A study of a respiratory related variation of muscle tone during the decrement of decerebrate tonicity in ECT.

An oscillating decerebrate tonicity following the clonus phase in electroplexy was found to occur in the upper limbs, their tendon reflexes and the jaw; this increased with each expiration and decreased with inspiration. The times of these occurrences in the upper limbs were measured in groups where no anaesthesia, diazepam or methohexital were used. The mean times of their onset and end were related to other phenomena of ECT. The times of occurrence and duration of decerebrate tonicity were established and compared in the three cohorts. There was a definite relationship to the onset of respiratory rhythmicity in all three groups. The evidence for the existence of decerebrate tonicity and atonicity are discussed from experimental contributions and more recent clinical evidence of the clonus phase as an example of an oscillation between tonic and atonic decerebrate states. Further clinical and experimental data are discussed which show connections between the decerebrate state, cerebral and cerebellar functions, respiratory centres, brain-stem and gravity afferents during rest and locomotion. An explanation is offered that the oscillatory phenomena are probably a mechanism to aid respiration and motor efficiency.