Pathomorphological differentiation between traumatic rupture and nontraumatic arterial dissection of the intracranial vertebral artery

We aimed to establish an objective indicator for differential diagnosis between traumatic rupture of the intracranial vertebral artery (TRIVA) and nontraumatic rupture from intracranial vertebral artery dissection (NIVAD). We investigated 19 intracranial vertebral artery (IVA) samples, including three from TRIVA, seven from NIVAD and nine non-IVA rupture cases using 0.2-mm serial histological sections through the IVA. The internal elastic lamina (IEL)–adventitia ratio for each slide was calculated as the ratio of the traced length of the adventitia to the length of the IEL as measured by digital photomicrography. NIVAD cases showed a significant peak in the IEL–adventitia ratio around the area of rupture, whereas TRIVA and non-rupture cases showed no specific increase or decrease in IEL–adventitia ratios throughout the IVAs. All NIVAD cases had a significantly higher average IEL–adventitia ratio across 10 slides at the site of the rupture lesion than at the site furthest from the rupture. In contrast, two out of three TRIVA cases showed no significant difference between the two points. The other TRIVA case showed a significantly lower IEL–adventitia ratio at the point nearest the rupture compared with that at the point farthest from the rupture. Other histological characteristics considered specific to either TRIVA or NIVAD were observed. Our results indicate that measuring and comparing IEL–adventitia ratios at ruptured and non-ruptured sites of the IVA could be a useful practical indicator for differential diagnosis between TRIVAs and NIVADs.