This document summarizes various infectious diseases of the nervous system, including meningitis (caused by bacteria like E. coli, streptococcus pneumoniae, and neisseria meningitidis), encephalitis (often caused by viruses like herpes simplex, cytomegalovirus, and poliovirus), and brain abscess (most commonly caused by streptococcus and staphylococcus aureus spreading from the sinuses). It describes clinical features, causative organisms, routes of infection, and histopathological findings for different conditions.

1. Infectious Diseases of the Nervous System

2.  Meningitis (generally* bacterial)
◦ E. coli, Strep B (neonates)
◦ H. influenzae (children)
◦ Neisseria meningitidis (adults)
◦ Strep. pneumoniae, Listeria (elderly)
◦ PMNs in CSF, INCREASED protein, REDUCED glucose
 Encephalitis (generally viral)
◦ Arboviruses, HSV, CMV, V/Z, polio, rabies, HIV
◦ Lymphs and macrophages in perivascular spaces
 Meningoencephalitis: Viral,Bacterial,Fungal
and Parasitic.
viral, chemical, tumoral

3.  Routes of entry for infections of the nervous
system :
 -Hematogenous (the most common )
- Direct implantation (traumatic or iatrogenic)
- Local extension (sinusitis )
- Peripheral nerves ( as in Rabies and HSV
which invade the nerve terminals and ascend
to CNS )

4.  ACUTE PYOGENIC(BACTERIAL) MENINGITIS :
*Causative organisms : see before
 Clinical picture :
-Headache, photophobia, malaise,irritability ,
mental confusion, fever, vomiting .
-Physical examination showing neck stiff-
ness .
Lab.: CSF examination with Gram stain and
culture .
 Complications : Increased ICP with fatal
herniation if untreated properly

7.  ACUTE ASEPTIC(VIRAL) MENINGITIS.
 *It is a benign, short-lived meningeal
inflammation
*Viral causes include:
 -Enteroviruses(MOST common) , Echovirus
and Coxsackievirus
 *Scanty meningeal infiltrate with lymphocytes .
 CSF shows lymphocytic increase , with moderate
protein elevation and nearly normal sugar content .

8.  BRAIN ABSCESS.
 Etiology.
*Streptococci and Staph.aureus (most common)
-Direct spread from paranasal sinuses(50%)
-Hematogenous(25%)from lung abscess,
subacute endocarditis, bronchiectasis or after
tooth extraction .
 -Mortality – 20%
-Morbidity with focal neurologic deficits or
epilepsy (50%)

9. Discrete lesion with central liquefactive
necrosis , a surrounding fibrous collagenized
response and edema

10. Granulation tissue formation with
exuberant neovascularization

11.  Tuberculous meningitis .
 Tubeculoma
 SYPHILIS, gummas in brain

12. TUBERCULOMA

13.  ARBO VIRUSES
 HSV1 , HSV2 , V/Z
 CMV , POLI0 , RABIES
 HIV
 Progressive Multifocal Leukoencephalopathy : polyoma virus (JC)
 Subacute Sclerosing Panencephalitis (Measles)
 Perivascular and parenchymal mononuclear cell
infiltrate(Lymphocytes, plasma cells and macrophages) is the most
characteristic histologic feature of viral encephalitis
 Viral infection can lead to abnormal intranuclear inclusions, as seen
in herpetic infection (Cowdry body), cytoplasmic inclusions, as seen
in rabies (Negri body), or both nucleus and cytoplasm
(cytomegalovirus)

14. VIRAL
ENCEPHALITIS
PERIVASCULAR
LYMPHOCYTIC
“CUFFING”

15.  Cowdry Body intranuclear inclusion in a
neuron in herpes simplex encephalitis.

17. Intracytopasmic
Eosinophilic Negri
body of Rabies

18.  includes
 *Creutzfeldt-Jakob disease(CJD) the most common
 *Gerstmann-Strausler-Scheinker dis.(GSS)
 *Fatal familial insomnia(FFI)
 *Kuru
 COMMON FEATURES.
 -Accumulation of abnormal cellular protein termed Prion
protein(PrP) which is infectious and transmissible
 -Transmission: sporadic(85%),familial(15%),iatrogenic
CJD(inoculation, corneal transplant) .
 -Epidemiology: CJD incidence 1-2/million
 age of onset 55-75
 Characterised by spongiform changes caused by intracellular vacuoles in
neural cells .
 Progressive dementia ends by death usually within 7 months .

19. Spongiform change in the cerebral cortex

20.  What is the most common cause of brain
abscess in adults ?
 a) Streptococcus and staphylococcus aureus .
 b) TB
 c) toxoplasmosis
 d) Neisseria