CSF flow study in Chiari Malformation-Teaching Points

45 year lady with neck pain on routine MR suggests tonsillar ectopia of approximately 8 mm (to the level of body of C2) with phase contrast CSF flow study suggesting subtly reduced signal intensity and flow pattern of the CSF column in the posterior subarachnoid space, possibly representing benefit from surgical decompression (could be deferred for periodic reviews in view of no significant neurological deficit).

Teaching points by Dr MGK Murthy, Dr Krishna Mohan, Dr Sumer Sethi, Mr Narasimhulu:

-      Chiari-I exhibits downward displacement to the cerebellar tonsils, may bilateral ethmoid associated with syringomyelia.

-      The presence and magnitude of ectopia on MR does not correlate with the presence and the severity of signs and symptoms.

-      Upto 30% of individuals with more than 5 mm ectopia have no symptoms, whereas symptoms could exist with minimal or no ectopia.

-      Symptomatic chiari-I patients may benefit from surgical decompression, while patients without CSF flow abnormalities may not benefit.

-      Although quantitative assessment methods of the CSF flow at C.V.junction are reported, non quantitative visual assessment including reduced flow in the posterior subarachnoid space in phase contrast MR images are reliably used in various studies to decide decompression.

-      The technique includes transverse and sagittal phase contrast MR images with ECG gating, with plane of acquisition as dense (for transverse a plane transverse to the axis with the spinal canal immediately below the tonsillar tips) patients neck in neutral / flexed and extended positions.

-      Some of the abnormal findings of the C.V.junction CSF flow include moderate preponderance of the anterior CSF flow and reduced flow in the posterior subarachnoid space ,  hyperactive flow and  flow jets.

-      False positives include absence of posterior flow, presence of anterior flow jets. CSF flow more likely to be abnormal in flexion than other positions.