Can Subarachnoid Hemorrhage Due to Ruptured Aneurysm Present as Seizure?
Yes, seizures are a well-recognized presenting feature of aneurysmal subarachnoid hemorrhage (aSAH), occurring in 6-26% of patients, with the majority of early seizures happening at the time of aneurysmal rupture before medical presentation. 1
Incidence and Timing of Seizures in aSAH
Seizures at presentation occur in approximately 11-15% of patients with aSAH, most commonly at the time of initial aneurysmal rupture or rebleeding before aneurysm treatment 1
The reported incidence varies widely (6-26%) partly because many "seizure-like episodes" may not be truly epileptic in origin, and improved EEG monitoring has refined our understanding to a more accurate range of 7.8-15.2% 1
Early seizures (before medical evaluation) are far more common than in-hospital seizures in patients receiving prophylactic anticonvulsants 1
Delayed seizures occur in 3-7% of patients after the acute period 1
High-Risk Features for Seizure Presentation
Certain clinical and radiographic features significantly increase the likelihood of seizure as a presenting symptom:
Middle cerebral artery (MCA) aneurysm location is the strongest anatomic predictor of seizures 1
Intracerebral/intraparenchymal hematoma substantially increases seizure risk (OR 5.67) 1, 2
High subarachnoid clot burden (Hijdra scale >21) is independently associated with seizures (OR 2.76) 2
Subdural hematoma presence dramatically increases seizure risk (OR 5.67) 2
Poor neurological grade (Hunt-Hess grade ≥3 or WFNS grade IV-V) correlates with higher seizure incidence 1, 2, 3
Hydrocephalus and cortical infarction are additional risk factors 1
History of hypertension has been noted as a risk factor in retrospective studies 1
Clinical Implications for Patients with Prior Seizure History
Patients with preexisting epilepsy who present with seizures after aSAH require careful evaluation to distinguish between their baseline seizure disorder and new aSAH-related seizures 4
The presence of seizures at presentation in aSAH patients is not associated with development of chronic epilepsy at three months in those without prior epilepsy 5
Late seizures (>30 days post-treatment) correlate with history of previous seizures, presence of CSF shunt, and use of antiepileptic drugs 4
Nonconvulsive Seizures
Nonconvulsive seizures occur in approximately 19% of stuporous or comatose aSAH patients, typically appearing an average of 18 days after hemorrhage 1
Continuous EEG monitoring is reasonable in patients with fluctuating neurological examination, depressed mental state, or high-risk features to detect nonconvulsive seizures 1
Nonconvulsive status epilepticus is a very strong predictor of poor outcome in aSAH patients 1
Treatment Approach Considerations
Endovascular coiling is associated with significantly lower seizure incidence (3% delayed seizures, no periprocedural seizures) compared to surgical clipping 1, 6, 4
For patients presenting with seizures, antiseizure medication for ≤7 days is reasonable to reduce seizure-related complications in the perioperative period 1
Treatment beyond 7 days is not effective for reducing future SAH-associated seizure risk in patients without prior epilepsy who present with seizures 1
Phenytoin should be avoided as it is associated with excess morbidity and mortality, as well as worse cognitive outcomes at 3 months 1
Levetiracetam has a superior safety profile compared to phenytoin when seizure prophylaxis is indicated 7
Common Pitfalls to Avoid
Do not dismiss seizure as a presenting symptom of aSAH, particularly in patients with MCA aneurysms or intracerebral hematoma 1, 2
Avoid assuming all "seizure-like" episodes at ictus are true epileptic seizures; many may represent other phenomena related to acute brain injury 1
Do not routinely prescribe long-term anticonvulsants for patients presenting with seizures from aSAH unless they have specific high-risk features for delayed seizure disorder 1
Recognize that seizures at presentation do not independently predict worse long-term outcome, though they may indicate more severe hemorrhage 3