Brain Infections

Question 1

Four cardinal signs of brain inflammation:

Answer 1

Fever, headache, altered mental status, and focal neurologic signs.

Question 2

Meningitis:

Answer 2

Inflammation of the membranes of brain and spinal cord (involving the subarachnoid space)

Question 3

Encephalitis:

Answer 3

Inflammation of the brain parenchyma

Question 4

Myelitis:

Answer 4

Inflammation of the spinal cord

Question 5

Encephalopathy:

Answer 5

Disorders/diseases of the brain that include non-infectious causes.

Question 6

Acute encephalitis presentation:

Answer 6

Fever, headache, altered mental status, speech problems, seizures, motor weakness, hyper-reflexia, abnormal movements/tremor, pituitary involvement, spinal cord involvement, raised ICP.

Question 7

Chronic encephalitis causes and presentation:

Answer 7

Syphilis.

Causes: sensory changes, ataxia, and dementia

Question 8

“Space-occupying lesions” causes and presentation:

Answer 8

Brain abscesses (causes fever, headache, confusion, hemiparesis, aphasia).
Epidural abscesses (causes fever, back pain, loss of LE strength/rectal tone/urinary retention)

Question 9

Toxin-mediated syndromes causes and presentation:

Answer 9

Clostridium tetani (causes SPASTIC paralysis).
Clostridium botulinum (causes cranial nerve and respiratory FLACCID paralysis).

Question 10

Acute encephalitis causes:

Answer 10

ARBOVIRUSES (1-50% fatal), HSV (70% fatal), RABIES (99% fatal without prophylaxis), coxsackie, EBV, CMV, mumps.

Question 11

Pathophysiology of viral encephalitis:

Answer 11

True encephalitis: Direct tissue destruction, vascular damage, and edema. Hematogenous (EEE, West Nile) or Neuronal (HSV, rabies) transmission.
Post-infectious encephalomyelitis: autoimmune demyelination

Question 12

West Nile virus:

Answer 12

Commonly causes: fatigue, fever, headache, muscle weakness, rash.
Rarely causes: ENCEPHALITIS, meningitis, flaccid paralysis.
Diagnosis: PCR, CSF analysis (lymphocytic pleocytosis, elevated protein, CSF antibody), EEG reveals generalized slowing (frontal and temporal)
Treatment: Supportive
Prevention: Mosquito control, insect repellants.

Question 13

Herpes simplex encephalitis:

Answer 13

Causes perinatal encephalitis in neonates (HSV 1 or 2), sporadic encephalitis in adults (HSV 1).
Routes of infection:
1) primary infection (usually of oropharynx) with CNS invasion via trigeminal nerve,
2) CNS invasion after RECURRENT HSV-1 INFECTION,
3) CNS infection without clinically obvious primary OR recurrent HSV-1 infection
HSV-1 localizes to medial-temporal, orbital-frontal lobes, limbic structures. HSV-2 can be more generalized.
Causes: fever, headache, altered consciousness, personality changes, seizures, aphasia, hemiparesis.
Diagnosis: CSF (high opening pressure, lymphocytic pleocytosis with red cells, normal glucose, elevated protein), HSV PCR, EEG, MRI
Treatment: IV acyclovir (high dose)

Question 14

Rabies encephalitis:

Answer 14

Reservoirs include raccoons, skuns, foxes, dogs, coyotes. Animal bites are most serious risk for human disease.
Virus replicates in muscle cells at wound site, and is taken up by unmyelinated peripheral nerve terminals and transported to CNS by retrograde flow. Serum antibody develops in 10 days, but this does not halt viral replication.
Symptoms: no symptoms until virus reaches spinal cord. Produces agitation, HYDROPHOBIA, excessive salivation, arrhythmias, coma, seizures, and death. PARALYTIC rabies (ascending paralysis) occurs in 20%.
Prevention: post-exposure prophylaxis with rabies vaccine and rabies immunoglobulin.

Question 15

Acute demyelinating encephalomyelitis (ADEM):

Answer 15

Also known as post-infectious encephalomyelitis.
An autoimmune demyelinating disease that mimics acute viral encephalitis. May be a history of illness in the weeks before presentation. Rarely, it follows vaccination or atypical bacterial infection.
CSF is usually normal. MRI scanning shows enhancing multifocal white matter disease with demyelination.

Question 16

Brain abscess:

Answer 16

One of the main “space-occupying” brain lesions. Fever present in 50%.
Mechanisms of infection are local extension or hematogenous spread.
Risk factors: otitis media, mastoiditis, sinusitis, dental sepsis, penetrating trauma, neurosurgery.
More common in the IMMUNOCOMPROMISED.
IMAGINING IS CRITICAL
Treatment: drainage, empiric therapy (vancomycin/ceftriaxone/metronidazole). For HIV, empiric treatment for toxoplasma. Rule out PML, lymphoma.