Electroencephalography and clinical Neurophysiology, 1991, 78:311-313 © 1991 Elsevier Scientific Publishers Ireland, Ltd. 0013-4649/91/$03.50 ADONIS 001346499100085V

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EEG 90166

Short c o m m u n i c a t i o n

Atypical electr~encephalographic pattern in a patient Mth subacute sclerosing panencephalitis Gregory B. Sharp, S. Mark Laney, Barbara F. Westmoreland and Robert V. Groover Section of Pediatric Neurology and Section of Electroencephalography, Mayo Clinic and Mayo Foundation, Rochester, MN 55905 (U.S.A.) (Accepted for publication: 18 November 1990)

Summm-y Subacute sclerosing panencephalitis (SSPE) has become rare since the widespread use of the measles vaccine. In this patient with a 5 month history of seizures and progressive dementia due to SSPE, the atypical electroencephalographic pattern was characterized by generalized spike-and-wave discharges, maximal on the right, associated with clinical seizures. After diazepam (intravenously), more typical periodic complexes appeared.

Key words: Subacute sclerosing panencephalitis; Electroencephalography; Spike and wave discharges; Periodic complexes

Subacute sclerosing panencephalitis (SSPE) is now known to be an encephalitic condition due to infection of the central nervous system with measles (rubeola) virus (Jubelt and Miller 1989). The primary infection typically occurs in early childhood with a clinical or subclinical measles infection. The affected patient usually shows signs and symptoms of SSPE during the latter part of the first decade of life or in adolescence. The course is progressive over months to years and usually results in death. The most prominent symptoms include progressive dementia, myoclonic jerks, motor abnormalities, ataxia, and seizures (Radermecker 1977). Chorioretinitis and associated visual disturbances may occur. The diagnosis is based on the characteristic clinical and electroencephalographic (EEG) findings and characteristic findings in the cerebrospinal fluid (CSF) which consist of increased measles antibody titer and a marked increase in gammaglobulin fraction (Radermecker 1977; Dhib-Jalbut et al. 1981). Radermecker (1949) and Cobb and Hill (1950) first described the characteristic EEG pattern consisting of high-voltage periodic sharpand-slow-wave complexes that are often associated with motor spasms. In the case reported here, the patient presented with atypical EEG findings, making the diagnosis more difficult.

Report of case A 15-year-old boy from Karachi, Pakistan, had a seizure, 5 months before being seen at the Mayo Clinic, that was characterized by jerking of one side of his body and loss of consciousness. Several days later he began having episodes of failing to the ground. Despite treatment with anticonvulsants, the number of seizures increased and were characterized by tonic stiffening, staring, and shaking of his left hand and arm. Six weeks prior to being seen at the Mayo Clinic, the patient was having, seizures every 5-10 rain. Also, progressive cognitive and intellectual deterioration, gait ataxia, decreased visual awareness, loss of recent memory, and deterioration of speech had developed. The patient was seen at several medical institutions in Europe and America.

Correspondence to: Barbara F. Westmoreland, M.D., Mayo Clinic, 200 First Street SW, Rochester, MN 55905 (U,S.A.).

Because the diagnosis was not clear, he was referred to the Mayo Clinic for further evaluation. On examination, we found him to be a demented young man with decreased recent memory and confusion as to time and place. He had diffuse hyperreflexia with a Babinski response on the left and an equivocal response on the right. He had a bilateral intention tremor with periodic myoclonus-like jerks. The funduscopic examination showed no evidence of retinal lesions. The CSF protein concentration was increased (47 mg/dl) with immunoglobulin at 13.7 mg/dl (representing 29% of the total protein); there were 3 oligoclonal bands in the CSF and 2 in the serum. The serum measles titer was strikingly high (IgG at 1:10,240). The CSF measles titer was 1 : 160. Magnetic resonance imaging of the head showed abnormalities in the white matter of the posterior cerebral hemispheres consistent with a demyelinating process. Brain-stem auditory evoked responses were within normal limits.

EEG findings Recordings made at the onset of the disease process and at I and 2 months later showed widely distributed spike-and-wave discharges with a frequency of 2-2.5 Hz and maximal on the fight. On occasion, some nodding of the patient's head was observed in association with the spike-and-wave bursts. There also was diffuse slowing of the background, Two EEGs made at the Mayo Clinic showed diffuse slowing with frequent trains of 2-2.5 Hz spike-and-wave discharges that were maximal over the right frontocentral region (Fig. 1). The spike-andwave discharges ranged from 3 to 35 sec in duration and occurred every 10-50 sec with 3-10 see between the bursts (Fig. 2). The spike-and-wave discharges often were followed by a train of rhythmic slow-wave activity over the right hemisphere. Associated with the spike-and-wave bursts were jerking movements of the left upper extremity and face and eye movements. When the patient held his hands out, they would drop during the spike-and-wave bursts. Also, he would fall backward during the bursts. A sleep recording showed frequent trains of spike-and-wave discharges that lasted up to 70 sec and during which the patient had jerking movements of his left face

312

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and arm. No distinguishable sleep activity was present during the sleep recording. A repeat tracing 1 day later showed similar findings. When 10 mg of diazepam was given intravenously during the recording, there was a decrease in the spike-and-wave discharges and quasiperiodic sharp-and-slow-wave complexes became apparent, occurring every 7-10 sec (Fig. 3). Later, the spike-and-wave discharges returned, replacing the quasiperiodic complexes.

Panszi 1975). The patient described here was referred because of frequent seizures with EEGs that were dominated by spike-and-wave discharges. Although epileptiform abnormalities have been observed in SSPE, spike-and-wave bursts are relatively uncommon in patients with SSPE (Lombroso 1968; Broughton et al. 1972; Markand and Panszi 1975; Westmoreland et al. 1976). The pathophysiology of spike-and-wave discharges in SSPE is unclear, however. This may, in part, reflect involvement of cortical and subcortical neurons (Markand and Panszi 1975). In rare instances, the typical pattern of periodic complexes of SSPE may be seen during a sleep recording or after an injection of diazepam (Lombroso 1968; Westmoreland et al. 1976). In this patient, the characteristic periodic EEG pattern was not apparent during the routine awake and sleep recordings, but after an intravenous injection of diazepam the periodic complexes became apparent. This may have

Discussion

One of the diagnostic features of SSPE is the characteristic EEG pattern consisting of periodic complexes usually occurring every 4-15 sec (Cobb 1966). However, on occasion the EEG may be less typical and thus present a problem in making the diagnosis (Markand and

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ATYPICAL EEG IN SSPE

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been related in part to a transient suppression of the spike-and-wave bursts, which allowed the more characteristic sharp-and-slow-wave complexes to be seen, or there may have been an activating effect of diazepam itself. The atypical presentation of seizures and spike-and-wave discharges in this patient made the diagnosis difficult. This case illustrates the usefulness of a pharmacologic agent, diazepam, in bringing out the more typical EEG pattern. Although SSPE has been seen less frequently in countries in which the measles vaccine is used, it still is seen in other countries and one should be aware of the atypical presentation, both clinically and electrographically, that can occur with this entity.

References

Broughton, R., Nelson, R., Gloor, P. and Andermann, F. Petit mal epilepsy evolving to subacute sclerosing panencephalitis (abstract). Electroenceph. din. Neurophysiol., 1972, 33: 352. Cobb, W. The periodic events of subacute sclerosing leucoencephalitis. Electroenceph. din. Neurophysiol., 1966, 21: 278-294. Cobb, W. and Hill, D. Electroencephalogram in subacute progressive encephalitis. Brain, 1950, 73: 392-404.

Dhib-Jalbut, S.S., Abdelnoor, A.M. and Haddad, F.S. Cellular and humoral immunity in subacute sclerosing panenoephalitis. Infect. Immun., 1981, 33: 34-42. Jubelt, B. and Miller, J.R. Viral infections. In: L.P. Rowland (Ed.), Merritt's Textbook of Neurology, 8th Edn. Lea and Febiger, Philadelphia, PA, 1989: 96-137. Lombroso, C.T. Remarks on the EEG and movement disorder in SSPE. Neurology, 1968, 18: 69-75. Markand, O.N. and Panszi, J.G. The electroer~cephalogram in subacute sclerosing panencephalitis. Arch. Neurol., 1975, 32: 719-726. Radermecker, F.J. Infections and inflammatory reactions, allergy and allergic reactions; degenerative diseases. In: A. R6mond (Ed.), Handbook of Electroencephalography and Clinical Neurophysiology, Vol. 15, Part A. Elsevier Scientific Publishers, Amsterdam, 1977: 28-35. Radermecker, J. Aspects 61ectroenc£-phalographiques dans trois cas d'encZ~phalite subalgu6. Acta Neurol. Psychiat. Belg., 1949, 49: 222-232. Westmoreland, B.F., Blume, W.T. and Gomez, M.R. Generalized sharp and slow wave and electrodecremental seizure pattern in subacute sclerosing panencephalitis. Mayo Clin. Proc., 1976, 51: 107-111.