MRI-based Brain Structural And Functional Abnormalities In Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis（ALS）is a progressive motor neuron disease involving dysfunction and death of upper and lower motor neurons in the motor cortex,brain stem and spinal cord.It is also called "gradual freezing disease",because ALS patient’s muscles gradually atrophy and become paralyzed,whose body seems to be gradually frozen.The exact cause of ALS is still unclear,and there is no specific cure.Therefore,it is of great significance to study the pathophysiological mechanism of ALS for the early diagnosis and treatment of this disease.Studies have shown that,generally,cerebral cortex of ALS patient has abnormalities both in structure and function.In this study,by analyzing magnetic resonance imaging data of ALS patients and healthy controls,starting from the abnormal atrophy of cerebral cortex surface area,we explored structural and functional abnormalities in cerebral cortex of ALS patients,which might provide new insights for the abnormal brain connection patterns in ALS.In this study,structural and functional MRI data of 120 subjects（60 ALS patients and 60 healthy controls）were processed and analyzed.Changes in cortical surface area,as well as structural and functional connectivity,were compared.Results showed that compared with healthy controls,cortical surface area of left precentral gyrus in patients with ALS was significantly reduced.Cortical areas connected to the left precentral gyrus in ALS brain were more widely distributed,involving the bilateral pre-and post-central,middle and superior frontal,lateral temporal,occipital and parieto-occipital areas.Patients with ALS showed significantly enhanced functional connectivity between left precentral gyrus and bilateral postcentral gyrus.Results also showed decreased selfinhibition in left precentral gyrus.It is inferred that possible reasons for abnormally enhanced brain connections and abnormally weakened self-inhibition are increase of the excitatory neurotransmitter glutamate and decrease of the inhibitory neurotransmitter γ-aminobutyric acid in neurons of left precentral gyrus in patients with ALS.The imbalance between the two may lead to dysfunction and death of cerebral cortical neurons in patients with ALS due to "excitotoxicity" effect,showing degeneration in patients with ALS macroscopically.Neuron death accounts for the reduction of cortical surface area,which is functionally manifested by decreased self-inhibition in left precentral gyrus.In order to compensate for this,ALS showed more extensive connections between left precentral gyrus and whole cerebral cortex in terms of structural connectivity,showing the characteristics of degeneration and synchronous compensation in patients with ALS,which may provide some references for further research of this disease.