Abstract
Since the beginning of 1995 the new hydrostatic dual-switch valve (DSV) was implanted
in 35 adult patients with hydrocephalus of different etiology. 26 patients suffered
from normotensive hydrocephalus (10 idiopathic and 16 symptomatic), and 9 patients
from hypertensive hydrocephalus of various origin. The first 21 cases of this cohort
were compared in a randomized study with a comparable group of 21 hydrocephalic patients
who received a conventional differential-pressure (DP-) valve. The clinical status
and CT were assessed prior to shunting, 14 days and 3 and 6 months after the operation.
The reduction of ventricular size was evaluated by the measurement of the Evans Index.
The CT follow-up in the DSV group was characterized by an only minimal (14) or only
slight (16) reduction of ventricular size in the vast majority of cases. A comparison
of 21 patients with a DSV and the patients with DP valves, evaluated by measuring
the reduction of the Evans Index, revealed a distinctly higher percentage of significant
regressions in the DP valve collective, without doubt due to chronic over drainage.
The overall clinical result of our 35 patients with a DSV was excellent and good in
31 patients, but the outcome seems to be more dependent on the preshunt damage of
the brain than on hydrocephalic aspects. A negligible incidence of subdural effusions
in the DSV group compared to 11 cases in the DP valve collective reflects the ability
of the DSV to prevent overdrainage. The capability of the DSV to maintain the IVP
within physiological limits after shunting, especially in the upright position, is
documented by a comparison with possible unphysiological IVP variations in other valve
constructions, which depend on the level of implantation, subcutaneous pressure or
CSF flow through the valve.
Key words
Hydrocephalus - Valve - Overdrainage
