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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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Table 555-1. Signs and Symptoms of CNS Infection
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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 ...

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