POSTERIOR LEUKOENCEPHALOPATHY WITHOUT SEVERE HYPERTENSION - UTILITY OF DIFFUSION-WEIGHTED MRI

Objective: Standard MRI confirms the diagnosis of posterior leukoencep halopathy syndrome (PLES), recently associated with an increasing numb er of medical conditions. In PLES, Ta-weighted MRI demonstrates hyperi ntensity spreading out from posterior brain regions; the pathophysiolo gy remains mysterious. In the acute setting, diffusion-weighted imagin g (DWI), but not standard MR imaging, can distinguish ischemic injury from those conditions known to cause vasogenic brain edema. DWI is pot entially valuable in understanding the pathophysiology of PLES and in diagnosing patients who do not have previously known risk factors. Met hods: Serial CT and MRI studies (including DWI, apparent diffusion coe fficient [ADC] maps, and, in one instance, perfusion-weighted imaging) were performed in three female patients with a neurologic syndrome co nsistent with PLES while hospitalized for treatment of other condition s. Results: None of the patients had previously described risk factors for PLES; all had only mild elevations in blood pressure. MRI showed large, abnormal, T2 hyperintense regions in the posterior cerebrum wit h corresponding hyperintensity on ADC maps-signal characteristics pred ominantly consistent with vasogenic edema. There were also smaller pat chy posterior cortical regions with decreased ADC and bright DWI consi stent with infarction in one, and dramatic conversion of a large regio n to an ischemic pattern in another. Conclusions: ADC maps and DWI can successfully differentiate PLES from early cerebral ischemia, thus pl aying a pivotal role in treatment decisions. PLES is associated with a wider variety of conditions than has been previously reported and is not always reversible. Hyperintense DWI signal in patients with the sy ndrome likely marks a tissue stage of permanent brain injury.