This microsurgical study attempts to analyze the intraoperative anatomic vascular variations associated with the anterior communicating artery (ACoA) aneurysms in 120 patients who were operated on at the Neurosurgical Department of Atatürk University Medical School, Erzurum, Türkiye. All patients underwent radical surgery for aneurysm by the right pterional approach. The findings were recorded during surgical intervention and through the slides and videotapes of the operations. A total of 72 (60%) of our patients had vascular variations in the vicinity of the ACoA. Marked hypoplasia of the A1 segment of anterior cerebral artery (ACA) at the right or left side (26.6%, n = 32), median artery of the corpus callosum (MACC) (14%, n = 17), duplication of the ACoA (8.3%, n = 10), duplication of the A1 segment of ACA (7.5%, n = 9) and azygous pericallosal artery (3.3%, n = 4) were the variations that were observed during operations. A retrospective study of the cerebral angiograms of the cases indicated that preoperative diagnosis of the A1 or ACoA duplication was not possible, 14 (82.4%) of the 17 MACC's were easily identified, while three (17.6%) could not be diagnosed. From this intraoperative study, we concluded that, regardless of whether a vascular variation has been identified preoperatively, ACoA aneurysm surgery should be undertaken with the possibility of an MACC in mind. The recognition of the anatomic variations of the ACoA and the detailed knowledge of the microvascular relationships of the aneurysms will allow the neurosurgeons to construct a better and safer microdissection plan to save time on the one hand and to prevent postoperative neurological deficits on the other.

The pterional approach is commonly employed in surgery of the anterior circulation and upper basilar artery aneurysms, as well as for the tumors of orbital, retroorbital, sellar, chiasmatic, subfrontal and prepontine areas and lesions around the sella especially for lesions behind the clivus. Also tumors arising from the medial sphenoid ridge, the superior orbital fissure, the anteromedial temporal surface, or the cavernous sinus region are approached through a pterional exposure. The surgical technique is based on the experience, training and observation of the neurosurgeon. One technique is not necessarily better than another. Regardless of the surgical technique, the end results depend on a rigorous, methodical, systematic, and step-by-step approach to the target, securing it with minimal injury to surrounding structures. In this study, we have analyzed the intraoperative anatomical findings of the Sylvian vein and fissure, lenticulostriatal artery, olfactory nerve, and recurrent artery of Heubner and showed the surgical pitfalls in 700 patients with different diagnoses that were operated on with the pterional approach. The findings were recorded during surgical interventions and through the slides and videotapes of the operations. Also, we have stressed the preservation of the frontotemporal branch of the facial nerve, the delicate retraction of frontal lobe, the cottonoid retraction in temporal lobe and the preservation of olfactory nerve functions.

Damage to the olfactory nerve during the pterional approach to the anterior communicating artery aneurysms has not previously been investigated in a quantified manner. In this retrospective study, 100 patients with anterior communicating artery aneurysms, for whom the pterional approach was employed, were observed from the point of view of postoperative olfactory nerve function. In the postoperative period only three cases suffered from the impaired sense of smell ipsilateral to the side of surgery. 15 patients objectively showed olfactory nerve distinctions. The functions of olfactory nerve could be preserved at a relatively high rate of 85 per cent. This high rate resulted from the microtechnique employed as well as the relatively cautious frontal lobe retraction which was less than 1.5 cm.

The anatomical variations of Sylvian vein and cistern were investigated during the pterional approach in 230 patients with 276 aneurysms of anterior circulation arteries, that were operated on at the Neurosurgical Department of Atatürk University Medical School. Erzurum, Türkiye. All patients underwent radical surgery for aneurysm by the right or left pterional approach. The findings were recorded during surgical intervention and observed through the slides and videotapes of the operations. In our study, we surgically classified the variations of the Sylvian vein, according to its branching and draining patterns. Type I: The fronto-orbital (frontosylvian), fronto-parietal (parietosylvian) and anterior temporal (temporosylvian) veins drain into one sylvian vein. Type II: Two superficial Sylvian veins with separated basal vein draining into the sphenoparietal and Rosenthal's basal vein. Type III: Two superficial Sylvian veins draining into the sphenoparietal and the superior petrosal veins. Type IV: Hypoplastic superficial Sylvian vein and the deep one. Four types of Sylvian vein variations were defined as follows. The Type I was seen in 45% (n = 103), the Type II was found in 29% (n = 67), Type III was recorded in 15% (n = 34) and Type IV, or hypoplastic and deep form was discovered in 11% (n = 26) of patients. The course of the Sylvian vein was on the temporal side (Temporal Coursing) in 70 percent of the cases (n = 160), on the frontal side (Frontal Coursing) in 19% of the patients (n = 45) and in 8 percent of the cases (n = 18) in the deep localization (Deep Coursing). Only 3 percent of the cases (n = 7) showed a mixed course. The variations of the Sylvian cisterns were classified into three types, according to the relationships between the lateral fronto-orbital gyrus and the superior temporal gyrus. In Sylvian Type, the frontal and temporal lobes are loosely (Sylvian Type A, Large) or tightly (Sylvian Type B, Close and Narrow) approximated on the surface thereby covering the area of the Sylvian cistern. In frontal type, the proximal, part of the lateral fronto-orbital gyrus herniated into the temporal lobe. In temporal type, the proximal part of the superior temporal gyrus hemiated into the lateral fronto-orbital gyrus. The variations of the Sylvian cisterns in 230 patients were as follows: in 31% (n = 71) Sylvian Type A, in 21% (n = 48) Sylvian Type B, in 34% (n = 78) Frontal Type, and in 14% (n = 33) Temporal Type. We concluded that venous perfusion disorder of the brain is the most important factor during the pterional approach. Careful intraoperative assessment and protection of the Sylvian vein, which is a surgical pitfall, is an indispensable part of the operation. The recognition of the anatomical variations of the Sylvian vein and cistern, and the detailed knowledge of the microvascular relationships at that level will allow the neurosurgeon to construct a better and safter microdissection plan, to save time and can prevent postoperative neurological deficits.

This study attempts to analyse the intra-operative anatomical findings of the lenticulostriate artery (LSA) in 60 patients with middle cerebral artery (MCA) aneurysms who were operated on at the Neurosurgical Department of Atatürk University Medical School, Erzurum, Türkiye. All patients underwent radical surgery for aneurysm by the right or left pterional approach. The findings were recorded during surgical intervention using slides and videotapes of the operations. On average there were 4 (range, 1-14, total number = 240) LSAs, in one hemisphere, per case with MCA aneurysm. Twenty percent of LSAs (n = 48) arise from the prebifurcation part of the M1 segment, 65% (n = 156) arise from the postbifurcation part of the M1 segment, and 15% (n = 36) arise from the proximal part of the M2 segment. The great majority of the LSAs (85%, n = 204) originated along the proximal part of the MCA. Of a total of 240 LSAs, 125 (52%) originated from one single large vessel, a stem artery which then divided after 2-10 mm into many branches, 85 (35%) originated as two large proximal trunks, and 30 (13%) originated as multiple small arteries arising along the whole infero-medial wall of the M1 segment of MCA. We concluded that recognition of the anatomical variations of the LSA and detailed knowledge of the microvascular relationships of the MCA aneurysms, will allow neurosurgeons to construct a better and safer microdissection plan, to save time, and to prevent postoperative neurological deficits.