Meningitis Flashcards
Definition of Meningitis
Meningitis refers to the inflammation of the meninges
It can be classified into several types based on the infectious agent involved, including bacterial meningitis, viral meningitis, fungal meningitis, and others
Pathomechanism of Meningitis
Meningitis typically occurs when infectious agents gain access to the central nervous system (CNS) either through the bloodstream or by direct extension from nearby structures.
The entry of these pathogens triggers an immune response, leading to inflammation of the meninges.
The inflammation causes an increase in the permeability of the blood-brain barrier, allowing immune cells and fluid to enter the subarachnoid space and leading to further damage.
The inflammatory response can result in tissue damage, impaired cerebral blood flow, and neurological dysfunction.
Causes of Meningitis
Bacteria: Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae.
Viruses: Viral meningitis is usually caused by enteroviruses, such as coxsackieviruses and echoviruses. Other viral agents, including herpes simplex virus, varicella-zoster virus, and mumps virus.
Fungi: Fungal meningitis is less common but can occur in immunocompromised individuals. Cryptococcus neoformans is the most common fungal pathogen causing meningitis.
Other pathogens: Meningitis can also be caused by parasites (e.g., Naegleria fowleri, a rare cause of primary amebic meningoencephalitis) or non-infectious causes such as chemical irritants, drug reactions, or autoimmune conditions.
Symptoms of Meningitis
Sudden high fever
Severe headache
Stiff neck (neck stiffness)
Photophobia (sensitivity to light)
Nausea and vomiting
Altered mental status, confusion, or irritability
Seizures
Rash (in bacterial meningitis, particularly meningococcal meningitis)
Symptoms in infants: In infants, symptoms may also include poor feeding, irritability, high-pitched crying, and a bulging fontanelle (soft spot on the baby’s head).
Diagnosis of Meningitis
Lumbar puncture (spinal tap): Cerebrospinal fluid (CSF) analysis is crucial for diagnosing meningitis. It involves collecting a sample of CSF through a lumbar puncture and analyzing it for cell count, glucose levels, protein levels, and culture or PCR testing to identify the infectious agent.
Blood tests: Blood cultures are performed to identify bacteria or fungi circulating in the bloodstream. Other blood tests may help evaluate the overall inflammatory response and assess organ function.
Imaging studies: Imaging, such as a CT scan or MRI, may be performed to assess for complications, such as cerebral edema, hydrocephalus, or abscess formation.
Differential diagnosis of Meningitis
Encephalitis: Inflammation of the brain, often accompanied by similar symptoms as meningitis, but with more prominent neurological signs.
Non-infectious causes: Conditions such as subarachnoid hemorrhage, autoimmune disorders, and drug reactions can mimic some symptoms of meningitis.
Treatment of Meningitis
Antibiotics or antiviral medications: For bacterial meningitis, prompt administration of broad-spectrum antibiotics is crucial, followed by targeted antibiotics based on culture and sensitivity results. Antiviral medications may be used for viral meningitis.
Supportive care: This includes maintaining hydration, controlling fever and pain, and providing comfort measures.
Anticonvulsant medications: If seizures occur, anticonvulsant medications may be administered.
Prevention:
Vaccination: Vaccination against specific pathogens, such as Neisseria meningitidis, Haemophilus influenzae type b (Hib), and Streptococcus pneumoniae, can provide protection against bacterial meningitis.
Hand hygiene: Frequent handwashing can reduce the spread of infectious agents.
Respiratory hygiene: Covering the mouth and nose when coughing or sneezing can prevent the spread of respiratory pathogens.
Prophylactic treatment: In certain situations, such as close contacts of individuals with bacterial meningitis, prophylactic treatment with antibiotics may be recommended to prevent transmission.
Complications of Meningitis
Neurological complications: These can range from mild impairments to severe disabilities, such as cognitive deficits, hearing loss, vision problems, speech difficulties, and motor deficits.
Septicemia: Bacterial meningitis can lead to bloodstream infections (septicemia), which can be life-threatening.
Hydrocephalus: Accumulation of cerebrospinal fluid in the brain due to impaired circulation or absorption, requiring surgical intervention.
Brain abscess or subdural empyema: Collection of pus within the brain or between the brain and the meninges, requiring drainage.
Meningococcal septicemia: In severe cases of meningococcal meningitis, a fulminant bloodstream infection can occur, leading to septic shock and multi-organ failure.
