BACKGROUNDSpinal muscular atrophy is an autosomal recessive neuromuscular disorder that is caused by an insufficient level of survival motor neuron (SMN) protein. Nusinersen is an antisense oligonucleotide drug that modifies pre-messenger RNA splicing of the SMN2 gene and thus promotes increased production of full-length SMN protein. METHODSWe conducted a randomized, double-blind, sham-controlled, phase 3 efficacy and safety trial of nusinersen in infants with spinal muscular atrophy. The primary end points were a motor-milestone response (defined according to results on the Hammersmith Infant Neurological Examination) and event-free survival (time to death or the use of permanent assisted ventilation). Secondary end points included overall survival and subgroup analyses of event-free survival according to disease duration at screening. Only the first primary end point was tested in a prespecified interim analysis. To control the overall type I error rate at 0.05, a hierarchical testing strategy was used for the second primary end point and the secondary end points in the final analysis. RESULTSIn the interim analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (21 of 51 infants [41%] vs. 0 of 27 [0%], P<0.001), and this result prompted early termination of the trial. In the final analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (37 of 73 infants [51%] vs. 0 of 37 [0%]), and the likelihood of event-free survival was higher in the nusinersen group than in the control group (hazard ratio for death or the use of permanent assisted ventilation, 0.53; P = 0.005). The likelihood of overall survival was higher in the nusinersen group than in the control group (hazard ratio for death, 0.37; P = 0.004), and infants with a shorter disease duration at screening were more likely than those with a longer disease duration to benefit from nusinersen. The incidence and severity of adverse events were similar in the two groups. CONCLUSIONSAmong infants with spinal muscular atrophy, those who received nusinersen were more likely to be alive and have improvements in motor function than those in the control group. Early treatment may be necessary to maximize the benefit of the drug. (Funded by Biogen and Ionis Pharmaceuticals; ENDEAR ClinicalTrials.gov number, NCT02193074.)

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Familial transthyretin (TTR) amyloidosis commonly presents with peripheral neuropathy and involvement of visceral organs. In contrast, signs of central nervous system (CNS) involvement are exceptional. We report that members of a kindred affected by a slowly progressive dementia, seizures, ataxia, hemiparesis, and decreased vision without neuropathy have TTR amyloid deposits in the leptomeninges, the brain parenchyma, and the eye. This condition, previously labeled oculoleptomeningeal amyloidosis, is linked to a mutation at codon 30 of TTR gene, resulting in the substitution of valine with glycine in this family, TTR amyloid deposits were present in the leptomeninges, especially the leptomeningeal vessels, and in the subependymal regions of the ventricular system where they disrupted the ependymal lining and resulted in amyloid-glial formations protruding into and narrowing the ventricular system. Hydrocephalus and atrophy and infarction of cerebral and cerebellar cortexes were also present. Review of the literature shows that amyloid deposition in the leptomeninges is not uncommon in TTR amyloidoses clinically characterized by peripheral neuropathy and lack of CNS signs. The present kindred, which presented exclusively with signs of CNS involvement, expands the phenotype of TTR amyloidosis and raises questions concerning the mechanisms determining phenotypic expression in TTR familial amyloidosis.

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Progressive subcortical gliosis (PSG) is a sporadic and familial dementing disease characterized pathologically by astrogliosis at the cortex-white matter junction, a feature present in some prion diseases. With immunocytochemical and Western blot analyses, we investigated the presence of deposits of the prion protein (PrP) and of the protease-resistant PrP isoform, the hallmarks of prion diseases, in six affected members of two large kindreds with PSG. The coding region of the PrP gene was sequenced and chromosomal linkage determined. We demonstrated "diffuse" PrP plaques in the cerebral cortex of two subjects from one kindred and protease-resistant PrP fragments in four of the five subjects examined. We found no mutation in the coding region of the PrP gene. Moreover, the disease was linked to chromosome 17 and not to chromosome 20, where the PrP gene resides. The familial form of PSG is the first human genetic disease characterized by the presence of protease-resistant PrP that lacks a mutation in the coding region of the PrP gene. The linkage to chromosome 17 suggests that other genes are involved in the PrP metabolism. Whether the protease-resistant PrP plays a primary or secondary role in the pathogenesis of this form of PSG remains to be determined.