bow hunter 's syndrome ( bhs ) is caused by the compression of the dominant vertebral artery ( va ) against a fibrous band or osseous prominence by rotational head movement2,6,10 ) , leading to ischemic insult in the vertebrobasilar territory8,14 ) .
bhs presents as recurrent attacks of paroxysmal vertigo , nystagmus , and ataxia caused by head rotation5,8,10 ) . due to the rarity of this pathology
recently , we encountered 2 cases , which we present herein along with our surgical approach . in these 2 cases
, we were able to achieve successful decompression of the va ; the two patients recovered completely without further clinical symptoms .
a 50-year - old woman had been experiencing paroxysmal vertigo attacks for a 10 month period prior to visiting our institute .
the patient 's vertigo was aggravated when she turned her head to the left side .
scans , we observed no definitive abnormal findings except for hypoplastic left va in the neutral position ( fig .
2a ) , but complete occlusion of right va was found at atlanto - axial level when the patient turned her head to the left side ( fig .
we decided on a surgical decompression of the left va at the cross transverse foramen of the first cervix as the surgical approach .
we placed an adhesive , fibrous bandage between the left va and the transverse foramen . during the surgical procedure ,
after surgery , the patient 's symptoms improved , and her neck three - dimensional angiography ct scans demonstrated complete decompression of the right vertebral artery ( fig . 3 , 4 ) .
a 42-year old woman reported severe vertigo , dizziness , right upper extremity tingling sensations and aggravated syncope when she turned her head to the right . upon otolaryngological examination
, she presented right beating nystagmus when her head was rotated to the right in the sitting or supine position .
there were no abnormal findings except for hypoplasia of the posteroinferior cerebellar artery termination of the left va on magnetic resonance angiography .
however , dynamic cerebroangiography showed no steno - occlusive lesions of left va in the neutral position ( fig .
5a ) , but an occlusion of the left va was observed at the c1 - 2 level from right head rotation ( fig .
we selected a surgical approach and found an adhesion between the left va and transverse foramen .
a 50-year - old woman had been experiencing paroxysmal vertigo attacks for a 10 month period prior to visiting our institute .
the patient 's vertigo was aggravated when she turned her head to the left side .
scans , we observed no definitive abnormal findings except for hypoplastic left va in the neutral position ( fig .
2a ) , but complete occlusion of right va was found at atlanto - axial level when the patient turned her head to the left side ( fig .
we decided on a surgical decompression of the left va at the cross transverse foramen of the first cervix as the surgical approach .
we placed an adhesive , fibrous bandage between the left va and the transverse foramen . during the surgical procedure ,
after surgery , the patient 's symptoms improved , and her neck three - dimensional angiography ct scans demonstrated complete decompression of the right vertebral artery ( fig . 3 , 4 ) .
a 42-year old woman reported severe vertigo , dizziness , right upper extremity tingling sensations and aggravated syncope when she turned her head to the right . upon otolaryngological examination
, she presented right beating nystagmus when her head was rotated to the right in the sitting or supine position .
there were no abnormal findings except for hypoplasia of the posteroinferior cerebellar artery termination of the left va on magnetic resonance angiography .
no significant changes were observed with neck rotational positions . however , dynamic cerebroangiography showed no steno - occlusive lesions of left va in the neutral position ( fig .
5a ) , but an occlusion of the left va was observed at the c1 - 2 level from right head rotation ( fig .
we selected a surgical approach and found an adhesion between the left va and transverse foramen .
bhs is syndrome characterized by symptoms such as dizziness , vertigo , and blurred vision when the patient rotates his neck .
bhs is defined as symptomatic vertebrobasilar insufficiency by a mechanical occlusion of the vertebral artery during head rotation9 ) . however , because of the collateral blood flow through the contralateral va and the circle of willis , va occlusion does not cause symptoms in most individual cases11 ) . thus ,
symptomatic bhs is rare . because of its rarity , no large - scale established protocols exist for its research , treatment , or diagnosis .
the compressive occlusion of the va is occurs due to a variety of reasons , including the fibrous band tethering of the va at the transverse foramina of the c1-c2 junction , as in our cases , and at the point of dural penetration , which is located above the atlantooccipital membrane .
a pathognomonic finding of bhs is the improvement of symptoms when the patient is in a neutral position , even after he claims to have dizziness or blackout when he turns his head to one side .
when bhs is suspicious , considerable authors used digital subtraction angiography as the diagnostic modality1 ) . in our cases , clinical symptoms were aggravated when patients turned their head to one side ; symptoms were improved when the patients ' heads returned to a neutral position .
furthermore , we conducted dynamic angiography to confirm occlusive va lesions toward a diagnosis of bhs .
because of the rarity of this pathology , there are no long term follow - up studies ; only prospective studies exist for bhs treatment .
thus , there is no guideline to support the decision to proceed medically or operatively .
because of post - operative complications and the impact on quality of life , some authors have suggested medical treatment ( anticoagulation , neck collar applied not to rotate the head , etc.12 ) .
however , other patients with bhs who were treated conservatively with medication required surgery because of repeated , aggravated symptoms ; after surgery , these patients showed clinical improvement3 ) .
patients who had vascular decompression for bhs at the atlanto - axial level had shown signs of improvement in several case reports1,4,7,13 ) .
as mentioned above , there is no definitive guideline for the diagnosis and treatment of bhs because of its rarity .
the surgical decompression of mechanical va compressions constitutes an appropriate treatment with a good prognosis .
 bow hunter 's syndrome ( bhs ) is rare cause of vertebrobasilar insufficiency that arises from mechanical compression of the vertebral artery by head rotation . 
 there is no standardized diagnostic regimen or treatment of bhs . 
 recently , we experienced 2 cases resisted continues medication and treated by surgical approach . in both cases , there were no complications after surgery and there were improvements in clinical symptoms . 
 thus , we describe our cases with surgical decompression with a review of the relevant medical literature . 