Anatomical study of petrous and cavernous parts of internal carotid artery

Guidezilla Catheter in Neuroendovascular Interventions: A Case Series Study

BACKGROUND

Neuroendovascular procedures can be challenging due to severe angulation of the cervical and cranial vessels. Typical approaches for overcoming this tortuosity involve using multiple telescoping catheter systems to provide proximal support for therapeutic device delivery. Although this approach can be effective, it does have limitations.

METHODS

We describe the utility of the Guidezilla (Boston Scientific, Natick, Massachusetts, USA) guide extension catheter, a device designed for coronary interventions, in the treatment of 3 patients undergoing neuroendovascular procedures.

RESULTS

In these 3 cases, the decision to use a guide extension catheter varied but was mainly due to severe tortuosity, heavy calcifications, and failure to introduce stents into distal locations.

CONCLUSIONS

Although helpful in overcoming challenging anatomy, the Guidezilla guide extension catheter should be used with caution when used as a bailout device.

Anatomical characteristics and morphometric analyses of the internal carotid artery using retrospective angiographic images

PURPOSE

Anatomical variations of the internal carotid artery (ICA) can cause complications during endovascular treatments. Therefore, the aim of this study was to investigate the features of the ICAs obtained from 2D digital subtraction angiography (2D DSA).

METHODS

The morphometrics and angles of the ICA segments from 2D DSA images from a total of 100 patients (45 males and 55 females) were investigated. The lengths (L1-3), angles (A1-3), and diameters (D1-6) through the ICA measurement points (five segments: C2 [petrous], C3 [lacerum], C4 [cavernous], C5 [clinoid], C6 [ophthalmic]) were systemically recorded by two observers. All measured parameters were compared for both sexes and sides.

RESULTS

The lengths (mm) and angles of the ICA were 7.20 ± 2.22 (L1), 15.71 ± 2.32 (L2), 10.99 ± 1.66 (L3) and 109.31 ± 17.77 (A1), 107.87 ± 20.51 (A2), 80.81 ± 16.33 (A3), respectively. There were no differences in the angulations of the A1-A3 segments between the sexes (p > 0.05). The L2 (C3-C4) was significantly longer in males, but only the left side of females showed a greater length (p < 0.05). The averaged mean diameters of the ICA (D1-6) in both sexes were 4.17 ± 0.55 mm. However, the diameters of the D1-D6 from left and right sides of males except the right D6 were significantly longer than those of females (p < 0.05). Also of significance was that the right diameters of females (D1) and males (D1 and D2) were shorter compared to left sides.

CONCLUSION

This study demonstrates some differences in lengths, diameters, and angles in both sexes and sides of the normal ICA. Neurosurgeons and neurointerventionalists should be aware of such variations when operating, performing interventional procedures, and interpreting 2D DSA.

Clinical analysis of cavernous sinus anatomy, pathologies, diagnostics, surgical management and complications - comprehensive review

For decades, the cavernous sinus (CS) has been the subject of debates and scientific studies aimed at elucidating its anatomical variability, and at choosing the best method for accessing it so that optimal diagnoses and related surgical treatments can be decided. The present review considers a series of issues related to the CS. The anatomy of the CS and its features is explored first, and the most important structures, spaces and morphological variations are considered. This is followed by CS pathology and selected diagnostic methods that have proved useful in therapy, and then the management of these pathologies is discussed. Examples of therapeutic steps that have proved helpful in specific cases are taken from the literature. Finally, the various surgical accesses and complications that can be encountered during invasive interventions in the CS area are discussed. The aim of this study is to summarize up-to-date anatomical and clinical knowledge about the CS, citing the most informative scientific papers and aggregating their results. Morphological variations of the CS are common but have not been well described in the literature.

Impact of histological clot composition on preprocedure imaging and mechanical thrombectomy

INTRODUCTION:

We studied the relationship of acute ischemic stroke (AIS) large-vessel occlusion clot composition with vessel recanalization and preprocedure imaging.

SUBJECTS AND METHODS:

Individual clots from AIS patients who underwent mechanical thrombectomy (MT) between September 2016 and September 2018 were examined. Clot composition was analyzed histologically through a trichrome staining and image segmentation, and the area occupied by red blood cells (RBCs), fibrin, or mixed composition was quantified.

RESULTS:

Forty-three patients (65.4 ± 12.7 years, 39% of females) who underwent 92 retrieval passes (mean 2.14, range 1–6) were included in this study. Fibrin (44%) occupied the greatest area, followed by mixed composition (34%) and RBCs (22%). A stent retriever was deployed in 81% of cases, 20 patients (47%) achieved first-pass efficacy (FPE) (thrombolysis in cerebral infarction [TICI] 2b-3 after first pass), 41 (95%) achieved successful revascularization (TICI 2b-3), and 21 (49%) had good outcome (modified Rankin Scale [mRS] ≤2) at 90 days. Hyperdense artery sign (HAS) on initial computed tomography was correlated with mixed clot composition (P = 0.01) and lack of fibrin content (P = 0.03). In the univariate analysis, FPE was associated with RBC clot area, atrial fibrillation, and occlusion location but not with fibrin clot area, mixed clot area, stroke etiology, thrombectomy technique, distal emboli, or 90-day mRS. In the multivariate analysis, FPE was significantly correlated with low RBC clot area (odd ratio = 0.96, confidence interval [0.92.99], P = 0.034) but not with atrial fibrillation or location.

CONCLUSION:

Our results suggest that HAS is correlated with mixed clot composition and lower fibrin content and that lower RBC clot composition is associated with FPE in patients undergoing MT.

Automated landmarking of bends in vascular structures: a comparative study with application to the internal carotid artery

Automated tools for landmarking the internal carotid artery (ICA) bends have the potential for efficient and objective medical image-based morphometric analysis. The two existing algorithms rely on numerical approximations of curvature and torsion of the centerline. However, input parameters, original source code, comparability, and robustness of the algorithms remain unknown. To address the former two, we have re-implemented the algorithms, followed by sensitivity analyses. Of the input parameters, the centerline smoothing had the least impact resulting in 6-7 bends, which is anatomically realistic. In contrast, centerline resolution showed to completely over- and underestimated the number of bends varying from 3 to 33. Applying the algorithms to the same cohort revealed a variability that makes comparison of results between previous studies questionable. Assessment of robustness revealed how one algorithm is vulnerable to model smoothness and noise, but conceptually independent of application. In contrast, the other algorithm is robust and consistent, but with limited general applicability. In conclusion, both algorithms are equally valid albeit they produce vastly different results. We have provided a well-documented open-source implementation of the algorithms. Finally, we have successfully performed this study on the ICA, but application to other vascular regions should be performed with caution.

Investigation of Hemodynamic Receptors of the Internal Carotid Artery Segments

Objectives

Internal carotid artery (ICA), the main artery of the brain, passes through the cavernous sinus (CS) which forms one of these venous pools. During this transition, while there is arterial blood in the lumen of ICA, its outer surface is in contact with venous blood from the brain. Herein, we aimed to detect the receptor differences of ICA in this highly specialized anatomical region of the skull base.

Methods

We performed the study on 10 human cadavers and searched CGRPR, TRP12, ASIC3 and ACTHR receptors via immunostaining using laser scanning confocal microscopy.

Results

We determined TRP12 receptor positive in the tunica media and tunica adventitia layers of the cavernous segment of ICA. We did not detect similar positivity in the cervical part of the ICA. In the receptor scan we made in terms of CGRPR, while we detected positivity in the tunica media layer of the cavernous segment, we found positivity in the tunica intima layer of the cervicalis segment of the ICA. We did not detect any positivity for ASIC3 and ACTHR receptors in both parts of the ICA.

Conclusions

As a result, we observed various differences in receptors between ICA segments. While the outer surface of the ICA in the cervical region did not show any receptor positivity, we detected TRP12 receptor positivity along the tissue contour of vessel in the CS. We assume that it may provide a new perspective on pathologies of the CS/ICA and preservation of brain hemodynamics for clinicians.

Hemodynamic modeling of the circle of Willis reveals unanticipated functions during cardiovascular stress

The circle of Willis (CW) allows blood to be redistributed throughout the brain during local ischemia; however, it is unlikely that the anatomic persistence of the CW across mammalian species is driven by natural selection of individuals with resistance to cerebrovascular disease typically occurring in elderly humans. To determine the effects of communicating arteries (CoAs) in the CW on cerebral pulse wave propagation and blood flow velocity, we simulated young, active adult humans undergoing different states of cardiovascular stress (i.e., fear and aerobic exercise) using discrete transmission line segments with stress-adjusted cardiac output, peripheral resistance, and arterial compliance. Phase delays between vertebrobasilar and carotid pulses allowed bidirectional shunting through CoAs: both posteroanterior shunting before the peak of the pulse waveform and anteroposterior shunting after internal carotid pressure exceeded posterior cerebral pressure. Relative to an absent CW without intact CoAs, the complete CW blunted anterior pulse waveforms, although limited to 3% and 6% reductions in peak pressure and pulse pressure, respectively. Systolic rate of change in pressure (i.e., ∂P/∂t) was reduced 15%-24% in the anterior vasculature and increased 23%-41% in the posterior vasculature. Bidirectional shunting through posterior CoAs was amplified during cardiovascular stress and increased peak velocity by 25%, diastolic-to-systolic velocity range by 44%, and blood velocity acceleration by 134% in the vertebrobasilar arteries. This effect may facilitate stress-related increases in blood flow to the cerebellum (improving motor coordination) and reticular-activating system (enhancing attention and focus) via a nitric oxide-dependent mechanism, thereby improving survival in fight-or-flight situations.NEW & NOTEWORTHY Hemodynamic modeling reveals potential evolutionary benefits of the intact circle of Willis (CW) during fear and aerobic exercise. The CW equalizes pulse waveforms due to bidirectional shunting of blood flow through communicating arteries, which boosts vertebrobasilar blood flow velocity and acceleration. These phenomena may enhance perfusion of the brainstem and cerebellum via nitric oxide-mediated vasodilation, improving performance of the reticular-activating system and motor coordination in survival situations.

Morphometry of the Entire Internal Carotid Artery on CT Angiography

Background and Objectives: Knowledge of the internal carotid artery’s (ICA) morphometric features is influential in outlining surgical and minimally invasive procedures in the neurovascular field. Many studies have shown divisive numbers regarding the ICA’s caliber, with the measuring point of the artery sometimes differing. This study presents ICA dimensions based on computed tomography angiography in each of its seven segments as per Bouthillier’s classification, correlating vascular dimensions with anthropometric parameters. Materials and Methods: A thorough CT angiography analysis was performed on 70 patients with internal carotid vessels unaffected by atherosclerotic disease. The extracranial part of the ICA was measured in four locations—carotid bulb, post-bulbar dilation, at its cervical midpoint, and below its entrance into the carotid foramen. Single landmarks were used for measurements in the intracranial segments. ICA length was assessed in the neck region and also in the cranial cavity. Craniometric measurements were performed on sagittal and coronal CT reconstructions. Patient height was taken into consideration. Results: The largest ICA portion is near its origin in the carotid sinus area (7.59 ± 1.00 mm), with a steep decline in caliber following its extracranial course. Distal ICA presented values somewhat similar to its proximal intracranial segment diameters (4.67 ± 0.47 mm). Dimensions of the ICA in the intracranial segments start from a value of 4.53 ± 0.47 mm and decrease by approximately 40% when reaching the origin of the middle cerebral artery (2.71 ± 0.37 mm), showing a marked decrease in caliber after the emergence of the most critical collateral artery, the ophthalmic branch. The length of the ICA varies between genders, with the male ICA being about 10 mm longer in total length than female ICA; this difference is also correlated with patient height and skull dimensions. Conclusions: Both intra- and extracranial ICA have variable dimensions and length related to gender and anthropometric parameters, with no significant differences obtained concerning side or age.

The parietal foramen anatomy: studies using dry skulls, cadaver and in vivo MRI

OBJECTIVE

The aim of this study was to describe the anatomical features encountered in the parietal foramen in a series of 178 human bones and 123 head MRI examinations. A cadaveric specimen was also dissected to demonstrate the trajectory of a superficial scalp vein through the parietal foramen as far as the dura mater. A literature review was performed regarding prevalence of parietal foramen in different populations.

METHODS

Totally, 178 paired adult bones were used to investigate the presence, shape and number of the parietal foramina. In addition, 123 brain MRI examinations were also studied.

RESULTS

The parietal foramina were encountered in 75/89 (84.3%) skulls [32/38 (84.2%) in women vs. 43/51 (84.3%) in men, p > 0.05]. The parietal foramen was present bilaterally in 44.73% of females and 54.9% of males. Regarding unilaterality of the parietal foramen, a right or left laterality was observed in female 21% right versus 18% left; and 16% versus 14% (left) in males (p > 0.05). The accessory parietal foramen was present in the right parietal in 2.6% and in 7.9% on the left side of the females, while 5.9% and 3.9% of the males on the right or left sides, respectively. The parietal foramina located in the proximity of the sagittal suture (male 7.1 ± 2.5 mm vs. female, 7.4 ± 2.7 mm). There was a positive correlation between the right and left parietal foramina regarding the distance from the median line. The distance from a foramen to the contralateral one was 16 ± 4 mm in men and 18 ± 5 mm in women, respectively (p > 0.05).

CONCLUSION

No major differences were encountered between sexes regarding the anatomical features of parietal foramen.

Rare Clinical Onset of Nontraumatic Intracavernous Aneurysm of the Internal Carotid Artery: A Diagnostic and Therapeutic Challenge

While the so-called pseudoaneurysms can result from arterial injury during trans-sphenoidal surgery or after a trauma, spontaneous aneurysms of cavernous–internal carotid artery (CICA) are rare. Symptoms vary and the differential diagnosis with other, more frequent, sellar lesions is difficult. We describe three cases of misdiagnosed CICA spontaneous aneurysm. In two cases the onset was with neuro-ophthalmological manifestations, classifiable as “cavernous sinus syndrome.” The emergency computed tomography scan did not show CICA aneurysm and the diagnosis was made by surgical exploration. The third patient came to our attention with a sudden severe unilateral epistaxis; endonasal surgery revealed also in this case a CICA aneurysm, eroding the wall and protruding into the sphenoidal sinus. When the onset was with a cavernous sinus syndrome, misdiagnosis exposed two patients to potential serious risk of bleeding, while the patient with epistaxis was treated with embolization, using coils and two balloons. Intracavernous nontraumatic aneurysms are both a diagnostic and therapeutic challenge, because of their heterogeneous onset and risk of rupture, potentially lethal. Intracavernous aneurysms can be managed with radiological follow-up, if asymptomatic or clinically stable, or can be surgically treated with endovascular or microsurgical techniques.

Does vascular stiffness predict white matter hyperintensity burden in ischemic heart disease with preserved ejection fraction?

The survival rate of patients with ischemic heart disease (IHD) is increasing. However, survivors experience increased risk for neurological complications. The mechanisms for this increased risk are unknown. We tested the hypothesis that patients with IHD have greater carotid and cerebrovascular stiffness, and these indexes predict white matter small vessel disease. Fifty participants (age, 40-78 yr), 30 with IHD with preserved ejection fraction and 20 healthy age-matched controls, were studied using ultrasound imaging of the common carotid artery (CCA) and middle cerebral artery (MCA), as well as magnetic resonance imaging (T1, T2-FLAIR), to measure white matter lesion volume (WMLv). Carotid β-stiffness provided the primary measure of peripheral vascular stiffness. Carotid-cerebral pulse wave transit time (ccPWTT) provided a marker of cerebrovascular stiffness. Pulsatility index (PI) and resistive index (RI) of the MCA were calculated as measures of downstream cerebrovascular resistance. When compared with controls, patients with IHD exhibited greater β-stiffness [8.5 ± 3.3 vs. 6.8 ± 2.2 arbitrary units (AU); P = 0.04], MCA PI (1.1 ± 0.20 vs. 0.98 ± 0.18 AU; P = 0.02), and MCA RI (0.66 ± 0.06 vs. 0.62 ± 0.07 AU; P = 0.04). There was no difference in WMLv between IHD and control groups (0.95 ± 1.2 vs. 0.86 ± 1.4 mL; P = 0.81). In pooled patient data, WMLv correlated with both β-stiffness (R = 0.34, P = 0.02) and cerebrovascular ccPWTT (R = -0.43, P = 0.02); however, β-stiffness and ccPWTT were not associated (P = 0.13). In multivariate analysis, WMLv remained independently associated with ccPWTT (P = 0.02) and carotid β-stiffness (P = 0.04). Patients with IHD expressed greater β-stiffness and cerebral microvascular resistance. However, IHD did not increase risk of WMLv or cerebrovascular stiffness. Nonetheless, pooled data indicate that both carotid and cerebrovascular stiffness are independently associated with WMLv.NEW & NOTEWORTHY This study found that patients with ischemic heart disease (IHD) with preserved ejection fraction and normal blood pressures exhibit greater carotid β-stiffness, as well as middle cerebral artery pulsatility and resistive indexes, than controls. White matter lesion volume (WMLv) was not different between vascular pathology groups. Cerebrovascular pulse wave transit time (ccPWTT) and carotid β-stiffness independently associate with WMLv in pooled participant data, suggesting that regardless of heart disease history, ccPWTT and β-stiffness are associated with structural white matter damage.

Analysis of the Anatomical Factors Affecting Ability to Navigate Penumbra Catheter through Internal Carotid Siphon

Objective

The efficacy and safety of aspiration thrombectomy using Penumbra catheter with acute large vessel occlusion in the anterior circulation have been reported in previous studies. In some cases, the carotid siphon (CS) is elongated, and with this anatomy, especially where there is bifurcation of the ophthalmic artery (OA), navigation of Penumbra catheters into distal internal carotid artery (ICA) is interrupted, which is known as the 'ledge effect'. We investigate the anatomical characteristics of CS that cause interruption of navigation of the Penumbra catheter.

Methods

Between January 2015 and March 2018, mechanical thrombectomy using Penumbra 60 was performed on 51 patients with middle cerebral artery (MCA) or intracranial ICA occlusion. Patients were divided into two groups: The 'ledge-effect' group those in whom the Penumbra catheter was unable to be navigated into the distal ICA through the CS, and 'no ledge-effect' group those in whom this was possible. The anatomical characteristics of CS, the diameter of ICA, diameter of OA, OA/ICA ratio and radius of the CS were evaluated using angiographical imaging.

Results

The 'ledge-effect' group numbered eight cases (17%). Only the value of the CS radius was significantly smaller in the ledge-effect group (p = 0.0019), other parameters were not significantly different between the groups. The cutoff radius value was 3.62 mm.

Conclusion

The most notable anatomical factor affecting possibility of navigation of the Penumbra catheter through the CS was the CS radius. This could be useful information when devices used in mechanical thrombectomy are selected.

Cerebral blood flow rates in recent great apes are greater than in Australopithecus species that had equal or larger brains

Brain metabolic rate (MR) is linked mainly to the cost of synaptic activity, so may be a better correlate of cognitive ability than brain size alone. Among primates, the sizes of arterial foramina in recent and fossil skulls can be used to evaluate brain blood flow rate, which is proportional to brain MR. We use this approach to calculate flow rate in the internal carotid arteries (Q˙ICA), which supply most of the primate cerebrum. Q˙ICA is up to two times higher in recent gorillas, chimpanzees and orangutans compared with 3-million-year-old australopithecine human relatives, which had equal or larger brains. The scaling relationships between Q˙ICA and brain volume (V_br) show exponents of 1.03 across 44 species of living haplorhine primates and 1.41 across 12 species of fossil hominins. Thus, the evolutionary trajectory for brain perfusion is much steeper among ancestral hominins than would be predicted from living primates. Between 4.4-million-year-old Ardipithecus and Homo sapiens, V_br increased 4.7-fold, but Q˙ICA increased 9.3-fold, indicating an approximate doubling of metabolic intensity of brain tissue. By contrast, Q˙ICA is proportional to V_br among haplorhine primates, suggesting a constant volume-specific brain MR.

Bone foramen dimensions and blood flow calculation: best practices

Some blood vessels enter bones through foramina, leaving the size of the foramen as a gauge for estimating the rate of blood flow and hence the metabolic rate of the supplied tissues. Foramen dimensions have been measured using varied methods in previous foramen studies, to relate regional blood flows with associated physiological processes. With the increasing interests in this 'foramen technique', standard methods with minimized measurement errors are therefore required. This study provides details of microphotographic and micro-computerized tomographic methods, and introduces a new alternative method, which uses impression material to measure foramen dimensions. The three methods are compared and the results indicate that all of them are capable of obtaining precise and accurate foramen dimension values, although they all have limitations. A microphotograph of the external opening is suggested to be the standard method because of its ease of use, but the alternative methods provide more detailed information on foramen shape. If the foramen is mainly occupied by one artery, blood flow rates can be calculated from foramen size and artery wall-lumen ratio, which is evaluated from the literature survey in this study. If veins or nerves also penetrate the foramen, a relative index of blood flow rate is nevertheless possible for comparative purposes.

Quantitative analysis of arterial supply to the developing brain in tetrapod vertebrates

Understanding the metabolic cost of building developing tetrapod brains is critically important to explaining the more than 10-fold differences in encephalization of adult tetrapods that have emerged during evolution. The exact metabolic costs of developing the variety of tetrapod brains are impossible to determine, but one can compare cerebral artery caliber (internal radius raised to the fourth power-r⁴ ) across developing tetrapod vertebrate groups as a proxy of cerebral arterial flow, the delivery of nutrients during embryogenesis and early postnatal development, and hence the metabolic costs of brain development. In this study, r⁴ of aortic outflow and cerebral inflow arteries, as well as aortic wall thickness as a proxy of arterial pressure, were measured and compared between developing representatives of all four tetrapod classes (mammals, birds, reptiles, and amphibians). We found a clear endotherm/ectotherm dichotomy in aortic outflow and cerebral inflow between developing mammals and birds on the one hand, and developing reptiles and amphibians on the other. We did not find strong evidence for functionally significant differences in cerebral arterial caliber between groups at the order level (i.e., within birds, reptiles or amphibians). In particular, we did not find evidence in favor of increased blood supply to the brain for more behaviorally complex and encephalized avian species.

Technical and anatomical factors affecting intra-arterial chemotherapy fluoroscopy time and radiation dose for intraocular retinoblastoma

BACKGROUND

Intra-arterial chemotherapy has an increasingly prominent role in the management of retinoblastoma. One concern regarding this technique is procedural radiation exposure.

OBJECTIVES

To examine the effects of our institution's procedural technique on fluoroscopy parameters for patients undergoing intra-arterial chemotherapy infusions for intraocular retinoblastoma. Secondary goals included describing the effect of anatomical variations of the carotid siphon and ophthalmic artery on radiation dose.

METHODS

A retrospective review of pediatric patients with retinoblastoma referred to interventional neuroradiology for chemosurgery was performed. Techniques were classified as: A (1.2 Fr or 1.5 Fr microcatheter with continuous verapamil flush, advanced without guide through a 2 Fr sheath) or B (1.5 Fr or 1.7 Fr microcatheter advanced within a 4 Fr base catheter, through a 4 Fr sheath). Statistical analysis was performed to determine if there was a significant difference in fluoroscopy parameters based on technique or due to anatomical variation.

RESULTS

26 patients were treated with 94 intra-arterial chemotherapy infusions. 34 procedures were performed using technique A and 60 using technique B. Mean fluoroscopy time (4.75 min), fluoroscopy dose (23.3 mGy), and dose-area product (DAP; 85.2 μGy.m²) for technique A were significantly lower (p value <0.05) than for technique B, 14.0 min., 191 mGy, and 586 μGy.cm², respectively.

CONCLUSIONS

Microcatheter-only technique with continuous verapamil infusion resulted in decreased fluoroscopy times, DAP, and radiation doses at our institution for the treatment of intraocular retinoblastoma. Furthermore, our fluoroscopy times using this technique are the lowest reported in the current literature. Additionally, our anatomical analysis has demonstrated a positive correlation between increasing vessel tortuosity and fluoroscopy times.

Anatomic Characteristics of Intrapetrous Carotid Artery: A 3-Dimensional Segmentation Study on Head Computed Tomography Scan

BACKGROUND

The intrapetrous carotid artery (IPCA) is one of the most unexplored anatomic regions, and its 3-dimensional reconstruction in living subjects is still missing. This study aims to describe the IPCA on 3D models extracted from head computed tomography (CT) scans.

METHODS

The intrapetrous carotid artery was manually segmented on head CT scans of 100 healthy patients free from vascular and neurologic pathologies (50 men and 50 women; age range, 18-91 years). Angles of the posterior and anterior genu, diameter and length of the horizontal portion, and volume of the entire canal were calculated through 3D analysis software. Statistically significant differences according to sex and side were assessed through 2-way analysis of variance (P < 0.05). Correlation of each measurement with age was calculated as well.

RESULTS

On average, the angles of the posterior and anterior genu were 120.1° ± 10.4° and 118.0° ± 10.0° in men and 119.5° ± 9.2° and 117.6° ± 10.3° in women, respectively, without statistically significant differences according to sex or side (P > 0.05). The average length and diameter of the horizontal part were, respectively, 25.5 ± 2.9 and 5.8 ± 0.8 mm in men and 24.0 ± 2.3 and 5.3 ± 0.8 mm in women. The volume of the IPCA was 0.941 ± 0.215 cm³ in men and 0.752 ± 0.159 cm³ in women. The length and diameter of the horizontal portion and the volume of the IPCA showed statistically significant differences according to sex (P < 0.05). No correlation with age was found.

CONCLUSIONS

This study provides data concerning not only linear and angular measurements, but also volumes of the IPCA, which are useful in planning surgical interventions of the cranial base.

Review of the main surgical and angiographic-oriented classifications of the course of the internal carotid artery through a novel interactive 3D model

The course of the internal carotid artery (ICA) and its segment classifications were reviewed by means of a new and freely available 3D interactive model of the artery and the skull base, based on human neuroimages, that can be freely downloaded at the Public Repository of the University of Barcelona (http://diposit.ub.edu/dspace/handle/2445/112442) and runs under Acrobat Reader in Mac and Windows computers and Windows 10 tablets. The 3D-PDF allows zoom, rotation, selective visualization of structures, and a predefined sequence view. Illustrative images of the different classifications were obtained. Fischer (Zentralbl Neurochir 3:300-313, 1938) described five segments in the opposite direction to the blood flow. Gibo-Rothon (J Neurosurg 55:560-574, 1981) follow the blood flow, incorporated the cervical and petrous portions, and divided the subarachnoid course-supraclinoid-in ophthalmic, communicating, and choroidal segments, enhancing transcranial microscopic approaches. Bouthillier (Neurosurgery 38:425-433, 1996) divided the petrous portion describing the lacerum segment (exposed in transfacial procedures and exploration of Meckel's cave) and added the clinoid segment between the proximal and distal dural rings, of interest in cavernous sinus surgery. The Kassam's group (2014), with an endoscopic endonasal perspective, introduces the "paraclival segment," including the "lacerum segment" and part of the intracavernous ICA, and details surgical landmarks to minimize the risk of injury. Other classifications are also analyzed. This review through an interactive 3D tool provides virtual views of the ICA and becomes an innovative perspective to the segment classifications and neuroanatomy of the ICA and surrounding structures.