Intracranial hypotension-MRI

Case Report: 21 year old post partum headache  shows bilateral subdural hygromata (left more than right) with prominent pachymenigeal vessels with no definite cortical vein thrombus  or MRV gross abnormality , possibly represents Intracranial hypotension following accidental  dural puncture during  spinal anesthesia

Teaching points by Dr MGK Murthy, Mr Charles (MRI Technologist)

1. Accidental dural puncture during epidural insertion is identified by observing CSF flow at the hub of the epidural needle, by aspirating CSF from the epidural catheter, or by observing the response to a test dose of local anesthetic . (Absence of all these does not exclude though)

2. Theories include  epidural needle causing  partial dural breach but leaving  an intact arachnoid membrane that can tear later, leading to a total dural- arachnoid breach  OR  a tissue plug hindering the flow of CSF through the needle at the time of puncture

3 Failure to recognize  the accidental puncture  can lead to intracranial hypotension, traction on cranial nerves, subdural hematoma or hygroma  as a result of an increased leakage of interstitial fluid from engorged pachymeningeal vessels, vasodilated due to a Monroe-Kelly type response to the excessive loss of CSF from a dural leak lower in the spinal canal .

4.MRI studies of low CSF pressure states include  meningeal enhancement, intracranial vein engorgement, tonsillar sagging and pituitary hyperaemia etc 

5.Traumatic damage to the fragile venous endothelial lining due to stretching of the cerebral vessels and relative stasis of blood flow in the vasodilated cerebral vasculature contribute towards cortical venous  thrombosis, though it may not be seen  and MRV can be grossly normal 

 6. An epidural blood patch is effective  in blocking the leak  with immediate resolution of symptoms