Diffusion Tensor Tractography in Two Cases of Kernohan-Woltman Notch Phenomenon
A 67-year-old man was admitted to the emergency room after an assault. The patient showed altered mentality and initial Glasgow Coma Scale was 3/15. Initial brain CT scan showed an acute frontotemporoparietal subdural hemorrhage (SDH) on the right side (). An emergent craniectomy and hematoma removal was done. After the operation, his cognitive function gradually improved to a Rancho Los Amigos level of function V. However, increased spasticity and weakness of muscles were noted on the right side: Motor grade, 2/5; Fugl-Meyer assessment, upper 6+lower 10=16/100; Manual Function Test, right 0/32. MRI was taken 5 days after injury. However, there were no abnormal signal changes on the cortical and subcortical areas of the left hemisphere or brainstem including the cerebral peduncle (). Nonetheless, his paradoxical ipsilateral motor weakness persisted.\nDTI images were obtained 4 weeks after onset of the injury. DTI was acquired using a 3.0-T Philips Gyroscan Intera MRI scanner (Philips Healthcare, Best, The Netherlands) with a six-channel phased array sensitivity encoding (SENSE) head coil. Images were obtained based on the single-shot echo-planar image sequence. The DTI data parameters were as follows: field of view 224×224 mm2; matrix 112×112; repetition time (TR)=9,131 ms; echo time (TE)=85 ms; slice thickness=2 mm; SENSE factor=2; and b=1000 s/mm2. We obtained 70-75 gapless, contiguous transverse images with each of 32 noncollinear diffusion-sensitizing gradients.\nFiber tracking was analyzed using the "FiberTrak" package included in the Extended MR Workspace R 2.6.3.1 software (Philips Healthcare). The setting parameters for the tractography were as follows: minimum fractional anisotropy (FA)=0.15; maximum angle change=30°; minimum fiber length=10 mm. Two regions of interests (ROI) were selected to reconstruct the CST. One ROI was placed on the CST portion of the anterior lower pons and the other was placed on the CST portion of the anterior mid pons.\nIn the fiber tracking with the DTI image, constructed fibers passed through the CST. However, disruption of fibers was observed around the left pons. The FA and apparent diffusion coefficient (ADC) values were obtained from posterior limb of internal capsule (PLIC), cerebral peduncle, and anterior pons of both hemispheres (). The FA values of the left cerebral peduncle and anterior pons were decreased compared to those of the contralateral side. The DTI images were obtained again 9 months after the onset of injury, and previously disrupted fibers were unchanged (). FA values of cerebral peduncle and pons on the affected side were increased, while there was no significant difference in the relative decrease of the previously acquired FA value on the left side. ADC values of the left hemisphere were similar or slightly higher than those of the right hemisphere in initial and follow-up images (). At 15 months post-injury, he was able to ambulate with a quad-cane under supervision, but was unable to grasp and release freely: Fugl-Meyer assessment, upper 24+lower 8=32/100; Manual Function Test, right 4/32.