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Provoked Dizziness from Bow Hunter’s Syndrome

(A) Digital subtraction angiography (DSA) demonstrated focal stenosis of V2 segment of left vertebral artery (yellow arrow). (B) DSA revealed that the posterior circulation of the brain was otherwise normal beyond the level of stenosis.

(A) Digital subtraction angiography (DSA) demonstrated focal stenosis of V2 segment of left vertebral artery (yellow arrow). (B) DSA revealed that the posterior circulation of the brain was otherwise normal beyond the level of stenosis.

 

A 62-year-old man was experiencing debilitating bouts of dizziness provoked by head rotation until ultimately finding relief with cervical spine fixation. He had a history of coronary artery disease, human immunodeficiency virus, tobacco use disorder, and generalized anxiety, and initially presented to a routine primary care visit with 3 weeks of episodic dizziness. During these dizzy spells, he became unsteady on his feet and typically experienced tinnitus. His symptoms worsened when he turned his head to the left; this was occasionally followed by intense, albeit brief, headaches. He denied any episodes of syncope and did not experience chest pain, palpitations, or diaphoresis during these attacks. He had not experienced diplopia, dysarthria, focal limb weakness, or paresthesias. He had no ear fullness or hearing loss. He denied weight loss, fevers, or chills.

Assessment

A comprehensive neurologic examination including detailed oculomotor testing was unremarkable. He had a steady gait with no truncal sway. A Dix-Hallpike maneuver failed to reproduce his symptoms. However, on leftward rotation of the head to approximately 30-45 degrees, the patient experienced near syncope with nausea, and began to hyperventilate. Cardiovascular examination revealed no carotid bruits, a regular cardiac rhythm with no murmurs, jugular venous pressure estimated at 6 cm H2O, and normal radial and pedal pulses. A 12-lead electrocardiogram revealed normal sinus rhythm with an incomplete bundle block, and 48-hour Holter monitoring did not identify any brady- or tachyarrhythmias. The patient’s dizziness was attributed to possible benign paroxysmal positional vertigo (BPPV), or possibly a somatic manifestation of anxiety.

Over the ensuing month, his spells became more frequent and intense. Given his burden of cardiovascular risk, he was referred for magnetic resonance angiography, which revealed focal moderate-to-severe stenosis of the mid-V2 segment of the dominant left vertebral artery (Video 1). Given these findings, he was referred to a neurovascular specialist who recommended additional neurovascular imaging.

Diagnosis

The differential diagnosis for episodic dizziness is broad and includes myriad causes; the Table1234 highlights some of the most common etiologies. The breadth of the differential diagnosis and the fact that some episodes of dizziness represent life-threatening disorders (eg, stroke, vertebral artery dissection, ventricular arrhythmia) makes the evaluation of dizziness an oft-daunting task for generalists.

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-Paul A. Bergl, MD

This article originally appeared in the September 2017 issue of The American Journal of Medicine.

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