Epileptogenic effects of pure metals implanted in motor cortex of monkeys

The ability of pellets of 26 pure metals to induce clinical epilepsy was evaluated in chronic experiments in 40 monkeys after precentral motor cortical implantation. Nickel and antimony were most effective. A variable mild epileptogenic effect was noted with bismuth, cadmium, zirconium, tin, titanium, iron, molybdenum, mercury, vanadium, tungsten, and tantalum. Other metals, including lead, beryllium, silicon, copper, silver, chromium, cobalt, manganese, zinc, and magnesium were ineffective. Most metal implants were associated with local meningocerebral cicatrix formation, but with five metals (nickel, copper, mercury, antimony, and cadmium) a profound, severe, necrotizing foreign-body reaction occurred. Clinical evidence of toxicity attributable to the metal implants was noted in monkeys treated with nickel, antimony, cadmium, and thallium.