Focal aware seizure secondary to cerebrovascular accident: Case report and differential diagnosis with Limb Shaking

ABSTRACT

Introduction: Although the leading cause of seizures in the older adult population is cerebrovascular accident, limb shaking syndrome is an important differential diagnosis, being a particular clinical manifestation of a transient ischemic attack. Clinical case: We thus describe a clinical case of a 62-year-old Chilean man who suffers a simple focal motor epileptic seizure, with imaging evidence of ischemic injury about 10 days old and significant carotid stenosis which is managed surgically. Discussion: There are different elements that can distinguish an epileptic seizure from a limb shaking syndrome. The pathophysiology of the first corresponds to a post-ischemic irritative phenomenon with a clear electroencephalographic manifestation, while the second is produced by relative hypoperfusion triggered by orthostatism in the context of carotid occlusive disease. The patient’s clinical picture was considered more compatible with an epileptic seizure than with a limb shaking syndrome syndrome.

Key words: Epileptic seizure, limb shaking syndrome, carotid occlusion.

INTRODUCTION

Stroke (Cerebrovascular Accident or CVA) is the most frequent cause of epileptic seizures in the elderly population(1), and there are different reports of epileptic seizures in patients with carotid obstruction(2). On the other hand, “Limb shaking syndrome” (LSS) is a secondary vascular dyskinesia that corresponds to the symptomatic manifestation of a transient ischemic attack (TIA), which is often an indicator of severe carotid occlusion(3,4,5).

Here, we present the case of a Chilean patient who experienced a focal motor seizure without alteration of consciousness as a clinical manifestation of carotid stenosis, and we further discuss this clinical presentation as a differential diagnosis of LSS.

CASE REPORT

A 62-year-old man presents with a complaint of waking up at night with rhythmic involuntary movements of the left upper extremity, which are followed after 10 minutes by similar flexion-extension movements in the ipsilateral lower extremity. The episode lasts for 20-30 minutes, after which he seeks medical attention at our hospital, and he does not experience any similar episodes thereafter. The patient denies any loss of consciousness or sphincter relaxation during the episode and reports no history of similar episodes in the past. On directed questioning, he reveals a medical history of type 2 diabetes mellitus, hypertension, and active smoking.

During the general physical examination, the patient is hemodynamically stable, well-hydrated, and well-perfused. There are no palpable lymph nodes, and bilateral pulses are symmetrical. There are no abnormalities in the cardiopulmonary or abdominal examination, and his lower extremities show no edema or induration.

During the neurological examination, the patient is awake, alert, and oriented to time and space. He can follow commands and recite the days of the week in reverse order. There is no dysarthria or formal language impairment. Cranial nerve examination shows isochoric and reactive pupils, preserved light reflex, intact visual fields by confrontation, normal oculomotor function, symmetric facial movements, intact sensation, absence of nystagmus, and normal lower cranial nerve function. In terms of motor examination, he has preserved muscle bulk and tone in all limbs and moves them symmetrically. Osteotendinous reflexes are present and symmetrical, with bilateral plantar reflexes being flexor. Sensory examination reveals no abnormalities in touch, pain, or proprioception. Cerebellar evaluation does not show dysmetria or dysdiadochokinesia, and there are no signs of meningeal irritation. His gait is unremarkable.

Upon admission, the patient is started on antiepileptic prophylaxis. The diagnostic workup begins with an electroencephalogram during wakefulness, drowsiness, and photostimulation, which is reported as normal, although it should be noted that it was performed when the patient no longer had symptoms. Subsequently, a brain magnetic resonance imaging (Figure 1) is conducted, which reveals a small hyperintense focal lesion in the left periaqueductal region on T2 Flair sequence, and multiple ill-defined hyperintense corticospinal lesions on the right frontoparietal region with residual diffusion restriction. Some lesions show contrast enhancement in the right precentral and parietal regions, with minimal edema. The distribution corresponds to the border zone between the right anterior and middle cerebral artery territories. The MRI report concludes that these lesions are of ischemic origin, approximately 10 days old. Additionally, microangiopathic changes are noted in the white matter.

Further investigation is carried out with a neck AngioCT, which reports atherosclerosis in the right carotid bulb causing 70-80% stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. Significant stenosis (greater than 50%) in the right clinoid-supraclinoid internal carotid artery is also identified, characterized by atherosclerotic plaque with irregular soft components.

With the diagnosis of focal aware seizure without alteration of consciousness secondary to occlusive arterial disease, an echocardiogram is performed. The echocardiogram reveals a preserved ejection fraction (60%), with no segmental abnormalities, severe valvulopathies, or pulmonary hypertension.

Surgical management is offered based on the latest recommendations for carotid stenosis. The patient agrees to undergo angioplasty of the right carotid artery, and he shows favorable hemodynamic evolution after the procedure.

DISCUSSION

In 1982, Cocito et al. studied 141 patients with angiographically demonstrated carotid artery or middle cerebral artery occlusive disease, in which epileptic seizures occurred in 17.3% of patients with carotid occlusion and 10.8% of patients with middle cerebral artery occlusion, with the majority of cases being focal motor seizures(2). The stroke is the most common cause of epileptic seizures in the elderly population(1), with two critical periods of occurrence. Within the first week, the episode is defined as early, and after the first week, it is considered a late event. Early episodes commonly occur within the first days after a stroke and are also known as “acute symptomatic seizures,” while late episodes have a peak incidence between 6 to 12 months after the event. The cumulative risk of a seizure after an ischemic event is 6.1% after the first year, 9.5% after the second year, and 11.5% after 10 years from the event(6).

On the other hand, in 1962, Miller Fisher described for the first time movements similar to epileptic seizures, including “tremors, jerks, twists, and retractions” of the arm and hand, or the arm, hand, and leg, which could herald a stroke in the carotid territory. Since his initial report, numerous additional cases of patients with stereotyped and hyperkinetic movements contralateral to an occluded or severely stenotic carotid artery have been described(3,7,8,4,9,10,11,12,13,14,15,16). The trigger is often described as any change in posture that eventually causes cerebral hypoperfusion. The latency between these maneuvers and the onset of symptoms is usually only a few seconds, while symptoms subside upon patient horizontalization(15,7). The pathophysiology explaining the LSS phenomenon is based on the theory of hypoperfusion or hemodynamic insufficiency, in which carotid stenosis and orthostatism lead to decreased cerebral blood flow in critical cerebral territories(17) .

LSS is an important differential diagnosis of an epileptic seizure (See Table 1). The absence of both electroencephalographic epileptic activity during an episode and interictal epileptiform discharges decisively distinguishes LSS from an epileptic episode , although some patients may present contralateral slow activity(3,4,8,14,18). The fact that LSS is an ischemic, not epileptic, phenomenon has been clinically supported by the absence of facial spasms or Jacksonian gait, the lack of response to anti-seizure medications, and the provocation by positional changes.

Analyzing the presented case, we can highlight the fact that the patient was awakened by the movements, placing the occurrence of this seizure in a context of permanent horizontal position and therefore quickly ruling out the orthostatic component of LSS, which is crucial in causing the relative hypoperfusion that corresponds to the key component of the pathophysiology of this syndrome. On the other hand, the duration reported by the patient of more than 20 to 30 minutes also distinguishes it significantly from LSS, considering that the latter usually does not last more than 5 minutes(5). The response to anti-seizure prophylaxis cannot be used to distinguish the condition since the seizure had ceased by the time the patient presented to our service.

Elements in the clinical case that may argue against the diagnosis of an epileptic seizure could be the unclear presence of Jacksonian gait, although the “migration” of movements from the upper extremity to the lower extremity could be indicative of it, and also the presence of a described normal electroencephalogram. However, it should be considered that the description of the movements was purely made by the patient and their family members and were not witnessed by healthcare personnel capable of distinguishing the clear presence or absence of Jacksonian gait. Similarly, the electroencephalogram was performed at a time when the patient no longer presented the clinical manifestations, so it could easily have been an epileptic seizure with a normal interictal electroencephalogram.

Considering that the MRI report indicates an antiquity of the lesions of at least 10 days, it is probable that the patient actually suffered an infarction in the affected area without any manifest symptoms at that time. It is essential to remember that the latest definitions of stroke by the American Heart Association (AHA) consider pathological imaging evidence or any other objective demonstration of ischemic injury in a defined vascular territory as sufficient evidence of stroke(19). Therefore, considering that strokes are the most important cause of epileptic seizures in older adults, we propose that the pathophysiology of the presented seizure is due to an irritative phenomenon secondary to an old stroke evidenced by the MRI, although without clinical manifestation, secondary to documented carotid artery occlusive disease shown by angiography.

The European Society of Cardiology guidelines define carotid stenosis as a stenosis greater than 50%, estimating severity using the NASCET criteria. Carotid stenosis is defined as “symptomatic” if it has caused symptoms within the last 6 months and “asymptomatic” if there have been no symptoms during that period. For diagnosis, Doppler ultrasound is recommended as the first-line test, with Computed Tomography or Magnetic Resonance angiography as a complementary study to assess the extent and severity. In the present case, the patient was evaluated with an Computed Tomography Angiography that revealed a 70-80% stenosis(20).

The treatment of carotid stenosis includes medical and surgical management. Medical management aims to reduce cardiovascular risk through pharmacological and non-pharmacological measures, optimizing the treatment of conditions such as hypertension, diabetes, and dyslipidemia. Non-pharmacological measures should include promoting smoking cessation and adopting a healthy lifestyle that includes a balanced diet and physical activity. Regarding surgical management, there are two main approaches: open surgery (carotid endarterectomy) or endovascular (carotid artery stenting). The latter option is less invasive with a lower risk of complications, especially cardiac infarction, making it a better choice for patients with prior cervical irradiation. Medical management should be indicated for all patients, while the decision to proceed with surgical treatment depends on the patient’s symptoms and the degree of carotid occlusion. For patients with a life expectancy of more than 5 years, surgical management is indicated in symptomatic cases with stenosis greater than 50%, and in asymptomatic cases with stenosis greater than 60%(20).

Given the patient’s age, symptoms, imaging evidence of ischemic injury, and the degree of carotid stenosis (70-80%), he was considered an optimal candidate for surgical management of his carotid artery occlusive disease and underwent angioplasty of the right carotid artery, with a favorable outcome.

In summary, ischemic injury secondary to a stroke should be suspected when there is a newly developed epileptic seizure in an adult patient, especially in the presence of cardiovascular risk factors. This requires conducting the appropriate diagnostic tests in order to identify the cause of the injury and initiate timely treatment, thereby preventing further ischemic events.

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