• Users Online: 184
  • Print this page
  • Email this page


 
 
Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 71  |  Issue : 1  |  Page : 24-29

Morphometric analysis of normal and variant anatomy of posterior cerebral artery and the incidence of fetal posterior cerebral artery in Uttar Pradesh region: A computed tomography angiographic study


1 Department of Anatomy, King George's Medical University, Lucknow, Uttar Pradesh, India
2 Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India

Date of Submission03-Jul-2021
Date of Acceptance14-Oct-2021
Date of Web Publication17-Mar-2022

Correspondence Address:
Dr. Sarah Sko Sangma
Department of Anatomy, All India Institute of Medical Sciences, New Delhi
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jasi.jasi_115_21

Rights and Permissions
  Abstract 


Introduction: The aim is to study morphometric analysis of normal and variant anatomy of posterior cerebral artery (PCA) and incidence of fetal PCA (FPCA) in Uttar Pradesh region. The PCA and its cortical branches supply blood to the occipital lobe, inferomedial temporal lobe, and portions of posterior inferior parietal lobe. Fetal-type PCA is a common anatomic variation of PCA that is closely associated with intracranial aneurysm. The present study provides the description of PCA regarding its normal morphology, morphometry, and variations in Uttar Pradesh region. Material and Methods: The study evaluated 100 computed tomography angiograms. Results: Among arteries that displayed normal anatomy, mean diameter of PCA was observed to be 4.29 ± 0.74 mm on the right side and 2.47 ± 0.74 mm on the left side. Mean diameter in males and in females was found to be 2.48 ± 0.73 mm and 2.47 ± 0.74 mm, respectively. In 56.5% of cases, the diameters of P1 segment of PCAs ranged from 2.1 to 3 mm whereas >3 mm diameter was observed in 18.5% cases. Nineteen percent cases showed 1.1–2 mm. In 6% cases, hypoplasia (≤1 mm) of PCA was observed. FPCA was observed in 26% cases. Unilateral observed in 17% cases and bilateral in 9% cases and the difference was statistically significant (P < 0.000). Discussion and Conclusion: Anomalies of PCA may assume considerable significance in surgeries of head and neck, which require ligation of internal carotid and common carotid artery. Awareness of these anatomical variations described shall prove to be useful for any cerebrovascular procedures.

Keywords: Fetal posterior cerebral artery, variations, vertebrobasilar system


How to cite this article:
Pankaj AK, Sangma SS, Chopra J, Sehgal G. Morphometric analysis of normal and variant anatomy of posterior cerebral artery and the incidence of fetal posterior cerebral artery in Uttar Pradesh region: A computed tomography angiographic study. J Anat Soc India 2022;71:24-9

How to cite this URL:
Pankaj AK, Sangma SS, Chopra J, Sehgal G. Morphometric analysis of normal and variant anatomy of posterior cerebral artery and the incidence of fetal posterior cerebral artery in Uttar Pradesh region: A computed tomography angiographic study. J Anat Soc India [serial online] 2022 [cited 2022 Jul 3];71:24-9. Available from: https://www.jasi.org.in/text.asp?2022/71/1/24/339871




  Introduction Top


Anterior and posterior circulations provide the primary blood circulation of the brain. Anterior circulation comprises internal carotid artery and its branches. Posterior circulation comprises the vertebral arteries, its main branch posterior inferior cerebellar arteries, the basilar artery (BA) and its branches anterior inferior cerebellar arteries, superior cerebellar arteries, and terminal branch posterior cerebral artery (PCA)[1] [Figure 1]. Most adult humans have the classic vascular anatomy in which both left and right PCAs originate from the BA and are part of the vertebrobasilar system or posterior circulation. PCA is divided into four segments, P1 to P4. The P1 segment is between the termination of the BA and the posterior communicating artery (PCOM)[2] [Figure 1]. An anatomic variant of the PCA, known as fetal-type or fetal PCA (FPCA), has been detected by anatomic,[3] and angiographic,[4],[5],[6] studies in 11% to 46% of adult humans, either unilaterally or bilaterally. FPCA is called a full FPCA if the P1 segment is not visualized on computed tomography angiography, magnetic resonance angiography [Figure 2] or after injection of contrast into the vertebral artery; a partial FPCA if the P1 segment is smaller than the PCOMA [Figure 3] or an intermediate FPCA if the P1 segment is as large as the PCOMA[7] [Figure 4].
Figure 1: Schematic diagram showing normal vertebrobasilar system and circle of Willis, where P1: P1 segment of posterior cerebral artery, P2: P2 segment of posterior cerebral artery

Click here to view
Figure 2: Schematic diagram showing full fetal posterior cerebral artery, blue arrow

Click here to view
Figure 3: Schematic diagram showing partial fetal posterior cerebral artery

Click here to view
Figure 4: Schematic diagram showing intermediate fetal posterior cerebral artery

Click here to view


Various authors have studied the morphometry of the PCA in different populations and the results have been seen to vary in different races. In the present study, we have made an attempt to make a normal morphometry of P1 segment of PCA and observe the variations associated with it such as hypoplasia and fenestration. A solid understanding of the pathophysiology of a PCA stroke as well as the syndrome relating to it requires adequate knowledge of the structures and vascular anatomy of the brain.


  Material and Methods Top


Ethical clearance

Approval for this observational, descriptive, cross-sectional study was obtained from Ethical review board of University with the Helsinki Declaration of 1975, as revised in 2000.

Study design

The present study is an observational, descriptive, cross-sectional, study.

Subjects

The study evaluated 100 computed tomography (CT) angiograms of patients of all age groups of either sex that visited the Department of Radiodiagnosis between September 2016 and August 2017 for undergoing head-and-neck CT angiography.

Duration of study

September 2016 to August 2017.

Inclusion criteria

  • All age groups
  • Patients undergoing brain angiography, craniovertebral junction angiography
  • Willing to participate in the study.


Exclusion criteria

  • Refusal to participate in the study
  • Pregnancy
  • Allergy to iodine
  • Renal insufficiency
  • Uninterruptable scans
  • History of head trauma, cerebral surgery, vasculitis syndrome, vertebrobasilar dissection or near-complete occlusion and space-occupying intracranial lesions likely to distort the vascular anatomy.


Preprocedure precautions

  • Patients were enquired to rule out the presence of any drug allergy to avoid the occurrence of any untoward anaphylactic reaction during the procedure
  • They were asked to come empty stomach
  • They were advised to drink only water just before the procedure
  • Blood urea and creatinine levels were evaluated before procedure.


Computed tomography angiography protocol

CT angiography was performed on a 64-slice multidetector computed tomography (MDCT) scanner (BRILLIANCE CT, Philips medical system, Netherland, B. V.5684 PC Best. The Netherlands). CT angiography of all patients was done after overnight fasting. Patients were trained for the breath holding method which was required during the procedure.

Procedure

CT angiography was performed after receiving a written informed consent from the concerned subject. The patient was positioned supine and head immobilized by adhesive strap. The images were acquired on a 64-slice MDCT. The area from C3 vertebra to the vertex was scanned. Plain CT followed by CT angiography was performed. 80–100 ml of nonionic contrast medium was injected at the rate of 5 ml/s followed by saline of flush 40 ml through the antecubital vein with 18 gauge cannula using power injector. The time of delay was chosen by bolus tracking. Common carotid artery was monitored in real-time with low-dose dynamic scanning at C5 vertebra. The diagnostic scan was manually started once contrast reached the common carotid artery. Source images thus obtained were transferred to the workstation dedicated to the scanner where the processing was done. The final postprocessed images along with the axial slices were used for analysis and reporting.

Image analysis

Images were processed on an extended brilliance workspace version 4.0. CT image interpretation was done using various techniques such as multiplanar reconstructions, maximum intensity projection, and volume-rendered technique. Axial source images [Figure 5] and [Figure 6] and three-dimensional reconstructed images were helpful in evaluating complex vascular anatomy. Interpretation was done by radiologists and anatomists. Image analysis was done for both right and left P1 segment of PCA for appreciating normal anatomy and variations such as:
Figure 5: Axial source image of computed tomography angiography of brain showing measurement of basilar artery

Click here to view
Figure 6: Axial source image of computed tomography angiography of brain showing measurement of normal posterior communicating artery and P1 segment

Click here to view


Figure 7: Three-dimensional volume-rendered image of computed tomography angiography of brain showing fenestration of left P1 segment

Click here to view
Figure 8: Axial source image of computed tomography angiography of brain showing hypoplasia of P1 segment and partial F posterior cerebral artery on the right side

Click here to view
Figure 9: Three-dimensional volume-rendered image of computed tomography angiography of brain showing partial F posterior cerebral artery on left side

Click here to view


Data analysis

The statistical analysis was carried out on SPSS (Statistical Package for the Social Sciences) 16.0 version (Chicago, Illinois, Inc., USA). The results were presented in frequencies and percentages. Chi-square test was used for the assessment of associations. One-way analysis of variance was used to compare the mean diameters of arteries among age groups.


  Results Top


One hundred (100) patients were included in the study (males = 52 and females = 48). Age ranged from 21 to 80 years with mean age = 48.86 ± 16.73 years.

The analysis of images revealed 100 P1 segments of PCAs on both right and left sides. PCA hypoplasia was seen in 6% of cases and fenestrated PCA was seen in 1% of cases. Among the arteries that displayed normal anatomy, the mean diameter of PCA was observed to be 4.29 ± 0.74 mm on the right side and 2.47 ± 0.74 mm on the left side. Mean diameter in males and in females was found to be 2.48 ± 0.73 mm and 2.47 ± 0.74 mm, respectively. The difference in mean diameter with laterality and gender was statistically insignificant.

In 56.5% of cases, the diameters of P1 segment of PCAs ranged from 2.1 to 3 mm whereas >3 mm diameter was observed in 18.5% of cases. In 19% of cases, it was observed to be 1.1–2 mm. In 6% cases, hypoplasia (≤1 mm) of PCA was observed [Table 1] and [Figure 10].
Table 1: Prevalence of different range of diameters of P1

Click here to view
Figure 10: Bar diagram showing prevalence of different range of diameters of P1 segment

Click here to view


The mean diameter of P1 segment of PCA did not show any consistent relation with age groups. It was maximum in <20-year age group then it decreased in 20–40-year age group. In 41–60-year age group, it was wider as compared to 20–40-year age group but lesser than <20-year age group. The diameter then again decreased in 61–80-year age group and was minimum among all values observed in various age groups. The difference in mean diameter among different age groups was statistically insignificant [Table 2] and [Figure 11].
Table 2: Mean diameter of P1 segment of posterior cerebral artery in different age groups

Click here to view
Figure 11: Bar diagram showing mean diameter of P1 segment in different age groups

Click here to view


Variations of partial FPCA: In the present study, FPCA was observed as partial type in 26% cases. Unilateral PCA was observed in 17% cases [Figure 12] and bilateral FPCA in 9% cases [Figure 12] and the difference was statistically significant (P < 0.000). The prevalence of unilateral FPCA was found to be more common in males (11%) as compared to females (6%) and on the right side (11%) as compared to the left (6%). Bilateral FPCA was observed to be more common in males than females [Table 3] and [Figure 12].
Table 3: Prevalence of fetal posterior cerebral artery

Click here to view
Figure 12: Bar diagram showing prevalence of partial fetal posterior cerebral artery

Click here to view



  Discussion Top


PCA was observed in 100 cases. The mean diameter of P1 segment of PCA was observed to be larger on the right side (4.29 ± 0.74 mm) as compared to the left side (2.47 ± 0.74 mm). Our findings were similar with that of Patel et al. who also found right PCA (2.53 mm) to be larger than left PCA (2.49 mm).[3] Similarly, Akgun et al. also found right P1 to be larger (2.56 ± 0.43 mm) as compared to the left side (2.43 ± 0.34 mm).[5]

The diameters measured by these authors were not in concurrence with the present study. The difference in measurement could be due to different modalities used by the authors. The readings noted by Pai et al. were comparatively lesser though they also reported that right P1 (2.76 mm) was marginally wider than left (2.5 mm).[8] In a cadaveric study done in 30 fresh cadaveric brain specimens, Canaz et al. found that in 18 (60%) brains, right PCA was wider than left PCA.[9]

We also noted that mean diameter of P1 was marginally larger in males (2.48 ± 0.73 mm) as compared to females (2.47 ± 0.74 mm), but the difference among gender groups was statistically insignificant. Rai et al. observed that the mean diameter was equal in both genders (2.2 ± 0.4 mm).[10] Their findings were not in parallel to the present study.

PCA occlusion or blockage may result in many clinical conditions such as thalamic syndrome and Weber's syndrome, therefore, thorough knowledge of the morphometry will help clinicians to deal with lesions of posterior circulation.[3] It will also enhance knowledge to radiologists and surgeons for proper diagnosis and treatment of the pathology of PCA.

In the present study, diameter of P1 ranged from 1.1 to 4 mm. In majority of arteries (56.5%), it ranged from 2.1 to 3 mm, so we can infer that normal range of diameter of P1 in the UP region of North India is 2.1–3 mm. Patel et al. found the range of diameter of PCA to be 2.07–3.6 mm in Gujurat population.[3] The range of diameter of PCA was found to be 0.3 mm to 3.8 mm in a study of 56 formalin fixed brains done by Saha et al.[11]

The knowledge about range of normal diameter of arteries is important to acknowledge hypolasia and/or dilatation to avoid any misinterpretation of the clinical condition. Hypoplastic arteries may alter the hemodynamic balance and cause intracranial stroke. Dilated arteries may be a risk factor for development of aneurysms.

The mean diameter of P1 segment of PCA did not show any consistent relation with age groups in the present study. However, Rai et al. found a significant increase in arterial caliber of PCA in patients aged ≥60 years compared with those aged 40–59 years which was not in congruence with the present study.[10]

The posterior circulation measurements showed an increase in arterial caliber with age. This baseline information may be useful in planning neurovascular procedures and endovascular device development.[10]

Along the course of our study, various types of variant forms were encountered which included hypoplasia and fenestration of P1 segment of PCA.

P1 segment hypoplasia was seen in 6% of cases and fenestration was seen in 1% of cases. Gunnal et al. found hypoplastic P1 segment in 5.29% and fenestration in 1.17%.[12] Akgun et al. also reported fenestrated PCA in 1 case on the left side.[5]

Fenestration is the duplication of a portion of an artery into two separate and parallel channels which rejoin distally.[5] They are rare anomalies which results from incomplete fusion of primitive embryologic vessels. They may be associated with aneurysms, arteriovenous malformations, and venous angiomas.[13]

FPCA was observed in 26% of cases which was of partial FPCA type. Unilateral PCA was observed in 17% of cases and bilateral FPCA in 9% of cases. The present findings were similar to the findings of He and Wan who found unilateral FPCA in 25% and bilateral in 7.4%.[14] Akgun et al. found that isolated FPCA was in 3 cases.[5] Pai et al. found in 10% cases.[8] Lambert et al. reported 2 cases of concurrent inferior cerebellar arteries (ICA)-PCA territory infarction in the setting of a unilateral FPCA.[7]

Blood supply of the PCA on the fetal type side is exclusively from the ipsilateral ICA, or from both the ipsilateral ICA and the BA, but predominantly from the ICA. Under normal circumstances, intracranial blood supply on both sides simultaneously relies on the cervical and vertebral basilar system, and the cerebral blood flow pressure remains similar between both sides. In the case of fetal type, the blood flow of the ICA and vertebral basilar system is unbalanced, leading to a series of hemodynamic changes in circle of Willis components.[11]

Emboli can move up the ICA, enter and occlude the FPCA or its branches, and result in a paradoxical PCA territory infarction with or without occlusion of other ICA branches.[10]


  Conclusion Top


These variations are probably genetically determined and may alter the occurrence, severity of symptoms, treatment options, and recovery from certain cerebrovascular disorders, namely stroke and aneurysms. The present study was focused to provide a nomogram for morphometry of PCA and presence of its normal and anatomical variants. A detailed knowledge of the normal vascular anatomy and its variants is useful to surgeons in planning shunt operations, keeps away inadvertent vascular traumas during surgeries, and avoids potential diagnostic pitfalls.

Acknowledgments

The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Standring S, Anand N, Jawaheer G, Tubbs RS, Birch R, Smith AL, et al. Gray's Anatomy. Elsevier; 41st edition, London, UK: 2016.  Back to cited text no. 1
    
2.
Kuybu O, Dossani RH. Posterior Cerebral Artery Stroke. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2018: https://www.ncbi.nlm.nih.gov/books/NBK532296/. [Last accessed on 2021 Sep 29].  Back to cited text no. 2
    
3.
Patel SK, Zalavadiya DI, Patel SV, Vaniya VH. Morphometry of posterior cerebral artery. International Journal of Anatomy, Radiology and Surgery. 2017 Oct ;6(4): AO35-AO37.  Back to cited text no. 3
    
4.
Bulsara KR, Zomorodi A, Provenzale JM. Anatomic variant of the posterior cerebral artery. AJR Am J Roentgenol 2007;188:W395.  Back to cited text no. 4
    
5.
Akgun V, Battal B, Bozkurt Y, Oz O, Hamcan S, Sari S, et al. Normal anatomical features and variations of the vertebrobasilar circulation and its branches: An analysis with 64-detector row CT and 3T MR angiographies. ScientificWorldJournal 2013;2013:620162.  Back to cited text no. 5
    
6.
Kovač JD, Stanković A, Stanković D, Kovač B, Šaranović D. Intracranial arterial variations: A comprehensive evaluation using CT angiography. Med Sci Monit 2014;20:420-7.  Back to cited text no. 6
    
7.
Lambert SL, Williams FJ, Oganisyan ZZ, Branch LA, Mader EC. Fetal-Type Variants of the Posterior Cerebral Artery and Concurrent Infarction in the Major Arterial Territories of the Cerebral Hemisphere. Journal of Investigative Medicine High Impact Case Reports; 2016:1-7.  Back to cited text no. 7
    
8.
Pai BS, Varma RG, Kulkarni RN, Nirmala S, Manjunath LC, Rakshith S. Microsurgical anatomy of the posterior circulation. Neurol India 2007;55:31-41.  Back to cited text no. 8
[PUBMED]  [Full text]  
9.
Canaz H, Arslan M, Hacioglu H, Tokmak M, Canaz G, Cavdar S. Morphometric analysis of arteries of Willis polygon. Rom Neurosurg 2018;32:56-64.  Back to cited text no. 9
    
10.
Rai AT, Rodgers D, Williams EA, Hogg JP. Dimensions of the posterior cerebral circulation: An analysis based on advanced non-invasive imaging. J Neurointerv Surg 2013;5:597-600.  Back to cited text no. 10
    
11.
Saha A, Sarkar A, Mandal S. A cadaveric study of bilateral configuration of posterior bifurcation of posterior communicating artery in Indian population. J Clin Diagn Res 2015;9:C01-4.  Back to cited text no. 11
    
12.
Gunnal SA, Farooqui MS, Wabale RN. Study of posterior cerebral artery in human cadaveric brain. Anat Res Int 2015;2015:681903.  Back to cited text no. 12
    
13.
Osborn RE, Kirk G. Cerebral arterial fenestration. Comput Radiol 1987;11:141-5.  Back to cited text no. 13
    
14.
He Z. Wan Y. Is fetaltype posterior cerebral artery a risk factor for intracranial aneurysm as analyzed by multislice CT angiography. Exp Ther Med 2018;15:838-46.  Back to cited text no. 14
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

Top
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
Abstract
Introduction
Material and Methods
Results
Discussion
Conclusion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed430    
    Printed16    
    Emailed0    
    PDF Downloaded97    
    Comments [Add]    

Recommend this journal