Retrospective Analysis of Morphological and Functional Alterations of the Maxillo-Facial Area in Patients Treated for Neurosurgical Pathologies with a Different Pterional Approach

An alternative approach to temporo mandibular disorders is presented. TMJ disorders are usually studied starting from the field of oral sciences, in this case the TMJ disorders are studied as a side effect or consequence of surgical interventions involving a muscle involved in mandibular movements. TMJ disorders were observed in all patients who underwent skeletal disconnection of the temporal muscle. However the patients where the re-attachment of the muscle was favored by a surgical technique that preserved the structural arrangement of the muscular tissue have largely recovered the functionality of the temporomandibular joints and of the mandibular movements. Received: February 16, 2021


Introduction
Pterional craniotomy is a method which provides wide access to the skull base. This method is considered crucial in neurosurgery, however this approach has a drawback, which is the need to perform a complete dissection of the temporal muscle. This leads to a risk of blemishes and functional alterations concerning chewing: this functional deficit is generally due to damage of the frontal branch of the Facial nerve and to the atrophy of the temporalis muscle [1][2][3].
The advantages of this method are: muscles create an obstacle to the regular cerebral blood flow along the main pathways venous.

Skin Incision and Dissection of Temporalis Muscle
After the incision of the skin, fascia temporalis and temporalis muscle must be incised too using a scalpel, muscles have to be spaced apart together with the skin to avoid injuries to the Frontal and Facial nerve. It is important to save the Temporalis Superficialis artery because it can be used for a intracranial or extracranial vascular bypass.

Craniotomy
On the Temporalis bone two holes have to be done to gain the access: the first hole is posterior, it is done above the zygomatic arch, the second one, also called the "key hole", it is brought forward up to one and a half cm on the frontal bone then with a curvilinear course we cross the superior temporal line and following the cutaneous edge we reach the posterior limit of the bone flap. The following phase of the osteotomy is done with a surgical drill, it creates a bloodless access to the skull base, this method also breaks part of the lesser wing of the Sphenoid bone. The incision of the Dura Mater is done with a semicircular incision around the Lateral Sulcus; then the first meninge can be spaced apart to gain the access to the Arachnoid [1,3,7]. In the pterional approach the risk of injuring the temporal branch of the Facialis nerve is high, this leads to the possibility of causing iatrogenic aesthetic-functional type damage, such as alteration of the tone of the Frontalis muscle and of the Orbicularis muscle: these two branches are particularly evident following the subgaleal pterional approach, but the risk is reduced if the temporal muscle is preserved together with the galeal fascia.
The temporal branch of the facial nerve crosses the zygomatic process, reaching the frontal muscle: if the pterional access incision follows the reference of the temporal fascia, preserving the body of the temporal muscle, injuries to the branches of the facial nerve, that carry the innervation to the Frontal muscles, are avoided [8][9][10][11][12]. The aim of the work is to verify the clinical, morphological and functional implications of the pterional approach in pathologies with neurosurgical indication; specifically, we want to investigate whether the surgical umlaut envisaged by this approach should have a full-thickness linear course, or multiple thicknesses following the planes of each fascia; finally you want to evaluate if the umlaut is safer with the cold blade scalpel or with the monopolar? [13][14][15][16][17].  The authors performed functional tests to evaluate the following parameters:

Materials and Methods
1.
Functionality of the V and VII Cranial nerve,

2.
Postoperative pain assessed by the VAS (visual analog scale),

3.
Width of the mouth opening with reference to the interincisal distance,

4.
Amplitude of lateral movements of the mandible,

Conclusion
From the literature examined, and from a careful analysis of our cases, we can deduce that the best way to dissect the temporal muscle, in the pterional approach, is to incise it together with the skin with a full thickness flap, without detaching the superficial muscle fascia from the subcutaneous plane in order to preserve the peripheral nerve branches that innervate the Frontal muscles. This approach will reduce the risk of alterations in the facial expression, function and sensitivity of the maxillofacial area in treated patients.
Finally, an important indication is to preserve the internal fascia of the temporal muscle, detaching it with a blade: in fact, the cases treated with monopolar coagulation have reported in the long term important hypotrophies associated with aesthetic-functional deficits, with serious repercussions on the chewing capacity.