Thalamic probabilistic connectivity with cerebral cortex and its correlation with motor outcome in spastic cerebral palsy

Motor impairment is the main disabling impact of spastic cerebral palsy (SCP). Thalamus is the major relay station for nearly all pathways to cerebral cortex and is one of the targets of deep brain stimulation therapy in cerebral palsy. Whether the pathways between the thalamus to motor cortex in spastic cerebral palsy are disrupted remains unclear and the study on its pattern of connectivity is sparse. Hence, this retrospective study aims to investigate the probabilistic connectivity between the thalamus and motor areas of cerebral cortex as well as to assess its correlation with Gross Motor Function Measures (GMFM) in spastic cerebral palsy patients. Probabilistic tractography was performed on secondary MRI data of ten healthy control and ten non aged-matched SCP patients (mean age 12.8 years old). Thalamus was set as the seed region while the three areas of motor cortex, particularly primary motor cortex, premotor cortex and supplementary motor area were the target regions. Connection probability index, which is the indication of white matter integrity, was measured between the thalamus to each motor cortex. Correlation between the thalamo-cortical connectivity with GMFM was performed in SCP patients. The thalamus was further parcellated according to its connection with specific motor cortex. It has been found that the pattern of thalamo-cortical connectivity in cerebral palsy was varied according to the patient’s clinical presentation. Some connection probability indices in SCP were lower than control but some were higher. The findings revealed that there was no correlation between the thalamo-cortical connectivity with GMFM. Thalamic parcellation in control showed that the thalamic cluster with positive connection to primary motor cortex was associated with the lateral group nuclei, which contain the thalamic motor nuclei. A striking feature of thalamic parcellation in SCP was the presence of cluster with positive connection to supplementary motor area. The findings suggest that the SCP brain network was unique according to the clinical manifestation. There was also an evidence of neuroplasticity as a compensatory mechanism for the motor deficit in spastic cerebral palsy