Aberrant pyramidal tract in a patient with corona radiata infarct A diffusion tensor tractography study

The aberrant pyramidal tract refers to the collateral pathway of the pyramidal tract through the medial lemniscus in the brainstem.A 63-year-old male patient presented with severe paralysis of the left extremities due to a right corona radiata infarct.He was able to extend the affected fingers against resistance at 2 months after stroke onset.At 6 months after stroke onset,he was able to perform some fine motor activities,as well as to walk with a nearly normal gait.Functional MRI,which was performed at 6 months after onset,showed that the contralateral primary sensorimotor cortex was activated during affected(left) hand movements.Diffusion tensor tractography results showed that at 2 weeks after stroke onset,pyramidal tracts of the affected hemisphere originated from the primary motor cortex and descended along the known pathway of the pyramidal tract with an aberrant pyramidal tract,which was bypassed through the medial lemniscus from the midbrain to the lower pons.However,the pyramidal tract from midbrain to pons in the affected hemisphere could not be depicted by diffusion tensor tractography at 6 months after stroke onset;instead,only the aberrant pyramidal tract existed for the course of the disappeared pyramidal tract.Results from this study indicate that the main motor functions of the affected extremities appeared to be controlled via the aberrant pyramidal tract with degeneration of the pyramidal tract in the brainstem of the affected hemisphere.