ABSTRACT
Syncope is a sudden, transient loss of consciousness, as well as loss of postural tone. Syncope results from an abrupt decrease in cerebral perfusion or essential substrate delivery. It can be difficult to differentiate syncope from seizure activity or, sometimes, episodes of transient weakness. Syncope is often associated with sudden exertion or excitement. Limb stiffening, opisthotonic posture, micturition, and vocalization are common. Syncope occurs when cerebral blood flow falls below a critical level; this is about 30–50% of normal in people, although it might differ for quadripeds. Reduced cerebral blood flow also can result from cerebrovascular or other intracranial disease. Cardiac arrhythmias, as well as organic heart disease, commonly are involved. Quadrupedal posture makes this less likely in companion animals, although it does seem that sudden excitement might precipitate this in dogs. Arrhythmic causes of syncope can occur during sleep such that a loss of consciousness might not be observed, but might result in seizure-like activity, opisthotonus, urination.
