Plasticity of the bony carotid canal and its clinical use for assessing negative remodeling of the internal carotid artery

Background and objective It has long been believed that the bony carotid canal has no plasticity and that a small canal represents a hypoplastic internal carotid artery. We aimed to show whether the carotid canal can narrow according to morphological changes in the internal carotid artery. Materials and methods The carotid canal diameter was longitudinally measured in seven individuals who underwent carotid artery ligation. As moyamoya disease is known to be associated with negative remodeling of the internal carotid artery, the carotid canal diameter was measured in 106 patients with moyamoya disease, and an association with the outer diameter of the internal carotid artery or a correlation with the disease stage was investigated. The carotid canal was measured by computed tomography (106 patients), and the outer diameter of the artery was measured by high-resolution magnetic resonance imaging (63 patients). The carotid canal area was calculated by the product of the maximum axial diameter and its perpendicular diameter. Results All seven patients who underwent carotid artery ligation showed narrowing of the carotid canal, and the carotid canal area decreased by 12.2%–28.9% during a mean follow-up period of 4.2 years. In patients with moyamoya disease, the carotid canal area showed a linear correlation with the outer area of the internal carotid artery (r = 0.657, p < 0.001), and a negative correlation with the disease stage (ρ = −0.283, p < 0.001). Conclusion The bony carotid canal has plasticity, and its area reflects the outer area of the internal carotid artery, therefore, it can be used to assess the remodeling of the carotid artery. A narrow carotid canal may not necessarily indicate hypoplastic internal carotid artery.

Osteological studies of skull base neurovascular area in reference to infratemporal approach to skull basec

Surgical approaches to the lateral skull base often lead to tearing of vessels and piecemeal removal of the tumour. This study is aimed to delineate exact relationship of the various foramina at the lateral skull base. The coronal dimensions of the jugular foramina are larger as compared to sagittal with right sided dominance also noticed in the case of carotid canal. The width of “Keel” separating the carotid and jugular foramina normally varies from 0.4 to1.4 centimetres and may not always suggest the erosion of the foramen of skull base scans, unless the erosion is associated with irregularity or demineralization the thickness of this keel really depends upon relative size of the vessels and location of foramina. Area between stylomastoid foramen, carotid canal and jugular foramen is roughly wedge shaped. The angle subtended by carotid and jugular at the stylomastoid foramen is about 36.84whereas the location of stylomastoid foramen and internal carotid axis pose an angle of 83:16. The angle subtended by stylomastoid and jugular at carotid on an average 59:31. The space between these structures is measured to be 0.642centimetres which can be verified on tomograms. By using these measurements, the precise location of the upper end of the vessels could be predicted, whereas the superior stump could be clamped with minimal exposure of the skull base and identification and location of the last four cranial nerves is found out. This could avoid injuries and subsequent morbidity while carrying out surgery in this region.

Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison1

For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell’s review of tyrannosaurids in which he established Daspletosaurus torosus — a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurus torosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes.

Simpson Grade I Resection of Type II Clinoidal Meningiomal Through Cranio-orbital Zygomatic Approach: 2-Dimensional Operative Video

Clinoidal meningiomas have been considered as a separate entity with distinguishing clinical, radiological, and surgical considerations.1–2 Surgical mortality and morbidity associated with anterior clinoidal meningiomas has remained high in the past, with radical resection considered unattainable.3 However, the extent of surgical removal is clearly the most determining factor in tumor recurrence and progression. Clinoidal meningiomas have been classified into 3 types according to their origin from the dura surface of the anterior clinoid and subsequent arachnoidal rearrangement around the parasellar neurovascular structures.1 In type II, there is an arachnoidal plane that allows the tumor dissection from the encased carotid artery and its branches and the optic nerve. In this type, the involvement of the cavernous sinus is limited to the external wall, which can also be removed. Hence, these tumors are amenable to Simpson grade I resection (tumor, dura, and bone). Approaching through the multidirectional axis provided by the cranio-orbital zygomatic approach allows safe exposure of the tumor and vascular control.4-5 Proximal carotid control is obtained in the petrous carotid canal, the invaded anterior clinoid is removed by and large extradurally, and the Sylvian fissure is split wide open to establish dissecting planes with the middle cerebral artery branches. The optic canal is opened, and tumor extension is removed.6 The invaded outer wall of the cavernous sinus and superior orbital fissure is removed. We demonstrate this technique in a 48-yr-old patient who consented for surgery and publication of images. All images at 2:27, center and right images at 2:46, and all images at 2:58, reused with permission from LWW, from Al-Mefty, Operative Atlas of Meningiomas. Left image at 2:46 reprinted from Surg Neurol, Vol 60/issue 6, Arnautović KI, Al-Mefty O, Angtuaco E, A combined microsurgical skull-base and endovascular approach to giant and large paraclinoid aneurysms, pp. 504–520, Copyright 1998, with permission from Elsevier. Image at 8:21 reprinted from Al-Mefty,1 Clinoidal meningiomas, by permission from JNSPG.

Interposition Grafting of the Facial Nerve After Resection of a Large Facial Nerve Schwannoma: 2-Dimensional Operative Video

Facial nerve schwannomas can develop at any portion of the facial nerve.1 When arising from the mastoid portion of the facial nerve, the tumor will progressively erode the mastoid, giving the schwannoma an aggressive radiological appearance.1,2 The facial nerve is frequently already paralyzed, or no fascicles can be saved during resection. In these cases, end-to-end interposition grafting is the best option for facial reanimation.1,3-5 The healthy proximal and distal facial nerves are prepared prior to grafting. The great auricular nerve is readily available near the surgical site and represents an excellent graft donor with minimal associated morbidity.4,6 We demonstrate this technique through a case of a 48-yr-old male who presented with a complete right-sided facial nerve palsy due to a large facial schwannoma that invaded the mastoid and extended to the hypoglossal canal, causing hypoglossal nerve paralysis, and petrous carotid canal. His 4-yr follow-up showed no recurrent tumor with restored facial nerve function palsy to a House-Brackman grade III, and full recovery of his hypoglossal nerve function. The patient consented to the surgery and the publication of his image.

Carotid Sympathetic Plexus Schwannoma Presenting as Middle Ear and External Auditory Canal Mass

Schwannomas in the middle ear and external auditory canal are exceedingly rare. The facial nerve, chorda tympani nerve, and Jacobson’s nerve have rarely been reported as the origins of primary schwannomas in the middle ear cavity. We experienced a case of carotid sympathetic plexus (CSP) schwannoma that arose from the carotid canal and extended into the middle ear and external auditory canal. The tumor presented bone erosion of the carotid canal, and it adhered tightly to the internal carotid artery. This report represents the first documented case of a CSP schwannoma, which involved the middle ear and external auditory canal.

Transoral Endoscopic Localization of the Parapharyngeal Internal Carotid Artery

Objectives To define transoral endoscopic surgical landmarks for the parapharyngeal segment of the internal carotid artery (ppICA) using cadaveric dissection. Materials and Methods Ten fresh cadaveric heads were dissected to demonstrate the parapharyngeal space anatomy and course of the ppICA as seen in a transoral approach. Anatomical measurements of the distance between the ppICA and bony landmarks were recorded and analyzed. Results The stylohyoid ligament, styloglossus, and stylopharyngeus could be considered to be the safe anterior boundary of the ppICA in the transoral approach; among them, the styloid ligament was the most rigid tissue. Dissection between the stylopharyngeus muscle and superior pharyngeal constrictor muscle provides direct access to the ppICA. At the level of the skull base, the distance from the root of the styloid process to the lateral margin of the external aperture of the carotid canal on the left side and on the right side was 8.57 ± 1.97 and 8.80 ± 1.21 mm, respectively. At the level of the maxillary tuberosity, the distance from the ppICA to the maxillary tuberosity on the left side and on the right side was 31.48 ± 2.24 and 31.01 ± 2.88 mm, respectively. Conclusion The endoscopic-assisted transoral approach can facilitate exposure of the ppICA. The root of the styloid process, styloid ligament, and maxillary tuberosity are critical landmarks in the identification of the ppICA in the transoral approach.