Neurology: Infections

Question 1

What is Meningitis?

Answer 1

Serious Infection of the meninges

• Microorganisms reach the meninges either by direct extension from ears, nasopharynx, cranial injury or congenital meningeal defect or bloodstream spread.
• Bacterial meningitis is fatal unless treated. Immunocompromised patients are at risk of infection with unusual organisms

Question 2

What are some non-infective causes of Meningitis?

Answer 2

• Malignant meningitis
• Intrathecal drugs
• Blood following subarachnoid haemorrhage

Question 3

What are microorganisms causing Meningitis/Encephalitis?

Answer 3

Bacteria

• Neisseria meningitidis
• Streptococcus pneumoniae
• Staphylococcus aureus
• Streptococcus group B
• Listeria monocytogenes
• Gram-negative bacilli (Escherichia coli)
• Mycobacterium tuberculosis
• Treponema pallidum

Viruses

• Enterovirus (ECHO, Coxsackie)
• Mumps
• Herpes simplex
• HIV
• Epstein-Barr

Fungi

• Cryptococcus neoformans
• Candida albicans
• Coccidioides immitis
• Histoplasma capsulatum
• Blastomyces dermatitidis

Question 4

What are some clinical clues for organisms in meningitis/encephalitis?

Answer 4

• Meningococcal infection = Petechial rash, fever, headache, neck stiffness
• Pneumococcal infection = Skull fracture, Ear disease, Congenital CNS lesion
• HIV with opportunistic infection = Immunocompromised patient’s
• Enterovirus infection = Rash or pleuritic pain
• Malaria = International travel
• Leptospirosis​ = Occupational (work in drains, canals, polluted water, recreational swimming). Clinically presents with myalgia, conjunctivitis, jaundice

Question 5

What is meningitic syndrome?

Answer 5

Meningitic syndrome

• Triad: Headache, Neck Stiffness and Fever
• Can also have Photophobia and vomiting

Question 6

How do bacterial and viral meningitis present?

Answer 6

Acute bacterial infection:

• Intense malaise, fever, rigors, severe headache, photophobia, and vomiting developing within hours or minutes
• Patient is irritable and often prefers to lie still
• Neck stiffness and positive Kernig’s sign usually appears within hours

Viral infections:

• Less severe meningitic signs
• Almost always benign, self-limiting condition lasting 4-10 days.

Question 7

How is meningococcal infection managed?

Answer 7

Medical Management

• Intravenous Antibiotics
  
  • Third-generation cephalosporin e.g. cefotaxime as empirical therapy
  • Switch to benzylpenicillin if sensitivity confirmed
• Dexamethasone 0.6mg/kg I.V with or before first antibiotic dose

Question 8

What are the investigations for meningococcal meningitis infection?

Answer 8

• Blood tests including blood cultures
  
  • CSF stains demonstrate organism
  • Ziehl-Neelsen stain demonstrates acid-fast bacilli
  • Indian ink stains fungi
  • PCR for meningococci and viruses
• Monitoring for septic shock
• Lumbar puncture unnecessary

Question 9

How should prophylaxis for meningitis be administered?

Answer 9

• Meningococcal infection should be notified to public health authorities and advice sought on immunization and prophylaxis of contacts.
• Chemoprophylaxis with rifampicin or ciprofloxacin offered to all close contacts
• MenC vaccine given in the UK and MenB, for infant immunization and use in outbreaks.
• Pneumococcal conjugated vaccine is now given to infants in many countries and pneumococcal polysaccharide vaccine is offered to older adults and those with, for example, immunodeficiency or splenectomy
• HiB (haemophilus influenzae) vaccine is given routinely in childhood in the UK and many other countries, virtually eliminating common cause of fatal meningitis

Question 10

What are symptoms of tuberculous meningitis?

Answer 10

• TB meningitis insidious onset is common
• Mild headache and constitutional upset
• Cranial nerve lesions
• Papilledema is common and secondary optic nerve damage
• Sudden deterioration secondary: Hydrocephalus, Vasculitis, Cerebral infarction

Question 11

What investigations for Tuberculous Meningitis?

Answer 11

• Brain imaging, usually with MRI, may show meningeal enhancement, hydrocephalus and tuberculomas although it may remain normal
• Sparse tuberculous organism cannot be seen on staining and PCR testing should be performed although result may be negative
• May take some weeks before results are confirmatory

Question 12

What is the management for Tuberculous Meningitis?

Answer 12

TB specialist

• Anti-TB drugs
  
  • Rifampicin, Isoniazid, Pyrazinamide, Ethambutol
• Prednisolone recommended

Question 13

What can causes Pleocytosis (cells in sterile CSF)?

Answer 13

• Partially treated bacterial meningitis
• Viral meningitis
• Tuberculous or fungal meningitis
• Intracranial abscess
• Neoplastic meningitis
• Parameningeal foci e.g. paranasal sinus
• Syphilis
• Cerebral venous thrombosis
• Cerebral malaria
• Cerebral infarction
• Following subarachnoid haemorrhage
• Encephalitis, including HIV
• Rarities, e.g. cerebral malaria, sarcoidosis, Behçet syndrome, Lyme disease, endocarditis, cerebral vasculitis