Diagnostic value of apparent diffusion coefficient hyperintensity in selected patients with acute neurologic deficits

Background and Purpose. A pattern of decreased intensity on apparent diffus ion coefficient (ADC) maps is useful in the early detection of ischemic bra in injury. Less information exists with regard to patients with acute neuro logic deficits in whom there is abnormal conventional magnetic resonance im aging (MRI) and increased ADC intensity. Methods. The authors identified 13 patients with acute neurologic deficits who underwent diffusion MRI and ha d calculated ADC maps demonstrating hyperintensity in regions characterized by computed tomography hypodensity and MRI T2 hyperintensity. The initial and follow-up imaging characteristics and clinical syndromes were recorded. Results. Clinical syndromes included hypertensive encephalopathy, posterio r leukoencephalopathy, hyperperfusion following carotid endarterectomy, ven ous sinus thrombosis, HIV encephalopathy, and brain tumor. Diffusion-weight ed imaging (DWI) was hyperintense in 3 of 13 patients, isointense in 4 of 1 3 patients, heterogeneous in 3 of 13 patients, and hypointense in 3 of 13 p atients. The ADC values in these regions were significantly higher than tho se in control regions (P < .0001). At early follow-up, MRI abnormalities re solved completely in 3 of 13 patients and partially in 9 of 13 patients. MR I abnormalities were unchanged in 1 patient. Conclusions. In the evaluation of patients with acute neurologic deficits, ADC hyperintensity may identif y a subset of patients with vasogenic edema of nonischemic etiology. Freque ntly, these conditions are potentially reversible if appropriately managed. DWI and conventional images alone are not sufficient to identify these neu rologic conditions.