Introduction central nervous system infection:

Nervous system —

  • Central Nervous System
  • Peripheral Nervous System


Central Nervous system –

  • Brain   — Cerebrum, Brain stem & cerebellum
  • Spinal cord

Coverings of brain – Meninges

  • Dura mater
  • Arachnoid mater
  • Pia mater


Definition of central nervous system infection:

Infection occurring in relation to the central nervous system.

Two types —

  • Generalized –Meningitis, Encephalitis & Myelitis
  • Localized —  Abscesses – Brain & S. Cord


Infections again are of two types—

  • Non-specific
  • Specific

Infection may be –

  • Bacterial
  • Viral—Herpes simplex, Herpes zoster, Jakob-Creutzfeldt disease (Mad Cow Disease)
  • Fungal –
  1. Coccidiodomycosis
  2. Blastomycosis
  3. Histplasmosis
  4. Cryptococcosis
  5. Aspergillosis
  • Parasitic-
  1. Hydatid
  2. Cesticercosis
  3. Protozoal—Malaria, Trypanosoma, Toxoplasma, E.histolytica




Fig: meningitis


Inflammation of leptomeninges.

Bacterial, Viral, Fungal.

Pyogenic, Tubercular





  • Spontaneous -Bacteriology— Strep., Enterobactericae, Listeria

Pneumo, Meningococci, H.Influ,

Antibiotics of choice – Ampicillin, Gentamicin,

Ceftriaxone, Cefotaxime

Vancomycin, Chlorampenicol


  • Post-traumatic or Post-surgical (Surgical Meningitis)-

Bacteriology— Staph. aureas, Pseudomonas, Enterobactericae



Antibiotics of choice – Flucoxacilline, Vancomycin, Ceftazidime

Route of entry—

  • Hematogenous
  • Direct—CSOM, Air sinus infection, Post-traumatic CSF leak, Penetrating injury,



  1. Clinical parameters
  2. Laboratory and imaging data


Length of treatment —   Antibiotics should be continued for at least 5 days after symptoms resolve.

Not less than 14 days according to some author.


Localized infection:

Brain abscess, Empyema, Cord abscess.



brain abscess

Fig: brain abscess


Risk factors:  

  • Pulmonary abnormalities ( Infection, A-V fistulas)
  • Congenital cyanotic heart disease
  • Bacterial endocarditis
  • Penetrating head injury
  • CSOM
  • Sinusitis
  • AIDS


Source of infection:

  • Contiguous spread – CSOM, Sinusitis, Odontogenic infection.
  • Hematogenous spread – Pulmonary, Cardiac, Dental infection, GI infection, Systemic infection.

In adult- Lung abscess(most common), Bronchiectasis and Empyema.

In children- Cong. Cyanotic heart disease esp. TOF.

  • Following penetrating trauma or Neurosurgical procedures.

Site of Abscesses:

For hematogenous spread-

  • Mostly MCA territory and on the Lt. side.
  • Pulmonary origin- usually multiple, Cardiac origin- usually solitary.
  • In patients with septic embolization, risk of cerebral abscess is elevated in areas of previous infarction or ischemia.


For contagious spread-

  • CSOM and mastoid air cells- Temporal lobe and cerebellar abscess.
  • Nasal Sinusitis- Frontal lobe abscess.
  • Sphenoid sinusitis- Least common but high incidence of intracranial complication due to venous extension to cavernous sinus.
  • Odontogenic- Rare




  • Strptococcus– most frequent, 33-50% anaerobic and microaerophilic.
  • Staph.aureas
  • Bacteroids
  • Enterobactericae
  • Fungal –  Common in transplant patients  Aspergillus fumigatus
  • Toxoplasma, Nocardia – common in immunocompromised patients.




  • Features of raised ICP
  • Focal neurological sign
  • Features of cause of the lesion
  • Gen. features of infection.



Blood work


  • CT scan- Depends upon the stage of the disease.

Usually Iso to hypodense lesion, with contrast ring enhancement.

  • MRI – Iso to hypointense in TIWI, hyperintense on T2WI, ring enhancement in gadolinium enhancement.
  • MRS
ct scan of brain abscess

Fig: ct scan of brain abscess




Medical Treatment:


  • If treatment can be started in cerebritic stage
  • Very small lesion < 3cm
  • Poor surgical candidate
  • Multiple small abscesses
  • Critical location- Dominant hemisphere, Brain stem
  • Concomitant Meningitis


  • get blood culture
  • antibiotics (3rd generation cephalosporin+ metronidazole+ vancomycin) or according to blood culture
  • steroid
  • anti conversant

Surgical Treatment:


  •  significant mass effect exerted by the lesion
  • proximity to ventricles
  • raised ICP
  • traumatic abscess with foreign body
  • multiloculated abscess



courtesy  :

Dr. Zahed, MS, FCPS

Asst. Professor, Neurology

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