HAA are at definite risk for rupture (14%). Risk factors for rupture include multiple HAA and nonatherosclerotic origin. Patients with symptomatic aneurysms or any of these risk factors should be considered for intervention.

Splenic artery pseudoaneurysm is rare and usually is a complication of pancreatitis or trauma. Average aneurysm diameter in our series of 10 patients was smaller than previously reported (1.7 cm vs 5.0 cm). Although conservative management has produced excellent results in some reports, from our experience and the literature, we recommend repair of all splenic artery pseudoaneurysms.

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SMA aneurysms are rare but appear to have a higher risk of rupture than previously reported. Male patients and patients with noncalcified aneurysms appear to have a greater risk of rupture. beta-Blockade may have some protective effect against aneurysm rupture. Intervention is reasonable in all patients at good operative risk with SMA aneurysms, considering the high rupture rate in our series.

Fine-tuning of neuronal connections during development is regulated through environmental interactions. Some fine-tuning occurs through changes in gene expression and/or epigenetic gene-specific DNA methylation states. DNA methylation occurs by transfer of a methyl group from S-adenosyl methionine to cytosine residues in the dinucleotide sequence CpG. Although CpG sequences spread throughout the genome are usually heavily methylated, those occurring in CpG islands in the promoter regions of genes are less methylated. In most cases, the extent of DNA methylation correlates with the extent of gene inactivation. Other known epigenetic mechanisms include histone deacetylation and chromatin remodeling, RNA inhibition, RNA modification, and DNA rearrangement. Exposure memory expressed as epigenetic DNA modifications allows genomic plasticity and short-term adaptation of each generation to their environment. Environmental factors that affect DNA methylation include diet, proteins, drugs, and hormones. Induced methylation changes may produce altered gene response upon subsequent hormonal stimulation. The gene-specific DNA methylation state may be preserved upon transmission through mitosis and meiosis. An increasing amount of data implicates a role for DNA methylation in multi-factorial psychiatric disorders. For example, L-methionine treatment can exacerbate psychosis; while valproate, a drug producing hypomethylated DNA, reduces such symptoms. Hypermethylation of the promoter region of the RELN gene correlates with reduced gene expression. This gene's protein Reelin, which is necessary for neuronal migration and synaptogenesis, is reduced in schizophrenia and bipolar disorder, suggesting hypermethylation of the promoter region in these disorders. Some evidence implicates methylation of the promoter regions of the DRD2 and HTR2A genes in schizophrenia and mood disorders as well. DNA methylation usually increases with age, although hypomethylation of the promoter region of the amyloid A4 precursor gene during aging may play a role in Alzheimer's disease. More studies are needed to define the role of methylomics and other epigenetic phenomena in the nervous system.

MIM for visceral artery aneurysms can be used alone or in combination to effectively treat VAAs in elective or emergent conditions.

True arterial aneurysms of the upper extremity distal to the axillary artery are rare and most commonly caused by blunt trauma. Fifty-eight percent of these lesions present with symptoms or complications. Thirty-three percent of asymptomatic lesions later become symptomatic. These factors combined with the minimal morbidity associated with repair suggest that operative repair should be routinely performed for these aneurysms. Revascularization can be performed selectively.

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