Introduction 27 7 8 19 22 26 30 24 36 39 6 11 15 21 14 20 21 26 Patients and methods Patients 1 Table 1 Summary of clinical features Case no. Age/sex Presentation Location Embolization Angiography Attempts and interval Outcome 1. WP 58Y/M Pulsatile bruit, rt. hypoglossal nerve paresis Rt. jugular process  and bulb Yes Feeders: rt. ascending pharyngeal and occipital arteries of ECA 2, 2 days No additional deficits; symptom free 2. KW 72Y/F Pulsatile bruit, swelling of rt. upper and lower eyelids Rt. jugular process  and bulb Yes Feeders: Both ascending pharyngeal and rt. occipital arteries of ECA 4, 5 days No deficits; symptoms improved 3. SH 70Y/F Pulsatile bruit Dorsal rim of foramen magnum, both occipital condyles and jugular processes Yes Feeders: Both internal maxillary and occipital arteries of ECA 2, 1 month No deficits, symptom-free 4. BE 68Y/F Pulsatile bruit Rt. Jugular tubercle and bulb Yes Feeders: rt. ascending pharyngeal and occipital arteries of ECA 2, 4 days Mild hypoglossal nerve palsy; symptom-free Abbreviations: Y: years; M: male; F: female; Rt: right; ECA: external carotid artery; Attempts and interval: attempts of endovascular embolization, and timing between the last endovascular and surgical treatment All patients underwent preoperative angiography and at least two attempts of endovascular embolization. For the occlusion of arterial feeders, Guglielmi electrolytically detachable platinum coils were used. The decision for surgical intervention was made after the endovascular approach proved unsuccessful in terms of complete obliteration, and the patient developed neurological deficits or intolerable symptoms of pulsatile bruit. Case histories Case 1 1 1 Fig. 1 a b arrows c d e f g h  Case 2 2 2 Fig. 2 a b arrows c d white arrows e f  Case 3 3 3 4 Fig. 3 a b c d e arrows f g  Fig. 4 3 a b c d e f g g  Case 4 Surgical technique 5 Fig. 5 upper lower  6 7 6 Fig. 6 Artistic illustration showing the transcondylar approach as applied to interrupt the connecting arterial feeders; the extent of the bony removal is judged according to the extent of the arteriovenous fistulas. Transosseous arterial feeders are encountered, which may occasionally cause a brisk arterial bleeding  Fig. 7 1 2 3 4 5 a b c d e  Intraosseous DAVFs were also encountered around the hypoglossal canal, with arteriovenous shunts flowing into the venous plexus surrounding the hypoglossal canal, and more anteriorly in the region of the inferior petrosal sinus. To reach this area, the bony resection was extended into a deeper region. Use of the intraoperative microdoppler probe gave a good impression of the arterialization of the jugular bulb. Thus, persistence of intraosseous arterial feeders indicated that bony resection had to be continued by drilling the jugular tubercle, the occipital condyle and the jugular process. The required extent of bone removal was also estimated from preoperative imaging, and was related to anatomical landmarks such as the hypoglossal canal, the posterior condylar emissary canal and the dural entrance of the vertebral artery. Drilling was stopped only when no more arterial feeders were encountered, indicating that all feeders had been interrupted. Normalization of blood flow within the jugular bulb could be documented by using the microdoppler probe. To adequately drill the dorsomedial portion of the occipital condyle, a small portion of the lateral atlantal mass had to be resected in some instances as well. In such cases, complete exposure of the horizontal portion of the vertebral artery was necessary. However, there was no need for complete C1 hemilaminectomy. The suboccipital dura mater was not opened, since an intradural inspection of the jugular foramen was unnecessary as there were no intradural arteriovenous shunts. After meticulous extradural hemostasis, wound closure was obtained in several layers. Results All four patients underwent surgical obliteration of their DAVFs via the transcondylar approach. This access route provided a good exposure of the target site, and allowed occlusion of the intraosseous pathological vessels. There were no intra-operative complications, and no permanent major postoperative deficit occurred. Despite a certain blood loss during surgery, no patient required intra-operative or postoperative blood transfusion. Although an extensive resection of the involved occipital condyle, jugular process and jugular tubercle was carried out in all patients, an occipito-cervical fusion was necessary only in patient 3 with bilateral lesions. There were no additional neurological deficits, with the exception of patient 4, who experienced mild hypoglossal nerve palsy postoperatively. Postoperative angiography was obtained in each patient to confirm obliteration of the DAVFs. Three patients showed radiological cures, with no further treatment necessary. In patient 2, the DAVFs were significantly reduced surgically, but still persisted. Therefore, a second surgical intervention was proposed to the patient, who eventually refused. While preoperative complaints disappeared in three patients, they were clearly improved in one individual. Discussion Definition, terminology, pathology and symptoms 13 7 9 10 18 30 31 31 26 22 8 26 28 29 22 Imaging 17 23 12 32 General management and endovascular intervention 26 14 22 6 15 25 33 6 6 34 34 20 Surgical technique and avoidance of complications 1 5 16 The use of this surgical procedure was most effective, as all patients in our study showed postoperative clinical improvement, and complete obliteration of the intraosseous DAVF in three patients. Only one patient (patient 3), whose angiogram revealed residual AV fistulas, experienced previously developed mild periorbital edema. We believe that this was due to residual pathological vessels anterior to the jugular bulb, an area very difficult to reach surgically. During the removal of pathological bone containing abnormal fistulas in this patient, the dilated thin wall of the jugular bulb was slightly injured. After packing this area of venous bleeding with muscle fascia, no space for further drilling was available. A second, slightly-modified surgical intervention was, therefore, proposed to the patient to obliterate the remaining fistulas, but she refused. 35 2 5 Conclusion Dural arteriovenous fistulas located around the jugular foramen are a less common type of DAVFs. The suboccipital transcondylar approach is considered the best access route when surgery of this particular pathology is intended. The amount of pathological bone that must be removed by drilling depends upon the extent of transosseous arterial feeders. Surgical obliteration of this complex vascular malformation is possible, at least in the cases in which the arterial feeders do not extend too far anterior to the jugular bulb. With this surgical technique, an atlanto-occipital instability may occur in very large or bilateral lesions, requiring occipito-cervical fusion.