Engel classification

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To classify postoperative outcomes for epilepsy surgery, Jerome Engel proposed the following scheme, [1] the Engel Epilepsy Surgery Outcome Scale, which has become the de facto standard when reporting results in the medical literature: [2]

Contents

History

Surgery for epilepsy patients has been used for over a century, but due to technological restrictions and insufficient knowledge of brain surgery, this treatment approach was relatively rare until the 1980s and 90s. [3] Prior to the 1980s, no classification system existed due to the lack of operations performed up until the time. As surgery as a treatment grew more prevalent, a classification system became a necessity. The appropriate evaluation of patients following epilepsy surgery is extremely important, as medical professionals must know the appropriate course of action to follow in order to achieve seizure freedom for patients. [4] Accordingly, the Engel classification guidelines were devised by UCLA neurologist Jerome Engel Jr. in 1987 and made public at the 1992 Palm Desert Conference on Epilepsy Surgery. [5] [6] The Engel classification system has since become the standard in reporting postoperative outcomes of epilepsy surgery. [1]

Overview

In Engel's 1993 summary of the 1992 Palm Desert Conference on Epilepsy Surgery, he annotated his classification system with more detail. [1] The annotation was as follows:

Advantages

The subjectivity of the Engel system leaves much of the postoperative class assignment process to the patients. While many have noted the disadvantages of a classification system where the patients are involved in determining the evaluation, others have praised it. [4] Proponents of the Engel classification guidelines argue that the patients are best able to perceive the worth of the operation because they are the ones experiencing the seizures before and after the treatment.[ citation needed ]

Disadvantages

As is the case for all current methods of reviewing epilepsy surgery outcomes, the Engel classification system has subjective components. [6] A "disabling seizure" is subjective and can vary in definition from person to person. While one epileptic experiencing a seizure when driving a car may find the seizure "disabling," the same magnitude of seizure may be interpreted as mild, and thus "nondisabling," by an epileptic resting in bed. Every class other than class I is also subjective because there is no quantitative definition of what determines a rare occurrence or method to measure worthwhileness. One doctor and patient may consider 2 seizures in a year as a rare occurrence while another doctor may consider 10 in a year as rarely occurring. The worthwhileness of the operation is ambiguous because worth can be interpreted differently by various patients and healthcare professionals. [7] Keeping those caveats in mind, most neurologists and neurosurgeons who specialize in epilepsy would most likely agree, as would many persons with epilepsy and even laypeople, that any seizure that leads to a period of status epilepticus (seizure activity, especially of the tonic-clonic, or grand mal, type, for longer than about five to ten minutes, or more- some now say it should be as little as two- without an intervening return to normal, or any repeat seizures without a return to consciousness) is a medical emergency, objectively a major problem, and cannot be considered a satisfactory outcome (unless perhaps if the person had a fatal or very severe form of a neurodegenerative syndrome or other disease where such severe repeat seizures are not unusual, and there are a number of these diseases; even then, such an outcome is usually still not a cure, just an amelioration of a fatal condition or a very disabling condition). Continuing to have to endure a large number of tonic-clonic seizures (grand mal seizures) over a period of days, months, or even over the course of a year or two, would make it impossible to drive and very hard to hold a job away from home entailing much stress, and would pose limits on one's abilities to safely carry out the activities of daily living without at least some monitoring or assistance.[ citation needed ]

The Engel classification system has been thought of as a cross-sectional grading system by medical professionals because it does not account for long term changes in patients. [7] It has been proposed that it would be more beneficial to reevaluate patients on an annual basis, and the International League Against Epilepsy (ILAE) devised a separate rating scale in 2001 that reevaluates patients on every annual anniversary of their surgery. [4] The ILAE also developed their system in hopes of avoiding many of the subjective components found in the Engel system. [4]

Related Research Articles

Epilepsy Group of neurological disorders causing seizures

Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical activity in the brain. These episodes can result in physical injuries, either directly such as broken bones or through causing accidents. In epilepsy, seizures tend to recur and may have no immediate underlying cause. Isolated seizures that are provoked by a specific cause such as poisoning are not deemed to represent epilepsy. People with epilepsy may be treated differently in various areas of the world and experience varying degrees of social stigma due to the scary nature of their symptoms.

Seizure Period of symptoms due to excessive or synchronous neuronal brain activity

An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with loss of consciousness, to shaking movements involving only part of the body with variable levels of consciousness, to a subtle momentary loss of awareness. Most of the time these episodes last less than two minutes and it takes some time to return to normal. Loss of bladder control may occur.

Corpus callosotomy is a palliative surgical procedure for the treatment of medically refractory epilepsy. In this procedure the corpus callosum is cut through in an effort to limit the spread of epileptic activity between the two halves of the brain.

Lennox–Gastaut syndrome Medical condition

Lennox–Gastaut syndrome (LGS) is a complex, rare, and severe childhood-onset epilepsy. It is characterized by multiple and concurrent seizure types, cognitive dysfunction, and slow spike waves on electroencephalogram (EEG). Typically, it presents in children aged 3–5 years and can persist into adulthood. It has been associated with several gene mutations, perinatal injuries, congenital infections, brain tumors/malformations, and genetic disorders such as tuberous sclerosis and West syndrome. The prognosis for LGS is poor with a 5% mortality in childhood and persistent seizures into adulthood (80%–90%).

Psychogenic non-epileptic seizure Type of neurological disorder

Psychogenic non-epileptic seizures (PNES) are events resembling an epileptic seizure, but without the characteristic electrical discharges associated with epilepsy. PNES fall under the category of disorders known as functional neurological disorders (FND), also known as conversion disorders. A more recent term to describe these events is dissociative non-epileptic seizures. These are typically treated by psychologists or psychiatrists. PNES has previously been called pseudoseizures, psychogenic seizures, and hysterical seizures, but these terms have fallen out of favor.

Temporal lobe epilepsy Chronic focal seizure disorder

Temporal lobe epilepsy (TLE) is a chronic disorder of the nervous system which is characterized by recurrent, unprovoked focal seizures that originate in the temporal lobe of the brain and last about one or two minutes. TLE is the most common form of epilepsy with focal seizures. A focal seizure in the temporal lobe may spread to other areas in the brain when it may become a focal to bilateral seizure.

Reflex seizures are epileptic seizures that are consistently induced by a specific stimulus or trigger making them distinct from other epileptic seizures, which are usually unprovoked. Reflex seizures are otherwise similar to unprovoked seizures and may be focal, generalized, myoclonic, or absence seizures. Epilepsy syndromes characterized by repeated reflex seizures are known as reflex epilepsies. Photosensitive seizures are often myoclonic, absence, or focal seizures in the occipital lobe, while musicogenic seizures are associated with focal seizures in the temporal lobe.

Anterior temporal lobectomy is the complete or partial removal of the anterior portion of the temporal lobe of the brain. The exact boundaries for removal can vary slightly in practice and between neurosurgeons. It is a treatment option for temporal lobe epilepsy for those in whom anticonvulsant medications do not control epileptic seizures, and who have frequent seizures, and who additionally qualify based on a WADA test to localize the dominant hemisphere for language module.

Seizure types most commonly follow the classification proposed by the International League Against Epilepsy (ILAE) in 1981. These classifications have been updated in 2017. Distinguishing between seizure types is important since different types of seizure may have different causes, outcomes and treatments.

Juvenile myoclonic epilepsy (JME), also known as Janz syndrome, is a fairly common form of generalized epilepsy of presumed genetic origin, and is also known as "Castels and Mendilaharsu Syndrome" in South America, representing 5-10% of all epilepsy cases. This disorder typically first manifests itself between the ages of 12 and 18 with sudden brief involuntary single or multiple episodes of muscle(s) contractions caused by an abnormal excessive or synchronous neuronal activity in the brain. These events typically occur either early in the morning or upon sleep deprivation. JME reported as inherited idiopathic epilepsy syndrome (generalized).

Epilepsy surgery involves a neurosurgical procedure where an area of the brain involved in seizures is either resected, ablated, disconnected or stimulated. The goal is to eliminate seizures or significantly reduce seizure burden. Approximately 60% of all people with epilepsy have focal epilepsy syndromes. In 15% to 20% of these patients, the condition is not adequately controlled with anticonvulsive drugs. Such patients are potential candidates for surgical epilepsy treatment.

Ohtahara syndrome (OS), also known as early infantile epileptic encephalopathy (EIEE) is a progressive epileptic encephalopathy. The syndrome is outwardly characterized by tonic spasms and partial seizures within the first few months of life, and receives its more elaborate name from the pattern of burst activity on an electroencephalogram (EEG). It is an extremely debilitating progressive neurological disorder, involving intractable seizures and severe intellectual disabilities. No single cause has been identified, although in many cases structural brain damage is present.

Responsive neurostimulation device or RNS system is a neurostimulation system designed to prevent epileptic seizures.

Fritz E. Dreifuss

Fritz E. Dreifuss, MD was a German-born, New Zealand-educated, American neurologist and subspecialist in epilepsy based at the University of Virginia in Charlottesville, Virginia, US.

Epilepsy is a disorder in which nerve cell activity in the brain is disturbed, causing seizures.During a seizure, a person experiences abnormal behavior, symptoms, and sensations, sometimes including loss of consciousness. There are few symptoms between seizures. A seizure is a single occurrence, whereas epilepsy is a neurological condition characterized by two or more unprovoked seizures. Epilepsy is the most common childhood brain disorder in the United States. Nearly 3 million people have been diagnosed with this disease, while 450,000 of them are under the age of 17. Two thirds of the child population will overcome the side effects, including seizures, through treatment during adolescence. Some treatments include surgery, medication and therapy, surgery however is only done if the child has drug resistant epilepsy.

Myoclonic astatic epilepsy (MAE), also known as myoclonic atonic epilepsy or Doose syndrome, is a generalized idiopathic epilepsy. It is characterized by the development of myoclonic seizures and/or myoclonic astatic seizures. Some of the common monogenic causes include mutations in the genes SLC6A1 (3p25.3),CHD2 (15q26.1), AP2M1 (10q23.2).

Early myoclonic encephalopathy (EME) is a rare neonatal-onset epilepsy developmental and epileptic encephalopathy (DEE) with an onset at neonatal period or during the first 3 months of life. It is marked by the presence of myoclonic seizures but multiple seizure types may occur. The electroencephalographic recording is abnormal with eitherusually a suppression-burst pattern or other significantly abnormal patterns. On most occasions the seizures are drug-resistant. After several months, the seizure pattern may develop into infantile spasms syndrome. The neurological exam is abnormal with a significant risk of early death. Various genetic and metabolic disorders are responsible. At present, EME and Ohtahara syndrome are recorded as distinct patterns in the categorization of epilepsies but both neonatal-onset epilepsy syndromes are considered to be merged in one unique entity. It is a severe type of epilepsy syndrome associated with high level of resistance to treatment and a high risk for cognitive impairment. The myoclonic seizures could be seen in other epilepsy syndromes. Multiple types of childhood epilepsies are usually mentioned as myoclonic epilepsies when the myoclonic seizures are a predominant feature.

People with epilepsy may be classified into different syndromes based on specific clinical features. These features include the age at which seizures begin, the seizure types, and EEG findings, among others. Identifying an epilepsy syndrome is useful as it helps determine the underlying causes as well as deciding what anti-seizure medication should be tried. Epilepsy syndromes are more commonly diagnosed in infants and children. Some examples of epilepsy syndromes include benign rolandic epilepsy, childhood absence epilepsy and juvenile myoclonic epilepsy. Severe syndromes with diffuse brain dysfunction caused, at least partly, by some aspect of epilepsy, are also referred to as epileptic encephalopathies. These are associated with frequent seizures that are resistant to treatment and severe cognitive dysfunction, for instance Lennox-Gastaut syndrome and West syndrome.

A neonatal seizure is a seizure in a baby younger than age 4-weeks that is identifiable by an electrical recording of the brain. It is an occurrence of abnormal, paroxysmal, and persistent ictal rhythm with an amplitude of 2 microvolts in the electroencephalogram, detected in infants younger than 4 weeks. These may be manifested in form of stiffening or jerking of limbs or trunk. Sometimes random eye movements, cycling movements of legs, tonic eyeball movements, and lip-smacking movements may be observed. Alteration in heart rate, blood pressure, respiration, salivation, pupillary dilation, and other associated paroxysmal changes in the autonomic nervous system of infants may be caused due to these seizures. Often these changes are observed along with the observance of other clinical symptoms. A neonatal seizure may or may not be epileptic. Some of them may be provoked by stimulation or suppressed by restraining them.

Drug-resistant epilepsy (DRE), also known as refractory epilepsy or pharmacoresistant epilepsy, is defined as failure of adequate trials of two tolerated and appropriately chosen and used antiepileptic drugs to achieve sustained seizure freedom. The probability that the next medication will achieve seizure freedom drops with every failed AED. For example, after two failed AEDs, the probability that the third will achieve seizure freedom is around 4%. Drug-resistant epilepsy is commonly diagnosed after several years of uncontrolled seizures, however, in most cases, it is evident much earlier. Approximately 30% of people with epilepsy have a drug-resistant form.

References

  1. 1 2 3 Engel, Jerome (1993). Surgical Treatment of the Epilepsies. Lippincott Williams & Wilkins. ISBN   0-88167-988-7.
  2. ↑ Tonini C, Beghi E, Berg AT, Bogliun G, Giordano L, Newton RW, Tetto A, Vitelli E, Vitezic D, Wiebe S (2004). "Predictors of epilepsy surgery outcome: a meta-analysis". Epilepsy Research. 62 (1): 75–87. doi:10.1016/j.eplepsyres.2004.08.006. PMID   15519134. S2CID   40141302.
  3. ↑ Weiner, Howard L. "Surgery". Epilepsy Foundation. Retrieved 1 May 2014.
  4. 1 2 3 4 Durnford, Andrew J.; William Rodgers; Fenella J. Kirkham; et al. (December 2011). "Very good inter-rater reliability of Engel and ILAE epilepsy surgery outcome classifications in a series of 76 patients". Seizure. 20 (10): 809–812. doi: 10.1016/j.seizure.2011.08.004 . PMID   21920780.
  5. ↑ Massachusetts General Hospital. "Engel Epilepsy Surgery Outcome Scale". Massachusetts General Hospital. Archived from the original on 7 April 2014. Retrieved 31 March 2014.
  6. 1 2 Passaro, Erasmo A. "Outcome of Epilepsy Surgery". Medscape. Retrieved 31 March 2014.
  7. 1 2 Yan, Chaohua; James Valeriano; Kevin Kelly; Carol Lane; Jack Wilberger (2009). "Comparison of 2 Classifications of Postoperative Seizure Outcome, Engel vs ILAE Classification, Following Epilepsy Surgery in Adults with Medically Refractory Epilepsy". Johns Hopkins University School of Medicine. Archived from the original on 7 April 2014. Retrieved 3 April 2014.
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