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CHAPTER 72: Encephalomyelitis 665

• Mamelak AN, Mampalam TJ, Obana WG, et al. Improved man-
agement of multiple brain abscesses: a combined medical and • Supportive care, along with appropriate therapy, is essential
surgical approach. Neurosurgery. 1995;36:76-86. because some patients recover even following protracted illness.
• Nathoo N, Nadvi SS, Gouws E, et al. Craniotomy improves out- • Consider bioterrorism in unexplained outbreaks, especially when
come for cranial subdural empyemas: computed tomography-era the presentation is unusual or out of season.
experience with 699 patients. Neurosurgery. 2001;49:872-878.
• Thigpen MC, Whitney CG, Messonnier NE, et al. Bacterial
meningitis in the United States—1998-2007. N Engl J Med.
2011;364:2016-2025.
• Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines INTRODUCTION
for the management of bacterial meningitis. Clin Infect Dis. Encephalomyelitis is a combination of two disease states affecting the
2004;39:1267-1284. central nervous system (CNS). Encephalitis is defined as an inflamma-
• van de Beek D, Brouwer MC, Thwaites GE, Tunkel AR. Advances in tory process of the brain associated with neurologic dysfunction; myeli-
the treatment of bacterial meningitis. Lancet. 2012;380:1693-1702. tis is an inflammatory process affecting the spinal cord. These may occur
• van de Beek D, Drake JM, Tunkel AR. Nosocomial bacterial men- separately or together. Occasionally the covering of the brain is involved
and therefore the term meningoencephalitis or meningoencephalomy-
ingitis. N Engl J Med. 2010;362:146-154.
elitis may be more appropriate.
There are about 20,000 cases of encephalomyelitis reported per year.
The approach to each suspected case of encephalomyelitis should be
REFERENCES standard yet individualized based on that patient’s clinical presenta-
tion. The course of symptoms, season of the year, travel, local out-
Complete references available online at www.mhprofessional.com/hall breaks, occupation, animal or insect exposure, recent illness, immune
status, age, and recent vaccine history all play a part in establishing a
diagnosis. Physical examination is not usually revealing, but rashes,
CHAPTER Encephalomyelitis inoculation reactions, or pneumonia can be helpful clues.
Though viruses are the predominant cause of encephalomyelitis,
72 Peter Spiro autoimmune and acute disseminated encephalomyelitis (ADEM) may
account for approximately 20% of cases. Other noninfectious causes of
Venkata Ranganadh Dodda
Vel Sivapalan this syndrome must also be excluded, such as vasculitis, connective tissue
diseases, and paraneoplastic syndromes.
A clinical correlation between non-CNS infections and CNS manifes-
KEY POINTS tations is not always clear or evident. An individualized workup includes
culture, PCR, antigen detection, and serologic IgM and IgG titers of
• Encephalomyelitis should be suspected in patients with neurologic noncentral nervous tissue (ie, sputum, stool, blood, and nasopharyngeal
findings including fever, headaches, odd behavior, altered senso- swabs). CSF analysis is of great value if lumbar puncture is not contrain-
rium, seizures, and focal neurologic deficits without obvious cause. dicated by findings on clinical examination or imaging. The results must
• Course of symptoms, season of the year, travel, local outbreaks, be used carefully based on the context of the presentation.
occupation, animal or insect exposure, recent illness, immune status, CSF is almost always abnormal but a normal study does not preclude
age, and recent vaccine history all play a part in trying to establish disease. A positive PCR or antigen study should help guide the treat-
a diagnosis. Physical examination is not usually revealing, but ment. Cell counts in the CSF can be clues to nonviral causes (eg, eosino-
rashes, inoculation reactions, or pneumonia can be helpful clues. philia with parasites and coccidioidomycosis).
• An individualized workup based on the above includes culture, Magnetic resonance imaging (MRI) is a key part of the workup, is
PCR, antigen detection, serologic IgM and IgG titers of noncentral more reliable than CT, and should be obtained prior to lumbar puncture
nervous tissue, as well as cerebrospinal fluid (CSF) analysis if not if possible. If MRI cannot be done or is impractical, CT with and with-
contraindicated by examination. The results must be used carefully out contrast can be helpful. PET, EEG, and brain biopsy are not usually
based on the context of the presentation. required. MRI or CT can occasionally be diagnostic or help guide the
workup in other directions. In the presence of a raised intracranial
• CSF is almost always abnormal but a normal study does not pre- pressure, a cisternal puncture can be done to obtain CSF. EEG can be
clude disease. A positive PCR or antigen study should help guide useful in patients with persistent altered mental status to evaluate for
treatment. Cell counts in the CSF can be clues to nonviral causes nonconvulsing status epilepticus and temporal activity associated with
(eg, eosinophilia with parasites and coccidioidomycosis). herpes simplex encephalitis.
• Magnetic resonance imaging (MRI) is a key part of the workup Despite all efforts to obtain a diagnosis, most cases of meningoen-
and is more reliable than CT scan. Either of these tests should be cephalitis remain cryptic. Arboviruses are the most common epidemic
obtained prior to lumbar puncture if possible. causes of encephalomyelitis; they are usually preceded by zoonotic out-
• Herpes simplex virus (HSV) is the most common cause of non- breaks, that is, chickens in St Louis encephalitis, birds in West Nile, and
epidemic fatal encephalitis. Early treatment with acyclovir signifi- horses in Eastern Equine Encephalitis.
cantly reduces mortality. Herpes simplex virus (HSV) is the most common cause of non-
• Arboviruses are the most common cause of epidemic outbreaks epidemic fatal encephalitis. If untreated, mortality is approximately
60% to 80%; early treatment with acyclovir significantly reduces
worldwide and depending on the area and season may be a clue mortality to approximately 10% to 20%. All suspected cases of
to the origin. encephalomyelitis should be treated with acyclovir while the results
• In all suspected cases of encephalomyelitis treatment with full-dose of the workup are pending. In addition, antibiotics, antifungals,
acyclovir should begin quickly until a diagnosis is established. A nega- and antituberculosis medications may be appropriate based on the
tive workup does not preclude HSV so empiric therapy is appropriate. clinical presentation. In patients with ADEM, corticosteroids should
be considered, as well as plasma exchange if the patient’s condition

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