Index
Symptomatic stenosis of the vertebral artery can cause vertebral insufficiency or stroke of the posterior territory of the cerebral circulation.
The vertebral arteries arise from the subclavian arteries , one on each side of the body, then enter deeply into the transverse process at the level of the sixth cervical vertebra (C6), or occasionally (in 7.5% of cases) at the level of C7.
They then proceed superiorly, into the transverse foramen of each cervical vertebra. Once they have passed through the transverse foramen of C1, the vertebral arteries travel through the posterior arch of C1 and through the suboccipital triangle before entering the foramen magnum.
Inside the skull, the two vertebral arteries join to form the basilar artery at the base of the Pons.
The basilar artery is the main blood supply to the brainstem and connects to the Circle of Willis to potentially supply the rest of the brain if one of the carotids is involved.
At each cervical level, the vertebral artery sends branches to the surrounding musculature through the anterior spinal arteries.
Structure and characteristics
The vertebral artery can be divided into four parts:
The prevertebral part : the V1 (preforaminal) segment travels up and back between the Longus colli and the Scalenus anterior. In front of it are the internal jugular and vertebral veins, which is crossed by the inferior thyroid artery.
The left vertebra is also traversed by the thoracic duct. Behind it is the transverse process of the seventh cervical vertebra, the sympathetic trunk and its lower cervical ganglion.
The cervical part: The V2 (foraminal) segment runs upward through the foramen in the transverse processes of the C6 to C2 vertebrae, and is surrounded by branches of the lower cervical sympathetic ganglion and by a plexus of veins that unite to form the vertebral vein in the lower part of the neck.
It is located in front of the trunks of the cervical nerves and follows an almost vertical course to the transverse process of the axis.
The Atlantic part : segment V3 Problems (extradural or extraspinal) of the C2 transversarium foramen on the medial side of the lateral Rectus capitis.
In addition, it is subdivided into the vertical part V3v that passes vertically upwards, crossing the root C2 and entering the transversary foramen of C1, and the horizontal part V3h, curved medially and posteriorly behind the superior articular process of the atlas, the anterior branch of the first cervical nerve on its medial side.
It then meets in the sulcus on the upper surface of the posterior arch of the atlas, and enters the vertebral canal passing under the posterior atlantooccipital membrane.
This part of the artery is covered by the semispinalis capitis and is contained in the suboccipital triangle, a triangular space delimited by the Rectus Capitis posterior major, the Obliquus superior, and the Obliquus inferior.
The intracranial part: segment V4 (intradural) pierces the dura mater and slopes towards the middle of the front part of the medulla oblongata; it is placed between the hypoglossal nerve and the anterior root of the first cervical nerve and below the first finger of the denticulatum ligament.
At the lower edge of the pons, it joins with the vessel on the opposite side to form the basilar artery.
Transverse process of the cervical vertebra. It targets the six transverse processes of the upper cervical vertebrae towards the skull as it rises into the foramina. It enters the skull through the foramen magnum, in front of the upper tooth of the denticulatum ligament.
Then, above, it rotates between the hypoglossal nerve and, below, the first cervical nerve, and continues towards the anterior surface of the medulla oblongata. It forms the basilar artery by joining with the other side at the lower edge of the pons. Here it becomes intracranial.
The vertebral artery has two sets of branches:
- Cervical.
- Cranial.
The neck is where the cervical branches detach and the skull where the cranial branches detach. The muscular and lateral spinal arteries are the cervical branches. The lateral spinals are divided into two branches by means of the intervertebral foramina.
These two branches supply the bodies of the vertebrae, the spinal cord, and its membranes. Before the vertebral artery touches the posterior occipito-atloid ligament, the muscular branches are detached. These branches serve the deep muscles of the neck.
The occipital and the deep and ascending cervical arteries fuse with these branches.
The vertebral artery in its course emits the following lateral branches:
- Meningeal branches.
- Anterior spinal artery.
- Posterior spinal artery.
- Spinal branches.
- Muscular branches.
- Posterior inferior cerebellar artery.
- Medullary branches.
The meningeal branches of the vertebral artery arise near the foramen magnum and supply the posterior cranial fossa and the falx cerebelli.
Each anterior spinal artery arises from the vertebral artery in the cranial cavity, descends anterior to the cord, and the two join to form a single trunk.
This trunk descends in the ventral midline of the spinal cord and enters the vertebral canal through the intervertebral foramina to supply the spinal cord.
The posterior spinal artery originates from the vertebral artery near the brainstem, descends posteriorly embedded in the posterolateral groove of the spinal cord, supplying the spinal cord.
The spinal branches of the vertebral artery arise in the neck, reach the spinal cord through the intervertebral foramina and supply it.
The muscular branches of the vertebral artery arise in the neck and supply the deep muscles of the neck.
The posterior inferior cerebellar artery (PICA) arises from the vertebral artery near the lower end of the olive. The posterior inferior cerebellar artery supplies the medulla oblongata, the choroid plexus of the fourth ventricle, the dentate nucleus, the cerebellar hemisphere, and the inferior vermis.
The medullary branches of the vertebral artery supply the medulla oblongata.
Vertebral artery injury
Vertebral artery injury accounts for less than 5% of all cervical arterial injuries, with penetrating trauma (more specifically, gunshot wounds), which is the most common form of penetrating injury, and motor vehicle accidents are the etiology of the majority of blunt vertebral artery injuries.
Almost 75% of vertebral artery injuries are asymptomatic due to their location and because the contralateral vertebral artery will likely provide sufficient flow to the posterior circulation (85%). 77
Additionally, the anatomic proximity of the epidural venous plexus along the C1 to C2 region, the most likely region of vertebral artery romalesion, results in arteriovenous fistula formation.
Physical and neurological findings, such as Horner syndrome, Wallenberg syndrome, cranial nerve palsies, and respiratory failure, should lead the physician to suspect a possible vascular injury.
Due to the relative rarity of this injury, management strategies for vertebral artery injury have been largely adopted from carotid injury data. Although accessible, surgical approaches to the vertebral artery can be challenging.
Surgical ligation of the proximal vertebral artery (at its origin) can be considered and performed by vascular surgeons in the context of acute trauma, especially in the context of a non-dominant vertebral artery injury.
However, endovascular ligation and reconstruction options should be considered first if a distal or middle vertebral artery injury occurs.
It is somewhat difficult to determine the true outcomes for patients with vertebral artery injury, as it is rare to have a severe, isolated injury.
It is estimated that although mortality ranges between 11% and 25%, only 5% of this mortality is directly attributable to injury to the vertebral artery.
Thrombosis or dissection of the vertebral artery
Vertebral artery thrombosis or dissection may follow minor neck trauma, especially rapid neck rotation. The site of occlusion is generally at the C1-2 level. Boys are more affected than girls (Ganesan et al, 2002).
Clinical features
The common features of vertebral artery injury are headache and brainstem dysfunction. Repeated episodes of hemiparesis associated with bitemporal throbbing headache and vomiting can occur and are easily misdiagnosed as basilar artery migraine.
The outcome is relatively good, survival is the rule, and chronic neurological disability is rare.
Diagnosis
The key to diagnosis is the presence of one or more areas of infarction on CT or MRI. The possibility of stroke leads to an arteriographic study, which reveals the occlusion of the basilar artery.
Treatment and administration
Long-term aspirin prophylaxis is a common recommendation, but its effectiveness has not been proven.
Vertebral artery stenosis
Extracranial ultrasound examination of the vertebral artery is limited to its origin from the subclavian artery, the transverse segments between the third and sixth vertebrae, and the loop of the atlas.
The diagnosis and classification of vertebral artery stenosis are more demanding than in carotid arteries. However, several studies defined PW Doppler criteria for evaluating vertebral artery stenosis that are comparable to those for the diagnosis of carotid artery stenosis.
For the evaluation of the vertebral arteries, it is important to consider the variability of the arterial caliber and the presence of numerous collateral pathways that allow delivery to the basilar artery even if there is a vertebral occlusion.
The flow in the vertebral arteries in more than 95% of the patients can be quantified by CDFI. This technique also favors the recognition of the origin, the proximal segment, the location of the extracranial vertebral stenosis, and the atlas loop.
In addition, normal values of flow velocities at the origin, proximal segment, and transverse segment have been identified by this imaging method. To evaluate the velocities in a vertebral artery, it is necessary to know the Doppler values of the contralateral artery.
The vertebral artery and carotid arteries, as many abnormalities in the contralateral vertebral artery (eg, aplasia, hypoplasia, stenosis, and occlusion) or severe stenosis in the carotid arteries with impaired vertebral artery blood flow can be demonstrated .
Vertebral artery stenoses are more commonly located at the origin of the subclavian artery, while the atlas loop and intracranial segment are less frequently affected. Finally, stenoses in the transverse segments are less common.
