Arachnoid cysts do not contain cerebrospinal fluid: A comparative chemical analysis of arachnoid cyst fluid and cerebrospinal fluid in adults

Abstract

BackgroundArachnoid cyst (AC) fluid has not previously been compared with cerebrospinal fluid (CSF) from the same patient. ACs are commonly referred to as containing "CSF-like fluid". The objective of this study was to characterize AC fluid by clinical chemistry and to compare AC fluid to CSF drawn from the same patient. Such comparative analysis can shed further light on the mechanisms for filling and sustaining of ACs.MethodsCyst fluid from 15 adult patients with unilateral temporal AC (9 female, 6 male, age 22-77y) was compared with CSF from the same patients by clinical chemical analysis.ResultsAC fluid and CSF had the same osmolarity. There were no significant differences in the concentrations of sodium, potassium, chloride, calcium, magnesium or glucose. We found significant elevated concentration of phosphate in AC fluid (0.39 versus 0.35 mmol/L in CSF; p = 0.02), and significantly reduced concentrations of total protein (0.30 versus 0.41 g/L; p = 0.004), of ferritin (7.8 versus 25.5 ug/L; p = 0.001) and of lactate dehydrogenase (17.9 versus 35.6 U/L; p = 0.002) in AC fluid relative to CSF.ConclusionsAC fluid is not identical to CSF. The differential composition of AC fluid relative to CSF supports secretion or active transport as the mechanism underlying cyst filling. Oncotic pressure gradients or slit-valves as mechanisms for generating fluid in temporal ACs are not supported by these results.

Quantitative proteomics comparison of arachnoid cyst fluid and cerebrospinal fluid collected perioperatively from arachnoid cyst patients

“…In addition, they found that some cysts had elevated protein levels in their fluid, relative to reference values. In a previous study on AC fluid and CSF from the same patient population as the current study, Berle et al [4] found AC fluid and CSF to be similar in electrolyte content, except for an increased phosphate content in cyst fluid. The following components were reduced in AC fluid compared with CSF: 1) the total protein amount 2) lactate dehydrogenase and ferritin.…”

“…The methods for sample collection and handling protocol as well as the laboratory work-up used in this study have previously been described in detail [4,17]. Briefly, AC fluid was collected during elective surgery for AC (craniotomy with fenestration and extirpation of the cyst) by puncturing the dura with a 23G, 25 mm long syringe needle using an Optidynamic® spinal fluid manometer (Mediplast AB, Malmo, Sweden) as siphon, through a burr hole before the craniotomy and opening of the dura.…”

Endoscopic fenestration of middle cranial fossa arachnoid cysts: Does size matter?

“…However, Berle et al compared the chemical composition of CSF and arachnoid cyst fluid from the same patient in a series of 15 patients undergoing surgery for unilateral MCF arachnoid cysts. 24 They found that arachnoid cyst fluid had significantly lower levels of protein compared to CSF, which lends support to a secretory theory of fluid accumulation.…”

Bilateral Retrocerebellar Arachnoid Cysts Exerting Mass Effect and Associated With Cerebellar Tonsillar Ectopia in an Otherwise Healthy Adult

“…3) As our patient was treated with minimally invasive burrhole drainage, no CSF was available to provide comparison, but the protein level of the cyst contents was 0.27 g/l, at the low end of the normal range for CSF, and consistent with AC. The small number of red cells present was likely related to surgery.…”