Morphometric variants of the posterior communicating artery

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O.A. Fomkin - Saratov State Medical University named after. IN AND. Razumovsky Ministry of Health of Russia, assistant at the Department of Human Anatomy, Candidate of Medical Sciences; V.N. Nikolenko - State Budgetary Educational Institution of Higher Professional Education First Moscow State Medical University named after. THEM. Sechenov Ministry of Health of Russia, Vice-Rector for Scientific and Innovation Activities, Professor of the Department of Human Anatomy, Director of the Research Institute of Molecular Medicine, Professor, Doctor of Medical Sciences; Yu.A. Gladilin – State Budgetary Educational Institution of Higher Professional Education Saratov State University named after. IN AND. Razumovsky Ministry of Health of Russia, Associate Professor of the Department of Human Anatomy, Doctor of Medical Sciences.

Introduction. Variability as a general biological phenomenon does not lose its relevance and deserves the attention of many scientists [1, 2]. Variability shows the plasticity of living systems and is associated with the implementation of the adaptive strategy of a natural population. The study of variability makes it possible to judge the interaction of the genotype with environmental factors during ontogenesis [3].

In response to the demands of clinical medicine, at present, detailed information is required not so much on the typical structure or average anatomical norm of an organ, but on the entire spectrum of its individual, typical and combined variability [2]. This also applies to the arterial vessels of the brain.

The subject of this study is the posterior communicating artery (PCA). As a branch of the cerebral part of the internal carotid artery, it participates in the formation of the arterial (Circle of Willis) circle of the brain. It has been proven that blood through this artery can flow in both directions [4]. In this regard, the PCA plays an important role in the implementation of compensatory collateral blood flow between the systems of the internal carotid and vertebral arteries.

The structure of the posterior communicating arteries varies greatly. Compared to other cerebral arteries, they have a small diameter and almost a pinpoint lumen [5-7].

Purpose of the study: to determine the variants of the posterior communicating artery (PCA) of adults depending on the individual and combined variability of its morphometric parameters.

Materials and methods . The study material was PCA obtained from autopsies of 115 corpses of people aged 21 to 84 years who died for reasons not related to acute or chronic cerebrovascular pathology. A total of 230 artery samples were examined. To study the morphology of the artery, transverse millimeter sections were made using a razor. Then the sections were placed in a Petri dish with saline solution and the outer diameter and wall thickness of the artery were measured under a microscope with an accuracy of 0.01 mm. The diameter of the artery lumen is presented in the study as the difference between the outer diameter and twice the thickness of the artery wall.

The obtained data were processed by the variation-statistical method using the Statistica-6 application package and Microsoft Exsel Windows-XP. To check the presence of a normal distribution, the Kolmogorov-Smirnov test was used. The distribution of parameters in the studied sample did not differ from normal. In this regard, for all parameters, the minimum and maximum values, the arithmetic mean (M), the error of the arithmetic mean (m), the standard deviation (s), and the coefficient of variation (Cv) were determined. To assess the reliability of differences between series, a parametric test (Student's test) was used. In this case, the differences were considered significant at a 95% probability threshold (p < 0.05). When studying individual variability, like most researchers dealing with the range of anatomical norms, we took the variation interval M ± σ as the average value of a trait. Since statistically significant gender differences in the length, wall thickness and lumen diameter of the PCA were found [6], variations in these parameters were calculated separately for men and women.

Results. The average values of the morphometric parameters of the PCA (230 samples), excluding gender, age and cerebral hemisphere, were: 1) length 12.26±0.19 mm (A=5.30-20.10 mm; s=2.89 mm; Сv=23.6%); 2) outer diameter – 1.33±0.02 mm (A=0.80-2.10 mm; s=0.26 mm; Cv=19.2%); 3) wall thickness – 0.23±0.01 mm (A=0.12-0.40 mm; s=0.06 mm; Cv=26.2%); 4) lumen diameter – 0.88±0.02 mm (A=0.46-1.46 mm; s=0.25 mm; Cv=28.0%).

Significant variability in the morphometric parameters of the PCA made it possible to identify groups of variants of their values (Table 1).

According to the length of the PCA, they were divided into: short - length less than 9.89 mm in men and less than 8.80 mm in women; medium in length - with a length from 9.90 to 15.72 mm for men and from 8.81 to 11.51 for women; long – with a length of more than 15.73 mm in men and more than 11.52 mm in women. The average age of subjects with short PCAs was 1.2 times greater than that of people with long arteries – 51.3±2.9 years and 43.0±2.6 years, respectively (p=0.039). The quantitative ratio of men and women in the group of subjects with short arteries is 39.5 and 60.5%; in the group of subjects with long arteries – 71.9 and 28.1%.

Based on the size of the outer diameter, SSAs are: thin - diameter less than 1.06 mm; medium diameter (medium wide) - the diameter ranges from 1.07 to 1.59 mm and wide - with a diameter of more than 1.60 mm. Subjects with wide PCA were on average 1.2 times older than people with thin arteries - 55.0±3.0 years and 45.5±2.1 years, respectively (p=0.011). The quantitative ratio of men and women in the group of subjects with thin arteries is 59.0 and 41.0%; in the group of subjects with wide arteries, the representation of men and women is equal – 50% each.

Based on the wall thickness, the PCA was divided into: thin-walled - wall thickness less than 0.17 mm in men and less than 0.14 mm in women; medium in thickness - with a wall thickness from 0.18 to 0.30 mm for men and from 0.15 to 0.25 mm for women; thick-walled - with a wall thickness of more than 0.31 mm in men and more than 0.26 mm in women. The average age of subjects with thick-walled PCAs was 1.7 times greater than that of people with thin-walled arteries - 69.2±2.3 years and 40.7±2.5 years, respectively (p=1·10-6). The quantitative ratio of men and women in the group of subjects with thin-walled arteries was 25.7 and 74.3%; in the group of those studied with thick-walled arteries – 78.9 and 21.1%.

Depending on the size of the lumen diameter, we have identified PSA: with a narrow lumen - the lumen diameter is less than 0.58 mm in men and less than 0.68 mm in women; with an average lumen - the diameter of the lumen varies from 0.59 to 1.07 mm in men and from 0.69 to 1.19 mm in women; with a wide lumen - the lumen diameter exceeds 1.08 mm in men and 1.20 mm in women. The age of subjects with a narrow and wide lumen of the PCA did not differ significantly - 51.2 ± 2.5 years and 45.6 ± 3.1 years, respectively (p = 0.163). The quantitative ratio of men and women in the group of subjects with a narrow lumen of the PCA was 75.6 and 24.4%; in the group of those studied with a wide lumen of the PCA – 43.6% and 56.4%.

It was noted that approximately 71.9% of all thin ACAs had a narrow lumen, and 28.2% had an average lumen. At the same time, thin PCAs had thin wall thickness in 23.1% of cases, thick wall thickness in 5.2% of cases, and medium wall thickness in 71.8% of cases (Table 2).

Medium-wide arteries in 87.1% of cases were characterized by an average lumen diameter; in 7.7% of cases, such PCAs had a narrow, and in 5.2%, a wide lumen diameter. Medium-wide arteries, as a rule, had an average wall thickness (67.1% of observations); thin- and thick-walled PCA were also found in this group – in 12.9 and 20% of cases, respectively.

Wide PCAs had a wide lumen diameter in 86.1% of cases and an average lumen diameter in 13.9% of cases. Moreover, in 13.9% of cases they were thin- or thick-walled, and in the remaining 72.2% they were characterized by an average wall thickness.

The combined variability of the morphometric parameters of the PCA made it possible to identify 18 of its types. The most common are medium-wide ACAs with an average wall thickness and an average lumen (43.0%). Rare types (frequency of occurrence less than 1%) include thin PCA (with an average wall thickness and lumen diameter, with a thin wall and a narrow lumen, a thick wall and a narrow lumen, a thick wall and an average lumen); ASA with a medium outer diameter, a thick wall and a wide lumen; wide PCA with a thick wall and medium lumen (Fig. 1). Thin-walled SSAs based on our material never had a wide lumen diameter.

Rice. 1.Frequency of occurrence of types of PSA,% ( OD – outer diameter , TS – wall thickness, DP – lumen diameter ): 1 – average for ND, TS and DP; 2 – thin with medium TS and narrow DP; 3 – wide with medium TC and wide DP; 4 – average in ND, with a thick wall and average DP; 5 – average according to ND with a thin wall and average DP; 6 – thin with a thin wall and medium DP; 7 – average according to ND with a thick wall and narrow DP; 8 – average according to ND, with a thin wall and wide DP; 9 – average for ND, vehicles with narrow DP; 10 – wide with a thin wall and wide DP; 11 – wide with average wall thickness and average DP; 12 – wide with a thick wall and wide opening; 13 – thin with medium TC and medium clearance; 14 – average in ND, with a thick wall and wide DP; 15 – thin with a thin wall and narrow DP; 16 – thin with a thick wall and narrow DP; 17 – thin with a thick wall and medium DP; 18 – wide with a thick wall and medium DP.

Discussion. The vast majority of works concerning PCA are devoted to variants of its development: aplasia, hypoplasia, the presence of a vascular network at the site of the artery, etc. [5, 8, 9]. We presented information on the individual typological variability of the morphometric parameters of the PCA for the first time.

As a result of the study, it was revealed that the morphological parameters of the PCA (length, outer and inner diameter, wall thickness) are characterized by significant individual variability. The coefficient of variation of the studied parameters varies from 19.2% (outer diameter) to 28.0% (lumen diameter). For each of the parameters, we have identified 3 groups of arteries: I – with a value of the attribute less than average (<М-σ); II – with the average value of the trait (M±σ); III – with a trait value greater than average (>M+σ). No clear pattern was found in the predominance of men or women in the extreme groups of variability (groups I and II). Thus, among subjects with short, thin-walled arteries and arteries with a wide lumen, women predominate, and among subjects with long, thin, thick-walled arteries and arteries with a narrow lumen, men predominate. In the group of those studied with wide ACAs, the percentage representation of men and women is the same.

The average age of subjects whose PMA, based on the size of their outer diameter, wall thickness and lumen diameter, belongs to group III, is statistically significantly 1.2-1.7 times greater than that of people with PMA belonging to group I variability. The average age of men and women with short PCA (group I), on the contrary, is 1.2 times greater than that of people with long PCA (group III). The age of subjects with narrow or wide lumen PCA did not differ significantly.

Conclusion. Thus, the analysis of individual variability in the length, outer and inner diameters and wall thickness of the PCA made it possible to identify 3 groups of artery variants for each of the parameters: with an average value of the attribute, with a value of the attribute less and more than the average. The combined variability of the morphometric parameters of the PCA made it possible to identify 18 of its types.

The data obtained will complement and organize the existing information on the dimensional characteristics of the PCA, which is important for a better understanding of the area of neuromorphology under study, and can also be useful in modeling blood flow in the arterial circle of the brain.

Vertebral artery syndrome (Barre-Lieu) - symptoms and treatment

For chronic neck pain, surgical and pharmacological treatment methods are used, as well as various methods of traction therapy —spinal traction with the help of special devices (blocks, belts, rings) [12].

The effectiveness of manual therapy methods - soft techniques, post-isometric relaxation, muscle stretching - is still being studied. To this end, two studies were conducted in 2015. A meta-analysis by Chinese scientists showed that manual techniques are less effective in eliminating pain than cervical spine traction [13]. However, a study by Canadian scientists found that manual therapy becomes more effective when combined with another method of active treatment for acute and chronic neck pain. Also, manual techniques cope better with chronic pain than massage, and more effectively combat acute and subacute neck pain than drug treatment. However, due to side effects from taking medications, manual therapy is preferable. In terms of effectiveness, manual techniques are similar to mobilization of the cervical spine, but mobilization as a separate intervention does not reduce pain [14].

As for the non-drug treatment method of acupuncture , a 2021 meta-analysis showed its effectiveness over sham acupuncture (acupuncture of non-acupuncture points) and inactive treatment [15].

An undoubted effective method of treating the syndrome is physical exercise . Their effectiveness in relieving acute and chronic pain is supported by a 2005 review. In this case, it is worth focusing on stretching the cervical region, shoulder girdle and chest. And the combination of exercises with mobilization and manual techniques on the cervical spine helps reduce pain in the short and long term [16].

Surgical methods include :

puncture interbody fusion - combining and fixing several vertebrae to avoid their displacement;
fenestration - partial removal of the arch of the intervertebral disc;
autodermoplasty of intervertebral discs - replacement of the disc with one's own tissues.

During the operation, porous explants made of an alloy of titanium and nickel are implanted. Due to their porosity, bone tissue quickly grows in them. This makes the fixation strong and significantly reduces the patient’s period of incapacity for work and the neck being in a stationary position.

In addition to stabilizing operations of the cervical spine, other types of interventions are also performed:

decompressive-stabilizing - removal of compression with subsequent fixation of the spine;
decompressive-plastic (laminoplasty) - elimination of compression by enlarging the spinal canal while maintaining the integrity of the posterior elements of the vertebrae;
decompressive operations - removal of the intervertebral disc or its arch, compressing the artery, etc. [9].

There is considerable experience in reconstruction of vertebral arteries . The following methods are used:

transposition - displacement of the vertebral artery into the subclavian (common carotid);
angioplasty - dilation of a vessel using an expanding balloon;
Stenting is the expansion of a vessel by installing a stent.

If the first and second segments of the vertebral artery are simultaneously affected, bypass surgery is performed—creating a bypass at the level of the third segment [17].