Inhibitory Motor Status: Two N e w Cases and a Review
of Inhibitory Motor Seizures
Ross Fine Smith, Orrin Devinsky, and Daniel Luciano
Transient paralysis is an uncommon seizure symptom. We report two new
cases of inhibitory motor status and review 24 previously cases of inhibitory
seizures. Among the 22 adult patients, 14 (64%) had a frontoparietal lesion
(tumor, 7; stroke, 7); 5 (23%) had mesiotemporal sclerosis (MTS), and 3 (14%)
had no identified lesion. In contrast, all 4 pediatric patients had no identified
brain lesions. Inhibitory motor seizures were associated most commonly with
lesions in frontoparietal primary and supplementary motor-sensory area and,
less often, in the mesial temporal lobe. Inhibitory motor seizures arising from
frontoparietal foci are often more prolonged (>2-3 min) than those arising
from the mesial temporal area (<1.5 min). Patients with temporal lobe seizure
foci manifest ictal flaccidity of an extremity during a complex partial seizure
(CPS), which may represent motor neglect rather than ictal weakness since
strength cannot be accurately assessed when consciousness is impaired. Inhibitory motor seizures from sensorimotor cortex seizure foci are probably
more common than is recognized. Key Words: Seizures--Epilepsy-Inhibition. 9 1997 by Elsevier Science Inc. All rights reserved.
Inhibitory motor seizures are manifested as a
paroxysmal paralysis of the face, arm, leg, or hemib o d y and were first described by Gowers (1) as a
"paroxysmal appearing palsy of an epileptic origin." Consciousness typically is not impaired, and
full function of the paretic extremity returns. Inhibitory m o t o r seizures have been periodically described by a variety of terms, including nonconvulsive seizure paralysis (2), hemiparetic seizures (3),
Received February 1, 1996; accepted August 22, 1996.
From the Department of Neurology, New York University School of Medicine, Hospital for Joint Diseases,
New York, NY, U.S.A.
Address correspondence and reprint requests to Dr.
Orrin Devinsky at Department of Neurology, Hospital
for Joint Diseases, School of Medicine, 301 East 17th
Street, New York, NY 10003, U.S.A.
J. Epilepsy 1997;10:15-21
9 1997 by Elsevier Science Inc. All rights reserved.
655 Avenue of the Americas, New York, NY 10010
ictal hemiparesis (4,5), ictal paralysis (6,7), and inhibitory epilepsy (8-10). Fisher (2) suggested the
following diagnostic criteria: (a) focal paralysis occurring before convulsive movements in a limb, (b)
a similar deficit without convulsive movements, (c)
a convulsive seizure in one limb concomitant with
paralysis in another limb w i t h o u t convulsive movements, (d) paralytic episodes preceding other epileptic seizures, (e) a seizure discharge in the EEG
during the paralytic episodes, (f) episodes of paralysis in a clinical situation in which a seizure
rather than another type of episode is expected, (9)
episode resolution with antiepileptic drugs (AEDs)
but persistence with other therapeutic measures,
and (h) absence of other conditions accounting for
transient attacks of focal weakness. The mechanism
probably involves an epileptic focus inhibiting de-
R. F. SMITH ET AL.
scending motor tracts, rather than stimulating
them, as in convulsive seizures (11).
Although partial seizures with inhibitory motor
phenomena such as speech arrest are not rare
(3,4,6), only sporadic cases and small series of ictal
paralysis of the face, appendicular, or truncal
muscles have been reported. We report two adult
cases exhibiting inhibitory motor seizures manifested as prolonged focal weakness.
A 25-year-old right-handed man presented with
progressive left hemiparesis I year after resection of
a right frontal astrocytoma and completion of
whole brain radiation and chemotherapy. Postoperatively, typical seizures consisted of eye and head
deviation to the left, progressing to left-sided clonic
activity. These occurred approximately once a
week. There was no postictal weakness. Follow-up
computed tomography (CT) scan showed a slight
increase in tumor size with right frontal edema. The
patient developed a complete left hemiplegia over
the course of several days, and the EEG showed
semirhythmic delta activity in the right central region (Fig. 1A). There was no improvement after the
administration of dexamethasone 20 mg followed
by 6 mg four times daily (q.i.d.) for 3 days. The
hemiplegia had persisted for days before the pa-
tient was given 10 m g intravenous diazepam
(DZP), which resulted in resolution of the semirhythmic activity in 1 rain (Fig. 1B). Within 10 rain
of DZP injection, left upper and lower extremity
strength increased to 3-4/5. Phenytoin (PHT) was
initiated, and at a 3-month follow-up visit, his
strength remained 3--4/5.
A 31-year-old left-handed woman with a recurrent left frontoparietal anaplastic astrocytoma was
evaluated for right focal motor seizures. The tumor
was partially resected in 1988, followed by radiation therapy. After initial surgery and radiation, she
continued to have right focal motor seizures beginning in the lower or upper extremity. These seizures did not secondarily generalize. In 1993, seizure frequency increased to three times a week des p i t e s u p r a t h e r a p e u t i c levels of P H T a n d
therapeutic levels of phenobarbital (PB). She had
previously failed to respond to carbamazepine, valproate and primidone. Magnetic resonance imaging
(MRI) scan showed local tumor recurrence. After
debulking surgery, she continued to have right focal motor seizures, lasting 1-3 min and occurring
two to three times a week. She had a persistent
right-sided hemiparesis (proximal upper extremity
3/5, distal upper extremity 1-2/5, proximal lower
extremity 2-3/5, distal lower extremity 1-2/5). The
hemiparesis was clinically stable for more than 6
weeks. There was a mild worsening in the baseline
FP 1 - F 7
FP1 - F 7 ~
T 3 - 1"5
FP 2- F s
F8 - T 4
T6- 0 2
Te-O 2 ~
FP 1 - F 3
F3 - T 4
FP,-F ~ , . - , . _ . _ ~
F 3 - T4
Figure 1. A: EEG during hendplegia showing right frontotemporal delta activity. B: EEG 20 s after intravenous diazepam
administration showing marked reduction in right-sided delta activity.
16 J EPILEPSY, VOL. 10, NO. 1, 1997
INHIBITORY MOTOR STATUS
right hemiparesis for 15-30 min after simple partial
motor seizures. A trial of dexamethasone (10 mg
intravenously and 4 mg every 6 h for I week) failed
to improve strength. The EEG showed delta and
theta range slowing in the left centroparietal and
Clobazam (CLB) 10 mg was initiated at night and
PB was reduced by 15 mg at night. Initial improvement was observed the morning after she received
the first bedtime dose. In the next 4 days, her
strength i m p r o v e d to ~ 4 / 5 in all right-sided
muscle groups and remained at this functional level
for more than 6 months. She received no glucocorticoids during this period. She remained seizurefree with PHT, CLB, and reduced PB dose for more
than 6 months.
We reviewed the English language literature to
identify reported cases of inhibitory motor seizures.
The first source was a computerized Medline search
of the years 1978 to 1994 utilizing the following
keywords; epileptic paralysis, ictal hemiparesis,
nonconvulsive seizure, hemiparetic seizure, partial
paralysis, focal inhibitory seizure, unilateral atonic
seizure, and inhibitory motor seizure. Seizure and
hemiplegia were also cross-referenced. The second
source comprised references from previous case reports and our review of more than 40 neurology
and epilepsy texts published before 1950.
All patients developed episodic weakness that
typically lasted 2-30 min and recurred. The weakness usually progressed to paralysis and, after the
seizure, power of the involved extremities returned
to baseline.-Five patients reported an aura of numbness in the involved areas, and two patients reported lightheadedness. In only two previous cases
(Cases 12 and 15) was prolonged weakness reported. Such prolonged ictal episodes constitute inhibitory motor status. In Case 12 the symptoms
lasted 14 h, and in Case 15 the symptoms lasted 3
days and did not resolve until DZP was administered. The cases we report also manifested inhibitory motor status, which resolved with the administration of intravenous DZP (in ~10 min) or oral
CLB (improvement in 410 h).
The cases reported in the literature and our 2
cases include various neuropathologic lesions. An
etiology was determined in all but 5 of the adult
cases. In 17 of 22 (77%) adult cases, an anatomic
lesion was detected on neuroimaging or autopsy [7
tumor, 5 mesiotemporal sclerosis KMTS), 4 stroke].
Three other cases had evidence of at least one previous stroke and speculated an additional stroke
may have been responsible for the epileptic focus.
Case reports with insufficient data or phenomena
that did not meet criteria were not reviewed. These
included reports of brief atonia of childhood (12)
and negative myoclonus (6). These episodes required an antecedent motor stimulus and lasted
only 100-500 ms. In addition, other negative ictal
phenomenon, including ictal-associated sensory
deficits and speech arrest, were not reviewed.
EEG abnormalities were detected in 23 of the 26
(88%) cases. No EEG reported in Case 4. In the 4
pediatric cases, no anatomic lesions were detected
and there was no evidence of underlying disease.
However, all 4 had abnormal EEGs and 2 patients
had abnormal single photon emission computed tomography scans that corresponded to the cortically
represented area of the paresis.
Table I summarizes the characteristics of case reports described in the literature. The two cases in
the current report are included.
Age and Sex
There was no predilection for sex (11 males, 10
females) or age (range 4 months to 79 years), including our two cases (ages 25 and 31 years).
In 4 of the 7 tumor cases lesion location was reported. All 4 tumors were located in the frontoparietal region. In 3 of the 4 (75%) cases documented
strokes were located in the posterioinferior frontal
area, corresponding to the focal EEG abnormalities.
The 5 cases of MTS were documented by neuropathological examination; 4 were left-sided.
J EPILEPSY, VOL. 10, NO. 1, 1997 17
R. F. SMITH ET AL.
o .- ~
"~ o "~
U :~[~ ~
] EPILEPSY, VOL. 10, NO. 1, 1997
INHIBITORY MOTOR STATUS
U U U O ~
.~ ~ ' ~
0 0 ~
Inhibitory motor seizures have received relatively little attention since their original description
by Gowers in 1881 (1). However, epileptic seizures
that cause negative symptoms are not rare. These
include ietal speech arrest (13-16), amaurosis
(17,18), amnesia (19-21), numbness or deafness (22),
neglect (23), and alien hand syndrome (24). In patients also experiencing partial motor seizures, the
inhibitory phenomena may be difficult to differentiate from a Todd's paralysis. Such differentiation
requires a detailed history of the events and appropriate interpretation of the studies, which makes
evaluation of the other reported cases difficult.
Partial seizures that inhibit motor activity are
rarely reported but should be considered in the differential diagnosis of transient weakness. Unlike
other partial seizure symptoms which usually last
less than 3 rain, ictal focal motor inhibition can last
relatively longer, often more than 5 min. The primary seizure localization associated with inhibition
of appendicular musculature is the frontoparietal
sensorimotor cortex. Such seizures can cause an ictal paralysis that lasts more than 3 min. In contrast,
ictal paralysis associated with video-EEG documented temporal lobe seizures and pathologically
verified MTS typically lasts less than I rain (14). The
motor inhibition is the primary ictal manifestation
in the frontoparietal foci. In patients with mesiotemporal foci, impaired consciousness and automatisms are the primary ictal features and flaccidity of
an extremity is often subtle and not reported by the
patient or witnesses. Focal appendicular flaccidity
during complex partial seizures could result from
either active inhibition of motor cortex or areas mediating attention to motor (i.e., motor neglect).
In our two cases, the paresis persisted 2 to 42
days, most likely from continuous or intermittent
ictal discharges that directly inhibited motor activity, with Todd's paralysis or structural defect as
secondary mechanisms. Active inhibition is supported by the following observations: (a) both patients responded quickly to an AED; (b) Patient 1
had a documented ictal discharge that responded,
together with the hemiparesis, to intravenous DZP;
(c) weakness did not improve in either patient with
dexamethasone therapy administered before benzodiazepines (BZDs); (d) follow-up neuroimaging
studies in both cases showed no evidence of reduced tumor size to account for improved strength;
and (e) no other etiology for change in power was
identified. The improved strength induced with
AED treatment would not be expected if weakness
J EPILEPSY, VOL. 10, NO. 1, 1997 19
R.F. SMITH ET AL.
resulted solely from a Todd's paralysis. Furthermore, the rhythmic EEG changes consistent with an
ictal discharge would not be expected to improve
with BZDs if Patient 1 was in a postictal state (i.e.,
Todd's paralysis). In these cases, the focal paresis
appeared to be a manifestation of partial status,
similar to that in the 63-year-old woman reported
by Fisher (2) and the 12-year-old boy reported by
Hanson and Chodos (3).
Both our patients had frontoparietal tumors,
whereas Fisher's case had a left inferior parietal infarct on neuropathological examination and no
cause was identified in the case of Hanson and Chodos. The case of Hanson and Chodos predated the
magnetic resonance imaging (MRI) era, however,
and CT scans were not obtained, but the patient did
h a v e an a b n o r m a l EEG a n d ictal [ 9 9 m T c ] pertechnetate brain scan. Brain tumors and strokes
have been previously associated with prolonged
partial seizures (25-27). Although weakness of appendicular and axial muscles has rarely been reported to result from epileptic status, other inhibitory seizure symptoms such as speech arrest and
aphasia are well documented in epileptic status
Hanson and Chodos (3) reported increased uptake on [99mTc]-pertechnetate brain scans during inhibitory motor seizures in two patients. After AED
administration, brain scans became normal, epileptiform activity resolved, and strength gradually returned in the paretic limbs, which supports the concept that weakness resulted from an inhibitory motor seizure; i.e., epileptiform activity reduced motor
strength. In the first case we described, the abnormal EEG consistent with an ictal discharge resolved
with BZD administration and correlated with clinical improvement, which further supports the relation between the electrophysiological seizure activity and the paralysis. The right-sided weakness in
the second case also improved shortly after the administration of CLB.
Penfield and Jasper (15) reported that electrical
stimulation in the perisylvian language areas and
supplementary motor cortex could cause speech arrest. Furthermore, stimulation of the human premotor cortex could impair the ability to perform specific voluntary movement or to sustain a voluntary
contraction (30); L/iders et al. noted this defect in 17
of 42 patients undergoing premotor cortical stimulation and suggested that the premotor areas directly inhibit primary motor cortex or are involved
in voluntary movement integration and cannot
function during electrical stimulation. Wilson (31),
in discussing inhibitory motor seizures, provided
20 J EPILEPSY, VOL. 10, NO. 1, 1997
several useful postulates: The cerebrum is a continuously interacting balance of excitation and inhibition and seizures distort this balance, with focal
ictal paralysis reflecting activation of inhibitory
These cases suggest several clinical caveats. Inhibitory motor seizures should be considered in patients with frontoparietal lesions w h o develop
acute motor deficits. In such patients, if neuroimaging studies fail to disclose progression of the lesion or if the other disorders are excluded (e.g.,
transient ischemic attack), evaluation with an EEG
may be revealing. A brief trial of a BZD should be
considered if other etiologies have been excluded,
especially if the EEG is abnormal. Patients with
temporal lobe seizures causing transient focal
weakness should be evaluated with coronal T1weighted MRI to exclude MTS or other structural
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