Motor Vehicle Accidents: The Most Common Cause of Traumatic Vertebrobasilar Ischemia

Canadian Journal of Neurological Sciences November 2003; Volume 30, No. 4; pp. 320-325 Michel Beaudry, J. David Spence From the Department of Clinical Neurological Sciences, University of WesternOntario, London, Canada. FROM ABSTRACT: Background: Recent media exposure of strokes from chiropractic manipulation have focusedattention on traumatic vertebrobasilar ischemia. However, chiropracticmanipulation, while the easiest cause to recognize, is probably not the mostcommon cause of this condition. Methods: We reviewed all consecutive cases of traumatic vertebrobasilar ischemia referred toa single neurovascular practice over 20 years. Results: There were 80 patients whose vertebrobasilar ischemia was attributed to necktrauma. Five were diagnosed as due to chiropractic manipulation, but thecommonest attributed cause was motor vehicle accidents (MVAs), which accountedfor 70 cases; one was a sports injury, and five were industrial accidents.In some cases neck pain from an MVA led to chiropractic manipulation, so the causemay have been compounded.In most vehicular cases the diagnosis had been missed, even denied, by theneurologists and neurosurgeons initially involved.The longest delay between the injury and the onset of delayed symptoms was fiveyears. Conclusions: Traumatic vertebrobasilar ischemia is most often due to MVAs; the diagnosis isoften missed, in part because of the delay between injury and onset of symptomsand, in part, we hypothesize, because of reluctance of doctors to be involved inmedicolegal cases. SIGNIFICANT POINTS FROM THIS ARTICLE: 1) Recent neck trauma may cause extracranial carotid and vertebral dissection. 2) Genetic abnormalities of collagen, elastin and other supporting elements inthe blood vessel wall may predispose the patient to carotid and vertebral arterydissection with even minor trauma such as sneezing or Valsalva maneuvers. 3) When symptoms are delayed after trauma, the connection between traumaand vascular events are difficult to recognize. The longest described (in theliterature) delay between trauma and onset of vertebrobasilar symptoms is twomonths. 4) Delays of 7 weeks after injury and 37 days after a motor vehicle accident(MVA) have been reported for the vertebrobasilar distribution, and delay of manyyears has been described in the carotid artery distribution." 5) When vertigo is experienced following vertebral artery dissection, it is oftendifficult for the attending physician to think of cerebral vascular problem as opposedto a vestibular problem, particularly in a young patient. 6) Migraine can produce visual symptoms indistinguishable from those due totransient ischemia in the posterior cerebral artery territory, and migraine can alsobe triggered by trauma. 7) In this study, all of these were attributed to vertebrobasilar ischemia:70% showed loss of consciousness64% had some difficulty with short-term memory or episodes of transient global amnesia2.5% had sleep disturbances (narcolepsy, sleep-walking) 8) Several patients had a motor vehicle accident, and then had further vascularinjury by neck manipulation. [This suggests that absent the initial MVA, thechiropractic manipulation would not have been associated with the ischemia]. 9) The severity of the initial trauma was substantial for some patients, but wasmild for many. 10) We have been struck by how often neurologists and neurosurgeons miss orrefuse to recognize the diagnosis, and suspect that it is often dismissed because ofan aversion to medicolegal cases and legal practitioners. The unwillingness todiagnose this condition of traumatic vertebrobasilar ischemia in the setting of MVAsis in marked contrast to the willingness, even eagerness, to diagnose it in thesetting of chiropractic manipulation, often by the same physicians who are unwillingto recognize it in MVA cases. 11) The cases of sleep disturbance noted (sleepwalking and narcolepsy) wereattributed to ischemia of the brainstem reticular formation. 12) The diagnosis is often missed, in many cases because the neck injury is aminor event such as a chiropractic manipulation. 13) Another reason for failure to consider the association between the neck injuryand the subsequent vertebrobasilar ischemia is the delay in time, up to nearly fiveyears. 14) With extension of the neck, especially when adding a rotational component,the vertebral artery is stretched and/or compressed in the foramen transversariumof the atlas or before it pierces the atlanto-occipital ligament. 15) Trivial neck turning while looking backward while backing up a car or duringswimming, yoga or archery, or a Valsalsva maneuver during birthing, may initiatevertebral artery dissection. 16) Neck extension during surgical intubation has been shown to injure thevertebral artery. 17) Vertebrobasilar ischemia may occur after extension of the neck over the edgeof a hairdressers sink while having hair shampooed. 18) 72% of people have an asymmetric circulation, usually having one hypoplasticvertebral artery. 19) Rotation and extension of the neck obstructs flow in a dominant vertebralartery, which may predispose the patient to problems when the collateral circulationis poor. 20) Rarely, osteophytes may compress a vertebral artery causing recurrenttransient ischemic attack events. 21) Instability of the alar or other atlanto-axial ligaments may cause episodes ofvertebrobasilar ischemia provoked by turning of the head. 22) Arterial spasm may lead to ischemic symptoms, and pre-traumatic spasmincreases the incidence of dissection. 23) Migraine may cause ischemia symptoms similar or identical to arterydissection. 24) Artery dissections are best shown with either MRA (magnetic resonanceangiogram) or ultrasound. 25) Traumatic vertebrobasilar ischemia may present up to four and nearly fiveyears after the neck injury. It is, therefore, probably much more common than iscurrently suspected. 26) Though chiropractic manipulation is perhaps the best-known cause, it isimportant to recognize that MVAs are a much more common cause, which is oftenmissed. COMMENTS FROM DAN MURPHY * All chiropractors should be aware that motor vehicle collisions are a prime(and possibly the primary), trigger of vertebral artery dissections. * The symptoms of post-traumatic vertebral artery dissections can be delayedfor hours, days, weeks, months and even years. * The primary mechanism for vertebral artery dissection is a combination ofcervical extension and rotation. * There appears to be an increased risk of dissections in patients withmigraines.