CENTRAL NERVOUS SYSTEM INFECTIONS

Question 1

KEY CONCEPTS

Answer 1

CRITICAL STEPS

Early Recognition
Appropriate Diagnostic Evaluation
Administration of Antibiotics
Adjunctive Corticosteroids

MC PATHOGENS

S. Pneumoniae
N. Meningitidis

CLINICAL FEATURES
The classic triad of fever, neck stiffness and altered mental status occurs in <50% of all patients with bacterial meningitis.

Question 2

MANAGEMENT

Answer 2

1. ANTIBIOTICS

EMPIRIC ANTIBIOTICS: CAM

Do not delay antibiotics for CT or LP, if delayed

Ceftriaxone 2 g IV q 12 h

AND
Vancomycin 20-35 mg / kg / dose IV loading dose (max 3000 g)
THEN
15-20 mg/kg IV q 12 h

ADD
Ampicillin 2 g IV q 4 h IF > 50 yrs, Alcoholic, Pregnant, Immunocompromised

ADD
Acyclovir 10 mg / kg / dose IV q 8 hrs IF HSV suspected (negative gram stain, seizure)

EMPIRIC ANTIBIOTICS: PENETRATING HEAD TRAUMA, POST-NEUROSURGICAL, CSF SHUNT

Cefepime 2 g IV q 8 h

AND
Vancomycin 20-35 mg / kg / dose IV loading dose (max 3000 g)
THEN
15-20 mg/kg IV q 12 h

ADD
Ampicillin 2 g IV q 4 h IF > 50 yrs, Alcoholic, Pregnant, Immunocompromised

ADD
Acyclovir 10 mg / kg / dose IV q 8 hrs IF HSV suspected (negative gram stain, seizure)

2, CORTICOSTEROIDS
before or at the time of antibiotics if S. Pneumonea is suspected

Adult: Dexamethasone 10 mg IV q 6 h x 4 days
Children: Dexamethasone 0.6 mg / kg / d divided q 6 h x 4 days

3. INVESTIGATIONS
   CBC, Blood Cultures x 2 prior to antibiotics

LUMBAR PUNCTURE
LP Contraindications
Infection at the site of the LP
Coagulation abnormalities
Risk of brain herniation

Risk / Benefits:
Post LP Headache - occurs in 10-30%
Infection
Bleeding
Back pain or radicular pain or numbness

CSF opening pressure (if done in left lateral decubitus)

Normal Opening Pressure: 50 - 200 mmH20

Tube 1 - cell count, gram stain, xanthocromia

Tube 2 - protein, glucose

Tube 3 - culture & sensitivity, viral studies

Tube 4 - cell count

CT HEAD

Altered mental status (GCS<10)

CNS Disease (CSF Shunt, Hydrocephalus, mass lesion, stroke, or focal infection)

Focal neurological deficit (excluding cranial nerve palsies)

Papilledema

Seizure (new onset within 1 week)

Immunocompromised (HIV, immunosuppressive therapy)

CLINICAL FEATURES
95% of patients have 2/4 features:
Neck stiffness (Se 70%)
Headache (Se 50%)
Fever (>38 C) OR hypothermia
Altered mental status
Photosensitivity

RISK FACTORS
Age: ≥65 years old, Neonates

Aboriginal groups, Students living in residence

PMHx: Immunocompromised (16%): HIV, DM; hepatic / renal failure; Comorbid Infection: otitis media or sinusitis (25%), mastoiditis, Pneumonia (12%), Endocarditis, Dental Infection

Recent neurosurgery, Head trauma, shunts

Recent travel to area with endemic meningococcal disease (eg. sub-Saharan Africa)

Alcoholism, IVDU

MENINGEAL IRRITATION MANEUVERS
Lay patient flat, no pillows
Lift head, hold for 10 seconds to examin for neck stiffness
Jolt accentuation (Sn 6% Sp 98.9%)
Accentuation of headache by horizontal rotation of the head at a frequency of two to three times per second
Brudzinski (Sn 11%, Sp 93.4%)
Spontaneous flexion of the hips during attempted passive flexion of the neck
Kernig’s (Sn 14.1%, Sp 92.3%)
Inability or reluctance to allow full extension of the knee when the hip is flexed 90 degrees
Nuchal Rigidity (Sn 39.4%, Sp 70.3%)

Peticial Rash (63% meningococcal meningitis)

ISOLATE PATIENT:
Droplet Precautions

N. Meningitidis

Indications: Close contact (> 8 hrs), contact with oral secretions

PROPHYLAXIS
Rifampin
Adults: 600 mg PO q 12 hrs x 2 d
Children: 5-10 mg / kg PO q 12 hrs x 2 d

H. Influenza
Indications: Living in household with >= 1 unvaccinated or incompletely vaccinated child age < 4 yrs old

Rifampin 20 mg / kg / d (max 600 mg / d) for 4 days

Group B Strep in Pregnancy
Indications:
Previous baby with group B Strep Infection
Colonization of the perineum or rectal area at 35 - 37 wk GA
Bacterium in pregnancy high risk features: ROM > 18 h, preterm delivery (<37 wk GA)

Question 3

DDX: CNS INFECTIONS

Answer 3

Meningitis
-fungal
-tubercular

Encephalitis
-HSV
-Arbovirus

Brain Abscess

Cerebral Malaria

Epidural Abscess

Question 4

CSF FINDINGS

Answer 4

Bacterial: Turbid, WBC>1000/mm3, ↓Glucose ↑↑Protein, 80-90% neutrophils, +gram stain

Viral: Clear, WBC 10-500/mm3, Nml glucose, Nml protein, -gram stain

TRUE CSF WBC = measured CSF WBC [(CSF RBC x serum WBC)/serum RBC]