Optic radiation injury in a patient with traumatic brain injury

Injury of the optic radiation in patients with mild TBI: A DTT study

Objectives

We investigated injuries of the optic radiations (ORs) in patients with mild traumatic brain injury (TBI) by using diffusion tensor tractography (DTT).

Methods

Fifty-two consecutive patients who complained of visual problems showed abnormal visual evoked potential (VEP) latency but no abnormality on conventional brain MRI after mild TBI, and fifty normal control subjects were recruited for this study. Subjects' ORs were reconstructed using DTT, and three DTT parameters (fractional anisotropy [FA], apparent diffusion coefficient [ADC], and tract volume) were measured for each OR.

Results

Mean FA value and tract volume of the OR were significantly lower in the patient group than in the control group (p < 0.05). However, there was no significant difference in the ADC values of the OR between the patient and control groups (p > 0.05). A weak negative correlation was detected between VEP latency and OR fiber number (r = 0.204, p < 0.05).

Conclusions

DTT revealed that OR injuries were not detected on the conventional brain MRI scans of patients who complained of visual problems and had abnormal VEP latency after mild TBI. Our results suggest that DTT would be a useful technique for detecting OR injury in patients with mild TBI.

Diagnostic Approach to Traumatic Axonal Injury of the Optic Radiation in Mild Traumatic Brain Injury

We describe a diffusion tensor tractography-based diagnostic approach to traumatic axonal injury of the optic radiation in a patient who showed visual field defect after mild traumatic brain injury. A 43-yr-old female patient experienced head trauma during a motor vehicle accident. After the head trauma, she noticed visual disturbance. Peripheral field defects were detected in both eyes on the Humphrey visual field test. After diffusion tensor tractography-based reconstruction of the optic radiation, We determined the fractional anisotropy and fiber number of each whole optic radiation. Four regions of interest were placed on the optic radiations based on diffusion tensor tractography configuration. The right optic radiation showed narrowing, and the left optic radiation revealed partial tearing in the posterior portion. The fiber number of the right optic radiation was more than two standard deviations lower than the control mean. The fractional anisotropy values of the regions of interest 2 (the narrowed area of the right optic radiation) and regions of interest 3 (the partially torn area of the left optic radiation) were more than two standard deviations lower than the control mean. Our results suggest that analysis of the configuration and parameters of the optic radiation based on three-dimensionally reconstructed diffusion tensor tractography results is a useful technique in the detection of traumatic axonal injury of the optic radiation in individual patients with mild traumatic brain injury.

Optic radiation injury in patients with aneurismal subarachnoid hemorrhage: A preliminary diffusion tensor imaging report

Visual field defect is one of the various clinical manifestations in patients with subarachnoid hemorrhage (SAH). Little is known about the pathogenic mechanism of visual field defect in SAH. In the current study, we investigated the diffusion tensor imaging (DTI) finding of the optic radiation in patients with SAH following rupture of a cerebral artery aneurysm. We recruited 21 patients with aneurismal SAH (12 males, 9 females, mean age, 52.67 years; range, 41–68 years) who showed no definite lesion along the visual pathway. Twenty-one age-and sex-matched normal control subjects were also recruited. DTI data were acquired at an average of 5.9 weeks (range: 3–12 weeks) after onset and reconstruction of the optic radiation was performed using DTI-Studio software. The fractional anisotropy value, apparent diffusion coefficient value, and fiber number of the optic radiation were measured. The fractional anisotropy value of the optic radiation was significantly decreased, and the apparent diffusion coefficient value was significantly increased, in patients with aneurismal SAH than in normal control subjects. However, there was no significant difference in the fiber number of the optic radiation between patients with aneurismal SAH and normal control subjects. The decrement of fractional anisotropy value and increment of apparent diffusion coefficient value of the optic radiation in patients with aneurismal SAH suggest optic radiation injury. Therefore, we recommend a thorough evaluation for optic radiation injury in patient with aneurismal SAH.

Damage to the Optic Radiation in Patients With Mild Traumatic Brain Injury

BACKGROUND

There are known limitations of conventional computed tomography and magnetic resonance imaging in detecting neural injury in patients with mild traumatic brain injury (TBI). Diffusion tensor imaging (DTI) provides a method to further assess cerebral injury in this patient population. We report 2 patients with mild TBI who showed injury of the optic radiation (OR) as demonstrated by DTI.

METHOD

Two patients who complained of visual field loss after mild TBI and 9 age-matched normal control subjects were recruited for this study. Peripheral field defects were detected with automated perimetry in both patients.

RESULTS

Regarding the configuration of OR, the total volume of OR was decreased in the right OR of both patients compared with controls; in contrast, the left ORs were divided into 2 parts in both patients. The voxel numbers of both ORs in both patients were more than 2 standard deviations lower than that of normal control subjects. The apparent diffusion coefficient value of the right OR in patient 2 was more than 2 standard deviations higher than that of normal controls.

CONCLUSIONS

We demonstrated injury of the OR using DTI in 2 patients who showed visual field defects after mild TBI.

Homonymous Visual Field Loss without Structural Lesion on Magnetic Resonance Imaging: Documented with Positron Emission Tomography and Diffusion Tensor Imaging

The authors describe a 35-year-old man suffering from homonymous hemianopia after head trauma 4 years before but with negative magnetic resonance imaging (MRI) findings. Brain fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸FDG-PET) showed hypometabolism at the unilateral occipital lobe and crossed cerebellar hemisphere, and diffusion tensor imaging (DTI) revealed that the ipsilateral optic radiations were completely interrupted. The crossed cerebellar diaschisis (CCD) observed in the chronic stage of brain damage was caused by cerebellar suppression of the cerebral blood flow due to an involvement of the corticopontocerebellar tract. PET and DTI provide objective means for determining the relationship of functional deficits to head trauma, even in cases where the injury was sustained years prior to the evaluation.

Quantitative volumetric analysis of the optic radiation in the normal human brain using diffusion tensor magnetic resonance imaging-based tractography

To attain the volumetric information of the optic radiation in normal human brains, we performed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are helpful in the study of optic radiation fiber tract information.

Traumatic thalamic injury demonstrated by diffusion tensor tractography of the spinothalamic pathway

BACKGROUND

This study reports on a patient with traumatic brain injury (TBI) with a thalamic lesion in the ventroposterolateral nucleus which was demonstrated by diffusion tensor tractography (DTT) for the spinothalamic tract and its thalamocortical pathway (STP).

METHODS

One patient with TBI and eight normal control subjects were recruited. A 64-year-old woman who had suffered a motor vehicle accident presented with a persisting tingling sensation and pain in her right upper and lower extremities at 3 weeks after onset. The patient showed impaired touch sensation, but normal proprioception. Diffusion tensor imaging was performed at 1 month after onset. Fractional anisotropy (FA) and mean diffusivity were measured using a region of interest method along the STP.

RESULTS

DTT showed normal STP integrities as compared with normal controls. However, the FA values of the left STP at the thalamus were more than 2 SD decreased. The diminished FA value of the left STP in the left thalamus seems to indicate injury of the left ventrolateroposterior nucleus. Central pain and impaired touch sensation of right extremities supports the presence of left STP injury at the ventroposterolateral nucleus in this patient.

CONCLUSION

It is believed that DTT for the STP provides a useful means of detecting thalamic injury in TBI.