Volume 11, Number 2
Motor Phenomena of Seizures Hiroshi Shibasaki, M.D., D.M.S.
Although epileptic seizures can be classified into many types with respect to clinical as well as electrophysiologic features, most of them are associated with motor phenomena of some type. Furthermore, all simple or complex partial seizures without motor manifestations may evolve to secmotor ondarily generalized convulsions.'-"Thus, phenomena are the most common clinical manifestation of seizure disorders. For the purpose of this review, motor phenomena of epileptic seizures, were classified as listed in Table 1 by modifying the 1981 seizure classification proposed by the dommission on Classification and Terminology of the -, International League Against Epilepsy.' A special focus will be placed on myoclonus in relation to epilepsy.
PARTIAL (FOCAL) MOTOR SEIZURES This to the simp1e partial seizures with motor signs of the 1981 Classification. It is the most common form of simple partial seizure^.^ Each subtype of this group is believed
to originate from an epileptic source in a specific cortical area, and thus the location of the seizure As- ~ just focus determines the motor p h e n ~ m e n a . ~ mentioned, any subtype of this group may secondarily give rise to generalized convulsions and may be associated with loss of consciousness if the epileptic discharge spreads to those structures closely related to consciousness. Electroencephalographic (EEG) expression seen
,.
Motor
of Epileptic Seizures
I. Partial seizures A. Focal motor seizure without march, including epilepsia partialis continua B. Focal motor seizure with march (jacksonian seizure) C. Epileptic nystagmus D. Versive seizure E. Postural seizure F. Phonatory seizure G. Benign childhood epilepsy . . with centrotemporal spikes 11. ~ u t o m a t k m s Ill. Generalized tonic, clonic, or tonic-clonic seizures Iv. Myoc~onus V. AtOnic seizures VI. Infantile spasm
Department of Brain Pathophysiology, Kyoto University School of Medicine, Kyoto, Japan Reprint requests: Dr. Shibasaki, Department of Brain Pathophysiology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto, 606 Japan Copyright 0 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
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June 1991
SEMINARS I N NEUROLOGY
FOCAL MOTOR SEIZURE WITHOUT MARCH
In this type of seizure, clonic, tonic, o r both forms of muscle contractions appear either concurrently o r in succession in a restricted portion of the body. Theoretically, any part of the body may be involved as a result of focal seizure activity, depending on the site of the seizure focus in the motor strip. Clinically, however, the distal portion of an extremity (hand o r foot) o r fBcial muscles are most commonly involved, probably because of the relatively large representation of those parts in the motor cortex o r a lower threshold for seizure activities in those cortical areas. Truncal musculature can also be involved as the site of onset, although much less commonly than the face, arm, o r leg.4.7 'The attack occurs either spontaneously o r when triggered by voluntary movement o r sensory stimulation of that part of the body. T h e attack usually occurs as a series of clonic muscle contractions, alone o r superimposed on a tonic cramp lasting a variable length of time. It
Polygraph
may be followed by localized paralysis in the involved portion lasting from minutes to hours (Todd's paralysis). At times when focal clonic muscle contractions occur in isolation, they are indistinguishable from epileptic myoclonus both clinically and electrophysiologically (see Myoclonus, later). T h e seizure focus may be either single o r multiple. When a partial motor seizure is continuous without march, it is called epilepsia partialis continua. -. I he seizure focus is usually found in the corresponding area of the contralateral motor strip. Even the truncal seizure has been reported to be associated with sharp wave and wave complexes localized at the contralateral centrovertex scalp, probably representing the precentral cortex.'
Epilepsia Partialis Continua (Kojewnikow's Syndrome) In this condition, prolonged, rhythmic, clonic muscle contractions occur, usually in the distal portion of an extremity, most commonly in a thumb. 'The muscle jerks continue for days o r weeks at a rate of 20 to 60 per minute. T h e EEG shows fbcal sharp waves at the contralateral central region in association with muscle jerks (Fig. 1). Occasional cases show no scalp-recorded EEG changes. Epilepsia partialis continua is always based on structural lesions involving the motor cortex o r a closely adjacent area.8
Jerk-locked Averaging
%,ipv
\ d L
20 msec
500 msec
-P--/~+%+L~~VW
84
+
EMG (Rt thenar)
Figure 1. EEG-EMG polygraph (left) and jerk-locked average (right) in a 53-year-old man with epilepsia partialis continua of the right hand. Although there is no detectable spike on the EEG in association with rhythmic clonic muscle contraction, the jerk was shown by jerk-locked averaging to be preceded by a small negative potential (arrow) in the left central region.
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in this type of seizures during the interictal stage consists of localized contralateral discharge such as spike, sharp wave, o r spike and wave complex at the corresponding area. During the seizure, the EEG shows localized contralateral discharge, most commonly rhythmic, low-voltage, 16 to 30 Hz rapid potentials, starting over the corresponding area of cortical representation, although it may not always be detected on the scalp.',4,"
VOLUME 11, N U M B E R 2 JUNE 1991
M O T O R P H E N O M E N A O F SEIZURES-SHIRASAKI
Myoclonus of segmental spinal cord origin commonly occurs in a periodic fashion and may resemble epilepsia partialis continua, but can be distinguished from the latter by the involvement of a group of muscles innervated by a spinal segment and by the lack of EEG correlates even when studied by using the technique of jerk-locked back averaging.
cortex:' In most instances, forced turning is believed to be caused by an epileptic focus in the hemisphere opposite to the side toward which the eyes turn.12.'"uch seizures have often been called adversive, but aversive o r contraversive is a better descriptor. Ipsiversive movements may occur in association with a temporal focus.':'
FOCAL MOTOR SEIZURE WITH MARCH (JACKSONIAN SEIZURE)
In some focal motor seizures, the ictal signs spread slowly from one part of the body to another, usually following the homuncular pattern. T h e most typical pattern of spread is from a thumb to the other fingers, forearm, and arm as well as to the face, then to the leg of the same side, and finally to the opposite limbs. A generalized convulsion with loss of consciousness may then occur. T h e march is believed to be associated with the spread of epileptic discharge from one part of the motor strip to adjacent areas. Jacksonian seizure may also be followed by Todd's paralysis of the portion of the body where the march started. Painful tonic spasm, which is observed in patients with multiple sclerosis who have predominant involvement of the spinal cord, may resemble focal tonic motor seizure. 'The fbrmer shows a spread of muscle cramp in a distribution that cannot be explained by the march of a cortical seizure and is often preceded by and associated with severe pain spreading in the same distribution as the spasm." EPILEPTIC NYSTAGMUS
Jerky horizontal con-jugate nystagmus may occur as a manifestation of partial seizures. 'I'he epileptic discharge is usually detected in the posterior quadrant of the cerebral hemisphere opposite to the fast phase of the nystagmus,"' although an exception has been r e p ~ r t e d A . ~ prolonged episode of this condition has been reported as oculoclonic status epilepticus." A pendular form of epileptic nystagmus has also been reported." Epileptic nystagmus may be distinguished from true nystagmus by its paroxysmal occurrence as well as its EEG correlates and by the association of other symptoms in nystagmus of brainstem o r cerebellar origin. VERSNE SEIZURE
This seizure consists of turning the head and eyes to one side. Ictal versive movements have been associated with lesions in the supplementary motor area and in superior frontal, parietal, and occipital
Tonic posturing of limbs occurs as a main manifestation of seizures originating from the supplementary motor area.''' Among 1 1 patients reported by Morris et al'' (1988), it was bilateral in seven cases. Although versive seizures have been reported to be associated with midline o r parasagittal foci,'-' none of the cases reported by Morris et all4 showed adversive movements. Dystonic posturing has been reported as a manifestation of complex partial seizures of temporal lobe origin.'"he posturing occurred contralaterally with respect to the ictal discharge.'" Paroxysmal kinesigenic choreoathetosis is a familial disorder of autosomal dominant inheritance, manifested by paroxysms of choreoathetosis and dystonic movements induced by physical exercise such as jumping and running." T h e attack is not accompanied by loss of consciousness o r EEG abnormality, but antiepileptic agents such as carbamazepine are very effective.In PHONATORY SEIZURE
Ictal vocalization o r speech arrest can occur as a manifestation of seizures. Occasionally, an invol~ ~ r l t a rrepetition y of a syllable o r phrase may be seen (epileptic palilalia).' Prolonged seizure disorders may present as epileptic aphasia and must be distinguished from a transient ischemic attack by EEG.'"*() T h e seizure may originate from the rolandic, prerolandic, o r temporal cortex o r from the temporoparieto-occipital j ~ n c t i o n . ~ BENIGN CHILDHOOD EPILEPSY WITH CENTROTEMPORAL SPIKES
This is a syndrome of brief, simple partial, hemifacial motor seizures, frequently with associated somatosensory symptoms. T h e partial seizures have a tendency to evolve into generalized tonic-clonic seizures. T h e syndrome is characteristically seen in children between ages 3 and 16 years and commonly occurs during sleep.*' T h e interictal EEG has blunt high-voltage centrotemporal (rolandic) spikes." A patient with this condition who also had prolonged intermittent episodes of drooling and oromotor dyspraxia was recently reported.'"
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POSTURAL SEIZURE
SEMINARS I N NEUROLOGY
(focal) seizure discharge occurring in some cortical area.
This is the most common form of complex partial seizures in the adult population and is characterized by more or less coordinated adapted inMYOCLONUS voluntary motor activity occurring during the state of clouding of consciousness. T h e motor activity is Myoclonus is defined as sudden, jerky, irregusually commonplace in nature, such as chewing and swallowing (eating automatisms), drinking,24 ular contractions of a muscle or group of muscles mimicry (for example, expression of fear), crying unassociated with loss of consciousness."4 Myo(dacrystic epilepsy)," laughing (ictal laughter, ge- clonic jerks are often epileptic in nature, that is, lastic epilepsy),"gesture, repetitive hand move- they are generated by the same mechanism as parments (for example, tapping, picking, and fum- tial motor seizures and can evolve to generalized Hence, they are classified as "epileptic ~~ bling), ambulation or wandering ( p ~ r i o m a n i a ) , ' ~ ,convulsions. vocalization (verbal automatism), kicking and thrash- myoclonus.""" Epileptic myoclonus often occurs in the face ing, and sexual behavior (sexual automatism)."' Although responsible cerebral structures for autom- and limbs. T h e jerks are usually of the postural or atisms may be variable, the seizure discharge seems intention (action) type, or both, and are rarely seer1 commonly to involve various areas of the limbic at complete rest or during sleep. Jerks are prosystem, especially temporal and frontal lobes.29 voked as soon as the patient initiates any kind of Among others, ictal laughter has been reported in volitional movement, including speech. If the jerks a patient with a tumor of the floor of the third are recorded by surface electromyogram (EMG), ventricle"" and in patients with hypothalamic ha- the associated discharge of each muscle jerk is abrupt and very brief, usually lasting less than 30 mar to ma^.^' msec. Moreover, epileptic myoclonus is commonly stimulus-sensitive. T h e most effective stimuli are GENERALIZED TONIC, CLONIC, OR TONIC- tactile or proprioceptive stimuli, such as tendon tap CLONIC SEIZURES or passive joint movement, and in some cases auditory or flash stimuli are also effective. A myoGeneralized tonic-clonic (grand mal) seizures clonic jerk elicited by tendon tap may sometimes may occur with (secondary generalized) or without appear indistinguishable from an enhanced deep (primary generalized) focal onset. Onset is sudden, tendon reflex, but in contrast to the monosynaptic with loss of consciousness and abrupt tonic con- spinal reflex, the myoclonic response, especially traction of muscles, frequently associated with stri- that of cortical origin, spreads to involve other dor, cry, or moan, followed by falling to the muscles of the corresponding extremity and those ground." While the afflicted person is lying rigid of other extremities at diff-erent latencies. Myo(usually less than 1 minute), cyanosis and urinary clonic jerks occurring in association with volitional incontinence may occur. T h e tonic stage is fol- movement of limbs are usually irregular and asynlowed by clonic convulsive movements lasting for a chronous, although they may occasionally look variable length of time (usually 1 to 3 minutes). symmetrical. A myoclonic response following an Forced contraction of the masticatory muscles may unexpected auditory stimulus, however, may inresult in bites on the lateral aspects of the tongue. volve both sides synchronously and truncal musHypersalivation and hyperventilation may cause culature as well. A vigorous jerk involving the trunfrothing at the mouth. T h e attack is commonly fol- cal and leg muscles, as occurs upon starting to walk, may cause a sudden drop attack. lowed by deep sleep. T h e interictal EEG usually shows diffuse 4 to Epileptic myoclonus is not disease specific at 6 Hz multiple-spike and wave complexes or diffuse all. It is a cardinal symptom of "progressive myo3 Hz spike and wave complexes.' During the sei- clonic epilepsy," which includes Lafora's disease, zure, diffuse 14 to 24 Hz multiple spikes or recruit- various forms of lipidosis, neuronal ceroid lipofusing patterns of 9 to 12 Hz diffuse rhythms may cinosis, myoclonic epilepsy associated with mitoprecede the tonic phase.6 In association with dif- chondrial m y ~ p a t h y dentatorubropallidoluysian ,~~ fuse rhythmic 9 to 15 Hz EEG discharges, irregular atrophy, juvenile neuroaxonal dystrophy, Unverfluttering or twitching movements of eyelids occur richt-Lundborg syndrome, and dyssynergia cereas a manifestation of generalized epilepsy.33 It is bellaris myoclonica (Ramsay Hunt syndrome).37 possible that the majority of generalized tonic- Epileptic myoclonus may also be seen in other conclonic seizures may result secondarily from partial ditions such as postanoxic myoclonus (Lance-Ad-
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AUTOMATISMS
V O L U M E 1 I , NUMBER 2 JUNE 1991
M O T O R P H E N O M E N A OF SEIZURES-SHIBASAKI
EEG-EMG Polygraph Polygraphic recording of multichannel EEGs and surface EMGs is essential to study any kind of myoclonus.'" First, the duration of EMG discharge associated with epileptic myoclonus is very short. I n the majority of rnyoclonus, whether epileptic or nonepileptic, various parts of the body and face are involved independently and asynchronously, but in epileptic myoclonus, agonist and antagonist muscles usually contract simultaneously. T h e EEG commonly shows multiple spikes or spike and wave complexes in patients with epileptic myoclonus, although there are exceptions. However, the conventional EEG-EMG polygraph may not reveal EEG spikes in association with myoclonic EMG discharges, even if the myoclonus is of cortical origin. Furthermore, when myoclonic jerks are associated with EEG spikes, it is often difficult to study the relationship between the two phenomena.
Jerk-Locked Back Averaging Epileptic myoclonus of cortical origin is preceded by an epileptic discharge generated in the motor cortex, but the latter may not be detectable on the scalp EEG. If that is the case, the EEG may be back averaged by using the onset of the simultaneously recorded EMG discharge as a trigger so that an EEG activity directly related to the myocloBy applying the technus can be dernon~trated.'~~"" nique of jerk-locked back averaging, the myoclonus-related cortical spike may be detected even though the conventional polygraph fails to reveal any related spike, and, furthermore, the temporal as well as spatial relationship between the myoclonus and the EEG discharge can be easily studied. However, the failure to demonstrate any myoclonus-related EEG spike by jerk-locked back averaging does not always mean the subcortical origin of that myoclonus. T h e EEG spike may be just too small to be picked up by the scalp electrodes, even by averaging. Myoclonus of subcortical origin is not preceded by any cortical discharge. Most patients with
epileptic myoclonus have cortical myoclonus, although they may also have myoclonus of subcortical origin. Periodic myoclonus frequently observed in patients with Creutzfeldt-Jakob disease may or may not be associated with the periodic synchronous EEG discharge (PSD). When both periodic myoclonus and PSD are seen on an EEG-EMG polygraph, jerk-locked back averaging with respect to the myoclonus does show some relationship between those two periodic phenomena, but the temporal relationship between the two is not con~ t a n t . ~'The " same holds true for periodic slow movement occurring in approximate synchrony with periodic EEG complexes in patients with subacute sclerosing panencephalitis. These periodic myoclonias are not epileptic in nature, although, at the advanced stage of Creutzfeldt-Jakob disease, when PSD becomes less conspicuous and multifocal spike discharges are seen on EEG, patients may develop epileptic myoclonus with stimulus sensitivity.
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ams syndrome), Alzheimer's disease, at a certain stage of Ch-eutzfeldt-Jakob disease, and metabolic encephalopathy (uremic encephalopathy, among ~thers).:'~ Electrophysiologically, epileptic myoclonus can be distinguished from nonepileptic myoclonus by employing various techniques as follow^.^'"
Cerebral Evoked Potentials Epileptic myoclonus is frequently stimulussensitive, although some subcortical myoclonus, such as myoclonus of brainstem origin and spinal myoclonus, may also be stimulus-sensitive and yet nonepileptic. Electrophysiologically, stimulus-sensitivity can be studied by applying various kinds of cerebral evoked potentials. In most patients with cortical reflex myoclonus, which is usually epileptic, the early cortical components of the somatosensory evoked potentials (SEP) following electric stimulation of the peripheral nerve are extremely large. Also, giant SEPs are followed by an enhanced EMG response of the stimulated part with a latency of 40 to 45 msec in the case of the hand; this is called the C reflex and corresponds to the . ~ a' typical cortical rereflex myoclonus i t ~ e l f . ~ 'In flex myoclonus, the reflex myoclonus spreads from the proximal to the distal muscles of the stimulated extremity (Fig. 2) and involves the opposite hand approximately 10 msec later (Fig. 3).43 In reticuIar reflex myo~lonus,"~ which has also been reported to be epileptic, the cortical SEP is not enlarged. This reflex myoclonus has been reported to start characteristically from the muscles innervated by the medullary motor nuclei and then to spread rostrally as well as caudaIly. In patients with pure brainstem reflex myoclonus, such as reported in a patient with extensive midbrain lesions causing a decerebrate state, symmetrical myoclonic jerks are elicited by somatosensory as well as by auditory stimuli, with variable latencies.44 87
SEMINARS IN NEUROLOGY
Electric Stim. (LMN) (n=64)
VOLUME 11, NUMBER 2 JUNE 1991
Jerk-locked Average (n=32)
Av. EMG L thenar
L wrist ext. .,! .;..
e' \ 100 ms
80 ms
Figure 2. Spread of reflex myoclonus induced in the left upper limb by electric stimulation of the left median nerve (left) and of spontaneous myoclonus occurring in the left upper limb in a 22-year-old man with progressive myoclonic epilepsy (right). Note the quite similar spread of both types of muscle jerk from proximal to distal muscles.
Jerk-Locked Evoked Potentials In cortical reflex myoclonus, cortical excitability immediately following a spontaneous myoclonus or reflex myoclonus can be abnormal, usually pathologically enhanced. This state can be studied by combining jerk-locked back averaging and evoked potentials. Cerebral evoked potentials anti EMG are averaged with respect to the stimuli, which are presented at defined intervals after the spontaneous myoclonu~.~~.*"
Av. EEG C3-A 1 C1-A1
ATONIC SEIZURES
k
i
Av. Rect. EMG
I
+
I
I
Stirn. (n=50)
.*Iex
I
I
I
I
I
I
20rnsec/div.
Figure 3. Occurrence of evoked myoclonus in the right hand (C') 10 msec after myoclonus was evoked (C reflex) in the left hand by electric stimulation of the left median nerve at the wrist in a 15-year-old girl with progressive myoclonic epilepsy. Cortical somatosensory evoked potentials (P25 and N33) are extremely enhanced.
T h e atonic seizure is characterized by a sudden diminution in muscle tone, leading to a head drop with slackening of the jaw and the dropping of a limb. Loss of all muscle tone leads to a slumping to the ground: drop attacks.I T h e seizure may be associated with a very brief loss of consciousness. T h e interictal EEG shows polyspikes and wave, flattening, or low-voltage fast activity, anti the ictal EEG shows polyspikes and slow wave complexes.' An atonic seizure may be the consequence of an extremely brief generalized myoclonic jerk. In this regard, a certain type of so-called negative myoclonus of the limbs, which is associated with sudden brief cessation of ongoing EMG activity and yet is preceded by an EEG spike," may be called a partial atonic seizure. Drop attacks can occur in combination with various forms of partial epilepsy.47 Drop attacks may also be seen in conditions other than epilepsy, such as brainstem ischemia secondary to circula-
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L biceps
tory insufficiency of the basilar artery territory, or cataplexy in narcoleptic patients.
INFANTILE SPASM
'This form of seizure starts between 3 and 12 months of age, and is seen in children up to 3 or 4 years old. The typical infantile spasm consists of an abrupt flexion of the neck and trunk, with the arms flung outward and forward, and is called a "salaam" or "jackknife" seizure.lHIt is well known to be associated with hypsarrhythmia on the EEG during the interictal period. T h e ictal EEG during infantile spasms is variable, with paroxysmal suppression of the background activity (the electrodecremental response) as the most common pattern, although polyspikes and slow waves and rhythmic fast activity may also be seen.4g REFERENCES 1. T h e Commission on
Motor Phenomena of Seizures Hiroshi Shibasaki, M.D., D.M.S.
Although epileptic seizures can be classified into many types with respect to clinical as well as electrophysiologic features, most of them are associated with motor phenomena of some type. Furthermore, all simple or complex partial seizures without motor manifestations may evolve to secmotor ondarily generalized convulsions.'-"Thus, phenomena are the most common clinical manifestation of seizure disorders. For the purpose of this review, motor phenomena of epileptic seizures, were classified as listed in Table 1 by modifying the 1981 seizure classification proposed by the dommission on Classification and Terminology of the -, International League Against Epilepsy.' A special focus will be placed on myoclonus in relation to epilepsy.
PARTIAL (FOCAL) MOTOR SEIZURES This to the simp1e partial seizures with motor signs of the 1981 Classification. It is the most common form of simple partial seizure^.^ Each subtype of this group is believed
to originate from an epileptic source in a specific cortical area, and thus the location of the seizure As- ~ just focus determines the motor p h e n ~ m e n a . ~ mentioned, any subtype of this group may secondarily give rise to generalized convulsions and may be associated with loss of consciousness if the epileptic discharge spreads to those structures closely related to consciousness. Electroencephalographic (EEG) expression seen
,.
Motor
of Epileptic Seizures
I. Partial seizures A. Focal motor seizure without march, including epilepsia partialis continua B. Focal motor seizure with march (jacksonian seizure) C. Epileptic nystagmus D. Versive seizure E. Postural seizure F. Phonatory seizure G. Benign childhood epilepsy . . with centrotemporal spikes 11. ~ u t o m a t k m s Ill. Generalized tonic, clonic, or tonic-clonic seizures Iv. Myoc~onus V. AtOnic seizures VI. Infantile spasm
Department of Brain Pathophysiology, Kyoto University School of Medicine, Kyoto, Japan Reprint requests: Dr. Shibasaki, Department of Brain Pathophysiology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto, 606 Japan Copyright 0 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
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June 1991
SEMINARS I N NEUROLOGY
FOCAL MOTOR SEIZURE WITHOUT MARCH
In this type of seizure, clonic, tonic, o r both forms of muscle contractions appear either concurrently o r in succession in a restricted portion of the body. Theoretically, any part of the body may be involved as a result of focal seizure activity, depending on the site of the seizure focus in the motor strip. Clinically, however, the distal portion of an extremity (hand o r foot) o r fBcial muscles are most commonly involved, probably because of the relatively large representation of those parts in the motor cortex o r a lower threshold for seizure activities in those cortical areas. Truncal musculature can also be involved as the site of onset, although much less commonly than the face, arm, o r leg.4.7 'The attack occurs either spontaneously o r when triggered by voluntary movement o r sensory stimulation of that part of the body. T h e attack usually occurs as a series of clonic muscle contractions, alone o r superimposed on a tonic cramp lasting a variable length of time. It
Polygraph
may be followed by localized paralysis in the involved portion lasting from minutes to hours (Todd's paralysis). At times when focal clonic muscle contractions occur in isolation, they are indistinguishable from epileptic myoclonus both clinically and electrophysiologically (see Myoclonus, later). T h e seizure focus may be either single o r multiple. When a partial motor seizure is continuous without march, it is called epilepsia partialis continua. -. I he seizure focus is usually found in the corresponding area of the contralateral motor strip. Even the truncal seizure has been reported to be associated with sharp wave and wave complexes localized at the contralateral centrovertex scalp, probably representing the precentral cortex.'
Epilepsia Partialis Continua (Kojewnikow's Syndrome) In this condition, prolonged, rhythmic, clonic muscle contractions occur, usually in the distal portion of an extremity, most commonly in a thumb. 'The muscle jerks continue for days o r weeks at a rate of 20 to 60 per minute. T h e EEG shows fbcal sharp waves at the contralateral central region in association with muscle jerks (Fig. 1). Occasional cases show no scalp-recorded EEG changes. Epilepsia partialis continua is always based on structural lesions involving the motor cortex o r a closely adjacent area.8
Jerk-locked Averaging
%,ipv
\ d L
20 msec
500 msec
-P--/~+%+L~~VW
84
+
EMG (Rt thenar)
Figure 1. EEG-EMG polygraph (left) and jerk-locked average (right) in a 53-year-old man with epilepsia partialis continua of the right hand. Although there is no detectable spike on the EEG in association with rhythmic clonic muscle contraction, the jerk was shown by jerk-locked averaging to be preceded by a small negative potential (arrow) in the left central region.
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in this type of seizures during the interictal stage consists of localized contralateral discharge such as spike, sharp wave, o r spike and wave complex at the corresponding area. During the seizure, the EEG shows localized contralateral discharge, most commonly rhythmic, low-voltage, 16 to 30 Hz rapid potentials, starting over the corresponding area of cortical representation, although it may not always be detected on the scalp.',4,"
VOLUME 11, N U M B E R 2 JUNE 1991
M O T O R P H E N O M E N A O F SEIZURES-SHIRASAKI
Myoclonus of segmental spinal cord origin commonly occurs in a periodic fashion and may resemble epilepsia partialis continua, but can be distinguished from the latter by the involvement of a group of muscles innervated by a spinal segment and by the lack of EEG correlates even when studied by using the technique of jerk-locked back averaging.
cortex:' In most instances, forced turning is believed to be caused by an epileptic focus in the hemisphere opposite to the side toward which the eyes turn.12.'"uch seizures have often been called adversive, but aversive o r contraversive is a better descriptor. Ipsiversive movements may occur in association with a temporal focus.':'
FOCAL MOTOR SEIZURE WITH MARCH (JACKSONIAN SEIZURE)
In some focal motor seizures, the ictal signs spread slowly from one part of the body to another, usually following the homuncular pattern. T h e most typical pattern of spread is from a thumb to the other fingers, forearm, and arm as well as to the face, then to the leg of the same side, and finally to the opposite limbs. A generalized convulsion with loss of consciousness may then occur. T h e march is believed to be associated with the spread of epileptic discharge from one part of the motor strip to adjacent areas. Jacksonian seizure may also be followed by Todd's paralysis of the portion of the body where the march started. Painful tonic spasm, which is observed in patients with multiple sclerosis who have predominant involvement of the spinal cord, may resemble focal tonic motor seizure. 'The fbrmer shows a spread of muscle cramp in a distribution that cannot be explained by the march of a cortical seizure and is often preceded by and associated with severe pain spreading in the same distribution as the spasm." EPILEPTIC NYSTAGMUS
Jerky horizontal con-jugate nystagmus may occur as a manifestation of partial seizures. 'I'he epileptic discharge is usually detected in the posterior quadrant of the cerebral hemisphere opposite to the fast phase of the nystagmus,"' although an exception has been r e p ~ r t e d A . ~ prolonged episode of this condition has been reported as oculoclonic status epilepticus." A pendular form of epileptic nystagmus has also been reported." Epileptic nystagmus may be distinguished from true nystagmus by its paroxysmal occurrence as well as its EEG correlates and by the association of other symptoms in nystagmus of brainstem o r cerebellar origin. VERSNE SEIZURE
This seizure consists of turning the head and eyes to one side. Ictal versive movements have been associated with lesions in the supplementary motor area and in superior frontal, parietal, and occipital
Tonic posturing of limbs occurs as a main manifestation of seizures originating from the supplementary motor area.''' Among 1 1 patients reported by Morris et al'' (1988), it was bilateral in seven cases. Although versive seizures have been reported to be associated with midline o r parasagittal foci,'-' none of the cases reported by Morris et all4 showed adversive movements. Dystonic posturing has been reported as a manifestation of complex partial seizures of temporal lobe origin.'"he posturing occurred contralaterally with respect to the ictal discharge.'" Paroxysmal kinesigenic choreoathetosis is a familial disorder of autosomal dominant inheritance, manifested by paroxysms of choreoathetosis and dystonic movements induced by physical exercise such as jumping and running." T h e attack is not accompanied by loss of consciousness o r EEG abnormality, but antiepileptic agents such as carbamazepine are very effective.In PHONATORY SEIZURE
Ictal vocalization o r speech arrest can occur as a manifestation of seizures. Occasionally, an invol~ ~ r l t a rrepetition y of a syllable o r phrase may be seen (epileptic palilalia).' Prolonged seizure disorders may present as epileptic aphasia and must be distinguished from a transient ischemic attack by EEG.'"*() T h e seizure may originate from the rolandic, prerolandic, o r temporal cortex o r from the temporoparieto-occipital j ~ n c t i o n . ~ BENIGN CHILDHOOD EPILEPSY WITH CENTROTEMPORAL SPIKES
This is a syndrome of brief, simple partial, hemifacial motor seizures, frequently with associated somatosensory symptoms. T h e partial seizures have a tendency to evolve into generalized tonic-clonic seizures. T h e syndrome is characteristically seen in children between ages 3 and 16 years and commonly occurs during sleep.*' T h e interictal EEG has blunt high-voltage centrotemporal (rolandic) spikes." A patient with this condition who also had prolonged intermittent episodes of drooling and oromotor dyspraxia was recently reported.'"
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POSTURAL SEIZURE
SEMINARS I N NEUROLOGY
(focal) seizure discharge occurring in some cortical area.
This is the most common form of complex partial seizures in the adult population and is characterized by more or less coordinated adapted inMYOCLONUS voluntary motor activity occurring during the state of clouding of consciousness. T h e motor activity is Myoclonus is defined as sudden, jerky, irregusually commonplace in nature, such as chewing and swallowing (eating automatisms), drinking,24 ular contractions of a muscle or group of muscles mimicry (for example, expression of fear), crying unassociated with loss of consciousness."4 Myo(dacrystic epilepsy)," laughing (ictal laughter, ge- clonic jerks are often epileptic in nature, that is, lastic epilepsy),"gesture, repetitive hand move- they are generated by the same mechanism as parments (for example, tapping, picking, and fum- tial motor seizures and can evolve to generalized Hence, they are classified as "epileptic ~~ bling), ambulation or wandering ( p ~ r i o m a n i a ) , ' ~ ,convulsions. vocalization (verbal automatism), kicking and thrash- myoclonus.""" Epileptic myoclonus often occurs in the face ing, and sexual behavior (sexual automatism)."' Although responsible cerebral structures for autom- and limbs. T h e jerks are usually of the postural or atisms may be variable, the seizure discharge seems intention (action) type, or both, and are rarely seer1 commonly to involve various areas of the limbic at complete rest or during sleep. Jerks are prosystem, especially temporal and frontal lobes.29 voked as soon as the patient initiates any kind of Among others, ictal laughter has been reported in volitional movement, including speech. If the jerks a patient with a tumor of the floor of the third are recorded by surface electromyogram (EMG), ventricle"" and in patients with hypothalamic ha- the associated discharge of each muscle jerk is abrupt and very brief, usually lasting less than 30 mar to ma^.^' msec. Moreover, epileptic myoclonus is commonly stimulus-sensitive. T h e most effective stimuli are GENERALIZED TONIC, CLONIC, OR TONIC- tactile or proprioceptive stimuli, such as tendon tap CLONIC SEIZURES or passive joint movement, and in some cases auditory or flash stimuli are also effective. A myoGeneralized tonic-clonic (grand mal) seizures clonic jerk elicited by tendon tap may sometimes may occur with (secondary generalized) or without appear indistinguishable from an enhanced deep (primary generalized) focal onset. Onset is sudden, tendon reflex, but in contrast to the monosynaptic with loss of consciousness and abrupt tonic con- spinal reflex, the myoclonic response, especially traction of muscles, frequently associated with stri- that of cortical origin, spreads to involve other dor, cry, or moan, followed by falling to the muscles of the corresponding extremity and those ground." While the afflicted person is lying rigid of other extremities at diff-erent latencies. Myo(usually less than 1 minute), cyanosis and urinary clonic jerks occurring in association with volitional incontinence may occur. T h e tonic stage is fol- movement of limbs are usually irregular and asynlowed by clonic convulsive movements lasting for a chronous, although they may occasionally look variable length of time (usually 1 to 3 minutes). symmetrical. A myoclonic response following an Forced contraction of the masticatory muscles may unexpected auditory stimulus, however, may inresult in bites on the lateral aspects of the tongue. volve both sides synchronously and truncal musHypersalivation and hyperventilation may cause culature as well. A vigorous jerk involving the trunfrothing at the mouth. T h e attack is commonly fol- cal and leg muscles, as occurs upon starting to walk, may cause a sudden drop attack. lowed by deep sleep. T h e interictal EEG usually shows diffuse 4 to Epileptic myoclonus is not disease specific at 6 Hz multiple-spike and wave complexes or diffuse all. It is a cardinal symptom of "progressive myo3 Hz spike and wave complexes.' During the sei- clonic epilepsy," which includes Lafora's disease, zure, diffuse 14 to 24 Hz multiple spikes or recruit- various forms of lipidosis, neuronal ceroid lipofusing patterns of 9 to 12 Hz diffuse rhythms may cinosis, myoclonic epilepsy associated with mitoprecede the tonic phase.6 In association with dif- chondrial m y ~ p a t h y dentatorubropallidoluysian ,~~ fuse rhythmic 9 to 15 Hz EEG discharges, irregular atrophy, juvenile neuroaxonal dystrophy, Unverfluttering or twitching movements of eyelids occur richt-Lundborg syndrome, and dyssynergia cereas a manifestation of generalized epilepsy.33 It is bellaris myoclonica (Ramsay Hunt syndrome).37 possible that the majority of generalized tonic- Epileptic myoclonus may also be seen in other conclonic seizures may result secondarily from partial ditions such as postanoxic myoclonus (Lance-Ad-
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AUTOMATISMS
V O L U M E 1 I , NUMBER 2 JUNE 1991
M O T O R P H E N O M E N A OF SEIZURES-SHIBASAKI
EEG-EMG Polygraph Polygraphic recording of multichannel EEGs and surface EMGs is essential to study any kind of myoclonus.'" First, the duration of EMG discharge associated with epileptic myoclonus is very short. I n the majority of rnyoclonus, whether epileptic or nonepileptic, various parts of the body and face are involved independently and asynchronously, but in epileptic myoclonus, agonist and antagonist muscles usually contract simultaneously. T h e EEG commonly shows multiple spikes or spike and wave complexes in patients with epileptic myoclonus, although there are exceptions. However, the conventional EEG-EMG polygraph may not reveal EEG spikes in association with myoclonic EMG discharges, even if the myoclonus is of cortical origin. Furthermore, when myoclonic jerks are associated with EEG spikes, it is often difficult to study the relationship between the two phenomena.
Jerk-Locked Back Averaging Epileptic myoclonus of cortical origin is preceded by an epileptic discharge generated in the motor cortex, but the latter may not be detectable on the scalp EEG. If that is the case, the EEG may be back averaged by using the onset of the simultaneously recorded EMG discharge as a trigger so that an EEG activity directly related to the myocloBy applying the technus can be dernon~trated.'~~"" nique of jerk-locked back averaging, the myoclonus-related cortical spike may be detected even though the conventional polygraph fails to reveal any related spike, and, furthermore, the temporal as well as spatial relationship between the myoclonus and the EEG discharge can be easily studied. However, the failure to demonstrate any myoclonus-related EEG spike by jerk-locked back averaging does not always mean the subcortical origin of that myoclonus. T h e EEG spike may be just too small to be picked up by the scalp electrodes, even by averaging. Myoclonus of subcortical origin is not preceded by any cortical discharge. Most patients with
epileptic myoclonus have cortical myoclonus, although they may also have myoclonus of subcortical origin. Periodic myoclonus frequently observed in patients with Creutzfeldt-Jakob disease may or may not be associated with the periodic synchronous EEG discharge (PSD). When both periodic myoclonus and PSD are seen on an EEG-EMG polygraph, jerk-locked back averaging with respect to the myoclonus does show some relationship between those two periodic phenomena, but the temporal relationship between the two is not con~ t a n t . ~'The " same holds true for periodic slow movement occurring in approximate synchrony with periodic EEG complexes in patients with subacute sclerosing panencephalitis. These periodic myoclonias are not epileptic in nature, although, at the advanced stage of Creutzfeldt-Jakob disease, when PSD becomes less conspicuous and multifocal spike discharges are seen on EEG, patients may develop epileptic myoclonus with stimulus sensitivity.
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ams syndrome), Alzheimer's disease, at a certain stage of Ch-eutzfeldt-Jakob disease, and metabolic encephalopathy (uremic encephalopathy, among ~thers).:'~ Electrophysiologically, epileptic myoclonus can be distinguished from nonepileptic myoclonus by employing various techniques as follow^.^'"
Cerebral Evoked Potentials Epileptic myoclonus is frequently stimulussensitive, although some subcortical myoclonus, such as myoclonus of brainstem origin and spinal myoclonus, may also be stimulus-sensitive and yet nonepileptic. Electrophysiologically, stimulus-sensitivity can be studied by applying various kinds of cerebral evoked potentials. In most patients with cortical reflex myoclonus, which is usually epileptic, the early cortical components of the somatosensory evoked potentials (SEP) following electric stimulation of the peripheral nerve are extremely large. Also, giant SEPs are followed by an enhanced EMG response of the stimulated part with a latency of 40 to 45 msec in the case of the hand; this is called the C reflex and corresponds to the . ~ a' typical cortical rereflex myoclonus i t ~ e l f . ~ 'In flex myoclonus, the reflex myoclonus spreads from the proximal to the distal muscles of the stimulated extremity (Fig. 2) and involves the opposite hand approximately 10 msec later (Fig. 3).43 In reticuIar reflex myo~lonus,"~ which has also been reported to be epileptic, the cortical SEP is not enlarged. This reflex myoclonus has been reported to start characteristically from the muscles innervated by the medullary motor nuclei and then to spread rostrally as well as caudaIly. In patients with pure brainstem reflex myoclonus, such as reported in a patient with extensive midbrain lesions causing a decerebrate state, symmetrical myoclonic jerks are elicited by somatosensory as well as by auditory stimuli, with variable latencies.44 87
SEMINARS IN NEUROLOGY
Electric Stim. (LMN) (n=64)
VOLUME 11, NUMBER 2 JUNE 1991
Jerk-locked Average (n=32)
Av. EMG L thenar
L wrist ext. .,! .;..
e' \ 100 ms
80 ms
Figure 2. Spread of reflex myoclonus induced in the left upper limb by electric stimulation of the left median nerve (left) and of spontaneous myoclonus occurring in the left upper limb in a 22-year-old man with progressive myoclonic epilepsy (right). Note the quite similar spread of both types of muscle jerk from proximal to distal muscles.
Jerk-Locked Evoked Potentials In cortical reflex myoclonus, cortical excitability immediately following a spontaneous myoclonus or reflex myoclonus can be abnormal, usually pathologically enhanced. This state can be studied by combining jerk-locked back averaging and evoked potentials. Cerebral evoked potentials anti EMG are averaged with respect to the stimuli, which are presented at defined intervals after the spontaneous myoclonu~.~~.*"
Av. EEG C3-A 1 C1-A1
ATONIC SEIZURES
k
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Av. Rect. EMG
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Stirn. (n=50)
.*Iex
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Figure 3. Occurrence of evoked myoclonus in the right hand (C') 10 msec after myoclonus was evoked (C reflex) in the left hand by electric stimulation of the left median nerve at the wrist in a 15-year-old girl with progressive myoclonic epilepsy. Cortical somatosensory evoked potentials (P25 and N33) are extremely enhanced.
T h e atonic seizure is characterized by a sudden diminution in muscle tone, leading to a head drop with slackening of the jaw and the dropping of a limb. Loss of all muscle tone leads to a slumping to the ground: drop attacks.I T h e seizure may be associated with a very brief loss of consciousness. T h e interictal EEG shows polyspikes and wave, flattening, or low-voltage fast activity, anti the ictal EEG shows polyspikes and slow wave complexes.' An atonic seizure may be the consequence of an extremely brief generalized myoclonic jerk. In this regard, a certain type of so-called negative myoclonus of the limbs, which is associated with sudden brief cessation of ongoing EMG activity and yet is preceded by an EEG spike," may be called a partial atonic seizure. Drop attacks can occur in combination with various forms of partial epilepsy.47 Drop attacks may also be seen in conditions other than epilepsy, such as brainstem ischemia secondary to circula-
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L biceps
tory insufficiency of the basilar artery territory, or cataplexy in narcoleptic patients.
INFANTILE SPASM
'This form of seizure starts between 3 and 12 months of age, and is seen in children up to 3 or 4 years old. The typical infantile spasm consists of an abrupt flexion of the neck and trunk, with the arms flung outward and forward, and is called a "salaam" or "jackknife" seizure.lHIt is well known to be associated with hypsarrhythmia on the EEG during the interictal period. T h e ictal EEG during infantile spasms is variable, with paroxysmal suppression of the background activity (the electrodecremental response) as the most common pattern, although polyspikes and slow waves and rhythmic fast activity may also be seen.4g REFERENCES 1. T h e Commission on
