The outer arterial wall layers are primarily affected in spontaneous cervical artery dissection.

OBJECTIVE: To evaluate the macroscopic and microscopic phenotype of the distal superficial temporal artery (STA) in patients with spontaneous cervical artery dissection (sCAD, n = 14). Arteries of accident victims, free of clinically apparent vascular disease, served as reference samples (n = 9). METHODS: Specimens of distal STA branches were obtained by biopsy or at autopsy. Their fine and ultrafine structure was documented by close-up photography of native STA branches, light microscopy, and electron microscopy in a case-control study. RESULTS: STA specimens from patients with sCAD revealed pathologic changes mainly in the adventitial and medial layers. In these areas, vacuolar degeneration and fissuring were associated with neoangiogenesis of capillaries and microscopic erythrocyte extravasation into the connective tissue. In addition, some specimens showed overt microhematomas close to the medial/adventitial border visible at low magnification. The reference arteries showed virtually no pathologic changes in the outer arterial layers. CONCLUSION: Bearing in mind that the STA is only a surrogate for the cervical arteries affected by sCAD, we propose the following pathogenetic model. We hypothesize that sCAD affects primarily the outer arterial layers. The process starts with degenerative changes at the medial-adventitial border associated with neoangiogenesis of capillary vessels branching from vasa vasorum in the adventitia. Leakage of neoangiogenetic capillaries releases blood cells into the connective tissue and leads to formation of microhematomas along the medial/adventitial border, as well as disintegration of the medial and adventitial texture. Microhematomas might then cause successive rupture of multiple neoangiogenetic capillaries and vasa vasorum, ultimately resulting in dissection.

Morphometric analysis of collagen fibrils in skin of patients with spontaneous cervical artery dissection.

BACKGROUND AND AIM: The aetiopathogenesis of spontaneous cervical artery dissection (sCAD) is largely unknown. Electron microscopic (EM) examination of skin biopsies of patients with sCAD revealed very subtle pathological changes of dermal connective tissue in about half of these patients leading to the hypothesis of an underlying connective tissue disorder. However, connective tissue abnormalities did not allow clear discrimination between patients and controls in our hands. Therefore, we sought to establish an objective basis for the assessment of connective tissue abnormalities in patients with sCAD using standardised morphometric assessment of collagen fibrils. METHODS: In this study a blinded examination was performed of collagen in skin biopsies and it sought parameters which are able to discriminate between patients with sCAD and controls. Various morphometric parameters were compared between patients with sCAD (n = 20) and control subjects (n = 18). RESULTS: Previously described "flower-like" collagen fibrils in skin biopsies were extremely rare in patients and controls and did not discriminate between the groups. However, they were abundant in the skin biopsy of a patient with Ehlers-Danlos syndrome type III (EDSIII) used as a reference. Morphometric parameters such as collagen fibril diameter, fibril density and relative fibril area did not discriminate between patients and controls on an individual basis, but the mean diameter of collagen fibrils in the skin was lower in patients with sCAD compared with controls while fibril density was higher resulting in nearly equal fibril areas per unit of area (relative fibril area) comparing both groups as well as individuals. CONCLUSIONS: Blinded pathological and morphometric analysis of collagen fibres in skin biopsies was, in our hands, unable to discriminate reliably between patients with sCAD and controls on an individual basis but did show differences in collagen fibril morphometry on a group basis. Furthermore, systematic and blinded pathological studies of skin biopsies in patients with sCAD and controls are needed.

A distinctive case of fibromuscular dysplasia.

Fibromuscular dysplasia (FMD) is a rare, non-inflammatory angiopathy, which can affect the brain supplying arteries. Usually, the diagnosis is based on conventional and/or MR angiography. We present a patient with multisegmental stenoses of the internal carotid artery (ICA) where the diagnosis of FMD is based on an eye-catching ultrasound finding.

Generalized arteriopathy in patients with cervical artery dissection.

OBJECTIVE: To make an ultrastructural comparison of superficial temporal artery (STA) biopsy specimens from patients with spontaneous cervical artery dissection (sCAD) and controls. METHODS: The authors used light microscopic examination of semithin sections and electron microscopic examination of ultrathin sections of STA biopsy specimens from patients with sCAD and controls. RESULTS: STA biopsy specimens from patients with sCAD taken around the time of the dissection showed a zone of connective tissue weakening with fissuring at the junction between the tunica media (TM) and the tunica adventitia (TA) in seven of nine specimens and erythrocyte infiltration in eight of nine specimens but in none of the control specimens. Light microscopy demonstrated transparent circular spots that, on electron microscopy, turned out to represent erythrocytes and other cellular components at different stages of degradation. Occasionally, scattered immune cells were found in specimens from patients with sCAD. In addition, smooth muscle cells of the synthetic phenotype, some of them showing extensive vacuolation were more common in the TM of STA biopsy specimens from patients with sCAD than in control specimens. CONCLUSIONS: Signs of tissue weakening along the TM/TA junction in STA biopsy specimens of patients with sCAD but not in controls suggest the presence of a generalized arteriopathy leading to impairment of the stability of the arterial wall in patients with sCAD. Limiting factors of the study are that some control biopsies were obtained from autopsies and that the anticoagulation status of patients and controls were not completely comparable.

Protease inhibitors in spontaneous cervical artery dissections.

BACKGROUND AND PURPOSE: Observations in patients with arterial aneurysms, fibromuscular dysplasia, and spontaneous cervical artery dissection (sCAD) indicate that protease inhibitor deficiency might boost the enzymatic destruction of arterial tissue and increase the risk of these arterial wall diseases. Here we present the first large investigation of the protease inhibitor hypothesis in patients with sCAD. METHODS: Eighty patients with sCAD were compared with 80 age- and sex-matched healthy individuals. Alpha1-antitrypsin (alpha1-AT) and alpha2-macroglobulin (alpha2-MG) levels, and alpha1-AT genotypes were assessed and compared between groups. RESULTS: alpha1-AT and alpha2-MG levels as well as alpha1-AT genotypes did not differ significantly between patients and controls. The frequency of Z alleles in the patient group was higher than in the control group and than in other cohorts from Europe; however, the difference remained nonsignificant. All patients with Z alleles had internal carotid artery dissections. CONCLUSIONS: Overall, this data does not support the hypothesis that protease inhibitor levels or alpha1-AT genotypes play an important role in the etiology of sCAD. The present data does not exclude that the Pi-Z allele might have an influence on subgroups of sCAD, such as internal carotid artery dissections.

A sequence-ready BAC/PAC contig and partial transcript map of approximately 1.5 Mb in human chromosome 17q25 comprising multiple disease genes.

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant recurrent neuropathy mapped to a 4-cM interval on chromosome 17q25 between the short tandem repeat (STR) markers D17S1603 and D17S802. Chromosome 17q25 in general and the 4-cM HNA region in particular are also implicated in the pathogenesis of a number of tumors (tylosis with esophageal cancer, sporadic breast and ovarian tumors) and harbor a psoriasis susceptibility locus. Initial attempts to construct a yeast artificial chromosome contig failed. Therefore, we have now constructed a complete P1 artificial chromosome (PAC) and bacterial artificial chromosome (BAC) contig of the region flanked by the STR markers D17S1603 and D17S802. The contig contains 22 PAC and 64 BAC clones and covers a physical distance of approximately 1. 5 Mb. A total of 83 sequence-tagged site (STS) markers (10 known STSs and STRs, 56 STSs generated from clone end-fragments, 12 expressed sequence tags, and 5 known genes) were mapped on the contig, resulting in an extremely dense physical map with approximately 1 STS per 20 kb. This sequence-ready PAC and BAC contig will be pivotal for the positional cloning of the HNA gene as well as other disease genes mapping to this region.

High-signal lesions in the midbrain on T1-weighted MRI in an HIV-infected patient.

In addition to opportunistic infections, neoplasms or cerebrovascular complications, metabolic encephalopathies are a classical cause of diffuse brain dysfunction in HIV infection and are frequent in the terminal stage. We report an HIV-infected patient with symmetrical, focally increased signal in the midbrain on proton density-and T1-weighted MRI without corresponding high signal on T2-weighted images or on CT. While the precise nature and cause of this uncommon finding is not fully understood, the available evidence suggests that these lesions might represent a novel metabolic encephalopathy.

Expression of the RT6 mono(ADP-ribosyl)transferases is regulated by two promoter regions.

The structure of the RT6 mono(ADP-ribosyl)transferase gene was studied. Analysis of cDNA clones revealed eight exons and suggested two independent transcriptional start sites. The existence of the downstream initiation site was confirmed by S1-nuclease protection and localized to position +29 of exon 2. The corresponding 5' flanking regions were found to contain typical promoter structures such as TATA- and CCAAT-boxes. Comparison with sequences deposited in the TRANSFAC database of transcription factor binding sites revealed few putative regulatory elements in the region associated with exon 1 (promoter 1). In contrast, several elements contained in the regulatory regions of other T cell-specific genes, such as ets, lyf-1 and ikaros were found in in promoter 2. Analysis of RT6-transcripts showed this region to be the most active promoter in spleen cells of adult rats. Finally, transient transfection assays with reporter gene constructs showed promoter 2 to mediate T-cell specific transcription.

Structure of the gene encoding the rat T cell ecto-ADP-ribosyltransferase RT6.

Cellular functions, such as the cytolytic potential of CTLs, can be regulated by mono-ADP-ribosylation of target proteins. Recently, the T cell differentiation marker RT6 has been shown to possess mono-ADP-ribosyltransferase activity. Defects in RT6 expression coincide with increased susceptibility in animal models for insulin-dependent diabetes mellitus and other autoimmune diseases. We present an analysis of the rat RT6 gene, providing a basis for studying the regulation of this gene in T cells of normal and diabetes-prone rats. It is the first structural analysis of a mammalian mono-ADP-ribosyltransferase gene. The RT6 gene consists of eight exons spanning approximately 20 kb. The proximal four exons encode 5' untranslated region sequences and are found in multiple alternatively spliced variants. Exon 5 encodes the N-terminal signal sequence. An unusually large exon 7 encodes the entire native polypeptide. The final exon 8 encodes the C-terminal signal sequence for glycosylphosphatidylinositol anchor attachment and the 3' untranslated region. Two independent TATA box-containing promoters associated with exons 1 and 2 were identified, and their activity was verified in transient transfection assays. The distal promoter displays elements contained in the regulatory regions of T cell-specific genes, such as ets and ikaros. Analysis of RT6 transcripts showed that this promoter is the major one in adult rat spleen cells. The 3' end of the gene does not display alternative splicing. However, two polyadenylation signals are found in the 3' untranslated region.