Microsurgical Anatomy of the Inferior Petroclival Vein and its Relation to Surrounding Structures: A Cadaveric and Radiological Study

BACKGROUND The inferior petroclival vein (IPV) courses along the extracranial surface of the petroclival fissure. It is occasionally involved in vascular diseases and has recently been used for vascular access to the cavernous sinus. However, detailed descriptions of its anatomy are currently lacking. OBJECTIVE To define the anatomic relationship between the IPV and its surrounding structures based on cadaveric dissection and radiological analysis. METHODS A dry skull and an injected cadaver head were examined to reveal the relationships between the IPV and its surrounding structures. The existence of the IPV and its relationships with other venous structures were also examined by contrast-enhanced, fat-suppressed T1-weighted magnetic resonance imaging in 26 patients (51 sides). RESULTS The entire course of the IPV was shown via stepwise cadaver dissection from below. Its relationships with surrounding structures, such as the jugular bulb, sigmoid sinus, inferior petrosal sinus, petrosal venous confluence, and the posterior, lateral, and anterior condylar veins, were also shown. In the radiological analysis, the IPV was identified on all sides. The rostral end of the vein was connected to the venous plexus around the carotid artery on all sides. The vein drained into the caudal end of the inferior petrosal sinus (49/51 sides, 96.1%) or into the anterior condylar vein (2/51 sides, 3.9%). CONCLUSION A precise understanding of the anatomy of the IPV will enable endovascular and skull base surgeons to achieve diagnoses and gain safe access to lesions involving the IPV.

Unique percutaneous direct puncture technique for occlusion of a hypoglossal canal dural arteriovenous fistula

PurposeTo report percutaneous transcranial puncture, embolization and occlusion of a very symptomatic hypoglossal canal/anterior condylar vein dural arteriovenous fistula (DAVF) using syngo iGuide navigational software in a patient in whom transarterial and transvenous embolization and surgery had failed.MethodsAfter unsuccessful arterial and venous embolization and surgical treatment of a symptomatic hypoglossal canal DAVF, a 47-year-old man was transferred for further management. With exquisite anatomic detail provided by C-arm cone-beam computed tomography (CBCT) equipment (Artis zee Biplane, Dyna CT VC21H, Siemens Healthcare GmbH, Germany) and syngo iGuide needle guidance navigational software (Siemens Healthcare GmbHy) for planning a safe direct approach, the hypoglossal/anterior condylar vein, the dominant outflow vein of the fistula, was needle punctured percutaneously at the hypoglossal foramen and occluded with ethylene vinyl alcohol copolymer liquid embolic agent (Onyx, Medtronic, Minneapolis, Minnesota, USA) after placing two anchoring platinum coils (Target detachable coils, Stryker Neurovascular, Fremont, California, USA).ResultsAfter a year of progressively severe left eye proptosis, chemosis and increased intraocular pressure, the symptoms quickly subsided after this embolization and the patient was symptom free at his 3-month and later checkups.ConclusionWith guidance and imaging provided by CBCT and syngo iGuide navigational software, an otherwise untreatable DAVF was successfully embolized and obliterated by an aggressive unique percutaneous trans-cranial needle puncture of the dominant outflow vein in the hypoglossal canal.

Dural Arteriovenous Fistula at the Anterior Condylar Confluence

We reviewed the records of eight patients with a dural arteriovenous fistula (DAVF) close to the hypoglossal canal and determined the angioarchitecture of the clinical entity at the anterior condylar confluence. Eight patients with DAVF received endovascular treatment at our institute over the past five years. Imaging with selective three-dimensional angiography and thin-slice computed tomography were used to identify the fistula and evaluate the drainage pattern. Based on the angiographic findings, the ascending pharyngeal artery was the main feeder in all cases, and the occipital, middle meningeal, posterior auricular, and posterior meningeal arteries also supplied the DAVF to varying degrees. Contralateral contribution was found in five patients. The main drainage route was the external vertebral plexus via the lateral condylar veins in four patients, the inferior petrosal sinus in three patients, and the internal jugular vein via the connecting emissary veins in one patient. Selective angiography identified the shunt point at the anterior condylar confluence close to the anterior condylar vein. Shunt occlusion with transvenous coil packing was performed in all cases; transarterial feeder embolization was also used in three patients. Two patients treated with tight packing of the anterior condylar vein developed temporary or prolonged hypoglossal palsy. Based on our results, the main confluence of the shunt is located at the anterior condylar confluence connecting the anterior condylar vein and multiple channels leading to the extracranial venous systems. To avoid postoperative nerve palsy, the side of the anterior condylar vein in the hypoglossal canal should not be densely packed with coils. Evaluating the angioarchitecture using the selective three-dimensional angiography and tomographic imaging greatly helps to determine the target and strategy of endovascular treatment for these DAVF.

Endovascular Treatment for Dural Arteriovenous Fistula of the Anterior Condylar Confluence Involving the Anterior Condylar Vein

Anterior condylar confluence (ACC) dural arteriovenous fistula (AVF) is a rare anomaly. We describe two cases of ACC dural AVF involving the anterior condylar vein that were successfully treated with selective transvenous coil embolization. The first patient presented with headache and right pulse-synchronous tinnitus, and demonstrated abnormal flow medial to the jugular bulb within the right hypoglossal canal on source image of magnetic resonance angiography (MRA). Arterioangiography disclosed a dural AVF in this area, supplied mainly by the meningeal branches of the bilateral ascending pharyngeal artery. We diagnosed ACC dural AVF involving the anterior condylar vein and transvenous embolization was successfully performed. The second patient presented with right pulse-synchronous tinnitus. Views of source image of MRA and arterioangiography were similar to the first case and, again, transvenous embolization was successfully performed. ACC dural AVF is a rare condition and knowledge of the anatomy of the venous system around the craniocervical junction is required for successful treatment.