P 1164. Pre-wallerian Degeneration versus New Ischemic Infarction

Background: Pre-wallerian degeneration is defined as progressive anterograde disintegration of axons and accompanying demyelination following an injury to the proximal axon or cell body. Possible underlying diseases are cerebrovascular infarction, trauma, necrosis, or focal demyelinization. In ischemic infarction, most commonly, the corticospinal tract is involved after middle cerebral artery infarct.

Wallerian degeneration is usually classified into four stages represented by distinct magnetic resonance imaging (MRI) findings. In stage 1, pre-wallerian degeneration, degeneration of the axons and myelin sheaths occurs, leading to hyperintense white matter signal changes on diffusion-weighted imaging (DWI with a corresponding correlate on apparent diffusion coefficient images). T1- or T2-weighted imaging often show no abnormal signal in the early stage.

Although described in 1850 by Augustis Volney Waller, detection of early DWI changes ipsilateral to the infarct zone still lead to misinterpretation as new ischemic lesions, often resulting in unnecessary invasive diagnostic procedures or escalation of antithrombotic therapy.

Aims: To increase knowledge about and awareness of pre-wallerian degeneration as a result of stroke in neonates and children. On the basis of three patients, the MRI correlates of pre-wallerian degeneration will be illustrated and discussed.

Methods: Retrospective case series of three pediatric stroke patients with evidence of pre-wallerian degeneration on MRI.

Results: Three patients could be identified in our database: a 3-day-old male newborn (case 1), a 2.5-year-old boy (case 2), and a 10-year-old girl (case 3). In all three patients, poststroke DWI changes in corticospinal tract ipsilateral to the infarct zone were identified at different time points poststroke (days 0, 6, and 13, respectively). In all three cases, these MRI findings were interpreted by the attending radiologist as new ischemic lesions affecting the posterior circulation. This led to more diagnostic procedures and escalation of antithrombotic therapy in all three cases and provoked unnecessary insecurity in parents and doctors. None of the patients showed new neurological signs at that time of imaging. In the following, MRI scans corresponding T2-hyperintens signal alterations occurred at day 8 (cases 1 and 2) and at day 13 (case 3).

Following interdisciplinary cases discussions, pre-wallerian degeneration was diagnosed in all three.

Conclusion: After neonatal or childhood stroke, new or additional DWI changes within the white matter tracts ipsilateral to the infarct zone pre-wallerian degeneration should be discussed as a differential diagnosis. They should not be mistaken as new ischemic lesions, especially when no new neurological signs occurred. Misinterpretation can result in unnecessary diagnostic procedures and escalation of antithrombotic therapy.