Prognostic Significance of Magnetic Resonance Imaging in Detecting Diffuse Axonal Injuries: Analysis of Outcomes and Review of Literature.

Abstract

Diffuse axonal injury (DAI) is the brain injury characterized by extensive lesions in the white matter tracts over a widespread area. DAI is one of the most common and devastating types of traumatic brain injury and a major cause of unconsciousness and persistent vegetative state after head trauma. It occurs in about half of all cases with severe head trauma. This study was undertaken to evaluate the prognostic significance of magnetic resonance imaging (MRI) in detecting DAI and to determine which clinical factors provide prognostic information in patients with traumatic brain injuries. This prospective study was conducted in a tertiary care hospital between April 2017 to May 2019 on 52 patients admitted to the hospital with severe traumatic injuries of the head and clinical diagnosis of DAI. The clinical outcomes and findings of Thecomputerized tomography (CT)/magnetic resonance imaging (MRI) of the brain were assessed at 1 month, 3 months, 6 months, and 1 year on the basis of improvement in Glasgow Coma Scale (GCS), the time required to consciousness, and the duration of hospital stay. The patients were classified into three groups according to the MRI grading classification proposed by Adams. The outcomes at the 6 month follow-up time were dichotomized as non recovered (Glasgow Outcome Scale (GOS) score 1 or 2) or recovered (GOS score 3-5).The following factors were evaluated in relation to outcome: age, admission GCS score, the motor component of the GCS examination at admission and at 24 hours post admission, brainstem injury based on T2-weighted and gradient echo MRI sequences, presence of bilateral brainstem injuries, presence of DAIin the brainstem and the supra tentorial compartment (including the cortex, basal ganglia, and corpus callosum) on both CT and MRI, cerebral contusions, subarachnoid hemorrhage, epidural hematoma, subdural hematoma, and intraventricular hemorrhage. The statistical analysis was performed with x2 between various stages and between patients with and without hemorrhagic DAI. A separate analysis with x2 and Yates' correction was performed after grouping the patients with good recovery and moderate disability against patients with severe disability and vegetative state. The correlation of patients GCS on admission, after 24 hours, and at discharge is statistically significant P < 0.001. Correlation among mean hospital stay in Grade I DAI, Grade II DAI, and Grade III DAI wass statistically significant (f = 70.22, P < 0.001). Correlation among mean time required for consciousness in Grade I DAI, Grade II DAI, and Grade III DAI was statistically significant (f = 181.92, P < 0.001). Based on anatomical location within the brainstem, the poorest outcomes occurred with injury to the medulla- with a 100% mortality rate. Poor outcomes were also associated with any injury to the pons. There was a significant correlation among brainstem injuries that crossed the midline, the motor component of the GCS examination, performed 24 hours after admission and at outcome. The median time to MRI was 1 day (range 0-35 days) among all, but 4 patients underwent MRI within 7 days after admission. Patients who did not recover underwent MRI at an average of 0.8 days after admission, whereas those who recovered underwent MRI at an average of 4.2 days after admission (P = 0.52). To determine if the time from admission to MRI had an influence on results, comparison was made between T2 and patient outcomes in relation to the interval between admission and MRI. Statistical analysis in the group of patients with different DAI stages showed a significant difference (P = 0.013). A statistically significant difference was also found between patients with hemorrhagic and non hemorrhagic DAI (P = 0.004). The current study showed a correlation between the mean time interval to recovery of consciousness in patients with DAI and the severity of injury grading on MRI. Hospital stay required for Grade I DAI was 2-3 weeks, for Grade II DAI was 3-4 weeks, and for Grade III DAI was 7-8 weeks. Apart from the well-known role of the Glasgow Coma Scale (GCS) in the prognosis of the outcome of patients with closed head injury, the presence of hemorrhage in DAI-type lesions and the association with traumatic space occupying lesions are additional poor prognostic signs established in this study. The analysis of outcomes were done for patients admitted with DAI and the current study established that poor outcomes were consistently seen in patients with brainstem injuries and poor results on 24-hour post admission GCS motor examinations.