Central Nervous System Infections

Central nervous system infections are usually:

Blood-borne invasion; most common

(e.g. polioviruses or Neisseria meningitidis)

Invasion via peripheral nerves; less common      

 (e.g. herpes simplex, varicella-zoster, rabies)

Blood-borne invasion takes place across: 

     - blood-brain barrier (encephalitis)

     - blood-cerebrospinal fluid (CSF) barrier (meningitis)

Invasion via peripheral nerves:

* Herpes simplex virus (HSV) and varicella-zoster virus (VZV) present in skin or mucosal lesions travel up axons to reach the dorsal root ganglia. 

* Rabies virus, introduced into muscle tissues by:   

     - bite of a rabid animal 

   - It enters peripheral nerves and travels to CNS, to reach the neurons

Pathologic consequences of CNS infection

In CNS; viruses infect neural cells, sometimes showing a marked preference

Polio and rabies viruses invade neurons. CJD virus invades oligodendrocytes

Spread of infection is direct from cell to cell along established nervous pathways

Bacteria and protozoa induce brain abscesses 

Meningitis

* Meningitis is one of the most terrifying disease

* It can be fatal in hours

* Early symptoms resemble, self-limiting condition (flu and colds)

Most common causes of meningitis are:

  a) Bacterial infections (Septic meningitis) may result in death or brain damage. 

  b) Viral infections (Aseptic meningitis) usually resolve without treatment. 

Bacterial Meningitis (Septic Meningitis)

Pneumococcal, Streptococcus pneumoniae (38%)

Meningococcal, Neisseria meningitidis (14%)

Haemophilus influenzae (4%)

Staphylococcal, Staphylococcus aureus (5%)

Tuberculous, Mycobacterium tuberculosis

Viral Meningitis (Aseptic meningitis)

Etiological Agents: 

Enteroviruses, most common (Coxsackie and Echovirus)

Adenovirus

Arbovirus

Measles virus

Herpes Simplex virus

Varicella Zoster virus
by
Akshaya Srikanth, Sunil Jain*
Pharm.D Intern, *Chief Pharmacist
Hyderabad, India