During the developmental stage of a 4-mm embryo, the ICA supplies the longitudinal neural arteries via the trigeminal artery, optic artery, hypoglossal artery and proatlantal intersegmental artery. In subsequent developmental stages the arteries normally regress and disappear, but if there is incomplete regression or the ipsilateral posterior cerebral artery does not develop properly, a persisting anastomosis, such as PTA, may occur [9
Both the REZ and cisternal part of the nerve are reported to be the responsible sites of TN [10
]. Chidambaranathan et al. reported that PTA originated from the posterolateral margin of the posterior bend of the cavernous segment of the ICA, ran posterolaterally and inferiorly around the dorsum sellae and communicated with the BA in the prepontine cistern [8
]. They also reported that the PTA compressed and distorted the REZ of the trigeminal nerve laterally [8
]. In our case, the PTA ran across Meckel’s cave and compressed the cisternal segment of the nerve caudally. de Bondt et al. found that PTA played a vital important role in TN, reporting that the incidence of PTA among patients with TN was 2.2%, which was much higher than that found in the general population [9
]. Owing to its abnormal blood pattern, the PTA could be large and potentially tortuous compared to the SCA, which is the most common culprit vessel of TN. Compression of the PTA could lead to chronic compression and microtrauma, resulting in hyperactivity of the nerve and ultimately to TN [10
]. Some studies found that branches of the PTA can also be culprit vessels of TN [11
]. PTA-related aneurysm [15
] or arteriovenous malformation (AVM) [16
] have also been reported to negatively affect the trigeminal nerve.
Hemorrhage has been reported to be a severe complication in percutaneous balloon compression (PBC) procedure [17
]. Also, PBC might injure the PTA in the Meckel’s cave, the balloon catheter could puncture the PTA and/or shearing compression could tear PTA during the formation of “pear head”. Consequently, preoperative 3D-TOF and 3D-CISS MR imaging are essential to identify the PTA to rule out PBC for the patients.