Katsuno and colleaguesArticle point out that spinal and bulbar muscular atrophy (SBMA), or Kennedy disease, is an adult-onset lower motor neuron disease characterized by slowly progressive muscle weakness and atrophy. The disease is caused by the expansion of a trinucleotide CAG repeat encoding a polyglutamine tract within the first exon of the androgen receptor gene. They review the data related to several potential therapies, including hormonal manipulation, that have emerged from animal studies, some of which have been tested in clinical trials.
Zhang et alArticle determine whether patients with myasthenia gravis (MG) have serum antibodies to lipoprotein-related protein 4 (LRP4), a newly identified receptor for agrin that is essential for neuromuscular junction formation, and to whether it can be established that such antibodies contribute to MG pathogenesis. They report that anti-LRP4 antibodies were detected in the serum of approximately 9.2% of patients with double-seronegative MG. Editorial perspective is provided by David P. Richman, MDArticle.
Richman and colleaguesArticle determine the pathogenesis of anti–muscle-specific kinase (MuSK) myasthenia, a newly described severe form of myasthenia gravis associated with MuSK antibodies characterized by focal muscle weakness and wasting and absence of acetylcholine receptor antibodies, and whether antibodies to MuSK, a crucial protein in the formation of the neuromuscular junction (NMJ) during development, can induce disease in the mature NMJ. Their findings support the role of MuSK antibodies in the human disease, demonstrate the role of MuSK not only in the development of the NMJ but also in the maintenance of the mature synapse, and demonstrate involvement of this disease in both presynaptic and postsynaptic components of the NMJ.
Gibbons et alArticle investigate the relationship between orthostatic hypotension, antibody titers, and cognitive impairment in patients with autoimmune autonomic ganglionopathy. They show that reversible cognitive impairment is independently associated with both orthostatic hypotension and elevated nicotinic acetylcholine receptor autoantibodies, thereby expanding the clinical spectrum of autonomic ganglionopathy and, in so doing, providing an additional treatable cause of cognitive impairment.
Farrar and colleaguesArticle investigate whether cortical dysfunction or plasticity is a feature of spinal muscular atrophy (SMA). Their findings suggest that despite spinal motoneuron degeneration there remains preservation of corticomotoneuronal function in SMA. The greater corticomotoneuronal projections to surviving spinal motoneurons likely represent an adaptive response to spinal motoneuron degeneration in SMA.
Wang and colleaguesArticle examine the effects of premutation alleles on major brain fiber tracts in males. Diffusion tensor imaging was performed on all study participants. Their findings revealed widespread alterations in structural connectivity associated with fragile X–associated tremor/ataxia syndrome and preserved or subtle changes in structural connectivity in unaffected carriers.
Lax et alArticle explore myelin components and mitochondrial changes within the central nervous system in patients with well-characterized mitochondrial disorders due to nuclear DNA or mitochondrial DNA mutations. Their findings demonstrate that primary mitochondrial respiratory chain defects affecting the white matter, and unrelated to inflammation, are associated with myelin-associated glycoprotein loss and CNS demyelination.
Tezenas du Montcel and colleaguesArticle evaluate disease progression and determine validity of clinical tools for therapeutic trials. They note that disease progressed faster in SAC s with polyglutamine expansions in SCA1, 2, and 3 than the other groups. Both outcome measures are suitable for therapeutic trials.
Boxer et alArticle sought to determine the saccade abnormalities associated with autopsy-defined cases of frontotemporal lobar degeneration and of Alzheimer disease. They report that decreased visually guided saccade velocity and gain are suggestive of underlying tau pathology in frontotemporal dementia, with vertical saccade abnormalities most diagnostic of progressive supranuclear palsy.
Crompton et alArticle expand the phenotypic spectrum of familial adult myoclonic epilepsy (FAME), highlight diagnostic pointers to this underrecognized disorder, and refine the FAME2 genetic locus. A 6-generation FAME kindred of European descent was ascertained in New Zealand and Australia. The most common FAME phenotype in this large family is mild postural hand tremor resembling essential tremor, combined with subtle proximal myoclonus.
This Month in Archives of Neurology. Arch Neurol. 2012;69(4):427-428. doi:10.1001/archneurol.2011.1449