Page 939 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

670 PART 5: Infectious Disorders

cause shingles (zoster) and postherpetic neuralgia. VZV is the only
human virus known to replicate in arteries. VZV involves both small
and large vessels and the term, VZV vasculopathy rather than encepha-
litis best suits this syndrome. The incidences of neurologic complica-
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tions with primary varicella are 1 to 3 per 10,000 cases. Among them
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cerebellar ataxia and encephalitis are common, while other entities
such as aseptic meningitis, transverse myelitis, Guillain-Barré or Reye
syndromes have been reported. Cerebellar ataxia is seen in children
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and occurs with a frequency of 1 per 1000 cases of chickenpox. It is
characterized by ataxia, nystagmus, headache, nausea, vomiting, and
nuchal rigidity. This illness is usually self-limited, lasting 2 to 4 weeks,
and most children have a complete recovery. The mortality rate is only
0.5%. A more severe form of encephalitis occurs mostly in adults and
infants, with an incidence of one to two episodes per 10,000 cases of
VZV. It most often begins approximately 1 week after the varicella rash
and is manifested by altered sensorium, seizures, and focal neurologic
signs and has a mortality rate of 5% to 10%. Neurologic complications
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from zoster can occur acutely for weeks to months after the rash.
Other than the common postherpetic neuralgia, encephalitis, myelitis,
cranial nerve palsies (Bell palsy and Ramsay Hunt syndrome), and
ophthalmic zoster are associated with VZV. Zoster encephalitis usu-
30
ally manifests as delayed contralateral hemiparesis/stroke due to large
vessel vasculopathy. This is most commonly observed in the elderly and
can occur weeks to months after an episode of herpes zoster, typically
FIGURE 72-3. Increased temporal lobe signal on axial DWI image. involving the first division of the trigeminal nerve. It is thought that
VZV directly invades cerebral arteries by extension along intracranial
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asymptomatic infected mothers. Neonatal encephalitis is associated with branches of the trigeminal nerve. Diagnosis is usually supported by
serious mortality and morbidity. In adults, HSV-2 primarily causes angiography that shows narrowing and thrombosis of the anterior and
19
genital infection and remains latent in sacral ganglia with viral shedding. middle cerebral arteries. The mortality rate is 20% to 25% and there is
32
Neonatal infection occurs with a frequency of 26 per 100,000 deliveries a strong probability of permanent neurologic sequelae. Chronic zoster
and although infection may be localized to the skin, it is more often dis- encephalitis is a variant of zoster encephalitis, seen almost exclusively in
seminated. It is recommended that all women in labor be examined for the immunocompromised, especially in AIDS patients and those with
genital HSV-like lesions and cesarean section be performed if lesions are impaired cell–mediated immunity. They present with headache, fever,
present and membranes are intact. One can neither predict nor prevent mental status changes, seizures, and focal neurologic signs. The onset
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these exposures. Approximately 50% of neonates with encephalitis are may occur months after the zoster rash, making the diagnosis more
premature, and clinical illness typically begins 1 to 3 weeks after birth. difficult. Pathology shows small vessel vasculopathy and demyelination.
33
Although CNS disease can occur in isolation, more commonly there is The clinical course is often progressive deterioration and death. VZV
evidence of diffuse disease with accompanying skin lesions, hepatitis, myelitis is a more common complication of zoster compared to varicella.
pneumonitis, or disseminated intravascular coagulation. The symptoms In most patients, spinal cord involvement is subtle or asymptomatic
21
in newborns are very nonspecific and consist of lethargy, failure to feed, manifesting as paresis, sphincter dysfunction, and impaired sensation
tremors, irritability, or seizures and, in the absence of skin lesions, may with a level compatible with the segment of VZV reactivation. Complete
34
be difficult to distinguish from other newborn encephalitides. The diag- recovery is the usual course. The diagnosis of VZV encephalitis may be
nosis should be suspected in any infant who becomes encephalopathic suspected on the basis of the characteristic lesions of varicella or zoster.
during the initial weeks of life. Skin vesicles are the easiest source of The virus may be identified from vesicular scrapings on Tzanck smear,
viral isolation and confirmation of diagnosis, but up to 20% of newborns immunofluorescence, electron microscopy, or culture. The virus grows
with HSV infection never have skin involvement. These infants often slowly, usually requiring 2 to 3 weeks for a positive culture. Serologic
excrete virus from peripheral sites in the absence of skin lesions; hence, recognition of specific IgM antibody is useful for diagnosing primary
conjunctival, throat, and CSF specimens should be submitted for viral chickenpox. As with HSVE, PCR analysis for CSF VZV DNA and VZV
35
studies. PCR testing for HSV-2 DNA in CSF is important to confirm antibody may be used to confirm the diagnosis. Intravenous acyclovir
22
the diagnosis. Unlike adult HSVE, viral cultures of the CSF for HSV-2 is the drug of choice for VZV encephalitis, at dose of 10 mg/kg every
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are often positive in neonates. Further diagnostic evaluation may include 8 hours for 7 to 10 days. A short course of steroids for 3 to 5 days is also
EEG, brain scan, CT, ultrasonography, and MRI, alone or in combina- recommended. Immunocompromised patients may require a longer
tion, depending on the circumstances. MRI shows more diffuse disease course. Treatment should be continued until negative CSF PCR tests. 30
MRI is more sensitive in detection of early lesions in neonatal encepha- ■ CYTOMEGALOVIRUS
and may reveal cavitary lesions and hemorrhages. Diffusion-weighted
24
litis. Early empirical treatment with acyclovir is important in decreasing CMV infections of the CNS occur mostly in immunocompromised
mortality and morbidity rates. Without treatment, the mortality rate patients, especially in those with AIDS and after bone marrow and
is 50% to 85% and the morbidity rate is 100%. Acyclovir at 20 mg/kg solid organ transplantation. 36,37 CMV rarely affects immunocompetent
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every 8 hours for 21 days is the current recommended dose for neonatal patients. CNS infections can manifest as diffuse encephalitis, meningo-
HSVE. With this larger-dose treatment, the mortality has decreased to encephalitis, ventriculoencephalitis, CNS mass lesions, transverse myeli-
26
5% and about 40% of the survivors develop normally. tis, and polyradiculopathy. CMV encephalitis (CMVE) is diffuse and
■ VARICELLA-ZOSTER VIRUS is the most common CMV infection of the CNS. Typically, it presents
subacutely, with lethargy, confusion, cranial nerve palsies, and coma.
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Varicella-zoster virus is exclusively a human DNA virus of Herpesviridae CT of the brain is nonspecific, with the exception of periventricular
family. It causes chickenpox primarily, becomes latent in cranial nerves enhancement seen in ventriculoencephalitis. MRI is preferred over CT
and dorsal root ganglia, and reactivates with immunosuppression to even though it also has limitations. MRI findings include periventricular

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