"Twists and turns" that neurology can't ignore

During reading, I often heard that "the vertebral artery of this patient is a little tortuous".
At that time, I did not pay much attention to this concept.
Recently, a patient with pontine infarction was admitted to the ward, and the vertebrobasilar artery was very dilated and tortuous.
That's what triggered my in-depth study of the sign
.

Author: Cao Xiaotang This article is published by the author authorized by the author, please do not reprint without authorization
.

Definition and Epidemiology Vertebrobasilar dolichoectasia (VBD), first described by the Italian anatomist Giovanni Morgagni in 1761, is an uncommon arterial disease characterized by dilation, lengthening, and tortuosity of the vertebrobasilar arteries [ 1]
.

 In the past, VBD was mainly found at autopsy.
Later, with the development of imaging technology, angiography, CT and MRI were widely used in clinical practice, which improved the ability to identify VBD
.

The prevalence of VBD in the general population is currently unknown
.

However, studies on some specific populations have shown that its prevalence is 0.
05% to 18% [2,3].
For example, the prevalence of VBD is about 2% in the first stroke population [4], and about 2% in patients with posterior circulation infarction.
is 3.
7%[5]
.

To date, there are no racial or ethnic differences in the prevalence of the disease
.

The predisposing age is 60-80 years old, more men than women
.

 Anatomical structure The V4 segment of the vertebral artery, the subdural segment, enters the dura mater between the hypoglossal nerve and the anterior root of the first cervical nerve, ascends anterior to the medulla oblongata, and joins the contralateral vertebral artery at the inferior border of the pons to form the base Arteries (Basilar artery, BA)
.

The starting point of BA is generally located at the midpoint of the pontine sulcus, and it ascends to the pontine peduncle sulcus to divide into the left and right posterior cerebral arteries
.

BA has an average length of 30mm and a width of 1.
5-4.
0mm[6]
.

The vertebral artery has a close anatomical relationship with the hypoglossal, glossopharyngeal, vagus, accessory, facial, vestibulocochlear, abducens, trigeminal, trochlear, and oculomotor nerves (Figure 1)
.

This close relationship makes cranial nerves susceptible to compression when the diameter or orientation of the vertebrobasilar artery changes
.

Figure 1 Anatomy of the relevant cranial nerves; a) The cadaveric specimen shows the relationship between the proximal end of the brainstem basal facial cranial nerve and the vertebrobasilar artery; b) T2 coronal view shows that the oculomotor nerve (triangle arrow) runs through the posterior cerebral artery (black arrow) Between the superior cerebellar artery (white arrow); c) Axial T2 view shows that the abducens nerve leaves the brainstem at the pontomedullary junction (black arrow), and the facial and vestibulocochlear nerves emerge at the pontomedullary junction (white arrow); d ) Axial T2 shows the ventral pons at the level of the trigeminal root entry zone (white arrows) showing the right abducens nerve (triangular arrows); e) Axial T2 showing the glossopharyngeal nerve (white arrows) exiting from both sides of the medulla oblongata Brain stem, just rostral to the vagus nerve; f) Axial T2 view shows the hypoglossal nerve (black arrow) emerging from the lower end of the medulla oblongata and exiting the base of the skull through the sublingual canal
.

Etiology and pathogenesis VBD is more common in elderly male hypertensive patients.
Therefore, atherosclerosis caused by hypertension is considered to be one of the main risk factors for the development of VBD [7]
.

However, other studies have shown that atherosclerosis may not play an important role in the pathophysiological mechanism of VBD, which is only secondary to the morphological and hemodynamic changes caused by VBD [8]
.

The reasons are as follows: atherosclerosis mainly involves the intima and endothelium of the arteries, VBD mainly involves the media, there are multiple gaps in the inner elastic layer, and the media is thinned secondary to smooth muscle atrophy and degeneration of reticular fibers
.

In addition, the incidence of atherosclerosis and hypertension was significantly higher, but the incidence of VBD was lower [9]
.

This also suggests that atherosclerosis may not be the main underlying cause of VBD
.

At present, it is believed that the main pathophysiological mechanism of VBD is abnormal vascular remodeling and abnormal connective tissue in the arterial wall caused by the imbalance of matrix metalloproteinase and antiprotease activities [9,10]
.

In addition, intracranial arterial dilatation is associated with dilation of the descending aorta [11] and coronary arteries [12], suggesting that VBD may be part of systemic vascular disease
.

The specific pathogenesis is shown in Figure 2
.

Studies have also found that VBD is associated with polycystic kidney disease, Ehlers-Danlos syndrome, Marfan syndrome, neurofibromatosis type I, Fabry disease, Pompe disease, and sickle cell disease, suggesting that it may have a genetic predisposition
.

VBD has also been reported to be associated with infections (eg, syphilis, varicella-zoster virus, etc.
), dissection, and IgG4-related diseases
.

Figure 2 Flow chart illustrating that abnormal vascular remodeling due to increased blood flow or pressure is the main pathophysiological mechanism of VBD.
Clinical manifestations Most patients with VBD are asymptomatic and discovered incidentally [9]
.

Symptomatic clinical manifestations fall into two broad categories—compressive symptoms and vascular events [13] (including transient ischemic attack, ischemic stroke, subarachnoid hemorrhage, etc.
)
.

Compressive symptoms result from the dilated ectopic vertebrobasilar artery compressing surrounding tissues, including the brainstem and cranial nerves
.

Compression of the brainstem and nucleus doubt can lead to limb weakness, pyramidal tract signs, dizziness, dysphagia, unsteady walking, and tinnitus
.

Almost all cranial nerves can be compressed, but the trigeminal, facial, and vestibulocochlear nerves are commonly compressed
.

The most common symptoms are trigeminal neuralgia and hemifacial spasm
.

Other signs and symptoms include nystagmus, tinnitus, and hearing loss due to vestibulocochlear nerve compression, vision loss and homotropic hemianopia due to optic nerve compression, diplopia and Horner syndrome due to compression of the abducens, trochlear, and oculomotor nerves, Hoarseness and dysphagia caused by compression of the glossopharyngeal and vagus nerves
.

Ischemic stroke is the most common clinical manifestation of VBD and the most common cause of VBD-related death [14]
.

VBD accounts for about 10% of patients with first cerebral infarction
.

The most common location of lesions was the brainstem, accounting for about 40%, especially the pons, followed by the posterior cerebral artery (29%), thalamus (22%), cerebellum (2%), and other regions (2%)
.

The main manifestation is the performance of perforating artery involvement
.

The pathogenesis is due to the following reasons: decreased forward blood flow in patients with VBD, and decreased mean systolic blood flow velocity, which in turn leads to an increased risk of thrombosis and thrombus occlusion of perforating arteries, resulting in perforator occlusion; lengthening and angulation of the vertebrobasilar artery leads to The arterial branch opening is deformed, and the blood supply of the perforating arteries is reduced, resulting in infarction in the blood supply area of ​​the pontine perforating arteries; the hemodynamic changes of the vertebrobasilar artery lead to vascular endothelial damage and secondary atherosclerosis
.

Bleeding in patients with VBD is severe and fatal, with a prevalence of 0.
0-6.
6% in patients with prolonged dilation
.

Intracerebral hemorrhage occurs because of pathological changes in the arterial wall, such as defects in the inner elastic lamina and thinning of the media due to smooth muscle atrophy
.

Elongation and degree of ectopic vertebrobasilar artery were also associated with bleeding
.

Subarachnoid hemorrhage is usually confined to the basal cistern
.

Based on limited data, predictors of bleeding were antiplatelet use, hypertension, female gender, and basilar artery diameter >10 mm
.

Hydrocephalus is a rare complication of VBD, mainly due to direct or indirect compression of the third ventricle floor or midbrain aqueduct causing cerebrospinal fluid circulation disorders, mainly normal pressure hydrocephalus
.

Other less common manifestations include central sleep apnea and cerebellar ataxia
.

Imaging diagnosis mainly relies on imaging.
DSA is the gold standard for diagnosing the disease, but its use is limited because it is invasive and cannot show the relationship between the vertebrobasilar artery and surrounding tissues.
Currently, CT, CTA and MRA are more used.
for diagnosis
.

Smoker et al.
[15] first proposed the diagnostic criteria for VBD based on CTA, including three quantitative indicators, namely bifurcation height reflecting prolongation, offset reflecting tortuosity, and basilar artery diameter reflecting dilation, as shown in Table 1
.

Bifurcation height and offset level 2 and above are abnormal
.

 Table 1 Diagnostic criteria for VBD based on CT and MRI[15,16] Figure 3 Smoker's diagnostic criteria; a) Axial T1 enhancement in the mid-pont shows the degree of basilar artery deviation; b) Sagittal T1 enhancement shows the height of the basilar artery bifurcation Some special imaging signs to be aware of include intraluminal thrombosis and hyperintense vascular signs
.

Both CTA and MRA can be used to assess intraluminal thrombosis in VBD, which manifests as a filling defect, see Figure 4
.

The hyperintense vascular sign on FLAIR sequences may be caused by decreased blood flow velocity, especially in posterior circulation TIA or stroke
.

Due to laminar flow, this sign is more obvious near the pipe wall, see Figure 5
.

The crescent-shaped hyperintensity of the vessel wall on the T1 sequence indicates the presence of an acute intramural hematoma, which is related to the rupture and growth of the intracranial aneurysm, as shown in Figure 6
.

Fig.
4 A 67-year-old man presented with facial paralysis, gaze palsy, and right limb weakness; axial CTA at the level of a) clivus and b) sphenoid sinus showed marked basilar artery dilatation (white arrow) and intraluminal thrombosis (Black triangle arrow)Fig.
5 Axial Flair shows hyperintense vascular sign, more obvious near the vessel wall (white arrow)Fig.
6 a) Axial non-enhanced CT image shows a hyperattenuating crescent-shaped intramural hematoma (triangle arrow) ;b) Axial CTA showing dissection involving dilated basilar artery (white arrow); c) Axial DWI showing multiple cerebellar infarcts (black arrow); d, e) Axial non-enhancing (d) and enhancing 6 hours later (e) T1 sequence showing increased volume of intramural hematoma (triangular arrow) and increased size of dissection (white arrow in e)
.

The hematoma does not have the characteristic crescent-shaped T1 hyperintensity due to the presence of more acute isodensity bleeding in the hematoma; f) Axial non-contrast CT obtained 2 days later, after the patient presented with acute deterioration of mental status and dyspnea, shows the ventricle Internal hemorrhage (triangle arrow) and massive subarachnoid hemorrhage (white arrow)
.

Treatment There is no specific treatment for VBD itself, and the existing treatment options are mainly for the treatment of VBD-related complications
.

Several studies have attempted to repair VBD with various surgical techniques, such as altering hemodynamics by reducing blood flow to the posterior circulation, or other direct surgical interventions, including resection and arterial bypass grafting, but the effect is unclear
.

Endovascular interventions, such as blood flow shunting through the use of stents with or without coils, have shown more promising results than open surgery
.

However, most of them are currently based on small case studies
.

The treatment of VBD-related ischemic stroke is controversial, and some studies have shown that aspirin or warfarin does not reduce the recurrence of VBD-related ischemic stroke and even increases the risk of bleeding
.

However, other studies have shown that warfarin may be effective, and randomized controlled studies are currently lacking
.

Therefore, for VBD-related ischemic stroke, the risks and benefits must be carefully weighed
.

There is currently no standard effective treatment for compressive symptoms
.

Several treatment options are available to manage VBD-induced symptoms of drug-refractory nerve compression, particularly trigeminal neuralgia and hemifacial spasm, including radiofrequency ablation, gamma knife radiation surgery, and botulinum toxin injections
.

The most effective treatment reported is microvascular decompression, which has now emerged as a safe and efficient surgical technique to relieve neurovascular compression syndrome
.

Key knowledge points ➤ It is now believed that the main pathophysiological mechanism of VBD is vascular remodeling and abnormal arterial wall connective tissue due to an imbalance between matrix metalloproteinase and antiprotease activities
.

➤Three quantitative indicators for evaluating VBD: bifurcation height reflects elongation, offset reflects tortuosity, and basilar artery diameter reflects dilation
.

➤Most patients with VBD are asymptomatic and are found incidentally
.

➤ Symptomatic clinical manifestations can be divided into compressive symptoms and vascular events, including TIA, ischemic stroke, and subarachnoid hemorrhage
.

➤ The most frequently described ischemic lesions were in the brainstem, especially the pons, followed by the posterior cerebral artery (29%), thalamus (22%), cerebellum (2%), and other regions (2%)
.

➤ There is no specific treatment for VBD itself.
There is currently no randomized controlled study on the use of antithrombotic drugs for ischemic vascular events, and the risks and benefits need to be carefully weighed in clinical practice.
There are also many methods for compressive symptoms, including radiofrequency ablation.
, gamma knife radiosurgery and botulinum toxin injection and microvascular decompression
.

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