Internal carotid artery stenosis: A novel surgical model for moyamoya syndrome

Abstract

Moyamoya is a cerebrovascular disorder characterized by progressive stenosis of the intracranial internal carotid arteries. There are two forms: Disease and Syndrome, with each characterized by the sub-population it affects. Moyamoya syndrome (MMS) is more prominent in adults in their 20's-40's, and is often associated with autoimmune diseases. Currently, there are no surgical models for inducing moyamoya syndrome, so our aim was to develop a new animal model to study this relatively unknown cerebrovascular disease. Here, we demonstrate a new surgical technique termed internal carotid artery stenosis (ICAS), to mimic MMS using micro-coils on the proximal ICA. We tested for Moyamoya-like vasculopathies by fluorescently labelling the mouse cerebrovasculature with Di I for visualization and analysis of vessel diameter at the distal ICA and anastomoses on the cortical surface. Results show a significant narrowing of the distal ICA and anterior cerebral artery (ACA) in the Circle of Willis, as observed in humans. There is also a significant decrease in the number of anastomoses between the middle cerebral artery (MCA) and the ACA in the watershed region of the cortex. While further characterization is needed, this ICAS model can be applied to transgenic mice displaying co-morbidities as observed within the Moyamoya syndrome population, allowing a better understanding of the disease and development of novel treatments.

Fig 1. Internal carotid artery stenosis (ICAS) surgical methods.

A) Orientation of the mouse during the surgical procedure. Head (teeth), forepaws and tail are restrained and incision is made in the midline of the neck (red dashed line). White box indicates region of images that follow. B) Opening of the cervical region exposing the trachea, sternocleidomastoid (SCM) muscle and posterior belly of the digastric (PBD) muscle. C) Suture (S1-2) placement retracting the SCM and PBD to expose the common, internal and external carotid (CCA, ICA, ECA) arteries. D) Identification of the occipital artery (OA), vagus nerve (VN) and ICA. E) Suture ligation of the OA and dashed line showing cut to better expose the ICA. F) Cut OA with ICA exposed and isolated using 6–0 suture. G) Micro-coil placement on ICA deep to ECA (as seen in H).

Fig 2. Decreased vessel diameter at the Circle of Willis is observed following ICAS.

A) Representative images of Di I perfused brains from control and ICAS mice. Images are of the ventral side of the brain and show the ipsilateral and contralateral internal carotid artery (ICA) which bifurcates into the anterior cerebral artery (ACA) and middle cerebral artery (MCA). B) Quantification of the ICA, ACA and MCA vessel diameter of the ipsilateral and contralateral sides in control (N = 5) and ICAS (N = 6) mice. *p < 0.05.

Fig 3. Translational comparison between human MMS and ICAS mechanical mouse model.

A) Image of Di I stained blood vessels from ICAS mouse model compared to B) AP angiogram of de-identified patient with Suzuki grade I MMS. Block arrows indicate the supraclinoid ICA stenosis, similar in position in both images. AChorA: anterior choroidal artery.

Fig 4. Decreased number of anastomoses in ICAS mice.

A) Representative dorsal images of Di I perfused brains of control and ICAS mice. Magnified images below to show detail of branching and connections. White circle is one example of an anastomosis. B) Quantification of the number of anastomoses between the ACA and MCA of both ipsilateral and contralateral sides in control (N = 5) and ICAS (N = 6) mice. **p < 0.01.