Mild Diffuse Axonal Injury Research Articles

ROLE OF MRI IN THE EVALUATION OF DIFFUSE AXONAL INJURY

INTRODUCTION: Diffuse axonal injury (DAI) is a relatively less common but severe form of traumatic brain injury. It occurs due to shearing forces and is identied as one of the most important causes of morbidity and mortality in patients with traumatic brain injury. MRI is found to be diagnostic when CTndings are normal and there are persistent unexplained neurologic ndings or at subacute and chronic periods. AIM: To evaluate the role of MRI in the diagnosis of diffuse axonal injury. MATERIALAND METHODS: 9 Subjects were identied retrospectively with the diagnosis of DAI on MRI in last 2 years. The 1.5TMRI scans of the patients with DAI included: T1 and T2- weighted imaging, FLAIR imaging and T2*-weighted gradient echo (GRE) imaging. Lesions were identied and compared on all sequences. RESULTS: The lesions were in cerebral white matter location in the cases of mild DAI, whereas in the severe DAI located in basal ganglia, corpus callosum, dorsal part of the brain stem as well as the cerebral white matter. For Haemorrhagic lesions, GRE is the best tool to detect haemorrhagic DAIs. For Non-haemorrhagic lesion, FLAIR and DWI are the best current tool to detect small and non-haemorrhagic parenchymal lesions, displayed as hyperintense lesions.

Serum levels of tau protein increase according to the severity of the injury in DAI rat model.

Traumatic brain injury (TBI) in the form of diffuse axonal injury (DAI) is difficult to diagnose in the early phase of the injury. Early diagnosis of DAI may provide opportunity for developing treatment and management strategies. Tau protein has been demonstrated to increase in the early phase of TBI with high diagnostic accuracy in patients with DAI. We tested the biological plausibility of tau protein using a rat DAI model by evaluating the association between serum tau levels and the severity of brain injury.DAI was induced in animals using the Marmarou model.After a survival of 60 minutes, rats were anesthetized and sacrificed after obtaining blood samples (5ml) from the heart. Eighteenratswereemployedin the present studyand were randomly subjected to sham-operated control (n=4), mild DAI (n=7), and severe DAI (n=7). Of seven severe DAI rats, two rats that had focal injury caused by skull fracture were excluded in the measurement of tau protein level. The serum levels of tau protein in the rat DAI model were found to increase significantly and consistently according to the severity of the injury.Rats with DAI showed significantly higher serum levels of tau protein compared to sham rats; the severe DAI rats had higher levels of tau than moderate DAI and sham rats (sham vs. mild, P=0.02; mild vs. severe, P=0.02). In conclusion, serum tau protein levels may be useful as a biomarker for diagnosing and estimating the severity of DAI in the early phase.

Diffuse Axonal Injury: Epidemiology, Outcome and Associated Risk Factors.

Diffuse axonal injury (DAI), a type of traumatic injury, is known for its severe consequences. However, there are few studies describing the outcomes of DAI and the risk factors associated with it. This study aimed to describe the outcome for patients with a primary diagnosis of DAI 6 months after trauma and to identify sociodemographic and clinical factors associated with mortality and dependence at this time point. Seventy-eight patients with DAI were recruited from July 2013 to February 2014 in a prospective cohort study. Patient outcome was analyzed using the Extended Glasgow Outcome Scale (GOS-E) within 6 months of the traumatic injury. The mean Injury Severity Score was 35.0 (SD = 11.9), and the mean New Injury Severity Score (NISS) was 46.2 (SD = 15.9). Mild DAI was observed in 44.9% of the patients and severe DAI in 35.9%. Six months after trauma, 30.8% of the patients had died, and 45.1% had shown full recovery according to the GOS-E. In the logistic regression model, the severity variables – DAI with hypoxia, as measured by peripheral oxygen saturation, and hypotension with NISS value – had a statistically significant association with patient mortality; on the other hand, severity of DAI and length of hospital stay were the only significant predictors for dependence. Therefore, severity of DAI emerged as a risk factor for both mortality and dependence.

Early diffusion tensor imaging findings in animal models of acute diffuse axonal injury

Objective To establish animal models of diffuse axonal injury (DAI) and discuss the early functional MRI findings.Methods Twenty-five adult white rabbits were divided into control group (n =5),mild DAI group and severe DAI group (n =6) according to random number.Mild DAI group was subdivided into mild DAI 3 h (n =6),1 day (n =4) and 1 week (n =4) groups.Routine MRI and diffusion tensor imaging (DTI) were performed.Parameters measured were fractional anisotropy (FA),apparent diffusion coefficient (ADC),axial diffusivity (AD) and radical diffusivity (RD).Results Significantly increased FA (P＜0.01) and decreased ADC (P＜0.05) and RD (P＜0.01) were detected in severe DAI group compared to control group,but there was no significant variation in AD between the two groups (P ＞ 0.05).Each parameter remained almost unchanged in mild DAI 3 h group and mild DAI 1 week group,but FA was increased (P ＜ 0.01) and RD decreased (P ＜ 0.05) in mild DAI 1 day group,with no changes of ADC and AD.Conclusion DTI is a sensitive way to detect the occurrence and development of DAI and can provide referential images for early DAI diagnosis. Key words: Brain injuries; Diffuse axonal injuries; Diffusion tensor imaging; Rabbits

Isolated bilateral abducens nerves palsy due to traumatic delicate arteriovenous fistula

Background: Ocular motor dysfunction is common in patients with head trauma. Also, traumatic lateral gaze palsy is usually associated with brain stem lesion, peripheral nerve injury with or without basilar skull fracture and lateral rectus muscle injury or entrapment. However, isolated bilateral abducens nerve palsy is extremely rare.Case study: This study describes a case of isolated bilateral abducens nerve palsy in a 35-year-old male with head trauma without cervical and skull fractures. He was diagnosed with mild diffuse axonal injury. During his assessment, he developed mild limb weakness, an ataxic gait and impaired abductive movement in both eyes. Angiography of the left common carotid artery revealed multiple small arteriovenous fistulae in both inferior nasal conchae. After embolization, lateral gaze palsy of his eyes was significantly improved.Conclusions: Based on this case, arteriovenous fistula should be considered as a cause of bilateral isolated abducens nerve palsy.

Role of Brain Perfusion Imaging (SPECT- Tc-99m HM-PAO) in Diagnostics and Follow-up in Diffuse Axonal Injury

Patients with diffuse axonal injury (DAI) may present an array of neurological and psychological symptoms. Magnetic resonance imaging (MRI) and computed tomography (CT) are clearly not sufficient to present the whole spectrum of underlying pathologies especially functional ones. The links between observed psychological changes and functional neuroimaging have not been fully established yet. Still unknown are the timing of DAI, which changes observed in different modalities (CT, MRI, SPECT) are primary (axons torn or severed at the time of injury and focal hemorrhagic lesions) or secondary (traumatic event only alter axonal function to elicit a local swelling followed by disconnection). This case report presents functional neuroimaging (SPECT- Tc-99m HMPAO) and psychological tests as a supplement to MRI and CT. Because of its sensitivity, functional neuroimaging may play an important role in the follow-up of mild DAI.