Meningitis

Definition

Meningitis is an inflammation of the protective membranes (meninges) covering the brain and spinal cord. It can be caused by bacterial, viral, fungal, or parasitic infections. Bacterial meningitis is a medical emergency that requires immediate treatment to prevent serious complications and death.

Aetiology

Meningitis can be caused by various pathogens:

Bacterial: Common pathogens include Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae type b (Hib).
Viral: Often caused by enteroviruses, herpes simplex virus, and varicella-zoster virus.
Fungal: Caused by fungi such as Cryptococcus and Histoplasma.
Parasitic: Caused by parasites such as Naegleria fowleri.

Pathophysiology

In bacterial meningitis, pathogens invade the bloodstream and cross the blood-brain barrier, leading to inflammation of the meninges. This inflammation causes increased intracranial pressure and can result in brain damage, neurological deficits, and death if not treated promptly.

Risk factors

Age: Infants and young children are at higher risk.
Community settings: College dormitories, military barracks, and other crowded places.
Immunocompromised individuals: Those with weakened immune systems.
Travel: Traveling to areas with high incidence of meningitis.
Previous infections or injuries: Sinus infections, otitis media, or head trauma.

Signs and Symptoms

Sudden onset of fever
Severe headache
Stiff neck
Nausea and vomiting
Photophobia (sensitivity to light)
Altered mental status (confusion)
Rash (in meningococcal meningitis)

Red Flags

Rapid progression of symptoms
Seizures
Severe headache with fever
Altered consciousness
Neurological deficits

Investigations

Clinical history and physical examination, focusing on meningeal signs (e.g., Kernig's sign, Brudzinski's sign)
Blood cultures to identify the causative pathogen
Lumbar puncture for cerebrospinal fluid (CSF) analysis, including cell count, glucose, protein, and culture
Polymerase chain reaction (PCR) testing for viral pathogens
Imaging studies (CT or MRI) if there are focal neurological signs or to rule out contraindications to lumbar puncture

Management

Primary Care Management:

Immediate referral to emergency services for suspected meningitis
Administration of empirical antibiotics if there is a delay in transfer to the hospital
Supportive care, including stabilisation of airway, breathing, and circulation

Hospital Management:

Empirical antibiotic therapy based on age and risk factors (e.g., ceftriaxone or cefotaxime)
Adjust antibiotics based on culture and sensitivity results
Dexamethasone to reduce inflammation and neurological complications in bacterial meningitis
Management of complications such as increased intracranial pressure and seizures
Supportive care, including fluids, electrolytes, and monitoring in an intensive care setting if necessary

Example Management for Meningitis:

A patient presenting with signs and symptoms of meningitis should receive empirical antibiotics (e.g., ceftriaxone 2 g IV every 12 hours) immediately after blood cultures and lumbar puncture are performed. If bacterial meningitis is confirmed, the antibiotic regimen should be adjusted according to the sensitivity profile of the identified pathogen. Dexamethasone 0.15 mg/kg IV every 6 hours should be administered for 4 days to reduce inflammation and prevent neurological complications. Supportive care, including intravenous fluids and monitoring of vital signs, is crucial.

Images:

Kernig's Sign and Brudzinski's Sign :

References:

NICE. (2024). Meningitis (bacterial) and meningococcal disease: recognition, diagnosis, and management. Retrieved from https://www.nice.org.uk/guidance/ng240
NICE. (2023). Meningitis - bacterial meningitis and meningococcal disease. Retrieved from https://cks.nice.org.uk/topics/meningitis-bacterial-meningitis-meningococcal-disease/
NHS. (2023). Meningitis. Retrieved from https://www.nhs.uk/conditions/meningitis/
Wahba M, Bell D, Skalina T, et al. Brudzinski sign (meningism). Reference article, Radiopaedia.org. Accessed on 27 May 2024. https://radiopaedia.org/articles/7061
MedlinePlus. Brudzinski's sign of meningitis. Updated 4 Dec 2022. Retrieved from https://medlineplus.gov/ency/imagepages/19069.htm
Ropper, A. H., & Samuels, M. A. (2019). Adams and Victor's Principles of Neurology. 11th ed. McGraw-Hill Education.
O'Sullivan, S. B., & Schmitz, T. J. (2016). Physical Rehabilitation. 6th ed. F.A. Davis Company.