Table 1.
Summary of microvascular anatomic investigations of the posterior vascularization and reported incidence of AOP associated or not with other variants in the circle of Willis.
| Author, year | Number of brain specimens | Average number of TPAs/brain | Frequency of AOP (%) | P1 segment (hypoplastic or absent) |
|---|---|---|---|---|
| Grochowski, Maciejewski, 2017 [9] | 13 | 5.8 | 0% | Not reported |
| Djulejić, 2015 [10] | 12–16 | 2.2 | 0% | Not reported |
| Griessenauer, 2013 [11] | 25 | Not available | 12% | 0% (specified) |
| Kocaeli, 2013 [12] | 34 | 8.5 | 11,7% | Not reported |
| Parraga, 2011 | 35 | 6 | Not reported | Not reported |
| Park, 2010 [13] | 26 (158) | 7,2 | 11,5% | Not reported |
| Kaya, 2010 [14] | 14 | 6.8 | 11,7 | Not reported |
| Pai, 2007 | 25 | 4 | Not reported | Not reported |
| Uz, 2007 [15] | 15 | 4 | 7% | Not reported |
| Cosson, 2003 | 12 | 7.5 | Not reported | Not reported |
| Rassi, 1992 | 30 | 3.2 | Not reported | Not reported |
| Caruso, 1990 | 50 | 8.2 | Not reported | Not reported |
| Marinkovic, 1986 [16] | 33 | 4 | Not reported | Not reported |
| Pedroza, 1986 [17] | 28 | 1-5 | 10,7% | Not reported |
| Lang, Bruner, 1978 | 50 | Not available | 8% | Not reported |
| Zeal, Rhoton, 1978 | 25 | 5.4 | Not reported | Not reported |
| Saeki, 1977 | 50 | 8.2 | 8% | hypoplastic P1 |