Cerebrospinal fluid glucose level in CM are decreased in about 25-40% of the cases and is called hypoglycorrhachia 1).

Normal glucose levels in CSF range between 50-80 mg/dl. Hypoglycorrhachia occurs because of the metabolism of tumor cells or defective transport mechanisms. This is also seen in infective meningitis, and cytology is necessary to differentiate between the two in such cases. Initial CSF cytology is positive in 55% of the cases 2).

The glucose levels in CSF also have a prognostic value. The probability of CM is less with hyperglycorrhachia, and levels greater than 2.7 mmol/L are associated with better outcomes 3) 4).

1)
Taillibert S, Laigle-Donadey F, Chodkiewicz C, Sanson M, Hoang-Xuan K, Delattre JY. Leptomeningeal metastases from solid malignancy: a review. J Neurooncol. 2005 Oct;75(1):85-99. doi: 10.1007/s11060-004-8101-x. PMID: 16215819.
2)
Chamberlain MC, Corey-Bloom J. Leptomeningeal metastases: 111indium-DTPA CSF flow studies. Neurology. 1991 Nov;41(11):1765-9. doi: 10.1212/wnl.41.11.1765. PMID: 1944906.
3)
Bruna J, González L, Miró J, Velasco R, Gil M, Tortosa A; Neuro-Oncology Unit of the Institute of Biomedical Investigation of Bellvitge. Leptomeningeal carcinomatosis: prognostic implications of clinical and cerebrospinal fluid features. Cancer. 2009 Jan 15;115(2):381-9. doi: 10.1002/cncr.24041. PMID: 19109820.
4)
Warley F, Bonella MB, Giunta DH, Elizondo CM, Ferreyro BL. Factores asociados a presencia de células neoplásicas secundarias en el liquido cefalorraquideo de pacientescon sospecha de meningitis carcinomatosa [Associated factors with the presence of secondary neoplastic cells in the cerebrospinal fluid of patients with suspected carcinomatous meningitis]. Rev Fac Cien Med Univ Nac Cordoba. 2017;74(1):26-32. Spanish. PMID: 28379128.