Successful recanalization for internal carotid artery occlusion with persistent primitive trigeminal artery manifesting only as ischemia of the posterior circulation

The PPTA is one of the four well known primitive anastomoses between the internal carotid artery and the vertebrobasilar system (the hypoglossal, otic, and proatlantal intersegmental arteries comprise the remaining three). It accounts for approximately 80–85 % of persistent anastomoses [12]. The PPTA originates from the cavernous segment of the ICA and communicates with the BA [13]. Saltzman et al. [14] classified the angiographic appearance of PPTA by conventional angiography into three types according to the angioarchitectural relationship with the neighboring vessels. Cases may be encountered that do not meet Saltzman et al.’s classification, making it difficult to understand the various types of PPTA. Recently, Weon et al. [15] proposed a new classification scheme for PPTA based on MRA, identifying five different types based on their anatomical relationship with the neighboring arteries. According to Weon et al. classification, the PPTA in our case was type 2 [15].

PPTA is frequently associated with other anatomical variations such as absence of the ipsilateral Pcom, vertebral artery, or BA [16, 17]. In a large case series, approximately 75 % of cases demonstrated different grades of BA hypoplasia [9]. In these circumstances, the BA received its flow almost exclusively from the ICA with supply to the upper brain stem, cerebellum and ipsilateral cerebral hemisphere arising from the ICA [16]. However patients with PPTA who developed ICA occlusion with cross flow from the Acom, are at high risk of severe cerebral infarction and associated BA top syndrome.

In our case, the initial NIHSS score was high (35 points) and Acom cross flow was represented on the initial head MRA. Therefore, our first impression was a presumptive diagnosis of BA occlusion. However, reference to prior head MRA, provided additional information necessary for a diagnosis of ICA occlusion, not BA occlusion. Additionally, HIA on the initial MRI DWI showed a lesion limited to the posterior cerebral artery (PCA) area. The PPTA in our case was Weon et al.’s classification type 2 (Fig. 2), which is defined as PCA blood supply predominantly from a patent PCom [15]. Based on this understanding, we were able to determine not only the exact angioarchitectural mechanism of the ICA occlusion but also the location of the thrombus (probably, it located at the origin of PPTA continuing to the origin of Pcom). Ultimately, we were able to attain a good result (a modified Ranking Scale of 1 at discharge). Another factor contributing to the good result might be the use of the Penumbra System, not a stent retriever. In this case, because sufficient cross flow from the Acom was observed on the initial head MRA, the thrombectomy might lead to incidental embolization in new territories (ENT) or embolization of distal territories (EDT) with accompanying Acom occlusion. Mokin et al. reported that an use of direct aspiration (using a 5MAX ACE Reperfusion Catheter) showed less ENT and EDT than the stent retriever in in vitro model experiments [18]. On the other hand, Mulder et al. reported the thrombectomy in posterior circulation stroke through persistent primitive trigeminal artery using a stent retriever as a case report [19]. Therefore, even though it is still controversial which devices (Penumbra System or stent retriever) can show less ENT and EDT, the Penumbra System was critically useful in our case.