Dinosaur tail sign on spinal MRI in a patient with postdural puncture headache.

Sakurai K, et al. BMJ Case Rep 2017. doi:10.1136/bcr-2017-221447 Description A 68-year-old man presented with cognitive impairment, urinary incontinence and short step gait. These symptoms, together with brain MRI finding, suggested idiopathic normal pressure hydrocephalus. After a spinal tap test to confirm the diagnosis, he suffered from postdural puncture headache. Despite an equivocal finding on spinal MR myelography (MRM), lumbosacral fat-suppressed T2-weighted image (FST2WI) clearly showed the characteristic ‘Dinosaur tail sign’ indicative of cerebrospinal fluid (CSF) leakage (figure 1). This pathognomonic sign disappeared on symptom improvement (figure 1). Spinal MRM is a radiation-free technique with excellent high-contrast resolution, making it possible to detect epidural fluid collections. Considering its non-invasiveness and high sensitivity for fluid signals, this technique should be used as the first-line examination in diagnosing CSF leakage. 3 However, it could be hard to detect subtle epidural CSF leakage on spinal MRM using a two-dimensional sequence. On the other hand, sagittal FST2WI can be a useful technique to evaluate the subtle interspinous arched hyperintensities indicative of subtle epidural CSF leakage. This case emphasises the use of ‘Dinosaur tail sign’ on lumbosacral sagittal FST2WI to reflect subtle