[Incidence of extra-arachnoid discharge following lumbar puncture].

Dimer-X is considered a good contrast medium for lumbar myelography. Its physical properties guarantee a homogeneous mixture with cerebrospinal fluid, with the result that postpunctural fluid leakage is easy to detect. One hundred Dimer-X lumbar myelographies were performed with two different spinal needles, a short beveled needle of 1.2 mm outer diameter and a special beveled "Quincke" needle of 0.7 mm outer diameter. Postpunctural fluid leakage is observed in 32% of the cases with the former and in only 12% with the latter. False-route injections occurred in 5% of the cases. Epidural leakage is the most frequent and can be detected by its "Christmas tree" appearance on antero-posterior X-ray. Subdural leakage is represented by a "railroad track" appearance on a lateral view. The leakage is observed more frequently in patients with normal myelogram (28%) than in patients with a herniated lumbar disc (18%).