 The test should therefore be carried out only by experienced physicians (usually neurosurgeons or neuroradiologists).An alternative route that may be used by neurosurgeons and neuroradiologists is lateral to C-1 with penetration through the large C-1 intervertebral hiatus.The cisternal tap may be used in myelography when the upper margin of a spinal block needs to be defined; however, magnetic resonance imaging (MRI) has become the procedure of choice for defining the upper and lower limits of spinal cord or spinal cord-compressing lesions.