CNS Infections - Viral Encephalitis and Bacterial Meningitis - Differential Diagnosis Framework Viral Encephalitis: MCC: Enteroviruses (e.g., coxsackievirus or Echovirus). Herpesviruses (MCC: HSV 1): • Herpes simplex virus 1 and 2 • Varicella-zoster virus • CMV • EBV • HHV6 Others: • Adenovirus, • Lymphocytic choriomeningitis virus (LCMV), influenza, parainfluenza, and mumps. • Arboviruses: - West Nile virus (WNV), Zika, chikungunya, dengue, LaCrosse, Saint Louise encephalitis, eastern equine encephalitis virus, - Jamestown Canyon virus, Snowshoe Hare virus - Powassan, louping ill virus and Coltivirus Symptoms: • Headache • Fever • Nuchal rigidity • Photophobia • Nausea, vomiting • Myalgia, pharyngitis • Maculopapular rash • Cough • Changes in alertness, confusion, or hallucinations CSF Analysis: • Lymphocytic pleocytosis • A mildly elevated protein level (< 1g/L) • Mildly decreased/Normal glucose level, • Normal opening pressure Lyme Meningoencephalitis: • 2 to 10 weeks after erythema migrans develops. • Common clinical features include - Headache, photophobia, nausea, - History of erythema migrans, - Tick bite in an endemic area, - Facial paralysis, which can be unilateral or bilateral. Treponema Pallidum Meningitis: • Headache and meningismus are common • CSF usually shows a lymphocytic pleocytosis with an elevated protein level. • In tertiary syphilis, neurosyphilis can be asymptomatic or symptomatic. • Symptomatic neurosyphilis can present with primarily meningovascular (stroke presentation) or parenchymatous (tabes dorsalis, general paresis) features Bacterial Meningitis: MCC: • Streptococcus pneumoniae, • Neisseria meningitidis (40%) • Listeria monocytogenes • Haemophilus influenzae Symptoms: • Acute meningeal signs (fever, nuchal rigidity) • Altered mental status. CSF Analysis: • Neutrophilic predominance • Protein level 100-500 mg/dL • Glucose level: <40 mg/dL • Normal opening pressure • Gram stain: Positive in 60%-90% • Culture: Positive in 70%-85% • Negative CSF Gram stain: Previous antibiotics, L. Monocytogenes or gram negative bacilli (< 50%) • S. pneumoniae antigen detection in the CSF has a 99% sensitivity and specificity Leptospiral Meningitis - Develops in the immune or second phase of the illness: • Uveitis • Rash • Conjunctival suffusion • Lymphadenopathy • Hepatosplenomegaly • The CSF formula resembles enteroviral meningitis, and the diagnosis is established by CSF or urine culture or by serology. CSF Lactate: Good indicator to differentiate bacterial from viral meningitis • In Bacterial meningitis • CSF-lactate ≥ 4.2 mmol/l is regarded as a strong indicator of a non-viral meningitis with a diagnostic sensitivity and specificity of up to 93-99% and 88-94%. by Dr. Kushal Vaishnani @k_vaishnani and Ravi Singh @rav7ks #CNS #Infections #differential #diagnosis #neurology #meningitis #encephalitis
