Ranasinghe et al. BMC Neurology
(2020) 20:320
https://doi.org/10.1186/s12883-020-01889-9

CASE REPORT

Open Access

Artery of Percheron infarction presenting as
nuclear third nerve palsy and transient loss
of consciousness: a case report
K. M. I. U. Ranasinghe* , H. M. M. T. B. Herath, D. Dissanayake and M. Seneviratne

Abstract
Background: Thalamic blood supply consists of four major vascular territories. Out of them paramedian arteries
supply ipsilateral paramedian thalami and occasionally rostral mid brain. Rarely both paramedian arteries arise from
a common trunk that arise from P1 segment of one sided posterior cerebral artery (PCA). This is usually due to
hypoplastic or absent other P1 and this common trunk is termed Artery of Percheron (AOP). Its prevalence is in the
range of 7–11% among the general population and AOP infarcts account in an average of 0.4–0.5% of ischemic
strokes. Clinical presentation of AOP infarction is characterized by impaired arousal and memory, language
impairment and vertical gaze palsy. It also can present with cerebellar signs, hemi paresis and hemi sensory loss.
We herein present a case of AOP infarction presenting as transient loss of consciousness and nuclear third nerve
palsy.
Case presentation: A 51 year old previously healthy male, was brought to us, with a Glasgow coma scale (GCS) of
7/15. GCS improved to 11/15 by the next day, however he had a persisting expressive aphasia. Right sided nuclear
third nerve palsy was apparent with the improvement of GCS. He did not have pyramidal or cerebellar signs.
Thrombolysis was not offered as the therapeutic window was exceeded by the time of diagnosis. Diagnosis was
made using magnetic resonance imaging (MRI) that was done after the initial normal non-contrast computer
tomography (NCCT) brain. He was enrolled in stroke rehabilitation. Aspirin and atorvastatin was started for the
secondary prevention of stroke. He achieved independency of advanced daily living by 1 month, however could
not achieve full recovery to be employed as a taxi driver.
Conclusions: Because of the rarity and varied clinical presentation with altered levels of consciousness, AOP infarcts
are easily overlooked as a stroke leading to delayed diagnosis. Timely diagnosis can prevent unnecessary
investigations and the patient will be benefitted by early revascularization. As it is seldom reported, case reports
remain a valuable source of improving awareness among physicians about this clinical entity.
Keywords: Artery of Percheron (AOP), Case report, Paramedian thalamic infarction, Thalamic infarction, Mid brain
infarction, Nuclear third nerve palsy

* Correspondence: indrachaparanasinghe@gmail.com
National Hospital of Sri Lanka, Colombo, Sri Lanka
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Ranasinghe et al. BMC Neurology

(2020) 20:320

Background
Artery of Percheron (AOP) is an anatomical variant of
posterior circulation arteries of the brain. Gerald Percheron studied thalamic blood supply and described its
anatomical variants depending on the arteries it arise [1].
According to him, P1 segment of the PCA gives rise to
paramedian arteries of each side to supply paramedian
thalami. Sometimes these paramedian arteries can arise
from one common trunk arising from a P1 segment of either side. This is usually due to hypoplastic or absent
other P1 segment. This common trunk is known as AOP.
A compromise of the blood flow of AOP leads to bilateral
paramedian thalamic infarction with or without rostral
mid brain involvement, resulting in characteristic clinical
picture of impaired arousal and memory, language impairment and occasionally ocular movement disorders [2–4].
AOP infarction is only seldom associated with pyramidal
symptoms. Non contrast computer tomography (NCCT)
of the brain is often normal misleading the physician to
consider pathologies other than a stroke.
The exact prevalence of AOP remains unknown. But according to two autopsy studies, this anatomical variant
can be present in 7 to 11.7% [5, 6]. Though it seems to be
a common anatomical variant, strokes due to AOP territory infarction are rare. Its incidence was 0.4% in an analysis done in Mexico involving 3750 patients with first
ever ischemic stroke [3] and was 0.5% in another analysis
on 3712 patients with ischemic stroke [4]. Out of thalamic
strokes, AOP territory strokes lie in the range of 4–18%
[7, 8]. Its rarity and the unusual clinical presentation for a
stroke, cause a delay in institution of advanced brain imaging and diagnosis. Thus, a good knowledge of the clinical presentation of this distinct entity will be helpful in
preventing undue delay in the diagnosis and the administration of thrombolytic therapy when indicated.
Case presentation
A 51-year-old previously healthy male was brought by
his family members following sudden loss of

Page 2 of 5

consciousness. On admission his Glasgow coma scale
(GCS) was 7/15 (eye 1, verbal 2, and motor 4). Neurological examination revealed bilateral symmetrical sluggish pupils of 3 mm. We could do only a limited
neurological examination due to low GCS. He moved all
four limbs to a painful stimulus and the deep tendon reflexes were normal. Bilateral flexor plantar response was
present. With the suspicion of any drug overdose, a
urine sample for toxins was sent urgently, but all the
tested toxins including opioids, benzodiazepines and amphetamines were negative. An urgent NCCT brain was
done within two hours of symptom onset to exclude
intracranial hemorrhage and it turned out to be normal.
After four hours of admission, his GCS improved to
11/15 (E3V2M6). However he was drowsy and there was
bilateral asymmetrical ptosis, right more than left. Third
nerve palsy without pupillary involvement was evident
on the right side. Right eye medial and downward gaze
were impaired. He also had bilateral upward gaze palsy,
but had no nystagmus (Fig. 1). These findings suggested
a right-sided nuclear third nerve palsy. He did not have
pyramidal or cerebellar signs and the visual fields were
normal.
As the NCCT brain was normal, we proceeded with
magnetic resonance imaging (MRI) and magnetic resonance angiogram (MRA) brain. It was reported as acute infarction in bilateral paramedian thalami and medial rostral
mid brain, suggesting AOP territory infarction. MRA
showed hypoplastic right vertebral artery. Apparent diffusion coefficient (ADC) images and diffusion weighted images (DWI) showed the paramedian thalamic infarctions
in the index case due to AOP involvement. Here the rostral mid brain involvement is asymmetrical as was suggested by the clinical findings as well (Fig. 2).
Over a week, his hypersomnolance gradually improved
but his diplopia persisted. After the diagnosis of ischemic stroke, the underlying risk factor assessment was
performed. He had hypertension, but no diabetes mellitus. Lipid profile was deranged with a low density

Fig. 1 Eye movements demonstrating right eye nuclear third nerve palsy. a Neutral position of eyes showing bilateral partial ptosis (right > left)
and outward and downward deviation of the right eye due to third nerve palsy. b Attempted vertical gaze; vertical gaze palsy is apparent. c
Right gaze; right eye abduction and left eye adduction is preserved. d Left gaze; right eye adduction is impaired whereas left eye abduction
is preserved

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Page 3 of 5

associated with motivation and mood [9]. These nuclei
get their blood supply primarily from the posterior cerebral circulation via different perforating arteries.
As described by Percheron, thalamic circulation has
four variations of arterial supply. The following figure
(Fig. 3) demonstrates neurovascular anatomical variants

Fig. 2 MRI images showing AOP territory infarction. a DWI image
showing paramedian thalamic infarctions. b DWI image showing
right rostral midbrain infarction (Note the assymetry in rostral mid
brain involvement). c ADC image showing paramedian thalamic
infarctions. d ADC image showing assymetrical right rostral
midbrain infarction

lipoprotein of 140 mg/dL. Electrocardiogram did not
show any evidence of arrhythmia or past cardiac ischemic events. Transthoracic echocardiogram was normal
except for the left ventricular hypertrophy. He did not
have polycythemia or thrombocytosis. As he had conventional risk factors for a stroke, we did not further
evaluate for other thrombophilic conditions. He was discharged after 1 week of hospitalization with out-patient
speech and physiotherapy. We started aspirin 75 mg, clopidogrel 75 mg and atorvastatin 40 mg daily. At the
clinic visit scheduled 3 weeks after the discharge, clopidogrel was withheld and aspirin 75 mg and atorvastatin
40 mg were continued. By the time of clinic visit he had
a marked recovery and could engage in his day-to-day
activities. However he could not resume his work as a
taxi driver even 3 months after the initial stroke.

Discussion and conclusions
Thalamus consists of five major functional nuclei i.e.
nociception and arousal controlling intralaminar and reticular nuclei, sensory nuclei receiving inputs from all
major sensory domains, effector nuclei controlling language and motor function, associative nuclei that involve
in higher cognitive functions and limbic nuclei

Fig. 3 Neurovascular anatomical variants supplying paramedian
thalamus and mid brain as was described by Percheron [10].
(Adapted from, Artery of Percheron infarction: review of literature
with a case report. Radiology and oncology. 2015 Jun 1;49 (2):141–
6.Written permission was obtained from the author and the journal
to use as an open access figure). a Variant I - each side perforating
arteries arising from each PCA. b Variant IIa - asymmetrically arising
two perforating arteries from one sided PCA. c Variant IIb - bilateral
thalamic perforating arteries arising from a single common trunk
(AOP). d Variant III - an arc bridging P1 segments of bilateral PCA
giving rise to several perforating arteries. Vessels marked by initials:
AICA - anterior inferior cerebellar artery, AOP - artery of Percheron,
BA - basilar artery, MP - midbrain perforators, PCA – posterior
cerebral artery, SCA - superior cerebellar artery, TP thalamic perforators

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supplying thalamus and mid brain. Out of the four variants, variant I is the most common type and in that each
side perforating arteries arise from each PCA. In variant
IIa, asymmetrically arising two perforating arteries from
one sided PCA supply the thalamus. Variant IIb is the
AOP of interest where bilateral thalamic perforating arteries arise from a single common trunk. That common
trunk is named AOP [1, 10]. It supplies the paramedian
thalami of both sides along with the rostral mid brain
[10] Variant III is an arc bridging P1 segments of bilateral PCA giving rise to several perforating arteries that
supply the thalamus.
Vascular compromise to the thalamus can lead to various clinical pictures depending on the territory infarcted.
In the literature, four major vascular territories of thalamus are described with different clinical presentations
of relevant vascular compromise [2]. They are as follows.
Tubulothalamic territory – causes impairment in
orientation, arousal, memory, learning, personality
and executive function
ii. Inferolateral territory – causes hemi sensory loss,
hemi paresis, hemi ataxia of the contralateral side
and post stroke painful syndrome, especially with
right sided strokes
iii. Posteror choroidal territory – causes sensory loss of
the contralateral side, visual field defects, tremor,
dystonia, weakness and occasional language
impairment
iv. Paramedian territory – causes hypersomnolance if
the lesion is bilateral, memory impairment,
difficulty in learning and language deficits

i.

The artery supplying the tubulothalamic territory can be
rarely absent, in which case artery supplying the paramedian territory takes over to supply the former territory as
well. In such situations when the AOP variant also coexists, AOP territory infarction can be devastating as it will
involve both the aforementioned territories [11].
AOP territory strokes are limited to case reports or
small case series in the literature. All of them had an involvement of bilateral paramedian thalami. In addition,
polar thalamic nuclei and mid brain were involved in
some cases [8, 12, 13]. In a case series of fifteen patients
with AOP infarctions, which is the largest case series in
the literature to the best of our knowledge, there were
three patterns of infarction described [4]. They are,
i.

Bilateral paramedian thalamic and rostral mid brain
infarctions – 8 patients out of 15 (53%) had this
pattern. The main presentations were mental state
deficits, ocular movement deficit, aphasia or
dysarthria and amnesia. Prognosis was poor in this
group.

Page 4 of 5

ii. Bilateral paramedian thalamic infarctions without
midbrain involvement – 6 patients (40%) were in
this group. The main presentations were mental
state deficits and amnesia. In addition, cerebellar
signs were seen in 50%. Ocular movement deficits
were less common, noted only in two patients
(33%). Prognosis was favorable.
iii. Bilateral paramedian and anterior thalamic
infarctions without mid brain involvement – Only
one patient out of the fifteen had this presentation.
The reported symptoms and signs were mental
state deficits, ocular movement disorder and
aphasia. Prognosis was favorable.
Our patient had the first presentation described above
with bilateral paramedian and rostral mid brain infarctions. As was seen in the above case series, he presented
with an impaired mental status, with a GCS of 7/15. He
had global aphasia initially. Ocular movement deficits he
had were right sided nuclear third nerve palsy and bilateral upward gaze palsy. Partial ptosis was asymmetrical
with the more affected right side. He did not have cerebellar or pyramidal signs.
The third nerve nucleus is a complex of sub nuclei.
Within the complex, sub nucleus to levator palpebral
superioris is unpaired. Thus a lesion at the nuclear
level will cause bilateral partial ptosis [14]. Furthermore the superior rectus muscle has a crossed innervation whereas motor neurons to medial rectus,
inferior rectus and inferior oblique are uncrossed. So
in case of nuclear third nerve palsy, there will be bilateral superior rectus palsy due to the involvement of
ipsilateral superior rectus nucleus and the crossing fibers from the other side [15].
Our patient’s MRI and MRA findings suggested AOP
territory involvement in which a symmetrical neurological deficit is usually expected. AOP was not visualized in MRA imaging of our patient probably due to its
occlusion. Its anatomical asymmetry in our patient
would explain the right sided third nerve involvement.
In case of AOP infarct, the initial NCCT brain remains
normal most of the time, whereas the diagnosis is made
with a subsequent MRI and diffusion weighted imaging
(DWI). AOP is seldom demonstrated by imaging as it is
too small to be visualized by MRA or CT angiogram, or
as it is occluded [16, 17].
The underlying etiologies for AOP territory infarction
remain the usual causes like hypertension, dyslipidemia,
diabetes, smoking, atrial fibrillation etc. as for any other
ischemic stroke. In a case series of 10 patients with AOP
territory strokes, 60% had small artery disease whereas
40% had cardiac source of embolism [2]. Our patient
was diagnosed with hypertension and dyslipidemia. He
did not have diabetes and echocardiogram was normal.

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So we attributed small artery disease as the potential
cause of his stroke.
If the timely diagnosis of AOP infarct is made within
the therapeutic window of 4.5 h, available treatment modalities include intravenous thrombolysis and endovascular treatment [18]. But mostly due to its varied
presentation, diagnosis is made outside the therapeutic
window, as happened with our patient as well. Prognosis
of thalamic strokes is usually favorable, which applies to
AOP territory infarctions as well [2, 4, 9]. In the aforementioned case series of 15 patients, 67% of who had bilateral paramedian thalamic infarcts had a functional
independency with a Modified Rankin Scale score less
than 2. However those who had rostral midbrain involvement in addition to the paramedian thalamic infarctions, had a poorer outcome. Only 25% of them had
a favorable outcome [4]. Our patient’s hypersomnolance
improved by day seven and at the 3 week review he was
independent in his day to day activities. However he did
not recover fully to resume his work as a taxi driver even
after 3 months.
As discussed above, AOP infarctions remain a rare
subset of ischemic strokes and are commonly overlooked
due to their relative lack of well-known motor deficits
that are expected in a stroke. Timely diagnosis can prevent unnecessary investigations and also the patient will
be benefitted if revascularization is achieved by timely
therapeutic interventions. Because of the rarity of AOP
infarctions, case reports remain to be a valuable source
of improving awareness amongst physicians.
Abbreviations
ADC: Afferent diffusion coefficient; AOP: Artery of Percheron; DWI: Diffusion
weighed imaging; GCS: Glasgow coma scale; MRI: Magnetic resonance
imaging; MRA: Magnetic resonance angiography; NCCT: Non contrast
computer tomography; PCA: Posterior cerebral artery
Acknowledgements
We thank Dr. Katarina Šurlan Popovič, Clinical Institute of Radiology,
University Medical Centre Ljubljana, Ljubljana, Slovenia, for granting
permission to adapt Fig. 3 as an open access figure.
We thank Professor Gregor Sersa, Editor-in-chief, Radiology and Oncology
journal, for granting permission to adapt Fig. 3 as an open access figure.
We thank the team of neurology and radiology at National Hospital of Sri
Lanka, for helping us with the diagnosis and guiding the management.
Authors’ contributions
All authors were involved in the management of the patient. IR did the
initial literature review and wrote the first draft. TH also reviewed literature
and corrected the first draft. DD reviewed the first draft after IR and TH. MS
did the final correction before submission. All authors have read and
approved the final manuscript.
Author’s information
IR – Registrar in Medicine, National Hospital of Sri Lanka, Colombo, Sri Lanka.
TH – Senior registrar in Neurology, National Hospital of Sri Lanka, Colombo,
Sri Lanka.
DD – Danapala Dissanayake, Consultant physician, National Hospital of Sri
Lanka, Colombo, Sri Lanka.
MS – Manohari Seneviratne, Consultant physician, National Hospital of Sri
Lanka, Colombo, Sri Lanka.

Page 5 of 5

Funding
In managing the patient or in writing the case report we did not receive any
funding.
Availability of data and materials
All necessary data and material are provided.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Informed written consent was taken from the spouse of the patient to
publish images and the details relevant to the disease for this scientific
publication.
Competing interests
The authors declare that they do not have any competing interests.
Received: 10 June 2020 Accepted: 16 August 2020

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