Ictal monoparesis associated with CME lesions in the primary somatosensory area Abstract—Reported are three patients with ictal monoparesis of an arm. In the hemisphere contralateral to the monoparesis, ictal and interictal epileptiform discharges were observed in the centroparietal area, and a wellcircumscribed lesion was commonly present in the primary arm somatosensory area (SI). In the presence of an SI lesion, the epileptic activity at the sensorimotor area could lead to selective or predominant activation of the inhibitory motor system. NEUROLOGY 2005;65:1476–1478 R. Matsumoto, MD, PhD; A. Ikeda, MD, PhD; T. Hitomi, MD; T. Aoki, MD; T. Hanakawa, MD, PhD; Y. Miki, MD, PhD; H. Tomimoto, MD, PhD; S. Shimohama, MD, PhD; and H. Shibasaki, MD, PhD Inhibitory motor seizures are characterized by paresis or paralysis of a body part as ictal manifestation. Since first described by Gowers in 1885,1 this rare yet treatable condition is now recognized as an established entity in the International League Against Epilepsy proposal of epileptic seizure types.2 Its pathophysiology, however, has not been well elucidated because of limited ictal EEG and imaging documentation.3-5 We previously reported the findings of electrocorticographic (ECoG) recording during ictal monoparesis of an arm, which demonstrated ictal discharges in the contralateral primary arm motor area (arm MI).6 So far, we have had a total of three patients with ictal monoparesis of the arm. The well-circumscribed lesion commonly observed in the primary arm somatosensory area (arm SI) drew our attention to report this case series with an emphasis on the role of SI lesion in generation of the ictal monoparesis. One of them (Patient 3 in the current report) was reported elsewhere exclusively for ECoG findings.6 Case reports. Patient 1. A 38-year-old woman had been seen for symptomatic right frontal lobe epilepsy since the removal of the right frontal hematoma reportedly due to the cortical venous thrombosis. Her habitual seizures started with an aura of choked feeling in the throat, followed by the head and eye version to the left. Recently, she had sought for emergency medical assistance for an unusual episode that was different from the habitual sei- From the Departments of Neurology (Drs. Matsumoto, Ikeda, Hitomi, Tomimoto, Shimohama, and Shibasaki) and Diagnostic Imaging and Nuclear Medicine (Dr. Miki) and Human Brain Research Center (Dr. Hanakawa), Kyoto University Graduate School of Medicine, and Department of Neurosurgery (Dr. Aoki), Shiga Medical Center for Adults, Moriyama, Japan. Dr. Shibasaki’s current address is Takeda General Hospital, Kyoto, Japan. Supported in part by Grants-in-Aid for Young Scientists (B) 17790578 from the Japan Ministry of Education, Culture, Sports, Science, and Technology (MEXT) to R.M., by a Research Grant from the Japan Epilepsy Research Foundation to R.M., and by a Research Grant for Treatment of Intractable Epilepsy (16-1) from the Japan Ministry of Health, Labor and Welfare and from Fujiwara Foundation to A.I. Disclosure: The authors report no conflicts of interest. Received April 20, 2005. Accepted in final form July 22, 2005. Address correspondence and reprint requests to Dr. A. Ikeda, Department of Neurology, Kyoto University Graduate School of Medicine, 54 Kawaharacho, Shogoin, Sakyo, Kyoto, 606-8507, Japan; e-mail: akio@kuhp.kyotou.ac.jp 1476 Copyright © 2005 by AAN Enterprises, Inc. zures. She first experienced tonic stiffening of the left hand for half an hour and then had weakness of the left arm for approximately 3 hours. At the beginning of monoparesis, she also experienced “alien” sensation of the left hand for several minutes. Her awareness was not impaired. On admission, mild weakness of the left hand and arm was observed. The muscle tone was normal bilaterally. Sensory examination was unremarkable for touch, pain, vibration, and position sense. An emergency short-term video-EEG study showed the EEG status pattern consisting of regional ictal discharges in the right central region (figure 1A). She was diagnosed as having ictal monoparesis of the left arm, and carbamazepine was added to valproate. EEG recorded after the recovery from the paresis showed no epileptiform discharges (see figure 1B). Subsequent MRI and MR venography studies revealed multifocal thrombosis in the superior sagittal sinus and cortical veins. Fluid-attenuated inversion recovery image revealed a high-intensity abnormality along the right postcentral sulcus at the hand/arm portion where a fresh thrombus was noted in the right postcentral vein (figure 2, A and B). A high-intensity abnormality was also observed in the postcentral gyrus to a lesser degree. Patient 2. A 37-year-old man was treated in a local hospital for recurrent seizures. The seizures started with numbness or tingling sensation in the right hand for a while and mostly were followed by mild to moderate weakness of the right hand and arm without loss of consciousness, which lasted 1 to several minutes in total and on rare occasions for 20 to 30 minutes. No muscle stiffness was noticed by the patient except for two seizures during which mild transient tremulous movements of the arm were noted. In one of the prolonged seizures, he visited a local emergency room and was given IV diazepam, which immediately relieved the weakness. A meningioma was found in the left anterior parietal area, the majority of which was situated in the postcentral gyrus (see figure 2C). Despite subtotal resection of the meningioma and treatment with phenytoin and carbamazepine, he continued to have the habitual seizures. He was referred to us for prolonged video-EEG monitoring. Neurologic examination was unremarkable for motor and sensory systems, except for postoperative paresthesia in the right arm and on the ulnar side of the right hand. Although the aura was recorded once, no ictal discharges were observed in the scalp EEG. Interictally, sharp waves were infrequently seen in the left parietal area. Patient 3. A 30-year-old man had frequent auras of palpitation and chest discomfort, which on two occasions evolved into clonic seizures of the left arm. MRI revealed a low-grade glioma localized in the right postcentral gyrus around the hand/arm SI (see figure 2D). Neurologically, motor and sensory systems were normal including cortical sensation. He underwent functional cortical mapping with chronically implanted subdural electrodes. Two spontaneous seizures were recorded with video and ECoG. He was found to have mild to moderate weakness of the left arm and clumsiness of the left fingers during the aura. The muscle tone was normal. No convulsions were seen, but mild tremulous movements of the left arm were seen for several seconds in the middle of the second seizure. During the ictal monoparesis, ECoG showed rhythmic epileptiform discharges in the precentral area, which, when electrically stimulated, showed positive motor responses of the contralateral arm (arm MI). The monoparesis and aura and Figure 1. (A) Scalp EEG during ictal monoparesis of the left arm in Patient 1. Epileptiform discharges were continuously observed in the right central region. Two representative pages are shown. (B) Scalp EEG after recovery from the ictal monoparesis on the next day. No epileptiform activity was seen. ictal discharges all disappeared immediately after IV injection of diazepam. Discussion. Among the three cases reported here, episodic monoparesis of the arm was accompanied by ictal EEG discharge in two patients: at the contralateral central area (scalp EEG) in Patient 1 and at the contralateral arm MI (ECoG) in Patient 3. In Patient 2, although no ictal EEG was recorded, complete recovery from the monoparesis by IV diazepam, together with interictal spikes at the contralateral parietal area, strongly suggests the epileptic nature of the monoparesis. Therefore, all three patients most likely had an inhibitory motor seizure of an upper extremity. In addition, positive, but very mild, motor symptoms or somatosensory sensation was seen in the same extremity at a certain period dur- ing the course of seizures. Taken together with epileptiform EEG activities seen over the contralateral centroparietal area and the presence of pathology in the corresponding SI, this localized, consistent somatotopy of ictal manifestation is suggestive of the involvement of the sensorimotor area in generation of ictal monoparesis. All three patients had a well-circumscribed lesion in the contralateral hand/arm SI, and thus it is reasonable to speculate that the SI lesion is closely related to the pathophysiology. With the presence of SI lesion, the epileptic activity at MI could have caused either direct or indirect activation of the inhibitory system. As documented by ECoG in Patient 3, ictal discharges at MI probably inhibited spinal motoneuron pool without eliciting excitatory activity in the Figure 2. Brain MRI showing the lesion in the hand/arm portion of the primary somatosensory area contralateral to the ictal monoparesis of the arm. An arrowhead indicates the central sulcus. (A) Fluid-attenuated inversion recovery image of Patient 1. A high-intensity abnormality is present along the right postcentral sulcus and in the right postcentral gyrus to a lesser degree. A right prefrontal lesion is derived from the removal of the hematoma reportedly due to cortical venous thrombosis. (B) T1-weighted image of Patient 1. Note a fresh venous thrombus in the right postcentral vein (an arrow). (C) T1-weighted image of Patient 2 taken after the subtotal resection of meningioma. The majority of the lesion is located in the left postcentral gyrus. (D) T2-weighted image of Patient 3. A well-demarcated highintensity lesion, consistent with a lowgrade glioma, is seen in the right postcentral gyrus. Another MRI with different scan sequence appeared elsewhere.6 November (1 of 2) 2005 NEUROLOGY 65 1477 corticospinal pathway, being consistent with the isolated silent period evoked by stimulation of MI.7 Alternatively, focal discharges at SI might have caused selective or predominant activation of the inhibitory motor system. The latter speculation seems plausible as epileptic discharges in the arm SI were associated with pure negative myoclonus in the contralateral arm in an epilepsy patient, who, to our interest, also had the altered arm SI due to focal cortical dysplasia.8 Moreover, single or repetitive intracortical microstimulation of SI in monkeys produced predominantly inhibitory effects, but not complete suppression, on ongoing voluntary muscle contraction.9 This observation is in conformity with the clinical feature of our patients, that is, mild paresis, not complete paralysis, of the affected arm. The previous literature implicated the symptomatogenic zone of ictal paresis in the contralateral temporal lobe10 or the negative motor area,4,5 a part of the premotor area that produces bilateral or widely distributed motor inhibition when electrically stimulated. In the former, ictal paresis was always associated with loss of awareness and automatisms. The latter caused paresis of one or more distal extremities with occasional concomitant facial muscle twitches due to epileptic involvement of the adjacent face motor area. Clinical features of the current cases are clearly different from these two conditions because of preserved consciousness and apparently equal involvement of both distal and proximal parts of an extremity. It is, however, difficult to differenti- ate ictal monoparesis from TIA or postictal paresis only from the clinical symptomatology, and thus EEG could help to make a diagnosis of this treatable condition. Acknowledgment The authors thank Ms. Kuniko Iwata (EEG technologist, Kyoto University Hospital) for technical assistance. References 1. Gowers WR. Epilepsy and other chronic convulsive diseases. New York: William Wood, 1885. 2. Engel J, Jr. A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology. Epilepsia 2001;42:796–803. 3. Abou-Khalil B, Fakhoury T, Jennings M, Moots P, Warner J, Kessler RM. Inhibitory motor seizures: correlation with centroparietal structural and functional abnormalities. Acta Neurol Scand 1995;91:103– 108. 4. Noachtar S, Lüders HO. Focal akinetic seizures as documented by electroencephalography and video recordings. Neurology 1999;53:427–429. 5. Meletti S, Rubboli G, Testoni S, et al. Early ictal speech and motor inhibition in fronto-mesial epileptic seizures: a polygraphic study in one patient. Clin Neurophysiol 2003;114:56–62. 6. Matsumoto R, Ikeda A, Ohara S, et al. Nonconvulsive focal inhibitory seizure: subdural recording from motor cortex. Neurology 2000;55:429– 431. 7. Ikeda A, Ohara S, Matsumoto R, et al. Role of primary sensorimotor cortices in generating inhibitory motor response in humans. Brain 2000;123:1710–1721. 8. Noachtar S, Holthausen H, Lüders HO. Epileptic negative myoclonus. Subdural EEG recordings indicate a postcentral generator. Neurology 1997;49:1534–1537. 9. Widener GL, Cheney PD. Effects on muscle activity from microstimuli applied to somatosensory and motor cortex during voluntary movement in the monkey. J Neurophysiol 1997;77:2446–2465. 10. Oestreich LJ, Berg MJ, Bachmann DL, Burchfiel J, Erba G. Ictal contralateral paresis in complex partial seizures. Epilepsia 1995;36:671– 675. 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