Clinical Characteristics and Possible Drug Targets in Autosomal Dominant Spinocerebellar Ataxias

Genetic ataxias: update on classification and diagnostic approaches

Ataxia encompasses a large group of rare disorders characterized by irregular movements, decreased coordination, imbalance, kinetic tremor, wide-based stance, and dysarthria. Evaluating ataxia can be challenging considering the volume of disorders and their complex pathologies involving diverse genetic and clinical factors. This is a comprehensive review of the genetic ataxia literature, presenting updated guidelines for differential diagnosis. Age, time course, and family history provide initial guidance for evaluation of ataxia. As genetic testing is increasingly utilized, new genes are discovered and phenotypes for existing disorders are expanded. This review assists physicians by offering a diagnostic roadmap for suspected hereditary ataxia based on the current literature.

Spinocerebellar ataxia type 40: A case report and literature review

Spinocerebellar ataxias (SCAs) are a group of neurodegenerative diseases with ataxia as the main clinical manifestation. The phenotypes, gene mutations, and involved sites of different subtypes show a high degree of heterogeneity. The incidence of SCA varies greatly among different subtypes and the case of SCA40 is extremely rare. The aim of this study is to report a rare case of SCA40 and systematically review the incidence, gene mutation, and phenotype of SCAs, especially SCA40.

Ophthalmic Manifestations and Genetics of the Polyglutamine Autosomal Dominant Spinocerebellar Ataxias: A Review

Spinocerebellar ataxia (SCA) is a part of the cerebellar neurodegenerative disease group that is diverse in genetics and phenotypes. It usually shows autosomal dominant inheritance. SCAs, always together with the cerebellar degeneration, may exhibit clinical deficits in brainstem or eye, especially retina or optic nerve. Interestingly, autosomal dominant SCAs share a common genetic mechanism; the length of the glutamine chain is abnormally expanded due to the increase in the cytosine–adenine–guanine (CAG) repeats of the disease causing gene. Studies have suggested that the mutant ataxin induces alteration of protein conformation and abnormal aggregation resulting in nuclear inclusions, and causes cellular loss of photoreceptors through a toxic effect. As a result, these pathologic changes induce a downregulation of genes involved in the phototransduction, development, and differentiation of photoreceptors such as CRX, one of the photoreceptor transcription factors. However, the exact mechanism of neuronal degeneration by mutant ataxin restricted to only certain type of neuronal cell including cerebellar Purkinje neurons and photoreceptor is still unclear. The most common SCAs are types 1, 2, 3, 6, 7, and 17 which contain about 80% of autosomal dominant SCA cases. Various aspects of eye movement abnormalities are evident depending on the degree of cerebellar and brainstem degeneration in SCAs. In addition, certain types of SCAs such as SCA7 are characterized by both cerebellar ataxia and visual loss mainly due to retinal degeneration. The severity of the retinopathy can vary from occult macular photoreceptor disruption to extensive retinal atrophy and is correlated with the number of CAG repeats. The value of using optical coherence tomography in conjunction with electrodiagnostic and genetic testing is emphasized as the combination of these tests can provide critical information regarding the etiology, morphological evaluation, and functional significances. Therefore, ophthalmologists need to recognize and differentiate SCAs in order to properly diagnose and evaluate the disease. In this review, we have described and discussed SCAs showing ophthalmic abnormalities with particular attention to their ophthalmic features, neurodegenerative mechanisms, genetics, and future perspectives.

The Combination of rTMS and Pharmacotherapy on In Vitro Models: A Mini-Review

BACKGROUND

Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive brain stimulation technique that is being actively explored as a potential therapeutic modality in various neuropsychiatric disorders, such as depression, neuropathic pain, epilepsy, multiple sclerosis, and neurodegenerative disorders, including the Parkinson's and Alzheimer's disease. The Food and Drug Administration (FDA) approved rTMS for the treatment of major depression, migraine-associated headaches, and Obsessive Compulsive Disorder (OCD). The fact that a significant proportion of patients suffering from these disorders fail to respond to current pharmacological interventions indicates the need for alternative therapies like rTMS.

OBJECTIVE

The objective was to find and summarize all studies combining the use of rTMS and pharmacological interference in vitro, in order to facilitate future studies.

METHODS

The results of studies combining the use of rTMS with pharmacological interference in vitro were focused on. The PubMed database was searched using the terms "rTMS", "repetitive", "transcranial", "magnetic", "stimulation", "in vitro", "in vivo", "cell cultures" untilMarch 2019 and 7 eligible studies were found.

RESULTS

Overall results show a synergistic effect of rTMS and pharmacotherapy in vitro with additive effectiveness, better prognosis, and superior potential management.

CONCLUSION

The limited amount of knowledge denotes the need for additional in vitro studies on the combination of rTMS and pharmacotherapy, which could be extended to in vivo studies and ultimately help design clinical trials so as to improve the therapeutic management of patients with a wide array of neuropsychiatric disorders.