Abstract
The anatomical variations of sylvian vein and cistern were investigated during the
pterional approach in 750 operative cases with different pathologies. All patients
were operated on at the Neurosurgical Department of Atatürk University Medical School,
Erzurum, Türkiye. The patients underwent surgery for the lesions necesstiating the
right or left pterional approach. The findings were recorded during surgical intervention
and observed through the operative sketches of the pathologies, the slides, and videotapes
of the operations. In our study, we surgically classified the variations of 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 52.8% (n = 396), the type
II was found in 19.2% (n = 144), type IM was recorded in 18.2% (n = 137), and type
IV, or hypoplastic and deep form was discovered in 9.8% (n = 73) of patients. The
coursing of sylvian vein was in the temporal side (Temporal Coursing) in 62.4 percent of the cases (n = 469), in the frontal side (Frontal Coursing) in 25 %of the patients (n = 187) and in 9 percent of the cases (n = 67) in the deep
localization (Deep Coursing). Only 3.6% of the cases (n = 27) showed Mixed Coursing. 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, wide and large) or tightly (Sylvian Type B, dose and narrow) approximated on the surface thereby covering the substance 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 herniated into the lateral fronto-orbital
gyrus. The variations of the sylvian cisterns in 750 patients with different pathologies,
were as follows: in 47.7% (n = 358) Sylvian type A, in 27.2% percent (n = 204) Sylvian
type B, in 16.3% (n = 122) frontal type and in 8.8% (n = 66) temporal type. We concluded
that venous perfusion discorder 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 and the importance of preservation
of this vein at that level, will allow the neurosurgeon, believing in the minimally
invasive neurosurgical techniques, to construct a better and safer microdissection
plan, to save time, and can prevent postoperative neurological deficits.
Key words
Sylvian vein - Sylvian cistern - Surgical pitfall - Pterional approach - Variation
