INFECTIONS OF CENTRAL NERVOUS SYSTEM

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

Meningitis:

Inflammation of leptomeninges.

Bacterial, Viral, Fungal.

Pyogenic, Tubercular

Meningitis—

• 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

Strep.

Antibiotics of choice – Flucoxacilline, Vancomycin, Ceftazidime

Route of entry—

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

Diagnosis—

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  

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

Pathogens:

• 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.

Presentation:

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

Evaluation:

Blood work

Imaging-

• 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

Management:

Medical Treatment:

Indications:

• 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

treatment:

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

Surgical Treatment:

Indication:

•  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