Study guide
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess
ABIM Critical Care Medicine Study Guide Exam
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1 Chapter 1: Exam Orientation: Format, Blueprint & Study Strategy
1.1 ABIM Critical Care Medicine Exam: Format, Blueprint & Study Strategy
2 Chapter 2: Acute Respiratory Failure & ARDS
2.1 ARDS Definition, Pathophysiology & Phenotypes 2.2 Lung-Protective Mechanical Ventilation 2.3 Refractory ARDS: Prone Positioning, Neuromuscular Blockade & VV-ECMO
3 Chapter 3: Obstructive Airways, Pulmonary Vascular & Pleural Emergencies
3.1 Severe Asthma & COPD Exacerbations in the ICU 3.2 Massive & Submassive Pulmonary Embolism 3.3 Pulmonary Hypertension & Right Ventricular Failure in the ICU 3.4 Massive Hemoptysis, Complex Pleural Effusions & Thoracic Drainage
4 Chapter 4: Airway, Parenchymal & Nonthrombotic Pulmonary Emergencies
4.1 Airway Management, Upper-Airway Obstruction & Artificial-Airway Complications 4.2 Diffuse Alveolar Hemorrhage, Interstitial Lung Disease, Pulmonary Vasculitis & Noncardiogenic Edema 4.3 Severe Community-Acquired & Viral Pneumonia 4.4 Nonthrombotic Embolism (Air, Fat, Amniotic Fluid, Tumor, Septic) & Acute Chest Syndrome
5 Chapter 5: Mechanical Ventilation Modes, Dyssynchrony & Liberation
5.1 Mechanical Ventilator Modes & Advanced Breath Delivery 5.2 Patient-Ventilator Dyssynchrony & Waveform Analysis 5.3 Ventilator Liberation, Spontaneous Breathing Trials & Post-Extubation Support
6 Chapter 6: Shock Syndromes & Hemodynamic Principles
6.1 Shock Classification, Cellular Pathophysiology & Biomarkers 6.2 Hemodynamic Monitoring: Arterial Lines, CVP & Pulmonary Artery Catheter 6.3 Dynamic Assessment of Fluid Responsiveness & Resuscitation Targets
7 Chapter 7: Vasoactive Therapies & Mechanical Circulatory Support
7.1 Vasopressors & Inotropes: Pharmacology & Clinical Titration 7.2 Temporary Mechanical Circulatory Support: IABP, Impella & TandemHeart 7.3 Venoarterial ECMO (VA-ECMO) & Differential Hypoxemia 7.4 Post-Cardiac Arrest Care, Targeted Temperature Management & Neuroprognostication
8 Chapter 8: Acute Kidney Injury & Renal Replacement Therapy
8.1 KDIGO AKI Classification, Etiologies & Diagnostic Evaluation 8.2 Continuous Renal Replacement Therapy (CRRT) vs Intermittent Hemodialysis 8.3 Indications & Timing for RRT in Critical Illness: AKIKI & STARRT-AKI
9 Chapter 9: Electrolyte, Acid-Base & Endocrine Emergencies
9.1 Severe Dysnatremias: Hyponatremia, Hypernatremia & Osmotic Demyelination 9.2 Potassium, Calcium, Magnesium & Phosphate Disorders 9.3 Complex & Mixed Acid-Base Disorders: Boston vs Copenhagen vs Stewart 9.4 Endocrine Crises: DKA, HHS, Thyroid Storm, Myxedema Coma & Adrenal Crisis
10 Chapter 10: Glycemic Control, Hyperammonemia, Pituitary & Adrenal Disorders
10.1 ICU Glycemic Control & Severe Hypoglycemia 10.2 Non-Hepatic Hyperammonemia & Metabolic Encephalopathy 10.3 Pituitary Emergencies, Adrenal Excess & Critical Illness-Related Corticosteroid Insufficiency
11 Chapter 11: Acute Coronary Syndromes & Cardiac Arrhythmias
11.1 Acute Coronary Syndromes & Mechanical Complications of Myocardial Infarction 11.2 Critical Tachyarrhythmias: Atrial Fibrillation with RVR, VT & VF 11.3 Critical Bradyarrhythmias, Conduction Blocks & Temporary Cardiac Pacing
12 Chapter 12: Acute Heart Failure, Valvular & Pericardial Emergencies
12.1 Acute Decompensated Heart Failure & Cardiogenic Pulmonary Edema 12.2 Acute Valvular Regurgitation & Prosthetic Valve Emergencies 12.3 Pericardial Tamponade & Acute Aortic Syndromes
13 Chapter 13: Myocardial Disease, Hypertensive & Cardiac Device Emergencies
13.1 Fulminant Myocarditis, Stress & Peripartum Cardiomyopathy, and Hypertrophic Cardiomyopathy 13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm 13.3 Implanted Cardiac Devices, LVAD Emergencies & Electrical Storm
14 Chapter 14: Sepsis & Systemic Infectious Diseases
14.1 Sepsis-3 Definitions & Surviving Sepsis Campaign 2026 Guidelines 14.2 Refractory Septic Shock & Adjunctive Therapies 14.3 Multidrug-Resistant Pathogens & Antimicrobial Stewardship in the ICU
15 Chapter 15: ICU-Acquired & Severe Focal Infections
15.1 Hospital-Acquired & Ventilator-Associated Pneumonia 15.2 Central Line-Associated Bloodstream Infections & Catheter-Associated UTIs 15.3 Intra-Abdominal Sepsis, Necrotizing Soft Tissue Infections & CNS Infections
16 Chapter 16: Focal, Special-Host & Systemic Infections
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess 16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections 16.3 Infective Endocarditis, Device Infections & Other Focal Cardiovascular Infections 16.4 Antimicrobial Pharmacokinetics, Allergy, Toxicity & Infection Prevention 16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses
17 Chapter 17: Neurocritical Care & Coma
17.1 Coma, Altered Mental Status & Acute Delirium in the ICU 17.2 Status Epilepticus & Non-Convulsive Status Epilepticus 17.3 Acute Ischemic Stroke & Intracranial Hemorrhage
18 Chapter 18: Cerebrovascular Syndromes, Encephalopathy & Withdrawal States
18.1 Cerebral Venous Sinus Thrombosis, PRES & Reversible Cerebral Vasoconstriction Syndrome 18.2 Alcohol & Sedative Withdrawal, Wernicke Encephalopathy & Drug-Induced Encephalopathy
19 Chapter 19: Intracranial Hypertension & Neuromuscular Weakness
19.1 Intracranial Pressure Monitoring, Cerebral Perfusion & Tiered ICP Management 19.2 Acute Neuromuscular Respiratory Failure, ICU-Acquired Weakness & Brain Death Determination
20 Chapter 20: Traumatic Brain Injury, Spinal Cord Injury & Toxin-Mediated Paralysis
20.1 Traumatic Brain Injury Management & Paroxysmal Sympathetic Hyperactivity 20.2 Acute Spinal Cord Injury, Neurogenic Shock & Autonomic Dysreflexia 20.3 Toxin-Mediated Paralysis & Neuromuscular Crises: Botulism, Tetanus, Tick Paralysis & Myasthenic Crisis
21 Chapter 21: Gastrointestinal, Hepatic & Abdominal Emergencies
21.1 Acute Upper & Lower Gastrointestinal Bleeding in the ICU 21.2 Acute Liver Failure & Severe Acute Pancreatitis 21.3 Abdominal Compartment Syndrome & Acute Mesenteric Ischemia
22 Chapter 22: Luminal GI Emergencies & Complications of Cirrhosis
22.1 Esophageal, Gastric & Bowel Emergencies: Perforation, Obstruction, Ogilvie Syndrome & Colonic Ischemia 22.2 Complications of Cirrhosis: Alcohol-Associated Hepatitis, Hepatorenal Syndrome & Pulmonary Vascular Syndromes
23 Chapter 23: Trauma, Burns & Perioperative Critical Care
23.1 Polytrauma Resuscitation, Damage Control & Massive Transfusion 23.2 Severe Burn Injury, Inhalation Injury & Environmental Emergencies 23.3 Perioperative Critical Care for High-Risk Surgical Patients
24 Chapter 24: Thoracic Trauma, Environmental Injury & Obstetric Critical Care
24.1 Thoracic Trauma: Flail Chest, Pulmonary Contusion, Great Vessel & Tracheobronchial Injury 24.2 Environmental Injury: Drowning, Diving, Altitude, Heat, Cold, Electrical & Radiation 24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy
25 Chapter 25: Transplantation, Donor Management & Post-Cardiac Surgery Care
25.1 Solid Organ Transplant Recipients & Deceased Donor Management 25.2 Post-Cardiac Surgery Critical Care: Bleeding, Tamponade, Low Output & Vasoplegia
26 Chapter 26: Hematologic Emergencies, Toxicology, Critical Ultrasound & ICU Liberation
26.1 Hematologic Emergencies in the ICU: HIT, DIC, TMA & Anticoagulant Reversal 26.2 Critical Care Toxicology, Toxidromes & Specific Antidotes 26.3 Critical Care Point-of-Care Ultrasound (POCUS) 26.4 ICU Liberation, Analgosedation, Goals of Care & Critical Care Ethics
27 Chapter 27: Transfusion Medicine, Hematologic & Oncologic Disorders
27.1 Transfusion Medicine: Products, Thresholds, Reactions & Apheresis 27.2 Red and White Cell Disorders, Hemoglobinopathies, Factor Deficiencies & Hypercoagulable States 27.3 Oncologic Emergencies, Hematopoietic Cell Transplant Complications & Cellular Therapy Toxicity
28 Chapter 28: Clinical Pharmacology, Adverse Drug Reactions & Specific Poisonings
28.1 Pharmacokinetic Principles, Dose Adjustment & Drug Interactions in Critical Illness 28.2 Adverse Drug Reactions: Anaphylaxis, Severe Cutaneous Reactions & Hyperthermic Syndromes 28.3 Specific Poisonings: Sodium-Channel Blockers, Lithium, Valproate, Theophylline, Iron, Sulfonylureas & Methemoglobinemia
29 Chapter 29: Ethics, Research Methods, Administration & Abdominal Ultrasound
29.1 Advance Care Planning, Nonbeneficial Treatment, Informed Consent & Confidentiality 29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement 29.3 Abdominal, Vascular & Procedural Point-of-Care Ultrasound
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess
Key Takeaways Explain This Topic AI
Start intravenous acyclovir 10 mg/kg every 8 hours for suspected herpes simplex encephalitis before results return; a negative CSF HSV PCR within the first 72 hours should be repeated rather than trusted.
Autoimmune encephalitis (notably anti-NMDA receptor) presents with psychiatric change, seizures, dyskinesias, and autonomic instability and is treated with steroids, IVIG or plasma exchange, and tumor removal.
Cryptococcal meningitis management depends on controlling intracranial pressure with repeated large-volume lumbar punctures; induction is liposomal amphotericin B plus flucytosine.
Dexamethasone improves survival in tuberculous meningitis and is given with antituberculous therapy, in contrast to cryptococcal meningitis where steroids caused harm.
Spinal epidural abscess classically presents with back pain, fever, and neurologic deficit; urgent MRI with contrast and surgical decompression preserve function.
Last updated: October 2026
Viral Encephalitis
Encephalitis is parenchymal brain inflammation, so altered consciousness, seizures, and focal deficits dominate, in contrast to the meningeal signs of meningitis. Many patients have features of both.
Herpes Simplex Virus (HSV-1)
The most common sporadic cause of fatal encephalitis in adults.
Features : fever, confusion progressing over days, personality change, aphasia, olfactory or gustatory hallucinations, and temporal lobe seizures .
Imaging : MRI shows temporal and inferior frontal lobe signal change, often hemorrhagic; CT is frequently normal early.
CSF : lymphocytic pleocytosis, elevated protein, normal glucose, and often red blood cells . EEG may show periodic lateralized epileptiform discharges over a temporal lobe.
Diagnosis : CSF HSV PCR has high sensitivity, but can be falsely negative in the first 72 hours . Repeat it if the clinical picture fits.
Treatment : acyclovir 10 mg/kg IV every 8 hours for 14 to 21 days , started empirically. Each hour of delay worsens outcome. Maintain hydration, because acyclovir causes crystal nephropathy, and adjust the dose for kidney function. Neurotoxicity (confusion, myoclonus) occurs with excessive levels.
Other Important Causes
- Agent Clues
- Varicella zoster virus Vasculopathy with stroke, cerebellitis, often with or after rash; treat with acyclovir
- West Nile virus Summer mosquito exposure; poliomyelitis-like flaccid paralysis , tremor, parkinsonism
- Enteroviruses Younger patients, summer and fall; usually self-limited
- Rabies Animal exposure, hydrophobia, agitation alternating with lucidity; nearly always fatal once symptomatic
- HIV Acute seroconversion illness, or opportunistic processes in advanced disease
- Measles, JC virus, prion disease Subacute to chronic courses
- Naegleria fowleri Freshwater diving; fulminant amebic meningoencephalitis; miltefosine-based regimen
- Toxoplasma Advanced HIV with ring-enhancing lesions; pyrimethamine, sulfadiazine, leucovorin
- Cerebral malaria Travel to an endemic area with P. falciparum ; IV artesunate
- Autoimmune Encephalitis
Suspect it in younger patients with subacute psychiatric symptoms, memory loss, seizures, orofacial dyskinesias, and autonomic instability.
Anti-NMDA receptor encephalitis is associated with ovarian teratoma and with preceding HSV encephalitis.
Diagnosis : serum and CSF autoantibody panels, MRI, EEG (an "extreme delta brush" pattern in some cases), and tumor screening.
Treatment : corticosteroids plus IVIG or plasma exchange, then rituximab or cyclophosphamide; remove the tumor. ICU care often involves prolonged ventilation, status epilepticus, and dysautonomia.
Brain Abscess
Routes : contiguous spread (otitis, sinusitis, dental infection), hematogenous seeding (endocarditis, lung abscess, right-to-left shunt), and direct inoculation (trauma, surgery).
Organisms : streptococci (including the Streptococcus anginosus group) and anaerobes, often polymicrobial; S. aureus after trauma or surgery; Nocardia , Toxoplasma , and fungi in immunocompromised hosts; Listeria in cell-mediated immune deficiency.
Presentation : headache (the most common symptom), fever in only about half, focal deficits, and seizures. Classic meningitis signs are often absent.
Imaging : a ring-enhancing lesion with central restricted diffusion on MRI, which helps distinguish abscess from tumor.
Management :
Aspiration or excision for lesions larger than about 2.5 cm, for diagnosis, or when there is mass effect. Stereotactic aspiration gives microbiologic diagnosis with low morbidity.
Empiric antibiotics : a third-generation cephalosporin plus metronidazole, adding vancomycin after trauma or surgery, for 6 to 8 weeks with imaging follow-up.
Avoid lumbar puncture when there is a mass lesion with mass effect.
Corticosteroids are reserved for significant edema and mass effect, because they impair capsule formation and antibiotic penetration.
Antiepileptic drugs for seizures; search for and treat the source, including a patent foramen ovale or pulmonary arteriovenous malformation in cryptogenic cases.
Spinal Epidural Abscess
Risk factors : injection drug use, diabetes, bacteremia, spinal instrumentation or injection, and epidural catheters.
Classic triad : back pain, fever, and neurologic deficit , but the complete triad is uncommon at presentation. Pain is usually severe and focal, with percussion tenderness.
Progression : back pain, then radicular pain, then weakness and bladder dysfunction, then paralysis. Once paralysis is established, recovery is poor, so the window is early.
Diagnosis : MRI with contrast of the whole spine (skip lesions occur), blood cultures, ESR and CRP. S. aureus causes most cases.
Treatment : urgent surgical decompression and drainage plus 6 weeks or more of antibiotics (vancomycin plus a third- or fourth-generation cephalosporin empirically). Medical management alone is considered only for patients without deficits, with an identified organism and close monitoring.
Cryptococcal Meningitis
Host : advanced HIV (CD4 below 100 cells/µL), transplant recipients, cirrhosis, and sometimes apparently normal hosts ( C. gattii ).
Presentation : subacute headache, fever, and cranial neuropathies. Raised intracranial pressure drives morbidity.
Diagnosis : cryptococcal antigen in serum and CSF, India ink, and fungal culture. Measure and record the opening pressure at lumbar puncture.
Treatment :
Induction : liposomal amphotericin B plus flucytosine (a single high dose of liposomal amphotericin B with 14 days of flucytosine and fluconazole is an accepted regimen in resource-limited settings), followed by consolidation and maintenance fluconazole.
Pressure control is as important as the antifungal : repeat large-volume lumbar punctures daily while opening pressure is above 25 cmH2O, with a lumbar drain or shunt for refractory pressure.
Corticosteroids are harmful in HIV-associated cryptococcal meningitis (a trial showed more adverse events and disability).
Delay or carefully time antiretroviral therapy (usually after about 4 to 6 weeks) to reduce immune reconstitution inflammatory syndrome.
Tuberculous Meningitis
Presentation : subacute headache, fever, and cranial nerve palsies (especially cranial nerve VI), with basal meningeal enhancement, hydrocephalus, and infarcts from vasculitis.
CSF : lymphocytic pleocytosis, very high protein , low glucose. Acid-fast smear has low yield; nucleic acid amplification (Xpert MTB/RIF Ultra) and large-volume culture improve detection.
Treatment : standard four-drug therapy with adjunctive dexamethasone , which improves survival. Treat for 9 to 12 months, watch for drug-induced hepatitis, and manage hydrocephalus with CSF diversion.
Note
The pattern to remember: steroids help in bacterial meningitis (pneumococcal) and tuberculous meningitis, and harm in cryptococcal meningitis.