patients. Neuro-Behc ̧et’s disease is characterized by fever, headache, and meningeal signs that
closely mimic a bacterial process. Aseptic meningitis, meningoencephalitis, or encephalitis may
also be present. The CSF profile is indistinguishable from aseptic viral meningitis/encephalitis.
There are no distinguishing features on the EEG or head CT/MRI imaging. The diagnosis of
neuro-Behc ̧et’s disease is based on recognizing that the patient has Behc ̧et’s disease and has
neurologic manifestations not attributable to another or superimposed process (20,21).
Neurosarcoidosis is a common manifestation of sarcoidosis. Signs of CNS sarcoid include
headaches, mental confusion and cranial nerve palsies. Any of the cranial nerves may be
affected. Patients with sarcoidosis may often present with polyclonal gammopathy on serum
protein electrophoresis (SPEP), an elevated ESR, leukopenia and mild anemia, and increased
levels of serum angiotensin-converting enzyme (ACE). Chest X ray shows one of the four
stages of sarcoidosis ranging from bilateral hilar adenopathy to parenchymal reticular nodular
fibrotic changes. In neuro sarcoid, the CSF is usually abnormal. A lymphocytic pleocytosis
(300 cells/mm) is usual. Protein levels in the CSF are usually elevated, and*20% of patients
have a decreased CSF glucose level. RBCs are not a feature of neurosarcoidosis. Aseptic
meningitis with sarcoidosis may present as acute meningitis mimicking/viral aseptic meningitis.
Sarcoid meningoencephalitis is more chronic, mimicking the chronic causes of meningitis due to
acid fast bacilli or fungi. Patients usually have a history of sarcoidosis, which is a clue to the
diagnosis. Diagnosis of neurosarcoidosis is a diagnosis of association and exclusion. Neuro-
sarcoidosis occurs in the setting of systemic sarcoidosis and is characterized by a negative CSF
Gram stain and culture. Treatment is with corticosteroids/immunosuppressives (1,20,23,24)
(Table 3).
CLINICAL AND LABORATORY FEATURES OF MENINGITIS
The clinical diagnosis of ABM concerns differentiating it from its mimics as well as the viral/
aseptic causes of meningitis. Patients with ABM have a more fulminant course and tend to be
more critically ill than those with a meningitis mimic or a virally mediated meningeal process.
Many meningeal pathogens have associated systemic manifestations, which, if appreciated
and related to the CNS findings, make the diagnosis of the underlying condition relatively
straightforward. However, in spite of an analysis of predisposing factors, host defense defects,
age of the patient, history of systemic disorders and cutaneous findings, the diagnosis of
meningitis remains based on the analysis of CSF findings. Analysis of the CSF obtained by
lumbar puncture is critical in ruling in the diagnosis of ABM, as well as ruling out viral or
noninfectious causes of meningitis (1,4,8,10,25).
PREDICTING THE PATHOGEN IN MENINGITIS
Normal hosts with ABM may or may not have a variety of historical epidemiologic clues as
well as physical findings that may suggest a particular organism. Patients with chronic
meningitis are diagnostic not therapeutic problems and are not included in this chapter
concerned primarily with the diagnosis and management of patients in the CCU with ABM. In
compromised hosts, the diagnosis of ABM depends on correlating the underlying disorder
with its host defense defect, which predicts the meningeal pathogen. Compromised hosts with
impaired cellular-mediated immunity (CMI) usually present with chronic rather than
bacterial meningitis. Such patients presenting with ABM should be viewed as normal hosts
from the standpoint of pathogen predictability, i.e., the underlying disorder is not responsible
for their meningitis. If a patient who has had an organ transplant or has HIV, for example, is
involved in an outbreak of meningococcal meningitis, the underlying disorder does not
predispose the patient to this pathogen. With ABM, compromised hosts with impaired CMI are
afflicted with the same infectious diseases as are normal hosts. Compromised hosts are not
exempt from the spectrum of infectious diseases that affect immunocompetent hosts.
Compromised hosts with defects in humoral immunity (HI) or those with combined CMI and
HI defects, e.g., chronic lymphatic leukemia (CLL), are predisposed to meningitis due to
encapsulated organisms,Streptococcus pneumoniae,Haemophilus influenzae,orKlebsiella pneumoniae
(1–6,8,18) (Tables 4 and 5).
138 Cunha and Smith