Simultaneous Infantile and Partial Seizures F. Donat, MD; Francis S.
Jane
Wright,
Spasms
MD
Abstract We report 11 infants with infantile spasms who had partial seizures that occurred concurrently with the infantile spasms. We studied this phenomenon with time-locked video electroencephalography. The partial seizures began before the infantile spasms and continued after one or more infantile spasms in seven patients. An infantile spasm occurred at the beginning of the partial seizure in five patients. (One patient had both seizure types simultaneously.) The clinical descriptions of these combinations of seizures were confusing, since they did not match known seizure types. The genesis of these seizures may involve an interaction between processes of focal cortical epileptogenesis (partial seizures) and brainstem synchronization (infantile spasms) ( J Child Neurol 1991;6:246-250).
hile analyzing video electroencephalo-
W g rams
who
had infantile of patients 11 whose recorded patients spasms, we encountered with infantile spasms occurred concurrently partial seizures. Although it is known that partial seizures 2 may occur in patients who have infantile spasms, 1, there is only one previous account in the literature of the simultaneous occurrence of the two seizure We report and characterize the clinical and electroencephalographic features of these combinations of seizures.
types.3
Patients and Methods EEGs were obtained on these patients as part of the initial evaluation of their seizure disorders (eight patients) or for follow-up evaluation when seizures had failed to respond to medical treatment (three patients). In all 11 patients, the seizures were recorded during time-locked simultaneous video-EEG monitoring. In seven patients, the seizures were recorded on 21-channel NihonKohden EEG instruments (Irvine, CA) using standard recording techniques.’ Recording times were 50 minutes to 2 hours in four patients, and 2 to 7 hours in three patients. In the other four patients, the seizures were recorded on
16-channel video-EEG cable
telemetry equipment (Telefac-
Corp, Conshohocken, PA) using a longitudinal bipolar montage and printed off-line on paper. Recording time was tor
24 hours in these patients. Interictal EEG findings were defined as hypsarrhythmia or modified hypsarrhythmia by accepted diagnostic criteria.3, Ictal EEG changes at the time of infantile spasms were also those that have been described in the liter-
ature.66 The ictal EEG features of partial seizures were defined criteria and consisted of repetitive focal waves, or other rhythmic activity that showed evolution in amplitude and frequency. 1, 8
by customary spikes, sharp
Results Of the 11 patients, nine ranged in age from 6 weeks to 6 months, with median age 3 months. One patient was 17 months old, and one was 21 months old. There were four girls and seven boys. Associated neurologic disorders included none or unknown in two patients, brain malformations in three patients (including two with hemimegalencephaly), tuberous sclerosis in two patients, previous hypoxia-ischemia in one patient, and meningitis, head trauma, and Menkes’ disease in individual
patients. Received August 30, 1990. Received revised Oct 8, 1990. Accepted for publication Oct 9, 1990. From the Department of Pediatrics, Children’s Hospital, Ohio State University School of Medicine, Columbus, OH Presented in part at the American Electroencephalographic Society Annual Scientific Meeting, New Orleans, LA, September
23, 1989. Address correspondence to Dr Jane F. Donat, Children’s 700 Children’s Drive, Columbus OH 43205.
Hospital,
Interictal EEGs showed hypsarrhythmia in six patients and modified hypsarrhythmia in five patients. Infantile spasms were flexor, extensor, or mixed and usually occurred in series .6, 9 All infantile spasms were associated with an ictal change in the EEG that consisted of a high-voltage sharp- or slowwave transient. In many instances, a generalized
246
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decrement in the cerebral
activity followed the transient. In all patients, the infantile spasms and the related ictal EEG changes were bilateral; in three patients they were asymmetrical. At onset, each partial seizure was limited to a focal cortical area, although in several instances subsequent spread to adjacent cortical regions was seen. The partial seizures originated in the left hemisphere in eight patients, in the right hemisphere in one patient, in the frontal vertex in one patient, and in both hemispheres in one patient. Simple partial seizures consisted of clonic jerking or asymmetrical tonic stiffening of the contralateral extremities or trunk. Complex partial seizures consisted of staring, cessation of normal movements, chewing, contralateral turning of the head and eyes (in two patients), and tonic posturing of the contralateral upper extremity (in one patient). Two types of simultaneous seizures were recorded. In seven patients, partial seizures and infantile spasms overlapped. The partial seizures began before and continued after one or more infantile spasms, which were occurring in series. With some of these partial seizures, the focal EEG ictal activity could not be seen during the generalized slow-wave transient of the infantile spasm but could be seen again during the generalized decrement; in others of these partial seizures, the focal EEG ictal activity could be seen overriding the generalized slow-wave transient (Figure 1). Duration of the partial seizures ranged from 15 seconds to several minutes. The partial seizures were clinical in all patients. Three patients had simple partial motor seizures; these
originated in central, temporal, and parietal-occipital head regions. Four patients had complex partial seizures ; these originated in frontal, temporal, and parietal-occipital head regions, and from multiple foci in one hemisphere. In five patients, an infantile spasm occurred at the beginning of a partial seizure. The focal ictal EEG activity appeared as the generalized slow-wave transient of the infantile spasms abated or within several seconds of the onset of the generalized decrement (Figure 2). This pattern of combined seizures occurred with both isolated and serial infantile spasms, and the partial seizures abated before the next infantile spasm if they occurred during a series. Duration of the partial seizures ranged from 5 seconds to several minutes. In four patients, the seizures were clinical. One patient had partial motor seizures that originated in the parietal-occipital head region. Three patients had complex partial seizures that originated in the frontal head region. One pa-
tient had seizures that were only electrographic; these originated in the central head region. One patient had both types of simultaneous seizures. Simple partial seizures that originated in the right temporal head region overlapped with infantile spasms. Complex partial seizures that originated in the left frontal head region began at the same time
infantile spasm. Three of the 11 patients had other similar partial seizures recorded that were not associated with infantile spasms. This included one patient whose complex partial seizures began before and overlapped the infantile spasms and two patients whose as an
simple partial seizures or complex partial seizures began while an infantile spasm was abating. In these patients, most of the partial seizures occurred simultaneously with the infantile spasms. All patients had infantile spasms unassociated with partial seizures recorded during the same EEG. Currently, the duration of follow-up of these patients is too brief for ment and outcome.
an
account of response to treat-
Discussion The concurrence of infantile spasms and partial seizures has received little attention in the literature. Our patients had partial seizures that began before and continued after infantile spasms or partial seizures and infantile spasms that began at the same time. Hrachovy et a1,3 in their article describing the variations of hypsarrhythmia, noted that focal electrographic or clinical seizures occurred during clusters of infantile spasms, without appearing to have any effect on the occurrence of the clinical infantile spasms, on the ictal EEG changes associated with the infantile spasms, or on the background hypsarrhythmic EEG. Although further details of the seizures were not reported, these seizures appear to be similar to ones we recorded in our patients. Yamamoto et all° described four patients who had partial seizures that ended 10 to 25 seconds before infantile spasms began. These researchers felt that the consecutive occurrence of the two seizure types did not represent secondary generalization but that the descending electrical volley induced by the partial seizures stimulated an abnormal brain stem to trigger infantile spasms. Likewise, we did not think that the infantile spasms in our patients were the result of secondary generalization of the partial seizures in the conventional sense, since the partial seizures continued after the infantile spasms. It is generally accepted that partial seizures are
247
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FIGURE 1 A partial seizure beginning before and continuing during infantile spasm is seen in this EEG of a 2-month-old boy with brain malformation. Focal spiking (seen at C3-P3) increases in frequency and decreases in amplitude and is associated with a partial motor seizure affecting the right arm. This discharge can be seen to continue through, and override, the generalized sharp- and slow-wave transients of the infantile spasms (ar-
rows).
initiated in an epileptogenic focus in the cerebral cortex.ll The pathophysiology of primarily generalized seizures is not known, but evidence from experimental models implicates an interaction between cortical and subcortical mechanisms (the corticoreticular model).12 Secondarily generalized seizures represent spread from a cortical focus, but exactly how the spread occurs beyond the initial cerebral hemisphere is also uncertain.l3 Mechanisms of secondary generalization may vary with different seizure types. Generation of myoclonic seizures appears to involve the cerebral cortex; the brain stem appears to be involved in the development and expression of tonic seizures.l4-16 Infantile spasms have not yet been classified in the International Classification of Epi-
leptic Seizures, 17 although they are classified among the cryptogenic or symptomatic generalized epilepsies.l8 Whether they are generated at the level of the cerebral hemispheres or the brain stem is uncertrain.19 The clinical appearance of infantile spasms
varies, having
more
myoclonic or more
tonic charac-
teristics in individual seizures or in different paEEG is more like that of tonic seizures, which exhibit generalized decrements and low-voltage fast than it is like that of myoclonic seizures, which exhibit multiple
tients .9,20 However, the ictal
activity,21
spike-and-wave discharges.22 Other clinical evidence has implicated both cortical and subcortical mechanisms in the genesis of infantile spasms. Multifocal or diffuse cortical disease is implied by the hypsarrhythmia pattern on EEG and by the frequent findings of developmental delay, mental retardation, and associated diffuse or multifocal cerebral hemisphere disease by history or pathology.23-25 Focal cortical disease is indicated by the occurrence of partial seizures in some infantile 26, 27 spasm patients, 1, by focal epileptiform activity focal on EEG,2, 28 by cortical pathology found on radiologic studies or autopsy,29-31 and by positron emission tomographic (PET) scan results.32 Involvement of brain-stem structures in infantile spasm patients has been found by autopsy,33, 34 PET
248
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’
FIGURE 2 An infantile spasm abating as a partial seizure begins can be seen in this EEG of a 4-month-old boy with seizures of unknown cause. One of a series of infantile spasms occurs at the arrow. On EEG this is accompanied by a generalized slow-wave transient and decrement, with brief rhythmic slowing. As this generalized discharge is abating, the partial seizure emerges with rhythmic spiking that increases in frequency and amplitude in the left frontal (F3-F7) region. This is associated with complex partial symptoms including staring, head turning to the right, and clonic jerking of the right limbs.
scanning,35 abnormal brain-stem auditory-evoked potentials,36 disturbances in REM sleep, 37, and de38
fects in neurotransmitter metabolism.39, 40 The simultaneous development of partial seizures and infantile spasms in our patients suggests that these two types of seizures may be generated at different levels of the brain. In our patients whose partial seizures preceded and continued after infantile spasms, the concurrence of the two types of seizures may be coincidental, as suggested by the data of Hrachovy et al.~ However, an alternative explanation, similar to that proposed by Yamamoto et al, lo is that the partial seizure activates the infantile spasms by lowering the brain-stem threshold for the initiation of infantile spasms in susceptible infants. In patients in whom an infantile spasm occurred at the beginning of a partial seizure, mechanisms of cortical epileptogenesis for the initiation of partial seizures and brain-stem synchronization for the development of infantile spasms may be activated at the same time. The emergence of the partial seizure as the infantile spasm is abating suggests that the occurrence of the infantile spasm may enhance excitability in abnormal cerebral cortical foci, resulting in the generation of the partial seizure. Regardless of the theoretical implications of si-
multaneous infantile spasms and partial seizures, we feel that in order to obtain accurate diagnosis and appropriate treatment it is important for clinicians to be aware that these two seizure types may occur in combination. In our patients, the clinical seizure histories supplied by parents or other caretakers were confusing. Some parents described only the infantile spasms or only the partial seizures. Other parents’ attempts to describe the combinations did not correspond to known seizure types. Accurate clinical identification of both types of seizures was not made before video EEGs demonstrated the simultaneous seizures.
Acknowledgment The authors thank Gretchen Herr, R EEG T, for her technical assistance.
1.
References Jeavons PM: West syndrome: Infantile spasms, in Roger J, Dravet C, Bureau M, et al (eds): Epileptic Syndromes in Infancy, Childhood and Adolescence. London, John Libbey Eurotext,
1985, pp 42-50. 2. Riikonen R: A long-term
follow-up study of 214 children with 249
Downloaded from jcn.sagepub.com at NORTH CAROLINA STATE UNIV on April 6, 2015
3. 4.
5.
6.
the syndrome of infantile spasms. Neuropediatrics 1982; 13:14-23. Hrachovy RA, Frost JD Jr, Kellaway P: Hypsarrhythmia: Variations on the theme. Epilepsia 1984;25:317-325. American Electroencephalographic Society: Guidelines in EEG, 1-7 (revised 1985).J Clin Neurophysiol 1986;3:131168. Gibbs EL, Fleming MA, Gibbs FA: Diagnosis and prognosis of hypsarrhythmia and infantile spasms. Pediatrics 1954; 13:66-72. Kellaway P, Hrachovy RA, Frost JD Jr, Zion T: Precise characterization and quantification of infantile spasms. Ann Neurol
1979;6:214-218. 7. Geiger LR, Harner RN: EEG patterns at the time of focal seizure onset. Arch Neurol 1978;35:276-286. 8. Blume WT, Young GB, Lemieux JF: EEG morphology of partial
epileptic
seizures.
Electroencephalogr
Clin
Neurophysiol
1984;57:295-302. 9. King DW, Dyken PR, Spinks IL, Munro AJ: Infantile spasms: Ictal phenomena. Pediatr Neurol 1985;1:213-218. 10. Yamamoto N, Watanabe K, Negoro T, et al: Partial seizures 11. 12.
evolving to infantile spasms. Epilepsia 1988;29:34-40. Pedley TA: The pathophysiology of focal epilepsy: Neurophysiological considerations. Ann Neurol 1978;3:2-9. Gloor P: Generalized corticoreticular epilepsies: Some considerations on the pathophysiology of generalized bilaterally synchronous spike and wave discharge. Epilepsia 1968;9:
249-263. 13. Aird RB, Masland RL, Woodbury DM: Neurobiological substrates of epilepsy, in Aird RB, Masland RL, Woodbury DM (eds): The Epilepsies, A Critical Review. New York, Raven Press, 1984, pp 35-36. 14. Fromm GH: The brain-stem and seizures: Summary and synthesis, in Fromm GH, Faingold CL, Browning RA, Burnham WM (eds): Epilepsy and the Reticular Formation. The Role of the Reticular Core in Convulsive Seizures. Neurology and Biology, vol 27. New York, Alan R Liss, 1987, pp 203-218. 15. Gale K, Browning RA: Anatomical and neurochemical substrates of clonic and tonic seizures, in Dichter MA (ed): Mechanisms of Epileptogenesis. The Transition to Seizure. New York, Plenum Press, 1988, pp 111-152. 16. Engel J Jr: Seizures and Epilepsy. Philadelphia, FA Davis, 1989, pp 160-165. 17. Commission on Classification and Terminology of the International League Against Epilepsy: Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Epilepsia 1981;22:489-501. 18. Commission on Classification and Terminology of the International League Against Epilepsy: Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia
1989;30:389-399. Frost JD Jr, Hrachovy RA: Infantile spasms, in Morselli PL, Pippenger CE, Penry JK (eds): Antiepileptic Drug Therapy in Pediatrics. New York, Raven Press, 1983, pp 115-136. 20. Hrachovy RA, Frost JD Jr: Intensive monitoring of infantile spasms, in Schmidt D, Morselli PL (eds): Intractable Epilepsy. New York, Raven Press, 1986, pp 87-97. 19.
Kellaway P,
Roger J, Ouahchi S, et al: An electro-clinical study generalized epileptic seizures of tonic expression. Epilepsia
21. Gastaut H,
of
1963;4:15-44. 22.
23.
Halliday AM: The neurophysiology of myoclonic jerking—a reappraisal, in Charlton MH (ed): Myoclonic Seizures. Amsterdam, Excerpta Medica, 1975, pp 1-29. Lacy JR, Penry JK: Infantile Spasms. New York, Raven Press,
1976. 24. Meencke HJ: Morphological aspects of aetiology and the course of infantile spasms (West-syndrome). Neuropediatrics
1985;16:59-66. 25.
K: Neuropathological aspects of infantile spasms. Brain Dev 1987;9:349-357. 26. Dravet C, Catani C, Bureau M, Roger J: Partial epilepsies in infancy: A study of 40 cases. Epilepsia 1989;30:807-812. 27. Plouin P, Dulac O, Jalin C, Chiron C: Partial seizures in West syndrome: 24-hour ambulatory EEG monitoring. Epilepsia
Jellinger
1989;30:691. 28. Watanabe K, Iwase K, Hara K: The evolution of EEG features in infantile spasms: A prospective study. Dev Med Child Neurol 1973;15:584-596. 29. Tjam AT, Stefanko S, Schenk VWD, de Vlieger M: Infantile spasms associated with hemihypsarrhythmia and hemimegalencephaly. Dev Med Child Neurol 1978;20:779-798. 30. Alvarez LA, Shinnar S, Moshe SL: Infantile spasms due to unilateral cerebral infarcts. Pediatrics 1987;79:1024-1026. 31. Ruggieri V, Carabello R, Fejerman N: Intracranial tumors and West syndrome. Pediatr Neurol 1989;5:327-329. 32. Chugani HT, Shields WD, Shewmon DA, et al: Infantile spasms: I. PET identifies focal cortical dysgenesis in cryptogenic cases for surgical treatment. Ann Neurol
1990;27:406-413. 33. Neville BGR: The origin of infantile spasms: Evidence from a case of hydranencephaly. Dev Med Child Neurol 1972; 14:644-656. 34. Satoh J, Mizutani T, Morimatsu Y: Neuropathology of the brainstem in age-dependent epileptic encephalopathy—espe— cially of cases with infantile spasms. Brain Dev 1986; 8:443-449. 35. Chugani HT, Engel J Jr: PET in intractable epilepsy, in Schmidt D, Morselli PL (eds): Intractable Epilepsy. New York, Raven Press, 1986, pp 119-128. 36. Kaga K, Marsh RR, Fukuyama Y: Auditory brain stem responses in infantile spasms. Int J Pediatr Otorhinolaryngol
1982;4:57-67. 37.
Fukuyama Y, Shionaga A, Iida Y: Polygraphic study during whole night sleep in infantile spasms. Eur Neurol 1979;
38.
Hrachovy RA,
18:302-311. Frost JD Jr, Kellaway P: Sleep characteristics in infantile spasms. Neurology 1981;31:688-694. 39. Silverstein F, Johnston MV: Cerebrospinal fluid monoamine metabolites in patients with infantile spasms. Neurology
1984;34:102-105. 40. Rektor I,
Svejdova M, Silva-Barrat C, Menini CH: Central cholinergic hypofunction in physiopathology of West’s syndrome, in Wolf P, Dam M, Janz D, Dreifuss FE (eds): Adin Epileptology, vol 16. New York, Raven Press, 1987,
vances
pp 139-142.
250
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Jane
Wright,
Spasms
MD
Abstract We report 11 infants with infantile spasms who had partial seizures that occurred concurrently with the infantile spasms. We studied this phenomenon with time-locked video electroencephalography. The partial seizures began before the infantile spasms and continued after one or more infantile spasms in seven patients. An infantile spasm occurred at the beginning of the partial seizure in five patients. (One patient had both seizure types simultaneously.) The clinical descriptions of these combinations of seizures were confusing, since they did not match known seizure types. The genesis of these seizures may involve an interaction between processes of focal cortical epileptogenesis (partial seizures) and brainstem synchronization (infantile spasms) ( J Child Neurol 1991;6:246-250).
hile analyzing video electroencephalo-
W g rams
who
had infantile of patients 11 whose recorded patients spasms, we encountered with infantile spasms occurred concurrently partial seizures. Although it is known that partial seizures 2 may occur in patients who have infantile spasms, 1, there is only one previous account in the literature of the simultaneous occurrence of the two seizure We report and characterize the clinical and electroencephalographic features of these combinations of seizures.
types.3
Patients and Methods EEGs were obtained on these patients as part of the initial evaluation of their seizure disorders (eight patients) or for follow-up evaluation when seizures had failed to respond to medical treatment (three patients). In all 11 patients, the seizures were recorded during time-locked simultaneous video-EEG monitoring. In seven patients, the seizures were recorded on 21-channel NihonKohden EEG instruments (Irvine, CA) using standard recording techniques.’ Recording times were 50 minutes to 2 hours in four patients, and 2 to 7 hours in three patients. In the other four patients, the seizures were recorded on
16-channel video-EEG cable
telemetry equipment (Telefac-
Corp, Conshohocken, PA) using a longitudinal bipolar montage and printed off-line on paper. Recording time was tor
24 hours in these patients. Interictal EEG findings were defined as hypsarrhythmia or modified hypsarrhythmia by accepted diagnostic criteria.3, Ictal EEG changes at the time of infantile spasms were also those that have been described in the liter-
ature.66 The ictal EEG features of partial seizures were defined criteria and consisted of repetitive focal waves, or other rhythmic activity that showed evolution in amplitude and frequency. 1, 8
by customary spikes, sharp
Results Of the 11 patients, nine ranged in age from 6 weeks to 6 months, with median age 3 months. One patient was 17 months old, and one was 21 months old. There were four girls and seven boys. Associated neurologic disorders included none or unknown in two patients, brain malformations in three patients (including two with hemimegalencephaly), tuberous sclerosis in two patients, previous hypoxia-ischemia in one patient, and meningitis, head trauma, and Menkes’ disease in individual
patients. Received August 30, 1990. Received revised Oct 8, 1990. Accepted for publication Oct 9, 1990. From the Department of Pediatrics, Children’s Hospital, Ohio State University School of Medicine, Columbus, OH Presented in part at the American Electroencephalographic Society Annual Scientific Meeting, New Orleans, LA, September
23, 1989. Address correspondence to Dr Jane F. Donat, Children’s 700 Children’s Drive, Columbus OH 43205.
Hospital,
Interictal EEGs showed hypsarrhythmia in six patients and modified hypsarrhythmia in five patients. Infantile spasms were flexor, extensor, or mixed and usually occurred in series .6, 9 All infantile spasms were associated with an ictal change in the EEG that consisted of a high-voltage sharp- or slowwave transient. In many instances, a generalized
246
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decrement in the cerebral
activity followed the transient. In all patients, the infantile spasms and the related ictal EEG changes were bilateral; in three patients they were asymmetrical. At onset, each partial seizure was limited to a focal cortical area, although in several instances subsequent spread to adjacent cortical regions was seen. The partial seizures originated in the left hemisphere in eight patients, in the right hemisphere in one patient, in the frontal vertex in one patient, and in both hemispheres in one patient. Simple partial seizures consisted of clonic jerking or asymmetrical tonic stiffening of the contralateral extremities or trunk. Complex partial seizures consisted of staring, cessation of normal movements, chewing, contralateral turning of the head and eyes (in two patients), and tonic posturing of the contralateral upper extremity (in one patient). Two types of simultaneous seizures were recorded. In seven patients, partial seizures and infantile spasms overlapped. The partial seizures began before and continued after one or more infantile spasms, which were occurring in series. With some of these partial seizures, the focal EEG ictal activity could not be seen during the generalized slow-wave transient of the infantile spasm but could be seen again during the generalized decrement; in others of these partial seizures, the focal EEG ictal activity could be seen overriding the generalized slow-wave transient (Figure 1). Duration of the partial seizures ranged from 15 seconds to several minutes. The partial seizures were clinical in all patients. Three patients had simple partial motor seizures; these
originated in central, temporal, and parietal-occipital head regions. Four patients had complex partial seizures ; these originated in frontal, temporal, and parietal-occipital head regions, and from multiple foci in one hemisphere. In five patients, an infantile spasm occurred at the beginning of a partial seizure. The focal ictal EEG activity appeared as the generalized slow-wave transient of the infantile spasms abated or within several seconds of the onset of the generalized decrement (Figure 2). This pattern of combined seizures occurred with both isolated and serial infantile spasms, and the partial seizures abated before the next infantile spasm if they occurred during a series. Duration of the partial seizures ranged from 5 seconds to several minutes. In four patients, the seizures were clinical. One patient had partial motor seizures that originated in the parietal-occipital head region. Three patients had complex partial seizures that originated in the frontal head region. One pa-
tient had seizures that were only electrographic; these originated in the central head region. One patient had both types of simultaneous seizures. Simple partial seizures that originated in the right temporal head region overlapped with infantile spasms. Complex partial seizures that originated in the left frontal head region began at the same time
infantile spasm. Three of the 11 patients had other similar partial seizures recorded that were not associated with infantile spasms. This included one patient whose complex partial seizures began before and overlapped the infantile spasms and two patients whose as an
simple partial seizures or complex partial seizures began while an infantile spasm was abating. In these patients, most of the partial seizures occurred simultaneously with the infantile spasms. All patients had infantile spasms unassociated with partial seizures recorded during the same EEG. Currently, the duration of follow-up of these patients is too brief for ment and outcome.
an
account of response to treat-
Discussion The concurrence of infantile spasms and partial seizures has received little attention in the literature. Our patients had partial seizures that began before and continued after infantile spasms or partial seizures and infantile spasms that began at the same time. Hrachovy et a1,3 in their article describing the variations of hypsarrhythmia, noted that focal electrographic or clinical seizures occurred during clusters of infantile spasms, without appearing to have any effect on the occurrence of the clinical infantile spasms, on the ictal EEG changes associated with the infantile spasms, or on the background hypsarrhythmic EEG. Although further details of the seizures were not reported, these seizures appear to be similar to ones we recorded in our patients. Yamamoto et all° described four patients who had partial seizures that ended 10 to 25 seconds before infantile spasms began. These researchers felt that the consecutive occurrence of the two seizure types did not represent secondary generalization but that the descending electrical volley induced by the partial seizures stimulated an abnormal brain stem to trigger infantile spasms. Likewise, we did not think that the infantile spasms in our patients were the result of secondary generalization of the partial seizures in the conventional sense, since the partial seizures continued after the infantile spasms. It is generally accepted that partial seizures are
247
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FIGURE 1 A partial seizure beginning before and continuing during infantile spasm is seen in this EEG of a 2-month-old boy with brain malformation. Focal spiking (seen at C3-P3) increases in frequency and decreases in amplitude and is associated with a partial motor seizure affecting the right arm. This discharge can be seen to continue through, and override, the generalized sharp- and slow-wave transients of the infantile spasms (ar-
rows).
initiated in an epileptogenic focus in the cerebral cortex.ll The pathophysiology of primarily generalized seizures is not known, but evidence from experimental models implicates an interaction between cortical and subcortical mechanisms (the corticoreticular model).12 Secondarily generalized seizures represent spread from a cortical focus, but exactly how the spread occurs beyond the initial cerebral hemisphere is also uncertain.l3 Mechanisms of secondary generalization may vary with different seizure types. Generation of myoclonic seizures appears to involve the cerebral cortex; the brain stem appears to be involved in the development and expression of tonic seizures.l4-16 Infantile spasms have not yet been classified in the International Classification of Epi-
leptic Seizures, 17 although they are classified among the cryptogenic or symptomatic generalized epilepsies.l8 Whether they are generated at the level of the cerebral hemispheres or the brain stem is uncertrain.19 The clinical appearance of infantile spasms
varies, having
more
myoclonic or more
tonic charac-
teristics in individual seizures or in different paEEG is more like that of tonic seizures, which exhibit generalized decrements and low-voltage fast than it is like that of myoclonic seizures, which exhibit multiple
tients .9,20 However, the ictal
activity,21
spike-and-wave discharges.22 Other clinical evidence has implicated both cortical and subcortical mechanisms in the genesis of infantile spasms. Multifocal or diffuse cortical disease is implied by the hypsarrhythmia pattern on EEG and by the frequent findings of developmental delay, mental retardation, and associated diffuse or multifocal cerebral hemisphere disease by history or pathology.23-25 Focal cortical disease is indicated by the occurrence of partial seizures in some infantile 26, 27 spasm patients, 1, by focal epileptiform activity focal on EEG,2, 28 by cortical pathology found on radiologic studies or autopsy,29-31 and by positron emission tomographic (PET) scan results.32 Involvement of brain-stem structures in infantile spasm patients has been found by autopsy,33, 34 PET
248
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’
FIGURE 2 An infantile spasm abating as a partial seizure begins can be seen in this EEG of a 4-month-old boy with seizures of unknown cause. One of a series of infantile spasms occurs at the arrow. On EEG this is accompanied by a generalized slow-wave transient and decrement, with brief rhythmic slowing. As this generalized discharge is abating, the partial seizure emerges with rhythmic spiking that increases in frequency and amplitude in the left frontal (F3-F7) region. This is associated with complex partial symptoms including staring, head turning to the right, and clonic jerking of the right limbs.
scanning,35 abnormal brain-stem auditory-evoked potentials,36 disturbances in REM sleep, 37, and de38
fects in neurotransmitter metabolism.39, 40 The simultaneous development of partial seizures and infantile spasms in our patients suggests that these two types of seizures may be generated at different levels of the brain. In our patients whose partial seizures preceded and continued after infantile spasms, the concurrence of the two types of seizures may be coincidental, as suggested by the data of Hrachovy et al.~ However, an alternative explanation, similar to that proposed by Yamamoto et al, lo is that the partial seizure activates the infantile spasms by lowering the brain-stem threshold for the initiation of infantile spasms in susceptible infants. In patients in whom an infantile spasm occurred at the beginning of a partial seizure, mechanisms of cortical epileptogenesis for the initiation of partial seizures and brain-stem synchronization for the development of infantile spasms may be activated at the same time. The emergence of the partial seizure as the infantile spasm is abating suggests that the occurrence of the infantile spasm may enhance excitability in abnormal cerebral cortical foci, resulting in the generation of the partial seizure. Regardless of the theoretical implications of si-
multaneous infantile spasms and partial seizures, we feel that in order to obtain accurate diagnosis and appropriate treatment it is important for clinicians to be aware that these two seizure types may occur in combination. In our patients, the clinical seizure histories supplied by parents or other caretakers were confusing. Some parents described only the infantile spasms or only the partial seizures. Other parents’ attempts to describe the combinations did not correspond to known seizure types. Accurate clinical identification of both types of seizures was not made before video EEGs demonstrated the simultaneous seizures.
Acknowledgment The authors thank Gretchen Herr, R EEG T, for her technical assistance.
1.
References Jeavons PM: West syndrome: Infantile spasms, in Roger J, Dravet C, Bureau M, et al (eds): Epileptic Syndromes in Infancy, Childhood and Adolescence. London, John Libbey Eurotext,
1985, pp 42-50. 2. Riikonen R: A long-term
follow-up study of 214 children with 249
Downloaded from jcn.sagepub.com at NORTH CAROLINA STATE UNIV on April 6, 2015
3. 4.
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