Outline of
Neurosurgery
E. R. Flotte, 2008
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and corrections to admin@flotte2.com
Procedures
Surgical Anatomy
External Landmarks
·
Motor Strip: 4-5cm behind coronal suture, 45° to midpoint
between orbit and EAC
·
Foramen of
·
Asterion = transverse-sigmoid junction
o
Nasion, glabella, bregma, lambda, inion, opisthion, asterion
Cerebral cortex
·
Supplementary Motor Area
Syndrome: Contralateral akinesia
with mutism (when on dominant side – very rarely on non-dominant side) after
damage to SMA. SMA: area 8 - mesial posterior frontal
lobe, role in initating speech and motor function.
Recovery of speech occurs in 4-12 days and motor by 2-6mos. May not be evident
during awake crani (may appear postop). Stimulation requires high voltage to
elicit 
responses (speech and motor arrest, complex postural movements, sensory
& autonomic phenomenon.)
·
Corpus Callosum:
o
Anterior: Slow ideation
o
Middle: SMA syndrome
o
Posterior: Sensorimotor deficits.
o
Hemispheric Disconnection
Syndrome
Middle
fossa triangles:
·
Glasscock’s: Foramen spinosum to arcuate eminence to
GSPN. Exposes petrous
Posterior
Fossa
·
Rhoton’s rule of 3: 1) Meckle’s cave, CN5, SCA, tentorial surface. 2) IAC, CN7/8, AICA, petrosal
surface. 3) Jugular foramen, CN9/10/11, PICA, subocciptal
surface.
·
Landmarks:
Transverse-Sigmoid junction at asterion. Mastoid
emissary vein/foramen at posterior edge of sigmoid sinus. Posterior end of incisura mastoidea is at level of
IAC.
Veins
·
Labbe: enters
at transverse-sigmoid junction.
Equipment
Surgical Drills
·
Pneumatic:
Midas Rex (Medtronic), Anspach
·
Electric:
Midas Rex, Anspach, NSK
Operating Microscopes
·
Manufacturers:
Zeiss, Leica
Neurosurgical Instruments
·
Lumbar
Self-retaining Retractors
·
Cranial
Self-retaining Retractors: Budde Halo, Greenberg
·
Handheld
Retractors: Army-Navy, Cushing Subtemporal
·
“Fish-hook”
retractors
·
Aneurysm
Clips: Sugita (Mizuho), Yasargil (Aesculap), Spetzler
·
Controlled
Suction
·
Dissectors:
Penfield
·
Microdissectors: Rhoton
Positioning
·
“Doughnut”
·
“Horsehoe”
·
Three-Point
Pin: Mayfield Headrest (Integra)
Electrocautery
·
Bovie Cautery (Monopolar):
grounding pad placed on patients thigh
·
Bipolar
Cautery
Neuroendoscope
Ultrasonic Aspirator
·
Used
for controlled tumor/tissue removal
·
Systems:
CUSA (Radionics)
Laser
·
NdYAG (not CO2) in bloody tumors; focused beam for gross removal, defocused
for margins
Hemostatic Agents
·
Bone
Wax
·
Gelfoam:
often used with topical thrombin.
·
Oxidized
cellulose: Surgicel
(J&J)
·
Avitene
·
Surgiflo, Floseal
·
Topical
Thrombin
Dural Grafts
·
Autologous:
pericranium, fascia lata
·
Cadaveric fascia
·
Bovine
pericardium: Dura-Guard
·
Collagen
matrix: DuraGen (Integra)
Onlay (DuraGen Plus)
·
Resorbable plating
·
Manufacturers:
Synthes, KLS-Martin, Leibinger
Shunt Hardware
·
Valve
types
o
Differential
Pressure: Holter (aka Spitz-Holter - obsolete), Heyer-Schulte
(Integra), Pudenz
(Integra), PS Medical (Medtronic),
§
Drain
at preset minimum/maximum pressures – available in low, medium, high
o
Flow-limiting:
Orbis Sigma (Integra),
Delta (with anti-siphon device) (Medtronic)
o
Programmable:
Sophy & Polaris (Sophysa), Codman Hakim, Strata (Medtronic), proGAV (Aesculap-Miethke)
·
Antibiotic-Impregnated
catheters
o
Manufacturers:
Bactiseal (Codman)
·
Anti-siphon
Devices
o
Manufacturers:
Codman
Procedures
·
Materials:
o
Autologous bone (cranium, rib, ilium):
lower infection risk than artificial material, may resorb
o
Methylmethacrylate “bone
cement”: high-tensile strength, infection 23%, fractures occur
o
Hydroxyapatite or
calcium phosphate (Bonesource): biocompatible and osteoconductive, inadequate setting, settling, brittle,
less satisfactory for large defects
o
Premade alloplastic implants (polyethylene - Porex)
o
Titanium mesh
·
Bone flap: implanted in patient’s abdomen or stored
in freezer. Autoclaving not recommended due to bone protein denaturation. 50%
bone resorption in children when replaced; no correlation with time to re-implantation
(JN:P2/04)
Locations
3rd Ventricle
·
No hydocephalus – transcallosal
·
Inferior – pterional,
subfrontal, subtemporal, transphenoidal, COZ
Basilar artery access:
·
Orbitozygomatic: Top 2/5, SCA, CN3/4, midbrain
·
Transcochlear: Middle 1/5, AICA, pons,
CN5-8
·
Far lateral:
Lower 2/5, PICA, CN9-12
·
(Henn, Spetzler, Clin NSurg 49)
Perimesencephalic Cisterns
·
Transsylvian pretemporal, subtemporal,
occipital transtentorial, supracerebellar
infratentorial, transtemporal
transchoroidal. See N6/04
Cavernous Sinus
·
Some
recommend resecting tumors (meningiomas)
from lateral compartment only, treating the residual with SRS. If tumor touches
but doesn’t encase ICA (C4) it can be totally resected.
Excision of medial cavernous sinus lesion carries a very high rate of cranial
nerve morbidity. (N6/04)
Positions
·
Sitting
o
Risks: Air embolism,
tension pneumocephalus, remote ICH, spinal cord
injury/infaction.
§
Place
precordial Doppler, CVL
o
Avoid
with patent foramen ovale, cardiovascular disease,
severe hypertension, cervical stenosis.
§
Consider
preop cspine MRI to rule out
cervical stenosis (canal should be >12mm)
Anterior Approaches
Transoral
·
Clivus, craniocervical junction (Dorsum sellae to C2-3). Extradural
lesions primarily (Intradural used for basilar
aneurysms.)
·
Supine,
head extended. Retractor has groove for ET tube. Posterior pharyngeal wall
incised, ± soft palate (lateral to uvula), ± hard palate. Use Dingmann mouth gag. (N1/04)
Transphenoidal
·
Patient
supine, on doughnut, forehead parallel to floor. Prep abdomen for fat graft.
Use intranasal cocaine for hemostasis.
·
Endonasal: Middle concha followed to
sphenoid ostia, nasal mucosa reflected
medial/inferiorly, sphenoid sinus opened thru ostia,
sphenoid mucosa removed, posterior
sphenoid/anterior sella wall opened (with chisel if
necessary). Dura opened in cruciate
fashion. Sella explored with ringed curettes.
·
Alternative:
Sublabial, transnasal (submucosal)
·
CSF
leak: Consider fat packing, fibrin glue, etc. Consider placing lumbar drain in
the O.R.
·
Carotid
tear: Hemorrhage controlled wth harvested fascia.
Immediate postop angio to rule out pseudo-aneurysm (repeat after 7-10 days if
negative).
·
Endoscopic
approach advocated by P. Cappabianca
·
Extended transphenoidal:
o
Presellar: planum sphenoidale removed
o
Transsellar-Transdiaphragmatic: Gland incised, diaphragm opened to
resect suprasellar mass.
o
Intra-cavernous sinus: consider preop
ballon occlusion test, carotid exposure for proximal
control.
o
Sellar-Clival
o
See N9/04
Bifrontal
·
Bicoronal incision. Pericranium saved for dural graft. Burrholes at
keyholes, straddling sinus posteriorly (± anteriorly).
Transbasal
·
Extradural access only.
·
Bifrontal craniotomy. Olfactory nn. divided, frontal sinuses cranialized,
ethmoid sinuses removed, sphenoid sinus unroofed,
optic n. unroofed, clivus drilled (sella to foramen magnum).
·
Extended
transbasal: “bandeau” included.
Transmaxillary
Anterolateral
Approaches
Pterional
·
Positioning:
Supine. Head Rotation: ICA/basilar 20º, MCA 45º, Acom
60º; Flex chin to contralateral shoulder; “Extend” vertex inferiorly so malar eminence is highest point.
·
Skin
incision: Coronal
·
May
reflect temporalis with skin (for frontal exposure),
or with subfascial dissection (for subtemporal
exposure).
o
Zygomatic Arch may be removed or detached and retracted with the temporalis muscle.
·
Craniotomy:
Frontotemporal. Keyhole exposes dura
& periorbita
·
Sphenoid
Ridge (including “spine”) drilled to orbitomeningeal
a./superior orbital fissure
·
Dural
opening: C-shape
·
Frontal
lobe retracted off sphenoid ridge to expose optic n.
·
Corridors:
o
Opticocarotid: less favorable due to perforators
o
Carotidoculomotor
·
Intradural Modifications:
o
Splitting
sylvian fissure:Yasargil
avoids using self-retaining retractors on Sylvian fissure. Veins adherent to
temporal lobe – dissect between veins and frontal lobe.
o
Anterior
clinoidectomy: Intradural
or extradural.
o
Unroofing of optic nerve: When opening optic n. sheath watch for trochlear which crosses over lateral-to-medial
o
Posterior
clinoidectomy
o
“Transcavernous”
approach to basilar artery: Anterior clinoidectomy +
mobilizing
