Comment on "the relationship of the posterior inferior cerebellar artery to the cranial nerves VII-XII".

Saylam et al. (2007) are to be congratulated for their recent article on the relationship of the posterior inferior cerebellar artery (PICA) with the cranial nerves, with particular reference to the microsurgery of this region. However, we would like to bring some additional observations to the attention of the authors. The study of the vessels of the brain base is one of our fields of research (De Caro et al., 1990, 1991, 1995, 1996, 1998, 2000; Porzionato et al., 2004; Macchi et al., 2005; Parenti et al., 2005). We studied the PICA on 40 autoptic brains (Macchi et al., 2004), and we were able to analyze the origin and the whole course of 80 PICAs, with reference to the five segments described by Lister et al. (1982), which were recognizable on both sides. It is a pity that Saylam et al. (2007) analyzed 40 PICAs of 25 cadavers, limiting their study to only two segments, i.e., the anteromedullary and the lateromedullary. In their results, the relationships of the PICA with the cranial nerves are listed following the number of cranial nerve [‘‘(1) course of the LM segment of the PICA and its relationship to the facial and vestibular nerves; (2) relationship between the origin of the PICA and its course relative to the rootlets of the glossopharyngeal, vagus, and accessory nerves; (3) relationship between the rootlets of the hypoglossal nerve and the PICA], rather than to the topographical course of the PICA, which would be clinically useful (origin and relationship of the PICA and hypoglossal rootlets; lateromedullary segment of the PICA; relationship between the PICA and the glossopharyngeal, vagus, and accessory nerves; tonsillomedullary and telovelotonsillary segments’ bifurcation). The former way of presentation has led the authors to a misinterpretation of the results of Macchi et al. (2004). Indeed, Saylam et al. (2007) discuss that the relationship of the PICA with the vagus nerve ‘‘is somewhat variable’’ with respect to the patterns of the course proposed by Macchi et al. (2004), who found that if the artery originates at a caudal level, it tends to pass below the vagus nerve and that if it originates from the basilar artery (BA), it passes above that nerve. In reality, the caudal level of the origin of the PICA corresponds to the lateromedullary segment of the vertebral artery (VA), and the data reported in Table 2 of the paper by Saylam et al. (2007) makes it clear that when the PICA originates from the lateromedullary segment of the VA, it is located in all the cases (10/10) below the vagus nerve. Thus, the findings of Saylam et al. (2007), adding 10 further new cases, confirm our hypothesis (Macchi et al., 2004). Moreover, Saylam et al. (2007) report that they found only one PICA originating from the BA and passing between the IX and X cranial nerves, as shown in Figure 2; however, Figure 7 shows one more PICA originating from the BA, and passing above the IX cranial nerves. On the other hand, they did not consider it relevant to provide figures of PICAs originating from the BA and passing below the X cranial nerves. Clinical-anatomic research is using computed tomography angiography (CTA) to map the vasculature in anatomical districts’ study (Tregaskiss et al., 2007). Huynh-Le et al. (2004) reported that threedimensional CTA demonstrates the surgical anatomy of VA-PICA aneurysms in detail, and it is very useful in selecting the optimal surgical approach. Our team is evaluating the course of the PICA in vivo by computed tomography. From our anatomoradiological database (Section of Radiology, Euganea Medica, Italy) six CTAs of the brain vessels (three males, three females; mean age, 54.6 years) were selected. The subjects underwent radiological examination for atherosclerotic pathology of the vessels of the circle of Willis. The CT images were obtained with a 16- slice multidetector CT scanner (Lightspeed16; GE Medical System, Milwaukee, WI) with the parameters (group 1; rotation time, 0.7 sec; thickness, 2.5 mm; table increment, 27/50; field of view, large; kV 140; 380 mA) acquired during the injection of the contrast medium (concentration of 350 mg I/ml, Omnipaque, GE Healthcare, distributed by Amersham Health, Princeton, NJ). A timing-bolus technique was applied to determine the delay time of scanning with a preinjection of 20 ml of contrast media at a flow rateof 5 ml/sec. Subsequently, 90–100 ml were injected intravenously, at 5 ml/sec, followed by a 50-ml saline chaser bolus, via a catheter placed in the cubital vein, and imaging acquisition was obtained in the angiographic phase. The acquired data were then reconstructed with 0.6-mm slice thickness with an overlapping of 0.3 mm. The data were transferred to an Aquarius workstation (TeraRecon TM, San Mateo, CA), and three-dimensional reconstructions (volume rendering technique, maximum intensity projection, and multiplanar reconstructions) were obtained. We were able to visualize the PICA in 10/12 PICAs in CT images (Fig. 1), showing the site of origin and the course of the lateromedullary segment. Our data confirm the role of CTA as advancing imaging technologies in basic anatomical research to study the vasculature both in cadaveric research and clinical studies in preoperative planning (Tregaskiss et al., 2007; Rozen et al., 2007).