Two other herpes viruses (Epstein–Barr virus/HHV-4 and varicella zoster virus/HHV-3) and the bacterium Mycoplasma pneumoniae have been associated with GBS. GBS is known to occur after influenza, and influenza vaccination has been demonstrated to be associated with a reduced risk. The tropical flaviviral infections dengue fever and Zika virus have also been associated with episodes of GBS. Previous hepatitis E virus infection has been found to be more common in people with GBS. Vaccine onset
An increased incidence of Guillain–Barré syndrome followed influenza immunization that followed the 1976 swine flu outbreak (H1N1 A/NJ/76); 8.8 cases per million (0.0088 per 1000) recipients developed it as a complication. GBS cases occurred in 362 patients during the 6 weeks after influenza vaccination of 45 million persons, an 8.8-fold increase over normal rates. The 1976 swine flu vaccination-induced GBS was an outlier; small increases in incidence have been observed in subsequent vaccination campaigns, but not to the same extent. The 2009 flu pandemic vaccine against pandemic swine flu virus H1N1/PDM09 did not cause a significant increase in cases. In fact, "studies found a small increase of approximately 1 case per million vaccines above the baseline rate, which is similar to that observed after administration of seasonal influenza vaccines over the past several years." The benefits to the population as a whole of vaccination in preventing influenza outweigh the small risks to individuals of that group of GBS after vaccination.
Recurrent silent strokes, with or without clinical strokes, often lead to cognitive decline and overt subcortical dementia. A case of CADASIL presenting as schizophreniform organic psychosis has been reported. Pathophysiology
The underlying pathology of CADASIL is progressive hypertrophy of the smooth muscle cells in blood vessels. Autosomal dominant mutations in the Notch 3 gene (on the long arm of chromosome 19) cause an abnormal accumulation of Notch 3 at the cytoplasmic membrane of vascular smooth muscle cells both in cerebral and extracerebral vessels, seen as granular osmiophilic deposits on electron microscopy. Leukoencephalopathy follows. Depending on the nature and position of each mutation, a consensus significant loss of betasheet structure of the Notch3 protein has been predicted using in silico analysis. Diagnosis
MRIs show hypointensities on T1-weighted images and hyperintensities on T2-weighted images, usually multiple confluent white matter lesions of various sizes, are characteristic. These lesions are concentrated around the basal ganglia, peri-ventricular white matter, and the pons, and are similar to those seen in Binswanger disease. These white matter lesions are also seen in asymptomatic individuals with the mutated gene. While MRI is not used to diagnose CADASIL, it can show the progression of white matter changes even decades before onset of symptoms.The definitive test is sequencing the whole Notch 3 gene, which can be done from a sample of blood. However, as this is quite expensive and CADASIL is a systemic arteriopathy, evidence of the mutation can be found in small and medium-size arteries. Therefore, skin biopsies are often used for the diagnosis.