Inadvertent stent placement in the persistent hypoglossal artery: A case for caution
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.232348
Source of Support: None, Conflict of Interest: None
The persistent hypoglossal artery (PHA) is an uncommon vascular anomaly that results from persisence of fetal carotid basilar anastomosis. It has a reported prevalence of 0.02–0.10%. The recognition of this anomaly, however, is very important as it can have significant clinical implications. We report a case of an ischemic stroke due to inadvertent ostial occlusion of the internal carotid artery (ICA) from stent placement in the PHA. We discuss the embryological development of the vertebrobasilar arterial system, the criteria to diagnose the presence of the PHA, and the importance of its recognition in clinical practice.
A 78-year old, right-handed man was evaluated after he developed global aphasia and right hemiparesis in the hospital. He had undergone stenting of the right ICA for asymptomatic, 50–69% stenosis the previous day. His medical history was also significant for a stent in his left ICA placed 5 weeks prior for asymptomatic, 50–69% stenosis based on an abnormal carotid duplex study.
He had been deemed as a 'high risk' candidate for carotid endarterectomy due to a history of congestive heart failure class 3, coronary artery disease, and hypertension.
His initial neurologic evaluation revealed a National Institutes of Health Stroke Scale of 16. He was globally aphasic with significantly impaired fluency and repetition. He could comprehend some simple commands. Also noted were right facial weakness, right hemiparesis, and right hemisensory loss.
A noncontrast head computed tomography obtained as a part of the stroke protocol was significant only for chronic small vessel ischemic disease. He did not receive intravenous alteplase (tissue plasminogen activator) as the onset of his symptoms was outside the therapeutic time window.
Magnetic resonance imaging (MRI) brain showed a small infarct in the left parietal lobe and multiple subacute infarcts in the anterior cerebral artery/middle cerebral artery (ACA/MCA) watershed zone in the left cerebral hemisphere [Figure 1].
Also noted was absence of flow signal voids in the left ICA and bilateral vertebral arteries, and presence of an “aberrant” extremely prominent artery in the left hypoglossal canal consistent with the presence of a PHA. This was further evaluated with a cerebral angiogram that confirmed the presence of a PHA [Figure 2]. The left common carotid artery (CCA) bifurcates into the left external carotid artery (ECA) and a common trunk consisting of the PHA and the left ICA. The PHA then traverses the hypoglossal canal and continues as the vertebral/basilar artery that terminates with the origin of the bilateral posterior cerebral arteries.
The previous stent was inadvertently placed in the PHA. The origin of the true left ICA at the proximal cervical segment medially was being compromised by the mid-distal aspect of the stent, resulting in severe iatrogenic stenosis at its origin. There was significant hypoperfusion of the left MCA/ICA and ACA territory evidenced by delayed transit time in comparison to the posterior circulation vessels.
Over the next week, the patient's neurologic examination improved significantly with return in fluency of speech, naming, and repetition. He continued to have mild persistent weakness in his right upper and lower extremities. Upon subsequent questioning, when his speech improved, the patient stated that he had been experiencing intermittent short-lasting episodes of right upper extremity weakness and speech difficulty for approximately 1 month, beginning soon after the left-sided stent was placed.
Stenting of the “real” left ICA was considered technically difficult and hence a left ECA/ICA bypass was performed to augment blood flow to the left ICA. The patient tolerated the procedure well. He was eventually discharged to the inpatient rehabilitation unit. On follow-up at 1 year following the event, conducted via a telephonic conversation, the patient reported no further episodes of neurologic deficits. His baseline deficits had resolved with the exception of mild persistent right leg weakness.
This case illustrates the importance of knowledge of anatomy prior to any procedure and the specific recognition of rare but important anatomical variants of intracranial arteries, such as the PHA.
The embryology of the vertebrobasilar system is intricate. Following the development of bilateral ICAs from the third branchial arch artery and the distal aspect of the dorsal aorta, the posterior circulation originates as bilateral longitudinal neural arteries in the hindbrain region of the 4 mm embryo (ovulation age 29 days). These arteries are supplied in a cranio-caudal distribution by paired carotid basilar anastomoses, namely the trigeminal artery, otic artery, hypoglossal artery, and the suboccipital inter-segmental artery.
In the 5–6 mm embryo, the posterior communicating arteries form and take over the function of the carotid basilar anastomoses, which consequently degenerate and regress. The otic artery is the first to regress, followed by the hypoglossal and trigeminal arteries. At the same time, the longitudinal neural arteries fuse to form the basilar artery. In the 7–12 mm embryo, the vertebral arteries develop from a transverse anastomosis between the suboccipital intersegmental artery and cervical intersegmental arteries, proceeding downward to the sixth cervical intersegmental artery that forms the origin of the vertebral artery from the subclavian artery. The typical lifespan of the trigeminal, hypoglossal, and otic arteries is approximately 1 week.,,
The PHA is present when (a) the hypoglossal artery arises as an extracranial branch of the ICA, (b) passes through the hypoglossal canal, and (c) the basilar artery originates from the persistent primitive hypoglossal artery.
Interestingly, in our patient, the left CCA gave rise to a common trunk consisting of the PHA and the left ICA.
As evidenced in our case, the presence of the PHA can result in false positive carotid duplex studies, hence confirmation of the anatomy with alternate imaging modalities such as angiography is essential prior to any planned intervention. The PHA is often the dominant vascular supply to the brainstem/cerebellum. Preoperative awareness of its presence is, therefore, crucial as brainstem ischemia could result from ICA cross-clamping during carotid endarterectomy.
In patients with the persistence of carotid basilar anastomosis, carotid atherosclerotic disease could present with posterior circulation symptoms, confusing the clinical scenario.,,
Surgery can be considered a viable treatment option in specific cases.
An ECA/ICA bypass was performed to prevent further ischemic strokes as stenting of the “real” ICA was technically difficult and the infarcts were thought to be a result of hypoperfusion based on their distribution in the watershed territories on MRI as well as by delayed filling of the ACA and MCA compared to the posterior circulation on cerebral angiogram. In cases where the ostium of the ECA is also occluded by the proximal end of the stent, a CCA/ICA bypass could be considered.
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There are no conflicts of interest.
[Figure 1], [Figure 2]