LETTERS TO THE EDITOR

C1-C2 fluid collection on MRI myelography in patients with spontaneous intracranial hypotension Dear Sir I have read with interest the paper of Y-F Wang et al. on ‘Spontaneous intracranial hypo-tension with isolated cortical vein thrombosis and subarachnoid haemorrhage ’ (1). In this paper the authors report that magnetic resonance imaging (MRI) myelography showed cerebrospinal fluid (CSF) leakage at the C1-C2 retrospinal region (fig. 3a) and along the C5-C6 nerve roots (fig. 3b,c). I believe that the spinal MRI has been misinter-preted, because the retrospinal C1-C2 fluid collec-tion is a false localizing sign and not the actual site of the CSF leak. In fact, in the literature it is reported that, in spontaneous intracranial hypotension patients, some undemonstrated CSF leakage sites drain CSF into a potential epidural space; then the fluid flows along this space as a ‘gutter ’ and arrives at the high cervical region. The CSF then leaks out through the C1-C2 space to the extraspinal region (2). Furthermore, 50 % of patients with post-lumbar puncture headache also have extraspinal fluid collections in the C1-C2 region (3). Therefore, in the case described it is likely that the actual CSF leak site is the one at the C5-C5 spinal level