Two cases of akinetic mutism which followed a pneumoencephalogram and ventriculogram, respectively, as well as 2 other cases with symptoms of partial akinetic mutism were reported. All 4 patients had obstructive hydrocephalus due to different etiologies. Literature was reviewed regarding the patho-physiology of akinetic mutism as well as a survey of reported etiologies of this syndrome. The following 4 pathophysiologic phases describe the progression of symptoms seen in the 1st 2 cases and, to a lesser extent, in the other 2 cases. This continuum, which might be called the "periventricular white matter syndrome," includes: [phase 1] development of pyramidal tract signs in the lower extremities, [phase 2] development of ataxla which resembles the so-called "frontal lobe" a tax La, [phase 3] appearance of apraxia of gait, and [phase 4] development of a total apraxia represented by the complete syndrome of akinetic mutism after sudden change in the gradient of intracranial pressure. In the 1st 2 cases phases 3 and 4 were reversible after shunting or removal of the block. While obstructive hydrocephalus does not explain all cases which present with the above continuum or complete akinetic mutism, it is a common denominator in many cases and not just an incidental finding.