Case Report
Hypoplastic Ipsilateral Internal Carotid Artery as a Cause of Acute Ischaemic Stroke: A Case Report
Nalaka Gunawansa*
Department of Vascular and Transplant Surgery, National Institute of Nephrology, Sri Lanka
*Corresponding author: Nalaka Gunawansa, Department of Vascular and Transplant Surgery, National Institute of Nephrology, Colombo, Sri Lanka
Published: 17 Sep, 2018
Cite this article as: Gunawansa N. Hypoplastic Ipsilateral
Internal Carotid Artery as a Cause
of Acute Ischaemic Stroke: A Case
Report. World J Surg Surgical Res.
2018; 1: 1060.
Abstract
Ischaemic stroke caused by carotid artery disease is generally attributed to atherosclerotic disease
of the carotid bifurcation. Non-atherosclerotic disease of the carotid arteries causing ischaemic
stroke, though documented, is rather rare. Less frequently, carotid artery dissection, fibro-muscular
dysplasia and post-traumatic thrombosis have been described as a cause of stroke. Developmental
abnormalities of the intra-cranial carotid or vertebral arteries can result in an incomplete formation
of the circle of Willis. However, such developmental abnormalities affecting the extra-cranial
carotid arteries is extremely rare and have largely been identified only as an autopsy finding among
individuals who remained free of cerebral symptoms throughout their lifetime. Nevertheless, the
identification of such maldeveloped extra-cranial carotid arteries in patients with ischaemic stroke
offers the clinicians a total new dimension in to cerebral perfusion and stroke aetiology.
Keywords: Stroke; Cerebral ischaemia; Carotid stenosis; Atherosclerosis; Carotid hypoplasia
Introduction
Developmental anomalies of the intra-cranial arteries constituting the Circle of Willis have been frequently documented. However, such developmental anomalies affecting the extra-cranial carotid arteries are extremely rare. Among them, Hypoplasia Of The Internal Carotid Artery (HICA) has a reported prevalence of 0.01% [1,2]. HICA involves the relative and significant narrowing of the extra-cranial internal carotid artery along its entire course outside the cranium without any localized region of stenosis or occlusion. Majority of such HICAs remain asymptomatic and are only identified incidentally during imaging for other indications or during autopsy [3]. Collateral circulation from the contra lateral side internal carotid artery as well as bilateral vertebral arteries result in the great majority of these patients remaining asymptomatic. The reported incidence of ipsilateral ischaemic stroke caused by HICA is extremely rare. This report describes a unique patient who presented with acute ischaemic stroke and was found to have an ipsilateral HICA as the only identifiable cause for stroke
Case Presentation
A 53-year-oldman was transferred to the emergency department with acute onset weakness of
the left arm and leg associated with slurring of speech. The symptoms had been persistent for just
over 36 hrs by the time he was taken to a regional hospital and then referred to the tertiary hospital.
He had no prior history suggestive of stroke, transient ischaemic attacks or ameurosis fugax. He
was a non-smoker and had no history suggestive of ischaemic heart disease or peripheral arterial
occlusive disease. He had no diabetes or hypertension nor hypercholesterolaemia. He was not on
any long-term medication.
On examination, he had weakness of the left arm and leg (muscle power 3/5). There was obvious
slurring of speech but no neurological deficit in the facial musculature. His pulse rate was regular
and counted at 76 beats per minute. His blood pressure was 155/90 mmHg.
A non-contrast Computerized Tomography (CT) scan was done which confirmed an ischaemic
stroke involving the middle cerebral artery region of the right side. The electro-cardiogram with
rhythm strip showed normal sinus rhythm. The trans-thoracic echocardiogram showed normal
cardiac structure and function with no evidence of cardiac thrombi or vegetations. A carotid duplex
scan was also done to assess the extra-cranial carotid and vertebral arteries. The duplex scan findings
showed normal structure and flow on the left side but with a thinned out (2.8 mm) narrow lumen
internal carotid artery on the right side. This relative narrowing of the lumen was seen throughout
the entire course of the artery in the extra-cranial segment. There was no demonstrable localized stenosis or plaque formation within the lumen. The flow velocities
were within normal limits with no significant turbulence.
A CT Angiogram (Figure 1) and Magnetic Resonance Angiogram
(MRA) (Figure 2) of the carotid vasculature were carried out to
better define the carotid artery anatomy. The imaging revealed a
thinned out right internal carotid artery throughout its course in
to the intracranial segments. The images of the skull base revealed
asymmetrically small carotid canal on the right side compared to the
left carotid canal. There was no evidence of atherosclerotic disease
or carotid dissection. After careful study of the clinical presentation
and the imaging, a diagnosis of right sided HICA disease with acute
ischaemic stroke was made.
Treatment was started with dual antiplatelets (aspirin and
clopidogrel both at 75 mg daily). He was also started on atorvastatin
20 mg daily and ramipril 2.5 mg for blood pressure control. A
programmed physiotherapy regime was started and speech therapy
rehabilitation was also commenced. Day-05 after admission, the
patient was discharged with the above medication to continue
physiotherapy and rehabilitation on an out-patient basis.
At 12 months follow-up, the patient remains well and has had
no further ischaemic episodes. He has recovered completely from
his leg weakness although some residual slurring of speech and some
weakness of the left arm (power 4/5) remains.
Figure 1
Figure 2
Discussion
Developmental anomalies of the extra-cranial carotid arteries are
rare with a reported prevalence of 0.01% [1]. As mentioned above,
they are mostly detected by incidental imaging or at autopsy. The
incidence of HICA causing ipsilateral ischaemic stroke is extremely
rare with reported cases in the literature being around under a
hundred cases [4,5]. Among these, approximately half have been
reported as bilateral [6].
Lie et al. in his landmark paper on congenital anomalies of the
carotid arteries, classified these anomalies in to three basic categories;
agenesis, aphasia and hypoplasia [7]. In agenesis and aphasia, the
affected internal carotid artery is totally absent in adult life. In Internal
carotid hypoplasia, such as was seen in this index patient, it is present
but significantly narrowed along its entire course compared to its
contra lateral counterpart. The confirmation of diagnosis is by seeing
a narrowed carotid canal in the skull base which signifies the absence
of a normal sized carotid artery from the developmental stages [8,9].
This finding helps to differentiate HICA from other conditions such
as chronic dissection of the artery or fibro muscular dysplasia, where
the carotid canal will appear normal in size as it was developmentally
normal and acquired the disease later in life. Hence the presence of
a narrowed carotid canal signifies a developmental anomaly present
from birth, as opposed to an acquired disease of the carotid artery.
HICA can often be associated with other developmental
anomalies of the Circle of Willis including aneurysms which may be
present in 23% to 45% of patients, compared to 2% to 4% seen in the
general population [2,10]. The path physiology behind the formation
of such aneurysms is thought to be the asymmetrical hemodynamic
with hyper perfusion on the contra lateral side. Once HICA has been
identified, the presence of such co-existent anomalies need to be
actively looked for and excluded in order to prevent possible cerebrovascular
accidents in the future. No other anomalies in the circle of
Willis were found in our index patient.
The recommended management of HICA in the absence of coexistent
intra-cranial aneurysms remains ‘best medical therapy’. This
includes the combination of anti platelet drugs, statin therapy and
blood pressure control. However, considering the very low incidence
of HICA, majority of such treatment evidence comes from anecdotal
experience.
Conclusion
Developmental anomaly of the extra-cranial carotid artery causing carotid hypoplasia is a rare finding usually detected at autopsy. A few cases of such carotid hypoplasia have been described in association with ipsilateral ischaemic stroke. The diagnostic confirmation is based on the demonstration of a comparatively narrowed internal carotid artery along its entire course beyond the carotid bifurcation along with a structurally narrowed carotid canal in the base of the skull. Approximately 1/3 of such patients may have co-existent intracranial cerebral aneurysms that may require surgical intervention. In the absence of such co-existent pathology, isolated internal carotid hypoplasia is managed expectantly with ‘best medical therapy’.
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