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Table 2 Frequencies of segmental variations using all 102 circles of Willis in comparison with the previous studies.

From: Are the distributions of variations of circle of Willis different in different populations? – Results of an anatomical study and review of literature

Variations

No

AcoA Aplasia

AcoA Hypoplasia

AcA Aplasia

AcA Hypoplasia

PcoA Aplasia

PcoA Hypoplasia

P1 Hypoplasia

P1 Aplasia

References

     

Uni

Bi

Uni

Bi

Uni

Bi

 

Alpers [14]

350

2%

3%

0

2%

0.6%

0

13.5%

9%

11%1

3.71%1

 

Fawcett [17]

700

0.14%

-

-

-

3.2%

0.4%

21.5%

0.7%

42%1

0.14%1

-

Riggs & Rupp [18]

994

 

27%

 

16%

  

21%

30%

16%

6%

-

Windle [21]

200

1.5%

-

-

-

11%

1.5%

21.5%

3.5%

10%1

2%1

 

El khamlichi Et al [22]

100

 

32%

 

4%

  

25%

35%

14%

1%

-

Fisher [23]

414

 

29%

 

13%

  

32%

49%

22%

7%

 

Lazorthes et al [25]

200

 

29.5%

 

7.5%

  

29.5%

40%

7.5%

4.5%

-

Puchades [36]

62

3.2%

6.4%

0.8%

6.4%

2.4%2

 

51.6%

 

11.3%

11.3%1

2.4%

Present study

102

1%

11%

-

1%

7%

3%

27%

33%

7%

-

 
  1. 1Fetal form of the posterior cerebral artery (P1 smaller than PcoA on the same side)
  2. 2The study has not indicated whether it has included bilateral hypoplasia or not.