White matter lesions and normal-pressure hydrocephalus: Binswanger disease or Hakim syndrome?

In 1894, Otto Binswanger [1] described a clinical form of dementia in the elderly characterized by subcortical white matter lesions, "enormously enlarged ventricles, " normal cerebral cortex, and "severe atheromatosis of the arteries of the brain" and concluded, "It is very likely that the subcortical loss of fibers is caused by the deficiency of the blood supply resulting from arteriosclerosis." This condition is known variously as subcortical arteriosclerotic encephalopathy, subcortical ischemic leukoencephalopathy, lacunar dementia, and Binswanger disease [2] . The presence of periventricular, deep white matter infarctions (DWMI) that spare the arcuate subcortical fibers is the typical hallmark of this condition. In 1964, Salomon Hakim [3] published in Bogota, Colombia, the description of a clinical triad of gait apraxia, incontinence, and dementia in adults with hydrocephalus and "normal" CSF pressure. The most striking feature of the syndrome was the possibility of a return to normal function after CSF shunting. Despite widespread disagreement on the terminology, Hakim syndrome currently is known as normal pressure hydrocephalus (NPH). I have pointed out the difficulties in clinically separating Binswanger disease from NPH [2] . In fact, both entities are characterized by prominent changes in ambulation , such as small-step gait (marche a petits pas), gait apraxia, and frequent falls . A subcortical type of dementia, with changes in mood, behavior, and personality, is common in both, as well as pseudobulbar palsy, emotional incontinence, and frontal lobe signs with loss of incentive, drive, and insight. Profound apathy and abulia may be observed in advanced cases of