Pterional craniotomy

Pterional craniotomy

The resulting bone flap is centered over the depression of the sphenoid ridge. Approximately 33% of the craniotomy is anterior to the anterior margin of temporalis muscle insertion, ≈ 66% is posterior.

With the craniotome, starting at the frontal burr hole the craniotomy is taken anteriorly across the anterior margin of the superior temporal line, staying as low as possible on the orbit (to obviate having to rongeur bone, which is unsightly on the forehead). The distance “B” from the medial extent of the craniotomy to the frontal burr hole is 3 cm for anterior circulation aneurysms. For the approaches to skull base (e.g. Dolenc approach), distance “B” is larger and takes the opening to ≈ the mid orbit. Then from point “B,” a sharp superior turn is made and the opening is taken back to point “A.” The height (“H”) of the craniotomy needs to be only ≈ 3 cm for aneurysms of the Circle of Willis, and slightly larger (≈ 5 cm) for the middle cerebral artery aneurysms. Minimal exposure of the temporal cortex is necessary for aneurysms of the skull base region. For large flaps (e.g. for tumors), “H” is made larger to expose more temporal lobe.


Frontotemporal craniotomy under regional anesthesia during awake craniotomies provides better pain control, a reduction in opioid use, and less somnolence in the early postoperative period 1)


Frontotemporal craniotomy, also known as “pterional craniotomy” (PC), provides an optimal microscopic exposure and a wide open working space for manipulation of intracranial structures, and it has been widely used in the field of neurosurgery for treatment of lesions in the anterior and posterior circulations 2).

The pterional craniotomy provides wide, multidirectional access to the anterior and middle cranial fossae as well as many structures of the interpeduncular fossae.

Other frontotemporal craniotomies derived from the pterional 3) 4) and supraorbital 5) craniotomies, as are the combined epi- and subdural approach with anterior clinoid removal 6) 7) and the orbitozygomatic extension of the pterional craniotomy 8) 9).

The pterional craniotomy is well established for microsurgical clipping of most anterior circulation aneurysms. The incision and temporalis muscle dissection impacts postoperative recovery and cosmetic outcomes.

The minipterional (MPT) craniotomy offers similar microsurgical corridors, with a substantially shorter incision, less muscle dissection, and a smaller craniotomy flap.


Although pterional craniotomy and its variants are the most used approaches in neurosurgery, few studies have evaluated their precise indications.

da Silva et al., evaluated the pterional (PT), pretemporal (PreT), and orbitozygomatic (OZ) approaches through quantitative measurements of area, linear, and angular exposures of the major intracranial vascular structures.

Eight fresh, adult cadavers were operated with the PT, followed by the PreT, and ending with the OZ approach. The working area, angular exposure of vascular structures and linear exposure of the basilar artery were measured.

The OZ approach presented a wider area (1301.3 ± 215.9 mm2) with an increase of 456.7 mm2 compared with the PT and of 167.4 mm2 to the PreT (P = 0.011). The extension from PT to PreT and OZ increases linear exposure of the basilar artery. When comparing the PreT and OZ, they founded an increase in the horizontal and vertical angle to the bifurcation of the ipsilateral middle cerebral artery (P = 0.005 and P = 0.032, respectively), horizontal angle to the basilar artery tip (P = 0.02), and horizontal angle to the contralateral ICA bifurcation (P = 0.048).

The OZ approach offered notable surgical advantages compared with the traditional PT and PreT regarding to the area of exposure and linear exposure to basilar artery. Regarding angle of attack, the orbital rim and zygomatic arch removal provided quantitatively wider exposure and increased surgical freedom. A detailed anatomic study for each patient and surgeon experience must be considered for individualized surgical approach indication 10).

see pterional approach.

Pterional craniotomy complications.

Left pterional craniotomy for thrombectomy and clipping of ruptured left MCA giant aneurysm

Mini-pterional craniotomy


1)

Bojaxhi E, Louie C, ReFaey K, Gruenbaum SE, Leone BJ, Bechtel P, Barbosa MP, Chaichana KL, Quinones-Hinojosa A. Reduced Pain and Opioid Use in the Early Postoperative Period in Patients Undergoing a Frontotemporal Craniotomy under Regional vs General Anesthesia. World Neurosurg. 2021 Jun;150:e31-e37. doi: 10.1016/j.wneu.2021.02.009. Epub 2021 Mar 5. Erratum in: World Neurosurg. 2022 Apr 19;163:2. PMID: 33684585.
2)

Kang HJ, Lee YS, Suh SJ, Lee JH, Ryu KY, Kang DG. Comparative analysis of the mini-pterional and supraorbital keyhole craniotomies for unruptured aneurysms with numeric measurements of their geometric configurations. J Cerebrovasc Endovasc Neurosurg. 2013 Mar;15(1):5–12.
3)

Yasargil MG: Microneurosurgery. Stuttgart: Georg Thieme, 1984, Vol I
4)

Yasargil MG, Fox JL, Ray MW: The operative approach to aneurysms of the anterior communicating artery, in Krayenbül H (ed): Advances and Technical Standards in Neurosurgery. Wien: Springer-Verlag, 1975, Vol 2, pp 114–170
5)

Jane JA, Park TS, Pobereskin LH, et al: The supraorbital approach: technical note. Neurosurgery 11:537–542, 1982
6)

Dolenc VV: A combined epi-and subdural direct approach to carotidophthalmic artery aneurysms. J Neurosurg 62:667–672, 1985
7)

Dolenc VV, Yasargil MG: Anatomy and Surgery of the Cavernous Sinus. Wien: Springer-Verlag, 1989
8)

Fujitsu K, Kiwabara T: Zygomatic approach for lesions in the interpeduncular cistern. J Neurosurg 62:340–343, 1985
9)

Hakuba A, Liu S, Nishimura S: The orbitozygomatic infratemporal approach: a new surgical technique. Surg Neurol 26: 271–276, 1986
10)

da Silva SA, Yamaki VN, Solla DJF, Andrade AF, Teixeira MJ, Spetzler RF, Preul MC, Figueiredo EG. Pterional, Pretemporal, and Orbitozygomatic Approaches: Anatomic and Comparative Study. World Neurosurg. 2019 Jan;121:e398-e403. doi: 10.1016/j.wneu.2018.09.120. Epub 2018 Sep 26. PubMed PMID: 30266695.

Pterional Transzygomatic approach

Pterional Transzygomatic approach

This approach allows wide access to different topographic areas (clinoid process region and clinoidal ICA, the entire cavernous sinus (CS), and the posterior fossa from the interpeduncular fossa to the facial nerve) via a lateral trajectory 1).

see Pretemporal transzygomatic transcavernous approach

see Transzygomatic approach with anteriorly limited inferior temporal gyrectomy.

Videos

Position

The patient is positioned in the supine position with the head attached to the table with a Mayfield skull clamp. The head is elevated and left parallel to the ground plane.

Incision

The incision starts at the level of the lower edge of the zygomatic arch, slightly anterior to the tragus, and extends behind the hairline towards the contralateral pupillary line. In patients with thick subcutaneous tissue, a preauricular incision can be extended downwards quite safely, up to 25 mm below the superior edge of the zygomatic arch.

The anteroposterior position of the incision will depend upon the type and location of the lesion to be treated.

Dissection of the soft tissues

The dissection of soft tissues starts with subgaleal disection until the fatty tissue over the temporal aponeurosis is recognized. This sector roughly corresponds to the anterior fourth of the temporal muscle and is located immediately posterior to the frontal branch of the superficial temporal artery. From there, an incision is made on the external layer of the temporal fascia which, together with the interfascial fat, is dissected anteriorly in that plane to protect the frontal branch of the facial nerve. In this inter- fascial space runs a small vein, perpendicular to the incision, which must be coagulated and cut. Afterwards, the orbital rim is exposed at the top of the field, with the zygomatic arch lying below.

Sectioning of the zygomatic arch

The zygomatic arch is sectioned with two vertical cuts: a posterior cut immediately before the temporo–mandibular joint; and an anterior cut just behind the union of the zygomatic arch and zygomatic bone. Thus, the zygomatic arch is moved downwards, together with the masseter muscle.

The temporal muscle is separated from the skull via retrograde dissection, so as to avoid post-operative muscular atrophy.

A small cuff of muscle and fascia, at the level of the superior temporal line, is kept in place for reinsertion of this muscle at the end of surgery. Thus, the muscle is taken downwards, through the space left by the sectioned zygomatic arch. This procedure allows for complete exposure of the floor of the middle fossa.

Craniotomy

A pterional approach (fronto–temporo–sphenoidal craniotomy) is performed in the usual way 2) 3).

The quantity of frontal and temporal bone to be removed depends upon the type and location of the lesion to be resected. The greater wing of the sphenoid bone and the squamous portion of the temporal bone are drilled out until complete exposure of the lateral aspect of the temporal dura is achieved.


Two burr holes are made in the pterion above and below the lower wing of the sphenoid bone and the bone between them is flattened with a burr. A frontotemporal bone flap is cut with a vertical saw that includes the temporal muscle cuff. An additional hole below the upper temporal line may be helpful for this purpose. A free bone flap is lifted elevating and breaking down the bone. In the event of tumors that infiltrate the pterional bone or the external third of the sphenoid wing, it may be necessary to make the craniotomy around the involved bone, which is then removed by drilling or with a bone gouge. This is a pathological bone with reactive hyperostosis and/or tumor infiltration that must be removed, sometimes with profuse vascularization.

Possibilities

The transzygomatic approach offers excellent exposure to the floor of the middle fossa and the lateral wall of the cavernous sinus (both intradurally and extradurally). Also, combined with a pretemporal approach, it affords a good view of the interpeduncular cistern; and using a transtemporal approach, it provides good access to the insular region.

Once the craniotomy has been performed, the anatomical possibilities are numerous:

1.- intradural access to the middle fossa

2.- intradural pretemporal access to the basal cisterns

3.- intradural transtemporal access to the insular region

4.- extradural access to the middle fossa 4).

Case series

José M González-Darder in 2019 presented a prospective series of 26 cases with SWMs larger than 3 cm in one of its main diameter. All patients were studied following the same clinical and imaging procedures. The surgical approach was through a pterional transzygomatic craniotomy. The surgical procedure has the following steps: 1. Extradural tumor devascularization and resection of the hyperostotic and/or infiltrated bone and then intradurally; 2. Intradural tumor debunking; 3. Microdissection of vascular branches and perforators from the capsule; 4. Identification of the optic and oculomotor nerves and internal carotid artery; 5. Tumor capsule dissection and resection; 6. Dural resection or cauterization; 7. Dural and bone reconstruction and closing. Results  All lesions were completely removed. Most complications were transient. The most relevant complication was a large middle cerebral artery infarct with permanent hemiplegia despite a decompressive craniotomy. Conclusion  Large SWMs can be considered as a single pathology regarding the surgical approach and intraoperative microsurgical procedure strategies. The pterional transzygomatic approach allows an extradural devascularization of the tumor and an extensive bone resection that facilitates the intradural stage of tumor resection. The proposed approach allows a wide and radical resection of the duramater and bone that increases the Simpson grade. However, surgery does not control other biological or molecular prognostic factors involved in tumor recurrence 5).


José M González-Darder et al. presented the experience with the transzygomatic pterional approach in the treatment of neurosurgical pathology of the base of the skull located in the middle cranial fossa and surrounding areas.

A retrospective study of pathological findings, surgical outcomes and complications in a series of 31 cases operated on between 2009 and 2011 using a transzygomatic pterional approach.

The lesions involved the sphenoid wing (25.9%), several regions due to invasive growth pattern (19.5%), the temporal lobe (16.1%) and cavernous sinus (12.9%). The others were located in the floor of the middle fossa, Meckel’s cave, incisural space, cisterns, and infratemporal region. The pathological nature of the lesions was: benign meningioma (42%), temporal lobe tumour (19.5%), vascular disease (12.9%), inflammatory lesions (6.4%), atypical meningioma (6.4%), epidermoid cyst (6.4%), neurinoma (3.2%) and poorly differentiated infratemporal carcinoma (3.2%). The approach was usually combined extra-intradural (58.1%) and, less frequently, just extradural (16.1%) or intradural (25.8%). Approach-related complications were minor: haematomas in the wound not requiring treatment (67.8%), superior transient facial paresis (9.7%), transient temporomandibular joint dysfunction (12.9%) and atrophy of the temporal muscle (16.2%). There were no hardware-related complications or cosmetic issues related to the osteotomy and posterior osteosynthesis of the zygomatic arch.

The pterional approach combined with osteotomy of the zygomatic arch allows mobilising the temporalis muscle away from the temporal fossa, consequently exposing its entire surface to complete the temporal craniotomy up to the middle fossa; it helps to access and treat pathology in this region or it can be used as a corridor to approach surrounding areas 6).

References

1)

Chotai S, Kshettry VR, Petrak A, Ammirati M. Lateral transzygomatic middle fossa approach and its extensions: Surgical technique and 3D anatomy. Clin Neurol Neurosurg. 2014 Dec 29;130C:33-41. doi: 10.1016/j.clineuro.2014.12.014. [Epub ahead of print] PubMed PMID: 25576883.
2)

González-Darder JM, Quilis-Quesada V, Botella-Maciá L. [Transzygomatic pterional approach. Part 2: Surgical experience in the management of skull base pathology]. Neurocirugia (Astur) 2012; 23(03):96–103
3)

Quilis-Quesada V, Botella-Maciá L, González-Darder JM. [Transzygomatic pterional approach. Part 1: anatomical study]. Neurocirugia (Astur) 2012;23(02):47–53
4)

Campero A, Campero AA, Socolovsky M, Martins C, Yasuda A, Basso A, Rhoton A. The transzygomatic approach. J Clin Neurosci. 2010 Nov;17(11):1428-33. doi: 10.1016/j.jocn.2010.03.023. Epub 2010 Aug 6. Review. PubMed PMID: 20692168.
5)

González-Darder JM. Combined Extradural and Intradural Pterional Transzygomatic Approach to Large Sphenoid Wing Meningiomas. Operative Technique and Surgical Results. J Neurol Surg B Skull Base. 2019 Jun;80(3):244-251. doi: 10.1055/s-0038-1668538. Epub 2018 Aug 21. PubMed PMID: 31143566; PubMed Central PMCID: PMC6534744.
6)

González-Darder JM, Quilis-Quesada V, Botella-Maciá L. [Transzygomatic pterional approach. Part 2: Surgical experience in the management of skull base pathology]. Neurocirugia (Astur). 2012 May;23(3):96-103. doi: 10.1016/j.neucir.2012.04.005. Epub 2012 May 19. Spanish. PubMed PMID: 22613467.
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