Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease that produces weakness and ultimately death from respiratory failure. ALS results in the death of 500 Australians per year, with a median survival of only 2-3 years from diagnosis. Currently there is no accurate objective measure of Upper Motor Neuron damage in ALS.
Aim
The aim of this study was to use two methods, Transcranial Magnetic Stimulation (TMS) and Diffusion Tensor Imaging (DTI) to interrogate the UMN in ALS patients in comparison to control subjects. These tools were used to develop an algorithm to quantify UMN involvement in ALS.
Method
TMS and DTI were performed in ten ALS patients and ten healthy control subjects. TMS is a method for neurophysiological assessment of UMN function and cortical abnormalities. DTI is a magnetic resonance method to investigate CST pathology.
Results
TMS demonstrated an increase in excitability of corticomotoneurons and a decrease in intracortical inhibition, contributing to motor cortex excitability in ALS. The DTI studies identified considerable differences between ALS patients and controls in diffusivity along the CST between the internal capsule and midbrain in patients with ALS. Multiple correlations were demonstrated between the TMS and DTI parameters. An UMN algorithm was developed using TMS and DTI parameters that clearly distinguishes between ALS and control subjects.
Conclusion
A SICI/DTI parameter algorithm is described that can be used to quantify UMN involvement in ALS.