Atypical clinical and electroencephalographic pattern in a patient with subacute sclerosing panencephalitis

Abstract

SUMMARY -We describe an atypical clinical and electroencephalographic (EEG) pattern observed during the course of subacute sclerosing panencephalitis in a 14 year-old boy. In this patient with a two weeks history of partial complex seizures, the atypical EEG pattern was characterized by an initial left temporal focus which evolved to periodic lateralized epileptiform discharges (PLEDs) and, only during the 3 rd and 4 th weeks the typical bilateral and generalized periodic complexes appeared.KEY WORDS: subacute sclerosing panencephalitis, EEG, periodic complexes, partial complex seizure.Since the early reports of Radermecker (1949) 12 and Cobb and Hill (1950) 2 , the great diagnostic value of electroencephalographic (EEG) findings in subacute sclerosing panencephalitis (SSPE) has been outlined by numerous workers. As is well known, the characteristic EEG pattern consists of high-voltage and polymorphic periodic complexes, recurring at long intervals, grossly widespread throughout both hemispheres 3 that are often associated with motor spasms.In the case reported here, the patient presented partial complex seizures and an atypical EEG finding, making the diagnosis more difficult. We are aware of only one study of SSPE with partial complex seizures 9 . REPORT OF CASEHJ, a 14-year-old boy had partial complex seizures two weeks before being seen at the Escola Paulista de Medicina, that were characterized by loss of consciousness, staring, verbal and gestual automatisms, several times per day. Also, cognitive and intellectual deterioration had developed. A diagnosis of partial complex seizures and behavioural disturbance were made. Despite treatment with anticonvulsants (carbamazepine) the * Head of the EEG Sector, Escola Paulista de Medicina (EPM); **Junior Doctor of the EEG Sector; ***Resident in Neurology; ****Full Professor and Head of the Discipline of Neurology, EPM. Aceite: 2-janeiro-1995.Dr. Délrio Façanha da Silva -Disciplina de Neurologia, Setor de Eletrencefalografia, Escola Paulista de MedicinaPadrão clínico e eletrencefalográfico atípico em um paciente com panencefalite esclerosante subaguda RESUMO -Descrevemos o quadro clínico e eletrencefalográfico atípicos observados durante a evolução de panencefalite esclerosante subaguda, em um menino de 14 anos. Neste paciente, com história de crises parciais complexas há duas semanas, o padrão eletrencefalográfico atípico foi caracterizado por foco temporal esquerdo que evoluiu para "periodic lateralized epileptiform discharges" (PLEDs), somente durante a 3 a e 4 a semanas surgindo os clássicos complexos periódicos difusos. PALAVRAS-CHAVE: panencefalite esclerosante subaguda, EEG, complexos periódicos, crise parcial complexa.

Subacute Sclerosing Panencephalitis Presenting with Unilateral Periodic Myoclonic Jerks

“…9,10 The characteristic periodic myoclonus has been reported unilaterally, particularly in the early stages of the disease. 11,12 The EEG complexes consist of high voltage (300-1500 µV) polyphasic sharp and slow wave complexes lasting 0.5 to 3 seconds in duration and recurring in a periodic fashion every 3 to 12 seconds. 5 These periodic complexes are constant and stereotyped in a single recording but may vary from patient to patient, or within the same patient at different stages of the disease.…”

Periodic EEG patterns: importance of their recognition and clinical significance

“…They are more specific with respect to the etiology and may be encountered in disorders like some toxic encephalopathies ( for baclofen or ketamine, for example), anoxic brain injury and SSPE 3 . In SSPE (suggested by the presence of PLIDDs in a child with dementia and myoclonic jerks), the stereotyped complexes, occurring at a regular interval and having a constant relationship to myoclonus, make this as one of the most characteristic and disease-specific of all EEG patterns 34,[48][49][50][51] . The early descriptions, by Cobb 48 , in 1966, characterized the stage II of SSPE by bilaterally symmetrical and synchronous generalized, stereotyped high amplitude delta waves, called Radermacker or "R" complexes, recurring at regular intervals of 5 to 15 seconds, although less specific and atypical EEG changes have been described 49 .…”

“…With advancing disease, the interval between the discharges becomes progressively smaller 2,49 . Silva et al 51 described an atypical clinical and EEG pattern in a 14-yearold boy with SSPE, who presented an initial EEG characterized by a left temporal focus which evolved to PLEDs. Typical GPEDs appeared during the 3 rd and 4 th weeks.…”

Periodic Lateralized Epileptiform Discharges in Fulminant Form of SSPE

“…Several atypical changes have been described which include asymmetric periodic complexes 2 ; frontal rhythmic delta activity; electrodecremental periods following EEG complexes; diffuse sharp waves and sharp-and-slow-wave complexes over frontal regions; and focal abnormalities, such as sharp wave and sharp and slow wave foci. 3 Combination of SSPE and PLEDs have been reported earlier, though rarely [4][5][6] . The electrical evolution in our patient was dissimilar and evolved from GPC to PLEDs over a period of three weeks but there were no clinical seizures through out the course of the illness as is expected in acute PLEDs 7 .…”