Medial medullary infarction identified by diffusion-weighted magnetic resonance imaging

Objective: To elucidate the frequency and clinical profiles of patients with medial medullary infarction (MMI) identified by diffusion-weighted MRI (DWI). Methods: We assessed the frequency, radiological findings, etiology and clinical features of MMI detected by DWI from our single-center registry of acute ischemic patients. Results: Thirty patients (1.5% of 2,014 with ischemic stroke) had MMI, including isolated unilateral MMI in 26 patients. Lesions were located by DWI in the rostral medulla of 25 patients (83%). Culprit infarcts that were undetectable by DWI in 6 (38%) of 16 patients who were assessed within 24 h after onset were later confirmed as MMI. The major etiological mechanism was small artery occlusion (SAO; 19 patients) and the median initial National Institutes of Health Stroke Scale score was 4 (interquartile range: 3-4.75). The most frequent symptom was contralateral hemiparesis (27 patients). None of the patients fulfilled the classical Dejerine Triad. Twenty-two patients (73%) had a modified Rankin Scale score of ≤2 at 3 months. A patient developed transient ischemic attack within 3 months; none developed recurrent stroke. Conclusions: Rostral medullary infarction with mild neurological deficits resulting from SAO is relatively frequent. Because emergency DWI within 24 h could not detect MMI in one third of the patients, this type of infarction could be misdiagnosed as capsular/pontine lacunae or other neurological disorders.