Brain Abscess

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For further information, see CMDT Part 24-09: Intracranial & Spinal Mass Lesions

Key Features

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Essentials of Diagnosis

Symptoms and signs of expanding intracranial mass
There may be signs of a primary infection or of congenital heart disease
Fever may be absent

General Considerations

Presents as an intracranial space-occupying lesion
May occur as a sequela of ear or sinus infection, a complication of infection elsewhere in the body, or an infection introduced intracranially by trauma or surgical procedures
Most common infective organisms
- Streptococci
- Staphylococci
- Anaerobes
Mixed infections also occur

Clinical Findings

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Symptoms and Signs

Early symptoms
- Headache
- Drowsiness
- Inattention
- Confusion
- Seizures
Later signs
- Increasing intracranial pressure
- Focal neurologic deficits
There may be little or no systemic evidence of infection

Differential Diagnosis

Other rapidly expanding intracranial space-occupying lesions

Diagnosis

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Laboratory Tests

Examination of the cerebrospinal fluid does not help in diagnosis and lumbar puncture may precipitate herniation
Peripheral leukocytosis sometimes present

Imaging Studies

CT scan of the head characteristically shows an area of contrast enhancement surrounding a low-density core (similar to metastatic neoplasms)
MRI permits earlier recognition of focal cerebritis or abscess

Diagnostic Procedures

Stereotactic needle aspiration may enable a specific etiologic organism to be identified

Treatment

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Medications

Intravenous antibiotics, combined with surgical drainage (aspiration or excision) if necessary to reduce the mass effect, or to establish the diagnosis
Broad-spectrum antibiotics are used if the infecting organism is unknown (Table 30–5)
Initial empiric antibiotic regimens typically include
- Ceftriaxone, 2 g intravenously every 12 hours
- Metronidazole, 15 mg/kg intravenous loading dose, followed by 7.5 mg/kg intravenously every 6 hours
- Vancomycin, 1 g intravenously every 12 hours
Antimicrobial treatment is usually continued parenterally for 6–8 weeks and is followed by oral treatment for certain infections, such as nocardiosis, actinomycosis, fungal infections, and tuberculosis
Dexamethasone (4–25 mg orally four times daily, depending on severity, followed by tapering of dose, depending on response) may reduce any associated edema; intravenous mannitol is sometimes required

Table 30–5.Examples of initial antimicrobial therapy for acutely ill, hospitalized adults pending identification of causative organism (in alphabetical order).

View Table||Download (.pdf)

Table 30–5. Examples of initial antimicrobial therapy for acutely ill, hospitalized adults pending identification of causative organism (in alphabetical order).

Suspected Clinical Diagnosis

Likely Etiologic Diagnosis

Medication of Choice

Brain abscess

Mixed anaerobes, pneumococci, streptococci

Ceftriaxone, 2 g intravenously every 12 hours plus metronidazole, 500 mg orally every 8 hours plus vancomycin, 15 mg/kg intravenously every 8 hours

Endocarditis, acute (including injection drug user)

S aureus, E faecalis, viridans streptococci

Vancomycin, 15 mg/kg/dose intravenously every 12 hours

Fever in neutropenic patient receiving cancer chemotherapy

S aureus, Pseudomonas, Klebsiella, E coli

Cefepime, 2 g intravenously every 8 hours

Intra-abdominal sepsis (eg, postoperative, peritonitis, cholecystitis)

Gram-negative bacteria, Bacteroides, anaerobic bacteria, enterococcus

Piperacillin-tazobactam, 4.5 g intravenously every 6–8 hours, or ertapenem, 1 g every 24 hours

Meningitis, bacterial, age > 50, community-acquired

Pneumococcus, meningococcus, Listeria monocytogenes,¹ gram-negative bacilli, group B streptococcus

Ampicillin, 2 g intravenously every 4 hours, plus ceftriaxone, 2 g intravenously every 12 hours, plus vancomycin, 15 mg/kg intravenously every 8 hours

Meningitis, bacterial, community-acquired

Streptococcus pneumoniae (pneumococcus),² Neisseria meningitidis (meningococcus)

Ceftriaxone, 2 g intravenously every 12 hours,¹ plus vancomycin, 15 mg/kg intravenously every 8 hours

Meningitis, postoperative (or posttraumatic)

S aureus, gram-negative bacilli, coagulase-negative staphylococci, diphtheroids (eg, Propionibacterium acnes) (uncommon) pneumococcus (in posttraumatic)

Vancomycin, 15 mg/kg intravenously every 8 hours, plus cefepime, 3 g intravenously every 8 hours³

Osteomyelitis

S aureus, secondarily gram-negative aerobes

Vancomycin 15 mg/kg intravenously every 8 hours plus ceftriaxone 2 g intravenously every 24 hours

Pneumonia, acute, community-acquired, non-ICU hospital admission

Pneumococci, M pneumoniae, Legionella, C pneumoniae

Ceftriaxone, 1 g intravenously every 24 hours or ampicillin-sulbactam 1.5–3 g intravenously every 6 hours) plus azithromycin, 500 mg intravenously every 24 hours; or a respiratory fluoroquinolone⁴ alone

Pneumonia, postoperative or nosocomial

S aureus, mixed anaerobes, gram-negative bacilli

Cefepime, 2 g intravenously every 8 hours; or ceftazidime, 2 g intravenously every 8 hours; or piperacillin-tazobactam, 4.5 g intravenously every 6–8 hours; or imipenem, 500 mg intravenously every 6 hours; or meropenem, 1 g intravenously every 8 hours plus tobramycin, 5–7 mg/kg intravenously every 24 hours; or ciprofloxacin, 400 mg intravenously every 12 hours; or levofloxacin, 500 mg intravenously every 24 hours plus vancomycin, 15 mg/kg/dose intravenously every 12 hours

Pyelonephritis with flank pain and fever (recurrent urinary tract infection)

E coli, Klebsiella, Enterobacter, Pseudomonas

Ceftriaxone, 1 g intravenously every 24 hours; or if culture results confirm susceptibility, ciprofloxacin, 400 mg intravenously every 12 hours (500 mg orally); or levofloxacin, 500 mg once daily (intravenously/orally)

Septic arthritis

S aureus, N gonorrhoeae

Ceftriaxone, 1–2 g intravenously every 24 hours

Septic thrombophlebitis (eg, IV tubing, IV shunts)

S aureus, gram-negative aerobic bacteria

Vancomycin, 15 mg/kg/dose intravenously every 12 hours, plus ceftriaxone, 1 g intravenously every 24 hours

¹TMP-SMZ can be used to treat Listeria monocytogenes in patients allergic to penicillin in a dosage of 15–20 mg/kg/day of TMP in three or four divided doses.

²Including penicillin nonsusceptible isolates.

³Cefepime 3 g is a higher dose than sometimes recommended in order to optimize treatment of Pseudomonas and Enterobacter.

⁴Levofloxacin 750 mg/day, moxifloxacin 400 mg/day.

Outcome

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Follow-Up

Monitor patient by serial CT scans or MRI every 2 weeks and at deterioration

Complications

Seizures
Focal neurologic deficits

Prognosis

Abscesses < 2 cm can often be cured medically

When to Admit

When the diagnosis is suspected

Reference

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Chow F. Brain and spinal epidural abscess. Continuum (Minneap Minn). 2018 Oct;24(5):1327–48.
[PubMed: 30273242]

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Citation

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Key Features

Essentials of Diagnosis

General Considerations

Clinical Findings

Symptoms and Signs

Differential Diagnosis

Diagnosis

Laboratory Tests

Imaging Studies

Diagnostic Procedures

Treatment

Medications

Outcome

Follow-Up

Complications

Prognosis

When to Admit

Reference

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