Case Report

Perioperative Bioccipital Watershed Strokes in Bilateral Fetal Posterior Cerebral Arteries
During Spinal Surgery
Gioia Mione1, Guillaume Pische1, Valérie Wolff 2, Romain Tonnelet 3, Lisa Humbertjean1, Sébastien Richard1

Key words

- BACKGROUND: Vision loss due to cerebral infarction during spinal surgery is

- Cerebral watershed infarction

less described. Intraoperative hypotension would be a leading cause. Patients
with variation of the circle of Willis could be more prone to present stroke in
this context, but reports are lacking to sustain the theory. Bilateral occipital
watershed ischemic strokes have never been described before. We report the
case of a patient with a fetal origin of both posterior cerebral arteries (PCAs),
presenting this particular anatomic stroke following lumbar laminectomy surgery for spinal stenosis during which intraoperative hypotension was observed.
We discuss how this common anomaly associated with intraoperative hypotension could have promoted this serious complication.

- Circle of Willis
- Intraoperative hypotension
- Perioperative stroke
- Posterior cerebral artery
- Spinal surgery
- Vision loss

Abbreviations and Acronyms
BP: Blood pressure
CBF: Cerebral blood flow
ECG: Electrocardiogram
fPCA: Fetal posterior cerebral artery
ICA: Internal carotid artery
PCA: Posterior cerebral artery
From the Departments of 1Neurology, Stroke Unit, and
3
Neuroradiology, University Hospital of Nancy, France; and
2
Department of Neurology, Stroke Unit, University Hospital
of Strasbourg, France
To whom correspondence should be addressed:
Sébastien Richard, M.D., Ph.D.
[E-mail: s.richard@chu-nancy.fr]
Citation: World Neurosurg. (2016) 85:367.e17-367.e21.
http://dx.doi.org/10.1016/j.wneu.2015.09.098
Journal homepage: www.WORLDNEUROSURGERY.org
Available online: www.sciencedirect.com
1878-8750/$ - see front matter ª 2016 Elsevier Inc.
All rights reserved.

- CASE

DESCRIPTION: A 55-year-old man woke up with cortical blindness
after he had undergone lumbar surgery during which a marked decrease in
blood pressure had occurred. Magnetic resonance imaging revealed bilateral
symmetric infarctions of the occipital lobes in the distal territory of both PCAs
and smaller anterior watershed ischemic strokes, suggesting a hemodynamic
mechanism. Extended investigations, including conventional angiography, failed
to find any cause of stroke but revealed bilateral fetal PCAs supplied by internal
carotid arteries only. Two years later, the patient has not recovered and remains
severely visually impaired.

- CONCLUSIONS: The

standing hypothesis would be posterior low-flow
infarctions resulting from intraoperative hypotension on a variation of the circle of Willis more prone to decrease in cerebral blood flow. Moreover, this case
supports the hypothesis of vascular insufficiency due to intraoperative hypotension as cause of stroke during spinal surgery.

INTRODUCTION
Perioperative stroke is a rare complication
of general surgery with an estimated
incidence between 0.02% and 1%.1-3
Intraoperative hypotension is considered
to be at least a promoting factor, but
mechanisms affecting cerebral circulation
remain unclear.4,5 More, it has been suggested that congenital variation of the
circle of Willis could potentiate the risk of
watershed strokes during intraoperative
hypotension.4,6 Patients undergoing spinal
surgery are particularly exposed to intraoperative hypotension with a risk of vision
loss due to ophthalmic and cortical
infarctions. Watershed ischemic strokes in
the posterior cerebral artery (PCA) territories have never been described before. It
would support the hypothesis of cerebral
hemodynamic insufficiency by decreased

cerebral blood flow (CBF) as a mechanism
of ischemia.7 We report a case of a patient
with bilateral fetal PCAs (fPCAs) who
presented this particular anatomic
infarction in the course of spinal surgery
during which intraoperative hypotension
was applied.
CASE
The patient gave written consent for the
description of the case. The case was
reported to the pharmacovigilance center.
A 55-year-old man, without any specific
medical history or under any treatment (165
cm, 65 kg, body mass index of 23.9 kg/m2),
was admitted for scheduled lumbar laminectomy surgery for spinal stenosis. Blood
pressure (BP) before surgery was 176/114 mm

WORLD NEUROSURGERY 85: 367.e17-367.e21, JANUARY 2016

Hg. After premedication with 100 mg hydroxyzine orally, anesthesia was induced
with inspired sevoflurane 5%, sufentanil
75mg, and propofol 120 mg. It was maintained with inspired sevoflurane 1% to 3%
with an additional dose of 75 mg sufentanyl.
After induction, the patient was placed in the
genupectoral position for surgery. Electrocardiogram (ECG), blood oxygen saturation,
capnia, and temperature were monitored
throughout the anesthesia, as well as BP
with a noninvasive cuff on the right arm.
Systolic BP was between 61 and 145 mm Hg
with the exception of a 12-minute period at
48 mm Hg. It was lowered to <80 mm Hg for
75 minutes to prevent bleeding. Diastolic BP
averaged 53 mm Hg (Figure 1). Total
anesthesia time was 95 minutes. No blood
transfusion was required. Once ventilation

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CASE REPORT
GIOIA MIONE ET AL.

BIOCCIPITAL WATERSHED STROKES DURING SPINAL SURGERY

Figure 1. Patient’s blood pressure profile during anesthesia.

resumed spontaneously, the patient’s
trachea was extubated and the patient was
taken to the recovery area without any
reported incident or cardiac arrhythmia.
When he woke up, he complained of
complete blindness. Ocular appearance
was normal at funduscopic examination
with complete pupillary responsiveness.
No confusion or memory disturbance was
noticed. Brain magnetic resonance
imaging revealed extended symmetric
areas of recent ischemia in both occipital
lobes on diffusion-weighted sequences

(Figure 2A) and a typical aspect of bilateral
anterior watershed strokes at the junction
of the anterior and middle cerebral arteries
(Figure 2B). Cerebral infarctions were
already visible as hyperintensities on fluid
attenuated inversion recovery sequences.
Time-of-flight magnetic resonance angiography did not show any vascular occlusion
but revealed a bilateral fPCA with hypoplasia
of proximal segments P1 (Figure 3A and B).
Blood tests showed a hemoglobin level of 14
g/dL, platelet count of 200 G/L, C-reactive
protein level of 9 mg/L, low-density

Figure 2. Axial diffusion weighted cerebral resonance magnetic imaging
showing recent ischemia in both distal territories of cerebral posterior
arteries (A) and recent bilateral anterior watershed ischemic strokes (B).

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lipoprotein cholesterol level of 3.16 mmol/L,
and preprandial blood glucose level of 6
mmol/L. Coagulation tests were normal.
ECG, 48-hour cardiac monitoring, transesophageal echocardiography, and examination of cervical and cerebral arteries by
ultrasound were normal. BP monitoring
in the stroke unit did not reveal arterial
hypertension. Faced with this unusual
aspect of ischemia in both PCA territories,
a conventional angiography was performed.
It showed normal arterial caliber but
confirmed the variation of the circle of
Willis with both PCAs originating from
the carotids through posterior communicating arteries, hypoplastic P1 segment,
and distal part of the basilar artery
(Figure 3C and D). Unfortunately, the
patient’s clinical status did not significantly
improve during hospitalization. The
patient was discharged with paramedical
assistance and a daily dose of aspirin.
Severe visual impairment and left spatial
neglect remain after 2 years.
DISCUSSION
Vision loss is a complication encountered
in 0.2% of spinal surgeries.8,9 Most cases
result from ischemia of the optic nerve or
the retina promoted by anemia, intraoperative hypotension, and elevated intraocular pressure due to prone position
during a long time.10 Cortical blindness
and cerebral infarction at large are less
described.11
Our
case
suggests
intraoperative hypotension would be a
leading cause of stroke in this context.
Intraoperative hypotension is widely
observed during major spinal surgery due
to disruption of extensive vascular
networks found in bones.12 More, it can
be applied by physicians to decrease
blood loss and avoid transfusion.13,14 The
POISE trial showed that an episode of
hypotension at any time during a patient’s
surgical procedure is related to a higher
risk of perioperative ischemic stroke.5
However, while vascular insufficiency
resulting from decreased CBF would seem
to be the most logical explanation, no
solid evidence supports this theory. There
is a discrepancy between the high
frequency of intraoperative hypotension
and the rare reports of stroke occurring
during general surgery, particularly during
the intraoperative phase, suggesting that
another mechanism is involved. Cerebral

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CASE REPORT
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BIOCCIPITAL WATERSHED STROKES DURING SPINAL SURGERY

Figure 3. Circle of Willis with bilateral fetal posterior cerebral arteries, axial (A) and coronal (B) planes
of time-of-flight magnetic resonance angiography, sagittal view (C) of conventional angiography and
upper oblique view (D) on 3-dimensional reconstruction. ACA, anterior cerebral artery; BA, basilar
artery; ICA, internal carotid artery; MCA, middle cerebral artery; PCA, posterior cerebral artery; PCoA,
posterior communicating artery.

watershed infarctions as a witness of
vascular insufficiency are less described.
More cases of cortical infarctions
suggesting an embolic mechanism are
reported, as perioperative hypotension can
cause paroxysmal atrial fibrillation and
arterial micro emboli.15,16 Nevertheless,
the aspect of posterior infarction in our
case was not typical of stroke due to PCA
occlusion. Rather, it seems to be the
result of a transitory decreased CBF at the
distal parts of the PCAs. Among the
arguments supporting this hypothesis of
cerebral vascular insufficiency during
surgery is the bilateral and symmetric
aspect of the posterior infarctions coupled
with the presence of typical anterior
watershed strokes. Furthermore, thorough
investigations failed to find any other
cause of ischemic stroke. The addition of
two
circumstances
could
explain
watershed infarctions of the PCAs in this
case. First is the dramatic decrease in BP
during spinal surgery, all the more so
given the high initial BP values. However,

we failed to identify hypertension in
medical history and during careful
monitoring in the stroke unit. The

intraoperative BP profile of the patient
accords with criteria of definition of
intraoperative hypotension given by Bijker
et al.: “1) a 20% decrease in systolic
pressure from the baseline value 2) a
combination of systolic pressures below
100 mm Hg or a greater than 30%
decrease from the baseline value, and 3) a
systolic pressure below 80 mm Hg.”17
Prolonged
time
of
intraoperative
hypotension would also be determinant.7
It could result in a decrease of CBF, for
which distal cerebral arterial territories are
the most vulnerable. Furthermore, we
hypothesize that the fPCAs, presented by
this patient, made the posterior territory
more sensitive to a decrease in CBF. This
congenital variation of the circle of Willis
is relatively common: the unilateral form
is found in 11 to 29% of the population,
and the bilateral form in 1 to 9% and is
more often found in brains with signs of
ischemic infarction on autopsy.18,19 It is
an embryonic derivation of the PCA from
the internal carotid artery (ICA) through a
patent posterior communicant artery.
Consequently,
the
PCAs
depend
completely on the anterior circulation and
the ICAs have to supply a larger flow
territory (Figure 4). Moreover, this
disposition
and
the
absence
of
communication of the PCAs with the
vertebrobasilar system would mean that
the occipital lobe is a more distal vascular
area, more prone to suffering from a

Figure 4. Bilateral fetal posterior cerebral arteries and consequences on
cerebral blood flow.

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CASE REPORT
GIOIA MIONE ET AL.

decrease in CBF. The presence of typical
anterior watershed strokes suggests this
variation made all the ICA territory more
vulnerable to intraoperative hypotension,
in contrast to posterior territories like the
cerebellum and brainstem, where no
infarction occurred. Drummond et al.
have already described a left anterior
watershed cerebral infarction following
intraoperative hypotension and suggested
that a congenital variation of the circle of
Willis would potentiate the hemodynamic
effect.6 But this case differs from ours as
it concerns a unilateral anterior infarction
with an isolated left carotid (i.e.,
supplying the left anterior circulation only
without any communication with the
contralateral and posterior circulations).
However, both cases indicate that an
incomplete circle of Willis increases
vulnerability to BP decrease and the
severity of the resulting ischemic strokes.
Both patients presented large cerebral
infarctions, bilateral in our case, and
resulted in severe disability. The severity
of the strokes could in part be explained
by the fact that the central nervous system
suffering from ischemia would be less
able to regulate BP and respond to drugs
correcting intraoperative hypotension, one
problem making the other worse.20
Bilateral infarctions in the PCA territories
previously described in the literature differ
from our case in several points. These
strokes usually result from embolic
mechanisms due to atrial fibrillation or
artery-to-artery embolization.21 The latter
may even originate from ulcerated
atherosclerotic plaques in ICA through
persistent
cervical
embryologic
connections with posterior circulation,
like hypogloss and trigeminal arteries.22,23
Fortunately, our patient did not present
the classical Dide-Botcazo syndrome,
described in bioccipital infarctions, associating anosognosia, amnesia, and topographical disorientation in addition to
cortical blindness. This would be explained
by the conservation of the inferomedial
temporal lobe structures and thalami
usually involved following the complete
occlusion of PCAs.24 We can conclude
that a hemodynamic mechanism in our
case led to a posterior cortical infarction
with a particular location and clinical
presentation.

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BIOCCIPITAL WATERSHED STROKES DURING SPINAL SURGERY

CONCLUSIONS
The atypical posterior watershed strokes
presented by our patient could be the
result of a decrease in arterial BP during
spinal surgery occurring in a setting of
bilateral fPCAs. This case supports the
hemodynamic insufficiency hypothesis as
a mechanism of stroke due to intraoperative hypotension during spinal surgery. It would also suggest that patients
with this common variation of the circle of
Willis are at higher risk of intraoperative
stroke and intraoperative hypotension
should be avoided in this context.
ACKNOWLEDGMENTS
We appreciate Felicity Neilson, Matrix
Consultants, for having reviewed the
English language with scientific expertise.
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Citation: World Neurosurg. (2016) 85:367.e17-367.e21.
http://dx.doi.org/10.1016/j.wneu.2015.09.098
Journal homepage: www.WORLDNEUROSURGERY.org

Conflict of interest statement: The authors declare that the
article content was composed in the absence of any
commercial or financial relationships that could be construed
as a potential conflict of interest.

Available online: www.sciencedirect.com
1878-8750/$ - see front matter ª 2016 Elsevier Inc.
All rights reserved.

Received 3 September 2015; accepted 25 September 2015

WORLD NEUROSURGERY 85: 367.e17-367.e21, JANUARY 2016

www.WORLDNEUROSURGERY.org

367.E21