Use of histomorphometry in the assessment of fatal vertebral artery dissection

Plausible Mechanisms of Causation of Immediate Stroke by Cervical Spine Manipulation: A Narrative Review

It has been proposed that cervical spine manipulation (CSM) can cause dissection in healthy cervical arteries, with resultant immediate stroke. However, research does not support a causal association between CSM and cervical artery dissection (CAD) in healthy cervical arteries. The objective of this study was to review the literature to identify plausible mechanisms of causation of immediate stroke by CSM. Immediate stroke is defined as a stroke occurring within seconds or minutes of CSM. Our review found plausible thromboembolic and thrombotic mechanisms of causation of immediate stroke by CSM in the literature. The common premise of these mechanisms is CAD being present before CSM, not occurring as a result of CSM. These mechanisms of causation have clinical and medicolegal implications for physicians performing CSM.

Symptoms of Patients With Vertebral Artery Dissection Presenting to Chiropractors: A Systematic Review and Meta-Analysis

Early symptoms of vertebral artery dissection (VAD) may be nonspecific, including neck pain and headache. Neck pain and headache are also common reasons for patients to seek chiropractic care. We hypothesized that neck pain and/or headache would be the most prevalent symptoms among patients with undiagnosed VAD presenting to chiropractors compared to dizziness or other symptoms. We searched PubMed, Ovid, the Index to Chiropractic Literature, Google Scholar, and gray literature through September 2023 for observational studies describing patients aged ≥10 with previously undiagnosed VAD presenting to a chiropractor. Article selection, data extraction, and quality assessment were performed in duplicate. We synthesized the point prevalence of symptoms and other clinical features. We included 10 case reports describing 10 patients (mean age = 37, SD = 7, 60% female). All patients had either neck pain or headache (100%; 95% confidence interval (CI) = 100%-100%). The most prevalent individual symptoms were neck pain (90%; 95% CI = 71%-100%), headache (80%; 95% CI = 55%-100%), visual disturbance (50%; 95% CI = 19%-81%), and dizziness (40%; 95% CI = 10%-70%). The certainty of results was very low due to publication bias. While our findings suggest that neck pain and/or headache are the most prevalent symptoms among patients with undiagnosed VAD visiting a chiropractor, the small sample size and reliance on case reports preclude any definitive conclusions. Further research with larger sample sizes, control groups, and better control of confounders is required to corroborate these results. Chiropractors should be aware of VAD features and refer suspected patients for emergency care.

Vertebral artery dissection presenting as acute cerebrovascular accident

Vertebral artery dissection is a lesser known but significant cause of stroke in young, healthy people. Given its infrequency of presentation, emergency physicians may not always recognize its common symptoms--vertigo, diplopia, ataxia, and dysarthria--as a stroke. In this case report, we describe a patient with vertebral artery dissection presenting with atypical symptoms and discuss the epidemiology, risk factors, presentation, clinical examination findings, imaging modalities, and treatment of this disease.

Medico-legal Aspects of Traumatic Injury of the Vertebrobasilar Artery

Based on our experiences with medico-legal autopsies, we analyzed traumatic injury of the vertebrobasilar artery (VBA) in traffic accident victims. VBA rupture occurred in six cases with traumatic medullary lesions, but in none with cervical cord injury. A relatively small external force applied to the head or neck can induce isolated traumatic subarachnoid hemorrhage (SAH), which accounts for approximately 11% of fatal head injuries. We examined the relationship between site of impact and site of vascular injury in 16 cases of isolated traumatic SAH. The results showed that the vertebral artery (VA) on the side of impact tended to be longitudinally injured in victims experiencing an external force equivalent to that of a fist punch to the head or face. There was no clear relationship between the site of impact and the site of vascular injury in victims who had sustained an external force greater than that of a fist punch. However, our results suggest that an external force causing rotation of the head was likely to cause tearing of the artery. In cases in which an external force equivalent to that of a fist punch was applied to the head, a raised blood alcohol level was a significant risk factor for artery rupture. Furthermore, a difference in the diameters of the left and right VAs was a risk factor for artery rupture. To determine why the VA, the most frequent site of arterial dissection, is also frequently the site of injury, we histologically examined normal and dissected VBAs. We also discuss medico-legal issues of the causal relationship between external force applied and rupture or dissection of the VA.

Histological Study of the Normal Vertebral Artery-Etiology of Dissecting Aneurysms-

Histological evaluation of dissecting aneurysms of the cerebral arteries has suggested that defects in the internal elastic lamina (IEL) induce dissection of the arterial wall. Dissecting aneurysms occur most frequently in the vertebral artery (VA). The present study examined sections of the normal VA to elucidate the mechanisms of arterial dissection. Bilateral VAs (20 vessels) were obtained from 10 patients who died of causes other than intracranial lesions. The VAs were detached from the VA union to the site 10 mm proximal from the point penetrating the dura mater. The VAs were cut at 5-mm intervals, and each segment was observed using modified Masson's trichrome staining for elastic fibers. The thickness of the media and adventitia significantly thinned after the origin of the posterior inferior cerebellar artery (PICA). IEL defects were observed at 35 sites in 11 vessels from six subjects. There was a high incidence of IEL defects in the extradural portion and near the origin of the PICA, areas frequently involved in arterial dissection. There was a high incidence of intimal thinning at areas of IEL defects (19 of 35), and thinning was particularly marked distal to the origin of the PICA. In the absence of intimal thickening, the vascular strength at the site of IEL defects may be reduced, which would promote the occurrence and progression of arterial dissection.

Age related changes in the tunica media of the vertebral artery: implications for the assessment of vessels injured by trauma

AIMS

To provide an illustrated, detailed semiquantitative analysis of the important degenerative changes along the length of the vertebral artery so that pathologists faced with investigating a fatal arterial injury can identify important pre-existing wall abnormalities.

METHODS

Ten transverse annuli were taken along 34 vertebral arteries from 17 subjects and stained sections were prepared using haematoxylin and eosin and the picro-sirius red method. After routine microscopy, the elastic fibres, collagen, and smooth muscle nuclei in the tunica media were quantified using an eyepiece graticule. An estimate of the severity and extent of elastic tissue fragmentation, collagenous scarring, and intimal thickening/atheroma was then undertaken.

RESULTS

Smooth muscle counts remained constant along the artery but collagen counts were higher and elastic counts substantially lower within the intracranial segment. Elastic fibre fragmentation was recognised in infancy and was moderately advanced by early adulthood but considerable collagenous scarring developed later in life. Some individuals demonstrated severe fragmentation and scarring before the age of 35 years. The degenerative changes were often focal and spared the intracranial segment almost completely. Atheroma increased with age but was rarely severe and appeared not to worsen appreciably beyond the age of 40 years. An unusual arrangement of the collagenous tissue was described within the upper cervical loops.

CONCLUSION

Damaged vertebral arteries need to be sampled extensively to allow a proper histological assessment. The picro-sirius red method was successful in delineating the fine connective tissue structure of the wall and early degenerative changes. An understanding of the age and site specific changes should allow the pathologist to recognise important pre-existing abnormalities more easily.

Vertebral artery trauma

Vertebral artery trauma is not commonly seen by forensic pathologists. The experience of vertebral artery trauma at the Victorian Institute of Forensic Medicine (30 cases) is summarized and reviewed in the light of the literature. Causes of vertebral artery trauma are discussed. In case 1, the history and timing of the injury raise the question as to whether the vertebral artery dissection occurred before the episode of trauma, that is, was spontaneous or resulted from trauma. Moreover, underlying vertebral artery disease was present, raising the question as to how much trauma was needed to cause vertebral artery dissection. In case 2, despite the history of head/neck trauma, a neurosurgeon considered the subarachnoid hemorrhage was spontaneous, due most likely to ruptured saccular aneurysm or arteriovenous malformation. In case 3, the vertebral artery rupture was not diagnosed in the setting of multiple injuries. Case 4 is an example of prolonged survival with delayed onset of symptoms following vertebral artery trauma. Case 5 is an example of the not uncommon scenario of homicidal vertebral artery trauma accounting for basal subarachnoid hemorrhage, rapid collapse and death. Cases 1 and 4 indicate that relatively normal activity may be possible following vertebral artery trauma in some cases (at least for a time). Cases 1 and 4 are also examples of intracranial vertebral artery dissection.

Traumatic laceration of the intracranial vertebral artery causing fatal subarachnoid hemorrhage: case report

A 36-year-old man who had been drinking alcohol had a fatal subarachnoid hemorrhage immediately after suffering a moderate craniofacial injury. Autopsy revealed a 3-mm longitudinal laceration of the left intracranial vertebral artery proximal to the posterior inferior cerebellar artery. There was no finding of arterial dissection. We discuss the mechanisms of the traumatic laceration of the vertebral artery in relation to traumatic dissection of the vertebral artery.

A necropsy and histomorphometric study of abnormalities in the course of the vertebral artery associated with ossified stylohyoid ligaments

AIMS

To establish whether abnormalities in the course of the vertebral artery occur and whether they are relevant to arterial injury associated with head and neck movements.

METHODS

Twenty vertebral arteries were carefully dissected at necropsy and abnormalities in course were noted, along with any other bony or cartilaginous cervical anomalies. The effect of head and neck movement on these vessels was studied before a detailed histomorphometric examination was undertaken on sections of the excised arteries.

RESULTS

Five vessels had an abnormal course. One vessel entered the transverse foramina of the fifth cervical vertebra rather than the sixth, but was otherwise normal. In two subjects both vertebral arteries were abnormal in the upper cervical portion with, in each case, a straight left vertebral artery and a right vertebral artery with a deficient loop, closely applied to the atlanto-axial joint. Both of these subjects also had completely ossified stylohyoid ligaments and the arteries visibly stretched with modest head and neck movements. Histology revealed variable degrees of smooth muscle disarray in the tunica media of two of the arteries with loop deficiencies. The circumference of one of the straight arteries was smaller than expected but in all other measured histomorphometric parameters these vessels appeared normal.

CONCLUSIONS

Vertebral artery loops are deficient in a number of subjects. This finding is important given the recently described biomechanical susceptibility of the vertebral artery to longitudinal extension and may explain the smooth muscle changes, in that this may represent attempts at arterial wall remodelling. Subjects with such loop deficiencies may be more susceptible to a variety of head and neck insults and such abnormalities should be sought at necropsy in subjects who die as a result of fatal vertebral artery injury.