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. 2022 Sep 26;241(6):1303–1309. doi: 10.1111/joa.13765

Anatomical study of the carotid‐trigeminal interface: The missing link in the trigeminovascular system?

Louis‐Marie Terrier 1,2,✉, Anne‐Marie Bergemer 3, Christophe Destrieux 2,4, Igor Lima Maldonado 2,4
PMCID: PMC9644948  PMID: 36156796

Abstract

The trigeminal system is considered a prominent actor in brain nociceptive innervation. The trigeminovascular system is mainly composed of pseudounipolar neurons located within the trigeminal ganglion, whose dendrites originate in cerebral blood vessels. Anatomical studies demonstrating anatomical continuity between perivascular fibers and the trigeminal system are lacking. This issue is addressed in this study. Eleven cadaveric heads obtained from a body donation program were fixed in formalin. We performed a microanatomical study of the cavernous carotid‐trigeminal interface and a histological examination of the tissue bridges crossing the virtual space between the medial aspect of the trigeminal ganglion and ophthalmic nerve and the lateral aspect of the cavernous segment of the internal carotid artery. Very strong adhesion was observed between the horizontal segment of the artery and the ophthalmic nerve in all specimens. The virtual space in this interface was crossed by a web of delicate filaments. Histological examination demonstrated the presence of nerve fibers in all samples. In this study, the carotid‐trigeminal interface has been described in greater detail than ever before and could provide insight into disorders related to the trigeminovascular system. As the present results do not allow the exact nature of the axons to be affirmed, further investigation is necessary.

Keywords: internal carotid artery, sympathetic nervous system, trigeminal nerve, trigeminal system, trigeminovascular system

Very strong adhesion was observed between the horizontal segment of the carotid artery and the ophthalmic nerve in all specimens. The virtual space in this interface was crossed by a web of delicate filaments. Histological examination demonstrated the presence of nerve fibers in all samples.

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1. INTRODUCTION

The trigeminal system is recognized as being responsible for facial and dural sensitivity. More recently, evidence has indicated it to be a prominent actor in cerebrovascular nociceptive innervation, suggesting that it also shares a role in different types of headache and orofacial pain (Edvinsson et al., 2020; Fontaine et al., 2018; May & Goadsby, 1999a; Mayberg et al., 1984; Moskowitz, 1984; Noseda & Burstein, 2013; Olesen et al., 2009; Penfield & McNaughton, 1940; Pietrobon & Moskowitz, 2013; Pietrobon & Moskowitz, 2014; Ray & Wolff, 1940; Terrier et al., 2021; Zhang et al., 2011). The trigeminovascular system, which is responsible for cerebrovascular innervation, originates within the cerebral vascular walls (Arbab et al., 1986; Arbab et al., 1988; Edvinsson, 2011; Edvinsson et al., 1989) and runs in the ophthalmic nerve (V1), that is, the first branch of the trigeminal nerve (Arbab et al., 1986; Arbab et al., 1988; Edvinsson et al., 1981; Edvinsson et al., 1989; Feindel et al., 1960; Liu‐Chen et al., 1986; Liu‐Chen, Han, & Moskowitz, 1983; Liu‐Chen, Mayberg, & Moskowitz, 1983; Mayberg et al., 1984). The trigeminal ganglion contains pseudo‐unipolar neurons. Their axons give two processes: one reaches peripheral targets, including cerebral blood vessels, and the second projects to brainstem trigeminal nuclei. Since it is located at the interface between the nervous and vascular systems, the trigeminovascular system is strategically positioned to detect and convey sensory inputs from brain vessels to the sensory circuits (May & Goadsby, 1999b). The cavernous segment (C4) of the internal carotid artery (ICA) is a strong candidate for being the point where fibers of the trigeminocarotid system reach the trigeminal nerve. In this area, ICA medially crosses the trigeminal ganglion, and the C4 segment takes an anteroposterior orientation and follows these neural structures for several millimeters (Rai et al., 2013).

To our knowledge, there has been no anatomical demonstration of such an interaction. In a previous study, we have detailed the delicate organization of its dural lodges, inner structures, and their anatomical relationships (Destrieux et al., 1998). As part of the dissection process, tissue bridges around the nerves and vessels were described, but their nature was not precisely determined.

In the present study, we performed a microanatomical analysis of the cavernous carotid‐trigeminal interface. Additionally, we histologically examined tissue bridges crossing the virtual space between the medial aspect of the trigeminal ganglion and V1, and the lateral aspect of the cavernous segment (C4) of the ICA.

2. METHODS

2.1. Specimen preparation

We studied 11 adult heads obtained from our institution's body donation program (Association des dons du corps) with ethical permissions of University of Tours (France). Before death, participants—six men and five women, with a mean age of 75.9 ± 13.7 years (mean ± SD, min.: 55, max.: 93)—gave written consent for the use of their entire body for educational or research purposes. The authorization documents, in the form of handwritten testaments, are stored in the files of the Body Donation Center.

Within 24 h of death, specimens were fixed by common carotid artery injection of 4% formalin solution (formaldehyde 4% w/v buffered to pH 6.9, RS, Carlo Erba Reagents, Cornaredo, Italy), followed by immersion in the same fluid. Additionally, for better visibility of the microanatomy (i.e., cavernous branches of the ICA), we injected two of the 11 heads with dyed 671A neoprene latex (DuPont de Nemours); red for the ICAs and vertebral arteries, and blue for the jugular veins (encre acrylique Colorex, Pébéo). This injection was performed manually with a volume of 150 ml for the ICA, of 150 ml for the vertebral arteries at the craniovertebral transition, and of 200 ml for the internal jugular veins. The procedure is performed with the aid of an 200 ml syringe and a small urinary catheter in 10 min. The injection was performed after decapitation at the C4–C5 level of the fifth cervical vertebra, without pressure monitoring.

After removing the calvaria, the encephalon, including the brainstem, was carefully removed between the first and third day following formalin injection. The trigeminal nerve was sectioned at its root entry zone to maximally preserve its cisternal segment and ganglion. The ICA was sectioned after emerging from the cavernous sinus (ophthalmic segment). The entire cavernous segment of the ICA was included in the dissection. The skull bases were then cut using an oscillating autopsy saw, producing 22 parallelepiped blocks. Each block contained the entire cavernous sinuses, trigeminal nerve, proximal branches, and the cavernous ICA.

2.2. Microdissection

A standardized protocol was used to expose the intracavernous carotid‐trigeminal interface. Firstly, the dural layers of the lateral wall of the cavernous sinus and the trigeminal cave were progressively separated under magnification using a surgical microscope (Leica M720 OH 5). During this procedure, the superolateral aspect of the trigeminal ganglion and the three main branches of the trigeminal nerve were identified. These were exposed using a microsurgical technique, avoiding traction on the neurovascular structures.

Next, intracavernous microdissection identified the plane between the medial aspect of the anterior part of the trigeminal structures and the lateral aspect of the cavernous segment of the ICA. Gentle lateral traction of the nervous elements, under direct visual control, amplified this virtual space. All bridging structures were documented photographically and registered in a computerized database.

2.3. Histological examination

In 10 of the blocks obtained from five heads, the exposed tissue bands between the lateral aspect of the cavernous ICA and the medial aspect of the trigeminal ganglion or V1 were sectioned and collected. The fragments were immersed in formalin and embedded in paraffin. Histological examination was then performed using optical microscopy and hematoxylin–eosin‐safran staining.

3. RESULTS

The trigeminal nerve is surrounded by a rich dural environment which is key to understanding ICA‐trigeminal nerve relationships. We first present dissection results, followed by a histological description of this interface.

3.1. Dural environment of the carotid‐trigeminal interface

The cisternal segment of the trigeminal nerve ran in the posterior fossa and inferiorly crossed the insertion of the tentorium on the petrous bone, or posterior petroclinoid fold. It then entered a dural foramen, the porus trigeminus, which is the entrance of the trigeminal cave in which the trigeminal ganglion was located. The latter was a dural evagination of the dura mater's inner layer, also called the cerebral layer or dura propria. This was located just dorsal to the trigeminal impression, a small notch at the superomedial edge of the petrous bone. The trigeminal cave was similar to a three‐digit‐glove situated between the dura mater's inner and outer (or periosterodural) layers (François et al., 2010).

The arachnoid membrane extended from the posterior cranial fossa, as a pocket into the trigeminal cave. It lined the trigeminal cistern , which surrounded the trigeminal nerve, and ended at the trigeminal ganglion midportion. Since no cerebrospinal fluid was interposed, the anterior part of the trigeminal ganglion slightly adhered to the trigeminal cave. Three branches emerged from the anterior part of the trigeminal ganglion, the V1 (ophthalmic), V2 (maxillary), and V3 (mandibular) divisions, which progressed towards the superior orbital fissure, foramen rotundum, and foramen ovale, respectively, to leave the intracranial space.

The cavernous sinus was limited by a dural envelope surrounding a venous space through which the cavernous segment (C4) of the ICA, and several cranial nerves, coursed. It was located dorsal to the dorsolateral aspect of the body of the sphenoid bone, just anterior and dorsal to the apex of the petrous part of the temporal bone. The floor of the cavernous sinus was composed of the external layer of the dura overlying the roof of the sphenoidal sinus (Destrieux et al., 1998). The roof of the cavernous sinus was roughly horizontal and was continued medially as the diaphragma sellae. The diaphragma sellae and both roofs of the cavernous sinuses were formed from inner dural layer joining both anterior petroclinoid folds. Laterally, at the anterior petroclinoid fold, this horizontal dural layer (the roof of the cavernous sinus) became vertical. The resulting lateral wall of the cavernous sinus then vertically descended to join the outer dural layer, where both formed the dura mater of the middle cerebral fossa. The pituitary gland was located in the midline, between both cavernous sinuses. It was enclosed in the hypophyseal sac made of inner dural layer connected to the diaphragma sellae. Consequently, the medial wall of the cavernous sinus was the lateral aspect of this dural bag, which followed the irregular shape of the pituitary gland. Anteriorly, the cavernous sinus was related to the superior orbital fissure, located between the body, lesser wing, and orbital plate of the greater wing of the sphenoidal bone. Posteriorly, the cavernous sinus was continued by the petroclival venous confluence (Destrieux et al., 1997), another interdural space, confluent to the cavernous sinus, inferior petrosal sinus, and basilar plexus.

The cavernous sinus contained the whole horizontal portion of the carotid siphon . The border between the lacerum and cavernous segments of the ICA was demarcated by the petrolingual ligament. The petrolingual ligament joined the apex of the petrous part of the temporal bone to the sphenoidal lingula, which was developed at the lateral aspect of the sphenoid body, just lateral to the carotid sulcus. At this level, the course of the cavernous segment of the ICA changed from vertical to horizontal, forming the posterior ICA genu. The ICA then continued horizontally along the sphenoid body to reach the medial aspect of the anterior clinoid process (clinoid segment). There, its direction changed again, and it ran dorso‐posteriorly to pierce the roof of the cavernous sinus. As the ICA emerged from the roof of the cavernous sinus (ophthalmic segment), it reached the subarachnoid space, where it developed into branches that participated in the circle of Willis, in which trigeminovascular fibers were described.

Several cranial nerves reached the cavernous sinus lateral wall. The trochlear nerve (IV) entered the posterior part of the roof of the cavernous sinus close to the crossing of the anterior and posterior petroclinoid folds. The oculomotor nerve (III) pierced the cavernous sinus roof anteromedial to it, in a slightly depressed area. Finally, the V1 anteriorly continued its course from the trigeminal cave. The oculomotor (III), trochlear (IV), and ophthalmic (V1) nerves then ran within the cavernous sinus lateral wall, disposed in this order from superior to inferior. The ophthalmic nerve progressed forward, near the medial surface of the dura and inclined upward in the lower part of the lateral wall of the cavernous sinus.

By contrast, the abducens nerve (VI) coursed within the cavernous sinus, penetrating the interdural space at the posterior aspect of the clivus, close to the petro‐occipital fissure. It ran within the petroclival venous confluence, where it turned around the lateral aspect of the ICA posterior genu. Finally, the VI coursed ventrolateral to the ICA, and medially to the V1. The III, IV V1, and VI finally reached the orbit through the superior orbital fissure.

The V1 and VI nerves adhered to the lateral surface of the cavernous segment of the ICA, and the anatomy of this interface is detailed in the next section.

3.2. The carotid‐trigeminal interface

An obvious intracavernous carotid‐trigeminal interface was observed in the 22 studied specimens, located between medial aspect of the ophthalmic nerve and the lateral aspect of the cavernous segment (C4) of the ICA.

The zone of stronger adhesion to the carotid wall started about 2 to 3 mm distal to the trigeminal ganglion (Figure 1). When gentle lateral traction of the nerve enlarged the virtual space between the V1 and the lateral aspect of the cavernous ICA, the adhesion zone took the form of a web of delicate tissue bands and filaments in all specimens. When the same procedure was performed for the anterior portion of the trigeminal ganglion, adhesion was softer, and only tiny, sparse tissue bands were observed in all cases.

FIGURE 1.

FIGURE 1

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Anatomical study of the carotid‐trigeminal interface. (a) Cadaver dissection: Lateral view of the cavernous sinus (right). The dura mater covering the trigeminal ganglion and the lateral wall of the cavernous sinus was carefully removed. The virtual space located between the medial surface of the ophthalmic nerve and the lateral aspect of the cavernous segment (C4) of the ICA was exposed and we observed a tight adhesion at about 2 mm of the TG for all our specimens (22 cavernous sinus). (b) Schematic representation: Enlargement of the region of interest. Exposure of the virtual space between V1 and ICA. Visualization of the fine band tissues stretched between V1 and ICA inside the cavernous sinus. aca, anterior cerebral artery; cica, cavernous segment of internal carotid artery; ica, internal carotid artery; ilt, inferolateral trunk = caroticocavernous trunk; mca, middle cerebral artery; ocm, oculomotor nerve; oph, ophthalmic nerve; opt, optic nerve; pca, posterior cerebral artery; sca, superior cerebellar artery; tg: trigeminal ganglion; * and **: sites of sampling for histological examination.

There was no bone separating the ICA and trigeminal ganglion in any case. However, the posterior part of the trigeminal ganglion was isolated from the ICA by the dural and arachnoid envelopes of the trigeminal cave and cistern. Thus, the posterior portion of the trigeminal ganglion did not contribute to the carotid‐trigeminal interface (Figure 2).

FIGURE 2.

FIGURE 2

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Histologic examination of adhesions between the medial surface of the trigeminal nerve (TG, V1) and the lateral aspect of the cavernous ICA. (a) Histologic section of tissue bands stretched between the trigeminal ganglion (TG) and the cavernous segment C4 of the ICA. (b) Histologic section of tissue bands stretched between the ophthalmic nerve (V1) and the cavernous segment (C4) of the ICA.

3.2.1. Histological examination

Nerve fibers were detected in the 10 samples collected at the interface between the V1 and ICA . A nerve trunk with branches was observed in two samples. Neurons were identified in three specimens and adipocytes in two. Additionally, blood vessels, collagen, and fibrous tissue were observed in all samples (Table 1).

TABLE 1.

Histologic study

Specimens Nervous fibers Neurons Blood vessel Adipocyte
1—V1‐R +++a + Yes Yes
1—TG‐R 0 0 Yes Yes
1—V1‐L +++a + Yes Yes
1—TG‐L 0 + Yes No
2—V1‐R ++ 0 Yes No
2—TG‐R NA NA NA NA
2—V1‐L ++ 0 Yes No
2—TG‐L NA NA NA NA
3—V1‐R ++ + Yes No
3—TG‐R + 0 Yes No
3—V1‐L ++ 0 Yes No
3—TG‐L 0 0 No No
4—V1‐R ++ ++ Yes No
4—TG‐R 0 0 Yes No
4—V1‐L ++ + Yes No
4—TG‐L + 0 Yes No
5—V1‐R ++ + rare Yes No
5—TG‐R + 0 No No
5—V1‐L + 0 Yes Yes
5—TG‐L 0 0 Yes No
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Note: The histologic examination showed the presence of nervous fibers in the thin tissue bands stretched between the ophthalmic nerve and the cavernous segment (C4) of the ICA at about 3 mm from the TG. For nervous fibers and ganglion cells, we estimated the density: 0: absence; +: low density; ++: medium density; +++: high density; (N), specimen number; V1, ophthalmic nerve; TG, trigeminal ganglion; R, Right; L, Left.

a

Presence of nerve trunk and branches.

Filaments were collected between the anterior part of the trigeminal ganglion and the ICA in eight specimens. In the remaining two specimens, these filaments were too delicate for histological preparation. Histological examination showed nerve fibers in three specimens that were less dense compared to those found between the V1 and the ICA. Neuronal ganglion cells and adipocytes were observed in a single specimen, and blood vessels in six specimens. Collagen and fibrous tissue were also present in all samples.

4. DISCUSSION

In the present study, we performed a cadaveric investigation of nerve fiber exchanges between the perivascular plexus around the intracavernous ICA and trigeminal nerve. Microanatomical dissection, with the assistance of a surgical microscope, enabled the determination of neural filaments crossing the virtual space between the lateral wall of the cavernous ICA and the medial aspect of the ophthalmic division and, less frequently, between the cavernous ICA and the anterior portion of the trigeminal ganglion. The neural nature of these fibers was confirmed by histological analysis. These findings have important neurophysiological and clinical implications.

The trigeminal nerve is involved in several physiological phenomena, such as facial and intercranial pain perception and the modulation of cerebral blood flow. Therefore, many pathological conditions involve the trigeminal system; this is the case for primary headaches (migraine, tension headache, cluster headache), but also for secondary types of craniofacial pain. As the pathophysiology of these conditions is not completely understood, questions persist, particularly regarding the anatomy of innervation of the intracranial compartment.

Neural tracing studies have shown that the dura mater and large cerebral vessels are innervated by trigeminal fibers. However, no anatomical studies have documented the branches through which these fibers potentially join the cerebral vasculature. The French anatomist Hovelacque (1927) mentioned the existence of fine branches connecting the trigeminal ganglion and the ophthalmic nerve to the perivascular plexus, as mentioned in his anatomy textbook, in the French language only (Hovelacque, 1927). Similarly, Northfield (1938) mentioned connections that were found by Sheehan between the trigeminal ganglion and the perivascular plexus in eight specimens using gross dissection. These results were, however, not published, and the only trace of this observation is Northfield's assertion that Sheehan had mentioned them in a personal communication (Northfield, 1938).

These findings were not reproduced by other anatomists, such as Penfield & McNaughton (1940), although these authors consistently observed pain perception in the trigeminal region during intraoperative mechanical, electrical, or heat stimulation. It is possible that the delicate nature of these branches, as demonstrated in the present study, caused the heterogeneity of these results. While barely visible to the naked eye, these observations would have been more difficult in the era before the development of most tracing techniques and the operating microscope. Another factor is that the nature of these structures is difficult to assert when histological techniques are not used, which may have contributed to them receiving less attention in anatomical dissection.

Studies on this topic using neural tracers, or the degeneration method, suited to the investigation of small structures, particularly flourished in the eighties. Our findings converge with these results in many aspects, across both techniques and species. In a seminal work, Mayberg et al. (1981) demonstrated that following application of horseradish peroxidase to the proximal segment of the middle cerebral artery in cats, this marker could be found in the ipsilateral trigeminal ganglion (Mayberg et al., 1984). Similar studies in rats, using horseradish peroxidase or true blue tracer, also demonstrated retrograde labelling of ganglionic neurons (Arbab et al., 1986; Arbab et al., 1988; Edvinsson, 2011; Edvinsson et al., 1989). In turn, when agglutinin‐conjugated horseradish peroxidase was injected directly into the trigeminal ganglion, fibers were labeled in the cerebral arterial circle (of Willis), the anterior cerebral artery, and the rostral part of the basilar artery (Arbab et al., 1986).

Using intraganglionic injection in rats, Arbab et al. (1986) described a sparse network of trigeminal fibers located near the smooth muscle layer of the cerebral arteries (Arbab et al., 1986; Arbab et al., 1988). Studies in felines have shown that these fibers bundle together and lie either within the adventitia, or between the adventitia and the media, but not within the media or the endothelium (Liu‐Chen et al., 1986; Liu‐Chen, Han, & Moskowitz, 1983; Liu‐Chen, Mayberg, & Moskowitz, 1983). Marked trigeminal fibers were mainly located at the level of the ipsilateral internal carotid, middle cerebral artery, posterior communicating artery, posterior cerebral artery, the rostral part of the basilar artery, and the anterior cerebral artery (Arbab et al., 1986; Arbab et al., 1988; Mayberg et al., 1984).

The cell bodies that were marked in the ganglion when horseradish peroxidase or true blue tracer was applied to the middle cerebral artery were situated among cell clusters that project to the cutaneous territory of the ophthalmic nerve (Mayberg et al., 1984; O'Connor & van der Kooy, 1986). It has been suggested that this anatomical organization relates to the hemicranial distribution of vascular‐triggered headaches. Indeed, while all three trigeminal divisions perform the innervation of the cerebral meninges, the innervation of the cerebral arteries seemed to be particularly related to branches of the ophthalmic nerve (May & Goadsby, 1999b).

In a study on the pain‐sensitive structures, Ray and Wolf (1940) highlighted that pain resulting from stimulation of larger arteries of the forebrain was experienced in the area of the eye. In a similar study, Mayberg et al. (1984) highlighted that headaches induced by intravenous injection of histamine were abolished by procaine blockade of the ophthalmic nerve (Mayberg et al., 1981; Ray & Wolff, 1940). Furthermore, a reduction of migraines following trigeminal rhizotomy or bulbar tractot0omy was observed only when the ophthalmic nerve was rendered analgesic.

In experiments utilizing nerve fiber degeneration in monkeys, Ruskell and Simons (1987) observed delicate trigeminal branches joining the adventitia of the internal carotid artery at the icavernous part of the ophthalmic nerve, starting at 1.5 mm from the trigeminal ganglion (Ruskell & Simons, 1987). The authors observed morphological differences in those branches compared to the neighboring perivascular ones, as the former contained unmyelinated and numerous myelinated fibers of various diameters, and the latter had infrequent myelinated fibers of, mostly, uniformly small diameter.

Recently, Fontaine et al. (2018) revisited this topic in a study characterizing intracranial pain perception in patients undergoing awake craniotomy. In addition to sites over the dura mater, they observed pain sensitivity over several small pial vessels in the frontal, temporal, parietal, and insular lobes. Their mechanical stimulation caused referred pain, primarily in the territory of the ophthalmic nerve (Fontaine et al., 2018). That pain was elicited in pial structures and during small vessel stimulation raises important questions about the true extent of the intracranial trigeminal sensory territory.

In addition to their importance for vascular pain, the anatomical connections with the perivascular carotid plexus described in this study may also be part of the anatomical correlates that enable the trigeminovascular system to mediate vasomotor responses. The strong implication of the trigeminovascular system in cerebral vasodilation (Goadsby et al., 1997; Kumada et al., 1977; Lambert et al., 1984; Sakas et al., 1989) seems to be related to the vasodilator neuropeptides (calcitonin gene‐related peptide, substance P, and neurokinin A) contained in trigeminal fiber endings (Macfarlane & Moskowitz, 1995). In this context, the calcitonin gene‐related peptide was suggested to play an important role in migraines (Edvinsson, 2017).

This study has limitations. Only morphological aspects were investigated, without any functional or biochemical techniques for fiber characterization. Therefore, this analysis did not discriminate between the types of axons and the proportions of their subpopulations, such as autonomic or sensory, and afferent or efferent. However, this report contains the most detailed description of cavernous trigeminal‐perivascular connections to date. Future investigations could distinguish the different types of fibers in the trigeminocarotid connections and determine the actual extension of the intracranial ophthalmic trigeminal territory. Although important evidence has been reported in experimental animal systems, the present study addressed the anatomical specificities of the human trigeminovascular system.

5. CONCLUSION

The results of the present study show that nervous fibers regularly cross the virtual space in the carotid‐trigeminal interface of the human cavernous sinus. A zone of strong adhesion with the horizontal portion of the artery was observed for the ophthalmic nerve, in which delicate neural filaments were abundant. Although lower in number and density, similar structures were observed in the zone of soft adhesion between the anterior part of the trigeminal ganglion and the ICA. These findings have potential physiological and physiopathological implications and are especially important for the trigeminovascular system and related disorders. As the present results do not enable the exact nature (sensory, autonomic) of the axons to be affirmed, further investigation is necessary.

ACKNOWLEDGMENTS

The authors sincerely thank the Association du Don de corps du Centre Ouest and those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude. We are grateful to “La Fondation des Gueules cassées,” which funded this study.

Terrier, L‐M. , Bergemer, A‐M. , Destrieux, C. & Maldonado, I.L. (2022) Anatomical study of the carotid‐trigeminal interface: The missing link in the trigeminovascular system? Journal of Anatomy, 241, 1303–1309. Available from: 10.1111/joa.13765

DATA AVAILABILITY STATEMENT

N/A.

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