Back to the scanner: expected and unexpected imaging findings following spinal puncture and access.

Spinal canal procedures to withdraw fluid or introduce drugs are common minimally invasive techniques after which patients may experience new symptoms causing presentation to the emergency department. CT or MR imaging as part of the diagnostic workup may reveal expected or unexpected findings which may explain these symptoms. Small foci of gas within the spinal canal or intracranial compartment are common but are usually self-limited. Postlumbar puncture headache, presumed to be due to intracranial hypotension, may manifest on brain MR as dural thickening and low-lying cerebellar tonsils. Treatment with a blood patch is sometimes required for persistent symptoms. Spinal subarachnoid hemorrhage may be a devastating complication of dural puncture and may result in pain and paraplegia. In this review, technical details of these procedures are described and examples of common and uncommon postprocedure appearances on imaging are presented.