Long standing diffusion abnormality of corticospinal tract after large intracranial hemorrhage

Abstract

Introduction: Wallerian degeneration (WD) refers to anterograde degeneration of distal axons and myelin sheaths after injury of the neuronal cell body or proximal axon. The use of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) for detection of WD has been reported. WD has characteristics of high signal intensity on DWI and can be detected transiently. We experienced one WD patient, who showed high signal intensity on DWI and low signal intensity on ADC in corticospinal tract at 1 year after intracranial hemorrhage.

Case: 60-year-old female visited our emergency department with the chief complaint of drowsy mentaliy. Emergent brain CT revealed hypertensive intracranial hemorrhage (ICH) in left stritocapsular area. After intensive treatment, she showed alert mentality, but left hemiparesis has been persistent. At 1 year later, we did brain MRI, and which showed high signal intensity on DWI and low signal intensity on ADC along the corticospinal tract . anterior medulla, basis pontis, crus cerebri, internal capsule, and centrum semiovale. So, we assessed that high signal intensity lesions may be due to new ischemic lesion. But, there was no correlated symptom, and lesions were not explained with vascular territory. Also, diffusion tensor images (DTI) revealed significantly reduced fractional anisotropy (FA) in cortocospinal tract compared to contralateral side. We concluded that those signal is compatible with WD due to intracranial hemorrhage 1 year ago.

Discussion: Previous study reported that in WD, abnormal signal was not detected on any pulse sequence for 6 months after cerebrovascular accident. But, our case showed diffusion abnormality as long as 1year. Also, because ADC showed low signal intensity, we initially misinterpreted that those signal was due to new ischemic lesion. We report one case which in WD, showed diffusion abnormality at 1 year after ICH.