Status epilepticus as a novel etiology of Lance–Adams syndrome: a case report

Abstract

Lance–Adams syndrome (LAS) is a rare neurological disorder characterized by action myoclonus. The majority of reported cases have occurred following resuscitation from cardiopulmonary arrest, and to our knowledge, no previous case has been documented in the setting of status epilepticus. In this article, we report a patient who developed LAS secondary to status epilepticus. This single-case report suggests that combination therapy with levetiracetam and clonazepam may be effective. The clinical manifestations of LAS secondary to status epilepticus were milder than those typically observed with other etiologies, and the patient achieved a favorable clinical outcome. However, these preliminary findings are based on isolated evidence and warrant confirmation in larger studies.

Highlights

• •We report a patient who developed LAS secondary to status epilepticus,no previous case has been documented in the setting of status epilepticus. So, our study may expand the etiology spectrum of LAS.
• •The patient got a favorable clinical response to combination therapy with levetiracetam and clonazepam, therefore, our study also contribute to the treatment of LAS induced by status epilepticus.

1. Introduction

Lance–Adams syndrome (LAS), also known as chronic post-hypoxic myoclonus (PHM), is a rare neurological disease characterized by movement-induced myoclonus, with the majority of cases arising after awakening from cardiopulmonary resuscitation (CPR). Herein, we describe a case of LAS with a previously undocumented precipitating factor - status epilepticus, and also demonstrate that combination therapy with levetiracetam and clonazepam may offer a favorable therapeutic response in this specific clinical setting.

2. Case presentation

A 44-year-old female patient was admitted on July 22, 2025, presenting with paroxysmal limb convulsions for 18 days and limb spasms for 5 days. Eighteen days prior to admission, the patient experienced recurrent episodes of limb convulsions accompanied by rigidity and impaired consciousness, with no full interictal recovery of consciousness. After receiving sedative and antiepileptic therapy, she recovered and was discharged on oral levetiracetam 1.0 g daily. Five days before the current admission, she developed intermittent spasms affecting the left upper limb, each lasting from several seconds to tens of seconds, and occasionally involving the left lower limb and facial muscles. These myoclonic jerks were consistently triggered by movement, intentional action or emotional stress, occurring at a frequency of approximately 7–8 times per day (see supplemental material).

The patient had been diagnosed with diabetes mellitus one month prior and was taking metformin. Notably, severe diarrhea developed one day before the onset of epileptic seizures. On admission, vital signs were normal, and neurological examination revealed no obvious abnormalities. Laboratory findings showed elevated alanine aminotransferase at 81 U/L, and glycated hemoglobin (HbA1c) at 6.68%. Serum electrolytes, blood routine, C-reactive protein, renal function, coagulation function, and thyroid function were all nearly normal. Cerebrospinal fluid (CSF) analysis demonstrated normal glucose, protein and cell counts, and pathogen screening as well as autoantibody panels for autoimmune encephalitis (both in serum and CSF) returned negative. Cranial magnetic resonance imaging (MRI) performed on July 1, 2025, was normal; however, a follow-up MRI on July 14, 2025, revealed cytotoxic edema in the bilateral parietal cortex (see Fig. 1). A subsequent MRI on July 25, 2025, showed decrease of these lesions with no restricted diffusion. Electroencephalography (EEG) on July 15, 2025, demonstrated generalized slow-wave activities in the right posterior-centro-parieto-occipital region, with a few scattered sharp-wave discharges. During the second hospitalization, an EEG performed on July 25, 2025, revealed approximately 3–4 Hz slow-wave discharges, some of which were overlapped by spike-like fast activities coincident with clinical myoclonic jerks (see Fig. 2).

Fig. 1.

The MRI shows cytotoxic edema in bilateral parietal cortex.

Fig. 2.

EEG shows slow-wave discharges and spike-like fast activities.

An initial diagnosis of status epilepticus with myoclonus was made. The presumed pathogenesis was metformin-induced lactic acidosis, triggered by severe diarrhea, which subsequently caused status epilepticus. Combined with the neuroimaging findings, it was postulated that status epilepticus gave rise to cerebral ischemia and hypoxia, thereby leading to secondary myoclonus. During this period, the antiepileptic regimen was adjusted to levetiracetam 1.5 g/day combined with lamotrigine 50 mg/day; however, symptom control remained disappointing.

Upon review of the literature, the diagnosis was revised to Lance–Adams syndrome (LAS). The treatment was accordingly modified to levetiracetam 1.5 g/day plus clonazepam 0.5 mg every 8 h. At follow-up, the patient reported no further episodes. An EEG on December 3, 2025, showed marked reduction in both slow-wave discharges and spike-like fast activities compared with previous recordings (see Fig. 3). Furthermore, a cranial MRI on January 17, 2026, demonstrated complete disappearance of the previous parietal cortical signal abnormalities (see Fig. 4). Over a six-month follow-up period, no myoclonus was observed, and clonazepam was successfully discontinued.

Fig. 3.

EEG shows less slow-wave discharges and spike-like fast activities in follow-up.

Fig. 4.

The MRI shows normal in follow-up.

3. Discussion

Lance–Adams syndrome (LAS) typically manifests within days to months following a hypoxic–ischemic brain insult. Its clinical features include sudden, transient and recurrent myoclonic jerks that are predominantly triggered by voluntary movement, intended action, sensory stimulation or emotional tension, with a predilection for the distal limbs and infrequent facial involvement [1], [2]. In this case, the patient developed movement-induced myoclonus approximately 10 days after status epilepticus, a phenomenological manifestation consistent with the clinical characteristics of LAS.

Notably, the majority of previously reported LAS cases have been attributed to cerebral hypoxia resulting from cardiac arrest, asthma, asphyxia or poisoning, etc. In contrast, our patient developed myoclonus after status epilepticus, an etiology that has not, to our knowledge, been documented in the literature. Furthermore, the degree of hypoxic brain injury in this case appeared milder than that typically observed in other etiologies, which may account for the more favorable clinical outcome and complete radiological disappearance seen in our patient.

The differential diagnosis between LAS and myoclonic epilepsy warrants careful consideration. Unlike LAS, myoclonic epilepsy usually presents with disturbance of consciousness and occurs within 72 h after cardiac arrest, and is associated with an extremely poor prognosis and high mortality. Its clinical manifestations are predominantly spontaneous, non-intentional myoclonus, and the EEG frequently reveals generalized epileptic discharges and burst inhibition, whereas diffuse slow-wave activity is uncommon [3]. These distinguishing features supported the exclusion of myoclonic epilepsy in our patient.

The pathophysiological mechanisms of LAS remain incompletely elucidated. Proposed contributors to LAS include abnormal cortical discharges, dysfunctional circuits in the cerebellum, brainstem and thalamus, and neurotransmitter imbalances. The characteristic EEG of LAS is slow-wave complex with multiple spines in the central midline region, suggesting possible cortical abnormal discharges. It is known that both 5-hydroxytryptamine (5-HT) and γ-aminobutyric acid (GABA) are implicated in myoclonus pathogenesis. GABA may interact with the serotonergic system to reduce myoclonus, and 5-HT deficiency in the inferior olivary nucleus has also been linked to disease development. Once 5-HT deficiency occurs, neurons may remain in a persistently hyperexcitable state, generating sustained rhythmic discharges. Additionally, some studies have reported reduced N-acetylaspartate/creatine (NAA/Cr) ratios in affected patients, indicating decreased neuronal activity in the posterior cingulate gyrus and leukocortical neurons, potentially reflecting hypoxic–ischemic injury. Neuroimaging data have further proved multiple brain regions are participated in myoclonus generation, including the frontotemporal lobes, ventrolateral thalamus, basal ganglia, pontine tegmentum, midbrain, cerebellum, and hippocampus. Repetitive thalamocortical discharges, potentially triggered by the ventrolateral nucleus and the Guillain–Mollaret triangle, may contribute to myoclonus onset. Thus, circuit dysfunction involving the inferior olivary nucleus, red nucleus, and deep cerebellar nuclei may represent a key mechanism in LAS [4], [5], [6].

Examinations of LAS primarily include EEG, neuroelectrophysiology and cranial MRI. EEG findings in LAS are heterogeneous. Some patients show normal, and others show epileptic discharges. Cranial MRI is often unremarkable in most patients, although some may show limited cortical diffusion abnormalities; lesions have also been reported in the cerebellum, lentiform nucleus, periventricular regions and thalamus [7]. In our patient, EEG recording showed interference by significant limb myoclonus during clinical episodes, but intermittent 3–4 Hz slow-wave discharges were observed, some of which were overlapped by spike-like fast activities. Concurrently, cranial MRI demonstrated limited diffusion in the right parietal lobe, which completely disappeared on follow-up imaging. These auxiliary findings collectively supported the diagnosis of LAS and were consistent with an underlying ischemic–hypoxic mechanism.

To date, no standardized treatment guidelines exist for LAS. Pharmacological management remains largely symptomatic, primarily relying on antiepileptic drugs. Levetiracetam, valproate sodium, and clonazepam have demonstrated efficacy in LAS, and combination regimens may achieve superior outcomes. Emerging evidence from limited case reports suggests that perampane and zonisamide may also be beneficial. Non-pharmacological treatments, such as globus pallidus internus deep brain stimulation (GPi-DBS) and repetitive electroconvulsive therapy, have shown potential but require further clinical validation [8], [9]. The long-term prognosis for most LAS patients is generally favorable, with many achieving independent self-care; however, some individuals may experience severe myoclonus, even disability. In our patient, the distinctive etiology and reversible MRI lesions may have contributed to a satisfactory response to antiepileptic therapy, particularly clonazepam. Therefore, the combination of levetiracetam and clonazepam may represent a relatively effective treatment option for LAS secondary to status epilepticus.

However, we also acknowledge the limitations of this study. As this is a single-case report (N = 1), the findings—including the clinical efficacy observed with the combination of levetiracetam and clonazepam, as well as the milder manifestation of the disease—cannot be definitively generalized to the broader patient population. Therefore, larger prospective studies or randomized controlled trials are needed to validate these observations and determine the generalizability of this treatment approach to the wider subpopulation.

4. Conclusion

In summary, we report a case of LAS with a previously unreported etiology - status epilepticus, and also suggest that levetiracetam combined with clonazepam may offer a favorable therapeutic strategy for this clinical setting.

The following are the supplementary data related to this article.

Supplementary Video 1

Recording Episodes on Video.

CRediT authorship contribution statement

Fuli Wang: Writing – original draft, Validation, Project administration, Investigation, Data curation, Conceptualization. Lei Xu: Investigation, Data curation. Ting Huang: Writing – review & editing, Methodology. Xing Liu: Methodology, Investigation, Formal analysis, Data curation. Zhongling Gu: Methodology, Investigation, Data curation. Yunbo Chen: Writing – review & editing, Validation, Supervision, Conceptualization.

Ethics statement

The study involving a human participant was reviewed and approved by the Ethics committee of Zigong Fourth People's Hospital, Zigong, China. The patient provided her written informed consent to participate in this study. Written informed consent was obtained from the individual for the publication of any potentially identifiable images or data included in this article.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.