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Unruptured Posterior Cerebral Artery Aneurysm Presenting with Temporal Lobe Epilepsy

Published online by Cambridge University Press:  28 May 2020

Leeor S. Yefet*
Affiliation:
Division of Neurosurgery, Vancouver General Hospital, Vancouver, Canada
Mostafa Fatehi
Affiliation:
Division of Neurosurgery, Vancouver General Hospital, Vancouver, Canada
Yahya Aghakhani
Affiliation:
Division of Neurology, Vancouver General Hospital, Vancouver, Canada
Gary Redekop
Affiliation:
Division of Neurosurgery, Vancouver General Hospital, Vancouver, Canada
*
Correspondence to: Leeor S Yefet, Division of Neurosurgery, Vancouver General Hospital, 899W 12th Avenue, Vancouver V5Z 1M9, Canada. Email: lyefet@alumni.ubc.ca
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Abstract

Type
Letter to the Editor
Copyright
Copyright © The Author(s), 2020. Published by Cambridge University Press on behalf of The Canadian Journal of Neurological Sciences Inc.

The International League Against Epilepsy (ILAE) proposed a new epilepsy classification scheme in 2013. Reference Scheffer, Berkovic and Capovilla1 The framework, which was formalized in 2017, builds upon several previous iterations while emphasizing the importance of seizure etiology at each level of classification. However, a recent systematic review reported that “epilepsy of unknown origin” continues to be the most prevalent diagnosis. Reference Fiest, Sauro and Wiebe2 The same study found structural/metabolic etiologies account for 40% of cases. Reference Fiest, Sauro and Wiebe2

Unruptured intracranial aneurysms are often asymptomatic or accompany vague symptoms like headaches; however, they may also cause cranial neuropathies or lead to cerebral ischemia. Reference Raps, Rogers and Galetta3 Giant aneurysms or those that project into cortical surfaces (i.e., the medial temporal lobe) can certainly lead to seizures. Overall, posterior cerebral artery (PCA) aneurysms are uncommon and hence they are very rarely implicated as the cause for seizures.

A search of the MEDLINE and EMBASE databases was performed with the specific Medical Subject Headings (MeSH) and keywords for (epilepsy or seizures) and (PCA and intracranial aneurysms). A total of 14 studies were initially identified. Titles and abstracts were screened; studies that described PCA aneurysms presenting with seizures were included. Of the seven remaining studies, two were excluded on further review. One did not have full text available and the other described a mycotic aneurysm located in the calcarine sulcus in the setting of metastatic choriocarcinoma. Reference Huang, Shih and Lui4,Reference Yeo, Britz, Powell, Smith and Zhang5 A summary of the cases is presented in Table 1.

Table 1: Summary of cases with PCA aneurysms presenting with seizures.

Here, we report a patient who experienced stereotypic spells consistent with temporal lobe epilepsy which was caused by an unruptured PCA aneurysm.

A 59-year-old left-handed man with a history of dyslipidemia and hypertension presented with episodes consistent with focal aware seizures. The patient described that these events began with a sense of panic and feeling like a curtain was coming down upon him with associated cognitive slowing as if he was wading through water. Soon thereafter, he would develop severe nausea with no emesis. These experiences lasted several minutes without loss of awareness, followed by an immediate return to his cognitive baseline. These events occurred two to three times per week with no identifiable triggers. His neurological examination did not yield focal deficits.

The patient was started on carbamazepine 200 mg BID empirically and referred to an epileptologist. A computed tomography angiogram and magnetic resonance imaging revealed a 7 mm aneurysm arising from the P2 segment of the left PCA that was embedded in the medial aspect of the left parahippocampal gyrus with increased signal suggesting inflammation or edema (Figure 1). A cerebral angiogram confirmed the presence of the superolaterally projecting saccular aneurysm (Figure 1).

Figure 1: Findings of diagnostic imaging. CTA slices in axial (A), coronal (B), and sagittal (C) views suggest a left PCA aneurysm which protrudes into the left parahippocampal gyrus. MRI slices in axial (D), sagittal (E), and coronal (F) views similarly suggest a left PCA aneurysm projecting into the left parahippocampal gyrus. Cerebral angiography demonstrating a left PCA aneurysm in coronal (G) and sagittal (H) views.

After considering endovascular and open surgical management options, as well as a conservative approach, microsurgical clip repair through a left subtemporal approach was recommended. This decision was based on the aneurysm size, distal location of the aneurysm, significant proximal vascular tortuosity, and small parent artery diameter. Furthermore, the surgical approach would also allow for resection of any local abnormal tissue. The patient underwent neuropsychological evaluation which suggested left hemisphere language dominance and low risk of significant cognitive decline with the proposed lesionectomy without hippocampal resection. An electroencephalogram showed moderate left temporal dysrhythmia seen maximal over the mid to posterior temporal derivations with a variable centroparietal field. These findings indicated focal cerebral dysfunction arising from the area most indicative of an underlying structural abnormality.

The surgery proceeded as planned with a left subtemporal craniotomy, clipping of the aneurysm base, and resection of gliotic tissue surrounding the aneurysm dome (Supplementary Figure 1). There was no evidence of adjacent hemosiderin deposition. The postoperative imaging confirmed satisfactory clipping, and the patient remains seizure free 5 months after surgery. He remains on carbamazepine which will be reassessed on his 6-month follow-up.

This case contributes to the literature describing PCA aneurysms as an epilepsy etiology. A review of the literature identified five cases of patients with PCA aneurysms presenting with seizures (Table 1). Reference Casey and Moore6Reference Yacubian, Rosemberg, Silva, Jorge, Oliveira and Assis10 The median age was 30, with range between 7 weeks to 35 years. Unique to the present case, the patient is the oldest reported at 59 years of age. Males were more common in this series (4 males, 1 females), and aneurysms were more frequently present in the right hemisphere (3 right, 2 left). Notably, seizure onset was focal in four cases. Reference Lad, Shannon and Byrne7Reference Yacubian, Rosemberg, Silva, Jorge, Oliveira and Assis10 Of these, awareness was described in two patients as being impaired and in one patient as intact.

Casey and Moore described a patient manifesting with generalized seizure. Reference Casey and Moore6 This case was unique in that the 24-year-old male was believed to have developed the aneurysm following a closed head injury. The remaining cases do not identify an explicit etiology, this being consistent with common understanding that cerebral aneurysms are often multifactorial acquired lesions. The etiology of the seizures could be due to several causes including gliosis secondary to subclinical hemorrhage or mass effect and impingement into the adjacent medial temporal cortex.

Two of the five cases identified in the literature underwent endovascular treatment of their aneurysms. Reference Peera and LoCurto8,Reference Yacubian, Rosemberg, Silva, Jorge, Oliveira and Assis10 Posterior circulation aneurysms are often treated with an endovascular approach due to the challenging surgical exposure and the close proximity of other deep brain structures. Notably, outcomes in these cases were largely comparable to those treated with surgery, with no described follow-up morbidity or mortality in either group. Reference Casey and Moore6,Reference Lad, Shannon and Byrne7,Reference Putty, Luerssen, Campbell, Boaz and Edwards9 One benefit to choosing microsurgical clipping is the direct visualization of the surrounding cortex allowing for concurrent lesionectomy. However, the choice of treatment modality ought to consider factors including patient characteristics, aneurysm morphology and location, and physician expertise. Reference Tsianaka, Al-Shawish, Potapov, Fountas, Spyrou and Konovalov11

This case report adds to the limited literature describing unruptured PCA aneurysms presenting with seizures. This patient was significantly older than previous cases, and he experienced focal aware seizures consistent with temporal lobe epilepsy for some time before seeking medical care. His seizures have not recurred 5-month post-clipping and lesionectomy. Almost all previous cases also presented with focal aware seizures and their seizures were reduced post-intervention. Both endovascular and surgical therapies have demonstrated similar efficacy with no clear morbidity or mortality advantage to either modality in this small group of patients.

Disclosures

The authors have nothing to disclose.

Statement of Authorship

All authors made significant contributions to this manuscript. GR was the most responsible physician for the procedure discussed in this case report. YA was the consultant epileptologist. MF was the resident neurosurgeon involved in this case report and helped obtain and clarify case information. LY wrote the initial draft of the manuscript. MF, YA, and GR reviewed and revised the manuscript.

Supplementary material

To view supplementary material for this article, please visit https://doi.org/10.1017/cjn.2020.105.

References

Scheffer, IE, Berkovic, S, Capovilla, G, et al. ILAE classification of the epilepsies: position paper of the ILAE Commission for Classification and Terminology. Epilepsia. 2017;58:512521.CrossRefGoogle ScholarPubMed
Fiest, KM, Sauro, KM, Wiebe, S, et al. Prevalence and incidence of epilepsy. Neurology. 2017;88:296303.CrossRefGoogle ScholarPubMed
Raps, EC, Rogers, JD, Galetta, SL, et al. The clinical spectrum of unruptured intracranial aneurysms. Arch Neurol. 1993;50:265268.CrossRefGoogle ScholarPubMed
Huang, LT, Shih, TY, Lui, CC. Posterior cerebral artery aneurysm in a two-year-old girl. J Formos Med Assoc. 1996;95:170172.Google Scholar
Yeo, CJJ, Britz, GW, Powell, SZ, Smith, RG, Zhang, YJ. Recurrent cerebral hemorrhage in normal pregnancy secondary to mycotic pseudoaneurysms related to choriocarcinoma. World Neurosurg. 2018;109:247250.CrossRefGoogle ScholarPubMed
Casey, ATH, Moore, AJ. A traumatic giant posterior cerebral artery aneurysm mimicking a tentorial edge meningioma. Br J Neurosurg. 1994;8:9799.CrossRefGoogle ScholarPubMed
Lad, SP, Shannon, L, Byrne, RW. Incidental aneurysms in temporal lobe epilepsy surgery: report of three cases and a review of the literature. Br J Neurosurg. 2012;26:6974.CrossRefGoogle Scholar
Peera, MA, LoCurto, M. Temporal lobe seizures from a posterior cerebral artery aneurysm presenting as memory flashbacks. CJEM. 2009;11:389392.CrossRefGoogle ScholarPubMed
Putty, TK, Luerssen, TG, Campbell, RL, Boaz, JC, Edwards, MK. Magnetic resonance imaging diagnosis of a cerebral aneurysm in an infant. Case report and review of the literature. Pediatr Neurosurg. 1990;16:4851.CrossRefGoogle Scholar
Yacubian, EMT, Rosemberg, S, Silva, HCA da, Jorge, CL, Oliveira, E de, Assis, LM de. Intractable complex partial seizures associated with posterior cerebral artery giant aneurysm: a case report. Epilepsia. 1994;35:13171320.CrossRefGoogle ScholarPubMed
Tsianaka, E, Al-Shawish, A, Potapov, A, Fountas, K, Spyrou, M, Konovalov, N. Clipping versus coiling in posterior circulation intracranial aneurysms: a meta-analysis. Chinese Neurosurg J. 2019;5:16.CrossRefGoogle ScholarPubMed
Figure 0

Table 1: Summary of cases with PCA aneurysms presenting with seizures.

Figure 1

Figure 1: Findings of diagnostic imaging. CTA slices in axial (A), coronal (B), and sagittal (C) views suggest a left PCA aneurysm which protrudes into the left parahippocampal gyrus. MRI slices in axial (D), sagittal (E), and coronal (F) views similarly suggest a left PCA aneurysm projecting into the left parahippocampal gyrus. Cerebral angiography demonstrating a left PCA aneurysm in coronal (G) and sagittal (H) views.

Supplementary material: PDF

Yefet et al. supplementary material

Figure S1

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