NMC Case Report Journal
Online ISSN : 2188-4226
ISSN-L : 2188-4226
CASE REPORT
Non-convulsive Status Epilepticus as a Potentially Under-recognised Cause of Consciousness Disturbance Following Mechanical Thrombectomy: A Case Report
Kiichi YANAGISAWA, Takuya SAITO, Tatsuhito ISHII, Keishiro SATO, Kazunari HOMMA, Yoshiyuki KONDO
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Keywords: cerebral infarction, mechanical thrombolysis, status epilepticus, electroencephalography, consciousness disorders
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2024 Volume 11 Pages 407-411

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Abstract

We report a case of persistent consciousness disturbance due to non-convulsive status epilepticus (NCSE) following a successful mechanical thrombectomy (MT). A 98-year-old female with atrial fibrillation presented with impaired consciousness and right hemiparesis 6 hrs after her last known well state. Magnetic resonance angiography revealed occlusion of the left internal carotid artery, necessitating MT to achieve complete recanalisation. Following admission, her consciousness showed no signs of improvement, and electroencephalography (EEG) revealed NCSE as the underlying cause. Levetiracetam treatment led to improvement in both clinical symptoms and EEG findings. This case highlights the importance of prompt diagnosis and management of NCSE in patients with ischaemic stroke who have persistent consciousness disturbance even after MT.

Introduction

Several large-scale studies have demonstrated the efficacy and safety of mechanical thrombectomy (MT) in elderly patients.1,2) However, some elderly patients experience delayed clinical recovery following MT.3) Non-convulsive status epilepticus (NCSE) is a leading cause of consciousness disturbance in acute medical conditions, including acute ischaemic stroke. Despite this, there is a paucity of literature on NCSE following MT. Herein, we present a case of prolonged consciousness disturbance following MT for acute ischaemic stroke, ultimately attributed to NCSE.

Case Report

A 98-year-old female, with a history of atrial fibrillation, heart failure, hypertension, dyslipidaemia, and chronic kidney disease, presented with acute consciousness disturbance 6 hrs after her last known well state. She was not taking any anticoagulants, and her premorbid modified Rankin Scale (mRS) score was 2. On admission, she had a Glasgow Coma Scale (GCS) score of 9 (E4V1M4), a National Institutes of Health Stroke Scale score of 20, and presented with right hemiparesis and aphasia. Laboratory studies revealed elevated levels of blood urea nitrogen (26 mg/dL), serum creatinine (1.00 mg/dL), D-dimer (3.0 μg/mL), and brain natriuretic peptide (204.5 pg/mL). Diffusion-weighted imaging demonstrated scattered acute ischaemic lesions in the left middle cerebral artery (MCA) territory, with a Diffusion-Weighted Imaging-Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) of 3 (Fig. 1). Moreover, magnetic resonance angiography revealed a left internal carotid artery (ICA) occlusion (Fig. 1). Given these findings, we opted for MT despite her advanced age and low DWI-ASPECTS.

Fig. 1

Magnetic resonance imaging and magnetic resonance angiography on admission and digital subtraction angiography during mechanical thrombectomy. Magnetic resonance imaging shows scattered acute ischaemic stroke in the left middle cerebral artery area (A) (B). Magnetic resonance angiography shows left internal carotid artery occlusion (C). Lateral view of the left internal carotid arteriography before mechanical thrombectomy demonstrates occlusion of the left internal carotid artery supra clinoid segment (D). Lateral view of the left internal carotid arteriography after the first pass shows successful recanalisation (E).

Digital subtraction angiography confirmed an occlusion of the left ICA supraclinoid segment (Fig. 1). A 9-Fr OPTIMO balloon-guiding catheter (Tokai Medical Products, Aichi, Japan) was inserted via the right common femoral artery into the left ICA cervical segment. A Phenom 21 microcatheter (Medtronic, Minneapolis, MN, USA) and a CHIKAI black microguidewire (Asahi Intecc, Aichi, Japan) were then advanced to the left MCA M1 segment. A 6 x 40 mm Solitaire X stent retriever (Medtronic, Minneapolis, MN, USA) was subsequently deployed across the occluding lesion, extending from the left MCA M1 segment to the left ICA clinoid segment. Afterwards, a REACT 71 aspiration catheter (Medtronic, Minneapolis, MN, USA) was positioned proximal to the stent retriever to facilitate thrombus aspiration using an aspiration pump. Both the stent retriever and aspiration catheter were successfully retrieved, achieving Thrombolysis of the Cerebral Infarction 3 reperfusion (Fig. 1).

On day 2 of admission, the patient remained unconscious, with a GCS score of 7 (E2V1M4). She did not exhibit any subtle motor symptoms or fluctuations in consciousness. Electroencephalography (EEG) revealed continuous 1-2 Hz lateralised periodic discharges (LPDs) over the left frontal regions of the longitudinal bipolar montage (Fig. 2). Following intravenous levetiracetam administration, 18-hr long-term video-EEG monitoring was conducted, which captured intermittent electrographic seizures with definite evolution (Fig. 3). Based on these findings, she was diagnosed with NCSE.

Fig. 2

Electroencephalography on day 2. Electroencephalography on day 2 reveals continuous 1-2 Hz lateralised periodic discharges over the left frontal regions of the longitudinal bipolar montage.

Fig. 3

Long-term video-electroencephalography on days 2 and 3. Findings of the 18-hr long-term video-electroencephalography on days 2 and 3 showing intermittent electrographic seizures with definite evolution.

The patient's level of consciousness fluctuated over the next several days before showing consistent improvement, eventually achieving a GCS score of 13 (E4V3M6). Magnetic resonance imaging (MRI) on day 5 revealed mild haemorrhagic transformation without significant enlargement of the ischaemic stroke (Fig. 4). Follow-up EEG on day 18 confirmed the improvement of electrographic features with diminished LPDs. On day 26, she was discharged to a rehabilitation facility with an mRS score of 4. Oral dose of levetiracetam was continued because she was considered at high risk for poststroke epilepsy due to the presence of acute symptomatic status epilepticus and cortical involvement of the infarction.

Fig. 4

Magnetic resonance imaging and magnetic resonance angiography on day 5. Magnetic resonance imaging on day 5 shows mild haemorrhagic transformation without significant enlargement of the ischaemic stroke (A) (B). Image of the magnetic resonance angiography showing left internal carotid artery patency (C).

Discussion

NCSE is characterised by continuous epileptic activity without overt motor symptoms.4) Its diagnosis relies primarily on EEG patterns, with a clear time-locked correlation to clinical manifestations such as eye blinking, eye deviation, nystagmus, and facial twitching, and post-medication clinical improvement being an essential supportive factor. In this case, long-term video-EEG monitoring indicated electrographic seizures with evolution for over 10 mins, whereas follow-up EEG on day 18 showed improvement after levetiracetam administration with clinical recovery. These findings satisfy the NCSE criteria outlined in the American Clinical Neurophysiology Society standardised critical care EEG terminology (2021 version).5)

Studies estimate that NCSE affects approximately 3.6% of patients hospitalised for ischaemic stroke, with an increasing incidence based on age.6,7) NCSE has also been associated with high mortality and morbidity rates, particularly in the context of acute underlying causes, such as ischaemic stroke.8) Despite numerous studies on this disease entity, its diagnosis remains challenging, even in intensive care settings.9) Therefore, prompt diagnosis and management are crucial in such cases.

The incidence of acute symptomatic seizures (ASS) following MT for ischaemic stroke is estimated to be approximately 6.1% based on a prospective cohort study.10) NCSE can be a form of ASS, and a retrospective study reported the prevalence of NCSE following MT to be 6.5%, although they included possible NCSE based on the Salzburg criteria.11) Advanced age, successful recanalisation, and haemorrhagic transformation were identified as risk factors for ASS.10) Similarly, blood-brain barrier disruption, free radical effects, increased cerebral excitability, and contrast media neurotoxicity have also been proposed in ASS pathophysiology.12,13) However, the question of whether MT directly increases ASS risk remains unclear. In our case, the absence of restricted diffusion on MRI of the left frontopolar region (identified as the EEG irritative zone) suggests that the moderately damaged cerebral tissue, experiencing temporary hypoxia followed by successful reperfusion, may have acquired epileptogenic properties, consistent with previous experimental data and a case report.14,15)

There are several prediction models for poststroke epilepsy. The SeLECT 2.0 score, the updated version of the known SeLECT (Severity of stroke, Large-artery atherosclerotic aetiology, Early seizures, Cortical involvement, Territory of MCA involvement) score has been proposed to incorporate the increased risk of poststroke epilepsy in patients who present with ASS as status epilepticus.16) In our patient, the calculated SeLECT 2.0 score was 12 points (with a maximum of 13 points), which suggests an 80% risk of poststroke epilepsy 1 year after stroke.17) Therefore, we decided to continue levetiracetam. Additionally, the risk score may be helpful in identifying patients who warrant EEG monitoring following MT, because it partially overlaps with known risk factors for ASS after stroke.18)

There is no consensus on the optimal duration of long-term EEG monitoring. Most critically ill patients experience their first seizure within 24 hrs of continuous EEG; however, extended monitoring is particularly important for comatose patients. In this case, although we were unable to perform 24-hr EEG monitoring, the early detection of electrographic seizures facilitated earlier intervention.

In conclusion, the possibility of NCSE should be actively considered in patients with ischaemic stroke who exhibit prolonged consciousness disturbance even after MT. Prompt long-term EEG monitoring is warranted for early diagnosis and treatment of NCSE.

Acknowledgments

We would like to express our gratitude to all the members of the Department of Neurology and Neurosurgery at Seirei Hamamatsu General Hospital for their insightful guidance and assistance.

Informed Consent

Informed consent was obtained from the patient involved in the study.

Conflicts of Interest Disclosure

All authors declare no conflict of interest.

References
 
© 2024 The Japan Neurosurgical Society

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