CSF Analysis: Infection, Inflammation & Hemorrhage

ABPN Neurocritical Care Study Guide Exam

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1 Chapter 1: Neurologic Examination & Coma Assessment in the ICU

Current Examination, Blueprint & Preparation Neurologic Examination in Critically Ill Patients Coma Evaluation & Consciousness Alterations Delirium & Toxic-Metabolic Encephalopathy in the ICU

2 Chapter 2: Cerebral Physiology & Intracranial Dynamics

Cerebral Blood Flow, Metabolism & Autoregulation Intracranial Pressure & Compliance Cerebral Edema & Herniation Syndromes

3 Chapter 3: Intracranial Hypertension & Cerebral Perfusion Management

Tiered ICP Management Protocols Hyperosmolar Therapy & Fluid Management Advanced & Refractory ICP Interventions

4 Chapter 4: Airway, Mechanical Ventilation & Pulmonary ICU Management

Emergency Airway Management & Neuro-Intubation Mechanical Ventilation Strategies in Acute Brain Injury Tracheostomy & Ventilator Weaning in Neurocritical Care Pulmonary Complications in the Neuro-ICU Obstructive Lung Disease, Pulmonary Hypertension & Bronchoscopy

5 Chapter 5: Hemodynamics, Shock & Cardiovascular Management

Hemodynamic Monitoring & Blood Pressure Targets Vasoactive Agents: Inotropes, Vasopressors & Antihypertensives Cardiac Complications of Brain Injury

6 Chapter 6: Neuropharmacology, Analgesia & Sedation

ICU Sedation & Analgesia Neuromuscular Blockade & Monitoring Propofol Infusion Syndrome & Drug Toxicities Antiseizure Drug Pharmacology in the ICU

7 Bleeding, Thrombosis & Hematologic Emergencies

Warfarin & Heparin Reversal Direct Oral Anticoagulant (DOAC) Reversal Antiplatelet Management & Platelet Dysfunction Venous Thromboembolism Prophylaxis & Management Transfusion, Coagulopathy, TMA & Cellular-Therapy Neurotoxicity

8 Chapter 8: Systemic ICU Care, Fluids, Electrolytes & Endocrine

Hyponatremia & Osmoregulation: SIADH vs Cerebral Salt Wasting Diabetes Insipidus, Hypernatremia & Endocrine Crises Critical Care Prophylaxis, Nutrition & Infection Prevention

9 Systemic Trauma & Environmental Injury

Polytrauma, Chest Injury & Abdominal Hemorrhage Burns, Electrical Injury & Hanging

10 Cardiac Emergencies & Mechanical Support

IABP, Ventricular Devices & ECMO Acute Coronary, Valvular, Rhythm & Aortic Emergencies

11 Kidney Injury, Acid–Base & Renal Replacement

Acute Kidney Injury & Renal Drug Clearance Acid–Base Disorders, Electrolytes & Renal Replacement

12 Systemic Infection & Endocrine Emergencies

Sepsis, Endocarditis & Antimicrobial Principles Thyroid, Adrenal & Dysglycemic Emergencies

13 Gastrointestinal & Hepatic Emergencies

Acute Abdomen, GI Bleeding & Abdominal Compartment Syndrome Acute Liver Failure, Cirrhosis & Hepatic Drug Effects

14 Chapter 9: Neuroimaging in the Neuro-ICU

Non-Contrast CT & CT Angiography CT Perfusion & Advanced Perfusion Imaging Magnetic Resonance Imaging in Critical Illness

15 Chapter 10: Electrophysiology & Neuromonitoring

Continuous EEG & ACNS Standardized Critical Care Terminology Invasive Neuromonitoring: ICP & External Ventricular Drains Multimodal Monitoring: PbtO2, Microdialysis & Transcranial Doppler

16 Angiography, Electrodiagnosis & CSF Analysis

Conventional Angiography & Cranial–Spinal Shunts EMG, Nerve Conduction & Acute Muscle Disease CSF Analysis: Infection, Inflammation & Hemorrhage

17 Chapter 11: Bedside Procedures, Ultrasound & Death by Neurologic Criteria

Critical Care Procedural Skills Critical Care Ultrasound & Echocardiography Determination of Death by Neurologic Criteria

18 Chapter 12: Acute Ischemic Stroke & Reperfusion Therapies

Acute Ischemic Stroke Management & Thrombolysis Endovascular Thrombectomy & Large Vessel Occlusion Malignant Hemispheric & Cerebellar Infarction

19 Chapter 13: Spontaneous Intracerebral Hemorrhage & Intraventricular Hemorrhage

Acute Intraparenchymal Hemorrhage Management Intraventricular Hemorrhage & Hydrocephalus Surgical Evacuation & Minimally Invasive Surgery in ICH

20 Chapter 14: Aneurysmal Subarachnoid Hemorrhage & Delayed Cerebral Ischemia

Aneurysmal Subarachnoid Hemorrhage: Acute Resuscitation & Securing Delayed Cerebral Ischemia & Cerebral Vasospasm Non-Aneurysmal Subarachnoid Hemorrhage & Vascular Malformations

21 Venous, Spinal & Traumatic Vascular Disease

Cerebral Venous Thrombosis & Spinal Cord Infarction Traumatic Dissection, Carotid–Cavernous Fistula & Penetrating Injury

22 Chapter 15: Traumatic Brain & Spinal Cord Injury

Severe Traumatic Brain Injury & Contusions Acute Traumatic Spinal Cord Injury & Neurogenic Shock Spine Trauma, Fractures & Cord Syndromes

23 Chapter 16: Status Epilepticus, Seizures & Neuromuscular Emergencies

Status Epilepticus: Convulsive & Non-Convulsive Refractory & Super-Refractory Status Epilepticus Acute Neuromuscular Respiratory Failure

24 Chapter 17: Post-Cardiac Arrest Care, CNS Infections & Encephalitis

Targeted Temperature Management & Post-Cardiac Arrest Care Post-Cardiac Arrest Neuroprognostication Acute CNS Infections, Encephalitis & Inflammatory Emergencies

25 Neuroinflammation & Neurooncology

Fulminant Demyelination & Autoimmune Encephalitis Brain, Spinal & Leptomeningeal Cancer Emergencies

26 Pregnancy, Transplantation & Pediatric Care

Pregnancy, Postpartum & Post-Transplant Neurologic Care Pediatric Neurocritical Care

27 Chapter 18: Neurosurgical & Perioperative Emergencies

Postoperative Neurosurgical Complications Device Complications: EVDs, Shunts & ICP Monitors Cerebral Hyperperfusion Syndrome & Post-Interventional Emergencies

28 Chapter 19: Ethics, Palliative Care & Organ Donation in the Neuro-ICU

Communication, Surrogate Decision-Making & Conflict Resolution Neuroprognostication Ethics, Withdrawal of Life Support & Palliative Care Organ Donation & Management of the Deceased Donor

CSF Analysis: Infection, Inflammation & Hemorrhage

Key Takeaways Explain This Topic AI

Assess LP safety and do not delay indicated empirical treatment while waiting for an unsafe or delayed procedure.

Interpret CSF glucose with serum glucose and cell counts, protein, microbiology, timing, and host immune status.

RBC clearing between tubes does not reliably exclude SAH, and CSF D-dimer is not a standard definitive discriminator.

Normal or mildly abnormal CSF does not exclude early infection, treated infection, or infection in an immunocompromised patient.

Last updated: October 2026

Define the Clinical Question Before Sampling

Cerebrospinal fluid (CSF) can help diagnose infection, inflammatory disease, malignancy, and selected hemorrhagic presentations. The useful question is not simply whether the fluid is abnormal. Decide which diagnoses are plausible, whether LP is safe, what tests are needed, and whether treatment must begin first. The outline also requires CSF physiology: fluid circulates from the lateral ventricles through the third and fourth ventricles into subarachnoid spaces and is cleared through multiple pathways, including arachnoid and lymphatic routes. Obstruction or impaired absorption can cause hydrocephalus.

Typical adult CSF volume is roughly 150 mL, and daily production is about 500 mL, but these approximations do not establish a safe drainage volume for an individual patient. CSF pressure depends on position, venous pressure, obstruction, and intracranial pathology. A lumbar pressure measurement cannot be interpreted as a reliable whole-brain pressure when compartments are obstructed or a dangerous pressure gradient exists.

Safety and Specimen Planning

Evaluate for a mass lesion, obstructive hydrocephalus, relevant focal findings, papilledema, unstable physiology, local infection, and bleeding risks. Neuroimaging before LP is indicated in selected high-risk presentations rather than required before every uncomplicated suspected meningitis. A normal scan does not guarantee safety in every clinical situation. If antibiotics or acyclovir are indicated urgently, obtain blood cultures when feasible and treat without waiting for a delayed procedure.

Review anticoagulant exposure, platelet status, and the planned procedure with current institutional guidance. Drug-specific hold times depend on dose, renal function, urgency, and bleeding risk; one fixed 48-hour rule is inadequate for all DOACs. Platelet transfusion recommendations also differ by procedure and guideline. Do not treat a conventional neurosurgical target as an evidence-based universal LP threshold.

Read the Core CSF Profile

Component What it contributes Limitation

Opening pressure Supports pressure and infection assessment in a proper position Position, effort, sedation, and ventilation can affect it

Cell count and differential Characterizes inflammatory or hemorrhagic response Early, treated, or immunocompromised infection may be atypical

Protein Reflects barrier dysfunction and other processes Nonspecific; rises with blood contamination and many diseases

Glucose and serum comparison Low relative glucose suggests selected infections or malignancy Timing and serum changes affect interpretation

Culture, stains, PCR, antigen Addresses specific pathogens Prior therapy, timing, and assay coverage affect sensitivity

Bacterial meningitis often produces neutrophilic pleocytosis, increased protein, and low glucose, but no pattern is obligatory. Viral disease often has lymphocytes and relatively preserved glucose, while early viral infection can be neutrophilic. Tuberculous, fungal, and malignant processes may produce low glucose with lymphocytic inflammation. A routine multiplex panel does not test every organism or replace cultures and host-specific testing.

Targeted Infection and Immune Testing

HSV encephalitis can have an initially negative PCR early in disease. If clinical suspicion remains, continue appropriate treatment and consider repeat sampling at the recommended interval. Immunocompromised patients may require targeted studies for opportunistic infection. Device-associated ventriculitis can have difficult-to-interpret cell counts after hemorrhage or surgery; culture and the clinical course remain central, and normal routine parameters do not reliably exclude it.

For autoimmune encephalitis or demyelinating disease, choose serum and CSF studies appropriate to the suspected syndrome. Oligoclonal bands and IgG indices indicate intrathecal immune activity but are not unique to one diagnosis. Interpret antibody results with the phenotype, specimen, assay, and prior treatment. Cytology and flow cytometry may address malignancy; a negative initial sample can require reconsideration or repeat adequate sampling when safe.

Blood in CSF and Suspected SAH

A traumatic puncture and a true SAH can both produce many RBCs. Clearing between tubes is not sufficiently reliable to exclude SAH , and persistence alone does not prove an aneurysm. Xanthochromia reflects blood-breakdown pigments, with detection affected by time, specimen handling, and whether the laboratory uses visual inspection or spectrophotometry. Early absence does not settle a late-presenting or high-risk clinical question.

Do not use CSF D-dimer or a fixed tube-to-tube percentage as a definitive bedside discriminator. Integrate the headache history, timing and quality of CT, CSF findings, and appropriate vascular imaging. An abnormal LP does not by itself identify the bleeding source; a responsible neurovascular workup may still be necessary.

Abscess and Epidural Infection

A focal brain abscess or spinal epidural abscess may be better diagnosed with imaging and a source-control plan than with routine LP. Brain abscess can cause focal deficits, seizures, edema, and mass effect; spinal epidural infection can cause back pain, weakness, sensory change, or bladder dysfunction. Fever and the full classic symptom triad can be absent. MRI with appropriate contrast and diffusion sequences is valuable, and urgent surgical or neurosurgical assessment is indicated when compression, deterioration, or a drainable focus is present.

Obtain cultures when feasible, give appropriate antimicrobial therapy, and address the source. Steroids in brain abscess are reserved for selected severe edema or impending herniation, not routine treatment of every lesion. A patient with an epidural abscess and progressive weakness needs urgent imaging and source-control assessment rather than an LP that delays decompression.

Sources checked October 17, 2026: IDSA CNS infection guidance and ESCMID brain abscess guideline .