Composition of encephalic arteries and origin of the basilar artery are different between vertebrates

Intracranial arterial anatomy is lacking for most mammalian and non-mammalian model species, especially concerning the origin of the basilar artery (BA). Enhancing the knowledge of this anatomy can improve animal models and help understanding anatomical variations in humans. We have studied encephalic arteries in three different species of birds and eight different species of mammals using formalin-fixed brains injected with arterial red latex. Our results and literature analysis indicate that, for all vertebrates, the internal carotid artery (ICA) supplies the brain and divides into two branches: a cranial and a caudal branch. The difference between vertebrates lies in the caudal branch of the ICA. For non-mammalian, the caudal branch is the origin of the BA, and the vertebral artery (VA) is not involved in brain supply. For mammals, the VA supplies encephalic arteries in two different ways. In the first type of organization, mostly found in ungulates, the carotid rete mirabile supplies the encephalic arteries, the caudal branch is the origin of the BA, and the VA is indirectly involved in carotid rete mirabile blood supply. The second type of encephalic artery organization for mammals is the same as in humans. The caudal branch of the ICA serves as the posterior communicating artery, and the BA originates from both VAs. We believe that knowledge of comparative anatomy of encephalic arteries contributes to a better understanding of animal models applicable to surgical or radiological techniques. It improves the understanding of rare encephalic variations that may be present in humans.

Fascinating wonderful network: Rete mirabile of the maxillary artery in cats - minireview

Cats are one of the most common companion animals, and they differ from dogs in several important ways. Considering the central importance of anatomy in high-quality medicine, the treatment of the feline mandible, mostly during intraoral procedures requiring general anaesthesia, has many important features. In cats, the major artery of the brain is the maxillary artery that forms unique structure - the rete mirabile. The rete mirabile is a plexus like vascular structure that lies extracranially and communicates with brain arterial circle through the orbital fissure. The development of the brain vasculature is different in cats, and it includes obliteration mechanisms of the internal carotid artery. The course of the maxillary artery that forms the rete mirabile has a strong relationship to the angular process of the mandible. Emphasis should be placed on manipulation with the feline mandible, especially during open-mouth procedures, as mistakes can lead to blindness, deafness, and central neurological disorders due to compression of the maxillary artery by the angular process of the mandible. This paper focuses on the anatomy and function of the blood supply to the brain, which is very specific in domestic cats and other felids.

The Pterygosphenoidal Triangle: Surgical Anatomy and Case Series in Endoscopic Endonasal Skull Base Surgery

BACKGROUND

Safe exposure of the lacerum segment of the carotid artery remains a challenge in endoscopic endonasal surgery.

OBJECTIVE

To introduce the pterygosphenoidal triangle as a novel and reliable landmark for facilitating access to the foramen lacerum.

METHODS

Fifteen colored silicone-injected anatomic specimens were dissected using an endoscopic endonasal approach to the foramen lacerum region in a stepwise manner. Twelve dried skulls were studied and 30 high-resolution computed tomography scans were analyzed to measure the borders and angles of the pterygosphenoidal triangle. Surgical cases incorporating the foramen lacerum exposure between July 2018 and December 2021 were reviewed to provide surgical outcomes of the proposed surgical technique.

RESULTS

The pterygosphenoidal triangle is delineated by the pterygosphenoidal fissure medially and the vidian nerve laterally. The palatovaginal artery is located at the base of the triangle anteriorly, while the apex is formed by the pterygoid tubercle posteriorly, which leads to the anterior wall of the foramen lacerum and lacerum internal carotid artery. In the reviewed surgical cases, 39 patients underwent 46 foramen lacerum approaches for resection of pituitary adenoma (12 patients), meningioma (6 patients), chondrosarcoma (5 patients), chordoma (5 patients), or other lesions (11 patients). There were no carotid injuries or ischemic events. Near-total resection was achieved in 33 (85%) of 39 patients (gross-total in 20 [51%]).

CONCLUSION

This study details the pterygosphenoidal triangle as a novel and practical anatomic surgical landmark for safe and effective exposure of the foramen lacerum in endoscopic endonasal surgery.

Skull base dural reflection models: tool for teaching neuroanatomy at resource-scarce centers

Skull base dural reflections are complex, and along with various ligaments joining sutures of the skull base, are related to most important vessels like internal carotid arteries (ICA), vertebral arteries, jugular veins, cavernous sinus, and cranial nerves which make surgical approaches difficult and need thorough knowledge and anatomy for a safe dissection and satisfactory patient outcomes. Cadaver dissection is much more important for the training of skull base anatomy in comparison to any other subspecialty of neurosurgery; however, such facilities are not available at most of the training institutes, more so in low- and middle-income countries (LMICs). A glue gun (100-Watt glue gun, ApTech Deals, Delhi, India) was used to spread glue over the superior surface of the bone of the skull base over desired area (anterior, middle, or lateral skull base). Once glue was spread over the desired surface uniformly, it was cooled under running tap water and the glue layer was separated from the skull base. Various neurovascular impressions were colored for ease of depiction and teaching. Visual neuroanatomy of the inferior surface of dural reflections of the skull base is important for understanding neurovascular orientations of various structures entering or exiting the skull base. It was readily available, reproducible, and simple for teaching neuroanatomy to the trainees of neurosurgery. Skull base dural reflections made up of glue are an inexpensive, reproducible item that may be used for teaching neuroanatomy. It may be useful for trainees and young neurosurgeons, especially at resource-scarce healthcare facilities.

Site of Origin of the Ophthalmic Artery Influences the Risk for Retinal Versus Cerebral Embolic Events

BACKGROUND

Embolic events leading to retinal ischemia or cerebral ischemia share common risk factors; however, it has been well documented that the rate of concurrent cerebral infarction is higher in patients with a history of transient ischemic attack (TIA) than in those with monocular vision loss (MVL) due to retinal ischemia. Despite the fact that emboli to the ophthalmic artery (OA) and middle cerebral artery share the internal carotid artery (ICA) as a common origin or transit for emboli, the asymmetry in their final destination has not been fully explained. We hypothesize that the anatomic location of the OA takeoff from the ICA may contribute to the differential flow of small emboli to the retinal circulation vs the cerebral circulation.

METHODS

We report a retrospective, comparative, case-control study on 28 patients with retinal ischemia and 26 patients with TIA or cerebral infarction caused by embolic events. All subjects underwent either computed tomography angiography or MRA. The location of the ipsilateral OA origin off the ICA was then graded in a blinded fashion and compared between cohorts. Vascular risk factors were collected for all patients, including age, sex, hypertension, hyperlipidemia, arrhythmia, diabetes, coronary artery disease, and smoking.

RESULTS

We find that in patients with retinal ischemia of embolic etiology, the ipsilateral OA takeoff from the ICA is more proximal than in patients with cerebral infarcts or TIA (P = 0.0002). We found no statistically significant differences in demographic, vascular, or systemic risk factors.

CONCLUSIONS

We find that the mean anatomical location of the OA takeoff from the ICA is significantly more proximal in patients with MVL due to retinal ischemia compared with patients with TIA or cerebral ischemia. This finding contributes significantly to our understanding of a long observed but poorly understood phenomenon that patients with MVL are less likely to have concurrent cerebral ischemia than are patients with TIA.

Anatomic Nuances of the Ophthalmic Artery Origin from a Ventral Viewpoint: Considerations and Implications for Endoscopic Endonasal Surgery

BACKGROUND

The origin of the ophthalmic artery is within the surgical field of endoscopic endonasal approaches (EEAs) to the suprasellar and parasellar regions. However, its anatomy from the endoscopic point-of-view has not been adequately elucidated.

OBJECTIVE

To highlight the anatomy of the ophthalmic artery origin from an endoscopic endonasal perspective.

METHODS

The origin of the ophthalmic artery was studied bilaterally under endoscopic visualization, after performing transplanum/transtubercular EEAs in 17 cadaveric specimens (34 arteries). Anatomic relationships relevant to surgery were evaluated. To complement the cadaveric findings, the ophthalmic artery origin was reviewed in 200 "normal" angiographic studies.

RESULTS

On the right side, 70.6% of ophthalmic arteries emerged from the superior aspect, while 17.6% and 11.8% emerged from the superomedial and superolateral aspects of the intradural internal carotid artery, respectively. On the left, 76.5%, 17.6%, and 5.9% of ophthalmic arteries emerged from the superior, superomedial, and superolateral aspects of the internal carotid, respectively. Similar findings were observed on angiography. All ophthalmic arteries emerged at the level of the medial opticocarotid recess. Overall, 47%, 26.5%, and 26.5% of ophthalmic arteries (right and left) were inferolateral, inferior, and inferomedial to the intracranial optic nerve segment, respectively. On both sides, the intracranial length of the ophthalmic artery ranged from 1.5 to 4.5 mm (mean: 2.90 ± standard deviation of 0.74 mm).

CONCLUSION

Awareness of the endoscopic nuances of the ophthalmic artery origin is paramount to minimize the risk of sight-threatening neurovascular injury during EEAs to the suprasellar and parasellar regions.

Preauricular retromandibular trans tympanic plate and styloid process keyhole approach to parapharyngeal lesions: a laboratory study

BACKGROUND

The surgical removal of the infratemporal parapharyngeal lesions (IPL) is challenging due to its anatomical complexity. Previous surgical approaches have often been too invasive and necessitated sacrifice of normal function and anatomical structures, particularly in the retromandibular nerve region. Therefore, we sought to identify an approach corridor to this area that requires less sacrifice and report an innovative approach through a retromandibular fossa route to the IPL.

METHODS

Five cadaveric specimens were dissected bilaterally with a trans-tympanic plate and styloid process approach. These specimens were investigated microanatomically and morphometrically to examine the extent of the approach in the parapharyngeal space. The clinical application of this approach was compared to previous approaches to the IPL used in our clinical series of 20 cases.

RESULTS

Using this novel approach, the inferior alveolar nerve was identified in all specimens, while the chorda tympani and lingual nerve were identified in 6 (60%) and 4 (40%) dissections, respectively. In all specimens, the petrous portion of the internal carotid artery and the exit of the lower cranial nerve were identified. The average length of the exposed lower cranial nerves was 16.6 ± 3.8 mm (range: 11-25 mm).

CONCLUSIONS

The described approach is feasible for accessing the IPL at the retromandibular nerve and is less invasive than conventionally used approaches.

Neurosurgical Anatomy of the Internal Carotid Artery: Magnetic Resonance Imaging Study of the Sellar Region

BACKGROUND

Transsphenoidal surgical approaches involve dissection of the posterior wall of the sphenoid sinus in close proximity to the internal carotid arteries. To reduce the risk of vascular injury, a detailed study of embalmed cadavers' sellae was conducted and found the internal carotid artery approached within 4 mm of the midline in 10% of cases, and the closest intercarotid distance (ICD) occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 82%, 14%, and 4% of cases, respectively. These measurements have not previously been compared with living patients with modern imaging techniques.

METHODS

This study measured the closest ICD of 233 coronal magnetic resonance imaging head scans from 183 patients (male = 88, female = 95) at the cavernous sinus, sphenoid sinus, or supraclinoid segments of the internal carotid artery. ICD at the sphenoid sinus was taken for all scans.

RESULTS

The internal carotid approached within 4 mm of the midline in 1.3% of cases. The closest ICD occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 24.5%, 35.8%, and 39.7%, respectively. Both results were significantly different from previous cadaveric studies (chi-squared tests, P = 1.4 × 10^-4 and P = 6.1 × 10^-8, respectively).

CONCLUSIONS

Surgically relevant measurements of the carotid arteries in the sellar are different in cadavers and living subjects. This is likely due to postmortem changes of surrounding structures. This study suggests clinically relevant anatomic studies using measurements taken from cadaveric specimens be updated with modern imaging techniques taken from living patients.

The approach angle to the interoptic triangle limits surgical workspace when targeting the contralateral internal carotid artery

BACKGROUND

The interoptic triangle (IOT) offers a key access to the contralateral carotid artery's ophthalmic segment (oICA) and its perforating branches (PB), the ophthalmic artery (OA), and the superior hypophyseal artery (SHA). It has been previously reported that the assessment of IOT's size is relevant when attempting approaches to the contralateral oICA. However, previous studies have overseen that, since the oICA is a paramedian structure and a lateralized contralateral approach trajectory is then required, the real access to the oICA is further limited by the approach angle adopted by the surgeon with respect to the IOT's plane. For this reason, we determined the surgical accessibility to the contralateral oICA and its branches though the IOT by characterizing the morphometry of this triangle relative to the optimal contralateral approach angle.

METHODS

We defined the "relative interoptic triangle" (rIOT) as the two-dimensional projection of the IOT to the surgeon's view, when the microscope has been positioned with a certain angle with respect to the midline to allow the maximal contralateral oICA visualization. We correlated the surface of the rIOT to the visualization of oICA, OA, SHA, and PBs on 8 cadavers and 10 clinical datasets, using for the last a 3D-virtual reality system.

RESULTS

A larger rIOT correlated positively with the exposure of the contralateral oICA (R = 0.967, p < 0.001), OA (R = 0.92, p < 0.001), SHA (R = 0.917, p < 0.001), and the number of perforant vessels of the oICA visible (R = 0.862, p < 0.001). The exposed length of oICA, OA, SHA, and number PB observed increased as rIOT's surface enlarged. The correlation patterns observed by virtual 3D-planning matched the anatomical findings closely.

CONCLUSIONS

The exposure of contralateral oICA, OA, SHA, and PB directly correlates to rIOT's surface. Therefore, preoperative assessment of rIOT's surface is helpful when considering contralateral approaches to the oICA. A virtual 3D planning tool greatly facilitates this assessment.

Elastic Statistical Shape Analysis of Biological Structures with Case Studies: A Tutorial

We describe a recent framework for statistical shape analysis of curves and show its applicability to various biological datasets. The presented methods are based on a functional representation of shape called the square-root velocity function and a closely related elastic metric. The main benefit of this approach is its invariance to reparameterization (in addition to the standard shape-preserving transformations of translation, rotation and scale), and ability to compute optimal registrations (point correspondences) across objects. Building upon the defined distance between shapes, we additionally describe tools for computing sample statistics including the mean and covariance. Based on the covariance structure, one can also explore variability in shape samples via principal component analysis. Finally, the estimated mean and covariance can be used to define Wrapped Gaussian models on the shape space, which are easy to sample from. We present multiple case studies on various biological datasets including (1) leaf outlines, (2) internal carotid arteries, (3) Diffusion Tensor Magnetic Resonance Imaging fiber tracts, (4) Glioblastoma Multiforme tumors, and (5) vertebrae in mice. We additionally provide a MATLAB package that can be used to produce the results given in this manuscript.

A comparative study of methods used to generate the arterial fiber structure in a clinically relevant numerical analysis

The advanced constitutive material models of artery wall require the definition of the mean collagen fiber directions in the material configuration. There are several proposed methods; however, it is unclear how much does the fiber structures obtained by these methods differ one from the other and how much this difference may affect the results of the structural analysis of a clinically relevant scenario. Therefore, in this paper, we address this issue by presenting the results of the comparative study of our developed and currently state-of-the-art fiber definition methods. In addition, we present the verification of our developed numerical model that incorporates the extended Holzapfel-Gasser-Ogden (HGO) constitutive material model and the generalized prestressing algorithm (GPA). In the case of the patient-specific internal carotid artery (ICA), the percentage error of the mean fiber directions defined by different methods does not exceed 17.73% (at least 0.05%, at most 81.82%) and has negligible effect on the stress levels, as the percentage error of the mean circumferential Cauchy stress does not exceed 0.1%. Both fiber definition methods produce comparable fiber structure, but our proposed method has an advantage, as it does not depend on method and software used to model the arterial wall mechanics.

The anatomical relation of the extracranial internal carotid artery in the parapharyngeal space

BACKGROUND

The proximity of the internal carotid artery to the pharyngeal wall poses a risk of injury during nasopharyngeal surgery.

OBJECTIVES

The aim of this study was to assess the distances between the extracranial internal carotid artery (ICA) and the pharyngeal wall.

MATERIAL AND METHODS

Measurements were taken on certain levels of the pharynx using computed tomography angiography (angio-CT) scans of 97 patients. One-tailed Student's t-test for independent variables and a comparison of expected values for dependent pairs of observations were applied.

RESULTS

The shortest distance between the ICA and the pharyngeal wall was 1.1 mm. The ICA is closer to the pharyngeal wall at the epiglottis apex level (16.46 ±0.89 mm) than to the Eustachian tube (ET) (19.8 ±0.62 mm) (p < 0.0005). In women, the ICA is closer to the ET (19.44 ±0.78 mm) than in men (20.17 ±0.96 mm) (p = 0.04). In women, the right ICA is closer to the pharyngeal wall than the left ICA at the level of the lower margin of the 2nd cervical corpus vertebra (C2) (right: 17.6 ±1.8 mm; left: 20.7 ±1.7 mm) (p = 0.002) and at the level of the epiglottis apex (right: 15.2 ±1.7 mm; left: 17.4 ±1.4 mm) (p = 0.028). The bifurcation of the common carotid artery (CCA) is higher in men (19.48 ±2.19 mm below the C2) than in women (21.82 ±1.02 mm) (p < 0.001). When the bifurcation is at the level of the epiglottis apex, the ICA is closer to the pharyngeal wall (12.3 ±1.69 mm) than in other cases (16.46 ±0.89 mm) (p = 0.005). In men, the higher the bifurcation is, the closer the ICA is to the pharyngeal wall at the level of the lower margin of the C2 (p = 0.003).

CONCLUSIONS

The risk of ICA incision during surgery differs between the pharyngeal levels, genders and sides of the neck. The ICA may be much closer to the pharyngeal wall than described in the literature.

Relationship between sphenoid sinus volume and protrusion of internal carotid artery and optic nerve: a 3D segmentation study on maxillofacial CT-scans

PURPOSE

Anatomy of sphenoid sinuses has acquired a growing importance with the diffusion of transsphenoidal surgical procedures. A common risk in these practices is the damage of internal carotid artery (ICA) and optic nerve (ON), which may protrude into the sphenoid air cavities. This study aims at analysing the relationships between sphenoid sinuses volume and protrusion of ICA and ON.

METHODS

260 head CT-scans were retrospectively analysed (equally divided among males and females, age range 20-92 years). Volume was segmented through ITK-SNAP software. In addition, the subjects were classified into four groups: no protrusion of any structure (group 1), protrusion of ICA (group 2), protrusion of ON (group 3), protrusion of both ICA and ON (group 4). Possible statistically significant differences in prevalence of the four groups according to gender were assessed through Chi-squared test (p < 0.05). Differences in volume between the four groups were assessed through one-way ANOVA test (p < 0.05), separately for males and females.

RESULTS

Group 1 was the most frequent (40.0%), followed by group 4 (27.7%) and group 2 (18.5%), without any difference according to gender. For what concerns volume, cases of ICA and concomitant ICA + ON protrusion had significantly larger sinuses, whereas isolated ON protrusion did not modify sinus volume.

CONCLUSIONS

Results show that protrusion of ICA is positively related with the volume of sphenoid sinuses, whereas the same relation was not verified for ON: surgeons should accurately consider possible ON protrusion in each case, as it may occur independently from sphenoid sinuses volume.

Visualization of the vidian canal and nerve using magnetic resonance imaging

BACKGROUND AND PURPOSE

Few studies have investigated the vidian nerve (VN) and vidian canal (VC) with the use of magnetic resonance imaging (MRI). The present study aimed to characterize the VC and VN using MRI.

MATERIALS AND METHODS

A total of 91 patients underwent thin-sliced, contrast MRI. The course of the VC and VN and the relationships with relevant structures were analyzed.

RESULTS

The VC was identified in 95% of axial images on the right side and in 93% on the left. The course of the VC was delineated in 99% of serial coronal images on both sides. The VN location in the VC was highly variable. The course of the VC and transmitting VN was delineated in 95% of sagittal images on the right side and in 91% on the left. The mean length of the VC was 19.8 mm on the right side and 19.3 mm on the left. Topographical relationships between the anterior genu of the petrous internal carotid artery and the posterior end of the vidian canal could be classified into three types. Of these, the type terminating at the level of the petrous carotid was the most predominant, comprising 76% of 182 sides. The course of the VC and transmitting VN could be classified into four types. The straight type was the most predominant and was found in 41%.

CONCLUSIONS

The VC and transmitting VN are structures with variable morphologies. Contrast MRI is useful for delineating the VC and VN.

The Face – A Vascular Perspective. A literature review

Vascular supply is key for maintenance of healthy tissue conditions but also with regard to healing following trauma or therapeutic interventions. The face is probably the most exposed part of the body and any changes of vascularity are readily visible (skin blanching, ecchymosis, hematoma, edema). With regard to the arterial supply, all vessels reaching the facial skin originate from the bilateral common carotid arteries. The ophthal­mic artery is considered the major arterial shunt between the internal and external carotid artery systems. Main arterial contributors to the face include the facial, transverse facial, and infraorbital arteries. In general, homonymous veins accompany the arteries, but there are some exceptions (inferior ophthalmic vein, retromandibular vein). Furthermore, the facial vein demonstrates a consistently more posterior course compared to the facial artery. Lymphatic vessels including lymph nodes play an important role for facial drainage.

Anatomical and histological study of the deep neck fasciae: does the alar fascia exist?

PURPOSE

The aim of this study was to determine whether the alar fascia is a distinct layer of the deep cervical neck fasciae. The present study also aimed to elucidate the anatomical limits of this fascia.

METHODS

Neck dissections of ten adult cadavers were performed, layer by layer, in the retropharyngeal region, under a powered operating microscope. Detailed dissections revealed the anatomical limits of the deep neck fasciae. Histological descriptions were also performed on large tissue samples collected from three cervical dissections.

RESULTS

In the ten dissections, three layers of fascia were identified and dissected in the retropharyngeal region: a visceral fascia, a prevertebral fascia and an alar fascia. The alar fascia appeared like a connecting band derivative of the visceral fascia, between both vascular sheaths. It fused completely with the visceral fascia anteriorly at the level of T2 and with the prevertebral fascia posteriorly at the level of C1. No sagittal connection between the visceral fascia and the prevertebral fascia was identified. The stained histological sections confirmed the presence of the visceral and prevertebral fasciae at the oropharyngeal level, with a third intermediate layer closely connected with the visceral fascia.

CONCLUSION

The alar fascia is a layer of the cervical neck fascia connected with the visceral fascia from C1 to T2 levels. The anatomical limits of this alar fascia and its relationships with the internal carotid artery are important in the surgical management and the prognosis of deep neck infections and retropharyngeal lymph node metastases.

Autoregulating Cerebral Tissue Selfishly Exploits Collateral Flow Routes Through the Circle of Willis

OBJECTIVE

Ischemic stroke is a leading cause of death and disability. Autoregulation and collateral blood flow through the circle of Willis both play a role in preventing tissue infarction. A steady-state model of the cerebral arterial network was used to investigate the interaction of these mechanisms when autoregulation is impaired ipsilateral to an occluded artery.

MATERIALS AND METHODS

Twelve structural variants of the circle of Willis were modelled with left internal carotid artery occlusion and coupled with (1) a passive model of the cerebral vascular bed, (2) a steady-state model of an autoregulating cerebral vascular bed, and (3) a model in which the contralateral hemisphere autoregulates and the ipsilateral hemisphere does not.

RESULTS

Results showed that if the autoregulatory response is impaired ipsilaterally, then, in the autoregulating hemisphere, cerebral flows are preserved at the expense of those on the ipsilateral side.

CONCLUSIONS

Thus, although autoregulation is an essential facilitator of collateral flow through the circle of Willis, contralateral autoregulation can exacerbate flow reductions if not balanced by the same response in the vascular beds on the ipsilateral side. The status of the autoregulatory response in both hemispheres can strongly influence cerebral blood flows and tissue survival and should, therefore, be monitored in stroke.

Nonmetric analysis of caroticoclinoid foramen in foothills of Himalayas: Its clinicoanatomic perspective

OBJECTIVE OF THE STUDY

Study was conducted to evaluate the incidence of caroticoclinoid foramen in north Indian population. Authors have also endeavoured to discuss its clinical and embryological implications.

MATERIALS AND METHODS

Study was conducted on 108 dry human skulls in department of anatomy SGRR medical college, Dehradun. Incidence of caroticoclinoid foramen was evaluated in accordance with side.

RESULTS

A percentage of 22.22 skulls presented with the caroticoclinoid foramen with maximum incidence of unilateral and incomplete type. Incidence revealed no bias towards side.

CONCLUSION

Anatomical knowledge about CCF may be helpful to radiologists and neurosurgeons in providing an additional insight into the diagnosis and management of various pathologies around sellar region.

The impact of the cochlear-carotid interval on tinnitus perception

PURPOSE

We hypothesized that the cochlear-carotid interval (CCI), which is defined as the smallest distance along the petrous segment of the internal carotid artery and basal turn of cochlea, may be associated with direct stimulation of hair cells, thereby affecting tinnitus perception. The aim of this study was to investigate the relationships between the CCI, tinnitus perception, and accompanying hearing loss in patients with tinnitus.

METHODS

The CCI on both sides was measured independently by two observers from the temporal 3D b-FFE MR images of 25 patients with tinnitus and 20 age/gender matched control subjects. The relationships between CCI, tinnitus visual analog scale (VAS), and tinnitus handicap inventory (THI) were investigated.

RESULTS

CCI ranged 0.2-5.6 mm (1.9 ± 1.5) on the right and 0.1-5.4 mm (2.2 ± 1.6) on the left side in the patient group and 0.5-5.4 (1.9 ± 1.4) mm on the right and 0.3-6.7 (2.3 ± 1.7) on the left side in the control group. The differences between the two groups were not statistically significant (p > 0.05). CCI showed a strong negative correlation with THI and VAS scores on both sides. Correlation of audiologic findings with CCI revealed a significant negative correlation with pure tone average of the ipsilateral ear most affectedly at high frequencies.

CONCLUSION

The strong negative correlation of CCI with tinnitus-related distress and accompanying sensorineural hearing loss predominantly at high frequencies suggests that further studies on patients with tinnitus that focus on this small area may help to improve the knowledge of tinnitus pathophysiology.

Choroidal thickness and retinal vascular caliber correlations with internal carotid artery Doppler variables

PURPOSE

Decreased retinal arteriolar caliber and increased retinal venular caliber have been associated with increased cardiovascular mortality. This study aimed to evaluate correlations of choroidal thickness and retinal vascular caliber measurements with internal carotid artery (ICA) Doppler ultrasound variables.

METHODS

In this cross-sectional and observational study, 43 eyes and ICAs of 43 healthy volunteers were examined. Spectral domain optical coherence tomography was used to measure subfoveal choroidal thickness (SFCT) and retinal vascular caliber. The ICA Doppler ultrasonographic parameters were diameter, flow volume, peak-systolic velocity, end-diastolic velocity, resistance index (RI), and pulsatility index (PI).

RESULTS

Negative correlations emerged between ICA RI and SFCT (p = 0.017, r = -0.36) as well as between ICA PI and retinal arteriolar caliber (p = 0.015, r = -0.37). A negative linear correlation appeared between ICA diameter and SFCT (p = 0.005, r = -0.42), although ICA diameter and flow volume showed no association with retinal vessel caliber (p > 0.05).

CONCLUSIONS

Choroidal thickness is negatively correlated with ICA diameter and ICA RI, while retinal arteriolar caliber is inversely related with ICA PI in normal volunteers.

Safe Corridor to Access Clivus for Endoscopic Trans-Sphenoidal Surgery: A Radiological and Anatomical Study

PURPOSE

Penetration of the clivus is required for surgical access of the brain stem. The endoscopic transclivus approach is a difficult procedure with high risk of injury to important neurovascular structures. We undertook a novel anatomical and radiological investigation to understand the structure of the clivus and neurovascular structures relevant to the extended trans-nasal trans-sphenoid procedure and determine a safe corridor for the penetration of the clivus.

METHOD

We examined the clivus region in the computed tomographic angiography (CTA) images of 220 adults, magnetic resonance (MR) images of 50 adults, and dry skull specimens of 10 adults. Multiplanar reconstruction (MPR) of the CT images was performed, and the anatomical features of the clivus were studied in the coronal, sagittal, and axial planes. The data from the images were used to determine the anatomical parameters of the clivus and neurovascular structures, such as the internal carotid artery and inferior petrosal sinus.

RESULTS

The examination of the CTA and MR images of the enrolled subjects revealed that the thickness of the clivus helped determine the depth of the penetration, while the distance from the sagittal midline to the important neurovascular structures determined the width of the penetration. Further, data from the CTA and MR images were consistent with those retrieved from the examination of the cadaveric specimens.

CONCLUSION

Our findings provided certain pointers that may be useful in guiding the surgery such that inadvertent injury to vital structures is avoided and also provided supportive information for the choice of the appropriate endoscopic equipment.

A new production method of elastic silicone carotid phantom based on MRI acquisition using rapid prototyping technique

In vitro experimental simulations of blood fluid in carotid artery require ideal phantoms that are as precise as possible. The purpose of this work is to demonstrate a method for carotid phantom fabrication by rapid prototyping technique (RP). By using 3D reconstructed projection of the 3D time-of-flight (TOF) Magnetic Resonance Imaging (MRI) sequence, a 12.5 cm multi-dimensional spatial structure of a carotid artery has been set up. Y-shaped and patient specific models have been generated respectively using silicone elastomer, which has a high resilience and a good tensile strength. The final patient specific model has internal carotid artery (ICA) with a highly spiraling siphon and an external carotid artery (ECA). Elastic properties of carotid walls have also been evaluated by Young's elastic modulus test and dynamic behaviors in optical and echography simulation experiments.

Endoscopic, endonasal variability in the anatomy of the internal carotid artery

BACKGROUND

Classic three-dimensional schemas of the internal carotid artery (ICA) for transcranial approaches do not necessarily apply to two-dimensional endoscopic views. Modifying an existing ICA segment classification, we define endoscopic orientation for the lacerum (C3) to clinoid (C5) segments through an endonasal approach.

METHODS

In 20 cadaveric heads, we classified endoscopic appearance based on shape and angulation of C3 to C5 segments. Distances were measured between both arteries, and between the ICA and pituitary gland.

RESULTS

We identified 4 common ICA patterns: types I through III matched side-to-side, whereas type IV was asymmetric. In 80% of specimens, the pituitary gland had direct contact with the ICA. In 20% of specimens, a space existed between the pituitary gland and the cavernous segment. Access to the posterior aspect of the cavernous sinus medial to the cavernous segment was possible without retraction of the artery or pituitary gland. Spaces between the lacerum and cavernous segments were trapezoid (80%) and hourglass (20%).

CONCLUSIONS

Distinguishing which ICA type courses between the lacerum and clinoid segments can help clarify the relationships between the artery and its surrounding structures during endoscopic approaches. Adapting the classic terminology of ICA segments provided consistency of endoscopic relevance, defined potential endoscopic corridors, and highlighted the critical step of arterial contact.

Correlating the length of internal carotid artery stenosis to the technique of endarterectomy and anesthesia used

A consensus correlating the length of the internal carotid artery stenosis (short vs. long) to the preferred Endarterectomy (Conventional Vs. Eversion) and type of anesthesia (General Vs. cervical blockade) implemented has not yet been met. In a collaboration study between two hospitals in Germany and Georgia, 215 patients were analyzed and stratified into 3 groups according to length of stenosis, surgical technique and type of anesthesia used. In this series, for eversion endarterectomy with cervical blockade, non-neurological complications commenced at 1,78%. For conventional endarterectomy performed under general anesthesia, patients with a short stenosis had no postoperative complications whatsoever, whereas the incidence rate for various neurological deficits was 2,7% for long stenosis. In case of short stenosis of the internal carotid artery, eversion endarterectomy with cervical block, seems to be an optimal choice. Whereas for long stenosis, conventional endarterectomy under general anesthesia is a more suitable option.

Identification of the internal carotid artery at the superior part of the cavernous sinus during endoscopic endonasal cavernous sinus tumor surgery

BACKGROUND

Identification of the internal carotid artery (ICA) is essential for successful endoscopic endonasal cavernous sinus tumor surgery. This study aimed to develop a method for identifying the ICA in cavernous sinus tumors at the superior part of the cavernous sinus.

METHODS

Ten fresh cadavers were studied with a 4-mm 0° and 30° endoscope to identify surgical landmarks of the ICA in the cavernous sinus. Clinical cases of cavernous sinus tumors were surgically treated using an endoscopic transpterygoid approach.

RESULTS

Anatomical study indicated the ICA at the superior part of the cavernous sinus can be identified using three steps: 1) exposure of the optic nerve sheath by drilling the optic canal; 2) identification of the proximal orifice of the optic nerve sheath at the transition of the optic nerve sheath and dura mater of the tuberculum sellae; and 3) identification of the clinoid segment of the ICA at the distal dural ring just below the proximal orifice of the optic nerve sheath. Although the ICA was encased and transposed by tumors in preliminary surgical cases, the clinoid segment of the ICA was safely exposed at the superior part of the cavernous sinus using this method.

CONCLUSIONS

Dural structures around the cavernous sinus are key to identifying the ICA at the superior part of the cavernous sinus. This method is expected to reduce the risk of ICA injury during endoscopic endonasal surgery for cavernous sinus tumors.

Anatomical variations of the sphenoid sinus and its adjacent structures: a review of existing literature

The sphenoid sinus, one of the posterior groups of sinuses, has long been regarded as a 'neglected sinus' due to the anatomical location, poor understanding and poor accessibility, till the advent of endoscopes and modern imaging techniques. Increasing knowledge and greater understanding of this sinus has permitted an evolution in surgical practices and boundaries. Various literatures of the past report a great variety of rates of pneumatization, rates of optic nerve protrusion and dehiscence, as well as internal carotid artery (ICA) protrusion and dehiscence. One similarity noted among these studies is that the rates vary according to the ethnicity of the patients. Recommendations have also been made along the way with regard to modified surgical techniques. This review aims to describe the pneumatization of sphenoid sinus and the topographical relation of the optic nerve and ICA in different populations.

Mapping of cerebral perfusion territories using territorial arterial spin labeling: techniques and clinical application

A knowledge of the exact cerebral perfusion territory which is supplied by any artery is of great importance in the understanding and diagnosis of cerebrovascular disease. The development and optimization of territorial arterial spin labeling (T-ASL) MRI techniques in the past two decades have made it possible to visualize and determine the cerebral perfusion territories in individual patients and, more importantly, to do so without contrast agents or otherwise invasive procedures. This review provides an overview of the development of ASL techniques that aim to visualize the general cerebral perfusion territories or the territory of a specific artery of interest. The first efforts of T-ASL with pulsed, continuous and pseudo-continuous techniques are summarized and subsequent clinical studies using T-ASL are highlighted. In the healthy population, the perfusion territories of the brain-feeding arteries are highly variable. This high variability requires special consideration in specific patient groups, such as patients with cerebrovascular disease, stroke, steno-occlusive disease of the large arteries and arteriovenous malformations. In the past, catheter angiography with selective contrast injection was the only available method to visualize the cerebral perfusion territories in vivo. Several T-ASL methods, sometimes referred to as regional perfusion imaging, are now available that can easily be combined with conventional brain MRI examinations to show the relationship between the cerebral perfusion territories, vascular anatomy and brain infarcts or other pathology. Increased availability of T-ASL techniques on clinical MRI scanners will allow radiologists and other clinicians to gain further knowledge of the relationship between vasculature and patient diagnosis and prognosis. Treatment decisions, such as surgical revascularization, may, in the near future, be guided by information provided by T-ASL MRI in close correlation with structural MRI and quantitative perfusion information.

[Microsurgical anatomy importance of A1-anterior communicating artery complex]

BACKGROUND

The anterior cerebral artery originates from the bifurcation of the internal carotid artery lateral to the optic chiasm, then joins with its contralateral counterpart via the anterior communicating artery. A1-anterior communicating artery complex is the most frequent anatomical variants and is the major site of aneurysms between 30 to 37%.

OBJECTIVE

Know the anatomy microsurgical, variants anatomical and importance of complex precommunicating segment-artery anterior communicating in surgery neurological of the pathology vascular, mainly aneurysms, in Mexican population.

METHODS

The study was performed in 30 brains injected. Microanatomy was studied (length and diameter) of A1-anterior communicating artery complex and its variants.

RESULTS

60 segments A1, the average length of left side was 11.35 mm and 11.84 mm was right. The average diameter of left was 1.67 mm and the right was 1.64 mm. The average number of perforators on the left side was 7.9 and the right side was 7.5. Anterior communicating artery was found in 29 brains of the optic chiasm, its course depended on the length of the A1 segment. The average length of the segment was 2.84 mm, the average diameter was 1.41 mm and the average number of perforators was 3.27. A1-anterior communicating artery complex variants were found in 18 (60%) and the presence of two blister-like aneurysms.

CONCLUSION

It is necessary to understand the A1-anterior communicating artery complex microanatomy of its variants to have a three-dimensional vision during aneurysm surgery.

[Anatomic variations of the internal carotid artery: implications for the neurologic endovascular therapist]

Tortuosity of the cervical segment of the internal carotid artery (ICA) can hinder navigation intravascular devices for treating intracranial aneurysms and even complex ICA access techniques can fail. Variations in the course of the internal carotid artery are known as coiling, kinking or tortuosity of the vessel. Such failures have clinical relevance. During endovascular procedures these anomalies difficult the intravascular surgical procedure. A potential alternative is the reconstruction of these anatomic anomalies of the carotid artery using neuro-interventional methods. We present a practical review of the literature.

Unilateral variation in the position of internal and external carotid arteries

During the routine dissection of the neck region of a 77 years old male cadaver in the Department of Anatomy at Bankura Sammilani Medical College, a unilateral variation in the position and course of internal and external carotid arteries was noticed on the right side of neck. The internal carotid artery was anteromedial to the external carotid artery at the site of bifurcation of the common carotid artery. Knowledge of variation in the course and relation of internal and external carotid arteries is important for surgeons to perform neck surgery and also for the radiologists to interpret carotid system imaging.

[Association of three anatomical variants of the anterior cerebral circulation]

BACKGROUND

As part of a study of the microsurgical anatomy of the pericallosal artery, we describe one brain with three unusual anatomical variants.

METHODS

From the autopsy of a 45 year-old female, we extracted the brain and all the arterial blood vessels were washed off with saline solution to be injected afterwards with red latex. The brain was then immersed in 10% formalin for two months. Finally, we dissected and measured the internal carotid artery segments, using a digital Vernier caliper under a Carl Zeiss OPMI surgical microscope with magnification of 6x up to 40x.

RESULTS

The brain's weight was 1250 grams and three rare anatomical variants were found: 1) right accessory middle cerebral artery (ACMA-d), 2) right bihemispheric anterior cerebral artery (ACABihem-d), 3) median artery of the corpus callosum (AMCC).

CONCLUSION

The association of the anatomical variations described previously is inconstant; furthermore, their appearance in a single case is rare.

Incidence of the occipital artery arising from the internal carotid artery identified by three-dimensional computed tomographic angiography

Variants of the branches of the external carotid artery are common, but it is extremely rare that the occipital artery arises from the internal carotid artery. We investigated the incidence using three-dimensional computed tomographic (CT) angiography. In 265 patients with cancer of the head and neck, we did CT angiography for vascular mapping of the external carotid artery and its branches before reconstruction or superselective intra-arterial chemotherapy. The origin of the occipital artery was detected in 514 of 530 carotid arteries (97%); the incidence of it arising from the internal carotid artery was 0.2%.

[Paraclinoid region: descriptive anatomy and radiological correlations with MR imaging]

OBJECTIVE

The paraclinoid region has a complex anatomy. The purpose of this study was to depict in details its anatomical landmarks and their radiological translations with magnetic resonance imaging (MRI).

MATERIAL AND METHOD

Ten anatomical specimens (20 paraclinoid regions) were prepared, then dissected and further analyzed with MRI in order to describe their important radio-anatomical structures (dural folds, osseous surfaces, arteries and nerves) along with their course and measurements, and the reference points of the carotid distal dural ring. The paraclinoid MR protocol consisted in a T2 high-resolution sequence with thin and contiguous slices acquired in a coronal (diaphragmatic) and sagittal oblique (carotid) plane. Reproducibility in living subjects was evaluated on 15 patients (30 paraclinoid regions). Statistical comparison was made between laboratory and MR measurements obtained on cadavers.

RESULTS

A detailed description of paraclinoid anatomy and structures was provided. Its landmarks were satisfactorily identified with the dedicated MR protocol. Reproducibility in living subjects was obtained. No statistical difference was found between laboratory and MR measurements.

CONCLUSION

This study provides a precise description of paraclinoid anatomical structures and their radiological correlations. This paraclinoid MR protocol allows locating paraclinoid lesions in comparison with the cavernous sinus roof, which is of paramount importance for the management of paraclinoid carotid artery aneurysms.

Neurovascular relationship between abducens nerve and anterior inferior cerebellar artery

We aimed to study the neurovascular relationships between the anterior inferior cerebellar artery (AICA) and the abducens nerve to help determine the pathogenesis of abducens nerve palsy which can be caused by arterial compression. Twenty-two cadaveric brains (44 hemispheres) were investigated after injected of coloured latex in to the arterial system. The anterior inferior cerebellar artery originated as a single branch in 75%, duplicate in 22.7%, and triplicate in 2.3% of the hemispheres. Abducens nerves were located between the AICAs in all hemispheres when the AICA duplicated or triplicated. Additionally, we noted that the AICA or its main branches pierced the abducens nerve in five hemispheres (11.4%). The anatomy of the AICA and its relationship with the abducens nerve is very important for diagnosis and treatment.

[Microsurgical treatment of internal carotid bifurcation aneurysms]

Clinical and imaging findings of a series of 14 internal carotid artery bifurcation aneurysms microsurgically treated are presented. A total of 10 lesions were diagnosed before rupture and 4 patients presented with subarachnoidal hemorrhage and frontobasal intracerebral bleeding. Diagnosis was done using neuroimaging (CT scan, angio-CT-3D, angio-MRI, angiography) but patients with ruptured aneurysms were treated with the sole information provided by the angio-CT-3D. The average fundus size was 8.4mm (3-13.3) and the average neck size was 6.8mm (3-9.6), being the fundus-to-neck ratio 1.32 (0.46-2.05). All lesions were microsurgically treated through a pterional approach with the help of temporary clipping of the afferent vessels in all cases. We used peroperative neuroprotective, neuromonitorization and micro-doppler cerebral flow measurement. Clinical results were excellent with 13 patients GOS grade 5 and one grade 4 three month afterwards of hospital discharge and complete exclusion of the lesion in angiographic controls done solely in patients with ruptured lesions.

Automatic identification of internal carotid artery from 3DRA images

Geometric characteristics and arrangement of the cerebral vessels are assumed to be related to the development of vascular diseases. Identifying anatomical segments and bifurcations of the cerebral vasculature allows the comparison of these characteristics across and within subjects. In this paper, we focus on the automatic identification of internal carotid artery (ICA) from 3D rotational angiographic images. The steps of the proposed method are the following: Arterial vascular tree is first segmented and centerlines are computed. From a set of centerlines, vascular tree topology is constructed and its bifurcations geometrically characterized. Finally, ICA terminal bifurcation is detected, which enables ICA identification. To detect ICA terminal bifurcation, a support vector machine classifier is trained. We processed 82 images to obtain 274 feature vectors of bifurcations around the ICA. 10×5-fold cross-validation showed an average accuracy of 99.6%, with 99.5% specificity and 100% sensitivity. The two most discriminating bifurcation features were: radius ratio between the smaller branch and its parent vessel, and the long-axis component of the smaller branch vector.

Vascular anatomy: the head, neck, and skull base

Knowledge of the anatomy of the vasculature of the head and neck from the thorax to the skull base is critical to the approach to diagnosis and treatment of cerebrovascular disease. Awareness of the anatomic variations that may be encountered, common and uncommon, is necessary to avoid diagnostic pitfalls and to avert therapeutic disasters. Careful anatomic analysis and understanding of collateral pathways and dangerous anastomoses facilitates cross-sectional and angiographic diagnosis and the development of surgical and endovascular treatment strategies.

The variations of the anterior choroidal artery: an intraoperative study

AIM

Increasing use of surgical magnification for operations in the territory of the anterior choroidal artery (AChA) has created a need for detailed knowledge of their anatomical variations. The aim of the present study is to examine the anatomical variations of the AChAin patients operated via pterional approach.

MATERIAL AND METHODS

The origin and branching pattern of AChAs were observed intraoperatively in 130 patients who were operated via a pterional approach at our center.

RESULTS

AChAs arose from the internal carotid artery (ICA) and distal to the posterior communicating artery (PCoA) at a ratio of 70%, from just distal to the original point of the PCoA in 20%, and from just proximal to the ICA bifurcation in 10% of the patients. In 95 cases, AChAs arose from the inferolateral aspect of the ICA in the posterolateral aspect in 27 and from its lateral part in 8 cases. AChAs were found as a single branch at the origins from ICA in 110 patients, as double in 17 cases and as triple in 3 patients.

CONCLUSION

Recognition of anatomical variations and microvascular relationships of AChA will allow neurosurgeons to construct a better and safer microdissection plan, to save time and can prevent postoperative neurological deficits.

Medial wall of the cavernous sinus: microanatomical diaphanoscopic and episcopic investigation

PURPOSE

To elucidate the question whether expansion of pituitary adenomas into the cavernous sinus (CS) has to be regarded as focal penetration rather than invasion, a microanatomical study of the medial wall (MW) of the CS was performed.

METHOD

Fourteen sellar hemiblocks underwent microsurgical dissection from lateral and medial approach. The thickness of the MW of the CS was examined by diaphanoscopy.

FINDINGS

The internal carotid artery (ICA) was adherent to the MW in five cases. In five specimens the lateral wall of the sella turcica consisted of a single layer without perforations. In nine cases this wall had two layers. There was no perforation of both layers in any case. Diaphanoscopy revealed thin MW in the lateral border of the sella (n = 13), below the horizontal segment of the ICA (n = 10), and antero-inferiorly to the carotid syphon (n = 9).

CONCLUSIONS

Expansion into the CS may be facilitated by low anatomical resistance against chronic tumor growth.

A framework for geometric analysis of vascular structures: application to cerebral aneurysms

There is well-documented evidence that vascular geometry has a major impact in blood flow dynamics and consequently in the development of vascular diseases, like atherosclerosis and cerebral aneurysmal disease. The study of vascular geometry and the identification of geometric features associated with a specific pathological condition can therefore shed light into the mechanisms involved in the pathogenesis and progression of the disease. Although the development of medical imaging technologies is providing increasing amounts of data on the three-dimensional morphology of the in vivo vasculature, robust and objective tools for quantitative analysis of vascular geometry are still lacking. In this paper, we present a framework for the geometric analysis of vascular structures, in particular for the quantification of the geometric relationships between the elements of a vascular network based on the definition of centerlines. The framework is founded upon solid computational geometry criteria, which confer robustness of the analysis with respect to the high variability of in vivo vascular geometry. The techniques presented are readily available as part of the VMTK, an open source framework for image segmentation, geometric characterization, mesh generation and computational hemodynamics specifically developed for the analysis of vascular structures. As part of the Aneurisk project, we present the application of the present framework to the characterization of the geometric relationships between cerebral aneurysms and their parent vasculature.

Hypoglossal schwannoma-successful reinnervation and functional recovery of the tongue following tumour removal and nerve grafting

OBJECTIVE

Hypoglossal nerve schwannomas are rare tumours that usually cause ipsilateral hypoglossal palsy. This report describes such lesions in two patients and suggests nerve grafting as part of the treatment regimen.

METHOD

Two patients with intra- and extra-dural hypoglossal schwannomas respectively were treated by direct surgery via a postero-lateral approach to the posterior fossa, hypoglossal canal and carotid sheath. Following tumour removal, sural nerve grafting was used to reconstruct the nerves. Unexpectedly, muscle bulk and motor function returned within 6 months in both patients.

CONCLUSION

Nerve grafting was highly successful in achieving functional recovery following surgery for hypoglossal nerve schwannomas.

Variation of the recurrent artery of Heubner in human cadavers

Study the normal anatomical and variation of the recurrent artery of Heubner (RAH) in fifty Thai cadaveric brains were studied under operating microscope. The anterior communicating artery (ACoA) located at the orbital surface of gyrus rectus about 50% and medial surface of gyrus rectus about 50%. The recurrent artery of Heubner originated from the anterior cerebral artery part 2 (ACA2) 60.4%, junction of ACoA 31.9%, and anterior cerebral artery part 1 (ACA1) 7.7%. Ninety-two percent of the origins of the RAH were identified within 2 mm from the proximal and distal of ACoA. The most common site of its origin from main artery was at its lateral surface 91.0%. The courses of RAH in relation to ACA1 segment were found anteriorly 63.4%, superiorly 29.9% and posteriorly 6.7%, respectively.

Trans-arterial embolisation therapy of dural carotid-cavernous fistulae using low concentration n-butyl-cyanoacrylate

BACKGROUND

Trans-venous embolisation has been accepted as the preferred treatment for dural carotid-cavernous fistulae (DCCF). However, such an approach is not always feasible. In this circumstance, trans-arterial embolisation with low concentration n-butyl-cyanoacrylate glue (NBCA) may be a feasible alternative. We report our results and experience of this method for DCCF.

MATERIALS AND METHODS

Five patients with DCCF were treated by trans-arterial embolisation using low concentration NBCA by wedging the microcatheter into the main feeding artery. All five lesions were associated with venous drainage into the superior ophthalmic vein. The inferior petrosal sinus was patent in one patient and thrombosed in four. Additional venous drainage into the Sylvian vein and the superior petrosal sinus was observed in two patients.

FINDINGS

The definitive NBCA injection was performed via the branches of the middle meningeal artery in three patients and accessory meningeal artery as well as ascending pharyngeal artery in two patients. Four patients showed complete obliteration of the DCCF on the post-embolisation angiogram, and follow-up studies showed clinical cure or improvement and successful obliteration of the DCCF. One patient had a residual DCCF after the procedure, but showed complete obliteration and clinical cure at 5-month follow-up. Glue penetrated into the Sylvian vein in one patient during the procedure without sequelae. Two patients had transient worsening of ocular symptoms after the procedure.

CONCLUSIONS

Trans-arterial embolisation with low concentration NBCA using a wedged microcatheter technique is still a safe and effective treatment for DCCF when the transvenous approach is not feasible. However, care must be taken to prevent inadvertent arterial and venous embolisation.

Cochlear anatomy study used to design surgical instruments for cochlear implants with two bundles of electrodes in ossified cochleas

Cochlear ossification, mainly secondary to meningitis, prevents the complete conventional cochlear implant insertion. Implants with two electrode bundles shorter than the conventional ones were specifically developed for ossified cochleas. However, during surgery there is a high risk of damaging the internal carotid artery (ICA). Therefore, measuring cochleostomy depth in order to insert the two electrode bundles would greatly increase the procedure's safety.

Aims

1) Find the distances between cochleostomies and ICA in cadaver temporal bones. 2) Design an instrument that can be used in cochlear implant surgery to introduce an implant with two bundles of electrodes.

Study Design

Experimental prospective.

Materials and Methods

In 21 temporal bones from cadavers we performed: 1) canal wall down mastoidectomy; 2) cochleostomy in the cochlear basal and middle turns; 3) ICA identification; 4) Length determination between the cochleostomies and the artery.

Results

the average distance ± standard deviation obtained for the upper tunnel was of 8.2 ± 1.1 mm and for the lower tunnel it was of 8.1± 1.3 mm. The shortest distance found was of 6.5 mm for the upper tunnel and 6.0 mm for the lower tunnel.

Conclusion

Despite the values calculated, we concluded that the best value to be considered in creating a surgical instrument are the minimum lengths obtained for each one of the cochlear turns, because this is the safest way to avoid damaging the ICA, that can be fatal.