The role of alertness in organic brain syndromes

We examined 35 patients, aged from 37 to 76 years, with impairment of intellectual functions due to normotensive hydrocephalus of varied origin. Axial tomography showed an enlarged ventricular system, with or without cortical atrophy. As a rule, the patients having no cortical atrophy displayed a significantly lower alertness level than the patients with cortical atrophy, who were more alert. Because the clinical picture was similar in both subgroups, it was postulated that the impairment of cortical function due to organic lesions resulted in symptoms similar to those due to chronic decrease of alertness. According to this hypothesis, there are two types of symptoms in patients with organic brain syndromes, one type being dependent on the alertness decrease and not on the organic lesion itself. Although the two types cannot be easily distinguished during clinical examination, the prognosis is substantially different for "organic" and "functional" symptoms. The hypothesis was supported by observations in 19 patients selected for ventriculoperitoneal shunt operation. Reexamination 3 months after the operation showed that the improvement was not related to changes in the organic substrate, i.e., to the diminished size of the lateral ventricles and of the third ventricle. On the other hand, the clinical improvement was significantly correlated to the increase of the alertness level after treatment.