Inhibitory focal epilepsy status chapter

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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. In- hibitory 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.

Inhibi tory motor seizures are manifested as a paroxysmal paralysis of the face, arm, leg, or hemi- body 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. Inhibi- tory motor seizures have been periodical ly 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 Uni-

versity 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.

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 wi thout convulsive movements, (c) a convulsive seizure in one limb concomitant with paralysis in another limb wi thout 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 si tuation 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-

J. Epilepsy 1997;10:15-21 �9 1997 by Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010

0896-6974/97/$17.00 Pit 50896-697-t(96)00072-2

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.

tient was given 10 mg intravenous d iazepam (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.

Case 2

Case Reports

Case 1

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. Postop- eratively, 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-

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 begin- ning in the lower or upper extremity. These seizures did not secondarily generalize. In 1993, seizure frequency increased to three times a week de- sp i te s u p r a t h e r a p e u t i c levels of PHT and therapeutic levels of phenobarbital (PB). She had previously failed to respond to carbamazepine, val- proate 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

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16 J EPILEPSY, VOL. 10, NO. 1, 1997

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 temporal regions.

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 s trength improved to ~ 4 / 5 in all r ight-sided muscle groups and remained at this functional level for more than 6 months. She received no glucocor- ticoids during this period. She remained seizure- free with PHT, CLB, and reduced PB dose for more than 6 months.

Literature Review

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.

Inclusion Criteria

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 re- quired 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.

Results

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).

INHIBITORY MOTOR STATUS

Clinical Manifestations

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).

Underlying Disease

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.

EEG Abnormalities

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.

Lesion Localization

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 posterioinferio r 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.

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Discuss ion

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 differen- tiate from a Todd's paralysis. Such differentiation requires a detailed history of the events and appro- priate 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 dif- ferential 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 automa- tisms 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 me- diating 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 sup- ported 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 ben- zodiazepines (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


R.F. SMITH ET AL.

resulted solely from a Todd's paralysis. Further- more, 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 in- farct on neuropathological examination and no cause was identified in the case of Hanson and Cho- dos. 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 and ictal [99mTc] -

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 (13,28,29).

Hanson and Chodos (3) reported increased up- take 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 con- cept 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 rela- tion 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 spe- cific 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 con- tinuously interacting balance of excitation and inhibition and seizures distort this balance, with focal ictal paralysis reflecting activation of inhibitory mechanisms.

These cases suggest several clinical caveats. In- hibitory motor seizures should be considered in patients with frontoparietal lesions who 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 T1- weighted MRI to exclude MTS or other structural lesions.

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Inhibitory focal epilepsy status chapter