Neurology: Seizures

Appendix A: Background Information On Seizures

Introduction
Epidemiological, molecular, biological, and genomic understanding of seizures and epilepsy has been advancing rapidly over the past 50 years leading to variation in the manner in which scientific reports are focused and the basic terminology used to discuss the entities being studied. For over the past 50 years, the International League Against Epilepsy (ILAE – ww.ilae.org) has had the role of defining terminology. Thus, this discussion will follow definitions promulgated by ILAE. As noted, however, terminology has evolved over that time, leading to difficulty in pooling or comparing conclusions from various studies.

Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures, and by the neurobiologic, cognitive, psychological, and social consequences of this condition. The definition of epilepsy requires the occurrence of at least one epileptic seizure.11 In 2010, the ILAE Commission revised the terminology and concepts for definition and classification of seizures and epilepsy as follows: “an epileptic seizure is a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.”12

ILAE recently updated the definition of epilepsy as a “disease of the brain” characterized by any of the following conditions: 1) at least two unprovoked seizures more than 24 hours apart; 2) one unprovoked seizure and a probability of further seizures similar the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years; and 3) diagnosis of an epilepsy syndrome.1

Classification of Epileptic Seizures
In 2010, ILAE adopted an updated schema for classification of seizures, partly as a result of advances in neuroimaging, biochemical understanding, and genomics.12

• Focal Seizures
  Focal seizures originate within a network of neurons limited to one hemisphere of the brain and the signs and resulting symptoms depend on precisely where the disruptions in brain activity occur. Focal seizures may have motor, sensory, autonomic, or other symptoms (e.g., hallucinations, déjà vu). Focal seizures are sub-categorized as with or without impairment of consciousness or awareness.
• Generalized Seizures
  Generalized seizures originate within a network of neurons that distribute to both hemispheres of the brain. They may vary considerably in their clinical features, from subtle alterations in consciousness to body convulsions. Generalized seizures are categorized as the following:
  • Tonic-clonic (in any combination) – A type of seizure that starts with a sudden loss of consciousness and generalized stiffening of body (tonic phase) followed by contraction of the muscles (clonic phase).
  • Absence – Often common in childhood, absence (previously called petit mal) seizures are generally brief lapses in awareness. Some clonic motor activity may occur.
    • Typical
    • Atypical
    • Absence with special features
      • Myoclonic absence
      • Eyelid myoclonia
  • Myoclonic – Characterized by sudden and brief muscular contractions, myoclonic seizures may involve any group of muscles and can resemble tremors.
    • Myoclonic
    • Myoclonic atonic
    • Myoclonic tonic
  • Clonic – Consists of alternating successions of contractions and partial relaxations of a muscle.
  • Tonic – Brief seizures involving a sudden onset of increased muscle tone.
  • Atonic – Characterized by a sudden loss of muscle tone, atonic seizures begin suddenly and cause the individual, if standing, to fall quickly to the floor.
• Unknown (epileptic spasms)

Epilepsy Syndromes
A number of different syndromes of epilepsy have been differentiated with various implications in terms of evaluating persons for effect on safe and effective performance of essential law enforcement job functions:

• Juvenile myoclonic epilepsy – a generalized seizure disorder that appears in early adolescence and is usually characterized by bilateral myoclonic jerks. Remission is uncommon.
• Lennox-Gastaut syndrome – occurs in children and is associated with multiple seizure types. The epilepsy is usually poorly controlled.
• Mesial temporal lobe epilepsy syndrome – usually associated with complex partial seizures and with pathology to the hippocampus. Is sometimes refractory to treatment with anticonvulsants, but tends to respond well to surgical intervention.

Other syndromes associated with genetic abnormalities, most of which will have significant problems from the underlying syndrome that may also adversely affect the ability to safely and effectively perform essential law enforcement job functions.

Risk of Recurrence
A primary issue of concern in assessing the safety of the LEO with a seizure disorder for performing essential law enforcement job functions is prediction of the risk of a recurrent seizure.

Single Unprovoked Seizure

Several studies have looked at the cumulative risk of recurrence of seizure following a single unprovoked seizure.13 Data from 5 studies involving adult patients with single unprovoked seizures were reported as the cumulative risk of recurrence of seizure at specified follow-up periods14-18:

The additional risk of recurrence does not fall close to a 1% risk level until at least year 5 or beyond,15,16,17 other than in the reports by Hopkins and Elwes reports.14,18 Additionally, it should be mentioned that treatment with anticonvulsants after a single unprovoked seizure does not significantly reduce relapse. According to the First Seizure Trial Group (1997), the treatment of first tonic-clonic seizure does not improve the prognosis of epilepsy.19 In a randomized trial of treated and untreated patients, 87% of treated patients had no seizures for a year; 68% had no seizures for 2 years; and in treated patients, 83% and 60% achieved similar endpoints.

Epilepsy
In one large study, after 9 years from the index seizure, the 5-year remission rate was an average of 71%.7 Another study found the relapse rate in adults after withdrawal of AEDs was 39% to 74% at 1 year, and 35% to 57% at 2 years.8

The risk of recurrence after one or more seizures is related to etiology and other factors. There is no reliable risk of recurrence applicable to all individuals with a seizure disorder.

Adapted from Seizure Disorders and Commercial Motor Vehicle Driver Safety. FMCSA, Expert Panel Recommendations. October 15, 2007.

Seizure Recurrence in the Setting of Withdrawal of Anti-epileptic Drugs
About 1/3 of patients seizure-free on anti-epileptic drugs (AEDs) will relapse.20-24 AED withdrawal probably increases the risk of seizures during the withdrawal period, and may increase the risk in the 1 to 2 years after withdrawal, although there is a possibility that these patients would have relapsed nonetheless. Also, certain patients who have recurrent seizures do not achieve control when AEDs are restarted. Some risks of recurrence can be identified. According to Specchio and Beghi, “The relapse rate was highest in the first 12 months (especially in the first 6 months) after withdrawal and tended to decrease thereafter. Based on a previously published meta-analysis of data published up to 1992, the pooled relapse risk was 25% (95% CI 21-30%) at 1 year and 29% (95% CI 24-34%) at 2 years after AED withdrawal. The factors associated with a higher-than-average risk of seizure relapse included adolescent-onset epilepsy, partial seizures, the presence of an underlying neurological condition and abnormal EEG findings at the time of AED withdrawal in children.” 8

Sequelae of Seizures and Epilepsy
At present, there is reasonable evidence of structural and functional adverse effects on the brain from epileptic electrical discharges, particularly those that involve greater parts of the brain. Thus, in performing fitness-for-duty evaluations of persons with either a relatively recent single seizure of any class outlined above (or of persons with epilepsy fitting a category above that would not be recommended for restriction), the evaluation should include a specific focus on functions such as short- and long-term memory, executive functions, and emotional control. The adverse effects of temporal lobe epilepsy and surgical treatment on memory have been known and studied for decades.25 Frontal lobe epilepsy and surgical treatment are also associated with neuropsychological aberrancies that may have adverse effects on safe and effective performance of essential law enforcement job functions.26

As the current diagnosis of epilepsy promulgated by ILEA implies, psycho-social ramifications of the diagnosis of epilepsy may represent a significant burden on the person in question. While specific guidelines do not exist for correlating a seizure disorder (single unprovoked seizure not in a remote time or epilepsy) with psychological effect and possible adverse effect on safe and effective performance of essential law enforcement job functions, fitness-for-duty evaluations should take this aspect into consideration.