Xanthochromia

Xanthochromia, from the Greek xanthos (ξανθός) 'yellow' and chroma (χρώμα) 'colour', is the yellowish appearance of cerebrospinal fluid that occurs several hours after bleeding into the subarachnoid space caused by certain medical conditions, most commonly subarachnoid hemorrhage. Its presence can be determined by either spectrophotometry (measuring the absorption of particular wavelengths of light) or simple visual examination. It is unclear which method is superior. Xanthochromia, from the Greek xanthos (ξανθός) 'yellow' and chroma (χρώμα) 'colour', is the yellowish appearance of cerebrospinal fluid that occurs several hours after bleeding into the subarachnoid space caused by certain medical conditions, most commonly subarachnoid hemorrhage. Its presence can be determined by either spectrophotometry (measuring the absorption of particular wavelengths of light) or simple visual examination. It is unclear which method is superior. Cerebrospinal fluid, which fills the subarachnoid space between the arachnoid membrane and the pia mater surrounding the brain, is normally clear and colorless. When there has been bleeding into the subarachnoid space, the initial appearance of the cerebrospinal fluid can range from barely tinged with blood to frankly bloody, depending on the extent of bleeding. Within several hours, the red blood cells in the cerebrospinal fluid are destroyed, releasing their oxygen-carrying molecule heme, which is then metabolized by enzymes to bilirubin, a yellow pigment. The most common cause for bleeding into the subarachnoid space is a subarachnoid hemorrhage from a ruptured cerebral aneurysm. The most frequently employed initial test for subarachnoid hemorrhage is a computed tomography scan of the head, but it detects only 98% of cases in the first 12 hours after the onset of symptoms, and becomes less useful afterwards. Therefore, a lumbar puncture ('spinal tap') is recommended to obtain cerebrospinal fluid if someone has symptoms of a subarachnoid hemorrhage (e.g., a thunderclap headache, vomiting, dizziness, new-onset seizures, confusion, a decreased level of consciousness or coma, neck stiffness or other signs of meningismus, and signs of sudden elevated intracranial pressure), but no blood is visible on the CT scan. According to one article, a spinal tap is not necessary if no blood is seen on a CT scan done using a third generation scanner within six hours of the onset of the symptoms. However, this is not standard of care.