anatomical description of basic anatomy required to understand the endoscopic endonasal procedures for skull base surgery

1. Endonasal Endoscopic
Anatomy
Presented By –
Dr. Rahul Jain
Moderated by : Dr V.C. Jha
HoD Deptt of Neurosurgery,
AIIMS Patna

2. Background
• Hermann Schloffer (1907) performed the first
transsphenoidal pituitary surgery via a lateral
rhinotomy approach
• Oscar Hirsch and Harvey Cushing attempted to
refine the technique in 1910.
• In 1965, Hardy was the first to use a microscope to
approach the sella, pioneering the transsphenoidal
approach.
• use of the endoscope was first described by Jho
and Carrau in 1997.

3. Advantages of an Endoscope
• The endoscope can physically enter into the
sphenoid sinus and provide a wide-angled
panoramic view with zooming capability.
• endoscope shows a diverging flask-shaped wide-
angled view.
• Angled views may be advantageous when large
suprasellar macroadenomas are to be removed or
direct visualization of the medial wall of a
cavernous sinus is required.

4. Microscope vs Endoscope
Parameter Microscope Endoscope
Fogging No Yes
Vision 3D 2D
Hemostasis Good Difficult
Dissection Good (Bimanual) Difficult
Exposure Tubular Panoramic
Extent of visualisation Narrow Wide
Extent of removal ++ ++++
C-Arm Yes Yes/No
Nasal Packing Yes Yes/No

6. Sinonasal Anatomy
Nasal Cavity is bordered
• medially – nasal septum (composed of the septal
cartilage, the perpendicular plate of the ethmoid bone,
and the vomer);
• superiorly by the cribriform plate of the ethmoid bone
and bridge of the nose (consisting of the nasal portion
of the frontal bone, nasal bone, and frontal process of
the maxilla);
• inferiorly by the floor of the nasal cavity (involving the
palatine process of the maxilla and the horizontal plate
of the palatine bone); and
• conchae or turbinates laterally (inferior, middle,
superior, and sometimes supreme turbinates).

8. • The superior and middle conchae (along with the
occasional supreme concha) are components of the
ethmoid bone, whereas the inferior concha is a
separate bone.
• The EE-TS procedure traverses the,region medial to
the middle turbinate, between the middle
turbinate and the nasal septum, on the way to the
sphenoid sinus then the pituitary fossa at the sella
turcica.

9. Osteomeatal Complex
• normal sinonasal anatomy located laterally to the
middle turbinate is referred to as the osteomeatal
complex (OMC) and comprises a key set of
structures for sinonasal function.
• consists of the middle turbinate, uncinate process,
hiatus semilunaris, ethmoid infundibulum, and
ethmoid bulla.

10. Hiatus semilunaris is
essentially a two-
dimensional (2D) crescent-
shaped opening leading
from the middle meatus
into the three-dimensional
(3D) funnel-shaped
ethmoid infundibulum to
which the frontal sinus,
anterior ethmoid sinus,
and maxillary sinus usually
drain.

12. • important point is that there are individual structural
variations, which can affect paranasal sinus physiology
and surgical anatomy.
• When the path of physiologic mucus flow is interrupted
mechanically or functionally, the paranasal sinuses can
retain stagnant mucus, which can subsequently
become infected and result in sinusitis.
• Anatomic variations may also include a pneumatized or
aerated turbinate, most frequently the middle
turbinate, which is referred to as concha bullosa and
can be enlarged.

13. • Despite these variations or the presence of any
nasal polyps, the main point is that structures of
the OMC should not be significantly disturbed en
route to the sphenoid sinus during EE-TS.

14. Ethmoidal Air Cells Variations
1. Agger Nasi cells
• Most anterior ethmoidal cells located just anterior
and lateral to the nasofrontal recess.
• For EE-TS, the surgeon should be aware that a
hyperpneumatized agger nasi cell can occasionally
present as a bulge that mimics the anterior view of
a turbinate.

15. 2. Haller cells
• infraorbital ethmoid air cells or
maxilloethmoidal cells.
• closely related to the ethmoid
infundibulum along the medial
roof of the maxillary sinus.
• Because Haller cells are quite
lateral, these usually do not
present a problem during EE-TS,
although their proximity to the
ethmoid infundibulum can
result in inadvertent orbital
entry if not recognized.

16. 3. Onodi Cells
• sphenoethmoidal cells
• posterior ethmoidal air cells that can project superiorly
into the sphenoid sinus toward the lateral side and can
potentially be confused with a septated region of the
sphenoid sinus.
• optic nerve and/or internal carotid artery (ICA) can
bulge into Onodi cells instead of the sphenoid sinus
proper or occasionally may have either partial or
complete bony dehiscence at the sphenoid sinus,
presenting risk for injury during surgery.

18. Nasal Turbinates
• inferior turbinate (IT) extends along the length of
the nasal cavity. Mucosal inferior turbinate
hypertrophy is its most common variation and may
narrow the nasal corridor space, but it usually
shrivels with the use of topical decongestants.
• middle turbinate (MT) has three attachments in the
sagittal, coronal and horizontal planes from an
anterior to posterior direction. MT presents with
many variations, its pneumatisation being the
commonest.

19. • A pneumatised MT, known as the concha bullosa,
needs to be opened (by means of conchoplasty), before
lateralising the MT. Sometimes, the MT may be
bulbous, owing to its bony structure, in which case,
conchoplasty cannot be performed, Neither can it be
lateralised easily to achieve wide nasal corridor.
• In such cases it is advisable to sacrifice the MT. We also
perform middle turbinectomy in cases which require
extended trans-sphenoidal route, transpterygoid route
or in paediatric patients, in whom adequate space is of
prime importance during the surgery.

20. • superior turbinate (ST) carries majority of the
olfactory fibres. Hence superior turbinectomy is
generally avoided to maintain post-op olfaction.
• In cases which require extended endoscopic trans-
sphenoid surgery, or in cases (where the sphenoid
is filled with pathology and the landmarks are
difficult to visualise, or in cases where space is
premium (for parking the endoscope, partial
superior turbinectomy is done and the posterior
ethmoids are opened.

21. Right partial superior turbincetomy done to expose posterior ethmoid cells
(white arrow)

22. Vasculature of Nasal Septum
• The blood supply originates from the ophthalmic
branch of the internal carotid artery (ICA) and
maxillary and facial branches of the external carotid
artery (ECA).
• The blood supply to the upper nasal septum is from
the anastomosis of anterior and posterior
ethmoidal arteries which are branches of
ophthalmic artery.

23. • Majority of nasal septum is supplied by
Sphenopalatine artery (SPA), branch of ECA.
• SPA perfuses the posterior and inferior division of
septa.
• SPA enters the nasal cavity through sphenopalatine
foramen where it divides into 2 major branches
namely septal and posterior lateral nasal artery.

24. • Septal artery exits SP foramen, courses through
rostrum of sphenoid and distributes the nasal
septum with 2-3 branches. Hence nasoseptal flap
should be wide enough including atleast 2-3
branches to maintain its viability.

26. Anatomic Landmarks in Stages of
EE-TS Pituitary Surgery
4 stages
1. Nasal stage
2. Sphenoid stage
3. Sellar stage
4. Reconstruction stage
Recognition of important landmarks during each of
these stages is the key to a safe exposure.

27. Nasal Stage
• endoscope is inserted in line with the floor of the
nasal cavity, parallel to the MT at an angle of 25°
inferiorly to initially visualize the choana.
• choana is the anatomic reference point.
• inferior margin of the MT leads to clival
indentation, which is about 1 cm, below the level of
sellar floor. This is quite a consistent surgical
landmark.

29. • Hadad Bassagasteguy (HB) flap is most commonly
used nasoseptal flap to seal off meninges from
nasal cavity and harvested prior to tumor
dissection. It is local, robust, easily harvestable flap.
• Based on sphenopalatine artery it is considered
gold standard for endoscopic skull base
reconstruction.
• Landmarks for harvesting HB flap – sphenoid
ostium, ST, MT, Eustachian tube, Choanal arch,
Mucocutaneous junction of septum.

31. • Factors determining side on which HB flap is taken:-
• Sharp spur which might lead to tear
• Lateral extension of sella tumor
• Lateral sphenoid CSF leak which requires sacrifice of septal
branch.

32. Sphenoid Stage
• sphenoid ostium (SO) is identified posterior and
inferior to the root of the ST in the lateral rostral
corner of sphenoid rostrum.
• Submucosal dissection along the contralateral side
of the sphenoidal rostrum to visualize the
sphenoidal ostium (SO) contralateral to the side of
approach gives the classical “owl eye appearance”.

33. • vomer is drilled and the rostrum of the sphenoid sinus
is removed
• The limits of the sphenoidotomy include: Cranially, the
superior limit of SO providing adequate visualization of
the planum sphenoidale, the optico-carotid recesses
and the optic protuberances; caudally, the
pterygo-sphenoid synchondrosis/vidian canal at 5 and 7
O’ clock position.
• The lateral limit is the crest marking the the junction of
the sphenoid and ethmoid sinuses with visualization of
the carotid artery (CA) protuberance.

34. Sellar Stage
• sphenoidal mucosa located only on the anterior
wall of the sella and the floor is coagulated with a
bipolar and excised.
• Anatomical landmarks are identified in the aerial
panoramic view and mimic a “fetal face”.
• Gentle drilling with a diamond burr under low
speed is done to thin the sellar floor to an egg shell
thickness.

36. • The anterior wall of the sella and its floor is
removed millimeter by millimeter circumferentially
till four blue lines (both the superiorly and inferiorly
located inter-cavernous sinuses and the laterally
located cavernous sinuses) are seen.

38. References
1. Schmidek and Sweet’s operative neurosurgical
techniques 7th Ed. Vol 1
2. Youmann’s and Winn Neurological surgery 8th Ed.
3. YR Yadav, BS Sharma – Neuroendoscopic Surgery.
4. Sharma BS, Sawarkar DP, Suri A. Endoscopic
pituitary surgery: Techniques, tips and tricks,
nuances, and complication avoidance. Neurol
India 2016;64:724-36

39. THANK YOU