Atypical EEG findings in subacute sclerosing panencephalitis

Expanding the Spectrum of EEG Periodic Discharges in Subacute Sclerosing Panencephalitis: A Case Report

Background Atypical electroencephalogram (EEG) abnormalities emerge in patients with subacute sclerosing panencephalitis (SSPE), especially in cases with an atypical clinical presentation that can lead to diagnostic difficulties.

Case Report In this article, we presented a case of SSPE with an atypical onset with epileptic seizures and Parkinson's features. The neurological examination during the initial evaluation of the patient showed extrapyramidal syndrome, hyperreflexia, intention tremor, and dysmetria. Cranial magnetic resonance imaging was normal. Video EEGs were performed in wakefulness and sleep. In wakefulness, multiple brief seizures (1–1.5 seconds were recorded, consisting of gradual bending of the body forward and to the right that lacked the sudden characteristic of myoclonia. During those episodes, we recorded generalized epileptiform activity of 4 or 5 sharp waves, with higher amplitude in the anterior regions, in some of the paroxysms superimposed on a slow wave or followed by a high amplitude slow wave. The paroxysms appeared periodically every 15 to 30 seconds. However, 2 months later, the EEG showed typical periodic generalized activity of biphasic/triphasic slow waves (Radermecker complexes), accompanied by myoclonias.

Conclusion We reported a peculiar EEG pattern in a patient with SSPE that consists of periodic generalized activity of sharp waves. Atypical EEG patterns can appear when the disease progresses, but initially too, before typical periodic complexes and can complicate the diagnostic process.

Atypical Pediatric Demyelinating Diseases of the Central Nervous System

PURPOSE OF REVIEW

Pediatric central nervous system demyelinating diseases include multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and acute disseminated encephalomyelitis (ADEM). As diagnostic criteria become more inclusive, the risk of misdiagnosis of atypical demyelinating diseases of rheumatologic, infectious, and autoimmune etiology increases.

RECENT FINDINGS

We review mimics of multiple sclerosis, neuromyelitis optica spectrum disorder, and acute disseminated encephalomyelitis, including rheumatologic diseases: systemic lupus erythematosus and neuro-Behçet disease; infectious diseases: human immunodeficiency virus, progressive multifocal leukoencephalopathy, and subacute sclerosis panencephalitis; and autoimmune diseases including X-linked Charcot-Marie-Tooth disease, chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) and autoimmune glial fibrillary acidic protein (GFAP) encephalopathy. Atypical demyelinating disease may mimic classic neuroinflammatory diseases of the central nervous system. Imaging may meet criteria for a diagnosis of multiple sclerosis, or patients may present with optic neuritis and transverse myelitis consistent with neuromyelitis optica spectrum or myelin oligodendrocyte glycoprotein (MOG) antibody disorders. Through careful history-taking and review of atypical MRI findings, we may avoid misdiagnosis and mistreatment.

Subacute Sclerosing Panencephalitis Presenting with Unilateral Periodic Myoclonic Jerks

Background:

Subacute sclerosing panencephalitis (SSPE) is a rare complication of measles virus infection. The disease is characterized by behavioural abnormalities, intellectual deterioration, motor weakness, and generalized myoclonic jerks progressing to coma and death in one to two years in 80% of the cases. The myoclonic jerks are associated with characteristic generalized slow periodic complexes on electroencephalography (EEG). The symptoms and signs of SSPE are frequently quite variable. The clinical course is equally variable and difficult to predict. The characteristic periodic myoclonus can rarely occur unilaterally particularly in the early stages of the disease. As well, the periodic EEG complexes have been reported unilaterally in up to 3% of cases.

Case Report:

A 12-year-old boy, who was seen at a later stage with atypical manifestation of myoclonic body jerks confined entirely unilaterally, combined with contralateral periodic EEG complexes. One could assume clinically that the more diseased hemisphere was responsible for generating the jerks. However, brain magnetic resonance imaging revealed asymmetric hemispheric changes suggesting that the less neurologically damaged hemisphere is responsible for generating the unilateral myoclonic jerks. This has led to the interpretation that the more severely damaged hemisphere has lost the neuronal connectivity required to generate these periodic myoclonic jerks.

Conclusion:

Subacute sclerosing panencephalitis may have asymmetric hemispheric involvement, not only early, but also in the advanced stages of the disease, which can result in unilateral periodic myoclonic jerks.

Nonconvulsive status epilepticus on electroencephalography in a case with subacute sclerosing panencephalitis

Subacute sclerosing panencephalitis is a neurodegenerative disease with a poor prognosis. We report a case of a 5 1/2-year-old boy who had emotional lability, cognitive difficulties, and myoclonia after a mild closed head injury. The magnetic resonance image of the brain and computed tomographic scan of the head were normal. His electroencephalogram (EEG) showed continuous nonconvulsive status epilepticus activity, which could not be suppressed with intravenous diazepam. After treatment with phenytoin for 2 days, an EEG showed periodic high-amplitude sharp-and-slow-wave complexes, which were also not suppressed with intravenous diazepam. Since the patient had measles at 5 months of age, subacute sclerosing panencephalitis was considered, and the diagnosis was confirmed by the presence of measles antibodies in cerebrospinal fluid.

Early Detection of Subacute Sclerosing Panencephalitis by High b-Value Diffusion-Weighted Imaging

The authors report a case of subacute sclerosing panencephalitis in which the diagnosis was suggested by high b-value diffusion-weighted imaging (DWI) findings. The signal abnormalities were located asymmetrically at bilateral cerebral corticosubcortical regions. High b-value DWI showed these signal abnormalities as marked hyperintensity with decreased apparent diffusion coefficient values. The signal abnormalities were difficult to identify on other magnetic resonance imaging sequences, including routine DWI. High b-value DWI could be valuable for earlier detection of subacute sclerosing panencephalitis.

Atypical EEG findings in subacute sclerosing panencephalitis

OBJECTIVE

To evaluate atypical electroencephalographic features in subacute sclerosing panencephalitis (SSPE) and to detect its relation to clinical features.

METHODS

Twenty-two patients aged 2-17 years (mean 9.4 years) with definite diagnosis of SSPE were studied. Their clinical data and EEG records were reviewed retrospectively. All EEG records were analysed for features of periodic complexes (PCs) in relation to age, age at onset, clinical stage and the rate of progression as well as duration of the disease.

RESULTS

Classical periodic complexes of SSPE were found in EEGs of 13 patients (group I). Atypical patterns were observed in EEGs of nine patients (group II). Two new atypical findings were identified: prolonged discharges which include sharp waves and slow waves for 4-7 s followed by suppression for 1-4s; and periodic complexes which consist of four or five sharp waves in every 2 s. We observed atypical EEG patterns were more frequently in Stage III, acute form, and the disease duration was longer than in the typical group.

CONCLUSIONS

Atypical EEG patterns in SSPE might be related to the progression of the disease, but this theory needs further longitudinal studies.

SIGNIFICANCE

We suggest atypical EEG patterns might be observed more frequently in patients with severe neurologic disability, more rapidly progressive disease and longer duration of disease.

A case of subacute sclerosing panencephalitis preceded by epileptic seizures: evolutional EEG changes

We reported a patient with subacute sclerosing panencephalitis (SSPE) in whom EEG had been serially performed before the onset. She was referred to our hospital due to epileptic seizures at 2 years of age. Focal spikes were seen on EEG at the time of her first seizure (2 years 4 months). At the time of the second unprovoked seizure (9 years 8 months), EEG showed poorly organized background activity associated with focal spikes and a few diffuse spike-and-waves. Then, diffuse paroxysms became predominant, followed by periodic synchronous discharges. In our case, EEG abnormalities were recognized before mental deterioration. Unexpected EEG changes in a patient with epilepsy could be a clue as to the diagnosis of SSPE.

Clinical presentation of subacute sclerosing panencephalitis in Papua New Guinea

Eighty-three children presented at Goroka Base Hospital in the Eastern Highlands Province (EHP) of Papua New Guinea over a period of 3 years and 9 months between February 1997 and November 2000 were confirmed to have subacute sclerosing panencephalitis (SSPE). Confirmation of the diagnosis was based on the demonstration of high titres of measles antibodies in the cerebrospinal fluid and/or serum in association with clinical features supportive of SSPE, including characteristic electroencephalographic changes and amplification of measles virus genome by reverse transcriptase polymerase chain reaction in some cases. The mean cerebrospinal fluid and serum enzyme immunoassay antibody levels among the SSPE patients were 38 250 and 860 580, respectively. The mean age of onset of SSPE was 7.9 +/- 2.6 years and ranged between 2 and 14 years. The overall male to female ratio was 1.2:1 and 1.4:1 for EHP.

Correlation between clinical stages and EEG findings of subacute sclerosing panencephalitis

In this retrospective study 67 patients with SSPE seen between the years 1980 and 1998 were reviewed. Using the criteria of SSPE diagnosis (clinical signs, characteristic EEG patterns, high titres of measles antibodies in the serum and CSF), the patients were divided into two groups. Group A fulfilled all criteria, however, due to the inability of measuring measles antibody before 1987, it was not possible to observe the third criterion in Group B. Among 67 patients, groups A and B consisted of 51 boys and 16 girls ranging in age between 1 to 23 years, mean age 13.1. The male/female ratio was 3.1. The periodic EEG complexes (PCs) were usually bilateral, synchronous and symmetrical. PC amplitude asymmetry was seen in 12 patients and 2 patients had no PC synchronization between the hemispheres. Six patients had more than one form of PC. Delta activity in anterior hemispheres after PC was seen in 40 patients, mostly in stage 2A. Thirty-two patients had focal epileptiform abnormalities in multiple locations at every stage but most frequently in frontal, central and temporal regions. One patient had PC over both hemispheres and periodic lateralized epileptiform discharges (PLEDs) over the right hemisphere. The EEG findings described and observed in our study do not seem to be specific to SSPE but these findings were not atypical or unusual.

Electroencephalogram in developmental delay: specific electroclinical syndromes

The electroencephalogram (EEG) plays an important role in the evaluation of a child with developmental delay. An EEG is often required to classify seizures in children with developmental delay. Equally important is the role of the EEG in the identification of specific electroclinical syndromes in children who may or may not manifest seizures. Specific electroclinical syndromes include the acquired epileptiform aphasia syndrome, Landau-Kleffner syndrome, and electrical status epilepticus during slow wave sleep. Other clinical situations where the EEG offers diagnostic and prognostic information, such as subacute sclerosing encephalitis, progressive myoclonus epilepsies, Rett syndrome, and Lennox Gastaut syndrome are also discussed.

Acute fulminant SSPE: clinical and EEG features

We report an autopsy-proven case of SSPE in which the course was rapidly progressive, leading to death in 2 months. The patient was admitted for investigation of visual symptoms. His examination revealed complete right homonymous hemianopia and myoclonic jerks in the right half of the body. EEG showed high voltage periodic slow-wave discharges that were often associated with jerks. Measles antibody was positive in serum and CSF. MRI showed hyperintensity in the white matter of the occipital poles. The patient became completely blind and had jerks in all four limbs. His condition continued to deteriorate and within 3 weeks he reached a state of deep coma. The myoclonic jerks became less marked and gradually completely ceased. The EEG showed diffuse slow activity without periodic complexes. The patient died approximately 2 months from onset of disease. Brain autopsy revealed severe neuronal loss with abundant inclusion bodies in the remaining neuronal and oligodendroglial nuclei, which was compatible with SSPE.