Pontine ischemic rarefaction.

To investigate apparently asymptomatic, bilateral symmetrical predominantly pontine hyperintensities (PHI) on magnetic resonance imaging (MRI) scans in elderly patients, we examined the pons histopathologically in two brains of elderly hypertensives with PHI, and in three without PHI, on postmortem MRI scans. We also reviewed 85 serial in vivo MRI scans of patients over 60 and compared scan findings, vascular risk factors, and clinical symptoms between patients with PHI and a control group. A subcortical arteriosclerotic encephalopathy (SAE)-like pathology was present in the pons in only the two autopsy brains with PHI and corresponded with the location of PHI on the postmortem MRI scans and with the most frequent sites of PHI on in vivo scans. SAE also involved the hemispheric white matter in one of the autopsy brains. Five of 16 (31%) patients with, and 4 of 69 (6%) without, PHI on in vivo MRI scans had marked periventricular hyperintensity (PVHI) compatible with SAE (p = 0.01). We conclude that an SAE-like pathology may be seen in the pons in elderly hypertensives and this pathology is probably the cause of PHI seen on MRI scans of patients over 60 years of age.