Study guide
25.2 Autoimmune Encephalitis and Acute Autonomic Hyperactivity (03.Q–R)
ABIM Neurocritical Care Subspecialty Certification Exam
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Eligibility, Practice Pathway, and the IM Training Route 1.3 Format, Scoring, Pearson VUE, and Score Reports 1.4 How to Use This Independent Study Guide
2 ICU Neurologic Exam, Cerebral Physiology, and CSF
2.1 Neurological Examination in the ICU 2.2 Cerebral Physiology, ICP, CBF, and Autoregulation 2.3 CSF Physiology
3 Core Neuropharmacology
3.1 Osmotic Agents 3.2 Anti-Seizure Drugs 3.3 Anesthetics, Sedatives, Analgesia, and Paralytics 3.4 Antihypertensives, Vasopressors, and Inotropes
4 Reperfusion Drugs, Airway, and Ventilation
4.1 Thrombolytics, Anticoagulants, and Antiplatelets 4.2 Reversal of Anticoagulation After Acute Hemorrhage 4.3 Airway Management and Tracheostomy 4.4 Mechanical Ventilation
5 Hemodynamics and Shock
5.1 Hemodynamic Monitoring 5.2 IABP, Temporary VADs, LVAD, and ECMO 5.3 Diagnosis and Management of Shock
6 Nutrition, Temperature, and ICU Prophylaxis
6.1 Nutrition (01.J) 6.2 Temperature Control (01.K) 6.3 ICU Prophylaxis, Delirium, and Early Mobility (01.L)
7 General Trauma
7.1 Emergency Evaluation of Polytrauma, Chest, and Abdominal Trauma 7.2 Long-Bone Fractures and Fat Embolism 7.3 Burns, Electrical Injury, and Hanging/Strangulation
8 Pulmonary Critical Care
8.1 Pulmonary Physiology and ARDS (01.N.1–2) 8.2 PE, Pneumonia, and Pulmonary Edema (01.N.3, 7–8) 8.3 COPD, Asthma, PAH, and Bronchoscopy Basics (01.N.4–6, 9)
9 Cardiovascular Critical Care
9.1 Cardiovascular Physiology, Stress Cardiomyopathy, ACS, and Valves 9.2 Arrhythmias and Pacing 9.3 Acute Aortic Dissection and Cardiac Ultrasound
10 Renal and Infectious Disease
10.1 AKI, RRT, and Renal Drug Dosing 10.2 Acid-Base and Electrolyte Disorders 10.3 Severe Sepsis, Septic Shock, and Infective Endocarditis 10.4 Antimicrobial Use and Infection in the Immunosuppressed
11 Endocrine and Salt-Water Disorders
11.1 Pituitary Apoplexy, DI, and Panhypopituitarism (01.R.1–4) 11.2 SIADH and Cerebral Salt Wasting (01.R.5–6) 11.3 Thyrotoxicosis, Myxedema, Adrenal Crisis, and Dysglycemia (01.R.7–9)
12 Gastrointestinal Critical Care
12.1 GI Physiology, Acute Abdomen, Bleed, Ileus, and Perforation (01.S.1–5) 12.2 Mesenteric Ischemia and Abdominal Compartment Syndrome (01.S.6–7) 12.3 Fulminant Liver Failure, Cirrhosis Decompensation, and Hepatic Dosing (01.S.8–10)
13 Hematologic Disorders
13.1 Anemia, Transfusion, Thrombocytopenia, Coagulopathy, and DIC (01.T.1–4) 13.2 VTE in the Neuro ICU (01.T.5) 13.3 Chemo/Immune, SCT, CAR-T, Sickle Cell, and TMA (01.T.6–10)
14 Neuroimaging
14.1 CT of Brain and Spine 14.2 MRI and CT/MR Perfusion 14.3 Noninvasive Angiography and Catheter Angiography
15 EEG, EMG, and CSF Analysis
15.1 EEG, Standard and Processed (02.B) 15.2 Basic EMG Interpretation (02.G) 15.3 CSF Analysis (02.H)
16 ICP, TCD, and Multimodality Monitoring
16.1 ICP Monitoring (02.C) 16.2 Transcranial Doppler (02.D) 16.3 Brain-Tissue Oxygen and Multimodality Monitoring (02.E–F)
17 Brain Death and Bedside Procedures
17.1 Brain Death Prerequisites and Clinical Exam (02.I) 17.2 Apnea Testing and Ancillary Studies (02.I) 17.3 Vascular Access, Thoracic Echo, and Lung Ultrasound (02.J–L)
18 Coma, Anoxia, and Intracranial Hypertension
18.1 Coma and Other States of Altered Consciousness (03.A) 18.2 Global Anoxia-Ischemia and Post-Resuscitation Encephalopathy (03.A.1) 18.3 Toxidromes, ICU Delirium, and Hypertensive Encephalopathy (03.A.2–4) 18.4 Intracranial Hypertension as a Disease State (03.B)
19 Acute Ischemic Stroke
19.1 IV Reperfusion Therapy (03.C.3) 19.2 Mechanical Thrombectomy Windows and Imaging Selection (03.C.3) 19.3 Malignant Hemispheric Infarction and Basilar Artery Occlusion (03.C.1–2)
20 Intraparenchymal Hemorrhage
20.1 Intracerebral Hematoma (03.D.1) 20.2 Cerebellar Hematoma (03.D.2) 20.3 Intraventricular Hemorrhage (03.D.3)
21 SAH, CVST, and Spinal Cord Infarction
21.1 Aneurysmal Subarachnoid Hemorrhage (03.E.1) 21.2 Non-Aneurysmal SAH (03.E.2) 21.3 Cerebral Venous Sinus Thrombosis (03.F) 21.4 Spinal Cord Infarction (03.G)
22 Vascular Anomalies and Traumatic Brain Injury
22.1 Unruptured Aneurysm, Cavernoma, AVM, and Dural AVF (03.H) 22.2 Diffuse Axonal Injury and Cerebral Contusions (03.I.1–2) 22.3 Epidural Hematoma, Subdural Hematoma, and Penetrating Injury (03.I.3–4, 7) 22.4 Arterial Dissection and Carotid-Cavernous Fistula (03.I.5–6)
23 Spine, Hydrocephalus, and CNS Infection
23.1 Spinal Cord Injury, Central Cord, and Neurogenic Shock (03.J) 23.2 Unstable Spine Fractures (03.K) 23.3 Hydrocephalus and CSF Diversion (03.L) 23.4 Acute CNS Infections (03.M)
24 Seizures and Neuromuscular Emergencies
24.1 Status Epilepticus and Seizures (03.N) 24.2 Guillain-Barré Syndrome (03.O.1) 24.3 Myasthenic Crisis (03.O.2) 24.4 Motor Neuron Disease, Acute Myopathies, Rhabdomyolysis, and CINM (03.O.3–6)
25 Inflammatory Disease, Neuro-Oncology, and Special Populations
25.1 Fulminant Demyelinating Diseases (03.P) 25.2 Autoimmune Encephalitis and Acute Autonomic Hyperactivity (03.Q–R) 25.3 Neuro-Oncology and Treatment Complications (03.S) 25.4 Pregnancy/Post-Partum, Post-Transplant, and Pediatric Patients (03.T–U)
26 Neurosurgical and Perioperative Complications
26.1 Postoperative Seizures, Hemorrhage, Ischemia, and Hyperperfusion (04.A, C, D, H) 26.2 Infection, CSF Leak, and Pneumocephalus (04.B, E, F) 26.3 Complications of EVD and Lumbar Drain (04.G, I)
27 Ethics, Prognostication, and Organ Donation
27.1 Communication, Decision-Makers, Advance Directives, and DNR (05.A, B, G) 27.2 Uncertainties of Prognostication and the Self-Fulfilling Prophecy (05.C) 27.3 Palliative Care, Withdrawal, Withholding, and Futility (05.D–F) 27.4 Donation After Cardiac Death and Care of the Organ Donor (05.H–I)
25.2 Autoimmune Encephalitis and Acute Autonomic Hyperactivity (03.Q–R)
Key Takeaways Explain This Topic AI
Anti-NMDA receptor encephalitis classically affects young women with ovarian teratoma and progresses from psychiatric change and seizures to orofacial dyskinesias, autonomic instability, and central hypoventilation; send CSF and serum antibodies and start first-line immunotherapy empirically when suspicion is high.
First-line rescue is corticosteroids plus IVIG or plasma exchange, plus tumor search and teratoma resection; rituximab or cyclophosphamide is second-line if the patient does not improve.
LGI1 antibody disease causes faciobrachial dystonic seizures, hyponatremia, and limbic encephalitis in older adults; name LGI1 or CASPR2 rather than the outdated voltage-gated potassium channel complex label.
Paroxysmal sympathetic hyperactivity after traumatic brain injury is simultaneous, triggered surges of tachycardia, hypertension, diaphoresis, and dystonic posturing; exclude seizure and sepsis first, then use gabapentin, propranolol, morphine, and bromocriptine conceptually.
Autonomic storms also occur in Guillain-Barré dysautonomia and tetanus; treat triggers, use short-acting hemodynamics, and do not assume every fever-tachycardia cycle is pneumonia.
Last updated: September 2026
Why antibody disease and autonomic storms share an ICU bed
The ABPN content specifications split autoimmune encephalitis (03.Q) from acute autonomic hyperactivity (03.R) . In the unit they collide: a young woman with anti–N-methyl-D-aspartate (NMDA) receptor encephalitis can hypoventilate and swing from tachycardia to asystole, and a trauma patient with paroxysmal sympathetic hyperactivity (PSH) can look like status epilepticus or septic shock. Treat the immune disease empirically when the syndrome is typical, and treat the autonomic syndrome only after you have excluded the mimics that kill.
Anti-NMDA receptor encephalitis
Anti-NMDA receptor encephalitis is the prototype surface-antibody encephalitis. It preferentially affects children and young women . An ovarian teratoma is the classic tumor in female adolescents and adults; extra-ovarian teratomas and other tumors are less common. HSV encephalitis can trigger later NMDA autoimmunity—do not stop the workup at a negative HSV PCR if a new movement disorder appears weeks later.
The course is stereotyped enough to recognize without the antibody result:
- Viral-like prodrome
- Psychiatric change, insomnia, memory loss, and seizures
- Orofacial dyskinesias , dystonia, catatonia, and decreasing consciousness
Autonomic instability (labile blood pressure and heart rate, hypersalivation, hyperthermia) and central hypoventilation requiring ventilation
MRI is often normal or shows only subtle FLAIR change. EEG may show slowing; extreme delta brush is supportive but insensitive. CSF is more sensitive than serum for NMDA-receptor antibodies; send both . Do not wait two weeks for a send-out before treating a typical syndrome.
First-line therapy: high-dose corticosteroids plus IVIG or PLEX , and immediate tumor search . In women of reproductive age that search includes pelvic MRI or transvaginal ultrasound, not a chest radiograph alone. Resect the teratoma as soon as the patient is operable; leaving the tumor in place is associated with poorer and slower recovery. If there is no meaningful improvement, escalate to rituximab and/or cyclophosphamide . Recovery often takes months; autonomic storms and hypoventilation can persist after the movement disorder quiets. Titrate weans slowly and keep a low threshold to re-image the pelvis if the course stalls.
LGI1, CASPR2, and the rest of the panel
Leucine-rich glioma-inactivated 1 (LGI1) antibody disease typically affects older men. The pathognomonic clue is faciobrachial dystonic seizures (FBDS) —brief, frequent, ipsilateral face-and-arm jerks that often precede limbic encephalitis. Hyponatremia is common. Tumor association is low (thymoma is occasional). FBDS often respond to immunotherapy better than to ordinary antiseizure drugs; start immunotherapy rather than stacking three sodium-channel agents.
Contactin-associated protein-like 2 (CASPR2) antibody disease produces neuromyotonia, neuropathic pain, insomnia, and Morvan syndrome (encephalopathy plus peripheral nerve hyperexcitability). Thymoma is more relevant than in LGI1. Stop using voltage-gated potassium channel (VGKC) complex as a diagnosis; a double-negative VGKC radioimmunoassay without LGI1 or CASPR2 is not a reason to immunosuppress.
Other ICU-relevant antibodies:
Antibody / syndrome Typical host and tumor ICU signature Treatment note
NMDA receptor Young woman; ovarian teratoma; post-HSV Psychiatry → dyskinesias → dysautonomia and hypoventilation Steroids + IVIG or PLEX; resect teratoma; rituximab/cyclophosphamide if slow
- LGI1 Older adult FBDS, hyponatremia, limbic seizures Immunotherapy early; tumor uncommon
- CASPR2 Adult; thymoma possible Neuromyotonia, Morvan, pain, insomnia Search for thymoma
- AMPA receptor Limbic encephalitis; various tumors Seizures, amnesia Tumor plus immunotherapy
GABA-B receptor Older adult; small-cell lung cancer Refractory seizures, limbic encephalitis Chest imaging is not optional
- GAD65 Stiff-person, cerebellar, epilepsy Less explosive than NMDA; high-titer CSF Immunotherapy variable
- GFAP Meningoencephalomyelitis Radial perivascular enhancement Steroids often help
Hu / ANNA-1 Small-cell lung cancer Sensory neuronopathy, encephalomyelitis Intracellular antigen; tumor treatment dominates; immunotherapy less reliable
Treat empirically if suspicion is high. Surface-antibody diseases respond; intracellular-antigen paraneoplastic syndromes respond less. That difference does not justify waiting for the panel in a ventilated, dyskinetic young woman.
Tumor search is age- and syndrome-directed : teratoma for NMDA, chest imaging for Hu and GABA-B, thymoma for CASPR2 and some AMPA, testicular ultrasound for Ma2. 18F-FDG PET is used when CT is unrevealing and the syndrome is paraneoplastic. Repeat the search if the patient plateaus.
Paroxysmal sympathetic hyperactivity after TBI
PSH is a syndrome of simultaneous, paroxysmal increases in sympathetic and motor activity after severe acquired brain injury, most often traumatic brain injury (TBI) . A 2014 international consensus defined it as transient, concurrent rises in heart rate, blood pressure, respiratory rate, temperature, sweating, and motor posturing. Episodes are often triggered by suctioning, turning, or pain. Older names (sympathetic storm, diencephalic seizures, autonomic storm) still appear in stems.
Exclude seizure and sepsis first. The same patient can have both PSH and true seizures, ventriculitis, pulmonary embolism, alcohol withdrawal, neuroleptic malignant syndrome, or serotonin syndrome. A normal-appearing EEG during a stereotyped, stimulus-triggered run of tachycardia and diaphoresis supports PSH; a highly rhythmic EEG change supports seizure. Fever workup is still required. Do not start bromocriptine and close the case while an EVD is growing gram-negative rods.
Once mimics are addressed, treatment is conceptual rather than a single mandatory cocktail:
Reduce triggers: premedicate for suction, treat pain, control fever, minimize unnecessary stimulation.
Gabapentin (or pregabalin) for prevention of episodes, especially when dystonia is prominent.
Propranolol as a nonselective beta blocker for tachycardia and hypertension (watch bronchospasm and cardiac failure).
Morphine as an abortive for an acute storm.
Bromocriptine as a dopamine agonist adjunct when episodes persist (confusion, nausea, and lowered seizure threshold are tradeoffs).
Clonidine, dexmedetomidine, baclofen, and benzodiazepines appear in practice algorithms; none is proven in a large randomized trial, so the examination tests the idea of the class , not a secret milligram dose.
The PSH-Assessment Measure (PSH-AM) scores clinical features plus diagnosis likelihood. You do not need to memorize every point value; you do need to know that PSH is a diagnosis of pattern after exclusion.
Autonomic storms in Guillain-Barré syndrome and tetanus
Guillain-Barré syndrome (GBS) dysautonomia produces labile blood pressure, resting tachycardia, ileus, and suction-triggered bradycardia or asystole. Use short-acting vasoactive drugs, continuous telemetry, and avoid long-acting beta blockade you cannot reverse on the next hypotensive swing. This is not PSH; it is peripheral autonomic failure plus instability.
Tetanus produces muscle spasms, trismus, and true sympathetic storms . Management is airway protection, benzodiazepines or magnesium for spasms, metronidazole, human tetanus immunoglobulin, and short-acting control of blood pressure and heart rate. Do not treat tetanus storms as ordinary alcohol withdrawal.
Examination traps
Waiting for serum-only NMDA antibodies while the patient hypoventilates; CSF is more sensitive.
Calling LGI1 disease VGKC encephalitis and withholding immunotherapy because the radioimmunoassay is low-titer and double-negative.
Treating every post-TBI tachycardia-fever cycle as pneumonia without examining for stimulus-triggered PSH—or the reverse, treating PSH while missing ventriculitis.
Using a long-acting beta blocker as the only therapy for GBS autonomic swings.