In an adult with a sudden loss of consciousness and convulsive activity (new‑onset seizure), could this be an acute cerebrovascular event (stroke)?

Seizure at Stroke Onset: Yes, This Can Be an Acute Stroke

Yes, a new-onset seizure with sudden loss of consciousness and convulsive activity can absolutely represent an acute stroke, and you must not allow the seizure to delay urgent stroke evaluation and imaging. Seizures occur in 5-10% of acute strokes, and current evidence demonstrates that seizure at onset should not automatically exclude stroke diagnosis or time-sensitive treatments 1, 2, 3.

Immediate Management Algorithm

Step 1: Stabilize and Assess (First 10 Minutes)

• Secure airway, breathing, and circulation immediately 1
• If seizure is ongoing and non-self-limiting, administer IV lorazepam to terminate the seizure 1, 4
• Perform rapid neurological examination using NIHSS to quantify stroke severity and detect focal deficits 1, 5
• Measure vital signs including heart rate, rhythm, blood pressure, temperature, and oxygen saturation 1

Step 2: Emergency Neuroimaging (Do Not Delay)

Obtain immediate non-contrast CT scan of the brain regardless of the seizure 1. The seizure does not exclude stroke and must not delay imaging 4.

• If patient arrives within 4.5 hours of last known well: perform NCCT immediately to determine thrombolysis eligibility 1
• If patient arrives within 6 hours: perform NCCT plus CTA (arch-to-vertex) to identify large vessel occlusions for endovascular thrombectomy 1
• Do not wait for laboratory results before imaging unless there is clinical suspicion of bleeding abnormality, thrombocytopenia, or known anticoagulant use 1

Step 3: Differentiate Stroke from Seizure Mimics

The critical clinical challenge is distinguishing acute ischemic stroke from postictal Todd's paralysis 6. Key differentiating features:

Favor stroke diagnosis when:

• Focal neurological deficits persist beyond 24 hours 2
• Symptoms began while patient was active with smooth progression over minutes to hours 7
• Patient has vascular risk factors (hypertension, atrial fibrillation, prior stroke) 5
• Seizure occurred at the exact moment of symptom onset (suggests cortical ischemia as the seizure trigger) 1, 2

Consider Todd's paralysis when:

• Known epilepsy history exists 8
• Deficits resolve within hours 2
• No acute findings on initial CT (though this does not exclude stroke) 6

Critical pitfall: Non-contrast CT may be normal in the first 24 hours of acute ischemic stroke, missing up to 24% of cases 5. If clinical suspicion for stroke remains high despite negative CT, obtain MRI with diffusion-weighted imaging (DWI) to confirm acute ischemia 5, 6.

Seizure Management in Confirmed Acute Stroke

For Single, Self-Limiting Seizure at Stroke Onset

Do not initiate long-term anticonvulsant therapy 1, 4. This is a Level C recommendation from the Canadian Stroke Best Practice guidelines:

• A single seizure occurring at onset or within 24 hours is classified as an "immediate" post-stroke seizure 1, 4
• These seizures should NOT be treated with chronic anticonvulsants 1, 4
• There is no evidence supporting prophylactic anticonvulsants, and possible harm exists with negative effects on neural recovery 1, 4

For Recurrent or Ongoing Seizures

Monitor continuously for recurrent seizure activity during routine vital sign checks 1, 4. If seizures recur:

• Treat recurrent seizures as per standard seizure protocols (not stroke-specific) 1
• Consider EEG monitoring if unexplained reduced level of consciousness develops, as nonconvulsive status epilepticus can occur 1, 4
• Only initiate long-term anticonvulsants if recurrent seizures occur or status epilepticus develops 4

Impact on Thrombolysis Decisions

Seizure at stroke onset is listed as a relative contraindication to IV thrombolysis in traditional guidelines 1. However, this is increasingly challenged:

• Modern neuroimaging (DWI/PWI MRI and MRA) can confirm acute ischemic stroke even in the presence of seizures 6
• Case reports demonstrate successful thrombolysis with good outcomes in patients with seizure at onset when MRI confirms acute ischemia 6
• The key is confirming that focal deficits are due to acute ischemia rather than postictal state 6

Practical approach: If DWI/PWI MRI is immediately available and confirms acute ischemia with salvageable tissue, thrombolysis may be considered despite seizure 6. If only CT is available and shows no hemorrhage, the decision becomes more complex and requires rapid neurological consultation.

Laboratory Evaluation (Concurrent, Not Delaying)

Order these tests immediately but do not delay imaging or treatment 1:

• Blood glucose (hypoglycemia can mimic stroke with seizures) 1
• Complete blood count with platelets 1
• Electrolytes 1
• Coagulation studies (INR, aPTT) 1
• Renal function (creatinine) 1
• 12-lead ECG (atrial fibrillation is a major stroke cause and can be detected acutely) 1, 5

Risk Stratification: Which Strokes Cause Seizures?

Seizures are more likely with:

• Cortical involvement (deep or infratentorial lesions rarely cause seizures) 2, 9
• Hemorrhagic stroke (14.3% seizure rate vs. 6.7% for ischemic stroke) 9
• Sinus thrombosis (16.3% seizure rate, highest risk) 9
• Higher NIHSS scores (more severe strokes) 9
• Younger age at stroke onset 9

Location does not matter as much as cortical vs. subcortical: Cortical versus subcortical location did not influence seizure risk in adjusted analyses 9.

Common Pitfalls to Avoid

1. Do not dismiss the possibility of stroke because a seizure occurred – 5-10% of strokes present with seizures 2, 3
2. Do not delay brain imaging to "wait and see" if deficits resolve – time is brain 1, 4
3. Do not start prophylactic anticonvulsants after a single seizure at stroke onset 1, 4
4. Do not rely solely on CT in the first 24 hours – MRI with DWI is far more sensitive 5, 6
5. Do not automatically exclude thrombolysis if advanced imaging confirms acute ischemia 6