Blood to cerebrospinal fluid human chorionic gonadotropin-beta ratios in intracranial germ cell tumors.

Levels of human chorionic gonadotropin-beta (HCG-beta) are elevated in up to 43% of patients with intracranial germ cell tumors (GCTs) and are useful in the diagnosis of these tumors and the follow up of such patients. The ratio of blood HCG-beta to lumbar cerebrospinal fluid (CSF) HCG-beta in these patients at presentation has not been defined. Twenty-two patients with intracranial GCTs have been treated at St. Bartholomew's Hospital over the past 15 years. Two (17%) of 12 germinomas and seven (70%) of 10 nongerminomatous GCTs had elevated blood HCG-beta at presentation. Four cases of pineal region GCTs (one of 12 germinomas and three of 10 nongerminomatous GCTs) had paired, elevated, blood and lumbar CSF HCG-beta levels. The mean blood to CSF ratio was 1:10 (range 1.7-18.4), which is substantially lower than the ratio of 286:1 reported in systemic GCTs. The authors confirm the finding of a previous single report showing that ventricular CSF HCG-beta sampling via an accessible ventriculoperitoneal shunt reservoir may give a spuriously negative result, and they discuss the pathophysiology of the blood-brain barrier in the pineal region and the implications of the intrathecal administration of chemotherapy.