Which types of intracranial hemorrhage are most commonly associated with seizures?

Types of Intracranial Hemorrhage Associated with Seizures

Lobar intracerebral hemorrhage (ICH) is the type of head bleed most strongly associated with seizures, occurring in approximately 28-31% of patients, particularly when blood contacts the cortical surface. 1, 2

Seizure Risk by Hemorrhage Location and Type

Highest Risk: Lobar/Cortical Hemorrhage

• Lobar ICH carries the highest seizure risk because blood products in direct contact with cortical neurons trigger biochemical irritation through iron, hemoglobin, and thrombin acting as epileptogenic substances 1, 2
• Early seizures occur in 4.2% of all ICH patients within the first 72 hours, but this increases significantly with lobar location 1
• Electrographic seizures (often nonconvulsive) occur in 28% of monitored ICH patients during the initial 72 hours, predominantly in lobar hemorrhages 1, 3
• Cortical proximity is critical—hemorrhages located within 1 mm of cortex have substantially higher seizure rates than deep hemorrhages 4

High Risk: Subarachnoid Hemorrhage (SAH)

• Aneurysmal SAH causes seizures in 6-26% of patients, with most early seizures occurring at the time of aneurysmal rupture before medical presentation 1, 5
• Seizures at presentation occur in approximately 11-15% of aSAH patients 5
• Middle cerebral artery (MCA) aneurysm location is the strongest anatomic predictor of seizures in SAH 5
• Nonconvulsive seizures occur in approximately 19% of stuporous or comatose aSAH patients, typically appearing around 18 days after hemorrhage 5

Moderate Risk: Intracerebral Hemorrhage with Specific Features

• Presence of intraparenchymal/intracerebral hematoma substantially increases seizure risk (OR 5.67) 5
• Hemorrhage volume expansion of 30% or more between admission and 24-hour CT is independently associated with electrographic seizures (33% vs 15%; OR 9.5) 4
• Presence of subarachnoid blood component increases early seizure risk 6
• Intraventricular hemorrhage extension is a recognized risk factor 7

Lower Risk: Deep/Subcortical Hemorrhage

• Deep subcortical hemorrhages (basal ganglia, thalamus) have lower seizure rates but still occur in approximately 21% of cases 3
• These hemorrhages cause seizures through secondary mechanisms (edema, mass effect, midline shift) rather than direct cortical irritation 2, 3

Moderate Risk: Subdural Hematoma

• Subdural hemorrhage is predictive of both early-onset and late-onset seizures after ICH 6
• This association persists even after controlling for other demographic and clinical factors 6

Critical Clinical Patterns

Nonconvulsive Seizures Are Common

• Over half of post-hemorrhagic seizures are purely electrographic without clinical manifestations 4
• In monitored patients, 56% of first electrographic seizures are detected within the first hour of continuous EEG, and 94% within 48 hours 4
• Nonconvulsive seizures are associated with higher NIHSS scores, midline shift, and trend toward poor outcomes 1, 2

Timing Considerations

• Early seizures (within 7 days) occur in 4.2% of ICH patients overall, with 8.1% having seizures within 30 days 1
• Delayed seizures occur in 3-7% of patients after the acute period 5
• For aSAH, the majority of early seizures happen at the time of rupture before medical evaluation 5

Key Clinical Pitfall

The absence of clinically apparent seizures does not exclude seizure activity in patients with intracranial hemorrhage. Continuous EEG monitoring should be strongly considered in patients with lobar ICH, cortical involvement, unexplained neurological deterioration, or depressed mental status, as purely electrographic seizures occur in 18-28% of monitored patients and are associated with worse outcomes. 1, 5, 3, 4