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Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere
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Electroencephalographyand clinical Neurophysiology99 (1996) 440-443
Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere B. S a n t o s h k u m a r , K. R a d h a k r i s h n a n * Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695 011, India
Accepted for publication: 22 May 1996
Abstract We report a 15 year old girl with a childhood hemiplegia, who developed a recent progressive intellectual decline associated with elevated globulins and measles antibody titres in the cerebrospinal fluid, indicating a diagnosis of subacute sclerosing panencephalitis (SSPE). The magnetic resonance imaging revealed left hemispheric atrophy concordant with a long-standing right hemiplegia, and electroencephalography exhibited lateralized periodic complexes (PCs) over the right hemisphere concordant with left-sided myoclonic jerks. The modification of PCs in our patient due to preexisting damaged cerebral hemisphere illustrate that a fairly functional cortex and subcortical white matter are needed for the expression of the PCs of SSPE. Keywords: Subacute sclerosing panencephalitis; Hemiplegia; Periodic complexes; Electroencephalography
1. Introduction Subacute sclerosing panencephalitis (SSPE) is a slowly progressive fatal inflammatory disease of the central nervous system affecting children and young adults (Dyken, 1985). The diagnosis of SSPE can be established if the patient fulfils any 3 of the following 5 criteria (Dyken, 1985): (1) typical clinical presentation with inexorable cognitive decline and stereotyped myoclonic jerks; (2) typical electroencephalographic (EEG) pattern; (3) elevated cerebrospinal fluid (CSF) globulin levels; (4) elevated CSF measles antibody titres; and (5) typical histological findings in brain biopsy or autopsy. The EEG pattern in SSPE is one of the most characteristic and disease-specific of all EEG patterns (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983; Westmoreland, 1993). The pathognomonic periodic complexes (PCs) consist of generalized bisynchronous and symmetrical slow waves of high amplitude and a long repetition interval (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983). However, several atypical EEG findings in SSPE have been documented * Corresponding author. Tel.: +91 471 446069; fax: +91 471 446433; e-mail: [email protected]
(Table 1). The role of preexisting brain disorders in modifying the EEG pattern in SSPE seems to have received little attention. Our report of a patient with SSPE with atypical EEG findings related to preexisting brain lesion is therefore of interest.
2. Case report A 15 year old girl was hospitalized during March, 1995, with a history of progressive cognitive decline of 10 months duration, and myoclonic jerks involving the left side of the body of 4 months duration. She was born fullterm after a caesarean section and had normal milestones of development. She suffered 3 episodes of acute bacterial meningitis, secondary to CSF rhinorrhoea, between the ages of 3 and 5 years. The second episode was complicated by the development of a right hemiplegia and aphasia from which she partially recovered in 6 months, but was left with a mild spastic fight hemiparesis. S h e became lefthanded subsequently. She suffered infrequent right simple partial seizures involving fight upper limb and right half of the face, which necessitated treatment with sodium valproate. She was independent in all her activities of daily living and was above average in school performance. The sodium valproate therapy was withdrawn in January, 1994, after a
0013-4694/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0921 - 884X(96)96540-6
EEG 96540
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
441
seizure-free period of over 3 years. In June, 1994, she had 3 episodes of unprovoked generalized tonic-clonic seizures followed by left-sided myoclonic jerks and gradual decline in scholastic performance. The generalized seizures did not recur after the reintroduction of sodium
valproate therapy, 1800 mg daily, however, the myoclonic jerks did not abate. Examination revealed a conscious and alert girl. She had moderate dementia, a right supranuclear facial paresis and spasticity of right sided extremities. The tendon jerks were brisk on the right side; however, there was no Babinski sign. The most notable finding at examination was the presence of stereotyped periodic myoclonic jerks involving left-sided extremities and the left half of the face. The content and comprehension of speech was normal; however, the articulation was interrupted by facial myoclonic movements. The gait was disturbed by left lower extremity jerks and she needed support to walk. Routine urine analysis, hematocrit and blood biochemistry were normal. CSF showed 5 lymphocytes//zl and protein content of 0.15 g/l, of which globulins comprised 40% (normal <20%). The CSF measles antibody titre by ELISA was more than 1:10000 (normal <1:20). A 16 channel EEG exhibited a background activity of 7 Hz. Periodic lateralized slow wave discharges occurred over the right hemisphere at intervals of 2.5-3 s which showed a one to one relationship to left-sided myoclonic jerks (Fig. 1). A cranial MRI revealed marked loss of volume of left cerebral hemisphere associated with dilation of left lateral ventricle (Fig. 2).
T3 . T5 ~
~
Table 1 Atypical EEG findings in SSPE Finding
Reference
Prolonged and variable interval between PCs Asymmetric/focal PCs
Reiher et al., 1973 Markand and Panszi, 1975 Westmoreland et al., 1977 Lombroso, 1968 Martinovit, 1986 Farrel et al., 1971
Activation of PCs by sleep Activation of PCs by parent~;ral diazepam Periodic generalized bursts of fast waves Disappearance of PCs by a rise in body temperature Stimulus-evoked PCs and motor spasms Focal spikes and slow waves, and random spikes in frontal regions Multifocal paroxysmal high-amplitude slow waves during the presymptomatic stage Frontal rhythmic delta activity
Westmoreland et al., 1979 Markand and Panszi, 1975 Gimtnez-Rold~n et al., 1981 Markand and Panszi, 1975
~
t00 pv I
' ! I - OI . . ~ ~
n
.
t s,,~.
1'4
•4
Fig. 1. Awake EEG shows l~.riodic slow wave discharges over the right hemisphere. Surface electromyogram in the bottom channel reveals myoclonic jerks in the left upper extremity.
442
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
Fig. 2. Tl-weighted MR image demonstratesleft cerebral hemispheric atrophy and dilation of left lateral ventricle. She was discharged and referred to the care of a local nursing home facility. Her neurologic illness relentlessly progressed. By December, 1995, she became akinetic, semiconscious and mute, and died in April, 1996, due to complications of prolonged bed-bound state.
3. Discussion The patient described here fulfilled the criteria for clinical diagnosis of SSPE (Dyken, 1985). She exhibited progressive intellectual decline and stereotyped myoclonic jerks. CSF revealed a markedly elevated measles antibody titre and globulins. The unusual features were the strictly left-sided myoclonic jerks and concordant right hemispheric PCs in the EEG. MRI showed left cerebral hemispheric atrophy, presumably related to a vascular insult during early childhood, secondary to meningitis and arteritis. The characteristic PCs in SSPE consist of stereotyped, bilaterally synchronous and symmetrical high amplitude delta waves repeating with a fair regularity every 4 - 1 5 s (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983; Westmoreland, 1993). When clinical myoclonic jerks are present, there is a one to one relation-
ship of the jerks to the EEG complexes and once established, they are no longer influenced by sleep, drugs or external stimuli (Westmoreland, 1993). Initially, the PCs of SSPE may be somewhat asymmetric or occur irregularly before evolving into a regular repetition rate (Miller and Westmoreland, 1983). Out of the 31 patients with proved SSPE studied by Markand and Panszi (1975), pronounced asymmetry of the PCs was noted in only 3 patients. Of these, two had PCs higher in amplitude over the left hemisphere associated with myoclonic jerks of the right side of the body. However, the anatomo-pathological changes which could be ascribed to this phenomenon were not explored. Rarely, the PCs were reported to be entirely focal (Markand and Panszi, 1975). The EEG pattern of periodic lateralized epileptiform discharges (PLEDs) may superficially resemble EEG findings as seen in our patient. PLEDs consist of unilateral, high amplitude sharp waves or spikes that occur with a more or less regular periodicity, usually once in 1 or 2 s (Chatrian et al., 1964; Reiher et al., 1991). PLEDs occur in the setting of an acute focal cerebral hemispheric insult such as an infarct or encephalitis and the EEG complexes are either focal or lateralized, and regardless of the course of the disease process, they spontaneously disappear in a
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
few days or weeks (Chatrian et al., '1964; Reiher et al., 1991). However, occasitonally PLEDs can be chronic and can persist for several months or years (Westmoreland et al., 1986). The differentiation of PLEDs from the type of periodicity seen in our patient is therefore arbitrary. However, the major difference in our patient is that the PLEDs occurred over the normal hemisphere as shown by the MRI, thereby indicating a projected electrical disturbance. There is no satisfactory model to explain the pathogenesis of generalized periodic discharges. Four hypotheses concerning the origin of the PCs in SSPE have been proposed: (1) deep thalarnic or mesencephalic-reticular origin, associated with relative integrity of the cortex and thalamo-cortical pathways (Cobb, 1966; Lombroso, 1968); (2) origin from cortex isolated from subcortical structures (Lesse et al., 1958; Strom van Leeuwen, 1964); (3) involvement of both grey and white matter resulting in a disturbance of the normal cortico-subcortical electrical interaction (Gloor et al., 1968); and (4) a diffuse disturbance of the time constant of recovery of an electrochemical process at the cellular level (Cobb, 1979). The absence of the PCs over the side of long-standing cerebral hemispheric damage as observed in our patient shows that a fairly functional cortex and subcortical white matter are needed for the expression of generalized PCs of SSPE. References Chatrian, G.E., Shaw, C.M. and Leffman, H. The significance of periodic epileptiform discharges in EEG: an electrographic, clinical and pathological study. Electroenceph. clin. Neurophysiol., 1964, 17: 177-193. Cobb, W.A. The periodic ew,~ntsof subacute sclerosing leucoencephalitis. Electroenceph. clin. Neurophysiol., 1966, 21: 278-294. Cobb, W.A. Evidence on the periodic mechanism in herpes simplex encephalitis. Electroenceph. clin. Neurophysiol., 1979, 46: 345-350. Dyken, P.R. Subacute sclerosing panencephalitis. Neurol. Clin., 1985, 3: 179-195. Farrel, D.F., Starr, A. and Freeman, J.M. The effect of body temperature
443
on the 'periodic complexes' of subacute sclerosing panencephalitis (SSPE). Electroenceph. clin. Neurophysiol., 1971, 30: 415-421. Gim6nez-Rold,fm, S., Mar6n, M., Mateo, D. and Lopez-Fraile, I.P. Preclinical EEG abnormalities in subacute sclerosing panencephalitis. Neurology, 1981, 31: 763-767. Gloor, P., Kalabay, O. and Giard, N. The electroencephalogram in diffuse encephalopathies: electroencephalographic correlates of grey and white matter lesions. Brain, 1968, 91: 779-802. Lesse, S., Hoefer, P.F.A. and Austin, J.H. The electroencephalogram in diffuse encephalopathies. Arch. Neurol. Psychiatry, 1958, 79: 359375. Lombroso, C.T. Remarks on the EEG and movement disorder in SSPE. Neurology, 1968, 18 (2): 69-75. Markand, O.N. and Panszi, J.G. The electroencephalogram in subacute sclerosing panencephalitis. Arch. Neurol., 1975, 32: 719-726. Martinovi6, ~. Periodic generalized bursts of fast waves in subacute sclerosing panencephalitis. Electroenceph. clin. Neurophysiol., 1986, 63: 236-238. Miller, C.R. and Westmoreland, B.F. The EEG in slow virus diseases. Am. J. EEG Technol., 1983, 23: 209-217. Reiher, J., Lapointe, L.R. and Lessard, L. Prolonged and variable intervals between EEG complexes in subacute inclusion body encephalitis. Can. Med. Assoc. J., 1973, 108: 729-732. Reiher, J., Rivest, J., Grand'Malson, F. and Leduc, C. Periodic lateralised epileptiform discharges with transitional rhythmic discharges: association with seizures. Electroenceph. clin. Neurophysiol., 1991, 78: 1217. Strom van Leeuwen, W. Electroencephalographical and neurophysiological aspects of subacute sclerosing leuco-encephalitis. Psychiatr. Neurol. Neurochir., 1964, 67: 312-322. Westmoreland, B.F. The EEG in cerebral inflammatory processes. In: E. Niedermeyer and F. Lopes Da Silva (Eds.), Electroencephalography: Basic Principles, Clinical Applications, and Related Fields, 3rd edn. Williams and Wilkins, Baltimore, 1993, pp. 291-304. Westmoreland, B.F., Gomez, M.R. and Blume, W.T. Activation of periodic complexes of subacute sclerosing panencephalitis by sleep. Ann. Neurol., 1977, 1: 185-187. Westmoreland, B.F., Sharbrough, F.W. and Donat, J.R. Stimulusinduced EEG complexes and motor spasms in subacute sclerosing panencephalitis. Neurology, 1979, 29:1154-57. Westmoreland, B.F., Klass, D.W. and Sharbrough, F.W. Chronic periodic lateralized epileptiform discharges. Arch. Neurol., 1986, 43: 494-496.
Electroencephalographyand clinical Neurophysiology99 (1996) 440-443
Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere B. S a n t o s h k u m a r , K. R a d h a k r i s h n a n * Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695 011, India
Accepted for publication: 22 May 1996
Abstract We report a 15 year old girl with a childhood hemiplegia, who developed a recent progressive intellectual decline associated with elevated globulins and measles antibody titres in the cerebrospinal fluid, indicating a diagnosis of subacute sclerosing panencephalitis (SSPE). The magnetic resonance imaging revealed left hemispheric atrophy concordant with a long-standing right hemiplegia, and electroencephalography exhibited lateralized periodic complexes (PCs) over the right hemisphere concordant with left-sided myoclonic jerks. The modification of PCs in our patient due to preexisting damaged cerebral hemisphere illustrate that a fairly functional cortex and subcortical white matter are needed for the expression of the PCs of SSPE. Keywords: Subacute sclerosing panencephalitis; Hemiplegia; Periodic complexes; Electroencephalography
1. Introduction Subacute sclerosing panencephalitis (SSPE) is a slowly progressive fatal inflammatory disease of the central nervous system affecting children and young adults (Dyken, 1985). The diagnosis of SSPE can be established if the patient fulfils any 3 of the following 5 criteria (Dyken, 1985): (1) typical clinical presentation with inexorable cognitive decline and stereotyped myoclonic jerks; (2) typical electroencephalographic (EEG) pattern; (3) elevated cerebrospinal fluid (CSF) globulin levels; (4) elevated CSF measles antibody titres; and (5) typical histological findings in brain biopsy or autopsy. The EEG pattern in SSPE is one of the most characteristic and disease-specific of all EEG patterns (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983; Westmoreland, 1993). The pathognomonic periodic complexes (PCs) consist of generalized bisynchronous and symmetrical slow waves of high amplitude and a long repetition interval (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983). However, several atypical EEG findings in SSPE have been documented * Corresponding author. Tel.: +91 471 446069; fax: +91 471 446433; e-mail: [email protected]
(Table 1). The role of preexisting brain disorders in modifying the EEG pattern in SSPE seems to have received little attention. Our report of a patient with SSPE with atypical EEG findings related to preexisting brain lesion is therefore of interest.
2. Case report A 15 year old girl was hospitalized during March, 1995, with a history of progressive cognitive decline of 10 months duration, and myoclonic jerks involving the left side of the body of 4 months duration. She was born fullterm after a caesarean section and had normal milestones of development. She suffered 3 episodes of acute bacterial meningitis, secondary to CSF rhinorrhoea, between the ages of 3 and 5 years. The second episode was complicated by the development of a right hemiplegia and aphasia from which she partially recovered in 6 months, but was left with a mild spastic fight hemiparesis. S h e became lefthanded subsequently. She suffered infrequent right simple partial seizures involving fight upper limb and right half of the face, which necessitated treatment with sodium valproate. She was independent in all her activities of daily living and was above average in school performance. The sodium valproate therapy was withdrawn in January, 1994, after a
0013-4694/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0921 - 884X(96)96540-6
EEG 96540
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
441
seizure-free period of over 3 years. In June, 1994, she had 3 episodes of unprovoked generalized tonic-clonic seizures followed by left-sided myoclonic jerks and gradual decline in scholastic performance. The generalized seizures did not recur after the reintroduction of sodium
valproate therapy, 1800 mg daily, however, the myoclonic jerks did not abate. Examination revealed a conscious and alert girl. She had moderate dementia, a right supranuclear facial paresis and spasticity of right sided extremities. The tendon jerks were brisk on the right side; however, there was no Babinski sign. The most notable finding at examination was the presence of stereotyped periodic myoclonic jerks involving left-sided extremities and the left half of the face. The content and comprehension of speech was normal; however, the articulation was interrupted by facial myoclonic movements. The gait was disturbed by left lower extremity jerks and she needed support to walk. Routine urine analysis, hematocrit and blood biochemistry were normal. CSF showed 5 lymphocytes//zl and protein content of 0.15 g/l, of which globulins comprised 40% (normal <20%). The CSF measles antibody titre by ELISA was more than 1:10000 (normal <1:20). A 16 channel EEG exhibited a background activity of 7 Hz. Periodic lateralized slow wave discharges occurred over the right hemisphere at intervals of 2.5-3 s which showed a one to one relationship to left-sided myoclonic jerks (Fig. 1). A cranial MRI revealed marked loss of volume of left cerebral hemisphere associated with dilation of left lateral ventricle (Fig. 2).
T3 . T5 ~
~
Table 1 Atypical EEG findings in SSPE Finding
Reference
Prolonged and variable interval between PCs Asymmetric/focal PCs
Reiher et al., 1973 Markand and Panszi, 1975 Westmoreland et al., 1977 Lombroso, 1968 Martinovit, 1986 Farrel et al., 1971
Activation of PCs by sleep Activation of PCs by parent~;ral diazepam Periodic generalized bursts of fast waves Disappearance of PCs by a rise in body temperature Stimulus-evoked PCs and motor spasms Focal spikes and slow waves, and random spikes in frontal regions Multifocal paroxysmal high-amplitude slow waves during the presymptomatic stage Frontal rhythmic delta activity
Westmoreland et al., 1979 Markand and Panszi, 1975 Gimtnez-Rold~n et al., 1981 Markand and Panszi, 1975
~
t00 pv I
' ! I - OI . . ~ ~
n
.
t s,,~.
1'4
•4
Fig. 1. Awake EEG shows l~.riodic slow wave discharges over the right hemisphere. Surface electromyogram in the bottom channel reveals myoclonic jerks in the left upper extremity.
442
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
Fig. 2. Tl-weighted MR image demonstratesleft cerebral hemispheric atrophy and dilation of left lateral ventricle. She was discharged and referred to the care of a local nursing home facility. Her neurologic illness relentlessly progressed. By December, 1995, she became akinetic, semiconscious and mute, and died in April, 1996, due to complications of prolonged bed-bound state.
3. Discussion The patient described here fulfilled the criteria for clinical diagnosis of SSPE (Dyken, 1985). She exhibited progressive intellectual decline and stereotyped myoclonic jerks. CSF revealed a markedly elevated measles antibody titre and globulins. The unusual features were the strictly left-sided myoclonic jerks and concordant right hemispheric PCs in the EEG. MRI showed left cerebral hemispheric atrophy, presumably related to a vascular insult during early childhood, secondary to meningitis and arteritis. The characteristic PCs in SSPE consist of stereotyped, bilaterally synchronous and symmetrical high amplitude delta waves repeating with a fair regularity every 4 - 1 5 s (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983; Westmoreland, 1993). When clinical myoclonic jerks are present, there is a one to one relation-
ship of the jerks to the EEG complexes and once established, they are no longer influenced by sleep, drugs or external stimuli (Westmoreland, 1993). Initially, the PCs of SSPE may be somewhat asymmetric or occur irregularly before evolving into a regular repetition rate (Miller and Westmoreland, 1983). Out of the 31 patients with proved SSPE studied by Markand and Panszi (1975), pronounced asymmetry of the PCs was noted in only 3 patients. Of these, two had PCs higher in amplitude over the left hemisphere associated with myoclonic jerks of the right side of the body. However, the anatomo-pathological changes which could be ascribed to this phenomenon were not explored. Rarely, the PCs were reported to be entirely focal (Markand and Panszi, 1975). The EEG pattern of periodic lateralized epileptiform discharges (PLEDs) may superficially resemble EEG findings as seen in our patient. PLEDs consist of unilateral, high amplitude sharp waves or spikes that occur with a more or less regular periodicity, usually once in 1 or 2 s (Chatrian et al., 1964; Reiher et al., 1991). PLEDs occur in the setting of an acute focal cerebral hemispheric insult such as an infarct or encephalitis and the EEG complexes are either focal or lateralized, and regardless of the course of the disease process, they spontaneously disappear in a
B. Santoshkumar, K. Radhakrishnan / Electroencephalography and clinical Neurophysiology 99 (1996) 440-443
few days or weeks (Chatrian et al., '1964; Reiher et al., 1991). However, occasitonally PLEDs can be chronic and can persist for several months or years (Westmoreland et al., 1986). The differentiation of PLEDs from the type of periodicity seen in our patient is therefore arbitrary. However, the major difference in our patient is that the PLEDs occurred over the normal hemisphere as shown by the MRI, thereby indicating a projected electrical disturbance. There is no satisfactory model to explain the pathogenesis of generalized periodic discharges. Four hypotheses concerning the origin of the PCs in SSPE have been proposed: (1) deep thalarnic or mesencephalic-reticular origin, associated with relative integrity of the cortex and thalamo-cortical pathways (Cobb, 1966; Lombroso, 1968); (2) origin from cortex isolated from subcortical structures (Lesse et al., 1958; Strom van Leeuwen, 1964); (3) involvement of both grey and white matter resulting in a disturbance of the normal cortico-subcortical electrical interaction (Gloor et al., 1968); and (4) a diffuse disturbance of the time constant of recovery of an electrochemical process at the cellular level (Cobb, 1979). The absence of the PCs over the side of long-standing cerebral hemispheric damage as observed in our patient shows that a fairly functional cortex and subcortical white matter are needed for the expression of generalized PCs of SSPE. References Chatrian, G.E., Shaw, C.M. and Leffman, H. The significance of periodic epileptiform discharges in EEG: an electrographic, clinical and pathological study. Electroenceph. clin. Neurophysiol., 1964, 17: 177-193. Cobb, W.A. The periodic ew,~ntsof subacute sclerosing leucoencephalitis. Electroenceph. clin. Neurophysiol., 1966, 21: 278-294. Cobb, W.A. Evidence on the periodic mechanism in herpes simplex encephalitis. Electroenceph. clin. Neurophysiol., 1979, 46: 345-350. Dyken, P.R. Subacute sclerosing panencephalitis. Neurol. Clin., 1985, 3: 179-195. Farrel, D.F., Starr, A. and Freeman, J.M. The effect of body temperature
443
on the 'periodic complexes' of subacute sclerosing panencephalitis (SSPE). Electroenceph. clin. Neurophysiol., 1971, 30: 415-421. Gim6nez-Rold,fm, S., Mar6n, M., Mateo, D. and Lopez-Fraile, I.P. Preclinical EEG abnormalities in subacute sclerosing panencephalitis. Neurology, 1981, 31: 763-767. Gloor, P., Kalabay, O. and Giard, N. The electroencephalogram in diffuse encephalopathies: electroencephalographic correlates of grey and white matter lesions. Brain, 1968, 91: 779-802. Lesse, S., Hoefer, P.F.A. and Austin, J.H. The electroencephalogram in diffuse encephalopathies. Arch. Neurol. Psychiatry, 1958, 79: 359375. Lombroso, C.T. Remarks on the EEG and movement disorder in SSPE. Neurology, 1968, 18 (2): 69-75. Markand, O.N. and Panszi, J.G. The electroencephalogram in subacute sclerosing panencephalitis. Arch. Neurol., 1975, 32: 719-726. Martinovi6, ~. Periodic generalized bursts of fast waves in subacute sclerosing panencephalitis. Electroenceph. clin. Neurophysiol., 1986, 63: 236-238. Miller, C.R. and Westmoreland, B.F. The EEG in slow virus diseases. Am. J. EEG Technol., 1983, 23: 209-217. Reiher, J., Lapointe, L.R. and Lessard, L. Prolonged and variable intervals between EEG complexes in subacute inclusion body encephalitis. Can. Med. Assoc. J., 1973, 108: 729-732. Reiher, J., Rivest, J., Grand'Malson, F. and Leduc, C. Periodic lateralised epileptiform discharges with transitional rhythmic discharges: association with seizures. Electroenceph. clin. Neurophysiol., 1991, 78: 1217. Strom van Leeuwen, W. Electroencephalographical and neurophysiological aspects of subacute sclerosing leuco-encephalitis. Psychiatr. Neurol. Neurochir., 1964, 67: 312-322. Westmoreland, B.F. The EEG in cerebral inflammatory processes. In: E. Niedermeyer and F. Lopes Da Silva (Eds.), Electroencephalography: Basic Principles, Clinical Applications, and Related Fields, 3rd edn. Williams and Wilkins, Baltimore, 1993, pp. 291-304. Westmoreland, B.F., Gomez, M.R. and Blume, W.T. Activation of periodic complexes of subacute sclerosing panencephalitis by sleep. Ann. Neurol., 1977, 1: 185-187. Westmoreland, B.F., Sharbrough, F.W. and Donat, J.R. Stimulusinduced EEG complexes and motor spasms in subacute sclerosing panencephalitis. Neurology, 1979, 29:1154-57. Westmoreland, B.F., Klass, D.W. and Sharbrough, F.W. Chronic periodic lateralized epileptiform discharges. Arch. Neurol., 1986, 43: 494-496.