16 Mini-Pterional Approach
Chad A. Glenn, Joshua D. Burks, Phillip A. Bonney, and Michael E. Sughrue
16.1 Introduction
The mini-pterional approach is a lateral approach, which enables access to the trans-sylvian corridor through a minimally invasive craniotomy.
The approach is indicated for vascular pathology involving the anterior circulation, for extra-axial lesions of the anterior skull base and parasellar area, as well as intra-axial lesions of the inferior aspect of the frontal lobe.
16.4 Skin Incision (Fig. 16.2)
•Small, lightly curved incision
○Starting point: Incision starts just inside the sideburn,
2 fngerbreadths anterior to the pinna.
○Course: Incision runs along the hairline in a downward arc.
○Ending point: It curves anteriorly making a cut no longer than 6-7 cm.
16.2 Indications
•Anterior circulation aneurysms
•Anterior skull base meningiomas
•Parasellar tumors (e.g., craniopharyngiomas)
•Less common: Inferior frontal and fronto-orbital pathology
16.3 Patient Positioning (Fig. 16.1)
•Position: The patient is positioned supine with torso fexed slightly downward.
•Head: The head is extended 20°, rotated 5°to contralateral side for most pathologies.
•The ipsilateral malar eminence is the highest point in the surgical feld.
•The single pin should be placed on the ipsilateral side superior to the mastoid process. On the two-pin arm, one pin is placed superior to the mastoid process on the contralateral side and the other superiorly over the parietal bone.
16.4.1 Critical Structures
•Superfcial temporal artery.
•Frontal branch of the facial nerve.
16.5 Soft Tissue Dissection (Figs. 16.3, 16.4)
•Myofascial and muscular layers
○The scalp is refected antero-inferiorly and postero-superi- orly to expose the superfcial temporoparietal fascia.
○Temporal fascia is elevated in a sub-fascial incision and retracted to protect the frontal branch of the facial nerve.
○A “T-cut” is made in the upper posterior corner of the temporal muscle, and spread away from the inferior edge.
•Bone exposure
○Subperiosteal dissection proceeds until the sphenoid wing is exposed.
Fig. 16.1 Patient positioning. Care must be taken to extend the neck in order to allow gravity to aid in retraction of the frontal lobe in relation to t he anterior fossa. Rotation of the head is variable and is used in order to garner access to more medial or more lateral trajectories.
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Fig. 16.2 Planned incision along the hairline, running over the temporal fossa. Care must be taken to preserve the frontal branch of the facial nerve.
Abbreviations: E = ear; HL = hairline; IL = incision line; N = nose; P = pterion.
Fig. 16.3 Muscles dissection. Skin incision revealing temporal muscle below within
al fascia.
Abbreviations: EL = eyelid; TF = temporal fascia.
16.6 Craniotomy (Figs. 16.5, 16.6)
•Burr hole
○I: A single burr hole can be made anywhere behind the wing of the sphenoid.
•Craniotomy landmarks
○Superiorly/Inferiorly: Small frontotemporal craniotomy below the temporal muscle.
○Medially: Bone work as necessary to fatten the lesser wing of the sphenoid to the meningo-periorbital band (which is skeletonized).
○Anteriorly: Orbital roof is accessed as needed for exposure.
16.6.1 Variants
•Dolenc Approach
○Possible with well-planned craniotomy.
○Cavernous sinus is accessible with gentle retraction of temporal lobe.
16.6.2 Critical Structures
•Optic nerve
•Cavernous sinus
•Middle meningeal artery (MMA)
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Fig. 16.4 Muscles dissection. The temporalis is divided most anteriorly for better access to anterior structures.
Abbreviations: EL = eyelid; GSW = greater sphenoid wing; TM = temporal muscle; TS = temporal squama.
Fig. 16.5 Schematic picture showing the e between pterional (PTC) and mi-
ni-pterional craniotomy (MPC). A, B, C: burr holes sites for standard pterional approach. Abbreviations: MPC = mini-pterional craniotomy; PTC = pterional craniotomy; SON = superior orbital notch; STL = superior temporal line.
16.7 Dural Opening (Fig. 16.7)
•The dural opening is a C-shaped incision.
•The dural fap is then retracted using sutures toward the orbit and sphenoid ridge.
16.7.1 Critical Structures
•Superfcial middle cerebral veins located temporally.
•Orbito-meningeal band entering superior orbital fssure.
•Cavernous sinus.
16.8 Intradural Exposure (Fig. 16.8)
•Parenchymal structures: Pars orbitalis of the frontal lobe, superior temporal gyrus.
•Arachnoid layer: Sylvian cistern, opticocarotid cistern, suprasellar cistern.
16.9 Pearls
•This approach can be tailored as needed for more frontal and/or temporal exposure.
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Fig. 16.6 Craniotomy. Burr hole is above the fronto-sphenoidal suture and anterior to the fronto-parietal suture where the temporal musc ted.
Abbreviations: BH = burr hole; EL = eyelid; GSW = greater sphenoid wing; STL = superior temporal line; TF = temporal fascia; TM = temporal muscle; TS = temporal squama.
Fig. 16.7 Craniotomy is made medially above the lateral canthus and extends laterally beyond the spheno-temporal suture. Abbreviations: D = dura; E = ear; LSW = lesser sphenoid wing; TF = temporal fascia; TM = temporal muscle; TS = temporal squama.
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Fig. 16.8 Dural opening. The posterior aspect of the lesser wing of the sphenoid is drilled away for adequate visualization of anterior structures. A C-shaped dural opening is then made, and the dura is retracted anteriorly as shown above.
Abbreviations: AC = anterior clinoid; D = dura; IFG = inferior frontal gyrus; M2 = second segment of the middle cerebral artery; M3 = third segment of the middle cerebral artery; RG = rectus gyrus; STG = superior temporal gyrus; TF = temporal fascia; TM = temporal muscle; TS = temporal squama.
References
1.Iaconetta G, Ferrer E, Galino AP, et al. Frontotemporal approach. In: Cappabianca P, Califano L, Iaconetta G, eds. Cranial, craniofacial, and skull base surgery. Milan: Springer; 2010
2.Teo C, Sughrue ME. Principles and practice of keyhole brain surgery. New York, NY: Thieme Medical Publishers; 2014
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