ICANS (Immune Effector Cell‑Associated Neurotoxicity Syndrome) – Guideline Summary

Definition & Pathophysiology

• The American Society for Transplantation and Cellular Therapy (ASTCT) defines ICANS as a pathologic central‑nervous‑system inflammatory process that follows CAR T‑cell therapy. 1
• Endothelial activation and blood‑brain‑barrier leak are central mechanistic features, with cytokines IL‑6, IFN‑γ, and TNF‑α implicated. [2][3]

Epidemiology (Onset & Duration)

• Typical onset occurs 4–10 days after CAR T‑cell infusion. [1][2]3
• The median duration is 14–17 days; BCMA‑directed products may have a slightly shorter course. [1][2]
• Delayed presentations can arise up to 1 month post‑infusion. [4][5]
• ICANS may appear concurrently with CRS, after CRS resolution, or independently. [4][5]

Clinical Presentation

Characteristic Triad

• Language disturbances (expressive aphasia, dysarthria, dysgraphia). 4
• Encephalopathy (confusion, behavioral change, delirium). 2
• Motor dysfunction (fine‑motor impairment, weakness, tremor, myoclonus, ataxia). 2

Additional Neurologic Manifestations

• Lethargy, altered level of consciousness, headache (often with fever), insomnia, anxiety/agitation, psychosis, dizziness. [2][1]3

Severe Complications

• Seizures (clinical or subclinical) and profound depressed consciousness. 6
• Cerebral edema (rare but potentially fatal). [1][4]5
• Need for intubation and airway protection in life‑threatening cases. [4][5]

Risk Factors

• Cytokine release syndrome (CRS) severity is the strongest predictor of ICANS severity. [1][3]7
• High baseline inflammatory state. 7
• Higher CAR T‑cell dose. 2
• Use of CD19‑directed CAR products (higher‑grade ICANS vs. BCMA‑directed). [1][3]7

Grading & Assessment

Recommended Grading Scale

• The NCCN panel endorses the ASTCT ICANS Consensus Grading Scale, which grades five domains (ICE score, consciousness, seizures, motor findings, intracranial pressure/edema); the overall grade is the highest domain grade. [1][2]8

ICE (Immune Effector Cell‑Associated Encephalopathy) Score

• A 10‑point tool assessing orientation, naming, command following, writing, and attention; for children < 12 yr or those with developmental delay, the Cornell Assessment of Pediatric Delirium (CAPD) replaces ICE. [1][2]8

Domain Details

• Level of consciousness – graded per ASTCT criteria. [1][8]
• Seizures – Grade 3: any clinical or subclinical seizure; Grade 4: prolonged or repetitive seizures without return to baseline. [1][8]
• Motor findings – graded according to severity of weakness, tremor, ataxia, etc. [1][8]
• Elevated intracranial pressure / cerebral edema – rare but incorporated into grading. [1][2]8

Practical Use

• The ICE tool can be performed daily or each shift during the at‑risk period, providing a more objective and streamlined assessment than earlier CTCAE methods. [8][1]

Management

General Principles

• Corticosteroids are the cornerstone of therapy; they are initiated for grade ≥ 2 ICANS. [8][4][5][9]

Grade‑Specific Approaches

• Grade 1 – Supportive care and close neurologic monitoring. [4][5]
• Grade 2 – Dexamethasone 10 mg IV with reassessment every 6–12 h; obtain brain MRI with and without contrast. 6 (Praxis source; no alternative citation found)
• Grade 3–4 – Methylprednisolone 1 g IV once or twice daily for 3 days; provide ICU‑level care for airway protection. [6][4]5

Refractory ICANS (no improvement ≥ 24 h)

• Repeat neuroimaging and CSF evaluation (including opening pressure, when feasible). 6
• Consider investigational agents such as anakinra, lenzilumab, or defibrotide. [4][5]9

Seizure Prophylaxis & Management

• Levetiracetam 500–750 mg PO q12 h for 30 days (for high‑risk CAR T products). 6
• Continue prophylaxis if EEG shows no seizure activity; escalate therapy for non‑convulsive status epilepticus. 6

Supportive Care Measures

• Aspiration precautions, head‑of‑bed elevation, and avoidance of CNS‑depressing medications. 6
• Antifungal prophylaxis is strongly recommended for all patients receiving corticosteroids. [5][10]

Therapeutic Pitfalls

• Do not dismiss isolated headache as ICANS; it is common and frequently co‑occurs with fever. [1][2]3
• Tocilizumab does not resolve ICANS and may worsen neurotoxicity; it should not be used for isolated ICANS symptoms. [4][5]9
• Avoid routine pre‑medication with corticosteroids before CAR T infusion, as this can mask early toxicities. 6
• Formal ICE scoring must be performed; informal neurologic assessments are insufficient. 6

Clinical Outcomes

• ICANS is generally self‑limited, with most symptoms resolving within 5–17 days. [4][5]9
• Development of any grade of ICANS does not adversely affect complete remission rates, progression‑free survival, or overall survival. (Non‑cited data omitted per instruction).

ICANS Workup and Management Guidelines

Clinical Assessment

• Perform the 10‑point Immune Effector Cell‑Associated Encephalopathy (ICE) score at least twice daily during the at‑risk period (approximately days 1–30 after CAR‑T infusion) to screen for early neurotoxicity. 11
• The ICE assessment evaluates orientation (year, month, city, hospital), naming of three objects, following commands, writing a complete sentence, and attention (counting backwards by tens from 100). 12
• In patients < 12 years old or with developmental delay, substitute the Cornell Assessment of Pediatric Delirium (CAPD) for ICE scoring. [11][12]
• Assess motor function (weakness, tremor, myoclonus, asterixis, ataxia, parkinsonism) at least twice daily. 11
• Document focal neurologic deficits such as hemiparesis or paraparesis. 13
• Continuously monitor level of consciousness using standardized descriptors (awake, somnolent, arousable to tactile stimulus, stupor, coma). [11][13]

Neuroimaging

• Obtain brain MRI with and without contrast for all patients with grade ≥ 2 ICANS. [11][13]
• MRI is preferred over CT because it better detects focal and diffuse cerebral edema and subtle parenchymal changes. 11
• If MRI is unavailable or contraindicated (e.g., pacemaker, hemodynamic instability), perform a contrast‑enhanced head CT. 11
• For persistent grade ≥ 3 ICANS, repeat neuroimaging (MRI or CT) every 2–3 days to monitor for progression or new cerebral edema. 11
• Initiate initial imaging promptly when ICANS is suspected or confirmed at grade ≥ 2. [11][13]
• Repeat imaging is indicated for clinical deterioration or lack of improvement within 24 hours despite treatment. 12

Electroencephalography (EEG)

• Obtain EEG for any unexplained altered mental status to evaluate for subclinical seizure activity or non‑convulsive status epilepticus. [11][13]
• Perform EEG for all patients with grade ≥ 2 ICANS. 11
• EEG is mandatory for any patient with clinical seizure activity (focal, generalized, or suspected). [11][13]

Lumbar Puncture (CSF Evaluation)

• Perform lumbar puncture for all patients with grade ≥ 3 ICANS; consider it for grade 2 ICANS when the diagnosis is uncertain or infection cannot be excluded. [11][13]
• Conduct the LP after neuroimaging to rule out contraindications such as mass effect or elevated intracranial pressure. 13
• Measure opening pressure when feasible. 12
• Send CSF for cell count with differential, protein, glucose, Gram stain, bacterial culture, and cytology. 14
• Include viral PCR studies (HSV, VZV, enterovirus) to exclude infectious encephalitis. 14
• CSF analysis helps differentiate ICANS from infectious or malignant causes of altered mental status. [11][12]

Laboratory Monitoring

• Serially (at least daily during acute ICANS) monitor:
  
  • Complete blood count with differential 13
  • Comprehensive metabolic panel (including sodium; severe hyponatremia can worsen neurotoxicity) 11
  • C‑reactive protein 13
  • Lactate dehydrogenase 13
  • Fibrinogen 11
  • Prothrombin time / partial thromboplastin time 15
  • Magnesium and phosphorus 14
• Perform infection work‑up when fever is present: blood cultures, urinalysis with culture, and chest radiograph. 14
• Screen for cytomegalovirus and Epstein‑Barr virus reactivation in the appropriate clinical context. [14][13]

Supportive Care Measures

• Implement aspiration precautions immediately for any grade of ICANS; elevate the head of the bed to 30–45°. 11
• Suspend oral intake and convert oral medications to intravenous routes for grade ≥ 2 ICANS. 13
• Consider levetiracetam 500–750 mg PO/IV every 12 hours for 30 days in patients receiving CAR‑T products with high ICANS incidence (particularly CD19‑directed therapies). 11
• Extend seizure prophylaxis to patients with a prior seizure history, central nervous system disease involvement, concerning EEG findings, or known neoplastic brain lesions. 11
• Initiate neurology consultation immediately for any sign of neurotoxicity. 11
• Transfer to intensive care for grade ≥ 2 ICANS, especially when concurrent grade ≥ 2 cytokine release syndrome is present. [11][13]

Critical Pitfalls to Avoid

• Do not rely solely on a declining ICE score to diagnose ICANS; subtle behavioral changes may precede measurable score deterioration.
• Do not administer tocilizumab for isolated ICANS without concurrent CRS, as it does not resolve neurotoxicity and may exacerbate it. [15][12]
• Do not delay neuroimaging in patients with grade ≥ 2 ICANS; early detection of cerebral edema is essential. 11
• Promptly monitor and correct severe hyponatremia, which can aggravate neurologic symptoms. 11