The vertebral artery supplies blood flow to the hindbrain and courses through the transverse foramina of the cervical levels from C6 to C1 and is tethered at foramina C2, C1 and the atlanto-occipital membrane.
Abnomal stress on this artery may lead to a reduction of blood flow to the hindbrain, which we call vertebrobasilar insufficiency – a condition that can develop into cerebral or brain stem ischemia and lead to severe morbidity or death.
Estimations of the incidence of a VBI vary between one incidence in 5 million therapy sessions to one incidence in 400.000 cervical manipulations to 1 cerebrovascular accident in 100.000 patients aged of 45 or younger according to Rivet et al. (2005).
The debate if cervical manipulation can lead to a dissection of the vertebrobasilar artery is ongoing although literature has failed to provide a clear link between the two.
The classical ischemic signs characteristic for VBI include the 5Ds: dizziness, diplopia (or in other words double-vision), dysphagia (= which is a difficulty in swallowing), dysarthria (which means problems with the muscles that produce speech) and drop attacks. Futhermore, they include the 3Ns, which are nausea, nystagmus (which is a condition of involuntary eye movement) and ipsilateral numbness in the face as well as 1A, which is ataxia which describes lack of voluntary coordination of muscle movements which include gait abnormalities.
Taylor et al. (2010) mention that these signs rarely present in isolation in case of a VBI.
Most of the time, these ischemic signs a preceded by non-ischemic signs which are ipsilateral posterior neck pain and/or occipital headache and C5/C6 cervical nerve root impairment in rare cases due to lack of blood supply. Oftentimes, the headache is described as “headache like no other” and severe in nature.
As those symptoms are very common in our general neck pain and headache population, it is very important to look for risk factors which could indicate a lesion of the vertebrobasilar artery. These can be divided into 1) mechanical forces and 2) risk factors indicating an underlying pathology like atherosclerosis.
Mechanical risk factors include a preceding trauma to the head like in extreme neck movement during whiplash, sport, cervical manipulations etc., but also include onset of symptoms after innocuous day to day movements like visiting the hair dresser or turning to reverse the care. Another mechanical risk factor can be upper cervical instability. You can watch a video about that by a click in the top right corner!
Risk factors for underlying pathology include hypertension, hypercholesterolemia, hyperlipidemia, hyperhomocysteinemia, diabetes, genetic clotting diseases, infections, smoking, free radicals, direct vessel trauma or iatrogenic causes like surgery or medical interventions.