Application of bilateral transcranial Doppler ultrasound in diagnosing vertebral artery compression syndrome

Abstract

Background

Vertebral artery compression syndrome (VACS) is characterized by recurrent and reversible dizziness, consistently triggered by head rotation or hyperextension. Currently, no simple yet effective screening and diagnostic methods are available. This study aimed to explore the application of transcranial Doppler ultrasound with dual transducers (TCD-D) and a head stent in the screening and diagnosis of VACS.

Methods

From April 2018 to September 2024, three patients with dizziness upon head rotation, diagnosed as VACS, were enrolled. TCD-D was used to simultaneously monitor the real-time blood flow of the bilateral posterior cerebral arteries (PCAs) during the patients’ head rotation. Positional nystagmus was recorded by video goggles at the bedside. Additional examinations were performed to assess the otologic and cervical conditions. Seven control subjects were also included.

Results

Among the three patients, TCD-D results demonstrated a marked reduction in blood flow of bilateral PCAs upon head rotation, which provoked dizziness. A reactive hyperemic response was observed when the patients returned to the neutral position, supporting the diagnosis of VACS. In contrast, controls demonstrated only mild blood flow changes during non-specific head movements, without dizziness. Downbeat-dominant nystagmus, accompanied by complex horizontal components, was observed in all patients with VACS during head movements.

Conclusions

TCD-D is an effective, convenient, safe, and cost-effective tool for screening and diagnosing VACS. More importantly, it can be operated in the consultation room and simultaneous recording of positional nystagmus can improve diagnostic accuracy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-026-04798-5.

Background

Vertebral artery compression syndrome (VACS), refers to recurrent, reversible episodes of dizziness that are sometimes accompanied by visual disturbances, syncopal attacks, and, in severe cases, posterior circulation ischemia or stroke. These symptoms are consistently triggered by head rotation or hyperextension, which is easily misdiagnosed as benign paroxysmal positional vertigo (BPPV) [1–3]. The primary mechanism of VACS is attributed to the compression by the cervical musculoskeletal abnormalities during head rotation or hyperextension on both vertebral arteries (VAs), or on the dominant VA, resulting in vertebrobasilar insufficiency [4–7]. In the literature, digital subtraction angiography (DSA), dynamic contrast-enhanced computed tomography (dcCT), and dynamic contrast-enhanced magnetic resonance imaging (dcMRI) are used for VACS diagnosis but have drawbacks: DSA is invasive and cannot visualize bilateral VAs synchronously during symptom onset; dcCT and dcMRI are non-routine, time-consuming, hindered by difficulties in posture maintenance and contrast agent limitations. Doppler ultrasound is a non-invasive, cost-effective tool for quantitative hemodynamic assessment in VACS, well-tolerated across ages, but traditional modalities only examine one side sequentially, which may lead to misdiagnosis due to arterial dominance and asymmetric flow patterns.

Given the underlying mechanism of VACS, simultaneous assessment of VA blood flow on both sides represents the most reliable approach for screening and diagnosis of VACS. To optimize the examination method, we employed TCD with two ultrasonic probes (TCD-D) and a head stent to simultaneously assess blood flow in both posterior cerebral arteries (PCAs) while inducing head rotation or hyperextension. This study aimed to investigate the feasibility of this method for screening and diagnosing VACS.

Methods

This study is a retrospective case-control study. This study adhered to the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) review by the Medical Ethics Committee of Peking Union Medical College Hospital (No. I-25PJ1561). All the authors approved the final version and agreed to publish the article. All the participants gave written informed consent for the publication of their clinical details in this study, and no identifiable information was included in this study.

We enrolled patients with VACS who presented to the Department of Otorhinolaryngology, Peking Union Medical College Hospital, from December 2017 to June 2024. Demographic data, onset symptoms and disease course of the patients were collected in detail. All patients underwent audiological and vestibular function tests, radiological imaging and TCD-D. We also enrolled in 7 healthy control subjects, none of whom had a history of chronic diseases, particularly no history of dizziness.

TCD-D (Model 2000 S, Chioy Co., Ltd., China) was conducted using two 2-MHz probes, which were secured with a stable stent on both sides of the patient’s head to ensure consistent placement. The probes were positioned slightly anterior to the upper ear margin and tilted posteriorly (the posterior temporal window), and the detection depth was set to 65–70 mm. After minor adjustments, the optimal blood flow signals were obtained, where the angle between the probes and the PCAs was typically maintained at 60°-90°. Once stable spectral waveforms were acquired, the ipsilateral common carotid artery was compressed; if no change or an increase in blood flow velocity (BFV) was observed, this confirmed the accurate localization of the PCA.

The mean blood flow velocity (mBFV) of both PCAs was measured synchronously. Real-time blood flow spectra were recorded concurrently during both the static phase and the provocative head movement. For the baseline measurement, patients were instructed to sit or lie in a neutral position for 2 min to establish the baseline BFV. Subsequently, they were directed to sequentially rotate their head laterally to both sides, flex the neck forward, and extend it backward, ultimately adopting the position that elicited their symptoms. If the sitting position was intolerable, the examination was performed in the supine position. Throughout the examination, a sonographer was present for supervision, assisted with probes fixation as needed, and ensured patient safety. This testing procedure was conducted in accordance with previous literature [8, 9].

Results

Patients with VACS

Three patients diagnosed with VACS were enrolled, all male, with a mean age of 46.0 ± 13.1 years and a mean disease duration of 1.8 ± 1.3 years. Only one patient had a definite history of head and neck trauma. These three cases were highly representative: one patient exhibited bilateral cervical transverse foramen stenosis at different levels (right C1 and left C6) during head rotation; one patient had bilateral cervical transverse foramen stenosis at the same level (C4 and C5 bilaterally); and one patient presented with left VA dysplasia, accompanied by compression of the right VA due to stenosis of the right C6 transverse foramen. TCD-D outcomes revealed a significant reduction (10%-30% of the baseline) in bilateral PCAs blood flow in all three patients during head rotation, as well as a transient increase (110%-140% of the baseline) in blood flow when their heads returned to the neutral position. One patient underwent DSA, and the result was consistent with TCD-D.

Case 1

A 31-year-old male patient presented with a two-year history of progressive vertigo triggered by leftward head rotation and extension, accompanied by blackouts, nausea, limb weakness, and low-pitched tinnitus in both ears. He had no history of chronic diseases. Physical examination using video goggles in the consultation room revealed faint spontaneous left-beating nystagmus. Upon leftward head rotation, a brief left-beating nystagmus was observed, followed by downbeat nystagmus, which became more pronounced with head extension. After maintaining this position for a few seconds, the downbeat nystagmus ceased, followed by a transient left-beating nystagmus, and subsequently, a stable right-beating nystagmus emerged (see Video 1.1). Head and neck computed tomography angiography (CTA) revealed the left VA originating from the aortic arch, with both VAs patent and no obvious dominance. The bilateral posterior communicating arteries (PCoAs) were not visualized. However, narrowing of the left C6 transverse foramen was observed, with the left VA forming a relatively large angle at this location. Additionally, the right VA initially followed a tortuous course between C1 and C2 vertebrae (see Fig. 1).

Fig. 1.

CTA of Case 1 in neutral position. A The left VA originated from the aortic arch. B The right VA followed a more tortuous course between cervical vertebrae C1 and C2 compared to the left VA. C The left VA formed a relatively large angle at the left C6 transverse foramen

TCD-D was conducted to assess bilateral PCAs simultaneously. In the neutral head position, TCD-D demonstrated normal mBFV in both PCAs (Left: 32 cm/s; Right: 35 cm/s). However, during leftward head rotation and extension, a marked reduction of blood flow was observed (Left: 5 cm/s; Right: 10 cm/s), coinciding with immediate dizziness. Over time, partial restoration of blood flow to approximately 50% of baseline levels (Left: 20 cm/s; Right: 20 cm/s) was noted, corresponding with a subjective improvement in symptoms. Prolonged monitoring indicated that blood flow remained at this diminished level. Upon returning to the neutral position, a transient overshoot of mBFV was observed (Left: 35 cm/s; Right: 42 cm/s; see Video 1.2).

Afterwards, the patient underwent DSA and the results indicated that in the neutral position, both VAs appeared normal. However, when the head oriented to the left, the left VA became obstructed at the C6 transverse foramen, while the right VA occluded at the C1-C2 levels. A compensatory flow from the anterior to the posterior circulation via the right slender PCoA was observed, along with augmentation of the left VA’s blood supply through a communicative branch from the left occipital artery (see Fig. 2). The DSA finding correlated well with TCD-D, further confirming the diagnosis of VACS. The patient was referred to the orthopedic department for further evaluation. Given the partial alleviation of symptoms due to compensatory collateral circulation, a conservative treatment approach was adopted, involving cervical collar use and neck immobilization. Over a six-month follow-up period, the patient reported partial symptom relief.

Fig. 2.

DSA findings of Case 1. A Interruption of blood flow in the right VA between the cervical vertebrae C1 and C2. B The right posterior communicating artery was slender, with visible compensatory anteroposterior blood flow. C Interruption of blood flow in the left VA at the left C6 transverse foramen. D The left occipital artery’s communicating branch compensated for blood supply to the left VA. Black arrow: VA; red arrow: posterior communicating artery; blue arrow: posterior cerebral artery; orange arrow: occipital artery and its branch supplying blood to the VA

Case 2

A 52-year-old male presented with a 3-year history of dizziness, accompanied by limb weakness, blurred vision, and bilateral aural fullness, manifesting as presyncope upon tilting his head backward and yawning. The patient reported a history of cervical whiplash 15 years ago. During the physical examination, when he forcefully extended his head backward and opened his mouth wide, a slight left-beating nystagmus was initially observed. After a few seconds, a downbeat nystagmus appeared, lasting for more than 10s, followed by a brief right-beating nystagmus and ultimately returning to left-beating nystagmus (see Video 2.1).

Static CTA revealed narrowing of the bilateral C4 and C5 transverse foramina, with the left C4 being the most constricted, and absence of distinct visualization of both PCoAs (see Fig. 3A-C). Cervical X-ray showed dislocation of the C3 and C5 cervical vertebrae (see Fig. 3D). Cervical MRI indicated slight protrusion of the intervertebral discs at C4-C7. During TCD-D test, blood flow in both PCAs nearly disappeared instantaneously when the patient extended his head and opened his mouth forcefully, with the patient experiencing significant dizziness simultaneously. Upon closing his mouth or altering his head position, the blood flow rapidly increased, accompanied by a transient rebound effect, and the patient’s symptoms alleviated and resolved completely (see Video 2.2). The diagnosis of VACS was confirmed. Following a comprehensive evaluation and consideration of the patient’s preferences, a conservative treatment approach was selected. The patient’s symptoms have been partially controlled by avoiding extreme head rotations.

Fig. 3.

Radiological imaging findings of Case 2. A-C CTA: bilateral narrowing of the C4 and C5 transverse foramina, with the most severe stenosis observed in the left C4 transverse foramen. D Cervical X-ray: displacement of the C3-C5 vertebral bodies, accompanied by narrowing of the C4-C6 intervertebral spaces

Case 3

A 55-year-old male presented with a six-month history of episodic dizziness and right tinnitus, which occurred upon leftward head rotation and tilting. His symptoms resolved upon returning to a neutral position. The patient had a history of atherosclerosis. A mild spontaneous left-beating nystagmus was initially observed. Upon symptom provocation, a downbeat nystagmus appeared, accompanied by horizontal bidirectional nystagmus (see Video 3.1).

Cervical X-ray demonstrated bilateral stenosis of the C3-C4 and C5-C6 intervertebral foramina, with slight posterior displacement of the C5 vertebra. Cervical MRI revealed degenerative changes in the cervical spine, with mild intervertebral disc bulging from C4 to C7. Head and neck CTA showed significant hypoplasia of the left VA along its entire length, as well as narrowing of the right C6 transverse foramen (see Fig. 4). TCD-D demonstrated bilateral PCAs occlusion following leftward and upward head rotation, with a marked reduction in mBFV (Left: mBFV decreased from ~ 40 cm/s to 5 cm/s; Right: mBFV decreased from ~ 45 cm/s to 10 cm/s), and the onset of dizziness. Upon returning the head to the midline, a notably reactive hyperemic response was observed (Left: mBFV increased to ~ 50 cm/s; Right: mBFV increased to ~ 60 cm/s; see Video 3.2), with resolution of symptoms. Given the patient’s willingness, a conservative treatment approach was chosen, with regular follow-up to monitor disease progression.

Fig. 4.

Radiological imaging findings of Case 3. A-B CTA: significant stenosis of the left VA along its entire course, with severe intracranial stenosis (>70%). C CTA: stenosis of the right C6 transverse foramen. D CTA: left intracranial VA segment was not visualized. E Cervical MRI: mild bulging of the C4-5 intervertebral disc. F Cervical X-ray: posterior displacement of the C5 vertebra

Control group

The 7 healthy control subjects had a mean age of 28.0 ± 5.2 years, including 3 males and 4 females. During left and right neck rotation, neck flexion, neck extension, and the symptom-provoking head positions identical to those that elicited symptoms in the 3 patients with VACS, the ratio of the mBFV of the bilateral PCAs to that in the neutral head position ranged from 71.4% to 112.3%, with a mean value of 91.4% ± 9.7%, and none of the subjects reported any discomfort, particularly dizziness. After the head was returned to the neutral position, the corresponding ratio ranged from 83.3% to 119.8%, with a mean value of 102.8% ± 8.1%.

Discussion

Based on the early explanation in the background, the pathogenesis of VACS involves simultaneous compression of bilateral VAs or compression of the dominant VA. Therefore, simultaneous detection of posterior circulation blood flow occlusion during a specific head position would facilitate a more accurate and intuitive diagnosis of VACS. Currently, a range of diagnostic tools are employed to identify VACS, each with its own advantages and limitations. As the current gold standard for VACS, DSA provides a dynamic visualization of VA blood flow and intracranial collateral circulation during head movement. However, DSA does not allow for simultaneous visualization of both VAs during symptom onset, and its invasive nature poses certain risks, rendering it unsuitable for some patients, particularly children [10]. DcCT is also an effective diagnostic tool, offering detailed imaging of both VAs and their anatomical relationship with surrounding structures, which is valuable for surgical planning [2, 11–13]. However, it is not clinically routine. The main reason is that patients must maintain the symptom-provoking posture during scanning, which is highly challenging for those with severe symptoms. Involuntary movement compromises image quality and diagnosis. Moreover, dcCT cannot be repeated due to contrast agents, and CT radiation poses health risks. DcMRI, while advantageous in visualizing soft tissues, has limited utility in assessing bony structures, which are often the underlying causes of VACS. Furthermore, MRI’s prolonged scanning period makes it less tolerable for patients to maintain a specific head posture, particularly one that triggers symptoms. Doppler ultrasound is a highly effective, non-invasive, and dynamic method for quantitatively assessing the hemodynamic changes in VAs during symptomatic episodes, including flow reduction, disappearance, compensatory circulation, and recovery [14]. It is easy to apply in clinical settings, cost-effective, and well-tolerated in both adults and children, with negligible adverse effects, rendering it a promising tool for VACS screening and diagnosis [15, 16]. However, traditional ultrasonography examines one side at a time and does not provide a simultaneous view of both VAs. Unilateral or sequential Doppler can also be misleading because of arterial dominance, rapid collateral compensation, and asymmetric flow patterns.

In this study, we used TCD-D to simultaneously detect both PCAs for the screening and diagnosing VACS. The rationale for monitoring bilateral PCAs instead of VAs or the basilar artery is as follows: ① Complexity of VA anatomy: the VAs follow intricate courses through the neck, and compression can occur at either the same level bilaterally, as observed in Case 2, or at different levels, as in Case 1. This makes simultaneous observation of both VAs during neck rotation exceedingly challenging [9]; ②Limitations in basilar artery visualization: basilar artery assessment requires access through the occipital window, necessitating manual probe stabilization against the occiput. This can compromise signal stability and limit neck rotation angles during examination. Additionally, placing the probe on the occiput is impractical for patients unable to tolerate a seated position, particularly those requiring a supine examination; ③Advantages of PCA monitoring: as terminal branches of the basilar artery, the flow dynamics of bilateral PCAs reflect obstructions within the basilar artery, indirectly indicating both VAs involvement. Furthermore, both PCAs can be reliably visualized via the bilateral temporal windows. For conventional TCD, simultaneous visualization of both PCAs is almost infeasible, and head-turning maneuvers further complicate the examination. The implementation of dual ultrasonic transducers in conjunction with a head frame offers a more precise and efficient method for obtaining concurrent bilateral PCAs imaging. This approach enhances procedural efficiency, reduces examination time, and improves patient tolerance, particularly for those requiring supine positioning.

In this study, TCD-D effectively confirmed VACS in all cases. All the patients demonstrated good cooperation and experienced no adverse effects. The accuracy of TCD-D was further validated by DSA in Case 1, while the other two patients benefited from timely TCD-based diagnosis and appropriate treatment, despite forgoing DSA due to its invasive nature. To the best of our knowledge, only one prior study, conducted by Sturzenegger et al. in the 1990s, employed a similar approach to diagnose vertebrobasilar ischemia. Their study successfully diagnosed 4 cases of vertebrobasilar ischemia out of 14 suspected cases [17]. In the present cases, the mBFV of both the PCAs decreased to 10%-30% of the baseline value when the patients turned their heads via TCD-D. After the patients returned their heads, mBFV exhibited a brief rebound (reaching 110%-140% of the baseline). The findings are in accordance with existing literature which used unilateral or bilateral TCD [9, 17, 18]. It has been reported that BFV decreases ≤ 60% of baseline in patients with other types of paroxysmal positional vertigo and normal controls, and ≤ 110% of baseline when returning to neutral position, with inconsistent reproducibility of BFV changes and no clear correlation with symptoms [17]. In the health control group in this study, the changes in mBFV during any specific head position alteration were minimal, approximately 10% relative to the baseline value. The maximum reduction in BFV did not exceed 30% of the baseline value, which was far less pronounced than that observed in the 3 patients with VACS (who exhibited a 70%–90% reduction from baseline). Upon returning the head to the neutral position, a slight blood flow rebound was also observed in the control group, at only approximately 2% and not exceeding 20% of the baseline value, which was lower than that in the VACS patients (10%–40%). Besides, we consider that TCD-D allows for the observation and quantitative assessment of compensatory blood flow to some extent, as observed in Case 1. Symptom relief was achieved when blood flow recovered by 50%, and blood flow further increased when the head returned to the neutral position. These findings were confirmed by DSA, which verified the accuracy of TCD-D.

Notably, another typical sign aiding screening for VACS is downbeat-dominant nystagmus, with or without horizontal components, triggered by eccentric head positions. In Case 1, when the head was turned to the left, downward nystagmus and brief leftward nystagmus were observed, followed by the development of stable rightward horizontal nystagmus, which lasted for 1 min before subsiding. In Case 2, as the symptoms were provoked, downward nystagmus and brief rightward nystagmus emerged, eventually leading to a reversal from right-beating to left-beating nystagmus. In Case 3, during induced movements, downbeat nystagmus appeared, accompanied by bidirectional horizontal nystagmus. Hale et al. reported a case in which downbeat nystagmus was detected during DSA, confirming that the downbeat nystagmus originated from posterior circulation ischemia [19]. Current theory posits that the origin of the downward and horizontal nystagmus in VACS patients is likely due to hyperfunction of the anterior and horizontal semicircular canals, caused by ischemia of the anterior vestibular artery, branches arising from the posterior circulation [20, 21]. The direction of the horizontal component is attributed to the asymmetric functioning of both labyrinths [22, 23]. Furthermore, the spontaneous reversal of horizontal nystagmus is assumed to be due to central compensatory mechanisms [23]. In the three cases, the emergence of downbeat nystagmus during symptom provocation, coinciding with the peak of posterior circulation ischemia. Downward nystagmus combined with TCD-D is likely to enhance the screening and diagnosing efficiency of VACS. However, if the patients did not rotate their head to the extreme position that induced maximal ischemia in the posterior circulation, downbeat nystagmus may not occur, and some horizontal nystagmus could be detected. Therefore, it is crucial to carefully inquire about the positions that trigger the patient’s symptoms, and these positions should be specifically and thoroughly examined during the examination to avoid misinterpreting nystagmus that could interfere with the diagnosis, like BPPV [24].

The main limitation of this study is the small sample size, primarily attributed to the extremely low incidence of VACS. Owing to its rarity, VACS is highly prone to misdiagnosis in outpatient settings. The method described herein demonstrates feasibility for outpatient application. However, further diagnostic validation with a larger sample size is required in future studies.

Conclusions

Previous literature has established the provocation method and validated the corresponding physiological responses [14, 16, 19], while the present study quantifies the underlying hemodynamic mechanism through bilateral flow monitoring via TCD-D. TCD-D offers distinct advantages of simplicity, cost-effectiveness, non-invasiveness, and excellent patient tolerance with minimal adverse effects, rendering it a highly efficient tool for the screening, diagnosis, and severity assessment of VACS. Downbeat nystagmus is another key symptom elicited during VACS symptom provocation. In the future, synchronous monitoring of nystagmus and bilateral PCAs blood flow using TCD-D may facilitate more accurate diagnosis of VACS.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

VACS

Vertebral artery compression syndrome

TCD-D

Transcranial Doppler ultrasound with dural probes

PCA

Posterior cerebral artery

BPPV

Benign paroxysmal positional vertigo

VA

Vertebral artery

DSA

Digital subtraction angiography

dcCT

Dynamic contrast-enhanced computed tomography

dcMRI

Dynamic contrast-enhanced magnetic resonance imaging

CTA

Computed tomography angiography

MRA

Magnetic resonance angiography

mBFV

Mean blood flow velocity

PCoA

Posterior communicating artery

Authors' contributions

HY Sun collected the data of the present cases, conducted the literature review, and drafted the initial manuscript. YH Hu performed the TCD-D examinations and interpreted the corresponding results. Y Chen carried out radiological examinations and corresponding data analysis. XB Zhang conducted the DSA and analyzed the related results. YC Yang assisted in polishing the manuscript. SJ Wang organized the audiologic and vestibular function tests. HY Wu provided supervisory oversight for the intellectual content of the manuscript, led the study design, and revised the manuscript.

Funding

This work was supported by National Natural Science Foundation of China (82571329), Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (2023-RW320-03) and National High Level Hospital Clinical Research Funding (2022-PUMCH-C-041).

Data availability

The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study adhered to the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) review by the Medical Ethics Committee of Peking Union Medical College Hospital (No. I-25PJ1561). The informed consent to participate was obtained from all the participants.

Consent for publication

All the authors approved the final version and agreed to publish the article. All the participants gave written informed consent for the publication of their clinical details in this study, and no identifiable information was included in this study.

Competing interests

The authors declare no competing interests.