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Infections of the central nervous system (CNS) are less frequent
than infections of other organ systems, because the brain is protected
by both the anatomic barrier of the bony skull and blood-brain barrier.
Nevertheless, CNS infections remain a significant cause of morbidity and
mortality in children. Classic signs and symptoms of CNS infections
are often not present or more subtle in young children, thereby
making accurate diagnosis a challenge for the general pediatrician
(Table 555-1). The outcome of CNS infection
predominantly depends on the site of infection and etiologic organism
in addition to host immune status. For full description of bacterial
and viral CNS infections, see Chapters 231 and 232. In this chapter,
we focus on the neurologic presentation of CNS infections and discuss
the unique CNS involvement of purulent CNS infections, latent viral
infections, and prion diseases.
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Meningitis/Meningoencephalitis
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The most common presentation of meningitis includes nonspecific
signs and symptoms such as headache and nuchal rigidity. Meningismus
refers to a condition in which the neck and back muscles tense as
a reflex to avoid painful extension of the inflamed meninges. The
physical findings of Kernig sign (passive extension of the knee from
flexed thigh position elicits pain in the back) and Brudzinski sign
(passive flexion of the neck elicits spontaneous flexion the lower
extremities) are thought to reflect both the inflammation of the meninges
and increased intracranial pressure. Nuchal rigidity is rare in
neonates and uncommon in children ages 12 to 18 months. Other symptoms
of meningitis vary depending on the etiology and location of the
infection. The associated symptoms of fever, vomiting, lethargy,
irritability, photophobia, anorexia, and dehydration all support
the diagnosis.1 In neonates, a full fontanel may be present
in addition to failure to thrive, irritability, apnea, seizures, opisthotonus,
poor feeding, temperature instability, jaundice, and grey appearance.2
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The anatomic boundaries between the meninges and brain parenchyma
are indistinct. Many patients experience concurrent infections of
the meninges and parenchyma, known as meningoencephalitis, often
accompanied by signs of headache, generalized seizures, and mental
status changes (delirium, agitation, somnolence, lethargy). Within the
brain parenchyma, the inflammatory response is characterized by
neutrophilic infiltrations and increased vascular permeability via alteration
of the blood-brain barrier. Focal neurologic symptoms/signs
may ...