Etiology, Pathogenesis, Clinical Presentation, and Laboratory Diagnosis of Meningitis

Introduction

Meningitis is a serious condition characterized by inflammation of the meninges, the protective membranes covering the brain and spinal cord. It can be caused by various pathogens, including bacteria, viruses, fungi, and parasites.

Etiology of Meningitis

Bacterial Causes

• Streptococcus pneumoniae - Leading cause of bacterial meningitis in adults.
• Neisseria meningitidis - Common in adolescents and young adults, often spread in crowded settings.
• Haemophilus influenzae - Less common due to vaccinations.
• Listeria monocytogenes - Affects newborns, elderly, and immunocompromised individuals.

Viral Causes

• Enteroviruses - The most common viral cause.
• Herpes simplex virus - Can lead to severe encephalitis.
• Varicella-zoster virus - May complicate chickenpox or shingles.
• Mumps virus - Can lead to viral meningitis.

Fungal Causes

• Cryptococcus neoformans - Affects immunocompromised individuals, such as those with HIV/AIDS.
• Histoplasma capsulatum - Can lead to chronic meningitis.

Parasitic Causes

• Naegleria fowleri - Rare but deadly, found in warm freshwater.
• Angiostrongylus cantonensis - Causes eosinophilic meningitis.

Pathogenesis

Pathogens enter the bloodstream and breach the blood-brain barrier, triggering an inflammatory response. This leads to increased intracranial pressure, neuronal damage, and potential complications.

Clinical Presentation

• Fever and chills
• Severe headache
• Nuchal rigidity (stiff neck)
• Altered mental status (confusion, lethargy)
• Photophobia (sensitivity to light)
• Nausea and vomiting
• Seizures

Laboratory Diagnosis

Diagnosis is confirmed through cerebrospinal fluid (CSF) analysis obtained via lumbar puncture.

• CSF cell count - Elevated white blood cells suggest infection.
• Glucose levels - Reduced in bacterial meningitis.
• Protein concentration - Increased in bacterial and fungal meningitis.
• Gram stain and culture - Identify bacterial pathogens.
• Polymerase Chain Reaction (PCR) - Useful for viral detection.

Conclusion

Meningitis is a life-threatening condition that requires prompt diagnosis and treatment. Understanding its etiology, pathogenesis, and clinical presentation helps healthcare professionals intervene effectively.