Pneumorrhachis is defined as the presence of air within the spinal canal. In most cases it is reabsorbed spontaneously within a few days.
Classification by location:
(1) intradural (within the subdural or subarachnoid space)
(2) extradural (epidural, intraspinal)
Categories of causation:
(1) iatrogenic
(2) traumatic
(3) nontraumatic, including spontaneous/idiopathic
Specific causes have included:
(1) high intrathoracic pressure and barotrauma, including violent coughing or severe vomiting
(2) malignancy
(3) inhalational drug abuse
(4) cardiopulmonary resuscitation
(5) physical exertion
(6) air in other compartments (pneumothorax, pneumopericardium, pneumocephalus)
In many cases it is asymptomatic and found incidentally on imaging studies. It can cause:
(1) pain or discomfort
(2) sensory symptoms
(3) motor deficit
Differential diagnosis:
(1) intraspinal gas (non-air) collection, including gas gangrene