Abstract

Introduction: Meningitis is a clinical syndrome characterized by inflammation of the meninges. Meningitis is a medical, neurologica and sometimes neurosurgical emergency that requires a multidisciplinary approach. Anatomically meningitis can be divided into the inflammation of the dura (pachymeningitis), which is less common and leptomeningitis, which is more common and is defined as the inflammatiom of the arachnoid and the subarchanoid space. Examination of the cerebrospinal fluid is the cornerstone of diagnosis. Cerebrospinal fluid analysis includes the total count, differential count, protein, sugar, gram staining culture and sensitivity, AFB staining, in special cases CSF ADA and Tuberculous RNA PCR. Other laboratory tests, which may include CSF lactate, C- Reactive Protein, SGOT, glutamate level and Lactate Dehydrogenase. (LDH). Though CSF abnormalities in meningitis is well documented, only few studies have been conducted in our part of the world. This study is conducted to know the role of CSF LDH to differentiate different types of meningitis.

Materials and Methods: This was a hospital based cross sectional study. All patients with recorded clinical and biochemical evidence of meningitis (viral, bacterial, or tuberculous) admitted in a tertiary care centre in South Kerala during the period of April 2012- 2013 were included. After getting informed consent from Patients after applying inclusion and exclusion criteria, those fulfilling all the inclusion criteria were subjected to detailed evaluation, Lumbar puncture (for CSF collection and analysis of CSF) was done. According to the criteria patients were divided into four groups- Viral, bacterial, tuberculous and partially treated meningitis. CSF LDH was  measured and looked for any correlation with the diagnosis. Unpaired T test was used to compare mean LDH level in various types of meningitis. Association was checked with Chi square test.

Observations: 180 patients were included in this study, 111 were males and 69 females. Most of the patients were younger & belonged to the age group of 31-40 years in  bacterial  and viral meningitis group , whereas in tuberculous meningitis maximum number of patients were elderly ,in the age group 61-70years. Among the total 180 patients,33% were categorized as bacterial, 33% as viral, 4.44% as tuberculous and 28.88% as partially treated meningitis according to the study definitions. The average white blood cell count of the CSF among patients with bacterial meningitis was 613,tuberculous meningitis  was 656,and in viral meningitis was 101cells /mm3 .On analysis the differential count was predominantly polymorphs in bacterial whereas it was lymphocytic predominant in other groups. The average CSF protein in bacterial meningitis group was 102.4mg/dl, in viral meningitis group 33.6, tuberculous meningitis group  89.4 and in the partially treated group was 75.47mg/dl. The average CSF sugar value in bacterial meningitis was 29.5mg/dl, in viral 68.4mg/dl,in Tuberculous meningitis 23.3and in partially treated group was 43.03mg/dl. The average ADA value in bacterial meningitis group was 6.4,viral meningitis group was 4.8 whereas in tuberculous meningitis group it was 20.We  noted that the  average ADA value was maximally elevated in the tuberculous group. Among the 18 tuberculous patients, 17 had an ADA of more than 15. The average CSF LDH value was 94.1 IU/L in bacterial meningitis group, 30.2 IU/L in viral meningitis group &119.9 IU/L in tuberculous meningitis group. Out of the 72 patients who had viral meningitis in our study,18 (25%)  had JE/WEST NILE virus positivity. This high frequency of encephalitis was not observed in other studies, which indicates a high frequency of JE in our part of the world . In those tested positive for JE, the CSF LDH was significantly high. We had 52 (28.88%) patients in the partially treated meningitis group. Among this 34 had features of bacterial &6 had features of tuberculous meningitis. The CSF LDH value was significantly elevated in these two catogories. Rest of the12 patients with features suggestive of viral meningitis only had a mild elevation of LDH. The mean CSF LDH in viral meningitis & tuberculous meningitis group were 77.2 & 22.5 % respectively.

Conclusion: CSF LDH was significantly elevated in Tuberculous meningitis and bacterial meningitis. In viral meningitis, CSF LDH showed only a mild elevation. Viral meningitis with increased CSF LDH were positive for JE. Hence in Viral meningitis with high LDH should raise suspicion of encephalitis.