[Chronic hydrocephalus in adults]

The aim of this study is to sum up our current knowledge on the so-called "normal pressure hydrocephalus" syndrome, revisited by the authors as the "adult chronic hydrocephalus" syndrome (A.C.H.). It is based upon 1) a review of the literature dealing with the subject (518 references) and 2) an original series of 243 cases summarizing a 10 year experience of 2 french neurosurgical teams (Lyon: 123 cases, Clermont-Ferrand: 120 cases). Part I is devoted to the review of pathologic and pathophysiologic data. Both autopsy and microscopic findings clearly show 2 categories of anomalies in the brains of patients showing this condition: "non specific" lesions may be either causative (leptomeningeal thickening, villositar sclerosis) or secondary to hydrocephalus (ependymal wall disruption, sub-ependymal "edema"). Conversely, "specific lesions" are either degenerative (Alzheimer-type) or ischemic in origin. They seem unrelated to hydrocephalus, but may play a role in the ventricular enlargement by favoring changes in brain elastic properties. Data available from brain biopsies (13 cases) have confirmed the high incidence of such "specific lesions" of the parenchyma. Following the Hakim's initial hypothesis, several mechanisms have been proposed to explain the progressive ventricular dilation despite a fall in C.S.F. pressure. Experimental and clinical data (namely those referring to the pathogenesis of secondary A.C.H.) are reviewed. The sequence of events following acute ventricular obstruction is analysed. The ultimate state of chronic uncompensated hydrocephalus involve multiple factors among which a trans-cerebral mantle pressure gradient may play a major role. The intervention of compensatory mechanisms (reduction of C.S.F. production, establishment of alternative pathways of C.S.F. absorption) is also discussed. Part II is devoted to the presentation of the clinical material. Series of the literature including more than 20 surgical cases are briefly reviewed together with the authors' material and methods. Criteria of selection of patients, methods of clinical evaluation and of statistical analysis of results are exposed. Of the 243 patients of the present series, 225 were managed by C.S.F. shunt (V.A.: 137, V.P.:60, L.P.:28). Results were as follows (mean follow-up:31 mths +/- 28): good results (including excellent results): 128 (52.6%), fair: 52 (21.3%), poor and aggravated: 49 (20%), early deaths: 14 (5.7%), 12 of those post-operatively. The rate of surgical complications was 35% (S.D.H.: 16.8%, sepsis: 4%, seizures: 4%, shunt malfunction: 10.6%) leading to reoperation in 25.7%. Long-term survival rate was 75% (172 alive patients and 57 late deaths).(ABSTRACT TRUNCATED AT 400 WORDS)