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3.
ENDOSCOPIC ANATOMY ALONG
THE TRANSNASAL APPROACH TO THE PITUITARY
GLAND AND THE SURROUNDING STRUCTURES
M. Tschabitscher and R. J. Galzio
"The nasal route is impracticable and can be never otherwise", Dandy, 1945 [2]. This
assumption of one of the greatest neurosurgeons of the 20th century proved to be wrong.
The idea of reaching the pituitary along the preformed route through the nose and the
sphenoid sinus goes back to Davide Giordano's [4] theoretical considerations in 1894.
Schloffer [13] first practically tried to access the pituitary by reflecting the nose and
removing most of what is inside it, i.e. the nasal septum, the turbinates and the ethmoid.
Kanavel [8] only reflected the lower half of the nose and thus spared the ethmoid, while
Halstead [5] used a sublabial approach. With Hirsch's [6, 7] work the transnasal approach
made its first breakthrough in 1909.
Quite variable in size and shape and rarely symmetrical, the nasal and paranasal
sinuses form a complex system of cavities just above the oral cavity, which is divided into
ｾｯ＠
separate units by the nasal septum.
3.1
Nasal cavity
3.1.1
Development
The nose begins to develop in the 5th week at an embryonic size of about 5 mm with the
appearance of the olfactory placode from the ectoderm [1]. From it the olfactory sacs are
derived by impression and invagination from the olfactory pits and extend to the roof of the
primitive oral cavity. The epithelial lining of the olfactory sacs fuses with the epithelium of
the oral cavity to form the oronasal (bucconasal) membrane. Rupture of this membrane in
the 6th week of embryonic development gives rise to the primary choanae]. The primitive
palate separates the oral and nasal cavities anteriorly. The left and right primitive nasal
cavities are divided by the nasal septum, which grows downward from the medial frontal
process. At the same time, the palatine processes sprout out from the maxillary processes
and grow toward medial and caudal. They continue to grow horizontally as the tongue
subsides and make contact anteroposteriorly with the primitive palate. The posterior part
remains patent craniocaudally and develops into the pharynx [1].
3.1.2
Bony skeleton of the nasal cavity
The two nasal cavities resemble truncated pyramids. They are enclosed by a roof
(= cribriform plate), a floor (= hard and soft palate), a medial wall (= nasal septum), a
lateral wall (= ethmoid and maxillary bones + inferior nasal turbinate), a posterior wall
(= body of sphenoid bone) and an anterior wall (= external nose).
The roof is formed by a number of bony elements. These include the nasal bone, the
frontal process of the nasal bone, the cribriform plate of the ethmoid and the most anterior
part of the sphenoid body.
The floor is composed of the palatine process of the maxillary bone (and the
intermaxillary bone [Goethe] = premaxilla) anteriorly, which forms a synostosis with
the maxilla early at an embryonic size of 20 mm, and the horizontal plate of the palatal
bone.
E. Divitiis et al. (eds.), Endoscopic Endonasal Transsphenoidal Surgery
© Springer-Verlag Vienna 2003
M. Tschabitscher and R.
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J.
Galzio
Fig. 3-1 . Lateral wall of the nasal cavity.
1: inferior nasal turbinate, 2: middle nasal turbinate, 3: superior nasal turbinate, 4: frontal
sinus, 5: anterior ethmoid cells, 6: posterior ethmoid cells, 7: sphenoid sinus, 8: pituitary
The medial wall is contributed by the nasal septum. It consists of three parts of different
tissues: the fibrous columella (pars mobilis) anteriorly, the cartilaginous part (pars
cartilaginea) behind it and the bony part (pars ossea), i.e. the perpendicular plate of the
ethmoid and the vomer, posteriorly.
The lateral wall accommodates three nasal turbinates. In just under 20% of cases there
may be 4 (supreme nasal turbinate). The inferior nasal turbinate is a separate bone. Below it
the nasolacrimal duct empties into the inferior nasal meatus. The middle and superior nasal
turbinates are part of the ethmoid. The anterior margin of the middle turbinate is about 2 cm
posterior to the anterior margin of the inferior turbinate. Below it the maxillary sinus, the
frontal sinus and the anterior ethmoid air cells open into the nasal cavity through the hiatus
semilunaris, wh ich is bordered by the ethmoid bulla and the uncinate process. The tail of
the middle turbinate lies approximately at the level of the sphenopalatine foramen (this is
important for identifying arterial bleeding sources.) Below the superior turbinate the
posterior ethmoid air cells open into the nasal cavity (Fig. 3-1).
3.1 .3
Lining of the nasal cavity
The nose is part of the upper airways and is mainly lined by respiratory tract epithelium
(= ciliated epithelium with goblet cells and seromucous glands). The nasal vestibulum is
an exception because it is lined by multi-layer keratinized squamous epithelium (= facial
skin) and olfactory epithelium overlying the superior nasal turbinate and the nasal septum
opposite it.
The anterior inferior part of the nasal septum accommodates a mucosal recess of
variable depth, the vomeronasal organ (Jacobson's organ) (Fig. 3-2).
3.1.4
Vessels and nerves of the nasal cavity
Two major arteries supply the nasal cavity, i.e. the ophthalmic and the maxillary artery.
The ophthalmic artery supplies the inner nose anterior to the nasal turbinates with its
anterior ethmoid branch. Its posterior ethmoid branch carries blood to the superior nasal
Endoscopic anatomy
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Fig. 3-2. Anteriormost nasal segment.
7: mobile part of the nasal septum (columella), 2: inferior nasal turbinate, 3: vomeronasal
organ of Jacobson, 4: agger nasi, 5: middle nasal turbinate
Fig. 3-3. Posterior nasal segment.
7: inferior nasal turbinate, 2: middle nasal turbinate, 3: superior nasal turbinate, 4: ethmoid
bulla, 5: opening of the posterior ethmoid cells, 6: posterior ethmoid cell, 7: sphenoid
sinus, +-+ branches of sphenoethmoidal artery
turbinate and the anterior half of the middle turbinate. The maxillary artery gives off the
sphenopalatine artery in its pterygopalatine segment: this artery supplies the middle and
inferior turbinates with its lateral posterior and posterior septal branches from behind and
the inferior two thirds of the septum (Figs. 3-3, 3-4).
M. Tschabitscher and R.
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J.
Galzio
Fig. 3-4. Dissection of the sphenopalatine artery as it passes through the sphenopalatine foramen.
The posterior end of the middle turbinate is slightly retracted anteriorly to bring into view
the division into a superior and an inferior branch.
1: inferior nasal turbinate, 2: middle nasal turbinate, 3: superior nasal turbinate, 4:
sphenopalatine artery, 5: sphenoid sinus
The veins generally accompany the arteries and usually form a plexus.
The lymphatics draining the areas anterior to the nasal turbinates ultimately empty into
the submandibular nodes, those draining the posterior area and the paranasal sinuses into
the retropharyngeal and deep cervical nodes at the level of C2.
The sensory innervation of the nose is derived from the first branchial arch and thus
belongs to the trigeminal system. The ophthalmic nerve basically serves the same territory
as the ophthalmic artery. The maxillary nerve supplies the lateral wall of the nasal
cavity and the middle and inferior nasal turbinates with its lateral branches. Scarpa's
nasopalatine nerve from the medial group of the maxillary nerve passing the sphenopalatine foramen extends to the incisive canal and supplies the gingiva overlying the
incisive bone.
The terminal and vomeronasal nerves probably are subservient to perception during
embryonic development, but are largely lost postnatally.
3.2
Sphenoid sinus
The sphenoid sinus, which is derived from two mucosal evaginations at the posterior wall
of the nasal cavity, is initially paired. Its development begins in the third month of fetal life
Endoscopic anatomy
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and is completed about the end of puberty. Parts of its wall (conchae sphenoidales)
originate from the ethmoid anlage. They enclose the right and left natural openings of the
sphenoid sinus. Three sinus types are distinguished by their shape and size:
• Concha I type: anterior to the pituitary fossa (3%) (Fig. 3-5);
• Sellar type: extending to beneath the pituitary fossa (80%) (Fig. 3-6);
• Retrosellar type: extending to the clivus (17%) (Fig. 3-7).
The space within the sphenoid body is subdivided by one or several septa [141. (Single
septa are not always located in the midline!) The sphenoid sinus roughly resembles a
cube, which is subdivided in 2 halves by the septum. These halves are of different size in
65 to 70% of cases. Its walls are composed of 6 parts.
The roof is part of the anterior segment of the anterior cranial fossa and extends from
the jugum (= planum) sphenoidale to the limbus of the sphenoid. Behind it is the sella
turcica with the prechiasmal sulcus in between.
Fig. 3-5. Sphenoid sinus - concha I type (mediosagittal section) .
1: clivus, 2: sphenoid body, 3: posterior clinoid process, 4: sellar bridge, 5: anterior clinoid
process, 6: posterior ethmoidal cell, 7: sphenopalatine foramen. _
to the sphenoid sinus
- .... +-- spheno-occipital synchrondrosis
Fig. 3-6. Sphenoid sinus - sellar type.
1: clivus, 2: sphenoid sinus, 3: incomplete septum in the frontal plane, 4: sphenoid ostium,
5: sphenopalatine canal, * optico-carotid recess
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M. Tschabitscher and R. J. Galzio
Fig. 3-7. Sphenoid sinus - retrosellar type.
1: sphenoid sinus, 2: clivus
Fig. 3-8. Lateral extension of the sphenoid sinus into the pterygoid process.
1: posterior ethmoid cell, 2: sphenoid ostium, 3: lateral evagination of sinus into pterygoid
process, 4: clivus, * spheno-occipital synostosis
The floor forms the roof of the choanae anteriorly and the roof of the nasopharynx
posteriorly. Medially the pterygoid canal of Vidianus is recognizable as a bulge. (It should
not be mistaken for a septal remnant.) Laterally, at the junction with the lateral wall, the
maxillary nerve may form another bulge (Figs. 3-8, 3-9).
The medial wall is formed by the septum.
The lateral wall also forms the bony medial wall of the cavernous sinus. A recess of
variable size, optico-carotid recess, is located between the bulge of the optic nerve
and that of the internal carotid artery. This recess may be quite deep and extend
well into the anterior clinoid process. It should not be mistaken for an Onodi-Grunwald
cell. Bone dehiscences of variable age-related extension may be present above the
carotid.
The lateral wall has paired natural apertures medially and is contiguous with the
posterior ethmoid cells.
The posterior wall is contributed by the clivus.
Endoscopic anatomy
27
Fig. 3-9. Multi-septated sphenoid sinus extending inferiorly into the pterygoid process - frontal
section viewed from anterior.
1: foramen rotundum, 2: pterygoid canal of Vidianus, 3: pterygoid process, 4: pneumatized
anterior clinoid process, 5: optic nerve canal , 6: planum sphenoidale, * sphenoid sinus
3.2.1
How to reach the opening of the sphenoid sinus
The opening of the sphenoid sinus may be reached along two different routes:
From the upper choanal border along the posterior pharyngeal wall upwards into the
spheno-ethmoid recess (Fig. 3-10). This approach should be strictly medial along the
septum, lest a "maxillary fontanel" (that means an accessory opening of the maxillary
sinus present in about 10 to 20% of cases) be mistaken for the ostium sphenoidal is.
Fig. 3-10. Access to the sphenoid ostium from the upper
choanal border.
1: choana, 2: inferior nasal turbinate, 3: nasal
septum, 4: superior nasal turbinate, 5: middle nasal
turbinate, - sphenoid ostium, + .. maxillary sinus
fontanels, * branch of sphenopalatine artery
M . Tschabitscher and R.
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Galzio
Fig. 3-11. Access to the sphenoid ostium through the center of the middle nasal turbinate.
1: too steep, 2: right, 3: too flat
From the anterior nasal spine precisely through the center of the middle nasal turbinate
towards posterior. (Care should be taken to avoid an excessively steep and an excessively
flat approach. The former would lead into the cribriform plate, the latter deep into the
posterior cranial fossa) (Fig. 3-11).
3.3
Ethmoid labyrinth (complex)
The ethmoid cells are interposed between the lateral nasal wall and the medial orbital
wall. The 5-sided perpendicular plate of the ehtmoid (upper part of the bony nasal septum)
Fig. 3-12. Isolated ethmoid. Left - from anterior; right - from above.
1: crista galli, 2:cribriform plate, 3: ethmoid cells, 4: lamina papyracea, 5: perpendicular
plate of the ethmoid, 6: middle nasal turbinate, * anterior ethmoid canal (foramen)
Endoscopic anatomy
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divides the ethmoid into two halves. The cribriform plate is horizontal and lies between
the frontal bones. The ethmoid cells are suspended from its lateral margin like the side
bags of a motorcycle (Fig. 3-12). Between the sagittal borders, i.e. the upper and middle
turbinates medially and the lamina papyracea laterally, thin-walled chambers are present.
These communicate with one another or open into the nasal cavity. The ethmoid cells are
divided in three groups, i.e. anterior, middle and posterior. A factitious perpendicular
plane drawn through the anterior ethmoid canal (foramen) helps to distinguish the anterior
and middle from the posterior cells. The anterior cells open below the middle turbinate
into the middle meatus, the posterior cells open below the superior turbinate into the
superior meatus. There is, however, considerable variation (14).
3.4
Sellar region
The sphenoid body lies in the center of the cranial base (Fig. 3-13). Atransverse bulge, the
sellar tubercle, demarcates the sella turcica anteriorly. Anterior to it the prechiasmal
sulcus (12) extends towards the optic nerve canal and demarcates the planum
sphenoidale. Sometimes the planum sphenoidale has a right and left extension: medial
clinoid process. Ossification of the dura mater bridging from the anterior to the medial
cI,inoid processes gives rise to a carotico-clinoid foramen (foramen of Henle), (,.....,10% of
cases) (Fig. 3-14).
An ossified dural bridge (taenia interclinoidea, sellar bridge) between the anterior and
posterior clinoid processes is found in approximately 6% of cases. The sella turcica is
bordered posteriorly by the dorsum sellae. Between the dorsum and the sellar tubercle lies
the pituitary fossa. Its roof is formed by the sellar diaphragm, a dural fold perforated
Fig. 3-13. Sellar region.
1: planum sphenoidale, 2: prechiasmal sulcus, 3: sellar tubercle, 4: optic nerve canal, 5:
anterior clinoid process, 6: medial clinoid process, 7: posterior clinoid process, 8: dorsum
sellae, 9: carotid sulcus, 10: foramen rotundum, 11: foramen of VESALIUS
M. Tschabitscher and R.
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Galzio
Fig. 3-14. Variants of the sellar region .
1: optic nerve canal, 2: anterior clinoid process, 3: medial clinoid process, 4: posterior
clinoid process, 5: carotico-clinoid foramen of Henle, 6: sellar bridge
for accommodating the pituitary stalk. The width of this opening increases with age.
The inferior aspect of the diaphragm and the pituitary capsule are separated by an arachnoid
invagination: the hypophyseal cistern of Ferner (3). With its lateral extension the diaphragm
contributes to the superior wall of the cavernous sinus. Called "Wannenregion" by Lang (9),
this region is the key for the access to the cavernous sinus from above posterior to the anterior
clinoid process. (It roughly coincides with the 2 triangles of Dolenc + Hakuba.) It is
demarcated laterally by the anterior petroclinoid fold. The lateral wall ofthe sella turcica also
constitutes the bony medial wall ofthe cavernous sinus. The right lateral wall is significantly
steeper than that on the left side (9). In the carotid sulcus the internal carotid artery arches
from lateral and posteroinferior towards medial and anterosuperior. Its anterior end comes to
lie deep to the clinoid process and medial to the superior orbital notch.
3.5
Suprasellar region
Perneczky (11) equated the suprasellar region with an "equilateral pyramid". Its base is
formed by the sellar diaphragm. The sides of the pyramid contain the following structures:
the lamina terminal is, the anterior aspect of the optic nerve chiasm, the two optic nerves
and the anterior communicating artery complex with the Aland A2 segments anteriorly;
the optic tract, the internal carotid artery and 3 parallel structures, i.e. the posterior
communicating and the anterior choroidal arteries and the third cranial nerve, laterally;
and the interpeduncular fossa with the basilar tip and its division into the posterior
Endoscopic anatomy
31
cerebral and superior cerebellar arteries as well as the exit of the third cranial nerve
posteriorly. The infundibulum and the stalk of the pituitary mark the geometrical axis of
the pyramid. The stalk and anterior lobe of the pituitary are supplied by the superior
hypophyseal artery from the internal carotid artery [12]. These vessels typically are
parallel to the long axis of the stalk thus giving it a unique appearance (Fig. 3-17).
Fig. 3-15. The "equilateral pyramid" of the suprasellar region . Geometrical drawing from Perneczky Tschabitscher - Resch: Endoscopic Anatomy for Neurosurgery (by courtesy ofThieme Verlag)
Fig. 3-16. Structures found on the sides of the pyramid.
1: optic nerve, 2: optic chiasm, 3: optic tract, 4: lamina terminal is, 5: anterior cerebral
artery (A 1), 6: internal carotid artery, 7: pituitary stalk
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M. Tschabitscher and R.
J. Galzio
Fig. 3·17. Blood supply of the pituitary stalk.
1: superior hypophyseal artery, 2: internal carotid artery, 3: sellar diaphragm, 4: dorsum
sellae, 5: chiasmal branches
The posterior pituitary is supplied by the inferior hypophyseal artery from the
meningohypophyseal trunk (= truncus carotico-cavernosus posterior) [10). Rarely, it
receives blood directly from the intracavernous internal carotid artery.
3.6
Parasellar region
The parasellar region more or less corresponds to the cavernous sinus. Correctly we have
to subdivide the parasellar area into an extra and intracavernous part. Its roof is formed by
the "Wannenregion" described above (Figs. 3-18, 3-19).
Fig. 3·18. Roof of the cavernous sinus (Lang's "Wannenregion" ).
1: optic nerve, 2: oculomotor nerve, 3: Lang's "Wannenregion", 4: trochlear nerve, 5:
anterior clinoid process, 6: lateral wall of cavernous sinus, 7: temporal lobe
Endoscopic anatomy
33
Fig. 3-19. Cavernous sinus opened along the anterior petroclinoid fold.
1: oculomotor nerve, 2: Lang's " Wannenregion", 3: cavernous sinus (opened), 4:
trochlear nerve
Structures within the roof include, from anterior to posterior, the second cranial nerve,
the internal carotid artery (usually with the origin of the ophthalmiC artery), the third
cranial nerve and the triangular field of the fourth cranial nerve (Hakuba's triangle) at its
Fig. 3-20. Posterior part of sinus roof (opened).
1: ligament of Gruber, 2: abducent nerve, 3: oculomotor nerve, 4: superior cerebellar
artery, 5: trigeminal nerve, * canal of Dorello
34
M. Tschabitscher and R.
J.
Galzio
posterior end. The third cranial nerve lies lateral to the posterior clinoid process and
medial to the anterior petroclinoid fold. After its long intracranial course the fourth cranial
nerve passes between the anterior and posterior petroclinoid folds lateral and posterior to
the third cranial nerve and enters the roof of the cavernous sinus to proceed to its lateral
wall. 1.5 to 2 cm inferior and medial to the posterior clinoid process the 6th cranial nerve
enters the dural port between the periosteum (stratum periostale) and the dura (stratum
durale), which accommodates a venous plexus (3). It approaches the cavernous sinus
from posterior near the tip of the petrous bone. At this site it is usually crossed by a well
developed ligament (superior sphenopetrosal ligament of Gruber). Ossification of this
ligament gives rise to an abducent nerve foramen (foramen of Wegner) (Fig. 3-20).
Fig. 3-21. Mediosagittal section through sphenoid sinus. For easier distinction the arterial system is
shown in red and the venous system in blue. The mucous membrane and the bony sinus
wall were preserved to illustrate the bulges formed by the structures lateral to them .
1: pituitary, 2: optic nerve and ophthalmic artery, 3: internal carotid artery, 4: opticocarotid recess, 5: ophthalmic nerve, 6: maxillary nerve
Fig. 3-22. View into the cavernous sinus after removal of its medial wall.
1: pituitary, 2: optic nerve, 3: ophthalmic artery, 4: optico-carotid recess, 5: internal
carotid artery, 6: ophthalmic nerve, 7: abducent nerve, * superior orbital notch
Endoscopic anatomy
35
Fig. 3-23. View into the cavernous sinus from below.
1: pituitary, 2: planum sphenoidale, 3: dura of optic nerve canal , 4: internal carotid artery
Fig. 3-24. 1: pituitary, 2: planum sphenoidale, 3: optic nerve (dura of the optic nerve canal opened),
4: ophthalmic artery, 5: internal carotid artery
M. Tschabitscher and R.
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Galzio
Fig. 3-25. 1: pituitary, 2: pituitary stalk, 3: optic chiasm, 4: optic nerve, 5: ophthalmic artery, 6:
internal carotid artery, 7: olfactory nerve, 8: rectal gyrus
Fig. 3-26. 1: pituitary, 2: optic nerve, 3: ophthalmic artery, 4: ocu lomotor nerve, 5: trochlear nerve,
6: abducent nerve, 7: ophthalmic nerve
The cavernous sinus can be accessed transnasally either through its medial wall
(= lateral wall of the sphenoid sinus) (Figs. 3-21, 3-22) or through its floor from anterior
and inferior (Figs. 3-23 - 3-26).
Endoscopic anatomy
3.7
37
Retrosellar - retroclival region
Entry into the posterior cranial fossa through the posterior wall of the sphenoid sinus is
most easily gained, when the sinus is of the retrosellar type. After negotiating the mucosa
Fig. 3-27. Removal of clivus brings into view the venous plexus between the periosteum and the
dura mater.
1: pituitary, 2: optic nerve, 3: ophthalmic artery, 4: internal carotid artery, 5:
intracanalicular internal carotid artery, 6: clivus removed and venous plexus
Fig. 3-28. 1: olfactory nerve, 2: gyrus rectus, 3: anterior cerebral artery, 4: optic chiasm, 5: pituitary,
6: intra-sinusal internal carotid, 7: intracanalicular internal carotid, 8: basilar artery
M. Tschabitscher and R. J. Galzio
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Fig. 3-29. 1: pituitary, 2: mamillary body, 3: oculomotor nerve, 4: posterior communicating artery,
5: posterior cerebral artery, 6: superior cerebellar artery, 7: basilar tip, 8: anterior choroidal
artery
and the bone, which is sometimes no more than 1 to 2 mm thick, the very dense venous
plexus between the periosteum and the dura is reached . During dissection particular
attention should be paid to the 6th cranial nerve. Depending on the optical system used,
the basilar artery in the basal cistern and its branches as well as the neighboring cranial
nerves are well seen along almost their entire course (Figs. 3-27 -3-29).
References
1. Clara M (1966) Entwicklungsgeschichte des Menschen, 6.Aufl. VEB Georg Thieme, Leipzig
2. Dandy WE (1945) Surgery of the Brain. In: Lewis' practice of surgery, vol 12. Maryland W . F.
Prior Company Inc., Hagerstown, p 557
3. Ferner H (1960) Die Hypophysenzisterne des Menschen und ihre Beziehung zum Entstehungsmechanismus der sekundaren Sellaerweiterung. Z Anat Entw Gesch 121: 407 -416
4. Giordano D (1894) Manuale di medicina operativa. In: Duplay e Reclus (eds) Trattato di
Chirurgia. UTET, Torino, pp 100-103. (quoted from Guiffre R. Neurosurgery 42: 909-912,
1998)
5. Halstead AE (1910) The operative treatment of tumors of the hypophysis. Surg Gynec & Obstet
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115: 175-201
Endoscopic anatomy
39
11. Perneczky A, Tschabitscher M, Resch KDM (1993) Endoscopic anatomy for neurosurgery.
Georg Thieme, Stuttgart New York
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243-279
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767 -817
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pneumatischen Anhange. Bd 1, 2. Auf!. Wilhelm Braumuller, Wi en Leipzig