Internet Outline of

Neurosurgery

E. R. Flotte MD, 2009

Please send comments and corrections to admin@flotte2.com

www.outlineofneurosurgery.com

Cranial Procedures

General References

· Salcman M et al: Kempe’s Operative Neurosurgery, 2^nd ed.

Surgical Anatomy

External Landmarks

· Motor Strip: 4-5cm behind coronal suture, 45° to midpoint between orbit and EAC

· Foramen of Monroe ≈ Coronal suture

· 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 ICA.

Posterior Fossa

· Rhoton’s rule of 3:

1. Superior: Meckle’s cave, CN5, SCA, tentorial surface.

2. Middle: IAC, CN7/8, AICA, petrosal surface.

3. Inferior: 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

· Spinal Retractors

o McCulloch (Invuity)

o Caspar (Aesculap)

o Versatrac (Cardinal/V. Mueller); Shadowline (Cardinal/V. Mueller)

o MetRx (Medtronic Sofamor Danek) tubular retractor

· Cranial Self-retaining Retractors:

o Budde Halo (Integra)

o Greenberg (Codman)

o MetRx (Medtronic Sofamor Danek) tubular retractor has been used in craniotomies (Fahim DK JN:P2/09)

· Handheld Retractors: Army-Navy, Cushing Subtemporal

· “Fish-hook” retractors

· Aneurysm Clips: Sugita (Mizuho), Yasargil (Aesculap

), Spetzler (Cardinal/V. Mueller)

· Controlled Suction: Fukushima (Integra), Sundt (Scanlan)

· 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

Surgical Irrigation

· Saline with antibiotics (e.g. Bacitracin) typically used

Neuroendoscope

· See Neuroendoscopy

· Neuroendoscopic systems: Medtronic, Storz

o May be disposable or reusable

o Scopes may be rigid or flexible

o Various angles are available: e.g. 0°, 30°, 70°, 120°

Stereotactic Systems

Ultrasonic Aspirator

· Used for controlled tumor/tissue removal

· Systems: CUSA (Radionics/Integra)

Laser

· NdYAG (not CO2) in bloody tumors; focused beam for gross removal, defocused for margins

Cortical Stimulation

· Ojemann Bipolar Cortical Stimulator (Integra)

Hemostatic Agents

· Bone Wax

· Gelfoam (Upjohn/Pfizer): porcine gelatin sponge, often used with topical thrombin.

· Surgicel (J&J) oxidized cellulose (sheet or fibrillar)

· Avitene (Davol/Bard) microfibrillar collagen

· Surgiflo (J&J), Floseal (Baxter): Human Thrombin/Bovine Gelatin Matrix (i.e. morcelized gelfoam) mixture

· Topical Thrombin

· Dilute hydrogen peroxide

Dural Sealants

· Fibrin Glue: mixture of fibrinogen and thrombin. Must be heated to 37° before use.

o Brand names: Tisseal (Baxter), Evicel (J&J)

· DuraSeal (Confluent Surgical) For cranial use - only FDA approved cranial dural sealant. Liquefies in 4-8 weeks. May swell up to 50% - avoid near enclosed bony structures (i.e. neural foramen). Blue colorant. Spinal version (Xact) under investigation in U.S. – available in Europe.

Dural Grafts

· Autologous: pericranium, fascia lata

· Cadaveric fascia

· Bovine pericardium: Dura-Guard

· Collagen matrix: DuraGen (Integra) Onlay (DuraGen Plus)

Cranial Plating

· Resorbable plating

· Manufacturers: Synthes, KLS-Martin, Leibinger, Stryker

· Cranioplasty materials

Skin Closure

· Cyanoacrylate glue: DermaBond, Ethicon

· Antibiotic impregnated suture: Vicryl Plus (Ethicon)

o Antimicrobial-impregnated suture in shunt surgery: Rozzelle CR JN:P8/08

Procedures

Cranioplasty

· 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 - Stryker

): biocompatible and osteoconductive, inadequate setting, settling, brittle, less satisfactory for large defects

o Premade alloplastic implants – may be customized (polyethylene - Porex)

o Titanium mesh

· Bone flap: implanted in patient’s abdomen or stored in freezer. Autoclaving not recommended due to bone protein denaturation.

o 50% bone resorption in children when replaced; no correlation with time to re-implantation (JN:P2/04)

Positions

· Supine

· Lateral

o Park-Bench

o Modified Park-Bench: see Lanzino G ON10/05

· Prone: ↑ ETCO2 – make sure ET tube is not kinked

· Sitting

o Risks: Air embolism, tension pneumocephalus, remote ICH, spinal cord injury/infarction.

§ Place precordial Doppler, CVL

§ Consider preop c-spine MRI to rule out cervical stenosis (canal should be >12mm)

o Avoid with patent foramen ovale, cardiovascular disease, severe hypertension, cervical stenosis.

Anterior Approaches

Transoral

· Clivus, craniocervical junction (Dorsum sellae to C2-3). Extradural lesions primarily.

Transsphenoidal

· Adjuncts: Stereotactic Navigation, Flouroscopy

· Position: Patient supine; head on doughnut, horshoe, or Mayfield; forehead parallel to floor.

o Prep abdomen for fat graft.

o Use intranasal cocaine or Afrin for hemostasis during prep.

· Approaches:

o 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.

o Sublabial

o Transnasal (submucosal)

· Complications:

o CSF leak: Consider fat packing, fibrin glue, duraseal, etc. Consider placing lumbar drain in the O.R.

· Sella floor may be reconstructed (bone fragments, absorbable plates)

o Carotid tear: Hemorrhage controlled with harvested fascia. Immediate postop angio to rule out pseudo-aneurysm (repeat after 7-10 days if negative).

· Microdoppler may be used to locate carotid (Dusick JR N4/07 - VIDEO)

· Reviews: Ciric I N7/02 (Operative Nuances), Jane JA N8/02 (Operative Nuances), Fatemi N ON10/08 (Operative Nuances)

· Videos: Jane JA N8/02, Fatemi ON10/08

Endoscopic transsphenoidal approach

· Classification of endonasal endoscopic approaches: See Schwartz TH N5/08 Table 2

· “Two-nostril, three-handed” technique used (e.g. Pittsburgh)

· Reviews: Cappabianca P N5/04,Cappabianca P N10/04 (Operative Nuances), Dehdashti AR N5/08

· Videos: Cappabianca P N10/04

Extended transsphenoidal approaches

· Terminology varies

· Presellar: planum sphenoidale removed

· Transsellar-Transdiaphragmatic: Gland incised, diaphragm opened to resect suprasellar mass.

· Intra-cavernous sinus: consider preop balloon occlusion test, carotid exposure for proximal control.

· Sellar-Clival

· Anterior clivectomy: Al-Mefty O JN11/08

· Reviews: deDivitiis E N9/02, Couldwell WT N9/04, de Divitiis E ON11/07 (Operative Nuances), de Divitiis E NF12/08

· Case Reports: Dedashti AR N4/09

o Endoscopic endonasal odontoidectomy – Kassam AB ON7/05 - VIDEO,

· Videos: de Divitiis E ON11/07, Dehdashti AR N4/09

Bifrontal

· Bicoronal incision.

· Pericranium saved for dural graft.

· Burrholes at keyholes, straddling (or over) sinus posteriorly (± anteriorly).

o Consider using stereotaxy to avoid or include frontal sinuses as needed

· Superior sagittal sinus ligated as anteriorly as possible and dura opened

· Frontal Sinus Cranialization (obliteration/exenteration) (if needed): Remove posterior wall. Mucosa removed (exenterated) and packed into frontonasal duct. Remaining walls of sinus drilled to remove mucosal crypts (preventing mucocoele formation). Frontonasal duct then packed with muscle or fascia. Periosteal flap is then placed over sinus and floor.

o Others say enfold mucosa and cover with gelfoam (Kempes)

o Bicoronal incision. Preserve pericranium.

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

· See Hitomatsu T (Rhoton) N6/00 (Unilateral upper and lower subtotal maxillectomy)

Anterolateral Approaches

Pterional

· Positioning: Supine.

o 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

o Sphenoid Ridge (including “spine”) drilled/removed to orbitomeningeal a./superior orbital fissure

· Dural opening: C-shape

· Frontal lobe retracted off sphenoid ridge to expose optic n.

· Corridors to brainstem:

o Opticocarotid: less favorable due to perforators

o Carotidoculomotor

· Intradural Modifications:

o Splitting sylvian fissure: Yasargil avoids using self-retaining retractors on Sylvian fissure (N12/03 p1305).

· Veins usually 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 ICA+ mobilizing CN3 (by opening cavernous sinus roof) + posterior clinoidectomy.

· Mobilizing CN3 felt to be unnecessary by some. (Youssef AS N5/04)

Orbitozygomatic

· A.k.a. cranioorbitalzygomatic (COZ)

· Positioning, incision as for pterional. Save periosteum in case frontal sinus entered – look for sinuses on CT.

· Two-piece: Frontotemporal crani, then cuts at root of zygoma, malar eminence, orbit (IOF to lateral to supraorbital notch, at least 3cm deep to avoid exopthalamos).

· Alternative: One-piece.

· Modifications: taking just orbit or zygoma (Lemole GM JN11/03). If just taking zygoma leave it attached to the temporalis.

· Open mouth modification for lesions extending into infratemporal fossa (N5/04)

· Reviews: van Furth WR ON2/06 (Operative Nuances), Seckin H NF12/08

· Videos: van Furth WR ON2/06

Middle Fossa

Subtemporal

· For lesions in middle fossa or posterior cavernous sinus or intracanalicullar acoustic neuromas

· Limits: inferior to 1cm below posterior clinoid (to IAC with anterior petrosectomy)

· Positioning: Oblique, head 90º lateral.

· Skin Incision: Question-mark or Reverse U-shaped (anterior to tragus to mastoid tip)

· Craniotomy: Wide temporal (5cm) craniotomy centered anterior to EAC ± zygomatic osteotomy.

· Dura elevated (posterior to anterior avoids stretching GSPN). Middle meningeal a. divided & foramen spinosum packed.

· Temporal lobe elevation limited by vein of Labbe. Some recommend preoperative MRV. Periodically release retraction.

· Anatomy:

· IAC located along line bisecting the axes of the GSPN and arcuate eminence.

· Cochlea is at junction of posterior genu of carotid, geniculate ganglion, and medial IAC (premeatal triangle).

· Injury to GSPN causes decreased lacrimation

· Acoustic Neuroma/IAC:

· Prepare for abdominal fat graft.

· Unroof facial n. from IAC to geniculate ganglion

· Lateral-to-medial: GSPN followed to geniculate ganglion then facial n.

· Medial-to-lateral: from IAC

· Dura opened medial-to-lateral

· Identify facial n. Resect tumor. Reapproximate dura. Pack bony defect with fat.

Preauricular Subtemporal Infratemporal:

As above, plus:

· Facial n. dissected from stylomastoid foramen to parotid.

· Craniotomy: Wide temporal craniotomy ± zygomatic osteotomy (reflected inferior with masseter). Temporalis detached from coronoid process of mandible and reflected superiorly. Head of mandible and TMJ may be removed.

· TMJ-preserving approach (Vilela MD N7/04)

Transtemporal-Transchoroidal

Extradural Temporopolar

· Extradural approach to cavernous sinus and Clivus

· Generally performed after orbitozygomatic craniotomy. Extradural retraction of brain.

· Reviews: Zada G NF12/08

Combined Middle-Posterior Fossa

Anterior Transpetrosal (Petrosectomy)

· For lesions in posterior middle fossa/ superior posterior fossa. Exposes Basilar, AICA, CN5-8.

· Extension of subtemporal or pterional approaches.

· Petrous apex drilled between ICA, cochlea, and IAC, under V3.

o Kawase’s quadrilateral: petrous ridge and V3 medial, GSPN lateral, arcuate eminence posterior

· Dura opened superiorly and inferiorly parallel to superior petrosal sinus, which is divided at the medial aspect to preserve drainage from the petrosal v. Tentorium incised and retracted postero-superiorly with a suture. Dural window opened. Temporalis flap made and inserted into bony defect.

Combined supratentorial/infratentorial transpetrosal

· Positioning: Oblique (head lateral), ¾ prone, or sitting

· Skin Incision: hockey-stick, mastoid to in front of tragus. Temporalis and SCM dissected and reflected anteriorly.

· Craniotomy: L-shaped. Temporal/retromastoid, burrholes over transverse/sigmoid junction. Mastoidectomy.

Posterior Fossa

Transpetrosal approaches:

· Retrolabyrinthine, translabyrinthine, transcochlear

· AKA posterior transpetrosal, versus anterior transpetrosal

· Positioning: lateral, park-bench

· Incision: Curvilear. Top of pinna, 1cm behind mastoid, to mastoid tip

Retrolabyrinthine

· Exposure of sigmoid sinus, presigmoid posterior-fossa

· Drilling: EAM to supramastoid crest to back of mastoid. Spine of Henle marks mastoid antrum – when opened lateral semicircular canal is visualized. Expose middle fossa & 1cm retrosigmoid dura. Skeletonize jugular bulb & EAM. Facial n. is in fallopian canal behind EAM.

Translabyrinthine

· Hearing sacrificed. Higher rate of CSF leak.

· Labrinthectomy performed, expose Bill’s bar. Inferior to IAC cochlear aqueduct opened, CSF egress seen. Stimulate through dura at 0.1-0.3 mA to rule out ectopic facial n. before opening dura. Dura opened in “T” or “H”. Preserve arachnoid. Open arachnoid inferior to cranial n. for CSF release from cisterna magna. Debulk tumor after stimulating capsule. On brainstem CN7 is inferomedial to CN8. CN8 divided. Tumor separated from CN7 medial to lateral. OK to leave capsule on CN7. Muscle packed in middle ear to avoid CSF leak through Eustachian tube. (Diaz Day J N2/04)

· Reviews: Diaz Day J N2/04 (Operative Nuances)

· Videos: Diaz Day J N2/04

Transcochlear

· Hearing sacrificed.

· Exposure & transposition of CN7, drilling of EAC, middle ear, & cochlea.

Suboccipital

· Prone

· Incision usually midline linear

· Consider placing Burrholes over midline keel

· Dural opening often V/U-shaped

Retrosigmoid

· Consider bronchoscopy to evaluate for preop vocal cord paresis

· Consider BAERS, facial n. EMG, handheld nerve stimulator Consider lumbar drain.

· Positioning: lateral, park bench (also oblique/head lateral for obese pts). Head rotated to floor and flexed.

· Skin: (curvi)linear or hockey-stick. 2cm behind mastoid.

· Craniotomy vs craniectomy: Can perform craniectomy, or outline sinuses and then craniotomy, or craniotomy from asterion.

· Wax mastoid air cells to prevent CSF leak

· Can repair sinus with 5-0 prolene, or simply pack with gelfoam, surgical, duraseal, etc.

· Dural opening: X or Y-shaped. Open cisterna magna for CSF egress.

· Cerebellar retraction should be perpendicular to CN8 to avoid deafness.

· Main trunk of Superior Petrosal Vein (SPV) should be preserved. CN5 usually medial to SPV. CN7 whiter.

· MVD approaches: CN5: infratentorial. CN7 (HFS): infrafloccular. CN9: transcondylar. See Hitotsumatsu T N12/03

Far-Lateral

· Extension of retrosigmoid approach.

· Lateral, park-bench. Vertex tilted slightly towards floor, chin rotated 10º to floor. See Lanzino G ON10/05

· Horseshoe incision: midline, C3/4 to superior nuchal line, lateral to mastoid tip. Muscles reflected with scalp.

o Alternative: C-shaped, 1cm above ear to 5cm below mastoid tip.

· Muscles: trapezius medial, semispinalis superior, splenius inferior, SCM lateral. Incise at superior nuchal line – leave cuff for reattachment

o Suboccipital triangle: Rectus capitis posterior major medial, Superior & Inferior Obliques lateral.

o Midline fascia incised to expose occiput, C1/2. Muscles reflected laterally

· Remove lateral arch C1 to sulcus arteriosus.

· Some skeletonize and transpose vertebral a. from transverse foramen, although Spetzlet et al say it is unnecessary unless extradural control of the VA is needed (Lanzino G ON10/05)

· Remove lateral rim of foramen magnum, up to posterior 1/3 occipital condyle (depending upon lesion). Dura opened in C-shape.

o Resection of >50% of the condyle requires occipital-cervical fusion (Vishteh AG JN 1999)

o Hypoglossal canal lies at middle 1/3 of condyle

· Modifications: mobilization of vertebral artery, removal of jugular tubercle.

o Transcondylar, Supracondylar, Paracondylar (Wen HT JN97, Kawashima N9/03).

· Reviews: Lanzino G ON10/05 (Operative Nuances)

· Videos: Lanzino G ON10/05

Extreme lateral

· Incision 6cm below mastoid tip, along anterior border of SCM to EAM & curve posteriorly. SCM divided, leaving cuff.

· Identify CN11 (3.5cm below mastoid tip), plane between IJ & SCM.

· Splenius capitis, semispinalis capitis, & longissimus capitis reflected posteriorly exposes suboccipital triangle mm. which are reflected. Posterior belly of digastric protects facial n.

· Deep to SCM, behind IJ, along VA

Lateral Transcervical

· Exposes carotid sheath, CN7, 9-12, vertebral a.

· Positioning: Lateral, head 90º, vertex slightly down.

· Incision: S-shaped from above mastoid to anterior to SCM. Skin elevated from SCM (greater auricular n. seen). SCM & splenius capitis dissected off mastoid and reflected posteriorly, CN11 seen.

Lobectomies

Frontal Lobectomy

· Positioning: supine, head flexed

· Craniotomy: triangular, behind coronal suture, above frontal sinus

· Dural opening: triangular

· Extent: 7-8cm, @ sphenoid wing

· Leave olfactory tract in place

Temporal Lobectomy

· Extent: 4.5cm dominant, 7cm non-dominant

· Consider awake craniotomy

· Perform subpial dissection medially & superiorly

· Beware of anterior choroidal a. looping into choroids plexus – avoid coagulating plexus

Occipital Lobectomy

· Positioning: ¾ prone

· Craniotomy: triangular; 1cm away from SSS, TS

· Dural opening: T

· Extent: dominant 3.5cm; nondominant 7cm

· PCA in calcarine fissure coagulated

Corpus Callosotomy

· Therapeutic for epilepsy, or for approach to lateral or 3^rd ventricles

· Side Effects: delerium, mutism, apathy, memory problems in 1/3 (usually resolves within 1wk)

· 2-2.5cm oval callosotomy. Coagulate all ependymal vessels

· Preop angio, MRV to look for bridging veins

· Fenestrate septum >1cm² highest portion, post to foramen

Approaches by Lesion Location

Approaches to Lateral or 3^rd Ventricles

Superior Approaches to lateral/3^rd ventricles

· Consider fenestration of septum pellucidum for biventricular hydrocephalus (e.g. colloid cysts)

· Fornix damage causes memory problems

· Reviews: Yasargil MG N6/08S

· Videos: Yasargil MG N6/08S

1. Transcortical

· Better in the face of significant hydrocephalus

· May have a higher risk of seizures, behavioral disorders

· Reviews: Ellenbogen RG NF6/01

2. Transcallosal/Interhemispheric

· Preferred in the absence of hydrocephalus

· ACAs at risk. Possible SMA syndrome.

Callosotomies

Anterior Transcallosal

· Positioning: supine, flex head

· Skin incision: linear/curvilinear/bicoronal or U-shaped

· Craniotomy: rectangle/trapezoid, at least 2/3 anterior to coronal suture, SSS exposed

· Can sacrifice bridging veins anterior to the coronal suture (Apuzzo)

· Place retractors on falx & cortex. Relax retractors as possible.

· Watch for ACAs. Corpus callosum is pure white (vs cingulate gyrus).

· Cotton balls placed over corpus callosum for retraction.

Posterior Transcallosal

· Positioning: lateral side of approach down or prone

· Craniotomy: triangular/trapezoid, SSS exposed

· Expose corpus callosum – splenium to 6cm anterior

· Callosotomy: 3cm, in midline between ICVs; leave 2-3cm of splenium posteriorly

3. Endoscopic Approach to Lateral/3^rd ventricles

· Burrhole placement determined by desired trajectory, usually 1cm anterior to coronal suture and 3-6cm off midline

· Reviews: Charalampaki P ON10/05, Cappabianca P N2/08S, Souweidane MM ON6/08

· Videos: Cappabianca PN2/08S

Approaches to 3^rd ventricle thru lateral ventricles

A. Transforaminal

· 3^rd ventricle accessed through Foramen of Monro

· Do not use if mass is significantly larger than foramen

· Inspect 3^rd ventricle with mirrors or endoscope

· Sectioning fornix may cause severe neuropsychological impairment

· Some incise anterior nucleus of thalamus – risk of bleeding from internal cerebral vein

B. Transchoroidal-Transveluminterpositum

· Better approach if internal cerebral veins (ICVs) are not clearly separated

· Suprachoroidal: Open taenia fornicis medially, between choroid & fornix

· Subchoroidal: tenia thalami between choroid and thalamus. May have higher risk to thalamostriate v. & bridging vv.

§ Thalamostriate v. injury causes hemiparesis, somnolence, mutism.

· Transchoroidal

· Reviews: Kasowski HJ ON10/05 (Operative Nuances)

· Videos: Kasowsi HJ ON10/05

C. Interfornicial

· For lesions bulging upward, separating fornices

· Septum fenestrated. Fornicial raphe cut & fornices separated

· From foramen 1-2cm posterior (limited by hippocampal commisure). 2mm retractor is necessary

· Watch hippocampal fissure, internal cerebral veins, medial posterior choroidal arteries

Inferior approach to 3^rd ventricle

Trans-Lamina Terminalis

· Bifrontal craniotomy, interhemispheric approach (can also use pterional, transsphenoidal, COZ)

· Lamina terminalis fenestrated

· Reviews: Dehdashti AR ON4/05 (Operative Nuances)

· Videos: Dehdashti AR ON4/05

Pineal Region

· Send CSF for cytology, aFP, bHCG, PLAP (for germ cell tumors)

· Some recommend radiation based on CSF (if positive for germ cell markers) and imaging without tissue diagnosis.

· Some prefer stereotactic biopsy vs open biopsy/resection.

· Consider endoscopic biopsy and concurrent third ventriculostomy

· “It may be necessary to sacrifice the midline veins to access the collicular plate or the pineal body. This sacrifice may be asymptomatic but can result in a variety of symptoms caused by edema of the nuclei of the nerves or the central pathways in the brainstem (Chaynes P N3/04)

· “It is generally believed that some of the major veins (internal cerebral vein, basal vein of Rosenthal, or vein of Galen) can be safely sacrificed” – Sekhar LN, comment on Chaynes P N3/04

Supracerebellar-Infratentorial

· Less ideal for lateral or rostral tumors

· Position: Sitting or prone

· Craniotomy: Wide suboccipital craniotomy. May extend above transverse sinus.

· Dural Incision: U-shaped, wide, base at transverse sinus

· Retractor on tentorial surface

· Supracerebellar and Precentral-cerebellar veins may be sacrificed

Occipital-Transtentorial

· Positioning: sitting, ¾ prone

· Skin incision: Linear or U-shaped - base inferior, over midline/SSS, below transverse sinus

· Retract tentorium rather than falx

· No veins run from occipital lobe to SSS

· Incise tentorium posterior to anterior, 1cm off midline; may require liga-clips;

· Retract tentorium laterally w/suture

· Also: combined supra-infratentorial transsinus approach

Posterior Transcallosal Interhemispheric

Insula

· Lenticulostriate artery position: Moshel YA JN11/08

· Case Series: Simon M JN4/09, Duffau H JN4/09

· Reviews: Hentschel SJ N7/05 (Operative Nuances)

· Videos: Hentschel SJ N7/05, CNS University of Neurosurgery

Thalamus

· Approaches: transcortical, transinsular, interhemispheric, infratentorial

o Transcortical: frontal, parietal, occipital, or temporal routes used

· 3-5% mortality, 10% permanent morbidity (Albright AL JN:P5/04)

· Reviews: Puget S JN:P5/07 (pediatric), Albright AL JN:P5/04 (pediatric)

·

Optic Nerve/Orbit

· Optic nerve lesion differential diagnosis

· Lesions posterior to the globe are usually approached intracranially. Lesions lateral, inferior or superior to the globe are generally treated by an ophthalmologist transorbitally.

1. Transorbital

2. Extraorbital

A. Inferior Orbital: transmaxillary

B. Transfrontal/transcranial

§ Approached via pterional craniotomy

§ Dura opened in C-shaped fashion as for standard pterional craniotomy.

§ Dura incised (intradurally) over orbit and reflected medially.

§ Orbital roof (floor of anterior fossa) removed

§ Open orbital fascia along axis of optic nerve

§ If necessary open optic canal and annulus of Zinn

§ Consider bony decompression versus extirpation.

§ If extirpating nerve then sacrifice ophthalmic artery

§ Dissect fat and muscle to expose tumor (watch levator palpebra m. and supraorbital n.)

§ May fill orbital defect with fat. Close annulus/fascia if possible. Use titanium mesh for bony defect.

· Reviews: Bejjani GK NF5/01

Cavernous Sinus

· Reviews: Neurosurgical Focus 12/08

Perimesencephalic Cisterns

· Transsylvian pretemporal, subtemporal, occipital transtentorial, supracerebellar infratentorial, transtemporal transchoroidal. (N6/04)

Clivus

· Transbasal

· Transsphenoidal (Expanded Endoscopic Endonasal)

· Subtemporal

· Transpetrosal

· Far Lateral

· Reviews: Carrabba G NF12/08

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

· See Henn, Spetzler, Clin NSurg 49

Needle Brain Biopsy

· May be frameless or frame-based stereotactic-guided

o No difference in safety or yield between frameless or frame-based (Woodworth GF JN2/06)

· Targeting may be augmented by MRSpect, Perfusion MRI

· Brainstem: May be done transfrontal or transcerebellar (Sanai N N9/08)

o Transfrontal approach used for medial midbrain/pontine lesions

§ Contralateral transfrontal approach has been used for lateral lesions (Amundson EW JN3/05)

o Transcerebellar approach used for lesions at or below middle cerebellar peduncle

§ Case Series: Guthrie BL JN4/89 (BRW frame)

o Transtentorial approach rarely used

Revised 6/1/09

Text Copyright 2009

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