14th June 2023

Meningitis

Bacterial meningitis

Meningitis is the inflammation of leptomeninges (arachnoid & pia matter) including subarachnoid space. Bacterial meningitis indicates life-threatening inflammation of the meninges caused by a bacterial pathogen.

Aetiology

Common organisms implicated in bacterial meningitis vary with age:

Presentation

Bacterial meningitis may present with the classic triad of fever, headache, and neck stiffness. There may also be more nonspecific symptoms of fever, nausea, vomiting, lethargy, irritability, headache, muscle ache or joint pain.

Symptoms and signs which can be more specific to meningitis include neck stiffness, altered mental state (confusion, drowsiness, impaired consciousness) or seizures, non-blanching rash (petechial or purpuric), back rigidity, photophobia, Kernig’s sign (patient unable to fully extend at the knee when hip is flexed), Brudzinski’s sign (patient’s knees and hips flex when neck is flexed), focal neurological deficit, e.g. isolated cranial nerve abnormalities (principally of cranial nerves III, IV, VI, and VII).

Pre-hospital settings

In cases of suspected bacterial meningitis with non-blanching rash (typical of meningococcal disease), intramuscular or intravenous benzylpenicillin should be given at the earliest opportunity, either in primary or secondary care. Benzylpenicillin should only be withheld in people who have a clear history of anaphylaxis after a previous first dose; history of rash following penicillin is not a contraindication. Cefotaxime may be an alternative if penicillin allergy. Chloramphenicol can be used if immediate hypersensitivity to penicillin and cephalosporins.

For suspected bacterial meningitis without non-blanching rash, patients should be transferred directly to secondary care without giving parenteral antibiotics unless urgent transfer is not possible.

Investigations

• Routine bloods, including CRP and coagulation screen
• Blood cultures
• Pneumococcal and meningococcal PCR
• Lumbar puncture for CSF analysis
• CT head if fluctuating level of consciousness or focal signs. If symptoms of raised intracranial pressure, CT head must be performed prior to performing lumbar puncture.

Cerebrospinal fluid analysis for different meningitis aetiologies:

Treatment

Empirical treatment (organism not confirmed):

Treatment (organism confirmed):

Steroids

NICE guidelines advise to start dexamethasone immediately if lumbar puncture shows any of the following:

• Purulent CSF
• CSF white cell count >1000/μL or raised white cell count with protein >1g/L
• Bacteria on gram stain.

Dexamethasone should not be started >12 hours after starting antibiotics, and high-dose dexamethasone should be avoided in meningococcal meningitis.

It is important to note that bacterial meningitis and meningococcal disease are notifiable diseases. Prophylaxis for close contacts, regardless of vaccination status, is advised for those with:

• Prolonged close contact in household setting during 7 days before the onset of illness.
• Transient close contact with case only if they have been exposed to large particle droplets/secretions from the respiratory tract.

Chemoprophylaxis for meningococcal disease should be given ideally within 24 hours of diagnosis of index case.

Chemoprophylaxis in the UK is usually with either oral ciprofloxacin, rifampicin, or IM ceftriaxone (safe in pregnancy).

Complications

Immediate complications of bacterial meningitis include septic shock, seizures, cerebral oedema, septic arthritis, and pericardial effusion.

Delayed complications can include visual impairment, hearing impairment, motor deficits, epilepsy, cognitive impairment, hydrocephalus, Waterhouse Friedrichsen syndrome and septic thrombosis of dural venous sinuses.

Tuberculous meningitis

Meningitis can be caused by infection with Mycobacterium tuberculosis. This should be particularly considered in those with higher risk, including immigration from high endemic areas, healthcare professionals, and those residing in prisons or hostels etc.

Tuberculous meningitis can present acutely, however, it mostly presents as a subacute or chronic form. Clinical features include fever, malaise, intermittent headaches, and cranial nerve palsies.

CSF analysis usually shows a high protein, low glucose and raised lymphocytes. Acid-fast bacilli may be seen and Mycobacterium tuberculosis may be grown on culture.

Treatment active tuberculous meningitis (Recommended duration is 9-12 months) 

High dose steroids can be added at the start of treatment, with gradual withdrawal recommended over 4-8 weeks.

NICE recommends treating as tuberculous meningitis in cases of direct spinal cord involvement in TB (e.g.

spinal cord tuberculoma) and also in patients with miliary TB with signs and symptoms suggestive of CNS involvement.

Viral meningitis

In the UK, viral meningitis is the most common form of meningitis. Enteroviruses account for the majority, followed by herpes simplex and varicella zoster. It remains the most common cause of aseptic meningitis (i.e. no cause found after routine CSF stains and cultures). However, aseptic meningitis can also be caused by partially treated bacterial infections, fungi, parasites, drugs, and systemic disease, e.g. SLE, sarcoidosis, and Bechet’s disease.

Clinical features include acute onset meningism (i.e. neck stiffness, headache, photophobia) and fever. CSF shows a pleocytosis that is predominantly lymphocytic.

Aetiology

Herpes simplex virus (HSV-1) tends to cause encephalitis, whilst HSV-2 commonly causes meningitis. Mollaret syndrome is frequently associated with HSV-2, which is a recurrent and benign aseptic, lymphocytic meningitis.

Enterovirus infection can be suggested by a history of contact with small children with febrile illness, viral exanthema, symptoms of pericarditis, myocarditis, conjunctivitis, or pleurodynia (chest/abdominal pain associated with other viral prodrome), and symptoms of hand-foot-mouth disease.

Mumps infection may be indicated by meningeal symptoms following the onset of parotitis or orchitis. Epstein Barr Virus and Cytomegalovirus infection can be suggested by meningitis with mononucleosis syndrome. Varicella and CMV meningitis are more common in the immune-compromised host, e.g. transplant recipients.

Treatment

Treatment of viral meningitis is usually supportive only. If CSF analysis identifies a viral cause, antibiotics and steroids should be discontinued. Early treatment with aciclovir is found to be beneficial only in herpes encephalitis but not for meningitis. Ganciclovir for CMV is reserved for severe cases with positive CMV culture or when a congenital infection or an AIDS-related infection is suspected.