Pterional craniotomy

Most widely performed and versatile Craniotomy in Neurosurgery explained in details

1. Pterional Craniotomy Dr Fakir Mohan Sahu MBBS MS MCh SR Neurosurgery AIIMS Bhubaneswar 12/09/2020

2. Learning objective Historical perspective Anatomy Indication Positioning movements Scalp flap and craniotomy principle Steps of craniotomy Closure Complications Conclusion

3. Introduction “Workhorse” approach in cranial surgery Familiar to Neurosurgeons Flexible, Expandable Easy to perform Exposes large area – Parasellar space Provides generous number of working angles

4. Historical Perspective Term pterion derived from the Greek word “pteron” Refers to the wings that were attached to the head of Hermes (the messenger of the Greek gods) Evolved with the contribution of many neurosurgeons over the past century The credit for anterior cranial approach should be given to “Sir Victor Horsley” Horsley(1889) - Pituitary tumor  frontal approach, and faced difficulty “inoperable tumour ”

5. Historical perspective In 1900, Krause was the first to do an extradural subfrontal approach In 1914 Heuer and Dandy’s frontotemporal approach for chiasmal lesion

6. Historical perspective Pterional craniotomy first described by “Professor Mahmut Gazi Yasargil ” in 1975 Originally proposed- microsurgical trt . of cerebral aneurysms in entire circle of Willis The main intention of this approach Smaller craniotomy Less unnecessary exposure in the frontal and temporal lobes Presents a wide fronto -basal exposure and a trans-sylvian dissection (because of extensive sphenoid bone drilling) Enabling less brain retraction, Quick access to the basal cisterns as well as the circle of Willis

7. Pterional Anatomy This craniotomy is centered over and gets its name from the pterion . T he anatomic region of the skull where F rontal P arietal Temporal (squamous part) S phenoid (greater wing) Weakest part of the skull Anterior division of the M iddle Meningeal Artery  runs underneath the pterion.

8. Indication Exposure of fronto -temporo-parietal operculum Sylvian fissure Operating corridor to anterior cisterns of encephalon base Anterior circulation aneurysms (except distal anterior cerebral artery aneurysms) 3rd ventricular area through lamina terminalis Basilar apex and superior cerebellar aneurysms (additional orbitozygomatic osteotomy) Suprasellar and parasellar lesions Medial sphenoid wing tumors

9. Principle of Positioning Supine, neutral position, shoulder at the edge of the table Turn head away from side of craniotomy Neck should be positioned to avoid compression of jugular veins and endotracheal tube Extend neck so that malar eminence is at highest point of operative field (to allow gravity to facilitate brain retraction) Elevation of the head of bed and ipsilateral shoulder elevation with a shoulder roll (used to ensure adequate jugular venous return) Use radiolucent Mayfield skull clamp if intraoperative angiography is planned

10. Head fixation and movements Head fixated-Sugita or Mayfield head holder. Two pins need to be contralateral at superior temporal line right above the temporal muscle, and lastly , the third pin is placed at the ipsilateral mastoid Pay attention to five movements : (1) Traction –Head is move along with the head holder towards the surgeon (2) Lifting the surgical area to a level above the right atrium, to avoid impeding venous return (3) Deflection and (4) Rotation , both related to condition being operated (5) Torsion, with the angle between the head, neck, and shoulder, large enough to give the surgeon a satisfying lateral operating position

11. Patient positioning The angle of head rotation can be tailored according to tip of exposure to be achieved Usual angle for pterional approach  30–60° head rotation to the contralateral side Conditions needing I ncreased deflection with rotation 30–45° from vertical line ( M alar eminence in superior position ) C arotid bifurcation aneurysm MCA aneurysm ACom and ACA aneurysm S uprasellar tumors Conditions needing slight deflection with rotation 45–60 ° (orbital ridge in superior position) Cavernous sinus pathologies and basal lesions I nternal carotid (IC)-ophthalmic aneurysm IC-posterior communicating aneurysm IC-choroidal segment aneurysm .

12. Part preparation (Trichotomy) A fter the patient has been induced general anasthesia and catheterized Hair should be combed with a brush soaked with chlorhexidine or polyvinylpyrrolidone – so as to facilitate the shaving Strip shave of only the incision line with width of about 2 cm A lternatively, upto 2cm behind the incision line. S having just prior to surgery allows better fixating of fields, reduction of infection risks Once the area has been shaved, it is treated with ether-soaked gauze to remove the fat of the scalp and facilitate the fixation of fields M arking of the incision area with methylene blue .

13. Marking, Antisepsis M arking should accurate and adequate S imulate the separation of the skin flap and the consequent bone exposure. S tarting s uperior rim of the zygomatic arch  1cm ant. to tragus S hould not be much anterior  S uperficial temporal artery  F rontal branch of the facial nerve E xtend up to the midline of the skull in the frontal region . ( respecting the hairline) A ntisepsis Povidone iodine scrub, solution and spirit

14. Scalp incision S hould be made with a scalpel Curvilinear incision M idline widow’s peak and extending laterally to 1 cm anterior to the tragus, terminating within a skin crease U se of bipolar coagulation helps avoid bleeding of scalp arteries. P lacement of wet gauze L ater traction of the scalp flap can spare the use of haemostatic clips

15. Temporalis muscle anatomy The temporalis muscle is made up of two parts: O uter part- origin  superior temporal line inserts  coronoid process D eeper part -origin  along the surface of the temporal squama inserts  temporal crest . The temporalis muscle is covered by a superficial fascia, consists of two layers (superficial and deep layers) S eparated in their anterior portion by a pad of adipose tissue and Deep fascia more attached to the skull P rotects its vasculature and innervations (anterior, intermediate and posterior deep temporal arteries - maxillary artery) ( temporal branches of the mandible branches of the trigeminal nerve ).

16. Interfacial dissection Interfacial dissection of the temporalis muscle, ( Yasargil ) -to preserve the frontotemporal branch of the facial nerve -to reduce postoperative cosmetic changes Superficial fascia dissection Should be made vertically starting from the superior temporal line From 1.5 to 2 cm from the superior rim of the orbit to the posterior root of the zygomatic arch Removal of the surface layer of the superficial temporal fascia and its underlying fat pad

17. Temporalis muscle dissection D issection and detachment of the temporalis performed in two stages: Initially, transversal section of the upper portion of the temporal muscle ( C oagulation mode, and not for cutting, in order to avoid much bleeding). Parallel position, 1.5 cm inferior to the superior temporal line L eaving a top flap of muscle attached to the skull surface L ater suture of the inferior part during closure. (cover mainly the anterior burr hole) 2. Consists of performing the detachment of the deep muscular fascia of the skull

18. Trepanation and Craniotomy S hould be three points of trepanation 1st trepanation- between the superior temporal line and the frontozygomatic suture 2nd trepanation- most post. extension of superior temporal line 3 rd trepanation - inf. portion of the squamous part of the temporal bone L esser wing of the sphenoid bone is internally between the 1st and 3rd trepanations  D rilling After the trepanations, the dura must be properly detached from the internal bone surface. C raniotomy - Gigli saw or a craniotome Dural hitch suture taken (to prevent EDH both trans and post-surgery)

19. Basal Drilling -Lesser wing of the sphenoid bone -Orbital roof -remains of the temporal squama Purpose- To achieve bone flattening to facilitate the basal access For minimal brain retraction Further optimized with cisternal opening and the aspiration of CSF Occasionally, the meningo -orbital artery will require cauterization and division

20. Opening of Dura The dura is incised over the frontal lobe Curvilinear dural opening across the SF, based at the medial sphenoid wing The dura is reflected over the temporalis muscle and tented flush with the skull base by sutures to myocutaneous flap A ¼-inch Cottonoid is tucked behind anterior and posterior edges of the dural flap to wick away blood from myocutaneous flap Moist gauze sponges/ Cottonoid strips - to prevent dural desiccation B lue towels placed over these to decrease microscope light glare

21. Sylvian fissure opening Sylvian fissure can be divided into superficial and a deep part Using microscissors and either a scalpel blade number 11, 25G needle, or diamond knife T he superficial portion of Sylvian fissure is cut and dissected starting from the frontal part of superficial Sylvian vein. Relevant anatomical structures identifiable at this stage are ICA, MCA, ACA, and the optic nerve Though the gyrus rectus sometimes obscures the view of the AcomA complex, its resection is rarely indicated This approach grants access to cistern ( around olfactory, carotid artery, chiasmatic cistern, sphenoid part of lateral fissure, cistern in front of lamina terminalis, interpeduncular cistern, ambient cistern, and crural cistern which can be attained by resection of anteromedial segment of uncus.)

22. Closure Closure in layers Check for BP--‐ Valsalva manoeuvre Hitch suture Water tight but not tension Bone flap replacement Skin closed in two layers

23. Limitation Exposure related limitation (acc. to size and site) Modification of craniotomy (operators visualization) Deep and narrow naturally available space between the carotid artery and optic or oculomotor nerves Anterior clinoid plus minus posterior clinoid process (post circulation aneurysm) Removal of zygomatic arch ( parasellar lesion) Gyrus rectus resection ( hinder ideal exposure of the AcomA complex)

24. Complications and how to avoid it Aneurysmal intraoperative rupture Epidural or subdural hematoma Infection P ain on mastication P aralysis if the frontalis, orbicularis oculi ( myocutaneous flap) V isible scarring and other cosmetic defects ( osteomyoplastic monobloc Technique) T emporal hollowing (superficial temporal fat pad atrophy) ( miniplating systems and burr hole covers ) Inadvertent breach of orbit or frontal sinus (waxing)

25. Modification Over time, undergone variations, modifications, and extensions to expand its trajectory To increase the coverage of indications for more complex lesions. A combined approach(Drake et al) advantage of pterional and subtemporal perspectives for posterior circulation aneurysms (Called the “half and half” exposure) Among the most recognized variations Temporopolar Pretemporal Cranioorbitozygomatic Lateral supraorbital approaches.

26. Asian J Neurosurg 2017;12:466-74.

27. Pterional craniotomy video

28. Conclusion The classical pterional approach is attractive and widely used Smaller size craniotomy yet still allowing a wide frontobasal exposure Rapid access to basal cisterns and the circle of Willis Without requiring extensive brain retraction. Limits unnecessary frontal and temporal lobes exposure. Prevents risk of injury to the optic radiations or uncinate fasciculus (avoiding postoperative visual field deficits and aphasia) On cosmetic level of Pterional approach Good skin incision behind the hairline Appropriate size bone flap The osteoplastic craniotomy prevents postoperative temporalis atrophy With the numerous variations, this versatile approach has been and will continue to be the most commonly used cranial approach for years to come.

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