|Year : 2020 | Volume
| Issue : 6 | Page : 1321--1322
Facial Nerve Preservation During Temporal Exposure- Search for an Optimal Strategy
Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India
Dr. Girish Menon
Department of Neurosurgery, Kasturba Medical College, Manipal Academy of Higher education, Manipal, Karnataka
|How to cite this article:|
Menon G. Facial Nerve Preservation During Temporal Exposure- Search for an Optimal Strategy.Neurol India 2020;68:1321-1322
|How to cite this URL:|
Menon G. Facial Nerve Preservation During Temporal Exposure- Search for an Optimal Strategy. Neurol India [serial online] 2020 [cited 2021 Feb 26 ];68:1321-1322
Available from: https://www.neurologyindia.com/text.asp?2020/68/6/1321/304079
Exposure of the temporal region is a prerequisite for surgical approaches to more than three-fourths of all intracranial neurosurgical procedures. Dissection of the scalp over the temporalis region is an integral initial step of pterional craniotomy, frontotemporal craniotomy with or without its orbital and zygomatic extensions, bifrontal craniotomy, and almost all extensions of temporal craniotomy. Comprehending the surgical anatomy of the temporalis muscle, its fascial coverings, the multiple temporal fat pad layers and the course of facial nerve branches remains a complex challenge for neurosurgeons. The diverse nomenclature of the fascial layers and the fat pad layers often adds to the confusion. Need for a perfect understanding of this regional anatomy can never be overemphasized. The authors have provided valuable insights into the surgical anatomy of the temporal area through cadaveric dissection and this effort of theirs is highly commendable.
The scalp layers over the temporalis muscle below the superior temporal line differs from the rest of the cranial vault. Multiple authors have attempted to decode the surgical anatomy of this region. The nomenclature is confusing but what is certain and undisputable is that there are essentially two layers of fascia and three layers of fat pad.,, The temperoparietal fascia which is almost merges with the overlying galea is a thin sheet made up of multiple layers and is integrated with thin fibrous septa deep to the subcutaneous tissue. Beneath this temperoparietal fascia is the deep temporal fascia which a thick, dense tough fibrous layer covering the temporal muscle. This deep temporal fascia again splits into superficial and deep layers. The three layers of fat pad include i) the subgaleal/suprafascial fat pad superficial to the deep temporal fascia ii) the interfascial fat pad between the two layers of the deep temporal fascia and iii). the subfascial fat pad between the temporalis muscle and the deep layer of the temporal fascia. Above the superior temporal line, the facial nerve branches lie within the subgaleal fat pad in the plane between the galea and the pericranium. Below the superior temporal line, the facial nerves lies between the galea and superficial temporal fascia.
The main challenges in the exposure of the temporal region are i) avoiding injury to the facial nerve and its branches ii) provide optimal exposure without excessive retraction of the temporalis muscle iii) prevent temporalis muscle atrophy. The key to success depends on i) Careful dissection in the right plane, b) starting the fascial incision behind the frontal branch of the superficial temporal artery during flap raising or at a point 2.5 to 4 cm from the superior orbital rim or c) careful elevation of the fascial-pericranial flap without excessive traction d) placing the fascial incision on the medial surface of the superior border of the zygomatic arch approximately 2 cm anterior to tragus and e) by avoiding excessive cauterization.,,,
Traditionally, the two common approaches adopted for temporal flap elevation are the subfascial and the interfacial technique. The sub fascial technique is simpler, more efficient, has higher chances of facial nerve preservation but carries a higher risk of temporalis atrophy and causes more bleeding from the muscle tissue. The interfascial technique is technically more challenging but provides the best integrity of the temporalis muscle and carries least risk of temporal atrophy. The authors in this article compare five different approaches a) between temporoparietal fascia and the superficial layer of deep temporal fascia through superficial fat pad. b) between two layers of deep temporal fascia through an intermediate fat pad c) the combination of the above two d) below the deep layer of deep temporal fascia and above the temporal muscle e) the skin, fascia and temporal muscle raised as a single flap, -sub facial. The authors observed a high risk of facial nerve injury in the first and third approach, higher risk of vascular comprise with the fourth approach. The drawback of the fifth approach was decreased visualization and excessive retraction on account of the bulk of the muscle. They conclude by recommending the interfascial approach as the best strategy in terms of facial nerve preservation.
The observations by the authors through their meticulous cadaver study corresponds to published literature on this subject. The preference for the interfacial approach was reported by Yasergil way back in 1987. Many other authors have suggested subfascial approach as an easier alternative. The following cardinal principles of dissection, however, remain same for all approaches. Avoid excessive coagulation on the galea or temporoparietal fascia anterior to the superficial temporal artery, a sub periosteal dissection at the level of the zygomatic arch while the detaching the temporal muscle, careful elevation of the muscle along with the periosteum in order to protect the blood supply. Interfascial approach is best reserved for experienced surgeons and in cases of bicoronal skin incision, or in the lateral supraorbital approach in which the temporalis muscle does not need to be mobilized. Young neurosurgeons may find the subfascial approach easier and safer in terms of facial nerve preservation. The surgeon ought to customize his approach based on the extent of exposure needed and his expertise.
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Conflicts of interest
There are no conflicts of interest.
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