Meningitis refers to inflammation of the meninges, usually due to infection. The meninges are the membranes that line the brain and spinal cord. Cerebrospinal fluid (CSF) is contained within the meninges (in the subarachnoid space).
Bacterial Meningitis
The causes of bacterial meningitis include:
- Neisseria meningitidis
- Streptococcus pneumoniae (pneumococcus)
- Haemophilus influenzae type b (Hib)
- Group B Streptococcus (GBS) (particularly in neonates, as GBS may colonise the vagina)
- Listeria monocytogenes (particularly in neonates)
Neisseria meningitidis is a Gram-negative diplococcus, meaning the bacteria are spherical and usually occur in pairs. It is known as meningococcus.
Meningococcal meningitis occurs when Neisseria meningitidis infects the meninges and the cerebrospinal fluid. Meningococcal septicaemia occurs when the bacteria invade the bloodstream. Meningococcal septicaemia causes the classic non-blanching rash (although the rash can be absent in meningococcal disease).
Viral Meningitis
The most common causes of viral meningitis are:
- Enteroviruses (e.g., coxsackievirus)
- Herpes simplex virus (HSV)
- Varicella-zoster virus (VZV)
- Parechovirus (in infants under 3 months)
Viral PCR testing can be performed on a CSF sample. Aciclovir is used to treat HSV and VZV.
Presentation
Typical symptoms of meningitis are:
- Fever
- Neck stiffness
- Vomiting
- Headache
- Photophobia
- Altered consciousness
- Seizures
In meningococcal septicaemia, children may present with a non-blanching rash. Other causes of bacterial meningitis do not usually cause the non-blanching rash.
Neonates and babies can present with non-specific signs and symptoms, such as hypotonia, poor feeding, lethargy, hypothermia and a bulging fontanelle.
There are two special tests you can perform to look for meningeal irritation:
- Kernig’s test
- Brudzinski’s test
Kernig’s test involves lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee while keeping the hip flexed at 90 degrees. This creates a slight stretch in the meninges. In meningitis, spinal pain or resistance to movement may occur.
Brudzinski’s test involves lying the patient flat on their back and gently lifting their head and neck off the bed, flexing their chin to their chest. In meningitis, this causes the patient to flex their hips and knees involuntarily.
Lumbar Puncture
A lumbar puncture involves inserting a needle into the lower back to collect a sample of cerebrospinal fluid (CSF).
Contraindications to performing a lumbar puncture include:
- Raised intracranial pressure
- Focal neurological signs
- Shock
- Bleeding disorders (e.g., disseminated intravascular coagulopathy, thrombocytopenia or anticoagulation)
The spinal cord ends at the L1-L2 vertebral level. The needle is usually inserted into the L3-L4 or L4-L5 intervertebral space. Samples are sent for bacterial culture, viral PCR, cell count, protein and glucose. A blood glucose sample is sent at the same time for comparison to the CSF sample. The samples are sent immediately.
| Cerebrospinal Fluid | Bacterial | Viral |
| Appearance | Cloudy | Clear |
| Protein | High | Mildly raised or normal |
| Glucose | Low | Normal |
| White Cell Count | High (neutrophils) | High (lymphocytes) |
| Culture | Bacteria | Negative |
TOM TIP: Think about what will happen to bacteria or viruses living in the CSF rather than rote-learning the results. Bacteria swimming in the CSF will release proteins and consume glucose. Viruses may release a small amount of protein and do not consume glucose. The immune system releases more neutrophils in response to bacteria and more lymphocytes in response to viruses.
Management of Bacterial Meningitis
Bacterial meningitis is a medical emergency and should be treated immediately.
Patients seen in the primary care setting with suspected bacterial meningitis or meningococcal disease are given an urgent dose of benzylpenicillin (IM/IV) or ceftriaxone (IM) while awaiting transfer to hospital (it should not delay transfer). Where there is a true penicillin allergy, transfer should be the priority rather than other antibiotics.
Ideally, blood cultures and a lumbar puncture should be performed before starting antibiotics. However, antibiotics should not be delayed if the patient is acutely unwell.
Blood tests should include a meningococcal PCR if meningococcus is suspected. This tests for meningococcal DNA. It can give results faster than blood cultures (depending on local services) and will still be positive after the bacteria have been treated with antibiotics.
Follow the local guidelines and microbiology advice when prescribing antibiotics. The typical first-line choice is:
- Ceftriaxone
- Cefotaxime plus amoxicillin in neonates (amoxicillin is added to cover Listeria)
Aciclovir is added if viral meningitis or encephalitis caused by HSV or VZV is suspected.
Vancomycin should be added if there is a risk of penicillin-resistant pneumococcal infection (e.g., recent foreign travel or prolonged antibiotic exposure).
Steroids (e.g., dexamethasone) are also used in bacterial meningitis to reduce the frequency and severity of hearing loss and neurological complications.
Bacterial meningitis and meningococcal infection are notifiable diseases to the UK Health Security Agency.
Post-Exposure Prophylaxis
Significant exposure to meningococcal infection puts contacts at risk. This risk is highest with close, prolonged contact within 7 days of the onset of illness.
Post-exposure prophylaxis is guided by the local health protection team. The usual choice is a single dose of ciprofloxacin given as soon as possible, ideally within 24 hours of diagnosis.
Complications
- Hearing loss (a key complication)
- Seizures and epilepsy
- Cognitive impairment and learning disability
- Memory loss
- Focal neurological deficits, such as limb weakness or spasticity
Last updated May 2026
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