MRI for the management of neonatal cerebral infarctions:: importance of timing

Purpose: Focal ischemic stroke in neonates is a rare occurrence. Diagnosis with most imaging modalities is difficult, but necessary for initiating an anticoagulatory treatment. The purpose of this study was to evaluate the sensitivity of MRI sequences within the first 14 days of birth. Patients and methods: Four patients with neonatal stroke presenting as seizures were examined using a standard MRI protocol including diffusion-weighted images (DWI) and magnetic resonance angiography (MRA) within 72 h of birth. The time between the onset of symptoms and MRI ranged from 6 h to 48 h. Follow-up examinations were performed on days 5 (n=1), 7 (n=2), and 14 (n=1) for the control of a treatment with low-molecular heparin. Results: Eight infarctions were detected in the four patients, 5 in the middle cerebral artery ( MCA), three in the posterior cerebral artery (PCA) territory. All lesions were visible using DWI, four on T2-weighted images. Whereas in two patients small lesions contralateral to a large stroke were missed on T2-weighted images, the diagnosis would have been missed altogether without DWI in one patient. On follow-up, the visibility of the infarctions had declined using DWI after 5 days and the lesions were invisible after 1 week. Fourteen days after the stroke, an increased diffusion was detected in the infarcted brain tissue. By this time, all lesions were visible on T2-weighted images. Conclusion: In neonates, infarcted brain tissue can be detected using DWI with high sensitivity during the first 2 days after stroke and before other sequences are diagnostic. However, the diffusion restriction does not persist beyond 1 week. After 5 days, diagnosis has to rest mainly on T2-weighted images.