Crystals seen on CSF microscopy in a case of suspected subarachnoid haemorrhage.Although crystals are rarely identified on cerebrospinal fluid (CSF) microscopy, their presence can be of significant diagnostic value.  We report a case of oxalate crystals seen on CSF microscopy of a 43-year-old woman. 
CSF microscopy
The same crystals were seen on microscopy of CSF collected in a fluoride oxalate container used for glucose analysis.  It transpired that excess CSF had been collected into a fluoride oxalate container. 
fluoride oxalate container