Diffuse axonal injury mimicking metastatic brain tumor

Abstract

Introduction: Diffuse axonal injury (DAI) is frequently caused by traumatic brain injury. DAI results from shearing forces at the interface between brain structures of different density and rigidity. MRI is valuable in detecting traumatic lesions. T2-weighted fast spin echo (FSE) and fluid-attenuated inversion recovery(FLAIR) MRI sequences can demonstrate hyperintense lesion at gray-white matter junctions. Also, T2-weighted gradient echo (GRE) sequences improve detection of hemorrhagic lesions that occur in 20-30% of patients with DAI. However, multiple white matter lesions with enhanced property may cause confounding result with other disease, like metastatic brain tumor, sarcoidosis, or other infectious etiology, especially in patients with uncertain trauma history. We experienced one DAI patient who had uncertain traumatic brain injury, and initially was suspected as metastatic brain tumor.

Case: A 52-year-old male visited our outpatient clinic with the complaint of progressive right hand motorweakness and headache that aggravated from 1year ago. He was chronic heavy alcoholics, and had liver cirrhosis. He denied trauma history including head injury. Neurological examination revealed distal dominant right hand paresis, thenar muscle atrophy and web muscle wasting. Other findings were not significant. He had been checked brain MRI at 1year ago. This brain MRI showed small multiple high signal white matter lesions in T2-weighted FSE and FLAIR with gadolinium enhancement on T1-weighted imaging. Therefore,we suspected metastatic brain tumor as a tentative diagnosis initially. Through intensive investigation about malignancy, we recognized that there was no evidence of suggesting malignancy. Moreover, follow-up brain MRI showed decreased number of multiple white matter lesions and no gadolinium enhanced lesions. At this time, we focused on his heavy alcohol consumption and frequent loss of consciousness history, and we reviewed brain MRI findings. Finally, we diagnosed with DAI.

Discussion: Axonal damage is one of the most common and important pathological feature of traumatic brain injury. The axonal injury with focal hemorrhage is located centrally in the junctional areas of the subcortical gray-white matter, corpus callosum, basal ganglia, and dorsolateral region of the rostal brainstem. In these areas, T2-weighted FSE and FLAIR high signal intensity with gadolinium enhancement may lead to misdiagnosis, such as metastatic brain tumor, sarcoidosis, and other infectious disease. We report one patient with DAI, who initially was suspected with metastatic brain tumor.