A 70-year-old previously healthy man presents with episodes of presyncope - he feels
light headed and as though he is about to pass out. On your examination, his vital
signs are normal with no evidence of postural hypotension. Examination of his head
and neck, cardiovascular and neurological systems are unremarkable. You advise him
to keep a diary on the circumstances surrounding his episodes. Two weeks later he
is brought to the ER following a syncopal episode that occurred while shaving in his
bathroom.
DIAGNOSIS: Bow Hunter's Syndrome (BHS). BHS is a rare condition in which turning the
head mechanically compresses a vertebral artery and causes presyncope (or syncope)
by transiently cutting off blood flow to the posterior circulation. As seen in the
presented case, shaving, which requires head rotation, is a classic but often overlooked
trigger. The diagnosis can be confirmed by demonstrating vertebral artery flow changes
during head rotation using dynamic imaging. Treatment ranges from physical therapy
and motion restriction to surgical decompression, depending on severity.
The differntial diagnosis in the presented case includes the carotid sinus hypersensitivity
syndrome (CSHS), which, statistically, is actually a more likely diagnosis. As described
by MS IV Matthew Etts "CSHS is most commonly seen in older patients, particularly
men with carotid stenosis, vascular risk factors, neurodegenerative disease, or regional
head/neck pathology. CSHS is an exaggerated parasympathetic response of the sinoatrial
and antrioventricular nodes triggered by carotid sinus baroreceptor stimulation; this
leads to clinically significant AV block, bradycardia, and/or sinus pause/arrest and
an acute drop in cerebral perfusion with consequent presyncope or syncope. The diagnosis
of CSHS requires demonstrating syncopal/presyncopal events with any of the following
during carotid sinus massage (which must be accompanied by continuous cardiac and
blood pressure monitoring): a drop in SBP of 50 mmHg or greater; asystole for 3s or
more; or a mixure of these responses. For patients with severe symptoms care involves
permanent cardiac pacing, often with a dual-chamber pacemaker."