Meningitis - causes, symptoms, diagnosis, treatment, pathology

Summary

Meningitis is an inflammation of the leptomeninges, the two inner membranes surrounding the brain and spinal cord. It is most commonly triggered by infection, such as bacterial, viral, fungal, or parasitic pathogens. Symptoms include headaches, fever, and neck stiffness. Diagnosis involves physical exams like the Kernig’s and Brudzinski’s signs, followed by a lumbar puncture to analyze cerebrospinal fluid (CSF). Treatment depends on the cause and may include antibiotics, antivirals, or antifungals. Vaccines and prophylactic antibiotics help prevent certain types of meningitis, with prompt diagnosis and treatment crucial for recovery.

Takeaways

• 😀 Meningitis is the inflammation of the leptomeninges, the inner two protective membranes surrounding the brain and spinal cord.
• 😀 The meninges consist of three layers: the outer dura mater, the middle arachnoid mater, and the inner pia mater (leptomeninges).
• 😀 Cerebrospinal fluid (CSF) is found in the subarachnoid space between the leptomeninges, cushioning the brain and spinal cord and providing nutrients.
• 😀 The blood-brain barrier regulates the flow of substances between the blood and the brain, preventing the leakage of harmful molecules.
• 😀 Meningitis can be triggered by autoimmune diseases, adverse drug reactions, or most commonly, infections like bacteria, viruses, fungi, or parasites.
• 😀 Bacterial and viral infections are the primary causes of meningitis, with bacteria like Neisseria meningitidis and viruses like herpes simplex virus being common culprits.
• 😀 Meningitis can spread to the CSF and leptomeninges through direct spread (e.g., skull fracture) or hematogenous spread via the bloodstream.
• 😀 The body's immune response to meningitis causes an increase in white blood cells and inflammation, which can lead to raised CSF pressure and changes in glucose and protein concentrations.
• 😀 Classic meningitis symptoms include headaches, fever, and neck stiffness, along with photophobia, phonophobia, and altered mental status in some cases.
• 😀 The diagnosis of meningitis includes physical exams (e.g., Kernig's and Brudzinski's signs) and laboratory tests such as lumbar puncture to analyze CSF and PCR for specific pathogens.
• 😀 Treatment for meningitis is tailored to the underlying cause, with antibiotics, antivirals, antifungals, or antiparasitic drugs being used as appropriate, along with preventive measures like vaccination and prophylactic antibiotics.

Q & A

What does the term 'meningitis' refer to?

Meningitis refers to the inflammation of the meninges, the protective membranes surrounding the brain and spinal cord, particularly the inner two layers called the leptomeninges.

What are the three layers of the meninges, and which two are involved in meningitis?

The meninges consist of three layers: the dura mater (outer layer), the arachnoid mater (middle layer), and the pia mater (inner layer). Meningitis primarily affects the leptomeninges, which are the arachnoid and pia mater.

What is cerebrospinal fluid (CSF), and what is its role?

Cerebrospinal fluid (CSF) is a clear, watery liquid found in the subarachnoid space between the leptomeninges. It cushions the brain and spinal cord from impact, provides nutrients, and removes waste.

What is the normal composition of CSF?

Normally, CSF contains a few white blood cells (up to 5 per microliter), proteins (15-50 mg per deciliter), and glucose (45-100 mg per deciliter), which is about two-thirds of the glucose level in blood.

How is the blood-brain barrier involved in the regulation of CSF?

The blood-brain barrier, formed by tightly bound endothelial cells, regulates which molecules can enter or exit the brain and CSF. It prevents leakage and ensures only specific molecules can pass through.

What causes meningitis, and how does an infection typically spread to the CSF?

Meningitis can be triggered by infections, autoimmune diseases, or reactions to medications. Infections can spread to the CSF either through direct spread (e.g., from a skull fracture or skin infection) or hematogenous spread (via the bloodstream).

What are the differences in white blood cell counts and types in CSF across different types of meningitis?

In bacterial meningitis, the CSF contains over 100 white blood cells per microliter, primarily polymorphonuclear cells (PMNs). In viral meningitis, there are 10-1000 white blood cells, mostly lymphocytes. In fungal and tuberculous meningitis, the CSF contains 10-500 white blood cells, with lymphocytes being predominant.

What are the classic symptoms of meningitis?

The classic symptoms of meningitis are headaches, fever, and nuchal rigidity (neck stiffness). Additional symptoms may include photophobia (sensitivity to light) and phonophobia (sensitivity to loud sounds).

How is meningitis diagnosed?

Meningitis is diagnosed through a physical exam and maneuvers like the Kernig's and Brudzinski's signs, followed by a lumbar puncture to analyze CSF for white blood cells, protein, and glucose levels, and to test for specific pathogens.

What treatments are available for meningitis, and how do they differ depending on the cause?

Treatment for meningitis depends on its cause. Bacterial meningitis is treated with antibiotics and often steroids to reduce inflammation. Viral, fungal, and parasitic meningitis are treated with antivirals, antifungals, or antiparasitic drugs. Vaccines and prophylactic antibiotics can prevent certain types of meningitis.