What is the management plan for a patient with nonischemic cerebral enhancing lesions (NICE) possibly related to a delayed reaction to devices or materials used during an intravascular procedure?

Management of Nonischemic Cerebral Enhancing Lesions (NICE) Following Intravascular Procedures

For patients with nonischemic cerebral enhancing lesions (NICE) showing mild interval improvement on imaging, conservative management with clinical monitoring and follow-up imaging is recommended as the primary approach, as these lesions typically follow a benign clinical course over time.

Understanding NICE Lesions

NICE lesions are rare complications following endovascular procedures characterized by:

• Delayed onset (typically 1-12 months post-procedure)
• Punctate, nodular or annular enhancing foci on MRI
• Surrounding vasogenic edema
• Distribution in the vascular territory of the intervention
• No direct ischemic cause

Epidemiology and Clinical Course

NICE lesions are exceptionally rare complications:

• Incidence of approximately 0.5% after aneurysm endovascular treatment 1
• Even rarer after mechanical thrombectomy (3 cases in 34,824 procedures) 2
• Mean delay to diagnosis is 5±9 months, with onset occurring within one month in about 32% of cases 3

Clinical Presentation and Prognosis

• 74% of patients are symptomatic at onset 3
• Clinical course is generally benign:
  • 81% of patients become asymptomatic or minimally symptomatic (mRS 0-1)
  • 13% have mild disability (mRS 2)
  • No severe disability reported in large case series 3
• MRI may show persistent enhancement in 71% of cases despite clinical improvement 3

Management Algorithm

Initial Assessment

1. Confirm diagnosis and exclude alternative causes

   • Contrast-enhanced MRI to confirm NICE lesion characteristics
   • Rule out ischemic stroke, infection, tumor, or other inflammatory conditions

2. Evaluate symptom severity

   • Document neurological symptoms and functional status
   • Use standardized scales (NIHSS, mRS) for objective assessment

Management Based on Symptom Severity

For Asymptomatic or Mildly Symptomatic Patients:

• Conservative management with clinical monitoring
• Follow-up MRI at 3-6 months to assess lesion evolution
• No specific medication intervention required

For Symptomatic Patients:

• Corticosteroids may be considered for patients with significant edema and neurological symptoms
• Anti-seizure medications if seizures are present
• Cognitive rehabilitation for patients with cognitive impairment

Follow-up Protocol

• Clinical evaluation every 1-3 months until stable
• Follow-up MRI at 3-6 month intervals until stabilization or resolution
• Long-term follow-up is warranted as NICE lesions can show prolonged fluctuation 1

Pathophysiology and Prevention

The exact pathophysiology remains unclear, but two main theories exist:

1. Foreign body reaction to embolic material from devices used during intervention 1
2. Delayed hypersensitivity reaction to device materials (e.g., nickel allergy)

While nickel allergy has been proposed as a potential mechanism, evidence suggests foreign body emboli are more likely responsible 1.

Important Considerations and Pitfalls

• Do not confuse with acute stroke: NICE lesions have a delayed onset and different imaging characteristics compared to acute ischemic events
• Avoid unnecessary interventions: These lesions typically follow a benign course and rarely require surgical intervention
• Consider the possibility of NICE lesions in patients with new neurological symptoms weeks to months after endovascular procedures
• Be aware that enhancement can persist on imaging despite clinical improvement

Conclusion

The management of NICE lesions is primarily conservative, with monitoring and supportive care. The prognosis is generally favorable, with most patients achieving good functional outcomes despite potential persistence of imaging abnormalities.