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J Injury of Corticostriatal Tract between the Striatum and the Premotor Area in a Patient with Traumatic Brain

Korea Objectives: We investigated injury of corticostriatal (CStr) tract in patient with mild traumatic brain injury (mTBI), which was demonstrated by DTT. Method: A 44-year-old female with no previous history of neurological, physical, or psychiatric illness had suffered from head trauma resulting from a pedestrian car accident. She complained that could not quickly move the left hand with her intension. After three month’s administration, her slowness movement of left hand recovered rapidly to the point that she was able to extend all fingers quickly. Results: On DTT configuration, the integrity of the left CStr tract was well-preserved, however the right CStr tract showed narrowing and partial tearing in the subcortical white matter on a DTT at 25 months after onset. Conclusion: Injury of the right CStr tract was demonstrated in a patient who developed mild motor control problems following mild TBI. We believe that the evaluation of the CStr tract from the secondary motor area for patients who showed unexplained motor control problem is


INTRODUCTION
The input nucleus of the basal ganglia is the striatum, which coming from motor cortical regions which include the primary sensory-motor cortex, the secondary motor area. 1,2 The corticostriatal (CStr) tract, which connecting between cerebral cortex and the striatum of the basal ganglia, is concerned with important roles in cognitive and motor functions, including action selection, motor control, sequence learning, and habit formation. 3 In addition, connectivity between the striatum and the premotor cortex (PMC) is concerned with the skilled movements and movement sequences including behavioral sequences of hand movements. [4][5][6] Although the CStr tract is a large neural tract in the human brain, injuries of the CStr tract have not been elucidated in detail following mild traumatic brain injury (mTBI). The introduction of diffusion tensor tractography (DTT), which is derived from diffusion tensor imaging (DTI), has enabled three-dimensional visualization and estimation of the neural tract. [7][8][9] However, no study has reported on the injury of the CStr tract. In this study, we report on a patient with mTBI who showed the injured CStr tract, which was demonstrated by DTT.

Case report
A 44-year-old female with no previous history of neurological, physical, or psychiatric illness had suffered from head trauma resulting from a pedestrian car accident. During walk at a crosswalk, she was struck in the left leg by a sedan and fall down to the ground, and directly hit her head after hitting the car. The patient underwent the lost consciousness and post-traumatic amnesia for approximately ten minutes. She complained that could not quickly move the left hand with her intension. When she came the rehabilitation department of a university hospital two years after the stuck, although she showed mild weakness of the left upper extremity in the manual muscle test (manual muscle test: 4/5), we observed the slow, clumsy, and mutilated movements of the left hand when executing grasp-re- with the order from the little finger to the thumb (within ten seconds). No specific lesion was observed on brain MRI (T1-weighted, T2-weighted, and fluid attenuated inversion recovery [FLAIR] images). After three month's administration of dopaminergic drugs for improvement of apraxia, her slowness movement of left hand recovered rapidly to the point that she was able to extend all fingers quickly (within three seconds). [10][11][12] In addition, the clumsiness and mutilated movement was almost disappeared. The patient provided signed, informed consent and our institutional review board approved the study protocol.

RESULTS
On DTT configuration, the integrity of the left CStr tract was well-preserved, however the right CStr tract showed narrowing and partial tearing in the subcortical whit matter on a DTT at 25 months after onset (Figure 1).

DISCUSSION
In this study, using DTT, injury of the right CStr tract was found in a patient who showed abnormal movement of the left hand following mild TBI. We think that the abnormal movement of the left hand in this patient was mainly ascribed to limb kinetic apraxia (LKA). Because we could found characteristics of left hand movements (slow, clumsy, and mutilated), that is compatible with those of LKA (awkward, clumsy, coarse, mutilated pattern of execution of simple movements, confined mainly to movements of the affected hand). In addition, we were able to rule out ideational and ideomotor apraxia because the patient showed normal cognition for motor performance and a normal result on the ideomotor apraxia test. On the other hands, dopaminergic drugs, which have been reported to be effective for treatment of apraxia, appeared to have been effective for improvement of LKA. 10,12,15,16 As a result, we thought that the motor problem of the left hand was attributable to the injury of the CStr tract.
In conclusion, injuries of the right CStr tract were investigated in a patient who developed mild motor control problems following mild TBI.
Since the introduction of DTI, several neurochemical studies reported on the CStr pathway in the human brain. 5,6,[17][18][19][20][21] To the best of our knowledge, this is the first DTT study on injury of the CStr tract in a patient with mTBI. Our results suggest the necessity of evaluation of the CStr tract