Yet another study investigated cognitive functions in a large group of SMA children and adolescents compared to age-matched healthy controls. In contrast, other studies demonstrated superior cognitive abilities of SMA children and adolescents compared to those with DMD. In comparison to published normative data and to the similarly physically disabling disease Duchenne muscular dystrophy (DMD), no significant differences in intellectual performance of SMA patients were reported.
Few studies on cognition in SMA, mainly in children, showed different results. Įxpression of SMN protein has been detected in the human forebrain by immunochemistry, and therefore, a role during brain development is assumed. On average, death due to respiratory insufficiency occurs three to five years after symptom onset. Amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disease, is characterized by the rapidly progressive clinical correlates of the loss of cortical, brain stem and spinal motor neurons. The mildest SMA type 4 phenotype manifests predominantly in adulthood but may also show a juvenile onset in some cases. SMA type 3 includes clinically heterogeneous patients, who typically learn to walk independently, but may lose this ability again over the course of the disease. While type 1 represents the most severe infantile phenotype, type 2 patients, characterized by onset between seven and eighteen months of age, achieve the ability to sit unsupported, but not to walk independently. Spinal muscular atrophy (SMA), an autosomal recessively inherited motor neuron disease caused by mutations in the survival of motor neuron 1 ( SMN1) gene, is differentiated into four main subtypes on the basis of age at onset and best motor function achieved. Future studies should focus on disease-specific cognitive functions in SMA.ĭegenerative motor neuron diseases are primarily characterized by the loss of motor neurons leading to progressive muscle weakness, atrophy and ultimately death often due to respiratory insufficiency. Better cognitive abilities in SMA patients seemed to be related to the early onset, rather than the extent or the duration, of their physical handicap. While SMA and ALS patients were comparable in the vocabulary test, on average, SMA patients performed better than ALS patients in the cognitive domains of memory, language and executive function.
Demographic and clinical parameters were assessed to identify factors that potentially influence cognitive function.
In this prospective multicenter cross-sectional study, cognitive function was assessed by the Edinburgh Cognitive (and Behavioural) ALS Screen (ECAS) and a German vocabulary test (Wortschatztest, WST) in 34 adult patients with SMA types 2–4 and in 34 patients with ALS. Cognitive dysfunction, a clinically relevant non-motor feature in a substantial proportion of ALS patients, has been less frequently investigated in SMA. Motor neuron diseases, such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS), share several clinical similarities while differing substantially in etiology, disease onset and progression.
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