Prolonged Acute Convulsive Seizures

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What is a prolonged acute convulsive seizure?

To date, the definition of a prolonged acute convulsive seizure (PACS) is controversial and vague.

Prolonged Acute Convulsive Seizure

The National Institute for Health and Care Excellence (NICE) defines PACS as “any convulsive seizure that continues for more than 2 minutes longer than a person’s usual seizure¹”

Convulsive Status Epilepticus

Convulsive status epilepticus (CSE) is defined by the International League Against Epilepsy (ILAE) as abnormal prolonged tonic-clonic seizures lasting longer than 5 minutes (t1) and it should be treated in 30 minutes (t2), because it can cause irreversible neurological damage and neuronal death. This conceptual definition has two operational time dimensions: t1 (the time point when the seizure should be considered “abnormally prolonged”), and t2 (the time beyond which there could be long-term consequences).^2,3

CSE is conceptually defined as a seizure lasting 30 min or more, but operationally defined (for the purposes of administration of emergency treatment) as a seizure lasting 5 min or more.²

Immediate emergency treatment, in community settings of prolonged tonic-clonic seizures (lasting more than 5 minutes) is recommended to try to prevent progression and potential neurological consequences, both in children and adults. ^1-3

Epidemiology

High prevalence of epilepsy in children is associated with differences in the gamma-aminobutyric (GABA) system^4-6
CSE is one of the most common medical neurological emergencies in childhood,^7,8 with the highest incidence in the first 5 years of life and high mortality and morbidity rates.⁸
Although the incidence of CSE can vary depending on the defined duration of CSE^9,10 it ranges between 10 and 73 cases per 100,000 children per year globally^11-12 and 15.8 per 100,000 per year in adults.¹³

Risk factors for PACS or CSE

Epilepsy can have many causes.^13-19 The risk factors associated with PACS and CSE may include:

• History of previous prolonged seizures ^{13, 16, 17, 19}

• Genetic factors ^15,17

• Developmental brain abnormalities ^13,19

• Infections ^{13, 14-18}

• Metabolic derangement ^{13, 14, 18}

• Febrile convulsions ^{13, 16, 17}

• Traumatic brain injury ^{13, 14 ,18, 19}

• Brain tumours ^{13, 14 ,18}

• Developmental neurological abnormality ^{13, 19}

• Cerebrovascular insult (e.g. stroke) ^{13-15, 18}

• Non-compliance or inappropriate antiepileptic treatment ^{13,16, 18}

Others may include alcohol ¹⁸, hypoxia ¹⁸, very young or very old age ^{17, 19}

WHY prolonged acute convulsive seizures should be treated early

Most convulsive seizures self-terminate within two minutes.²¹ The longer a seizure lasts, the less likely it is to stop spontaneously¹⁹. Seizures over 5 minutes are likely to be prolonged leading to continuous seizure activity. ²

Permanent neurological and mental deterioration may result from CSE and the risks of morbidity are increased the longer the duration of the episode. ²⁰

After 30 minutes, long-term consequences occur, including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures.²

Early intervention in the community setting is key to helping to prevent CSE and reducing the risk of negative consequences or prolonged seizures. These may include: ^{1, 2, 20, 21}

Later development of epilepsy

Long-term neurological damage

Cognitive impairment

Psychiatric impairment

Immediate emergency treatment, in community settings of prolonged tonic-clonic seizures (lasting more than 5 minutes) is recommended to try to prevent progression and potential neurological consequences, both in children and adults. ^1-3

WHEN prolonged acute convulsive seizures should be treated

The seizure activity persists, the more difficult they are to stop. ²²

For this reason, a 5 minutes threshold has been set as a critical time to start treatment.^1,22

Given that most seizures initiate outside of hospital or clinical settings³³, it is important to have a seizure action plan (SAP) that aids appropriate giving of emergency treatment.^{1, 23} This may also be know as emergency management or care plan, and should cover details of any emergency medicine that has been prescribed, who is trained to use it and when to give it.¹ This approach is important in managing both prolonged seizures and CSE, both should be treated as a medical emergency.¹ Treatment is more likely to be successful if given in early (pre-hospital) rather than later stages²⁰ and so should commence as soon as it is apparent the seizure is persisting (5 minutes or more) ^1,20

A SAP is designed to offer essential guidance for people with epilepsy and their caregivers. It provides information on the steps that should be taken during a potential seizure emergency, ensuring that everybody involved is well-prepared to respond effectively^{1, 23, 24}. This personalised plan is beneficial for anyone who regularly interacts with the person with epilepsy, including parents, caregivers, relatives, teachers, coworkers, and friends.²³

A SAP not only serves as a management tool but also as a critical resource for fostering a supportive environment for those with epilepsy.²³ It include detailed information on seizure characteristics, anti-seizure medication (ASM), including rescue treatments, and contact instructions. Additionally, it provides other relevant medical and emergency support information tailored to the patient’s needs.²⁴

HOW to treat prolonged convulsive seizures

Treatment for prolonged seizures lasting 5 minutes or more (CSE) should be detailed in an individualised emergency management plan and followed when an episode occurs.¹

In the absence of emergency management plan being available, buccal midazolam or rectal diazepam are recommended as first line community rescue medication for seizures lasting 5 minutes or more in children, young people and adults.¹

The administration of the benzodiazepines diazepam or midazolam is the first-line therapy for the initial management of in the community.¹

Community setting:

› Rectal: diazepam^36-38
› Oromucosal: midazolam oromucosal solution^39-41

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› Nasal: midazolam nasal^39,40

Psychiatric disorders

› Intravenous: diazepam⁴¹, midazolam⁴¹, lorazepam⁴¹
› Intramuscular: diazepam⁴¹, midazolam⁴¹

Local guidance on prolonged convulsive seizures

Local guidelines may offer additional specifics regarding drug choices, dosages, and healthcare system-specific protocols but they should align with the principles outlined by:

• International League Against Epilepsy (ILAE).²⁵

• National Institute for Health and Care Excellence (NICE).¹

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References
1 National Institute for Health and Care Excellence (NICE). https://www.nice.org.uk/guidance/ng217/chapter/7-Treating-status-epilepticus-repeated-or-cluster-seizures-and-prolonged-seizures [Accessed December 2025]
2 Trinka E, Cock H, Hesdorffer D, Rossetti AO, Scheffer IE, Shinnar S, Shorvon S, Lowenstein DH. A definition and classification of status epilepticus–Report of the ILAE Task Force on Classification of Status Epilepticus. Epilepsia. 2015 Oct;56(10):1515-23.
3 Trinka E, Kälviäinen R. 25 years of advances in the definition, classification and treatment of status epilepticus. Seizure. 2017 Jan;44:65-73.
4 Rakhade SN, Jensen FE. Epileptogenesis in the immature brain: emerging mechanisms. Nat Rev Neurol. 2009 Jul;5(7):380-91.
5 Zimmern V, Korff C. Status Epilepticus in Children. J Clin Neurophysiol. 2020 Sep;37(5):429-433.
6 Silverstein FS, Jensen FE. Neonatal seizures. Ann Neurol. 2007 Aug;62(2):112-20.
7 Alford EL, Wheless JW, Phelps SJ. Treatment of Generalized Convulsive Status Epilepticus in Pediatric Patients. J Pediatr Pharmacol Ther. 2015 Jul-Aug;20(4):260-89.
8 Becker LL, Gratopp A, Prager C, Elger CE, Kaindl AM. Treatment of pediatric convulsive status epilepticus. Front Neurol. 2023 Jun 29;14:1175370.
9 Raspall-Chaure M, Chin RFM, Neville BG, Bedford H, Scott RC. The epidemiology of convulsive status epilepticus in children: a critical review. Epilepsia. 2007 Sep;48(9):1652-1663.
10 Cross JH. Setting the scene: definition of prolonged seizures, acute repetitive seizures, and status epilepticus. Do we know why seizures stop? Epileptic Disord. 2014 Oct;16 Spec No 1:S2-5.
11 Chin RF, Neville BG, Peckham C, Bedford H, Wade A, Scott RC; NLSTEPSS Collaborative Group. Incidence, cause, and short-term outcome of convulsive status epilepticus in childhood: prospective population-based study. Lancet. 2006 Jul 15;368(9531):222-9.
12 Singh RK, Gaillard WD. Status epilepticus in children. Curr Neurol Neurosci Rep. 2009 Mar;9(2):137-44.
13 Leitinger M, Trinka E, Giovannini G, Zimmermann G, Florea C, Rohracher A, Kalss G, Neuray C, Kreidenhuber R, Höfler J, Kuchukhidze G, Granbichler C, Dobesberger J, Novak HF, Pilz G, Meletti S, Siebert U. Epidemiology of status epilepticus in adults: A population-based study on incidence, causes, and outcomes. Epilepsia. 2019 Jan;60(1):53-62.
14 McKenzie KC, Hahn CD, Friedman JN. Emergency management of the paediatric patient with convulsive status epilepticus. Paediatr Child Health. 2021 Jan 21;26(1):50-66.
15 National Institute of Neurological Disorders and Stroke. “Epilepsy and Seizures“. Available at: https://www.ninds.nih.gov/health-information/disorders/epilepsy-and-seizures#:~:text=Epilepsy%20has%20many%20possible%20causes,tumors%2C%20or%20other%20identifiable%20problems. Accessed on December 2025.
16 Bast T. Syndromes with very low risk of acute prolonged seizures. Epileptic Disord. 2014 Oct;16 Spec No 1:S96-102.
17 Neubauer BA, Hahn A. Syndromes at risk of status epilepticus in children: genetic and pathophysiological issues. Epileptic Disord. 2014 Oct;16 Spec No 1:S89-95.
18 Martindale JL, Goldstein JN, Pallin DJ. Emergency department seizure epidemiology. Emerg Med Clin North Am. 2011 Feb;29(1):15-27.
19 Shinnar S. Who Is at Risk for Prolonged Seizures? J Child Neurol. 2007;22:14S-20S.
20 Walker MC and Shorvon SD. The Fifteenth Epilepsy Teaching Weekend on September 2015. Epilepsy Society. Chapter 33.
21 Scott, 2014. THE EDUCATIONAL JOURNAL OF THE INTERNATIONAL LEAGUE AGAINST EPILEPSY Scott RC. What are the effects of prolonged seizures in the brain? Epileptic Disord. 2014 Oct;16 Spec No 1(Spec No 1):S6-11.
30 Lipka and Bulow, 2003: Lipka K, Bülow HH. Lactic acidosis following convulsions. Acta Anaesthesiol Scand. 2003 May;47(5):616-8.
31 Smith RA, Martland T, Lowry MF. Children with seizures presenting to accident and emergency. J Accid Emerg Med. 1996 Jan;13(1):54-8.
22 Chin RF. 2014. The Educational Journal of the International League against Epilepsy. What are the best ways to deliver benzodiazepines in children/patients with prolonged convulsive seizures? Epileptic Disord. 2014 Oct;16 Spec No 1:S50-8.
23 Volkers N. Seizure action plans: More than management tools for epilepsy. Epigraph 2024; 26(2): 94-99.
24 Patel AD, Becker DA. Introduction to use of an acute seizure action plan for seizure clusters and guidance for implementation. Epilepsia. 2022 Sep;63 Suppl 1:S25-S33.
25 International League Against Epilepsy. https://www.ilae.org/

This information is intended for use by healthcare professionals.

NXUK/E/1125/01 December 2025