Craniotomy principles

SCALP FLAPS & CRANIOTOMY PRINCIPLES Scalp flaps- Historical perspectiveNeolithic period in 2000 B.C19th century- trephines1889 Wagner first osteoplastic bone flapGigli saw for craniotomy- Obalinski in 1897Electric and gas powered high speed drills

Anatomic and neurovascular considerations5 layers of scalp: Skin Connective tissue Aponeurosis Loose areolar tissue PericraniumLand marksNasionBregmaLambdaInionPterion: Middle meningeal arteryAsterion: Transverse sigmoid junction

Fronto- temporal branch: anterior branch middle branch posterior branchMiddle division: 1 cm anterior to superficial temporal artery, subgaleal pad of fat Dissect between superficial and deep layers of superficial temporalis fascia

Blood supplySuperficial temporal arteryOccipital arteryPosterior auricular arterySupra orbital and trochlear vesselsPrinciples of craniotomyPreoperative review of patientPreparation of scalpPositioning of patient on the tableScalp toiletMarking of the incisionDraping Planning Position of lesionPosition of important structuresContingency plan for enlarging incisionObtain adequate closure

Principles General principles:Surgical exposure of the lesionNeuro vascular supplyCosmetic effectTypes: Random patternBased on named vessel Length not > 1.5 times baseIntegrity of major vascular flap to be maintainedIncision in hair containing regionNo crossed incisions

Taylor Haughton Lines

Principles Skin incised with galeaPressure over the scalpPeriosteum raised with scalp or separatelyRaneys clips, bipolar, Haemostatic artery forcepsAdequate retractionInner surface protected with moistened gauzeRoller gauzeDissect in interfascial fat which is encountered within 4 cm of orbital rim

Types of craniotomiesFlap craniotomyTrephine craniotomyFlap craniotomy: Osteoplastic Free bone flapBone flapsMost direct access to targetFor cerebral convexity directly centered over the lesionNumber of burr holes variesSeparation of underlying duraBeveling effectBone flapsIf dura is lacerated during cutting, saw should be turned off and removed backwards via entrance hole

Air cells opened: Remove the mucosaPack with betadine soaked gelfoamPack with bone waxCover it up with vascularized tissue Proposed bony cuts over venous sinuses should be done last- vascularity adherenceCut sinus can be sewn/ tamponadeBony bleeds stopped with bone waxPenfields dissector to separate duraEpidural tacking sutures to control epidural bleeding before opening duraOthers dont in order to protect cortical blood vesselsTailor to avoid dural venous channels

Opening of Dura materManually palpate the duraDura opened as straight, curved or flap like incisionsFlaps based towards sinusesOpened with sharp hook and knifeIncision further opened with dural scissorsPlacement of cottonoid along the intended incisionSuitable cuff of dura around the bone for suturing laterClosure Closure in layersCheck for BP- valsalva maneuverHitch sutureWater tight but not tensionBone flap replacementSkin closed in two layers Bicoronal/ Souttar flapLarge exposures of anterior cranial fossa and sellaFronto-temporal lesions and cranial base Superior to zygomatic arch, 1 cm anterior to tragus- extends over the bregma to the corresponding site on the opposite sideReflect up to orbit rimSupraorbital/ trochlear vessels

Bicoronal/ Souttar flaps

Frontal/ Bifrontal bone flapsSuitable for frontal lobe, sub-frontal approaches to anterior skull base, and trans cortical access to ventriclesFrontal/ Bifrontal bone flapsAn extended frontal or bi-frontal craniotomies for exposure of sella, anterior cranial baseSupine with head extended for theseHoles placed on either sides of sagittal sinus and intervening bone is removed with roneguers or drill Either removed as single piece or conversion of frontal flap to bi-frontal flapCombining a frontal flap with pterional flap Frontal/ Bifrontal bone flapsGoals of surgery dictate the craniotomyBilateral orbital craniotomies may be added to minimize frontal lobe retractionDural openings for a unilateral frontal craniotomy usually consist of flap reflected towards sagittal sinusSuperior sagittal sinus may have to be ligatedFrontal flap

Exposes anterior frontal lobeBegins along coronal suture and curves anteriorly along the midline preferably ending at hair lineTemporal flapAnterior temporal lobe and sub temporal accessBased on zygomaGoes behind the earExtends anteriorly just behind the superior temporal line to the hair line

Link to video http://www.aiimsnets.org/NeurosurgeryAnimationVideoTemporalCraniotomy.htmlFronto- temporal (pterional) bone flapPopularized by Yasargil Most useful for aneurysms of anterior circulation, basilar top, also tumors of retro orbital, parasellar and subfrontal areasSupine position with head end elevated to 30 degrees and rotated by the same to opposite side

Fronto- temporal (pterional) bone flapLink to video - http://www.aiimsnets.org/NeurosurgeryAnimationVideoPterionalCraniotomy.htmlFronto-temporal flapUsed for most pterional craniotomiesCombines frontal and temporal skin flapsExtends from zygoma to 1-2 cm off the frontal midline following a curve behind the natural hair lineTemporalis muscle either dissected or reflected as a separate layerIn the later instance a cuff is left superiorly so as to suture itFronto- temporal (pterional) bone flapTemporalis muscle dissected or reflectedBone flap centered over the pterionKey burr hole, frontal burr hole, posterior burr hole, last burr hole just above the zygomaFurther bone may be removed from the inferior temporal squamaTo improve vision, drill the sphenoid ridgeDural flap based on the orbitFTOZAddition of orbito-zygomatic craniotomy will allow for a more lower and anterior approachSuited for para-sellar, inter-peduncular lesions,Basilar top aneurysm, Carotico-ophthalmic aneurysms.FTOZLink to video - http://www.aiimsnets.org/NeurosurgeryAnimationVideoFrontotemporalOrbitozygomaticFTOZApproach.html

Question mark skin flapCranial traumaExposure to whole hemisphereBased on zygomaBlood supply from superior temporal and supra orbital vesselsCurves around 3.5 cm posterior to external auditory meatusAnterior limb extends to hair lineHorse shoe skin flapExpose any portion of cerebral convexityInverted U shaped with base directed towards vascular supplySubtemporal exposure: anterior limb 1 cm anterior to the tragusFor anterior transcallosal approaches: over coronal sutureMitre skin flapMitre hats worn by bishopsOccipital lobe, posterior falx and superior tentorial surfaceInion to vertex: vertical limbUpper limb then falls over posterior parietal region towards the earBlood supply from the occipital artery34Linear and curvilinear incisionsLimited exposuresSimplicity E.g.: MLSOC RMSOC Hockey stick incisions Linear incisions for temporal lobe & subtemporal accessCP angle tumorsLateralProneThree quarters proneSitting Retromastoid suboccipital transmeatal approach

Retromastoid suboccipital transmeatal approachIncision Vertical linear ( 1 cm medial to the mastoid process )S / Lazy SInverted J -shaped/ Hockey-stickAnatomical variants-Dolichoectatic VA/Occipital arteryHypoplastic VA (20 %)- Avoid extreme flexion

Link to video - http://www.aiimsnets.org/NeurosurgeryAnimationVideoRetromastoidSuboccipitalCraniotomy.html

MLSOCLink to video - http://www.aiimsnets.org/NeurosurgeryAnimationVideoMidlineSuboccipitalCraniotomy.htmlPoppens-Suboccipital Transtentorial ApproachLink to video - http://www.aiimsnets.org/NeurosurgeryAnimationVideoPoppensSuboccipitalTranstentorialApproach.html

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