosum and body of lateral ventricle. Intimately related to circle of willis and deep venous system. Manipulation of walls of 3 rd ventricle may cause hypothalamic dysfunction.

18. ANATOMY OF THIRD VENTRICLE FLOOR- extends from optic chiasma (ant) to aqueduct of sylvius (post) Anterior half of floor formed by diencephalon and posterior half by mesencephalon

19. ANTERIOR WALL Extends from foramen of Monroe (above) to optic chiasma (below) Upper 1/3 hidden posterior to rostrum of corpus callosum Part of anterior wall visible on surface is formed by optic chiasma and lamina terminalis. From superior to inferior- column of fornix , foramen of monroe., ant commissure, lamina terminalis optic recess and optic chiasma

20. POSTERIOR WALL Extends from suprapineal recess above to aqueduct of sylvius below From above to below- Suprapineal recess Habenular commissure Pineal body Posterior commissure Aqueduct of sylvius

21. ROOF Extends from foramen of monro to suprapineal recess Tumors involving 3 rd ventricle (infrequently adenomas ) approached through roof of third ventricle 4 layers- neural layer (formed by fornix) - 2 thin membranous layer of tela choroidea (derived from pia mater) - layer of blood vessels between 2 layers of tela choridea

22. LATERAL WALL Not visible on external surface of brain. Formed by hypothalamus (inferiorly) and thalamus (superiorly) Thalamic and hypothalamic surfaces separated by hypothalamic sulcus

23. SUPRASELLAR CISTERNS Suprasellar region approached through cisterns surrounding anterior part of tentorial incisura. Incisura –triangular space between tentorium free edges Upper part of brainstem formed by midbrain sits in center of incisura.

24. Area between midbrain and free edges is divided into- Anterior incisural space –front of midbrain Paired middle incisural spaces-lateral to midbrain Posterior incisural space behind midbrain. Pituitary adenomas involve anterior incisural space Anterior incisural area roughly corresponds to suprasellar area.

25. CRANIAL NERVES Optic and oculomotor nerves and post part of olfactory tract pass through suprasellar region and anterior incisural space Optic nerve and chiasma cross anterior incisural space

26. OPTIC CHIASMA Normal chiasm overlies diaphragm sellae and pituitary (70%) Prefixed chiasm overlies tuberculum sellae.(30%)

27. Common sellar tumours The overwhelming majority of sellar region masses are pituitary adenomas (85%), craniopharyngiomas (3%), Rathke cleft cysts (2%), meningiomas (1%), and metastases (0.5%); all other lesions, such as hypophysitis, pituicytoma, spindle cell oncocytoma, and granular cell tumor of neurohypophysis, are rare lesions.

28. SURGICAL TECHNIQUES Transphenoidal hypophysectomy tumor removed through the nasal cavity. Advantages are - no other part of the brain is touched, the neurological complication rate is low, and there is no visible scar. Removing large tumors is difficult. If the tumor is a microadenoma, then the cure rates are high (greater than 80%). The operation can usually be done through the nose without an external incision. Transcranial hypophysectomy This technique approaches the tumor through the upper part of the skull and usually is the procedure of choice for large and complicated tumors. Computer-assisted surgery for tumor removal The stereotactic (from Greek: stereo—three dimensions; tactic—to probe) methods in brain tumor surgery have significantly reduced the invasiveness of surgical procedures to remove brain tumors.

29. ENDONASAL-TRANSSPHENOIDAL The operation takes place with the patient supine The head of the bed is elevated and the patient’s neck is slightly extended and rotated toward the nostril to be used for the procedure. Depending on the pre-operative assessment of the patients nasal passageway a 4 mm endoscope is used. The video monitor is positioned behind the patient’s shoulder directly opposite the surgeon’s line of vision. The 0° endoscope is used to guide the intranasal dissection and initial tumor resection. sphenoid ostia is identified and sphenoidotomy is done (infero- medially), sella turcica is identified, mucosa over sella is removed and sella bone is removed (using sickle knife/periosteal elevator/drill). Exposed duramater is cauterized and cut in a cruciate manner. After taking tissue for histopatholy, tumor resection is carried out using a suction device and ring curettes of varying diameter and orientation

30. SURGICAL TECHNIQUE All operations are performed via a single/double nostril approach. Once tumor resection is complete or residual tumor is outside the field of view, the 0° endoscope is withdrawn and a 30° endoscope is inserted. The angled lens of this endoscope provides excellent exposure of the suprasellar and parasellar regions. Rotating the 30° endoscope clockwise and counterclockwise provides visualization of suprasellar and parasellar tumor extension, including invasion into the cavernous sinus if present. Any residual tumor is resected, eliminating areas of potential tumor recurrence. Once tumor resection is complete, the area is irrigated and hemostasis is obtained. An abdominal fat graft is harvested and used to reconstruct the sellar defect, which is then sealed using surgicel and abgel. Nasal packing is done with merocel which is removed after 48 h

31. ADVANTAGES OF ENDOSCOPIC SURGERY (1) Better illumination and superior visualization as the light source is close to the target. (2) Wide angle view and visualization of the opticocarotid recess (OCRs) as well as carotid and optic protuberances. (3) Angled endoscopes expand the range of visualization including visualization of corners and hidden angles permitting complete removal of the tumor. (4) A high image resolution permitting more accurate differentiation between the diaphragm sellae and the arachnoid, and between the normal and neoplastic tissue enabling preservation of normal pituitary (5) Avoidance of nasal speculum and packing causes less postoperative discomfort and an early return to work.

32. DISADVANTAGES (1) Endoscope provides a two dimensional (2D) vision. 2) Spatial distortion of the periphery of the image occurs. (3) It has limited zoom and focus capability. (4) The 3–4 handed technique requires two surgeons. (5) The operating time is longer in the initial phase of the learning curve

33. SURGICAL TECHNIQUES Transphenoidal hypophysectomy tumor removed through the nasal cavity. Advantages are - no other part of the brain is touched, the neurological complication rate is low, and there is no visible scar. Removing large tumors is difficult. If the tumor is a microadenoma, then the cure rates are high (greater than 80%). The operation can usually be done through the nose without an external incision. Transcranial hypophysectomy This technique approaches the tumor through the upper part of the skull and usually is the procedure of choice for large and complicated tumors. Computer-assisted surgery for tumor removal The stereotactic (from Greek: stereo—three dimensions; tactic—to probe) methods in brain tumor surgery have significantly reduced the invasiveness of surgical procedures to remove brain tumors.

34. ENDONASAL-TRANSSPHENOIDAL The operation takes place with the patient supine The head of the bed is elevated and the patient’s neck is slightly extended and rotated toward the nostril to be used for the procedure. Depending on the pre-operative assessment of the patients nasal passageway a 4 mm endoscope is used. The video monitor is positioned behind the patient’s shoulder directly opposite the surgeon’s line of vision. The 0° endoscope is used to guide the intranasal dissection and initial tumor resection. sphenoid ostia is identified and sphenoidotomy is done (infero- medially), sella turcica is identified, mucosa over sella is removed and sella bone is removed (using sickle knife/periosteal elevator/drill). Exposed duramater is cauterized and cut in a cruciate manner. After taking tissue for histopatholy, tumor resection is carried out using a suction device and ring curettes of varying diameter and orientation

35. SURGICAL TECHNIQUE All operations are performed via a single/double nostril approach. Once tumor resection is complete or residual tumor is outside the field of view, the 0° endoscope is withdrawn and a 30° endoscope is inserted. The angled lens of this endoscope provides excellent exposure of the suprasellar and parasellar regions. Rotating the 30° endoscope clockwise and counterclockwise provides visualization of suprasellar and parasellar tumor extension, including invasion into the cavernous sinus if present. Any residual tumor is resected, eliminating areas of potential tumor recurrence. Once tumor resection is complete, the area is irrigated and hemostasis is obtained. An abdominal fat graft is harvested and used to reconstruct the sellar defect, which is then sealed using surgicel and abgel. Nasal packing is done with merocel which is removed after 48 h

36. ADVANTAGES OF ENDOSCOPIC SURGERY (1) Better illumination and superior visualization as the light source is close to the target. (2) Wide angle view and visualization of the opticocarotid recess (OCRs) as well as carotid and optic protuberances. (3) Angled endoscopes expand the range of visualization including visualization of corners and hidden angles permitting complete removal of the tumor. (4) A high image resolution permitting more accurate differentiation between the diaphragm sellae and the arachnoid, and between the normal and neoplastic tissue enabling preservation of normal pituitary (5) Avoidance of nasal speculum and packing causes less postoperative discomfort and an early return to work.

37. DISADVANTAGES (1) Endoscope provides a two dimensional (2D) vision. 2) Spatial distortion of the periphery of the image occurs. (3) It has limited zoom and focus capability. (4) The 3–4 handed technique requires two surgeons. (5) The operating time is longer in the initial phase of the learning curve