Clonic activity is further described as being without a march if it remains confined to the same body part from beginning to end. Clonic activity refers to a regularly repetitive jerking that is prolonged. Negative myoclonus would not be visible if the affected body part were resting. Negative myoclonus may produce a jerk-like motion in association with a transitory loss of posture of that body part. Negative myoclonus refers to an interruption of tonic muscle activity for less than 500 ms without prior positive contraction. This can affect any distal or proximal body part and may also be generalized. A myoclonic jerk or myoclonus refers to a very brief involuntary contraction usually lasting less than 100 ms. Dystonic posturing is a sustained contraction that results in an abnormal posture with a rotating or twisting motion ( Fig. This may be associated with a truncal rotation. Versive manifestation indicates a sustained or forced deviation of the eyes or the head to one side ( Fig. This will usually involve contraction of more than one muscle. Postural manifestation suggests tonic activity that results in a posture. Tonic activity includes epileptic spasms that are a sudden flexion and/or extension which is more sustained than a myoclonic jerk but yet very short in duration, affecting predominantly proximal or truncal muscles. Elementary motor manifestations include tonic, which means a sustained increase in muscle contraction lasting up to minutes. Elementary motor refers to the contraction of a muscle or group of muscles that is usually stereotyped and does not include multiple phases. Several qualifiers for motor manifestation exist.

The term positive motor can be used to specifically indicate an increase in muscle contraction. A motor manifestation can also be negative, associated with a decrease in muscle contraction. Motor manifestations refer to involvement of the musculature, usually with an increase in muscle contraction that produces a movement. The term ictal semiology means the signs and symptoms associated with seizures. Whenever possible, the definition is derived from the glossary of descriptive terminology for ictal semiology, reported by the ILAE task force on classification and terminology ( Blume et al., 2001). The terms frequently used in the description of seizures follow.

Joseph Jankovic MD, in Bradley and Daroff's Neurology in Clinical Practice, 2022 Glossary of Seizure Terminology and Other Definitions

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