Neurology >
Meningitis
“An infection of the protective membranes that surround the brain and the spinal cord (the meninges)”
Risk Factors
- Extremes of age (<5 or >60)
- Those with a suppressed immune system (e.g. HIV, on immunosuppressants)
- Chronic kidney failure
- Diabetes Mellitus
Aetiology
- Infective
- Bacterial – e.g. Neisseria meningitides
- Viral – e.g. Mumps, enteroviruses
- Fungal – e.g. Cryptococcus neoformans)
- Non-infective (e.g. malignant meningitis)
Pathophysiology
- Microorganisms reach the meninges either by direct (e.g. ears, cranial injury) or bloodstream spread.
- Acute bacterial: pia-arachnoid congested with polymorphs, resulting in pus formation and adhesions
- Chronic infection: brain covered in exudate with meningeal tubercles
- Viral: lymphocytic inflammatory CSF reaction without pus formation, polymorphs or adhesions
- NB cerebral oedema occurs in all bacterial meningitis infections
Clinical Presentation
- Early: headache, leg pains, cold hands and feet, abnormal skin colour
- Later: Meningism (neck stiffness, photophobia, positive Kernig’s sign), decrease in GCS, seizures, petechial rash
- NB: in acute bacterial symptoms more intense and develop within minutes/hours, whereas many viral meningitides have less prominent signs
Investigations
- Bloods:
- FBC, U+Es, LFT, glucose, coagulation screen
- Blood cultures
- Serology
- Imaging:
- Chest X-Ray – looking for TB signs
- CT Chest
- Special:
- Throat swabs, and rectal swab
- Lumbar puncture: if bacterial appears turbin, polymorphs predominant cell, high cell count/mm3, glucose <1/2 plasma, >1.5g/L protein)
Management
- Minutes save lives and local policies vary
- <55yrs: cefotaxime 2g/6hr slow IV
- >55yrs: cefotaxime + ampicillin (to cover Listeria)
- Viral: Aciclovir
Complications
- Cranial nerve lesions (leading to e.g. hearing loss, blindness)
- Paralysis
- Ataxia
- Recurrent seizures
- Problems with memory and concentration