Diffusion-Weighted-Imaging Negative Stroke Syndromes

Objective: Normal diffusion-weighted imaging (DWI) during the acute symptomatic phase of an ischemic stroke is a rare, but a well-known phenomenon. The exact rate and the clinical correlates of this phenomenon are not satisfactorily elucidated. Materials and Methods: Consecutive patients who were hospitalized with the diagnosis of acute ischemic stroke in the last 10 years and who had DWI (with a bmax of 1000 s/mm2) in the first 12 hours were included. A systematic review of published DWI-negative stroke cases and case series was performed. Alternate diagnoses including transient ischemic attack or stroke mimics such as seizure, migraine, functional disorders, and post-stroke recrudescence were excluded. Results: The diagnosis of DWI-negative stroke syndrome was made in 20 (1.3%) of 1.506 patients hospitalized in Hacettepe Hospitals. A literature search disclosed another 535 (6.6%) DWI-negative strokes out of 8.101 cases. A total of 115, identified in case reports and cohort (n=19) articles, were combined with our cases to delineate further characteristics of DWI-negative clinical stroke syndromes. DWI-negative syndromes (n=135) were “brainstem mini-strokes” (31.1%), “cortical small embolic infarcts” (5.2%), “pure penumbral stroke” (normal DWI with magnetic resonance perfusion deficit) (34.8%); “aborted stroke” (early and fully recanalized stroke, only diagnosable in patients with documented acute vessel occlusion) (5.2%); and “miscellaneous” (23.7%). Corresponding clinical stroke syndromes include partial hemispheric deficits (36.1%), focal cortical syndromes (4.3%), caudal brainstem syndromes (9.3%), acute isolated vertigo (9.3%), vertigo-plus syndromes (10.1%), ocular syndromes (7.4%), movement disorders (1.9%), typical lacunar syndromes (11.1%), and atypical lacunar syndromes such as ataxia ± dysatrhria (9.3%). Conclusion: In clinical practice of acute ischemic stroke, early DWI imaging can be negative in various clinical syndromes. Imaging repetition is necessary for the diagnosis and management plan of these patients