What is Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)?
Rotational vertebral artery syndrome (RVAS), also known as Bow Hunter syndrome, is a rare condition that can be corrected surgically. It causes lack of blood supply to the brain due to temporary blockage of a main artery in the spine when the head and neck are turned.[1][2][3] When you rotate your head and neck, it can compress the vertebral artery, a crucial artery in the spine.[1] The nickname ‘Bow Hunter syndrome’ comes from a case where the patient had a type of stroke while practicing archery with a continuously turned head.[4] The phrase ‘Bow Hunter stroke’ has been used since 1978 to describe this issue.[5]
In order to understand RVAS, it’s important to know about the vertebral artery’s structure. The vertebral arteries, which stem from larger arteries known as the subclavian arteries, usually dive into the sixth cervical vertebra in the spine (or the seventh in 7.5% of cases) and go upward through a hole in each neck vertebra. After going through the hole in the first cervical vertebra, these arteries follow the curve of this vertebra and move into a region in the back of the head, where they enter a large opening, the foramen magnum.[6]
What Causes Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)?
RVAS, or Radiculopathy, Vertebral Artery Syndrome, comes about because of a few different things and can be caused by:
* Aging neck joints, especially things like bone spurs, fibrous bands, and slipped discs
* Abnormally shaped vertebrae
* Tumors, for example spinal osteochondroma
* Narrowing of the bone canal in the spine, as seen with a genetic disorder known as hereditary exostosis
* Extra bony canal in the sideways sticking out part of the vertebrae
Another reason can be overly large or swollen neck muscles.
Risk Factors and Frequency for Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
RVAS often occurs in people between 50 and 70 years old and is more common in males. Certain factors increase the risk of developing this condition, such as old age, high blood pressure, osteoarthritis, high blood cholesterol, diabetes, smoking, and heart disease.
The most frequent site of compression is at the junction between the first and second vertebra in the neck (C1-C2), followed by the junction between the fourth and fifth vertebra (C4-C5). In a study of 126 cases, the most often affected region of the vertebral artery was V2 (58% of the time), followed by V3 (36% of the time). Osteophytes, or bone spurs, usually appear at the C4-C5 and C5-C6 levels.
- RVAS typically occurs in those aged 50 to 70 and is more prevalent in males.
- It’s linked to increased age, high blood pressure, osteoarthritis, high cholesterol levels, diabetes, smoking, and heart disease.
- The areas most often affected are the C1-C2 and C4-C5 segments of the spine.
- In a study of 126 cases, 58% had the V2 region of the vertebral artery affected, followed by 36% in the V3 region.
- Bone spurs most commonly occur at the C4-C5 and C5-C6 levels.
Signs and Symptoms of Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
RVAS or Rotational Vertebral Artery Syndrome can cause a range of symptoms, from minor issues like temporary loss of consciousness or feeling faint, to severe problems like strokes that affect the back part of the brain. These symptoms are usually brought on by moving the head from side to side within the normal range of motion, and generally get better when the neck is returned to a neutral position. These symptoms occur because there’s not enough blood flow to certain areas of the brain, including the labyrinth (a structure in the ear), the side of the lower part of the brain (lateral medulla), and the lower part of the cerebellum.
The main symptom of RVAS is vertigo, a sense of spinning, which can happen if the artery on the same side (ipsilateral) is squeezed at or below the fourth cervical vertebra (C4) or if the artery on the opposite side (contralateral) is squeezed at or above the third cervical vertebra (C3). Other symptoms can happening at the same time, such as tinnitus (ringing in the ears), headaches, diplopia (double vision), and ataxia (loss of control of body movements). But it’s important to note that these symptoms aren’t specific to RVAS and are also seen in disorders that affect the neuro-vestibular system, which is responsible for balance and spatial orientation.
RVAS is rare, but a treatable diagnosis to consider in patients who are experiencing vertigo, feeling unsteady, feeling faint, or feeling lightheaded due to a problem originating in the neck (cervicogenic dizziness). Most often, these patients will show nystagmus, a condition causing the eyes to make repetitive, uncontrolled movements, usually in the direction of the damaged side, which tends to fade with time (habituation).
Testing for Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
When a doctor suspects that a patient may have Rotational Vertebral Artery Syndrome (RVAS), it is a challenging condition to diagnose. This is because the condition involves complex and dynamic features that require careful testing and inspection to identify the cause and extent of the problem. Advanced imaging techniques and in-depth clinical assessments are necessary. A technique called ‘dynamic rotational angiography’ is often the most reliable test to confirm an RVAS diagnosis.
Doctors generally follow a step-by-step approach to diagnosing someone presenting with cervicogenic dizziness, which means dizziness caused by a problem in the neck. The steps may include:
– An X-ray of the neck: To check for any old-age related changes in the neck that could be causing disc space to narrow, harden (sclerosis), abnormal bone growths (osteophytes), or misalignment of the vertebrae (olisthesis).
– Checking if turning the neck causes dizziness: If it’s positive, a special type of ultrasound called a ‘dynamic transcranial Doppler test’ may be used to rule out RVAS.
– If the neck turn does not provoke dizziness, further tests may be needed, including checking for specific types of vertigo (benign paroxysmal positional vertigo). Tests focusing on posture and neck rotation can also be done to rule out neck injuries from a whiplash accident.
If none of these tests confirm a diagnosis, then the cause of dizziness could be due to old-age related changes in the neck or Barré-Liéou syndrome. This syndrome occurs when sympathetic nerve fibers get compressed by a worn out neck joint
Doctors will also conduct or consider several additional tests to rule out other potential causes of dizziness, including checking your blood pressure while standing, balance tests, tests for cerebellum issues, impulse tests for the head, and recording voluntary eye movements.
Key elements in diagnosing RVAS are as follows:
– Videonystagmography (VNG): This test checks for any abnormal eye movements which suggests that the symptoms are stemming from the central nervous system.
– Dynamic/3-position digital subtraction angiography (DSA): This scan is done with the head in a straight, left, and right turned position.
Additionally, the doctor might use an ultrasound or cervical arterial duplex ultrasonography test as initial screening tests for patients suspected of having an obstructed artery below the third vertebra. They may also request imaging scans like Computed Tomography Angiography (CTA) or Magnetic Resonance Imaging (MRI) to check for any abnormal growth like fibrous bands, osteophytes, stenosis (narrowed arteries), infarction (tissue death due to insufficient blood supply), or even map the course of the vertebral artery. One way to conclusively diagnose RVAS is through DSA, which shows any artery blockage while the patient’s head is being rotated.
To confirm the diagnosis of RVAS, doctors often rely on ‘dynamic rotational angiography’. However, during these tests, doctors must avoid forcing or quickly rotating the patient’s neck movements. Once a diagnosis is confirmed, doctors can use electrophysiological tests (like motor-evoked potentials, somatosensory-evoked potentials, and brainstem auditory-evoked responses) to get baseline information before and after the surgical intervention.
Treatment Options for Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
Rotational vertebral artery syndrome (RVAS) is a rare condition, and there still isn’t a universally agreed-upon best treatment. There are several methods of addressing RVAS:
- Wearing a cervical collar (a medical device that supports your neck)
- Use of blood thinning medications
- Surgical decompression alone (surgery to relieve pressure on the arteries)
- Surgical decompression combined with fusion (a type of surgery where two or more bones are joined together).
Doctors usually suggest conservative treatment – or non-surgical options – when there are no solid abnormalities squeezing the vertebral artery. These conservative treatments include avoiding turning the head, wearing neck braces, and medicine to prevent blood clots. Some studies have even found that a combination of two blood thinning drugs can reduce the risk of strokes in people with transient ischemic attacks (temporary disruption in the blood supply to part of the brain) or minor ischemic strokes.
However, it’s worth noting that even with this conservative management, patients are still at risk of experiencing recurring strokes.
Surgical treatment can very much depend on the particular patient’s problem. Generally, doctors try non-surgical treatments first, and only resort to surgery if these treatments don’t work. The most common surgical method is decompression, with or without fusion, and it’s been found to be safe and very effective in preventing strokes caused by lack of blood flow.
It is crucial to choose the surgical approach based on the path of the artery. The specific location, extent, and cause of the blockage determine the surgical plan. For example, the upper neck region is best accessed through a back (posterior) approach, while blockages beneath this level can often be accessed through the front (anterior).
There have also been cases where other treatments, such as embolization (a procedure that inserts a substance to block or reduce blood flow) and angioplasty (a procedure to restore blood flow through the arteries), have been utilised. It’s not clear yet how much they help in the long run.
What else can Rotation Vertebral Artery Syndrome (Bow Hunter syndrome) be?
: Rotational Vertebral Artery Syndrome (RVAS) has symptoms that are generally linked with vertebrobasilar deficiency. This makes its diagnosis challenging as several other conditions share the same symptoms. These conditions include:
- Lateral medullary syndrome, also known as Wallenberg syndrome
- Sick sinus syndrome
- Hypersensitivity baroreceptor syndrome
- Menière syndrome
- Costen syndrome
- Anomalies in the cranio-vertebral region
- Beauty parlor stroke syndrome
- Cervical myofascial pain syndrome
- Barré-Liéou syndrome
- Proprioceptive cervical vertigo
- Migraine-associated cervical vertigo
These conditions need to be ruled out in order to accurately diagnose RVAS.
What to expect with Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
Choi and their team monitored 19 patients with RVAS who were treated using non-invasive methods. They found that none of these patients suffered from a stroke affecting the back part of the brain, known as a posterior circulation stroke, within around 37.5 months of monitoring. Plus, 4 patients even noticed their symptoms disappear during this time.
However, contrastingly, a review by Rastogi and their team found less positive results with the non-invasive treatment. Only 37% of patients experienced favorable outcomes. It was evident from their observations that surgical treatment generally led to more patients seeing their symptoms improve.
Possible Complications When Diagnosed with Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
Complications from RVAS can directly affect a patient’s quality of life and overall health. Therefore, being able to identify and manage these complications is key to effective treatment and prevention. Repeated minor strokes or ‘transient ischemic attacks’ can cause fainting and balance issues. Moreover, any falls resulting from these attacks could lead to more serious injuries.
Recurrent strokes in the back of the brain, a symptom of RVAS, could lead to permanent and potentially disabling neurological problems. One common associated condition is infarction, which can occur due to poor blood flow or an embolism (a sudden blockage of a blood vessel) from the affected vertebral artery.
In some cases, decompressing the spine alone may cause instability. Patients who have undergone cervical fusion may lose significant movement in their neck post-surgery. This joint is responsible for 50% to 70% of neck rotation and 15% of bending and stretching. Re-blockage can also occur, typically after back decompression, because of overlooked anterior fibrous bands.
Key Complications:
- Repeated minor strokes leading to fainting and balance issues
- Falls leading to injuries
- Recurrent strokes causing permanent neurological problems
- Infarction due to poor blood flow or sudden blockage
- Spinal instability from decompression
- Loss of significant neck movements after cervical fusion
- Potential re-blockage after back decompression
Recovery from Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
After surgical care for RVAS (Rotational Vertebral Artery Syndrome – a condition where turning the head can cause temporary restriction of blood flow), it’s essential to actively monitor for any signs of nerve damage or issues with blood vessels. Doctors often use tools like Doppler ultrasound or MRI (magnetic resonance imaging), which are types of imaging technology, to make sure the blood flow in the vertebral artery (which supplies the brain and spinal cord with blood) isn’t hindered.
Managing pain, looking after the surgical wound, and preventing infections are also key factors in post-surgery care.
During recovery, the goal is to slowly regain neck movement while avoiding positions that could bring back symptoms. Physical therapy plays a significant role here, focusing on easy movement exercises and strengthening the muscles in the neck that support the blood vessels.
It’s also crucial that patients are educated about safe neck movements and changes they can make in their daily life to prevent the issue from recurring and to promote overall health of the blood vessels leading to the brain.
Preventing Rotation Vertebral Artery Syndrome (Bow Hunter syndrome)
If you’re encountering regular phases of dizziness, fainting, feeling nauseous, losing your balance, or other unusual signs related to your nervous system during times when you turn your head, it’s important to see a healthcare professional to find out if you have RVAS (Rotational Vertebral Artery Syndrome). This condition can initially be treated without surgery with methods like keeping the neck still and using blood-thinning medication. However, careful monitoring by a specialist is crucial.
After taking a detailed personal medical history, doing a focused examination of you, and conducting needed tests, it is very important to figure out whether your dizziness and sense of spinning are caused by inner ear issues, other nerve-related conditions, or whole-body diseases. This helps doctors to make the best use of medical tests, minimize the risk of serious health issues, and cut down on unnecessary medical costs, which is especially important in countries with lower and middle incomes.
