A distinction must be made between idiopathic falls and those falls which are merely unexplained
"Idiopathic falls," caused by a personal, non-occupational pathology (such as a myocardial infarction, fainting spell, or epileptic seizure), are not covered, unless the employee strikes a "hazard" (such as a desk); in those cases, injuries caused by the hazard are covered, but the underlying condition is not.
If a fall is not shown to be caused by an idiopathic condition, it is simply unexplained and is therefore compensable if it occurred in the performance of duty.