Paper - The circle of Willis - An examination of 700 specimens (1905)

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Fawcett E. and Blachford JV. The circle of Willis - An examination of 700 specimens. (1905) J Anat. Physiol. 40(1): 63.2–70. PMID 17232664

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This historic 1905 paper by Fawcett described the anatomical variability in the circle of Willis, a specialised blood supply to the brain.



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The Circle of Willis - An Examination of 700 Specimens

Edward Fawcett
Edward Fawcett (1867-1942)

By Professor E. Fawcett, University College, Bristol, and Dr J. V. Blachford, Medical Superintendent, City and County Asylum, Bristol.


This investigation is another of the series of which we have from time to time published reports. The only other we know of on the same subject— that of Dr Windle—was published in the year 1888 in this Journal, and dealt with 200 specimens. Our results are derived from an analysis of more than three times that number of cases, and, taken along with these, should furnish statistics which may be considered as affording reliable averages.

Plan of Report

We first examined the circle with a view to finding how often it was complete, how often incomplete. When incomplete, we ascertained to what the non-completion was due.

Then we inquired into the symmetry or asymmetry, and, when asymmetry was found, determined its nature and the frequency with which it occurred. Having done this, we made and recorded observations on most of the arteries entering into the circle. The question of the influence of sex was considered, and is reported on.

The Circle of Willis Complete

In 700 specimens we found the circle complete 673 times, or 9671 per cent.

In 350 females it was complete 334 times, or 95-4 per cent.

In 350 males it was complete 339 times, or 96:8 per cent.

F. 334 350 95.4 per cent. Total 673 = 96.1 Per cont.
M. 339 96.8 per cent. 700

The Circle of Willis Incomplete

It was incomplete in 27 cases, or 3'8 per cent,

In 350 females it was incomplete 16 times, or 4°5 per cent., and in a similar number of males 11 times, or 3°1 per cent.

16 KF. =45 . 350 45 per cent. ) 27 , Total =, =3'8 per cent. mbar, J 100 "350

Nature of Incompleteness. This was due to:—

a. Absence of one or both posterior communicating arteries. b. Absence of the anterior communicating artery.

c. Absence of one or both Posterior Communicating Arteries is not a common condition according to our tables, not nearly socommon as Windle reports. When one artery is absent, it is more commonly the right one.

(a,) Absence of one Posterior Communicating Artery: The Right.

The right posterior communicating artery was absent 13 times—1‘8 per cent. ; in 350 females it was absent 5 times, or 1-4 per cent., and in 350 males it was absent 8 times, or 2:2 per cent.

5 . F. 350 > 14 per cent. 13 Total =~ =1°8 per cent. 8 9-9 700 M. 350 — ”

Windle’s tigures, quoted in Quain’s Anatomy, show absence of this artery in 4°5 per cent of cases.

(a,) The Left.

This artery is not so commonly absent as the right one, being absent only 10 times, as against 13, in 700 cases, or 14 per cent. It was, unlike the right one. more commonly absent in females. Thus, in 350 females it was absent 7 times, and in a corresponding number of males 3 times. It was therefore more than twice as often absent in females as in males.

F. J _9 per cent. )

350 10 3 ( Total 700 = 14 per cent.

350

According to Windle, it is absent in 6°5 per cent. of cases.

M ‘85, The Circle of Willis 65

(a,) Absence of both Posterior Communicating Arteries.

This is a very uncommon condition, occurring in our specimens but 3 times—each time in a female—-4 per cent. Windle found it as often as 15 per cent.

It is a little difficult to account for these wide ditferences between our results and those of Windle. Can there be a difference in the insane, or-is it due to the great difference in the number examined ?

b. Absence of the Anterior Communicating Artery.

This must be a very rare condition as we met with it only once, and that in a female. Windle notes several cases of absence of the anterior communicating artery, mostly due to fusion of the anterior cerebrals.

Symmetry of the Circle of Willis

The circle was symmetrical in 514 cases out of 700, or in 73:4 per cent. In 350 females it was symmetrical 248 times, and in a corresponding number of males 266 times.

248 F. 350= 70°8 per cent. 514

266 | Total 7007 73'4 per cent. M. 355 =76 »

It was complete and symmetrical 510 times out of 700, or 72°8 per cent.—244 times in the female, or 667, and 266 times in the male out of 350 cases, or 76 per cent.

pr 244 on - 959 = 667 per cent. 510 266 Total 708 = 72:8 per cent. M. —— =76 350 ”


Asymmetry of the Circle of Willis

This has many causes, thus :—

a, Variation in size between the two posterior communicating arteries. b. Absence of an artery in the circle.

c. Doubling of one anterior cerebral artery.

d, Abnormal origin of the posterior cerebral arteries, 66 Professor E. Fawcett and Dr J. V. Blachford

a. Variation in Size between the two Posterior Communicating Arteries.

(a,) The Right Posterior Communicating Artery was larger than the left in 87 cases out of 700, or 12°4 per cent. In 350 females, 45 times, or 12°8; in males, 42 times, or 12 per cent.

pr 2° =128 per cent. 350 87 Total —— = 12°4 per cent. M 42 = 700 350712 »

(a,) The Left Posterior Communicating Artery was larger than the right in 64 cases out of 700, or 9:1 per cent. In 350 females, it was the case 37 times, or 10°5 per cent.; and in 350 males, 27 showed this condition, or 7°7 per cent.

37 F. 355 =105 per cent. ) 64

Total

M ot 77 700 °350— ” It is evident that the right artery is more often, by its enlargement, the R.87 121 t. L. 64 gy PCD

= 9-1 per cent.

cause of asymmetry than the left one, thus

This tallies with Windle’s observation.

b. Absence of an Artery vn the Circle.

So far as our observations go, it is the posterior communicating alone which is concerned here.

(b,) The Right Posterior Communicating was absent 13 times out of 700,

or 18 per cent, and it was more often absent in males than females, thus :—

5 F. aa 350 Total 23 =1 ‘8 per cent. M 8 700 350

(b,) The Left Posterior Communicating Artery was absent 10 times in 700, or 1-4 per cent. It was twice as often absent in females as in males, thus :—

ol Total 5 — 07 1:4 per cent.

ao glo 8 The Circle of Willis 67

c. Doubling of one Anterior Cerebral Artery.

This is a rare cause of asymmetry, occurring only twice, or ‘28 per cent., once in a male and once in a female.

In the male it divided into two within the circle, and when without the two united.

In the female the two reunited within the circle. In both cases it was the right artery which was affected.

d. Asymmetry due tu Abnormal Origin of the Posterior Cerebral Arteries,

(d,) The Right Posterior Cerebral in 6 cases out of 700 arose from the corresponding internal carotid, four times in females, twice in males, thus :—

4 F. = =1 11 per cent. | ota 6 _.gs per cent.

x 700 M. 350 = 57, (d,) The Left Posterior Cerebral Artery arose in 4 cases out of 700 from the corresponding internal carotid, or ‘57 per cent., three times in females and once in males, thus :—

3 F. — ="7 per cent. 350 | otal a ='57 per cent. M1 =28 , 350

Asymmetry due to abnormal origin of the posterior cerebral arteries is evidently twice as common in the female as the male.

Female : Male :: 7 : 3


Observations on Some of the Arteries Entering into the Circle of Willis

The Anterior Communicating Artery.

This was only absent once, and that in a female. It was found to be single or double, or even treble, and it might be L-shaped.

It was single in 645 out of 700, or 92'1 per cent.; in 350 females it was single 315 times, or 90 per cent., and in the same number of males 330 times, or 97:1 per cent.

315


F, —~=90 per cent. 350 rota 648 Total —~ =92°1 per cent. M. =97T1 700 P

The artery was dowble in 51 cases out of 700, or 7:2 per cent.; was 32 times double in females, or 9°14 per cent., and 19 times double in males :—

F. 32 = 9-14 per cent. )

0 36 ~ Total 51 =7-2 per cent. M, 29 =5-7 S 700 "350 »

The artery was treble in one case only, and that case was a male. It occurred in a case in which a third anterior cerebral artery was present.

The artery was L-shuped (like the letter H laid horizontally). This was met with twice, both being in females.

The Third Anterior Cerebral Artery.

This artery arises as a rule from the anterior communicating artery.

It was present 23 times in 700, or 3:2 per cent.—Windle says 4°5 per cent. It seems to be much more common in the male than the female, for it was met with 19 times in 350 males, or 57 per cent., and only 4 times in the females, or 1-1 per cent.

F. 4 a1 per cent. )

. Total ka =3-2 per cent.

“3597 »

In one case, a male, the artery arose by two roots, one from each anterior cerebral. In two cases it arose directly from the left anterior cerebral artery, one in a male, the other in a female.

In another case, in which there were three anterior communicating arteries present, it arose from the middle one.

Nothing need further be said about the other arteries entering into the circle—they have already been fully dealt with; but it may be interesting to note that in two females the basilar artery, after giving off two posterior cerebrals, bifurcated into two posterior communicating arteries.

We may now sum up :— The circle is usually complete and symmetrical. If incomplete, that is due to absence of one or both posterior communicating arteries, or of the The Circle of Willis 69

anterior communicating—a very rare condition. Absence of the posterior communicating arteries is not so common as stated.

If asymmetrical, it may be due to absence of a posterior communicating artery, to doubling of an anterior cerebral artery, or abnormal origin of one posterior cerebral.

The anterior communicating artery is more often double in females than in males.

A third anterior cerebral artery is much more often present in males than in females.


Circle of Willis - Table

(to be formatted)

i \ Total. Percent-| Females. Percent- Males. Percent- | age. age. | age, | - Complete . . . 673 96°71 334 | 954 339 | 968 | ' Incomplete . . . 27 3°8 16 | 45 Wo BL ‘Symmetrical. . .| 514 73°4 248 =, =70°8 266 76 \ | Asymmetrical . . .! 186 26°5 102 | 29°1 84 2171 | Complete and symmetrical. 510. 72°8 244 667 266 76 |

BR. post. com. > left 87 12°4 45 128 = 42 12 Ly 4 > right . 64 9 37 | 10% 27 TT ,R. ,. 4, absent 1B 18 5 14 8 , 22 ‘TL. yy | 10 | 14 | 7 2 3 | 85 Both absent | 3 | “4 3 85 0 0

Both very small . | 5 | T 3 85 2 ‘57 | Ant. communicating absent. 1 14 | 1 28 0 0 i os ” single . | 645 92°1 315 90 330 94:2 1 yy ” double.) 51 | 72 32 9°1 19 57 "oy » treble 1 ‘14 0 0 1 28 ” 5 x-shaped . 2 28 2 ‘S57 0 0 R. P. cereb. from int. car, . 6 85 | 4 11 2 ‘57 ' iL. Py ” ” . 4, ‘57 3 7 1 "28 Both ' " . 1 14 1 28 Oo | 0 3rd ant. cerebral . . 23 32 | 11 Ie 19 | 57 700 350 350 Total. | Females. Males, | + 1 “en CIRCLE OF WILLIS.

2. 3

L.PCe


Ve \

1, Complete and 2. Right post. 3. Left post. com- symmetrical, 72°8 per communicating municating larger cent. larger than left, than right, 9°1 per

12°4 per cent. cent. 4. Ss. ] 6.

4. Right post. com- 5. Left post. 6. Both post. com- municating absent, communicating municating arteries 1°8 per cent. absent, 1°4 per absent, °4 per cent.

cent. 7. 8. 9

7. Right post. cereb. 8. Left post. 9. Both post. cere- from int. carotid, cereb, from int. brals from int. °85 per cent. carotid, ‘57 per earotids, *14 per cent.

cent, 10, i. ) 12.

10. Ant. com- 11, Ant. com- 12. Ant. communi- municating single, municatingdouble, cating treble, ‘14 per 92°1 per cent. 7°2 per cent. cent.


Fig. 1. The circle of Willis

The circle of Willis

B. — Basilar artery.

R.P.C. — Right post. cerebral artery.

L.P.C. — Lett post. cerebral artery.

R.P.Co. — Right post, communicating.

L.P.Co. — Lett post. communicating.

M.C. — Middle cerebral artery.

L.A.C. — Left anterior cerebral.

R.A.C. — Right anterior cerebral

A.Co. — Anterior communicating.


Cite this page: Hill, M.A. (2020, September 18) Embryology Paper - The circle of Willis - An examination of 700 specimens (1905). Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_circle_of_Willis_-_An_examination_of_700_specimens_(1905)

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