Radiological and Morphometric Study of the Emissary Foramens and Canal in the Posterior Cranial Fossa of the Human Skull with Its Neurosurgical Significance.

Objective The posterior condylar canals (PCCs), posterior condylar veins (PCVs), occipital foramen (OF), and occipital emissary vein (OEV) are potential anatomical landmarks for surgical approaches through the lateral foramen magnum. We performed the study to make morphometric and radiological analyses of the various emissary foramens and vein in the posterior cranial fossa. Methods Morphometric study were performed on 95 dry occipital bones and radiological analyses on computed tomography (CT) angiography images of 150 patients. The number of OFs on both sides was recorded and PCC length and mean diameters of the internal and external orifices of PCC were measured for bony specimens. Prevalence of PCV and PCV size was investigated using CT angiography. Results Mean PCC length was higher in the left side (9.85 ± 2.5). Mean diameter of the internal orifice and the external orifice diameter were almost the same. The majority of PCCs (75-79.33%) had 2 to 5 mm diameter; only 4 to 9.2% were small in size (< 2 mm). In CT angiography, PCV was not identified in 23 (15.33%) patients. PCVs were located bilaterally in 105 (70%) and unilaterally in 22 (20.5%) patients. Only 11.3% of PCVs were large in size (> 5 mm), 80% of PCVs were medium sized (2-5 mm), and 8.6% were small sized (< 2 mm). Conclusion Normal values of OF, PCC, PCV, and OEV could serve as a future reference for the understanding of the physiology of craniocervical venous drainage, which is necessary to avoid surgical complications and can also serve as a guide to surgical interventions for pathologies of the posterior cranial fossa, such as tumors and injuries.

Aberrant drainage of posterior condylar emissary vein and abnormal orifice of hypoglossal canal: surgical implications in the transcondylar fossa approach for VA-PICA junction aneurysm.

BACKGROUND: The posterior condylar emissary vein (PCEV) and posterior condylar canal (PCC) are anatomical landmarks for identifying important structures like jugular tubercle and occipital condyle in surgical approach to the foramen magnum and condylar fossa. Several anatomical variations have been described. Drainage into the jugular bulb is found to be commonest. METHOD: A 70-year-old patient with unruptured vertebral artery-posterior inferior cerebellar artery (PICA) junction aneurysm-underwent surgical clipping via transcondylar fossa approach. RESULT: Preoperative computed tomography demonstrated an abnormal communication existed between the left-sided PCC and hypoglossal canal (HC). The PCEV was identified draining into a dilated venous channel/pouch at the "hip" of sigmoid sinus (junction of sigmoid sinus and jugular bulb). Intra-operatively, an occipital artery-PICA bypass was performed. The PCEV was skeletonized, coagulated, and divided to achieve hemostasis. The lateral and cranial drilling around PCC was successful at safeguarding the underlying contents of HC (in medial and caudal extent). CONCLUSION: Preoperative angiography and detailed morphometric analysis of the PCC were helpful in planning surgical approach-identifying and controlling the PCEV, and skeletonization of the PCC without compromising the hypoglossal nerve and anterior condylar emissary vein.

The Forgotten Intermediate Condylar Canal: Anatomic Study with Application to Skull Base Surgery.

BACKGROUND: The intermediate condylar canal, which lies lateral to the occipital condyles and medial to the jugular foramen, is rarely mentioned in textbooks, even those devoted to the skull base. Therefore the present anatomic study was performed to better elucidate these structures. METHODS: We studied 100 adult skulls (200 sides) to better understand the prevalence and anatomy of the intermediate condylar canal. RESULTS: An intermediate canal was found on 6 of 200 sides (3%). On average, these canals traveled 7.1 mm lateral to the occipital condyle and had a mean of 2.2 mm posteromedial to the jugular foramen. Anteriorly, these canals opened into the external surface of the hypoglossal canal and, when present, were just medial to a paracondylar process for which there was a strong positive correlation. The length of the canals ranged from 5 to 7.8 mm. In all, there were 3 partial canals and 3 complete canals. One left canal communicated anteriorly at the confluence of the inferior opening of a septated (bifurcated) hypoglossal canal and an unnamed foramen medial to the jugular foramen. These canals were distinct from posterior condylar canals when the latter was present. CONCLUSIONS: Knowledge of the anatomic variants at the base of the skull may help minimize complications during surgical procedures that employ a paracondylar or transcondylar approach or approaches to the jugular foramen.

Transarterial and Transvenous Embolization for Posterior Condylar Canal Dural Arteriovenous Fistula.

Objective: Posterior condylar canal dural arteriovenous fistula (PCC DAVF) is extremely rare, with only four previously reported cases in the English literature. Cases may present tinnitus and radiculopathy. In cases where the drainer is around the brainstem, subarachnoid and intraventricular hemorrhages (IVHs) may occur. We describe the clinical presentation, angiographic imaging, and endovascular treatment strategy of a PCC DAVF. Case Presentation: A 30-year-old woman presented to our hospital with tinnitus and stiffness of the shoulder. Neuroimaging studies showed DAVF with fistulous points around right PCC consisted of a high-flow shunt, fed mainly by the occipital artery, and drained to the suboccipital cavernous sinus (SCS) and internal jugular vein. The lesion was treated with a combination of transvenous coil embolization and transarterial Onyx injection. The patient recovered immediately after intervention and had no neurological deficits in the follow-up visit. Conclusion: In this case, endovascular treatment was performed safely without recurrence so far. A strategy combining transvenous coil embolization and transarterial Onyx injection may be an effective treatment for PCC DAVF with high-flow shunt. Further case accumulation is desired.

Posterior condylar canal dural arteriovenous fistula as a rare cause of glossopharyngeal neuralgia: A case report.

BACKGROUND: The symptoms of dural arteriovenous fistula (dAVF) vary according to the location of the fistula and the pattern of venous drainage. Here, we report the case of a patient with a dAVF-induced glossopharyngeal neuralgia. CASE DESCRIPTION: We report a case of a patient with right glossopharyngeal neuralgia caused by a posterior condylar canal (PCC) dAVF. The glossopharyngeal neuralgia was accompanied by persistent tinnitus and repetitive right side otalgia, as well as ipsilateral shoulder and throat pain, lasting for about 30 s. However, there were no specific findings on otoscopic examination. Cranial magnetic resonance imaging was performed to determine the cause of the symptoms, and a right PCC dAVF was observed. The dAVF was successfully obliterated using transvenous coil embolization. After embolization, the patient's symptoms were completely resolved. CONCLUSION: Although glossopharyngeal neuralgia caused by dAVF is rare, it can present due to intracranial lesions located adjacent to the glossopharyngeal nerve or vagus nerve. Brain MRI is therefore required to identify secondary causes in all patients with glossopharyngeal neuralgia.

Arteriovenous fistula of the clival diploic vein associated with arteriovenous fistula of the posterior condylar canal.

We herein report a rare case of a patient with a clival diploic vein arteriovenous fistula (AVF) associated with a posterior condylar canal AVF and discuss the radiological features of clival diploic vein AVF during decision-making on treatment strategies. A 69-year-old male patient with one-year history of pulsatile tinnitus was evaluated with magnetic resonance angiography, which revealed a dilated venous structure. Digital subtraction angiography revealed AVFs located in the clivus and posterior condylar canal. The clival diploic vein AVF was fed by the right internal maxillary artery and the petrous branch of middle meningeal artery and shed to the posterior condylar canal only through an intraosseous vein in the jugular tubercle. Although a catheter could not be navigated into the venous pouch in the clivus, the AVFs were successfully obliterated by transvenous embolization of the venous pouch in the posterior condylar canal.

A Case of the So-Called Posterior Condylar Canal Dural Arteriovenous Fistula with an Osseous Shunt.

Objective: The authors describe a case of the so-called dural arteriovenous fistula (DAVF) around the posterior condylar canal (PCC). Case Presentation: A 71-year-old woman presented with pulse-synchronous bruit on the left side. Conventional DSA demonstrated the following: There were many feeders, including the ascending pharyngeal artery (APA), the occipital artery (OA), and the vertebral artery (VA), to the DAVF around the PCC. Shunt flow from the posterior condylar vein (PCV) drained the suboccipital cavernous sinus (SCS) and sigmoid sinus (SS), and there was venous reflux into the inferior petrosal sinus (IPS). The patient was diagnosed with PCC DAVF and underwent transvenous embolization (TVE) with coils. Intraoperative 3D-rotational angiography (RA) and axially reconstructed images revealed an osseous shunt within the occipital bone adjacent to the PCC. The arteriovenous (AV) shunt and other symptoms disappeared after occluding the drainage route from the osseous shunt to the PCV. Conclusion: There are only three previous reports of PCC DAVF, being rare. However, no report clearly described the shunt point of PCC DAVF. 3D-RA and axially reconstructed images were useful to find and treat the shunt point.

The condylar canal and emissary vein-a comprehensive and pictorial review of its anatomy and variation.

The condylar canal and its associated emissary vein serve as vital landmarks during surgical interventions involving skull base surgery. The condylar canal serves to function as a bridge of communication from the intracranial to extracranial space. Variations of the condylar canal are extremely prevalent and can present as either bilateral, unilateral, or completely absent. Anatomical variations of the condylar canal pose as a potential risk to surgeons and radiologist during diagnosis as it could be misinterpreted for a glomus jugular tumor and require surgical intervention when one is not needed. Few literature reviews have articulated the condylar canal and its associated emissary vein through extensive imaging. This present paper aims to further the knowledge of anatomical variations and surgical anatomy involving the condylar canal through high-quality computed tomography (CT) images with cadaveric and dry bone specimens that have been injected with latex to highlight emissary veins arising from the condylar canal.

Management of a rare case of posterior condylar canal dural arteriovenous fistula presenting with subarachnoid haemorrhage: A case report and review of literature.

Posterior condylar canal dural arteriovenous fistula (PCC dAVF) is a rare entity with only three cases having been reported so far in the English literature. We describe the clinical presentation, imaging, and endovascular management of an elderly man with left PCC dAVF presenting with subarachnoid haemorrhage (SAH). Endovascular management of such cases requires thorough understanding of the vascular anatomy around the craniovertebral junction (CVJ) and variable bridging vein draining patterns. The fistula in our case was fed by the posterior meningeal branch of the left vertebral artery and was draining through a dilated and tortuous medullary bridging vein into the antero-lateral pontomedullary venous system. Transarterial glue embolisation was performed with complete exclusion of the fistula and venous pouches. The patient developed intractable hiccough and left-sided facial pain on the second post-procedural day, and MRI showed focal diffusion restriction in the left dorso-lateral medulla. He recovered completely after a short course of steroids.

The role of alternative anastomosis sites in occipital artery-posterior inferior cerebellar artery bypass in the absence of the caudal loop using the far-lateral approach.

OBJECTIVE Occipital artery-posterior inferior cerebellar artery (OA-PICA) bypass is a technically challenging procedure for posterior fossa revascularization. The caudal loop of the PICA is considered the optimal site for OA-PICA anastomosis, however its absence can increase the technical difficulty associated with this procedure. The use of the far-lateral approach for accessing alternative anastomosis sites in OA-PICA bypass in patients with absent or unavailable caudal loops of PICA is evaluated. METHODS A morphometric analysis of OA-PICA bypass with anastomosis on each segment of the PICA was performed on 5 cadaveric specimens through the conventional midline foramen magnum and far-lateral approaches. The difficulty level associated with anastomoses at each segment was qualitatively assessed in each approach for exposure and maneuverability by multiple surgeons. A series of 8 patients who underwent OA-PICA bypass for hemodynamic ischemia or ruptured dissecting posterior fossa aneurysms are additionally reviewed and described, and the clinical significance of the caudal loop of PICA is discussed. RESULTS Anastomosis on the caudal loop could be performed more superficially than on any other segment (p < 0.001). A far-lateral approach up to the medial border of the posterior condylar canal provided a 13.5 ± 2.2-mm wider corridor than the conventional midline foramen magnum approach, facilitating access to alternative anastomosis sites. The far-lateral approach was successfully used for OA-PICA bypass in 3 clinical cases whose caudal loops were absent, whereas the midline foramen magnum approach provided sufficient exposure for caudal loop bypass in the remaining 5 cases. CONCLUSIONS The absence of the caudal loop of the PICA is a major contributing factor to the technical difficulty of OA-PICA bypass. The far-lateral approach is a useful surgical option for OA-PICA bypass when the caudal loop of the PICA is unavailable.

The anatomical perspective of human occipital condyle in relation to the hypoglossal canal, condylar canal, and jugular foramen and its surgical significance.

BACKGROUND: The transcondylar approach (TCA) has gained importance in recent era which enables shorter and direct route to access the lesions ventral to the brainstem. The important step in this approach is resection of the occipital condyle (OC). The detailed knowledge of bony anatomy of OC and its relation to the hypoglossal canal (HC), condylar canal (CC), and jugular foramen (JF) is very important to avoid any iatrogenic injury during craniovertebral surgeries. The aim of the present study is to conduct a morphometric and morphological study and note the variations of the OC and the structures surrounding it in North Indian population. MATERIALS AND METHODS: The study was carried out on 100 OC. Morphometric measurements of OC and the distances of HC and JF from the posterior end of OC were noted. In addition, the extent of the HC and JF in relation to OC, presence or absence of CC, shape of the OC, and its articular facet were also noted. RESULTS: The incidence of short OC was seen in 13% skulls. The most common shape of OC was oval or rhomboid. Even though the articular facet was convex in majority of skulls but flat (10%) and concave (1%) were also observed. The external and internal distance of HC from the posterior end of OC was13.83 mm and 10.66 mm on the right side and 15.02 mm and 11.89 mm on the left side. The OC was related in its middle 1/3 to the HC in 15% skulls and to the whole extent of JF in 3% skulls. Thirty-four percent skulls displayed the septa in the HC. The CC was present bilaterally in 38% skulls and unilaterally in 40% skulls. CONCLUSION: The OC and related structures such as HC, CC, and JF are likely to have variations in respect to morphometry and morphology. This study may prove helpful to neurosurgeons operating in this field, especially during TCA where neurovascular structures emerging from these canals and foramen are more vulnerable to injury.

An unusual anatomic variation of the jugular foramen with doubled posterior condylar canal / Una variación anatómica inusual del foramen yugular con canal condilar posterior duplicado

A case of unusual anatomical variation of the jugular foramen (JF) with doubled posterior condylar canal (PCC) is reported. According to the presence of bridging, the JF can be defined as Type I (one septation, two compartments) on the right side and Type IV (three septations, four compartments) on the left side. The dome of the jugular fossa is present on the right, absent on the left. The jugular foramen shows a canal-like structure with an external and an internal opening. The lengths of the longest and widest axes of the JFs are measured as 21.93 x 16.56 mm on the right and 16.75 x 15.14 mm on the left side. The right JF is larger. The PCC is doubled on the right side and there is only one on the left side. It is essential not only to know compartments per se but also to know the structures passing through the compartments, in order to achieve desired surgical outcomes and avoid complications.

Es reportado el caso de una inusual variación anatómica del foramen yugular (FY), con el canal condilar posterior duplicado (CCP). De acuerdo con la presencia de los puentes, el FY se puede definir como Tipo I (una tabicación, dos compartimientos) en el lado derecho y Tipo IV (tres tabiques, cuatro compartimientos) en el lado izquierdo. El domo de la fosa yugular está presente en el lado derecho, y ausente en el izquierdo. El foramen yugular mostró una estructura igual a un canal con una apertura externa y otra interna. Las longitudes de los ejes más largos y anchos de la FY fueron 21,93x16,56mm al lado derecho y 16,75x15,14mm al lado izquierdo. El FY derecho fue más grande. El CCP se observó duplicado en el lado derecho y único en el lado izquierdo. Es esencial no sólo conocer los compartimientos en sí, sino también las estructuras que pasan a través de los compartimientos con el fin de lograr los resultados deseados y evitar las complicaciones quirúrgicas.