Bilirubin compounds in the CSF

Abstract

The occurrence of different bilirubin compounds in the CSF has been investigated spectrophotometrically. From a pool of about 500 spectrophotometric CSF records 68 cases were selected in which the bilirubin peak maxima of the CSF could be accurately determined. The spectrophotometric patterns were related to the diagnosis. The haemorrhagic and non-haemorrhagic parts of the CSF-bilirubin were estimated according to an equation described earlier. The investigation indicates the existence of two main forms of CSF bilirubin: “short wavelength” bilirubin compounds (“SB” compounds) with the spectrophotometric peak maxima in the range 425–430 nm, and “long wavelength” bilirubin compounds (“LB” compounds) in the range 450–460 nm. According to the findings in some CSF samples which were re-examined, the SB-compounds seem to be sensitive to storage. It is suggested, in accordance with recent investigations on serum bilirubin, that the SB-compounds may be largely bound as glucuronide conjugates, while the LB-compounds are probably “free” bilirubin, more directly attached to CSF albumin. In normal CSF concentrated by ultrafiltration, both SB and LB-compounds are probably present. In 1 of 6 CSF-concentrates examined a peak maximum at 425 nm was found, which may indicate that SB-compounds constitute an important part of normal CSF-bilirubin. SB-compounds were found to constitute the greater part of the CSF bilirubin in adult subjects with: (1) CSF-bilirubin estimated to be of non-haemorrhagic origin and due to presumed blood-CSF “barrier damage” ( e.g. multiple sclerosis, chronic myelopathy, polyradiculitis) and/or obstructive jaundice, (2) CSF-bilirubin estimated to be of mostly haemorrhagic origin due to “old” subarachnoid haemorrhage occurring 3–4 weeks previously. LB-compounds were found as CSF-bilirubin of haemorrhagic origin in recent CNS-haemorrhages and as non-haemorrhagic CSF-bilirubin in neonatal hyperbilirubinaemia. The divergence between the mean values for peak maxima for recent haemorrhages in adults, 450.5 ± 2.3 (SD), and newborns, 451 ± 2 (SD), is not statistically significant. However, the peak maximum value in neonatal jaundice, 457.0 ± 4.7 (SD), may indicate some difference between the neonatal CSF bilirubin and that induced by haemorrhage.