Seizure Types

Seizure Types

Epilepsy is a neurological condition that is characterized by a wide variety of symptoms and subtypes. The International League Against Epilepsy (ILAE) is an organization that is responsible for defining many important diagnostic and clinical classifications of the disorder. In 2017, the ILAE published revised criteria for various seizure types organized under focal, generalized, and unknown onset. These are further subdivided into motor and nonmotor symptoms. Seizures are typically classified by type of onset and the initial most prominent symptom (i.e., “focal atonic seizure”).  Below is a brief description of each seizure type that corresponds to different onset patterns.

 

Focal Onset Seizures

Seizures that arise from one specific area of the brain (such as in temporal lobe or frontal lobe epilepsy) are classified as focal onset. Focal onset seizure types also generally include the qualifiers “aware” or “impaired awareness” in order to describe whether or not individuals are aware of themselves and the environment during the seizure. Either awareness condition may be present along with the typical motor and/or nonmotor symptoms. Focal aware seizures and focal impaired awareness seizures were previously termed “simple partial seizures” and “complex partial seizures,” respectively. Following is a list of motor and nonmotor symptoms associated specifically with focal onset seizures (1).

 

Motor Symptoms

Automatisms refer to relatively coordinated, repetitive motor activity that may resemble a voluntary movement (2). These movements may be a continuation of activity occurring prior to the seizure (a perseverative movement) or might begin during a seizure (de novo) (3). Examples include lip smacking, tooth grinding, hand or foot tapping, or hand gestures (2). Another motor symptom, hyperkinetic activity, refers to a general increase of the rate of motor activity, seen primarily as sequential movements that are at times inappropriate such as rocking, thrashing, or leg pedaling (2).

 

Nonmotor Symptoms

Nonmotor symptoms associated with focal onset seizures vary widely across multiple domains. Autonomic symptoms refer to sensations that originate from changes in the autonomic nervous system, such as increased heart rate or gastrointestinal issues (2). Symptoms may also span cognitive, emotional, and sensory domains. In addition to cognitive impairment, more subtle shifts in cognition may be evident such as feelings of déjà vu or hallucinations (1). Both positive and negative emotional symptoms can occur in focal seizures, and emotional expression may or may not be correlated with subjective mood (1). Finally, while behavioral arrest (the decrease of ongoing motor activity) may be briefly observed at the start of the seizure, this may be used as a nonmotor qualifier only if it is the predominant symptom (1).

 

Generalized Seizures

Generalized seizure onset refers to seizures that do not originate from a specific brain region and typically involve both hemispheres (2). It is important to note that generalized seizures may be identified as propagating from a focal brain region. In this case, the term “focal to bilateral seizure” is used, replacing the former term “secondary generalized” (1). As seen in focal onset seizures, both motor and nonmotor symptoms specific to generalized onset may be present and are discussed below.

 

Motor Symptoms

Tonic-clonic seizures refer to the classic convulsive seizure presentation (formerly termed “grand mal” seizures) consisting of stiffened muscles (tonic phase) followed by rhythmic jerking of the muscles (clonic phase). Loss of consciousness is typical, and symptoms generally last from one to three minutes, although they may occur for longer durations (4). Myoclonic symptoms refer to sudden, brief convulsions that last no longer than 100 milliseconds and are more irregular than other convulsive symptoms (2, 4). Differing convulsive activity may also occur at similar rates within the same seizure event, forming myoclonic-tonic-clonic symptoms. Finally, myoclonic-atonic symptoms are also associated with generalized onset seizures, consisting of myoclonic symptoms coupled with the sudden loss or decrease of muscle tone (described in more detail below).

 

Nonmotor Symptoms

Nonmotor symptoms associated with generalized onset seizures are also called “absence” seizures. These are described as either typical or atypical, with atypical absence seizures exhibiting prolonged onset or cessation and unusual EEG readings. In fact, EEG analysis is often used to distinguish between typical and atypical absence symptoms. Absence seizures present as abrupt interruption of motor activity which may be coupled with a blank stare and unresponsiveness. These seizures last a few seconds to half a minute, and typically rapid recovery is observed. Additional absence classifications include myoclonic absence seizures, during which brief rhythmic myoclonic movement occurs, as well as eyelid myoclonia consisting of jerks of the eyelids (4).

 

Focal and Generalized Seizures

A number of motor symptoms are associated with both generalized and focal onset seizures, and are described in more detail below.

 

Atonic

Atonic symptoms consist of a sudden loss or decrease of muscle tone (paralysis or paresis) lasting longer than one to two seconds (2). This may occur in either the limbs, head, or torso, and these seizures have sometimes been described as “drop attacks” due to sudden falling (5). The degree of awareness is typically not specified in focal atonic seizures (1).

 

Epileptic Spasms

The clinical presentation of epileptic spasms varies widely based on type of movement. Broadly speaking, spasms are typically defined as the sudden extension and retraction of muscles which can occur anywhere in the body and last for approximately one second (longer than myoclonic seizures but shorter than clonic seizures) (2). More severe spasms may take place in the neck, head, or hip while minor spasms may manifest as isolated head nods or shrugs (6). Epileptic spasms have often been reported to occur more commonly upon awakening or prior to falling asleep (6). Similar to atonic seizures, the degree of awareness is typically unspecified in focal epileptic spasms (1).

 

Tonic/Clonic/Myoclonic

While the combined tonic-clonic presentation is specifically associated with generalized onset seizures, separate tonic and clonic events may have either focal or generalized onset. Tonic symptoms consist of ongoing muscle contraction lasting up to a few minutes while clonic symptoms refer to rhythmic jerking movements that may be symmetric or asymmetric. Discussed in more detail above, myoclonic motor symptoms may also be observed in both seizure onset types (4).

 

Unknown Onset

A handful of symptoms listed above can also be associated with seizures of unknown onset, including tonic-clonic seizures, epileptic spasms, and behavioral arrest (1). Unclassified seizures refer to those that are not readily categorized into an identifiable pattern (4).

 

Treatment

The most common treatment is medication, and usually anti-convulsants.  A neurologist is the branch of medical doctor that deals with seizures, and it is best to see a neurologist who specializes in epilepsy.  Neurofeedback has also been successful in treating seizures (7), and has the advantage of avoiding medication and its side-effects.  The results tend to be permanent.  Unfortunately insurance companies rarely support biofeedback or neurofeedback.

— S. Jacobs & J. Thomas

 

References

  1. Fisher, R, Cross, J, French, J, Higurashi, N, Hirsch, E, Jansen, F, … & Scheffer, I (2017). Operational classification of seizure types by the International League Against Epilepsy: Position Paper of the ILAE Commission for Classification and Terminology. Epilepsia58(4), 522-530.
  2. Blume, W, Lüders, H, Mizrahi, E, Tassinari, C, van Emde Boas, W, & Engel Jr, Ex‐officio, J (2001). Glossary of descriptive terminology for ictal semiology: report of the ILAE task force on classification and terminology. Epilepsia42(9), 1212-1218.  https://onlinelibrary.wiley.com/doi/full/10.1046/j.1528-1157.2001.22001.x
  3. Sadleir, L, Scheffer, I, Smith, S, Connolly, M, & Farrell, K (2009). Automatisms in absence seizures in children with idiopathic generalized epilepsy. Archives of neurology66(6), 729-734.
  4. Fisher, R, Cross, J, D’souza, C, French, J, Haut, S, Higurashi, N, … & Peltola, J (2017). Instruction manual for the ILAE 2017 operational classification of seizure types. Epilepsia58(4), 531-542.
  5. Kovac, S, & Diehl, B (2012). Atonic phenomena in focal seizures: nomenclature, clinical findings and pathophysiological concepts. Seizure21(8), 561-567.
  6. Goldstein, J, & Slomski, J (2008). Epileptic spasms: a variety of etiologies and associated syndromes. Journal of child neurology23(4), 407-414.
  7.  Sterman, M (2010). Biofeedback in the treatment of epilepsy.  Cleveland clinic journal of medicine, 77(3), 560-567.
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