Comparative Analysis of Cerebrospinal Fluid and Synovial Fluid Electrolytes for Estimation of Time Since Death: A Cross-Sectional Autopsy Study

Tauheed Anwar, Anoop Kumar Verma, Mousami Singh, Raja Rupani, Sangeeta Kumari4, Shiuli, Md. Kaleem Ahmad
Author(s)
1Senior Resident, Department of Forensic Medicine & Toxicology, King George’s Medical University, Lucknow, Uttar Pradesh, India. .2Professor & Head, Department of Forensic Medicine & Toxicology, King George’s Medical University, Lucknow, Uttar Pradesh, India 3Professor, Department of Forensic Medicine & Toxicology, King George’s Medical University, Lucknow, Uttar Pradesh, India. 4Additional Professor, Department of Forensic Medicine & Toxicology, King George’s Medical University, Lucknow, Uttar Pradesh, India. 5Professor, Department of Biochemistry, King George’s Medical University, Lucknow, Uttar Pradesh, India.

Abstract

Background: Accurate estimation of the postmortem interval (PMI) remains a major challenge in forensic practice, as conventional methods are influenced by environmental and individual factors. Thanatochemistry provides a more objective approach through predictable biochemical changes after death. Synovial fluid (SF) and cerebrospinal fluid (CSF), owing to their relative anatomical isolation, may serve as alternative matrices to vitreous humour. Postmortem disruption of cellular membranes causes measurable alterations in sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺). Comparative evidence regarding these electrolytes in SF and CSF remains limited. Material and Methods: This was a cross-sectional comparative study. A total of 100 medico-legal autopsy cases with known time since death (up to 24 hours) were included in this prospective study. CSF was collected via lumbar puncture, and SF was aspirated from the knee joint. Electrolyte levels (Na⁺, K⁺, Ca²⁺) were measured using ion-selective electrode methods. Cases were grouped based on PMI: 0–6, 7–12, 13–18, and 19–24 hours. Statistical analysis was performed using Jamovi 2.3.37 with descriptive and inferential statistics, applying Pearson correlation and linear regression models to identify relationships. Results: This study evaluated postmortem sodium, potassium, and calcium concentrations in cerebrospinal fluid (CSF) and synovial fluid (SF) during the first 24 hours after death. SF potassium showed the strongest correlation with exact time since death (TSD; r=0.467), followed by CSF potassium (r=0.373), whereas CSF calcium declined with increasing TSD (r=−0.274). The SF electrolyte model explained more variation than the CSF model, while the combined six-electrolyte model provided the best fit (R²=0.414; adjusted R²=0.376). Conclusion: Synovial-fluid potassium showed the strongest association with time since death and performed better than cerebrospinal-fluid potassium during the first 24 hours. Combining electrolytes from both fluids improved predictive performance, but the remaining error limits standalone forensic application. These estimates should therefore be interpreted alongside conventional postmortem findings, with external validation required before routine use.

 

Keywords: Autopsy, Cerebrospinal fluid, Synovial fluid, Electrolytes, Postmortem Interval.

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