Motor function reorganization in a patient with a brainstem lesion: DTT, fMRI and TMS study

We report on a hemiparetic patient who showed a new motor pathway posterior to the lesion in the midbrain and upper pons, demonstrated by three combined method of diffusion tensor tractography(DTT)/functional MRI(fMRI)/transcranial magnetic stimulation(TMS).

A 21-year-old left hemiparetic male who suffered from tuberous meningitis at the age of 12 months after birth. The evaluations were performed at 20 years after onset. Brain MRI showed focal encephalomalatic lesions~due to infarcts in right anterior thalamus, midbrain and upper pons. DTT, fMRI and TMS were performed simultaneously.

The contralateral primary sensori-motor cortex was activated during either affected or unaffected hand movements. DTT showed that the motor tracts descended along the known pathway of the CST, with the exception of the motor tract of the affected hemisphere, which descended along the posterior portion to the lesion in the right midbrain and the pons, and then rejoined the CST in the mid-pons. The TMS results suggested that the motor tract of the affected hemisphere had the characteristics of a CST.

We believe that the motor function of the affected hand in this patient had been recovered through the pathway posterior to the lesion in the midbrain and upper pons.