| 제목 |
Diffusion tensor tractography for optic radiation in traumatic brain injury patient: A Case Report |
| 소속 |
CHA Bundang Medical Center, CHA University School of Medicine, Department of Rehabilitation Medicine1, CHA University, Rehabilitation and Regeneration Research Center2 |
| 저자 |
Jongwook Kim1*, Dong Jin Koh1, Jeongson Huh1, MinYoung Kim1,2† |
Introduction
Visual problem especially visual field defect (VFD) is a common clinical symptom in patients with traumatic brain injury (TBI). Humphrey automated visual fields perimetry is a standard assessment and visual-evoked potential (VEP) is additive tool of visual fields test for TBI patients. However most of patients with TBI have cognitive impairment along with other disabilities, it is hard to apply perimetry to them. This case demonstrates the application of DTI and tractography for evaluating OR (Optic radiation) neural injury, which cannot be evaluated by conventional MRI and imprecise VEP findings. DTI and tractography might be useful as alternative visual field evaluation tools with objective results for patients with poor cognitive function.
Case report
A 40-year-old man had traumatic brain injury that caused subdural hemorrhage at the left frontotemporoparietal lobes with midline shift, and epidural hemorrhage at the right frontotemporal area (Fig. 1). He underwent decompressive craniectomy, and after 15 days, acute infarction at the right centrum semiovale occurred. As a result of intensive rehabilitation therapy, he could carry out independent living and occupational activities, but with minimal disturbances in vision. Primary ophthalmologic examination, perimetry, and VEP were inconclusive. The Humphrey visual fields perimetry revealed right hemianopia and left lower quadrantanopia (Fig. 2). The quadrant-field VEP showed no response at the right upper quadrant in any eye, and prolonged P100 latency at the left upper quadrant.
DTI and tractography: fraction anisotropy, mean diffusivity, and voxels number, can be objective indicators for the assessment of the OR (Optic radiation) in TBI patients (Table). Data of diffusion tensor imaging (DTI) and tractography were analyzed by comparing with 5 controls who have no visual symptoms and well-preserved physical and cognitive function (Fig. 3). And the results indicated injuries in the left upper, left lower, right upper optic radiation with increased mean diffusivity and decreased voxels numbers in the tracts. The lesion detected by DTI and tractography correlated well with the patient’s symptoms, which were left hemianopia and right upper quadrantanopia.
Conclusion
This is the first study to analyze optic radiation by dividing it into four distinctive tracts. This case demonstrates the application of DTI and tractography for evaluating OR neural injury, which cannot be evaluated by conventional MRI and imprecise VEP findings. DTI and tractography might be useful as alternative visual field evaluation tools with objective results for patients with poor cognitive function. |
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Figure 1. (A) Brain computed tomography after trauma showed fracture of right temporoparietal bone, large amount of epidural hemorrhage at right frontotemporal region, scalp swelling and laceration at right parietal region, and small contusional hemorrhage and subdural hemorrhage at left frontotemporoparietal region with a midline shift more than 5mm. / Figure 2. The Humphrey visual field test of the patient shows right hemianopia and left lower quadrantanopia of each eye.
Figure 3. Tractography for optic tracts in the patient (A) and the controls (n=5) (B). Blue colour indicates upper optic radiations tract, and red colour indicates lower optic radiations tract.
Table. Summary of the mean diffusivity, voxels number and fractional anisotropy values of optic radiation.
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