Technical problems and advances in the cerebellar-stimulating systems used for reduction of spasticity and seizures

A series of 300 patients were implanted for chronic cerebellar stimulation (CCS) from February 1974 to June 1980. The charge density was in the range of 0.7-1.6 microCi/cm2/phase. There is a very narrow range of stimulation in which CCS is effective. Increasing above the range, clinical benefits cease; at levels over 10 microCi/cm2/phase, damage to the underlying conducting elements occurs which renders the prosthesis ineffective. Periodic monitoring of the implanted equipment is mandatory for a successful clinical program. Scalp recordings and radiography have detected a 53% failure rate in the I-108 RF linked system. The failed receivers were replaced with more reliable I-110 receivers and later with a fully implantable pulse generator. No change has been detected in the electrode button-cortex interface when measuring the access resistance up to 5 years later.