Andrew N. Wilner, MD, FAAN, FACP
Angels Neurological Centers
A 79-year-old woman had 2 generalized tonic-clonic seizures. She had no prior seizures. The patient’s family called 911.
Past medical history was remarkable for asthma, diet-controlled type 2 diabetes, gastroesophageal reflux disease, hypercholesterolemia, hypertension, and osteoporosis. She had a right-sided posterior communicating artery aneurysm coiled and stented 2 years previously.
Medications included aspirin, clopidogrel, an inhaler, ranitidine, and valsartan.
In the emergency room, the patient was initially confused but quickly returned to baseline. Vital signs and neurological examination were normal except for mild ptosis of the right eye, a chronic finding due to compression of the right 3rd nerve by the posterior communicating aneurysm.
Visible on head computed tomography (CT) scan was a thrombosed aneurysmal sac measuring 2.5 x 2 cm ( Figure 1 ) which had increased in size from 2 years ago. Laboratory testing revealed an elevated lactic acid of 4.6 (normal: 0.871-2.1 mmol/L) and decreased CO 2 of 20 (normal: 22-30 mEq/l) consistent with recent convulsions. Complete blood count, chemistry, urinalysis, and chest x-ray were normal.
The patient was treated with levetiracetam and had no further seizures. After a diagnostic angiogram, a stent was placed to divert cerebral blood flow from the aneurysm. The patient was discharged with a prescription for levetiracetam 750 mg twice a day. A routine electroencephalogram (EEG) was unremarkable.
Approximately 100,000 new cases of epilepsy are diagnosed in the United States each year. 1 The incidence of new onset seizures is highest in the elderly. 2 In this age group, the most common cause of provoked new onset epilepsy is acute stroke. 2 Brain tumors, dementia, head trauma, and systemic disorders (eg, hepatic failure, hypoglycemia, hyperglycemia, hyponatremia, hypocalcemia, hypothyroidism, infections, and uremia) can all precipitate seizures. 2
Seizures due to unruptured cerebral aneurysms are rare, but may be more common with giant aneurysms (2.5 cm or larger). 3,4 Unruptured aneurysms may cause seizures due to subclinical hemorrhage, thrombus, or mass effect on the mesial temporal lobe. 5 In this patient, mass effect on the right mesial temporal lobe is clearly evident on the magnetic resonance image (MRI) and is the likely explanation for her seizures ( Figure 2 ).
This unusual case emphasizes the wide range of etiologies for new onset seizures in the elderly and need for a thorough diagnostic evaluation. 3
1. Browne TR, Holmes GL. Epilepsy [published correction appears in N Engl J Med . 2001;344(25):1956]. N Engl J Med . 2001;344(15):1145-1151.
2. Brodie MJ, Kwan P. Epilepsy in elderly people. BMJ. 2005;331(7528):1317-1322.
3. Cagavi F, Kalayci M, Unal A, Atasoy HT, Cağavi Z, Açikgöz B. Giant unruptured anterior communicating artery aneurysm presenting with seizure. J Clin Neurosci. 2006;13(3):390-394.
4. Hänggi D, Winkler PA, Steiger JH. Primary epileptogenic unruptured intracranial aneurysms: incidence and effect of treatment on epilepsy. Neurosurgery. 2010;66(6):1161-1165.
5. Andereggen L, Andres RH. “Sentinel seizure” as a warning sign preceding fatal rupture of a giant middle cerebral artery aneurysm. World Neurosurg . 2017;100:709.e11-709.e13.
Figure 1. CT brain axial image without contrast demonstrating a giant aneurysm adjacent to right mesial temporal lobe
Figure 2. MRI brain coronal image T2W-TSE revealing a giant aneurysm compressing right mesial temporal lobe