Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (86 page)

nb, Kernig’s or Brudzinski’s signs
in only ~10% of Pts (
Lancet
2012;380:1684)

• ± Focal neuro findings (~30%; hemiparesis, aphasia, visual field cuts, CN palsies) • ± Funduscopic findings: papilledema, absent venous pulsations • ± Rash: maculopapular, petechial or purpuric
Diagnostic studies
(
Lancet
2012;380:1684)

•
Blood cultures ¥ 2
before abx

•
WBC count
: >10,000 in >90% of bacterial meningitis in healthy hosts •
Consider
head CT
to r/o mass effect before LP
if
presence of high-risk feature (age

>60 y, immunosupp., h/o CNS disease, new-onset seizure, Δ MS, focal neuro

findings, papilledema); absence of all these has NPV 97%; however, in Pts w/ mass effect, herniation may occur w/o LP and may not occur even w/ LP (
NEJM
2001;345:1727)

•
Lumbar puncture
(
NEJM
2006;355:e12)

CSF Gram stain
has 30–90% Se; cx 80–90% Se if LP done prior to abx role of CSF PCR for common bacterial causes (? ~90% Se if w/in 2 h) to be defined repeat LP only if no clinical response after 48 h of appropriate abx or CSF shunt

Opening pressure
typically ↑ in bact meningitis; must measure w/ Pt’s legs extended

Rule of 2s
: CSF WBC >2k, glc <20, & TP >200 has >98% Sp for bacterial meningitis

Recurrent meningitis

• Bacterial: consider CSF leak, dermal sinus or other congenital/acquired anatomic defects • Viral: HSV-2 (causes majority of Mollaret’s meningitis) • Aseptic (see below): leak from cyst/tumor/lesion with dermoid/epidermoid elements, autoimmune (eg, SLE, Behçet’s), medications

• Additional CSF studies based on clinical suspicion: AFB smear & cx, India ink prep, cryptococcal Ag, fungal cx, VDRL, PCR (eg, of HSV, VZV, enteroviral), cytology

Prognosis

• For community-acquired
S. pneumo
mort. 19–37%; 30% have long-term neuro sequelae

ASEPTIC MENINGITIS

Definition

•
Negative bacterial micro data
, CSF pleocytosis with
appropriate blood & CSF cultures (aseptic meningitis can be neutrophilic, though less common) • Aseptic = less likely to be bacterial, but can be infectious or noninfectious
Etiologies
(
Neurology
2006;66:75)

•
Viral
: enteroviruses (most common), HIV, HSV (type 2 > 1), VZV, mumps, lymphocytic choriomeningitis virus, encephalitis viruses, adenovirus, polio, CMV, EBV

•
Parameningeal focus of infection
(eg, brain abscess, epidural abscess, septic thrombophlebitis of dural venous sinuses or subdural empyema) •
Partially treated bacterial meningitis
•
TB
,
fungal
,
spirochetal
(Lyme, syphilis, leptospirosis),
rickettsial
,
Coxiella
,
Ehrlichia
•
Medications
: TMP/SMX, NSAIDs, IV Ig and antilymphocyte Ig, PCN, INH, lamotrigine •
Systemic illness
: SLE, sarcoidosis, Behçet’s, Sjögren’s syndrome, RA •
Neoplasm
: intracranial tumors (or cysts), lymphomatous or carcinomatous meningitis (CSF cytology or flow may be reactive and dx may require meningeal bx)
Empiric treatment

• No abx if suspect viral (cell count <500 w/ >50% lymphs, TP <80–100 mg/dL, normal glc,
Gram stain, not elderly/immunosupp.); o/w start empiric abx, wait for cx data • If suspect MTb: antimycobacterial Rx + dexamethasone (
NEJM
2004;351:1741) • If suspect fungal: ampho lipid formulation, ± 5-fluorouracil

ENCEPHALITIS

Definition

• Infection of brain parenchyma with evidence of neurologic dysfunction
Etiologies
(specific etiology found in
<20% of cases;
Neurology
2006;66:75;
CID
2008;47:303)

•
HSV-1
(~9%): all ages/seasons; MRI: temporal lobe lesions/edema; EEG: temporal focus •
VZV
(~9%): 1° or reactivation; ± vesicular rash; all ages (favors elderly), all seasons •
Arboviruses
(~9%): Eastern/Western equine, St. Louis, Japanese, Powassan, W. Nile (
NEJM
2005;353:287): mosquito vector, bird reservoir; fever, HA,
flaccid paralysis
, rash. Risk factors for severe dis: renal dis., cancer, EtOH, DM, HTN (
Am J Trop Med Hyg
2012;87:179).

•
Enteroviruses
(coxsackie, echo): viral syndrome; peaks in late summer/early fall • Others: CMV, EBV, HIV, JC virus (PML), measles, mumps, rubella, rabies, flu, adenovirus • Nonviral mimics: bacterial endocarditis, brain abscess, toxoplasmosis, TB, toxins, vas-culitis, hematologic malignancies, Whipple’s disease, subdural hematoma, encephalomyelitis (eg, ADEM), paraneoplastic syndromes, seizure, mitochondrial disorders, autoimmune anti
N
-methyl-D-aspartate receptor (esp. if <30 y,
CID
2012;54:899)
Clinical manifestations

•
Fever
,
HA
, Δ MS, ± seizures and focal neuro findings (latter atypical for viral
meningitis
)
Diagnostic studies
(etiologic dx made in only about 25% of cases)
• Vaccine hx, dilated retinal exam, ELISA or DFA nasal/resp swabs for viruses, serologies •
Lumbar puncture
: lymphocytic pleocytosis; PCR for HSV (95% Se & Sp at 2–3 d), VZV, CMV, EBV, HIV, JC, adeno/enterovirus, W. Nile (<60% Se); W. Nile CSF IgM 80% Se •
MRI
(CT if MRI unavailable); W. Nile w/ thalamic hyperintensity • EEG to r/o seizure; findings in encephalitis are nonspecific
Treatment

• HSV, VZV: acyclovir 10 mg/kg IV q8h (often empiric Rx given frequency of HSV/VZV) • CMV: ganciclovir ± foscarnet; supportive care for most other etiologies

BELL’S PALSY

Definition & etiology

• Acute idiopathic unilat.
facial nerve palsy
(CN VII), often presumed HSV-1 reactivation
Clinical manifestations

• Unilateral
facial muscle weakness
,
hyperacusis
, ↓ taste/lacrimation/salivation
Diagnosis

• Dx of exclusion: r/o brainstem lesion, Lyme, zoster (incl
sine herpete
), HIV/AIDS, sarcoid
Treatment
(
NEJM
2007;357:1598;
JAMA
2009;302:985)

• ~80% recover spontaneously by 9 mo (much lower rate in DM) • Corticosteroids (prednisolone 25 mg PO bid × 10 d) started w/in 72 h of sx onset improve odds of recovery (note: no conclusive data for use in DM, immunosupp.) • No conclusive data to support the use of acyclovir or valacyclovir, though often prescribed

ZOSTER

Definition & etiology

• Zoster = herpes zoster = shingles: acute, unilat.,
painful dermatomal skin eruption
• VZV reactivation in peripheral nerve distribution from latency in dorsal root ganglion
Clinical manifestations

•
Neuritic pain in a dermatomal distribution
, then acute
dermatomal eruption of clustered rash
(vesicles > papules/pustules > macules) in varying stages of evolution • Consecutive dermatomes may be seen in all Pts; more widespread in immunosupp.

• Lesions in V1 distribution of facial nerve require urgent ophthalmologic evaluation • Post-herpetic neuralgia (PHN) = severe pain lasting >90 d after episode; may last mos to y, more frequent w/ ↑ age and delay of antiviral Rx
Diagnosis

• Appearance of rash; DFA is most Se from scrape of newly unroofed vesicle. Tzanck does not distinguish HSV or VZV, cx insensitive for VZV (unlike HSV).