Positional cervical Doppler ultrasonography suggesting proximal vertebral artery obstruction in Bow Hunter syndrome: a case report
This case report describes a patient with Bow Hunter syndrome who presented with dizziness and cerebellar infarctions, where positional cervical Doppler ultrasonography successfully identified intermittent proximal left vertebral artery obstruction during neck rotation, guiding subsequent imaging confirmation and conservative management.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The human body relies on a delicate network of blood vessels to deliver oxygen to the brain, and in the neck, two major arteries called the vertebral arteries run upward to feed the back portion of the brain. For most people, these vessels remain open and flowing regardless of how they turn their heads. However, a rare condition known as Bow Hunter syndrome occurs when a specific head movement, usually a sharp turn to one side, causes one of these arteries to kink or collapse temporarily. This dynamic blockage cuts off blood flow, potentially leading to dizziness, fainting, or even a stroke. Because the problem only happens during movement, standard medical scans taken while a patient lies still often miss the culprit entirely, leaving doctors to search for a cause that vanishes the moment the patient stops moving.
A team of researchers at the University of Fukui and other institutions recently documented a case that highlights how doctors can catch this elusive problem. They treated a 73-year-old man who arrived at the hospital with sudden dizziness, nausea, and vomiting. Initial scans revealed that he had suffered small strokes in the back of his brain, specifically in the left occipital lobe and the right cerebellum. At first, the medical team could not find a clear reason for these events. The patient's arteries appeared normal when he was lying still, and his heart rhythm was steady, ruling out common causes like blood clots from the heart or hardening of the arteries. It was only after a week in the hospital, when the patient accidentally turned his head to the right while reaching for an object, that his dizziness returned. This specific trigger led the team to suspect Bow Hunter syndrome.
To investigate, the doctors performed a specialized ultrasound test while the patient turned his head. They placed a sensor on the left side of his neck to listen to the blood flow in the vertebral artery. When the patient faced forward, the blood flowed smoothly. But the moment he turned his head to the right, the sound of the blood flow changed dramatically. The ultrasound showed a chaotic, back-and-forth pattern, indicating that the blood was struggling to get through a severe narrowing. Interestingly, after holding the head in that turned position for about 30 seconds, the flow began to improve slightly, though it remained sluggish. This specific pattern of flow suggested that the blockage was happening higher up in the artery, closer to where it branches off from the main body, rather than at the spot where the sensor was listening.
Armed with this clue, the team used advanced imaging to look at the artery while the patient turned his head. They took detailed pictures of the blood vessels in both the neutral position and the turned position. These images revealed the physical cause: as the man turned his head to the right, the proximal part of his left vertebral artery, located near the top of the chest and bottom of the neck, bent sharply and narrowed into a slit-like shape. This kinking was not caused by a bone spur or a tumor pressing on the vessel, but rather by the movement of the neck itself deforming the flexible artery. A final, more invasive test using dye and X-rays confirmed that blood flow dropped significantly during this rotation.
The researchers concluded that the patient's strokes were caused by this rotation-induced kinking, which likely reduced blood flow enough to starve parts of the brain or encouraged a small clot to form. Because there was no fixed object like a bone pressing on the artery, the team decided against surgery. Instead, they treated the patient with aspirin to prevent clots and instructed him to avoid turning his head sharply to the right. He wore a soft neck collar for support and was discharged after 26 days. Over the following year, he experienced no further symptoms. This case demonstrates that by combining a simple ultrasound test that tracks blood flow changes with targeted imaging, doctors can locate the source of these dynamic blockages even when standard scans fail, allowing for a treatment plan that avoids unnecessary surgery.
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