Extended endoscopic transsphenoidal approach for skull base lesions, basic concepts

and relevant surgical anatomy

By

Amr Mohamed MadkourAssisstant lecturer neurosurgery, Alex. University.

History of transsphenoidal approach,

• The ancient Egyptian embalmers used to remove the body organs from the thorax and the abdomen during the mummification process and preserve them in canopy, also they removed the brain through the nose so as not disfiguring the face and there are several studies on mummies made with CT and archaeologists have found the instruments used for such scope.

• David Giordano, chief surgeon of the hospital of venice, start to use the approach to the sella through an extracranial transsphenoidal approach at the end of the 19th century.

History of the approach,• later on, a series of European and American innovators, such as

Schloffer, Kocher, Hirsch, Halstead, and cushing et al. use the transsphenoidal surgery, either sublabial or directly transnasal approach.

• The approach decreased in use after that due to poor illumination and absence of antibiotics and cortisone therapy.

• The French neurosurgeon Gerard Guiot, was the one who implemented the standard procedure with the use of intraoperative fluoroscopy and extend the approach even to the supra and parasellr pathologies that was exception that time in the second half of the 50th. Gerard Guiot was the first to use the endoscope for inspection of the sellar cavity at the end of the surgical procedure in order to further and deeper inspect of the surgical dome.

History of the approach,

• Jules Hardy later added the routine use of the operating microscope. then Jules Hardy with the contribution of Rudolph Fahlbusch in Germany, and Shou in China, and Edward R, and Laws Jr in USA master the approach.

• The association of an expert in functional endoscopic sinus surgery, Ricardo Carrau and a brilliant neurosurgeon, Hae Dong Jho had been characterized the terms and modalities of the new endoscopic transsphenoidal approach to the sellar region, strictely endonasal, without the use of a transsphenoidal retractors. they perform the first case of pituitary adenoma completely endoscopic in 1996

History of the approach,

• The share of Italian surgeons, Cappabianca and de Divitiis constituted the European outpost of such more recent progress in transsphenoidal surgery since 1997and the core of the Italian connection together with Castelnuovo’s group and Frank’s group, who remove the tumors through the nose.

Amin Kassam and his group in Pennsulvania, are one the eminent teams in endoscopic skull base surgey.

Basic concepts for extended approach(according to kassam and carru)

• Two nostril approach • Middle turbinectomy, unilateral• Posterior ethmoidectomy, unilateral• Removal of the posterior portion of the nasal septum• Wide sphenoidotomy• Free hand endoscope ( three or four hand technique)

Calssic transsphenoidal approach1- Nasal phase:

2- sphenoidal phase:

Continue,

3- sellar phase:

(A) Extended endoscopic approach to the suprasellar region

• To expose the suprasellar region and planum sohenoidale, this require more anterior trajectory with wide opening of the superior portion of the anterior wall of the sphenoid sinus, with removal of the superior turbinate on one or both sides, with drilling of the bone of the tuberculum sellae and planum sphenoidalae depending on certain anatomical landmarks, the medial optocarotid recess with carotid and optic protuberance and posterior ethmoidal artery laterally, complete removal of the bone from the planum to reach the falciform ligament or even more anteriorly according to the lesion.

A, wide spenoidotomy and bilateral posterior ethmoidectomy to obtain wider view of the planum sphenoidale; B, both posterior ethmoidal arteries are visible, they usually represent a limit when opening the planum sphenoidale

endoscopic transsphenidal view after removal of tuberculum sellae and planum sphenoidale up to the falciform ligament

The suprasellar area is divided into four regions by Two imaginary planes, one passing through the inferior surface of the chiasm and mammilary bodies, and the other passing through the posterior edge of the chiasm and dorsum sellae

1- suprachiasmatic region

• suprachiasmatic region before (A), and after (B) opening the lamina terminalis

once opening the dura over the planum sphenoidale and tuberculum sellae, the chiasmatic cistern with the anterior margin of the chiasm and medial portion of the optic nerves are visible. Also the lamina terminalis cistern is exposed, once opening the arachnoid, the A1 segments, the anterior communicating, the recurrent artery of heubner, A2 segments, and gyri recti of the frontal lobes are visible

2- subchiasmatic region

• once opening the dura, the pituitary stalk below the chiasm, the superior hypophyseal artery and the perforating branches for the inferior surface of the optic chiasm and nerves are apparent. Laterally, the origin of the ophthalmic artery below the optic nerve is also visible. When the endoscope is advanced below the chiasm, lateral view shows the ICA, its bifurication, and the first A1 segment before it reaches the superior surface of the chiasm.

3- retrosellar region,

• that can be reached by passing the endoscope between the pituitary stalk and ICA above the dorsum sellae. We can see from inferior to superior, the upper third of the basilar artery and the pons below it, the posterior cerebral artery, the superior cerebellar arteries, the occulomotor nerve, the mammillary bodies, and the floor of the third ventricle

4- ventricular region,

• it appears by passing the endoscope into the retrosellar space shows the floor of the third ventricle in front of the mammillary bodies. Opening the floor allows access to the ventriclular cavity. The lateral ventricle walls formed by the medial portion of the thalami are visible with the interthalamic commissure. The foramina of Monro are visible superiorly. Then follow the interthalamic adhesion toward the posterior ventricle wall

Ventricular region, cont,

• Once opening of the roof of the third ventricle, the pineal gland and internal cerebral veins lateral to the pineal gland are visible.

• the endoscope passes below the interthalamic adhesion, the pineal gland and both internal cerebral veins are visible

Transtuberculum, transplanum approach

• Most commen pathologies that can be removed through this approach including:

- craniopharyngioma - tuberculum sellae meningeoma - pituitary adenomas - ect,

• de Divitiis E, Cappabianca P, Cavallo LM. Endoscopic

transsphenoidal approach: adaptability of the procedure to

different sellar lesions. Neurosurgery 2002 ;51(3):699-705.

23y female patient complaining of headache , with bitemporal hemianopia, no hormonal disturbance

Operated for extended endoscopic transsphenoidal removal of the tumor,( cystic craniopharyngioma)

Postopertive MRI shows complete removal of the tumor

45y female patient complaining of severe headache, no hormonal disturbance, with rt superior quadrantanopia

Operated for extended endoscopic approach for removal of tuberculum sellae meningeoma

Postoperative MRI shows complete tumor removal

(B) Extended endoscopic approach to the olfactory groove

• This approach facilitates dealing with lesions affecting the cribriform plate and called transcribriform approach, (crista galli and olfactory sulci)

.(A), the asterisks marks the olfactory sulcus; EC, ethmoid cell; LP, lamina papyracea; mewl, medial wall of ethmoid labyrinth; Pp, perpendicular plate of the ethmoid; OP, optic protuberance. (B), The ethmoidal arteries have been isolated on both sides and the cribriform plate is removed thus exposing the dura. AEA, anterior ethmoidal artery; O, orbit; dm, dura matter; ICAs, sellar portion of the ICA.

The superior portion of the lamina papyracea is removed,and the anterior and posterior ethmoidal arteries are isolated

and ligated on both sides. The bone of the anterior skull base between the orbits is removed and the dura mater is opened, allowing exposure of the intracranial contents. The olfactory nerves and the basal surfaces of the frontal lobes are initially visualized By

retractingthe medial surfaces of the frontal lobes, it is possible to expose the two pericallosal arteries in the interhemispheric fissure

Transcribriform approach,

• It is possible to deal with the following lesions through this approach:

1- CSF leak 2- meningocele, encephalocele 3- ethesioneuroblastoma 4- olfactory groove meningeomas 5- other skull base malignancies. Limits of bone resection:- Posterior wall of the frontal sinus- Medial wall of the orbit- Posterior ethmoidal arteries (+, -)

37y male patient presented with heaadche and anosmia, operated for endoscopic transcribriform approach for tumor removal

(C) Extended endoscopic approach to the the upper clivus

• After removal of the middle turbinate on one side, and wide anterior sphenoidotomy with removal of all septa and removal of the posterior portion of the nasal septum, we begin to detach the nasal mucosa from the vomer and along the inferior wall (floor) of sphenoid sinus and the mucosa dissected laterally till the vidian nerve which represent the lateral boundary of the surgical corridor. This mucosal flab dissected inferiorly in the nasal cavity and can be used for repair later on. According to the tumor extension, we begin to remove the bone of the clivus till the sella superiorly, paraclival tracts of the ICA laterally, and below the level of the paraclival carotid inferiorly.

A- the nasal mucosa has been dissected around the vomer and laterally toward the vidian canal and nerve which is important surgical landmark B- after drilling of the upper half of the clivus and exposure of the dura matter

The bone of the clivus and bone covering the intracavernous carotid has been removed completely exposing the paraclival carotid, the dorsal meningeal artery and the abducent nerve behind the paraclival segment of

intracavernous carotid.After opening the dura we see the basilar artery and pons, the course of abducent nerve from its origin to the

cavernous sinus

(D) Extended endoscopic approach to the lower clivus and craniocervical junction and C1

• This approach can be considered the extreme inferior extension of the previously described endoscopic approach to the clivus.

• we extend the bone removal to the posterior portion of the vomor and the whole sphenoid floor to access the lower clivus. In this way we achieve wide exposure of the sphenoid cavity, the rhinopharynx, and sphenoclival region down to C1.

The image shows the lower clivus the rhinopharynx and eustachian tubeafter removal of the lower clivus we can see the foramen lacerum which is important

surgical landmark and the lateral limit of the approach at this level

The mucosa of the rhinopharynx has been removed and the longus capitis and the longus colli muscles have been dissected to expose the

craniovertebral junction

(E) Extended endoscopic approach to parasellar region and cavernous sinus

• this drawing shows the middle third of the clivus and petrous bone in coronal plane, the five zones in black boxes. Zone 1, medial petrous apex approach; zone 2, petroclival approach; zone 3, inferior cavernous (quadrangular space) approach; zone 4, superior cavernous sinus approach; zone 5, trans pterygoid infratemporal fossa approach. CS, the cavernous sinus above; V, vidian canal leading to the ICA; J, jugular vein.

Extended endoscopic approach to the infratemporal fossa

• this area can be reached through removal of the medial and posterior maxillary wall, the medial pterygoid plate (MPP) and extending upward until in flush with the middle cranial fossa and foramen rotundum. And extending laterally to the lateral pterygoid plate (LPP) that should be removed to reach the infratemporal fossa

endonasal skull base reconstruction,

• It is the most important step that we should prepare for it before starting bone removal

• The principles of repair, ( according to cappapianca and cavallo) :1- reduce CSF pulsatile effect on the skull base defect2- sandwich closure of the osteo dural skull base defect3- cover skull base defect by free mucosal flab(+,-)4- sphenoid sinus ballon stenting for two weeks 5- lumber drainage for 3-5 days

Sandwich tichnique

- intradurally: 1. dural layer 2. fat layer 3. dural layer- extradurally: dural layer

Take home message

• Endoscopic work has steep learning curve• Attending cadaveric workshops is very important to understand

the relevant surgical anatomy of extended approach• Be sure that the room setup is well prepared for extended

approach• Aided tools such as dopler probe and neuronavigation should be

available• We should design the plan of bony work and methods of repair

from the start and should be individualized according to the case• Put in mind that repair is the most important step in the operation

References,

• Cavallo LM, Messina A, Cappabianca P. Endoscopic endonasal surgery of the midline skull base: anatomical study and clinical considerations. Neurosurg Focus 2005; 19:E2.

• Aydin S, Cavallo LM, Messina A. The endoscopic endonasal transsphenoidal approach to the sellar and suprasellar area. Anatomic study. J Neurosurg Sci 2007; 51:129-38.

• Kassam A, Gardner P, Snyderman C, Mintz A, Carrau R. Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the clivus, petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg. Focus, volume 19, July 2005.

• Cavallo LM, De Divitiis O, Aydin S, et al. Extended endoscopic endonasal transsphenoidal approachto the suprasellar area, anatomic consideration- part1. Neurosurg 61: ONS-24- ONS-34, 2007.

References,

• Guiot J, Rougerie J, Fourestier M, Fournier A, Comoy C, Vulmiere J, Groux R. International endoscopic explorations. Presse Med 1963; 71: 1225-1228.

• Giordano D. Compendio di chirurgia operative italiana. UTET, Torino 1911, pp 100-103.

• Cushing HW. The pituitary body and its disorders: clinical states produced by disorders of the hypophysis cerebri. JB Lippincott, Philadelphia, 1912; pp296-305.

• Hardy J. Transsphenoidal hypophysectomy. J Neurosurg 1971; 34: 582-594.• Jho HD, Carrau RL, Ko Y. Endoscopic pituitary surgery. In: Reganchary SS,

Willkins RH (eds) Neurosurgical operative atlas. American Association of Neurological Surgeons, Park Ridge, 1996, IL, pp1-12.

• Carrau RL, Jho HD, Ko Y. Transnasal transsphenoidal endoscopic surgery of the pituitary gland. Laryngoscope, 1996; 106: 914-918

Thank you for your attention