Neuroinfectious disease is a high-yield topic for all neurology exams. You should be familiar with the commonly tested viral, bacterial, fungal, and parasitic infections; especially how to diagnose and treat them. Here you will find the topics and facts with the most weight for RITE® and board exams, along with quality radiology and pathology images, flashcards, and a practice quiz!

Authors: Steven Gangloff MD, Brian Hanrahan MD

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Congenital

Congenital rubella

  • A neuroinfectious disease that causes cataracts, congenital heart defects (PDA), deafness, microcephaly, and developmental delay. Less likely hepatosplenomegaly and jaundice.
  • MRI with periventricular and cortical (especially basal ganglia) calcifications.

Congenital Toxoplasmosis

  • Causes chorioretinitis (usually bilateral), macrocephaly (due to intrauterine hydrocephalus), seizures, developmental delay, jaundice, hepatosplenomegaly, thrombocytopenia, and purpuric rash.
  • MRI with calcifications of the basal ganglia and corticomedullary junction.
Neuroinfectious Disease congenital toxoplasmosis cortical necrosis
A coronal section of a single cerebral hemisphere from an infant who had congenital toxoplasmosis. There are foci of subpial, white matter, and subventricular necrosis. Congenital toxoplasmosis results from the transplacental spread of protozoa and is almost always due to primary maternal infection during pregnancy.

Congenital Cytomegalovirus (CMV)

  • Causes developmental delay, seizures, sensorineural deafness, hepatosplenomegaly, vision loss, microcephaly, and lissencephaly.
  • This neuroinfectious disease is the leading cause of acquired hearing loss in childhood, and hearing loss may even occur in children who had an asymptomatic CMV infection at birth.
  • Neuroimaging will show periventricular calcifications, profound cortical atrophy and ventriculomegaly. May also have associated anterior temporal cysts with white matter disease.
Neuroinfectious disease Congenital CMV MRI periventricular calcifications
(Left, Middle) Axial GRE sequences show multiple small foci of susceptibility at the basal ganglia (arrow) as well as along the cerebellar folia, suggesting calcification. Periventricular calcification is considered one of the most common features. (Right) Coronal T2 MRI shows diffuse parenchymal atrophy with a secondary expansion of the ventricular system with bilateral dysplastic hippocampi.

Neonatal herpes simplex

  • Exposure to genital herpes through the birth canal.
  • MRI with multifocal lesions, temporal lobe involvement, hemorrhages, and relative sparing of basal ganglia.

Congenital syphilis

  • Presents at birth with mucoid or bloody nasal discharge (“snuffles”), long bone deformities, Hutchinson’s teeth, keratitis/blindness, and frontal bossing.

Congenital HIV/AIDS

  • Symptom onset between 2 months and 5 years with a loss of milestones, failure of brain growth, ataxia, myoclonus +/- seizures, and spastic paresis.
  • Pathology with multinucleated giant cells and calcific vasculopathy (see below).
  • MRI with diffuse atrophy.

Bacterial

Bacterial Meningitis/Meningoencephalitis/Abscess

Causes of Bacterial Meningitis and Appropriate Treatments:

Age Group Most Common Pathogen Antibiotics
Newborns <1 m.o.
  1. Group B Streptococcus
  2. Escherichia coli
  3. Listeria monocytogenes
 Cefotaxime and ampicillin
(Must avoid ceftriaxone if less than 1 m.o.
due to jaundice risk)
Children
  1. Streptococcus pneumoniae
  2. Neisseria meningitidis
  3. Haemophilis influenzae type B
 Ceftriaxone, vancomycin, acyclovir
Plus dexamethasone if S. pneumoniae expected
Adolescents & Adults
  1. Neisseria meningitidis
  2. Streptococcus pneumoniae
 Ceftriaxone, vancomycin, acyclovir
Plus dexamethasone if S. pneumoniae expected
Adults > 50 y.o.
  1. Streptococcus pneumoniae
  2. Neisseria meningitidis
  3. Listeria monocytogenes
 Ceftriaxone, vancomycin, acyclovir, ampicillin

CNS abscess

  • It is high yield to be able to identify CNS abscess on MRI:
    • An abscess will have internal restricted diffusion due to the presence of pus, with a smooth rim of enhancement and adjacent vasogenic edema.
    • If multiple lesions are present, consider septic emboli.
Neuroinfectious disease Cerebral Abscess on MRI
Cerebral Abscess
  • Citrobacter species, Serratia marcescens, Proteus, Pseudomonas, and Enterobacter are common causes.
  • Ventriculitis is another possible complication of meningitis:
    • On MRI, ventriculitis appears as fluid levels within the cortical sulci and within the posterior horns of the lateral ventricles with increased signal and on the T1-weighted postcontrast views with extensive enhancement of the ependyma.
  • Lasting sequela of bacterial meningitis can include hearing loss, permanent motor deficits, learning disability, epilepsy, and/or hydrocephalus.
  • The most common cause of brain abscess in immunocompetent patients is spread from nearby infection (otitis, mastoiditis > sinusitis).
    • This accounts for 40-50% of cases.
    • Hematogenous spread (such as from endocarditis) accounts for 30-40% of cases.
    • Spread from distal infection (such as dental) is possible, but less common.
  • Most significant predisposing factor for bacterial abscess in children is cyanotic congenital heart disease.
  • Treatment:
    • Empiric brain abscess antibiotic treatment includes a third-generation cephalosporin and metronidazole.
      • Because >95% of brain abscesses are bacterial, and of those many are polymicrobial, broad-spectrum coverage is needed until a brain aspiration can confirm the pathogen.
      • An exception is if endocarditis is already confirmed or highly suspicious, in which case IV nafcillin is often used.
    • In addition to antibiotics, surgical drainage is a needed treatment.
    • Glucocorticoids can be considered if the abscess has mass effect large enough to cause significant depression of mental status.
 

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