Urea-Induced Myoclonic Seizures

Abstract

Infusion of urea generated in cats a myoclonic syndrome reminiscent of the excitatory events of clinical uremia. The electrical concomitants of the clinical events were spikes and sharp wave discharges in the lower brain stem reticular formation mostly in nucleus gigantocellularis. Microelectrode recordings revealed that each "electroencephalographic spike" represented a 30 to 80 msec depolarization wave with a superimposed cluster of high frequency regenerative potentials, similar to the paroxysmal depolarization shifts described at the levels of neocortex and paleocortex. Intercollicular sections of the brain stem were without significant effect, but sections of the upper cervical cord or curare paralysis depressed the reticular paroxysmal activity. A reticulospinal loop probably represents the anatomofunctional basis of this paroxysmal activity. Urea specifically generates these phenomena since identical plasma osmolality induced by other hypertonic solutions did not produce them.

Focal reflex myoclonus

“…Lance and Adams (1963) stated that intention myoclonus was invariably associated with cerebellar dysfunction which may alter the thalamocortical discharge. This may be present in our patient, but it is unlikely that there is dysfunction of the lower brain-stem reticular formation, such as the nucleus gigantocellularis, which may be necessary for the production of the generalized myoclonus which occurs in experimental urea infusion (Zuckermann and Glaser, 1972) and in human uraemia. An animal experimental model suggesting that myoclonus may represent a release phenomenon has been produced by Milhorat (1967) in the monkey by excision of the medial thalamus.…”

Uraemic myoclonus: an example of reticular reflex myoclonus?

“…It is, therefore, of interest that infusions of urea cause myoclonus in cats. Zuckerman and Glaser (1972) noted that, during the continuous infusion of urea, cats initially developed asynchronous fascicular muscle twitching, which gradually increased in magnitude, tended to become synchronised, and merged into clear-cut localised myoclonic jerks. Loud noises, proprioceptive stimuli, and voluntary movement evoked generalised myoclonus.…”

Myoclonus: Relation to Epilepsy

“…Experimental animal models suggest that the site of origin is the nucleus reticularis gigantocellularis (Zuckerman and Glaser, 1972). Experimental animal models suggest that the site of origin is the nucleus reticularis gigantocellularis (Zuckerman and Glaser, 1972).…”

“…Electrical recordings reveal that the responsible discharges come from the nucleus reticularis gigantocellularis (Zuckerman and Glaser, 1972). Systemic urea infusion (to mimic renal failure) in cats will induce myoclonic jerking as a prelude to generalized seizures.…”