Atypical EEG findings in subacute sclerosing panencephalitis
Introduction
Subacute sclerosing panencephalitis (SSPE) is a progressive and usually fatal degenerative disease of the central nervous system caused by a mutant measles virus. A defect in measles virus replication and abnormal immune response may play a role in pathogenesis (Dyken, 1985, Dyken, 2001, Garg, 2002). It affects children of different ages and young adults. Clinical symptoms usually occur years after acute measles. The main clinical symptoms are cognitive decline and stereotyped myoclonic jerks. Other neurological symptoms such as pyramidal, extrapyramidal, visual, cerebellar and autonomic symptoms, seizures and coma, develop later. The course is usually progressive, however, some patients have transient remission. In the late stage, patients usually die of intercurrent infections. Diagnosis is not difficult with typical clinical, electroencephalographic (EEG) and cerebrospinal fluid (CSF) findings. The classic EEG pattern in SSPE consists of periodic, generalized, bilaterally synchronous and symmetrical high amplitude slow waves (Blume and Kibara, 1999). However, several atypical EEG findings in SSPE have been reported (Dogulu et al., 1995, Markand and Panszi, 1975, Martinovic, 1986, Tung et al., 1997, Yohsikawa et al., 1990).
This study aimed to investigate electroencepalographic features in SSPE and to detect any variation.
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Materials and method
Subjects in this study consisted of 22 patients (8 girls and 14 boys) with SSPE, aged 2–17 years (mean 9.4 years) examined in the period 1990–2003. The age at onset of SSPE ranged from 2 to 17 years. Their clinical data and EEG records were reviewed retrospectively. All the patients had CSF examination, CSF and serum measles antibodies, CT or MRI. The diagnosis was based on clinical features, abnormal EEG and elevated titers of antibody in CSF. The clinical staging was according to the criteria
Results
Fifty-six EEG records from 22 patients were reviewed. EEG revealed the presence of periodic complexes. The patients were divided into two groups according to EEG findings. Group I consisted of 13 patients, all of which showed classical periodic discharges in 27 EEG records. Group II consisted of nine patients, all of which showed different atypical EEG patterns in 29 EEG records. There were no changes between repeated EEG measurements. The demographic and clinical features of the patients are
Discussion
The characteristic periodic complexes (PCs) in SSPE consist of stereotyped, bilaterally synchronous and symmetrical 100–1000 μV, 1–3 Hz waves, sometimes with intermingled spikes or sharp waves. Their duration ranges from 1 to 3 s and the interval between complexes varies from 2 to 20 s, but in the early stages these complexes may recur as frequently as every 5 min. These PCs may be present only during sleep and may be elicited by afferent stimuli in the early stages. The complexes are usually
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