1341
Microanatomy and Possible Clinical
Significance of Anastomoses Among
Hypothalamic Arteries
Slobodan V. Marinkovic, MD, Milan M. Milisavljevic, MD, and Zorica D. Marinkovic, MD
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We examined anastomoses among the hypothalamic arteries in 14 human brains using an
injection technique, microdissection, and a stereoscopic microscope. Five to 22 anastomoses
(mean 10.1) were found in all 14 brains on each side, varying from 20 to 280 (mean 71) /*m in
diameter and from 0.1 to 5.3 (mean 1.52) mm long. A single hypothalamic artery may be
connected to other vessels by one to 10 anastomoses. The anastomoses were channel-like or
plexiform; both types may be ipsilateral or right-left. They connected the hypothalamic arteries
"end-to-end," "end-to-side," and "side-to-side." The interconnected arteries ranged from 30
to 1,900 (mean 148) /xm in diameter. Anastomoses were most frequent among the commissural
arteries and in the distribution of the superior hypophyseal arteries and the tuberoinfundibular
branches of the posterior communicating artery. The largest anastomoses were found among
the tuberoinfundibular branches of the posterior communicating and internal carotid arteries,
as well as among the premamillary arteries and the mamillary branches. We discuss the
neurologic, neuroendocrinologic, and neurosurgical significance of the described anastomoses.
{Stroke 1989;20:1341-1352)
M
ost previous studies dealing with the anatomic examination of the hypothalamic
arteries1-8 have only mentioned the presence of a "circuminfundibular plexus" without giving any information about the frequency, number,
or size of the anastomoses within the plexus.
Others9-12 drew special attention only to capillary
connections and not to arterial anastomoses in the
hypothalamopituitary region. Hence, there is an
obvious lack of data concerning anastomoses among
the hypothalamic arteries. These anastomoses could
be of great neurologic, neuroendocrinologic, and
neurosurgical significance for several reasons. Neurologists need information about the vascular pattern in the hypothalamic region to predict the risk of
ischemic damage in that region following thromboembolic events and other pathologic processes that
may compromise local blood flow; neurosurgeons,
who perform delicate operations in the perichiasmatic, tuberal, and interpeduncular regions, must
have detailed information on the hypothalamic
microvasculature; and, finally, ongoing presence of
From the Institute of Anatomy (S.V.M., M.M.M.) and the
Departments of Neurology and Psychiatry (Z.D.M.), University
Medical School, Belgrade, Yugoslavia.
Address for correspondence: Dr. Slobodan V. Marinkovic,
MD, Institute of Anatomy, University Medical School, Dr.
Subotica 4/2, 11000 Belgrade, Yugoslavia.
Received October 17, 1988; accepted May 17, 1989.
these anastomoses could be a way of locally regulating neurosecretory activity.
Subjects and Methods
We examined 28 sets of hypothalamic arteries in
14 brains of individuals aged 28-67 years. Each
brain was carefully removed from the skull after
cutting the internal carotid arteries (ICAs), optic
nerves, and pituitary stalk as low as possible.
Plastic catheters were placed in the basilar artery
and in both ICAs. In most instances, the main stems
of the middle cerebral and anterior choroidal arteries were ligated, as were the distal segments of the
anterior cerebral arteries (ACAs) and the posterior
cerebral arteries (PCAs). Thereafter, the components of the circle of Willis were irrigated with
isotonic saline and injected with a solution of gelatin, 10% India ink, and formaldehyde. The injected
brains were then fixed in 10% formaldehyde solution for 3 weeks. The arteries of the fixed brains
were dissected under a stereomicroscope, using
neurosurgical microinstruments, while the brains
were immersed in water.
We microdissected several thousand hypothalamic vessels from 14 brains, drew the microvasculature of each brain, and identified each hypothalamic vessel. The 10 best-prepared brains were
used for photographs, measurements, and statistical analysis. All photographs were taken parallel
1342
Stroke Vol 20, No 10, October 1989
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FIGURE 1. Summarized drawing of anastomoses (black) among a: right (I), left (2), anterior median (3), and posterior
median (4) commissural arteries; b: median preoptic branch (5) of anterior communicating artery (6) and anterior cerebral
artery (ACAJ (7); c: two preoptic arteries (8) arising from ACA; d: preoptic artery and commissural arteries; e: preoptic artery
(8) and optic branch (9) of ACA; f: preoptic artery (8) and supraoptic artery (10); g: supraoptic artery (10) and optic branch
(11) of internal carotid artery (ICA) (12); h: right (13) and left (13') superior hypophyseal arteries (SHAs); i: superior (13) and
inferior hypophyseal arteries (cut);y. two ipsilateral SHAs (13); k: collateral branches of same SHA (13'); 1: SHA (13) and optic
branch (9); m: SHA (13') and tuberoinfundibular artery (14) arising from ICA (12); n: SHA (13) and tuberoinfundibular artery
(15) arising from posterior communicating artery (PCoA) (16); o: two tuberoinfundibular branches (14) of ICA; p:
tuberoinfundibular branch (14) and optic branch (11) of ICA; q: tuberoinfundibular branch (14) and PCoA (16); r:
tuberoinfundibular branch (14) of ICA and tuberoinfundibular branch (15) of PCoA; s: tuberoinfundibular artery (15) and optic
branch (11); t: tuberoinfundibular artery (15) and PCoA (16); u: collateral branches of tuberoinfundibular artery (15); v: two
ipsilateral tuberoinfundibular arteries (15); w: two contralateral tuberoinfundibular arteries; x: tuberoinfundibular artery (15)
and mamillary branch (17) of PCoA; y: tuberoinfundibular artery (15) and mamillary branch (18) of PCA (19); z: two mamillary
branches (17) of PCoA; a,: mamillary branch (17) of PCoA and mamillary branch (18) of posterior cerebral artery (PCA); bj:
mamillary branch (18) and perforating branch (20)ofPCA (19); c^ mamillary branch (17) and premamillary artery (21); d,:
premamillary artery (21) and PCoA; e ^ premamillary artery (21) and peduncular branch (22) of PCA; f,: premamillary artery
(21) and anterior choroidal artery (23). 24, basilar artery; 25, left cms cerebri; 26, left mamillary body; 27, pituitary stalk (cut);
28, optic chiasm; 29, left optic nerve.
Marinkovic et al Hypothalamic Arterial Anastomoses
FIGURE 2.
1343
Anastomotic
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plexus (1) formed by branches
of right (2), left (3), anterior
median (4), and posterior
median (5) commissural arteries. Anterior median commissural artery arises from
median preoptic artery, which
is connected (arrow) to anterior cerebral artery (6). Compare with Figure 1, a and b. 7,
anterior
communicating
artery; 8, left anterior cerebral artery; 9, preoptic arteries; 10, supraoptic artery; 11,
left optic tract. Basal and
slightly caudal view after displacing optic nerves and optic
chiasm ventrally. x9.
to the longitudinal (rostrocaudal) or transverse
(right-left) plane of the hypothalamus. Measurements were made using an ocular micrometer. The
caliber of the vessels was expressed in microns
and the length in millimeters. The mean and
standard deviation were calculated.
Results
The hypothalamus is supplied by several groups
of arteries. Thus, the rostral part of the hypothalamus (the preoptic area and a part of the supraoptic
region) is mainly nourished by the commissural,
preoptic, and supraoptic vessels that usually arise
from the ACA and anterior communicating artery.
The intermediate part of the hypothalamus (the
supraoptic and tuberal regions and the rostral portion of the lateral hypothalamic area) is mainly
supplied by the superior hypophyseal and tuberoinfundibular branches of the ICA and the posterior
communicating artery (PCoA). The caudal part of
the hypothalamus (the mamillary region and the
caudal part of the lateral hypothalamic area) is
nourished by the premamillary and mamillary
branches of the PCoA as well as the mamillary
uram^nea Oi me rv^rt ^rigure L).
We examined the anastomoses among all the
mentioned vessels and found them to be present in
all 14 brains studied. The number of anastomoses
varied from five to 22 (mean±SD 10.1±4.3) on
either side of the brain and from 11 to 40 on both
sides. A single hypothalamic artery may be
involved in as many as 10 anastomoses. The
anastomoses for each hypothalamic artery are as
follows.
Four commissural arteries may be distinguished
(Figure 1): the anterior median commissural artery,
arising from the anterior communicating artery or
one of its branches, including the median preoptic
arteries (Figure 1); the right and left commissural
arteries, originating from the ACA or the preoptic
arteries; and the posterior median commissural
artery, arising from the right or left superior hypophyseal artery (SHA). The anastomoses among the
commissural arteries themselves formed a delicate
plexus in the middle of the lamina terminalis (Figures la and 2), and anastomoses were also observed
among the commissural arteries and their neighboring arteries (Table 1).
There were usually three groups of preoptic arteries (Figure 1). The median preoptic arteries arose
from the anterior communicating artery or one of its
larger branches, while the medial and lateral preoptic arteries originated from the right and left ACAs.
Anastomoses (Table 1) were found among the preoptic arteries as well as among the commissural
arteries (Figure la and d), other preoptic vessels
(Figure lc), the optic branch of the ACA (Figure
le), the supraoptic artery (Figure If), and the SHA
(Figure Id). In one brain we also found an anastomosis between a median preoptic artery and the
main stem of the ACA (Figures lb and 2) with a
channel diameter of 210 /xm.
The supraoptic artery was connected to the preoptic arteries (Figure If, Table 1), to the perforating
branch of the ACA, to the optic branch of the ICA
(Figure lg), and to the tuberoinfundibular branch of
the ICA. Anastomoses were usually located close
to the lateral part of the optic chiasm (Figure 1).
One or two SHAs were present, arising from the
ICA 95% of the time (Figure 3) or from the PCoA
5% of the time. Among various anastomoses that
involved the SHA, we found one to three vessels
connecting the collateral branches of the SHA (Figures Ik and 3) in 20% (four hemispheres). These
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Commissural
Preoptic
7(W
5%
1
40
0.7
120, 130
b
c
d
e
a
Mamillary branch of PCoA
e
d
e
Tuberoinfundibular branch of PCoA
a
b
c
d
e
PCoA
a
b
c
d
c
b
110, 100
0.6
5%
1
70
10%
1
40,60
0.7, 0.9
100, 130
Supraoptic
branch of
ACA
a
30%
a
i\)/o
1-2 (1.3)
b
1-2(1.1)
c
20-60 (40)
25-110(69)
d
0.4-2.3 (1.0)
0.3-3.5 (1.5)
30-250(114)
e
50-210 (101)
Optic branch of ICA
a
b
c
d
e
Tuberoinfundibular branch of ICA
„
Commissural
40%
a
90%
b
—
1-2 (1.6)
20-110(53)
c
20-60 (38)
0.3-3.9 (1.7)
d
—
70-250(118)
e
80-130 (99)
Preoptic
a
40%
25%
b
1-2 (1.6)
1-2 (1.2)
20-60 (36)
c
20-110(53)
—
d
0.3-3.9 (1.7)
70-120 (92)
e
70-250(118)
Supraoptic branch of ACA
10%
a
1
b
40,60
c
d
0.7, 0.9
100, 130
e
Optic branch of ACA
5%
1
b
c
30
_
d
—
e
SHA
Artery
20%
1-2 (1.5)
60-130 (93)
1.3-3.2 (2.0)
65-200 (142)
—
5%
1
30
Optic
branch of ACA
20%
1-2 (1.4)
50-110(68)
0.9-3.7 (1.6)
60-210(115)
10%
1
100, 180
0.9, 3.1
120, 230
45%
1-2 (1.4)
20-200 (69)
0.2-2.9 (1.6)
50-280 (112)
10%
1
120, 130
1.8, 2.1
110, 150
5%
1
70
0.6
110, 100
Optic
branch of ICA
40%
1-3 (1.5)
20-200 (74)
0.3-5.3 (1.9)
30-250(118)
10%
1
120, 130
1.8, 2.1
110, 150
1
40-130 (85)
0.7-1.2 (0.8)
—
1-2 (1.5)
60-130 (93)
1.3-3.2 (2.0)
65-200 (142)
30%
1-2 (1.3)
25-110(69)
0.3-3.5 (1.5)
30-250 (114)
70%
1-2(1.1)
20-60 (40)
0.4-2.3 (1.0)
50-210 (101)
SHA
TABLE 1. Anastomoses Among Hypothalamic Arteries in Humans
10%
1
100, 180
0.9, 3.1
120, 230
20%
25%
1-3 (1.4)
30-110 (54)
0.7-2.4 (1.2)
90-200 (120)
10%
1
70, 180
2.4, 3.9
110, 1,600
30%
1-2 (1.5)
40-200 (105)
0.6-3.1 (1.8)
90-280 (170)
5%
1
90
4.1
120, 1,500
45%
1-2 (1.1)
20-110(55)
0.3-1.6 (1.0)
50-200(110)
30%
1-2 (1.5)
40-200 (105)
0.6-3.1 (1.8)
90-280 (170)
1
100
1.6
110, 120
5%
1-2 (1.4)
50-110 (68)
0.9-3.7 (1.6)
60-210 (115)
45%
1-2 (1.4)
20-200 (69)
0.2-2.9 (1.6)
50-280 (112)
40%
1-3 (1.5)
20-200 (74)
0.3-5.3 (1.9)
30-250 (118)
1
40
0.7
120, 130
5%
TuberoTuberoinfundibular
infundibular
branch of ICA branch of PCoA
Artery
10%
1
70, 180
2.4, 3.9
110, 1,600
5%
1
90
4.1
120, 1,500
PCoA
10%
1,2
110, 110
0.2, 1.7
110, 120
45%
1-2 (1.1)
20-110(55)
0.3-1.6 (1.0)
50-200 (110)
Mamillary
branch of
PCoA
25%
1
20-130 (76)
0.7-3.9 (2.1)
90-220 (150)
15%
1
20-100 (53)
0.7-1.7(1.1)
80-130 (100)
Mamillary
branch of
PCA
5%
1
80
3.4
120, 700
5%
1
90
1.2
120, 670
5%
1
90
0.6
140, 520
Premamillary
5%
1
150
0.4
170, 220
Interpeduncular
branch of PCA
Peduncular
branch
of PCA
8
1
3
B"
Marinkovic et al Hypothalamic Arterial Anastomoses
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1345
vessels connected the optic branches (Figures Ik
and 3), the tuberoinfundibular branches, or both;
the anastomotic vessels were 30-90 (mean±SD
51±20) fim wide and 0.2-2.1 (mean±SD 1.2±0.6)
mm long. The interconnected branches were 50-170
(mean±SD 93±38) /im wide.
The two ipsilateral SHAs were connected in
15% of the hemispheres (Table 1, Figure lj). The
anastomoses between the right and left SHAs
(Figures lh and 4) were present in all 14 brains
examined and connected the branches descending
along the pituitary stalk, the optic vessels, the
tuberoinfundibular branches, and the posterior
median commissural arteries. There were one to
four anastomoses, occasionally forming a small
network, located just rostral to the proximal pituitary stalk, that is, between it and the optic chiasm
(Figures lh and 4). The anastomoses were 20-180
(mean±SD 68+44)/urn wide and 0.1-1.7 (mean±SD
0.6±0.4) mm long. The interconnected branches
were 90-280 (mean±SD 161 ±51) fim wide. The
remaining anastomoses (Table 1) were observed
among the SHA and the commissural arteries
(Figures la and 2), the preoptic arteries (Figure
Id), the optic branch of the ACA (Figure 11), the
optic and/or tuberoinfundibular branch of the ICA
(Figures lm and 5), and/or the tuberoinfundibular
branch of the PCoA (Figures In and 6). The
anastomoses were usually observed at the level of
the optic chiasm and the proximal pituitary stalk
(Figure 1) or between the stalk and the optic tract
(Figures 5 and 6).
The middle hypophyseal arteries, also called the
loral or trabecular arteries, connect the SHA and
the inferior hypophyseal artery. Since the middle
hypophyseal arteries were cut in all 14 brains examined (Figures li and 3), we did not examine these
anastomotic channels in this study.
In two hemispheres (10%), we found anastomotic
channels 30-150 /xm wide and 0.4-2.3 mm long
among the collateral branches of the tuberoinfundibular branch of the ICA. The two ipsilateral tuberoinfundibular branches were occasionally interconnected (Figure lo). Table 1 shows that anastomoses
may exist among the tuberoinfundibular artery and
the supraoptic vessel, the SHA (Figures lm and 5),
the optic branch of the ICA (Figure lp), the PCoA
(Figure lq), and the tuberoinfundibular branch of
the PCoA. (Figures Ir and 7). These anastomoses
were usually situated between the optic tract and
the proximal pituitary stalk (Figures 5 and 7).
Anastomoses were found not only between the
tuberoinfundibular branch of the PCoA and the
neighboring vessels, but also among the collateral
branches of the branch itself in 20% (two brains)
(Figure lu). There were one to three anastomotic
channels 30-100 (mean±SD 62±29) jun wide and
1.0-1.8 (mean 1.4) mm long. The interconnected
branches were 70-210 (mean±SD 134±53) fim in
diameter. In brains with several tuberoinfundibular
arteries, the anastomoses could connect the ipsilat-
1346
Stroke
Vol 20, No 10, October 1989
FIGURE
3.
Anastomosis
(arrows) between two optic
branches (1 and 2) of left superior hypophyseal artery (3).
Note left trabecular artery (4).
Compare with Figure 1, k and
i. 5, right superior hypophyseal artery; 6, pituitary stalk
(cut); 7 and T, right and left
internal carotid arteries; 8 and
8', right and left optic nerves;
9, anterior cerebral arteries.
Basal view. x5.1.
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eral (Figures lv and 8) or contralateral arteries
(Figure lw). Such anastomoses were sometimes
connected to the mamillary branches (Figure lx and
w). Other anastomoses (Table 1) were seen among
the tuberoinfundibular artery and the SHA (Figures
In and 6), the tuberoinfundibular branch of the ICA
(Figures lr and 7), the optic branch of the ICA
(Figure Is), the PCoA (Figures It and 8), the
mamillary branch of the PCoA (Figure lx) or the
PCA (Figures ly and 11), and the premamillary
artery. These anastomoses could be located on the
lateral or caudal part of the median eminence (Fig-
ures 6, 7, and 11) and/or along the proximal pituitary stalk (Figure 1).
There were one to four mamillary branches of
the PCoA. In addition to the connections among
these vessels themselves (Figures lz and 9), we
also found anastomoses (Table 1) among the mamillary branches of the PCoA and the tuberoinfundibular branch of the PCoA (Figure lx), the mamillary branch of the PCA (Figures lat and 10), the
perforating (thalamoperforating, interpeduncular)
branches of the PCA, and the premamillary artery
(Figure lC]). The anastomoses were located around
FIGURE 4. Small anastomoticplexus (arrows) between
rostral stems (1 and V) of
right (2) and left (2') superior
hypophyseal arteries. Compare with Figure lh. 3, posterior median
commissural
artery; 4, optic chiasm; 5, pituitary stalk (cut). Basal view.
X36.5.
Marinkovic et al
Hypothalamic Arterial Anastomoses
1347
FIGURE 5. Anastomosis (large
8
arrows) between caudal stem
(1) of right superior hypophyseal artery (2) and branch (3) of
tuberoinfundibular artery (4)
arising from internal carotid
artery. Compare with Figure
lm. Note also anastomoses
(small arrows) connecting two
branches of same tuberoinfundibular artery. 5,rightposterior communicating artery; 6,
right posterior cerebral artery;
7,rightoptic tract; 8, pituitary
stalk (cut). Basal and slightly
caudal view. X13.8.
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FIGURE 6. Anastomoses (arrows) between branch (1) of
right superior hypophyseal artery (2) and branch (3) of
tuberoinfundibular artery (4) arising from right posterior
communicating artery (5). Compare with Figure In. 6,
internal carotid artery; 7, right optic tract; 8, pituitary
stalk (cut). Basal view. x6.3.
FIGURE 7. Anastomosis (arrows) between branch (1) of
tuberoinfundibular artery (2) arising from left internal
carotid artery (3) and branch (4) of tuberoinfundibular
artery (5) arising from posterior communicating artery
(6). Compare with Figure lr. 7, left mamillary body; 8,
left optic tract. Basal view, x 7.9.
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Vol 20, No 10, October 1989
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FIGURE 8. Anastomosis (small arrows) between two (1
and 2) tuberoinfundibular arteries arising from left posterior communicating artery (3). Note also anastomosis
(large arrow) between tuberoinfundibular artery (1) and
posterior communicating artery (3). Compare with Figure
lv and t. 4, superior hypophyseal artery; 5, left optic
tract. Basal view, "x.15.5.
the mamillary body (Figures 1 and 9) or on its
surface (Figure 10).
The mamillary branches of the PCA (Table 1) were
either interconnected or connected to the tuberoinfundibular branch of the PCoA (Figures ly and 11),
the mamillary branch of the PCoA (Figures la, and
10), the interpeduncular branch of the PCA (Figure
lb,), and/or the premamillary artery (Figure 11). The
anastomoses were situated close to (Figure 1) or on
the surface of the mamillary body (Figure 10).
The premamillary (thalamotuberal, anterior thalamoperforating) artery always arose from the PCoA.
The anastomoses involving the premamillary artery
were rare and, when present, few. We observed
vascular connections among this artery and (Table
1) the tuberoinfundibular branch of the PCoA, the
mamillary branch of the PCoA (Figure lc,) or of the
FIGURE 9. Anastomosis (arrows) between two (1 and 2)
mamillary branches of posterior communicating artery
(3). Compare with Figure lz. 4, left mamillary body; 5,
left optic tract; 6, head of pin. Basal view. x20.2.
PCA (Figure 11), the PCoA (Figure Id,), the peduncular branch of the PCA (Figures le, and 12), and/or
the perforating branch of the anterior choroidal artery
(Figure lft). The latter anastomotic channel was 280
fim wide and 0.3 mm long. The anastomoses were
usually located among the mamillary body, optic
tract, and cerebral peduncle (Figures 1 and 12).
Anastomoses among the hypothalamic arteries
varied from 20 to 280 (mean±SD 71±44) /xm wide
and from 0.1 to 5.3 (mean±SD 1.52±0.9) mm long.
The diameter of the connected arteries ranged from
30 to 1,900 (meaniSD 148±83) /x.m. The number of
anastomoses was correlated with their common
diameter; the more common the anastomoses, the
larger their diameter. The common diameter varied
from 620 to 3,170 (mean 1,044) fim. There were five
to 22 anastomoses (mean 10.1), with five anastomoses seen in 30% (six) of the hemispheres. A correlation between the number and size of certain
hypothalamic arteries, and the number and caliber
of their anastomoses, was not observed.
The anastomoses were like channels or like a
network, with channel-like anastomoses connecting
Marinkovic et al
Hypothalamic Arterial Anastomoses
FIGURE 10.
1349
Anastomosis
(arrows) between mamillary
branch (1) of left posterior
communicating artery (2) and
mamillary branch (3) arising
from interpeduncularperforating branch (4) of left posterior
cerebral artery (5). 6 and 6',
right and left mamillary bodies; 7, median eminence. Basal
and slightly caudal view. x8.8.
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FIGURE 11. Anastomosis (small arrows) between mamillary branch (1) arising from right posterior cerebral artery (2)
and branch of tuberoinfundibular artery (3) arising from left posterior communicating artery (4). Compare with Figure
ly. Note also anastomosis (large arrows) between mamillary branch (5) of left posterior cerebral artery (6) and branch
(7) ofpremamillary artery (not visible). 8, median eminence; 9 and 9', right and left mamillary bodies. Basal view. xll.
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Stroke Vol 20, No 10, October 1989
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FIGURE 12. Anastomosis (arrows) between peduncular
branch (1) of left posterior cerebral artery (2) and caudal
premamillary artery (3). Compare with Figure le,. 4, rostral
premamillary artery; 5, left posterior communicating artery
(displaced medially); 6, anterior choroidal artery; 7, left
optic tract; 8, left crus cerebri; 9, left mamillary body. Basal
view, x.7.7.
either the proximal (Figures 8, 9, and 12) or the
distal (Figures 4-7, 10, and 11) portions of the
hypothalamic arteries. Where there were many anastomoses, we observed various arrangements such
as parallel, alternating, or successive. While some
anastomoses connected two adjacent vessels, others connected several hypothalamic arteries (Figure
13). The channel-like anastomoses connected these
arteries "end-to-end" (Figure 6), "end-to-side" (Figure 5), or "side-to-side" (Figures 8-10 and 12). The
plexiform anastomoses were located at the level of
the lamina terminalis and sometimes around the
proximal pituitary stalk, as well as in the region of
the median eminence (Figure 1).
The anastomoses most often involved the commissural arteries and the SHAs as well as the
tuberoinfundibular branches of the PCoA (Table 1).
The largest anastomoses were observed among the
tuberoinfundibular branches of the PCoA or ICA,
as well as among the premamillary arteries and the
mamillary branches, and were rarest in the distribution of the supraoptic and premamillary arteries.
Discussion
The small central branches of the cerebral arteries, especially the perforating arteries, have been
regarded for decades as end arteries.13 Subsequent
investigation has confirmed the opinion for all of
these vessels14-18 except the interpeduncular (thalamoperforating) branches of the PCA.19>20 Our present study not only revealed the existence of hypothalamic arterial anastomoses in all 14 brains
examined, but also the possibility of involvement of
all the hypothalamic arteries in such connections.
The hypothalamus is highly protected against ischemic lesions because so many anastomoses among
the hypothalamic arteries are continually present and
of considerable size. Hence, lesions are possible only
in systemic disorders (such as arteriosclerosis, diabetes mellitus, multiple microembolism, bleeding disorders, and increased intracranial pressure), following
trauma, and during neurosurgery.21-31
However, there is a greater risk of ischemic
lesions in the hypothalamus of patients having few
anastomoses. Such a lesion may lead to various
clinical signs and symptoms, depending on the
hypothalamic region involved, and may be categorized as visceral, autonomic, endocrine, or metabolic disorders, or as personality changes.21-31 Also,
more frequent ischemic lesions can be expected in
the supplying region of those hypothalamic arteries
with sparse anastomoses, such as the premamillary
artery. Earlier data confirm that this artery is often
mentioned in relation to lateral hypothalamic and
Marinkovic et al
Hypothalamic Arterial Anastomoses
1351
FIGURE 13. Complex anastomotic channels
(arrows)
among branch (1) of superior
hypophyseal artery (2), optic
branch (3) of left internal
carotid artery (4), tuberoinfundibular artery (5) arising
from posterior communicating artery (6), and tuberoinfundibular branch (7) of internal carotid artery. 8, pituitary
stalk (cut). Specimen in Figure 3. Basal view. X15.5.
Downloaded from http://stroke.ahajournals.org/ by guest on July 28, 2017
anterolateral thalamic infarcts.7-8-30-31 Sparse anastomoses in the territory of some other hypothalamic
arteries are compensated for by their varied supply
sources. For example, the supraoptic nucleus can
be nourished by the supraoptic vessels arising from
the ACA, ICA, and SHA.3 Occlusion of one of
these vessels usually is not sufficient to cause any
neuroendocrine disorder.
In addition to the role they play in preventing
ischemic lesions of the hypothalamus in most
patients with cerebrovascular disease, these anastomoses may also be of considerable neuroendocrinologic significance. It is well known that
branches of the SHA and tuberoinfundibular artery
form the primary capillary plexus in the median
eminence and the proximal pituitary stalk.6-10-32
The portal vessels leave this plexus to form the
adenohypophyseal sinusoids. There is experimental evidence that under some circumstances, blood
flow reverses from the anterior pituitary to the
median eminence.6-12>32-34 Three findings are particularly important: the presence of some adenohypophyseal hormones in portal vessels, the detection of certain substances in the hypothalamus
after injecting them into the pituitary, and a few
veins draining the blood from the adenohypophysis.6-32 Because of the reversed blood flow,
pituitary hormones, and perhaps the peptide hormones released within the median eminence, may
reach certain hypothalamic arteries and, through
anastomoses, almost all other hypothalamic arteries. These hormones may influence the hypothalamus in two ways. First, some hormones may
change the diameter of the hypothalamic vessels
and so regulate the neurosecretory activity of
certain hypothalamic nuclei. The presence of the
peptidergic receptors and nerves in the walls of
cerebral and hypothalamic arteries in humans has
been reported.35-36 Second, thanks to anastomoses, these hormones can reach any part of the
hypothalamus and thus may regulate its activity
directly, especially in regions lacking a bloodbrain barrier, such as the organum vasculosum of
the lamina terminalis.37
Although other authors have reported similar
suggestions,6-32 our hypotheses will remain speculative until new evidence of reversed blood flow is
provided, especially direct observation of blood
flow in living animals.
Finally, the hypothalamic arteries and their anastomoses are very important from a neurosurgical
point of view for at least three reasons. First, the
hypothalamic arteries' parent vessels are often the
sites of aneurysms, which may compress and/or
distort the hypothalamic arteries.5-7-8-15-38'39 Second,
we have observed roughly 400-500 hypothalamic
arteries, branches, and anastomoses at the level of
the hypothalamus, a region measuring approximately 2x2 cm. Finally, unexpected anastomotic
channels may be injured during aneurysm surgery,
especially during dissection of the interconnected
hypothalamic vessels from the aneurysmal wall.
Hence, great care must be taken during any operation in the hypothalamic region.
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KEY WORDS
pituitary gland
arterial anastomoses
•
hypothalamus
Microanatomy and possible clinical significance of anastomoses among hypothalamic
arteries.
S V Marinkovic, M M Milisavljevic and Z D Marinkovic
Stroke. 1989;20:1341-1352
doi: 10.1161/01.STR.20.10.1341
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