Vertebral Artery Ultrasound

Vertebral Artery Interventions: A Comprehensive Updated Review

Patients with posterior circulation ischemia due to vertebral artery stenosis account for 20 to 25% of ischemic strokes and have an increased risk of recurrent stroke. In patients treated with medical therapy alone, the risk of recurrence is particularly increased in the first few weeks after symptoms occur, with an annual stroke rate of 10 to 15%. Additionally, obstructive disease of the vertebrobasilar system carries a worse prognosis, with a 30% mortality at 2-years if managed medically without additional surgical or endovascular intervention. Percutaneous transluminal angioplasty and stenting of symptomatic vertebral artery stenosis are promising options widely used in clinical practice with good technical results; however, the improved clinical outcome has been examined in various clinical trials without a sufficient sample size to conclusively determine whether stenting is better than medical therapy. Surgical revascularization is an alternative approach for the treatment of symptomatic vertebral artery stenosis that carries a 10-20% mortality rate. Despite the advances in medical therapy and endovascular and surgical options, symptomatic vertebral artery stenosis continues to impose a high risk of stroke recurrence with associated high morbidity and mortality. This review aims to provide a focused update on the percutaneous treatment of vertebral artery stenosis, its appropriate diagnostic approach, and advances in medical therapies.

Accidente cerebrovascular isquémico de la arteria cerebral media

La segunda causa de muerte a nivel mundial corresponde a los ataques cerebrovasculares (ACV), de los cuales más de dos terceras partes son de origen isquémico. Causan discapacidad a largo plazo por lo que conocer la anatomía de la circulación cerebral y las posibles manifestaciones clínicas del ACV isquémico permite sospechar, diagnosticar y brindar un manejo oportuno y apropiado, reduciendo el impacto en la salud y la calidad de vida del paciente y sus cuidadores. Objetivo: relacionar los últimos hallazgos en la anatomía arterial cerebral, los mecanismos fisiopatológicos y las manifestaciones clínicas del ACV isquémico de la arteria cerebral media (ACM). Materiales y métodos: revisión de la literatura mediante la búsqueda con términos MeSH en la base de datos Medline, incluyendo estudios, ensayos y metaanálisis publicados entre 2000 y 2020 en inglés y español, además de otras referencias para complementar la información. Resultados: se seleccionaron 59 publicaciones, priorizando la de los últimos 5 años y las más relevantes del rango temporal consultado. Conclusiones: son escasos los estudios sobre la presentación clínica de los ACV, lo que sumado a la variabilidad interindividual de la irrigación cerebral, dificulta la determinación clínica de la localización de la lesión dentro del lecho vascular. La reperfusión del área de penumbra isquémica como objetivo terapéutico se justifica por los mecanismos fisiopatológicos de la enfermedad.

A preliminary study on colour Doppler ultrasound for the evaluation of intervertebral stenosis of the vertebral artery

AIM

To determine the optimal thresholds for assessing intervertebral segment stenosis through haemodynamic parameters of colour Doppler ultrasound compared with computed tomography (CT) angiography.

MATERIALS AND METHODS

Fifty-four patients diagnosed with intervertebral stenosis on colour Doppler imaging were included. Twenty patients with normal vertebral arteries constituted a control group. Peak systolic velocity at the intervertebral stenosis (PSV_IV-S) and the intervertebral segment distal to the stenosis (PSV_IV-D), end diastolic velocity at the intervertebral stenosis (EDV_IV-S), and the intervertebral segment distal to the stenosis (EDV_IV-D) were measured, and the ratios of PSV_IV-S/PSV_IV-D and EDV_IV-S/EDV_IV-D were calculated. Cut-off values for the diagnosis of <50%, 50-69%, and 70-99% stenosis were determined using a receiver operating characteristics curve.

RESULTS

The optimal cut-off values of haemodynamic parameters for evaluating the intervertebral artery for <50% stenosis were PSV_IV-S ≥81.5 cm/s, EDV_IV-S ≥24.5 cm/s, PSV_IV-S/PSV_IV-D ≥1.49, and EDV_IV-S/EDV_IV-D ≥1.28; for 50-69% stenosis were PSV_IV-S ≥137.5 cm/s, EDV_IV-S ≥36.5 cm/s, PSV_IV-S/PSV_IV-D ≥3.14, and EDV_IV-S/EDV_IV-D ≥2.75; and for 70-99% stenosis were PSV_IV-S ≥216 cm/s, EDV_IV-S ≥55 cm/s, PSV_IV-S/PSV_IV-D ≥4.31, and EDV_IV-S/EDV_IV-D ≥4.16. PSV_IV-S/PSV_IV-D was the most superior haemodynamic parameter, with areas under the curve of 1.000, 0.906, and 0.968 for the diagnosis of <50%, 50-69%, and 70-99% stenosis, respectively.

CONCLUSION

Colour Doppler sonography reliably identifies intervertebral stenosis. The results can be used as a preliminary reference for evaluating intervertebral stenosis.

Neurovascular coupling is not influenced by lower body negative pressure in humans

Cerebral blood flow is tightly coupled with local neuronal activation and metabolism, i.e., neurovascular coupling (NVC). Studies suggest a role of sympathetic nervous system in the regulation of cerebral blood flow. However, this is controversial, and the sympathetic regulation of NVC in humans remains unclear. Since impaired NVC has been identified in several chronic diseases associated with a heightened sympathetic activity, we aimed to determine whether reflex-mediated sympathetic activation via lower body negative pressure (LBNP) attenuates NVC in humans. NVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 11 healthy participants (aged 24 ± 3 yr). NVC assessments were made under control conditions and during LBNP at -20 and -40 mmHg. Posterior (PCA) and middle (MCA) cerebral artery mean blood velocity (V_mean) and vertebral artery blood flow (VA_flow) were simultaneously determined with cardiorespiratory variables. Under control conditions, the visual stimulation evoked a robust increase in PCA_Vmean (∆18.0 ± 4.5%), a moderate rise in VA_flow (∆9.6 ± 4.3%), and a modest increase in MCA_Vmean (∆3.0 ± 1.9%). The magnitude of NVC response was not affected by mild-to-moderate LBNP (all P > 0.05 for repeated-measures ANOVA). Given the small change that occurred in partial pressure of end-tidal CO₂ during LBNP, this hypocapnia condition was matched via voluntary hyperventilation in absence of LBNP in a subgroup of participants (n = 8). The mild hypocapnia during LBNP did not exert a confounding influence on the NVC response. These findings indicate that the NVC is not influenced by LBNP or mild hypocapnia in humans.NEW & NOTEWORTHY Visual stimulation evoked a robust increase in posterior cerebral artery velocity and a modest increase in vertebral artery blood flow, i.e., neurovascular coupling (NVC), which was unaffected by lower body negative pressure (LBNP) in humans. In addition, although LBNP induced a mild hypocapnia, this degree of hypocapnia in the absence of LBNP failed to modify the NVC response.

Six-year history of intermittent symptomatic bilateral vertebral artery stenosis: Imaging and therapeutic intervention

A 66-year-old man was evaluated for a 6-year history of disabling symptoms of typical intermittent vertebrobasilar (VB) insufficiency. Duplex scanning was "normal," but computed tomographic angiography (CTA) revealed significant bilateral proximal vertebral artery (VA) disease. Angiography with stent placement with the proximal right VA resulted in resolution of symptoms. Symptoms of VB insufficiency may occur from bilateral VA disease, most often involving both proximal segments. Duplex ultrasound has high specificity but relatively low sensitivity for finding hemodynamically significant VA disease. Further imaging with CTA or magnetic resonance angiography (MRA) will help in identification of disease. As with this patient, invasive angiography with percutaneous stenting of the most significantly stenosed VA often results in resolution of symptoms of VB insufficiency.