Continuing Education Activity

Rotational vertebral artery syndrome (RVAS), or Bow Hunter syndrome, is a rare but surgically amenable cause of vertebrobasilar insufficiency due to dynamic and reversible occlusion of the dominant vertebral artery. Head and neck rotation can lead to vertebral artery compression at the atlantoaxial or subaxial levels in the spine. Patients typically have a history of transient ischemic attacks, presyncope, syncope, or severe strokes in the posterior circulation. The predominant symptoms are vertigo and cervicogenic dizziness. The most common causes are degenerative lesions of the cervical spine, notably osteophytes, fibrous bands, and lateral disc herniations. Healthcare professionals must consider all potential causes when diagnosing the underlying pathology of vertebrobasilar insufficiency. Accurate diagnosis requires a thorough understanding of vertebral artery anatomy and the use of advanced imaging techniques, particularly dynamic rotational angiography, to identify arterial compression. Treatment strategies include both conservative management, such as avoiding head rotation and using cervical collars, and medical therapies, such as antiplatelet or anticoagulation therapy. In some cases, surgical intervention may be necessary to alleviate the compression. 

This activity examines the underlying pathology of this rare condition and explores the role of imaging techniques and clinical assessments in confirming the diagnosis. This activity also covers current therapeutic strategies, including medical management and surgical interventions, for both acute and chronic RVAS cases. In addition, this activity provides clinicians with comprehensive knowledge and practical skills to recognize, diagnose, and manage RVAS effectively. Furthermore, this activity also highlights the role of the interprofessional healthcare team in collaborating to optimize outcomes for affected patients.

Objectives:

• Identify the clinical manifestations and risk factors associated with rotational vertebral artery syndrome.

• Implement conservative management strategies for rotational vertebral artery syndrome, including cervical immobilization and medical therapy.

• Select optimal rehabilitation protocols to restore neck mobility and prevent symptom recurrence.

• Collaborate with multidisciplinary healthcare teams to develop comprehensive care plans for patients with rotation vertebral artery syndrome, ensuring optimal long-term outcomes and patient well-being.

Introduction

Rotational vertebral artery syndrome (RVAS), or Bow Hunter syndrome, is a rare but surgically amenable cause of vertebrobasilar insufficiency due to dynamic and reversible occlusion of the dominant vertebral artery.[1][2][3] Head and neck rotation can lead to vertebral artery compression at the atlantoaxial or subaxial levels in the spine.[1] The name Bow Hunter syndrome was first used to describe a patient who developed Wallenberg syndrome (a lateral medullary infarction) during archery practice with his head turned for extended periods.[4] This condition was termed 'Bow Hunter stroke' by Sorenson in 1978.[5] 

Understanding the anatomy of the vertebral artery is critical in understanding the pathogenesis of RVAS syndrome. The vertebral arteries originate from the subclavian arteries. They generally enter deep into the transverse process of C6 in most cases (C7 in 7.5% of cases) and ascend through the transverse foramen of each cervical vertebrae. After ascending through the transverse foramen of the atlas (C1), the vertebral arteries travel along the posterior arch of C1 and into the suboccipital triangle, where they enter the foramen magnum.[6]

Etiology

RVAS has a multifactorial etiology, with the most common causes including:

• Degenerative joints of the cervical spine, notably osteophytes, fibrous bands, and lateral disc herniations
• Malformed vertebrae
• Tumors such as spinal osteochondroma
• Bony stenosis of the vertebral canal, as seen in hereditary exostosis
• Accessory osseous canal in the transverse process
• Hypertrophied neck musculature [7][8][9][10][11][12][13][14][15][16][17]

Epidemiology

RVAS typically presents during the fifth to seventh decade of life and has a higher predilection for males.[5][7] Other risk factors associated with the condition include older age, hypertension, osteoarthritis, hyperlipidemia, diabetes, smoking, and coronary artery disease.[4][7][8] 

C1–C2 is the most common anatomical location of compression, followed by C4–C5.[5] In a series comprising 126 cases, the most common region of vertebral artery involvement was V2 (58%), followed by V3 (36%).[7] Osteophytes most commonly involve C4-C5 and C5-C6 levels.[18]

Pathophysiology

During head rotation, mechanical compression, kinking, or stretching of the vertebral artery can lead to transient vertebrobasilar insufficiency, characterized by symptoms such as dizziness, vertigo, or even stroke. This occlusion typically occurs at the atlantoaxial (C1-C2) or subaxial levels of the cervical spine. Anatomical variations, degenerative changes, or congenital abnormalities can predispose individuals to this condition.

History and Physical

The clinical presentation of RVAS is highly variable, ranging from transient ischemic attacks, presyncope, or syncope to devastating strokes of the posterior circulation. These symptoms are often triggered by head rotation within the normal physiological range to one side and generally improve upon returning the neck to a neutral position.[5][8] Clinical manifestations typically occur due to transient hypoperfusion of the labyrinth, lateral medulla, and inferior cerebellum.

The predominant symptomatology of RVAS is vertigo,[5][18] which may occur due to the ipsilateral vertebral artery compression at or below C4 or contralateral vertebral artery compression at or above C3.[5] This may be associated with concurrent symptoms such as tinnitus, headache, diplopia, and ataxia.[5] However, these reported clinical findings are not specific to RVAS and are commonly observed in disorders affecting the neuro-vestibular system.[4][19][20] 

RVAS is considered a rare but treatable differential diagnosis in patients presenting with cervicogenic dizziness, which may include vertigo, disequilibrium, presyncope, and lightheadedness.[5] Nystagmus is most often downbeat toward the side of the lesion and characteristically shows habituation.[21]

Evaluation

Evaluating RVAS involves a comprehensive approach to accurately diagnosing this dynamic and often elusive condition. Clinicians must utilize advanced imaging techniques and clinical assessments to identify the precise cause and extent of arterial compression. Dynamic rotational angiography is considered the gold standard for confirming an RVAS diagnosis.

The algorithmic approach to evaluating a patient presenting with cervicogenic dizziness includes the following steps:

• Plain x-ray of the cervical spine: To rule out degenerative cervical spine disorder (DCD) that leads to disc space narrowing, sclerosis, osteophytes, and olisthesis.
• Positive neck turn: If dizziness on neck turn is positive, a dynamic transcranial Doppler test should be performed to rule out RVAS.
• Negative neck turn: If dizziness on neck turn is negative, the below-mentioned steps should be performed.
  • A positional test should be performed to rule out benign paroxysmal positional vertigo.
  • A posturography/joint position error/smooth pursuit neck rotation test should be preferentially performed to rule out whiplash-associated disorder.
  • If still negative, the dizziness may be due to DCD/Barré-Liéou syndrome, caused by compression of sympathetic fibers by the degenerative cervical joints.[5]

Excluding other clinical differential diagnoses is also imperative by performing or considering the following:

• Postural measurement of blood pressure
• Romberg test
• Cerebellar signs
• Head impulse test or Unterberger test
• Video/electronystagmography [5] 

The cornerstones in the diagnosis of RVAS are listed below.

• Videonystagmography (VNG): Indicates a central origin of clinical symptomatology.
• Dynamic/3-position digital subtraction angiography (DSA): Performed with the head in a neutral position, 90° to the left and 90° to the right.[22]

Transcranial Doppler or cervical arterial duplex ultrasonography can be performed to screen patients with suspected dynamic vertebral artery compression below C3.[5] Patients should undergo computed tomography angiography (CTA) or magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) to assess for any fibrous bands, osteophytes, stenosis, infarction, as well as topographical mapping of the vascular course of the vertebral artery.[5] Diagnostic confirmation is achieved through DSA, which shows normal arteries in neutral head alignment and vascular occlusion or stenosis during head rotation in RVAS.

Dynamic rotational angiography is the mainstay of diagnosis.[3][4] However, precautions must be taken to avoid sustained end-of-range or quick rotational neck movements during such procedures.[5] Furthermore, electrophysiological examinations such as motor-evoked potentials, somatosensory-evoked potentials, and brainstem auditory-evoked responses provide baseline information preceding and following surgical intervention.[23][24]

Treatment / Management

RVAS is rare, and there is still no consensus on the best course of treatment. Different modalities of management include the following:

• Application of a cervical collar
• Use of anticoagulants
• Standalone surgical decompression
• Surgical decompression with fusion [5]

Conservative management is recommended when no identifiable structural abnormalities compressing the vertebral artery are found.[5] Conservative treatment includes avoiding head rotation, using cervical collars, and/or administering antiplatelet or anticoagulation therapy.[2] Dual-antiplatelet therapy has been shown to reduce the risk of strokes from 11.7% to 8.2% in cohorts with transient ischemic attacks or minor ischemic strokes.[2] However, patients under conservative management remain susceptible to recurrent ischemic strokes.[2]

As there are many potential causes of dynamic vertebral artery compression, surgical treatment targets each patient's specific pathology and is not standardizable across all patients. Most patients are offered conservative treatment initially and undergo surgical intervention if medical management fails.[2] Decompression (osteophytectomy) with and without fusion is the preferred surgical strategy in most cases.[25][26][27] Surgical decompression is safe and highly effective in preventing ischemic events.[18] In a study involving 126 cases, standalone decompression was used in 73% of cases.[7] Decompression alone was also performed in a study comprising 14 cases.[8] A fully endoscopic approach has also been reported in a case of C1 avulsion fracture.[28] 

The anatomical course of the vertebral artery is crucial in determining the surgical approach. The location, extent, and cause of occlusion dictate the surgical plan.[5] The C1–C2 region is best visualized via a posterior approach, whereas lesions below C3 (subaxial) are typically addressed via an anterior approach.[5][8] Visualization of the exact stenotic point, rather than the stenotic level, is pivotal during surgery.[22] Intraoperative indocyanine green (ICG) angiography, dynamic catheter angiography, and Doppler ultrasound are used for real-time assessment of patency and adequate decompression of the vertebral artery.[1][3] In addition, intraoperative angiography further allows for an intra-arterial remodeling balloon to improve surgical safety.[1] 

Cornelius et al described a patient with a focal vertebral artery dissection. After conservative management failed, the patient underwent coil embolization of the right vertebral artery to prevent further embolic events.[29] Procedures such as posterior inferior cerebellar artery (PICA)-to-PICA bypass, angioplasty, and stenting have also been reported to enhance collateral flow.[2] The practical long-term benefits of endovascular treatments are yet to be determined.[5]

Differential Diagnosis

RVAS presents with nonspecific symptoms consistent with vertebrobasilar deficiency. Commonly reported differential diagnoses include the following:

• Lateral medullary syndrome or Wallenberg syndrome
• Sick sinus syndrome
• Hypersensitivity baroreceptor syndrome
• Menière syndrome
• Costen syndrome
• Anomalies of the cranio-vertebral region
• Beauty parlor stroke syndrome
• Cervical myofascial pain syndrome
• Barré-Liéou syndrome
• Proprioceptive cervical vertigo
• Migraine-associated cervical vertigo [5][30][31]

Prognosis

Choi et al reported 19 patients with RVAS who were treated conservatively, and none of them developed a posterior circulation stroke over 37.5 months of follow-up. Furthermore, 4 patients experienced resolution of symptoms during this follow-up period.[32] 

Conversely, a review by Rastogi et al reported only a 37% favorable outcome among patients who were treated via a conservative approach.[19] Surgical management resulted in a more favorable resolution of symptoms for most patients.[7]

Complications

Complications of RVAS can significantly impact patient outcomes and quality of life. Recognizing and managing these potential complications is crucial for effective treatment and prevention. Repeated transient ischemic attacks can result in syncope and impaired balance, and falls associated with these attacks can lead to additional injuries. 

RVAS can also cause recurrent posterior circulation strokes, leading to permanent and disabling neurological deficits.[33] Infarction can occur following hemodynamic impairment or arterio-arterial embolism from the involved vertebral artery.[2] 

Decompression alone can lead to spinal instability.[8] Patients undergoing cervical fusion lose significant neck movements postoperatively, with the atlantoaxial joint responsible for 50% to 70% of rotation and 15% of flexion and extension.[5] Reocclusion may occur, most often following posterior decompression, due to missed anterior fibrous bands.[5]

Postoperative and Rehabilitation Care

Postoperative and rehabilitation care for RVAS is crucial for optimal recovery and long-term success. Postoperatively, patients are closely monitored for neurological symptoms and vascular patency, often utilizing imaging techniques such as Doppler ultrasound or MRI to ensure adequate decompression of the vertebral artery. Pain management, wound care, and prevention of complications such as infection are also prioritized.

Rehabilitation focuses on gradually restoring neck mobility while avoiding positions that could precipitate symptoms. Physical therapy is crucial, emphasizing gentle range-of-motion exercises and strengthening cervical muscles to support vascular structures. Patient education on safe neck movements and lifestyle modifications is essential to prevent recurrence and promote overall vascular health.

Consultations

Patients with RVAS often require consultations with a multidisciplinary team to ensure comprehensive care. Neurologists are essential for evaluating and managing neurological symptoms and assessing the risk of stroke. Vascular surgeons or neurosurgeons provide expertise in surgical intervention and postoperative care, while radiologists are critical for accurate imaging and diagnosis through techniques such as dynamic rotational angiography.

Additionally, physical therapists contribute to rehabilitation by developing tailored exercise programs to restore neck function and prevent recurrence. In some cases, consultations with cardiologists or hematologists may be necessary to manage comorbid conditions such as hypercoagulability or cardiovascular disease, further optimizing patient outcomes.

Deterrence and Patient Education

Patients experiencing episodes of dizziness, syncope, nausea, loss of balance, and other neurological symptoms during head rotation should be evaluated for RVAS by a medical professional. Symptomatic patients diagnosed with RVAS can initially be managed nonoperatively with neck immobilization and anticoagulation. However, they require careful monitoring under the supervision of a medical specialist.

Following a detailed history, focused examination, and pertinent investigations, it is essential to rule out vestibular, neural, and systemic causes of cervicogenic dizziness and vertigo.[5] In addition, it is imperative to maximize the clinical utility, minimize morbidity, and reduce healthcare resource wastage through proper dichotomization, especially in low- and middle-income nations.[5]

Enhancing Healthcare Team Outcomes

RVAS is a treatable condition that can lead to significant morbidity if not managed appropriately. Therefore, it is ideally managed through an interprofessional team approach led by healthcare professionals. Furthermore, it poses a diagnostic challenge because many other causes of vertebrobasilar insufficiency mimic this condition.

Healthcare professionals, including neurologists, vascular surgeons, and orthopedic surgeons, require advanced diagnostic skills to accurately identify RVAS using dynamic rotational angiography and other imaging techniques. Surgeons must possess expertise in performing precise surgical interventions tailored to the specific site of occlusion. Advanced practitioners and nurses should be adept at monitoring patient symptoms and facilitating postoperative recovery, ensuring early detection of complications. Pharmacists are crucial in managing medications, including antiplatelet or anticoagulation therapy, and educating patients on proper usage and potential adverse effects. Physical therapists design rehabilitation strategies to restore neck mobility and prevent symptom recurrence through tailored exercise programs.

Healthcare professionals must collaborate effectively and communicate clearly to implement the management plan and optimize patient outcomes. Given the potential severity of mismanaging RVAS, clinicians must be well-educated and prepared to deliver the highest quality patient care.

To enhance patient-centered care, the interprofessional healthcare team must prioritize the patient's preferences, needs, and values. This involves actively involving patients in their care plans, providing clear and accessible information, and addressing any concerns or questions they may have. Personalized care plans should take into account the patient's lifestyle, comorbidities, and personal goals, ensuring a holistic approach to treating individuals affected by RVAS.

Optimizing team performance necessitates fostering a culture of mutual respect, continuous education, and quality improvement initiatives. Regular training sessions on the latest RVAS research, treatment advancements, and best practices can keep the team updated and competent. Establishing protocols and guidelines for RVAS management in patients ensures consistency in care delivery while conducting performance audits and utilizing feedback mechanisms to help identify areas for improvement.