Aim: 

Spinal muscolar atrophy (SMA) is an autosomal recessive motor neuron disorder characterized by degeneration of the antherior horn cells of the spinal cord leading to weakness and muscular atrophy. On the basis of age of onset and severity of the clinical course, the disease can be classified into three forms (type I, II, III). All forms are caused by homozygous loss of the survival motor neuron gene that encode the SMN protein. In the present work we focused our attention on the SMA type III mouse model, which describes a mild form of the pathology.

Methods: 

In five and nine months old type III SMA and wild type mice EMG recordings were performed. Animals were anaesthetized with intraperitoneal injection of a mixture of ketamine (60 mg/kg) and xylazine (3,5 mg/kg). For EMG testing, monopolar needles positioned in distal pelvic limb muscles were used and muscular potentials were recorded with and without wave pulse stimulation.

Results: 

Type III SMA mice revealed both a spontaneous and induced abnormal electrical activity more frequent and evident in nine months old mice. The characteristic pattern consisted in the appearance of fibrillation potentials and fasciculation potentials, accompanied occasionally by biphasic positive sharp waves. We did not see abnormal electrical activity in age-matched wild type mice.

Conclusion: 

Our results, besides to characterize further the mouse model of SMA type III, indicate how the EMG recording might be useful to evaluate the efficacy of a therapeutical approach.