Abstract
Background: Diffusion-weighted imaging (DWI) can disclose cytotoxic injury before abnormalities become conspicuous on conventional magnetic resonance imaging. Anatomical distribution may help distinguish causes of acute or rapidly progressive altered mental status.
Case presentations: We describe three patients investigated on a 3-Tesla MRI system (Siemens VIDA). A 66-year-old man with rapidly progressive dementia had bilateral symmetric cortical ribbon-like restriction, supporting Creutzfeldt–Jakob disease. A 77-year-old man with West Nile virus encephalitis had symmetric restriction in the thalami, basal ganglia, and midbrain. An 11-day-old girl with viral meningoencephalitis had diffuse restriction in the corpus callosum and bilateral periventricular white matter, a pattern associated with human parechovirus infection. In each case, Diffusion-weighted imaging (DWI) made the abnormality more conspicuous than T2-weighted or fluid-attenuated inversion recovery imaging.
Discussion: The three distributions - cortical, deep gray nuclear/brainstem, and neonatal white matter - provide a practical pattern-recognition framework. Diffusion-weighted imaging (DWI) is sensitive but not etiologically specific; interpretation requires apparent diffusion coefficient confirmation and correlation with age, clinical presentation, examination, electroencephalography, and microbiologic or prion testing.
Conclusion: In patients with altered mental status, early attention to the anatomical distribution of true restricted diffusion can prioritize a focused differential diagnosis and prompt appropriate confirmatory testing. These cases also illustrate the need to employ a pattern-based approach and avoid equating conspicuous diffusion-weighted imaging (DWI) signal with acute ischemia in nonvascular distributions.