Periodic lateralized epileptiform discharges in influenza B-associated encephalopathy

Lateralized Periodic Discharges: A Literature Review

The purpose of this article is to provide a comprehensive review of the literature about a particular EEG pattern, lateralized periodic discharges (LPDs), or periodic lateralized epileptiform discharges (PLEDs). The review will discuss the history and terminology of LPDs and provide a detailed summary of the etiologies, pathophysiology, clinical symptoms, and imaging studies related to LPDs. Current controversies about the association of LPDs with seizures and their management will be reviewed. Finally, some unanswered questions and suggestions for future research on LPDs will be discussed.

Previously diagnosed influenza infections and the risk of developing epilepsy

Several epidemiological studies suggest a possible involvement of viral infection in the development of epilepsy. While recent research from in vitro studies increasingly supports the role of herpes simplex virus type 1 (HSV-1) in the pathogenesis of epilepsy, little is known about the role of other viral infections such as influenza. Using data from the Clinical Practice Research Datalink (CPRD), we conducted a matched case-control analysis to assess the association between GP-diagnosed influenza infections and the risk of developing an incident diagnosis of epilepsy. During the study period 11 244 incident epilepsy cases and 44 976 matched control patients were identified. Prior exposure to influenza was reported in 7·5% of epilepsy cases and 6·7% of controls [adjusted odds ratio (aOR) 1·12, 95% confidence interval (CI) 1·03-1·22]. Prior history of 'complicated influenza', i.e. influenza associated with a possible super-infection, was associated with a slightly increased epilepsy risk (aOR 1·64, 95% CI 1·10-2·46), particularly if recorded within the 2 months preceding the epilepsy diagnosis (aOR 6·03, 95% CI 1·10-33·2). Our findings suggest that prior influenza exposure does not appear to materially alter the risk of developing epilepsy. By contrast, influenza episodes accompanied by complications were associated with a slightly increased epilepsy risk.

Periodic lateralized epileptiform discharges as manifestation of pneumococcal meningoencephalitis

Periodic Lateralized Epileptiform Discharges (PLEDs) are usually seen in the context of destructive structural lesions of the cortex, more frequently in acute ischemic stroke and less common in tumours and meningoencephalitis, specially herpes simplex virus. Its origin and prognosis are uncertain but it is known that PLEDs are linked to epilectic seizures, including status epilepticus.

We report on a 75-year old woman with pneumococcal meningoencephalitis who presented altered level of consciousness, acute focal deficits, convulsive seizures and PLEDs in left hemisphere. The finding of PLEDs on the electroencephalogram is related to focal lesions of heterogeneous origin, which up to date, have not been documented in pneumococcal infections of the central nervous system. Our case highlights the importance of identifying and addressing any modifiable etiologic factors of PLEDs.

Influenza virus and CNS manifestations

Neurological involvement during influenza infection has been described during epidemics and is often consistent with serious sequelae or death. An increasing incidence of influenza-associated encephalitis/encephalopathy has been reported in Japan, mainly in children. A variety of other clinical CNS manifestations, such as Reye's syndrome, acute necrotising encephalopathy (ANE), and myelitis as well as autoimmune conditions, such as Guillain-Barre's syndrome, may occur during the course of influenza infection. Virological diagnosis is essential and based on virus isolation, antigen detection, RNA detection by PCR, and serological analyses. Neuroimaging with CT and MRI of the brain are of prognostic value. The pathogenic mechanisms behind the influenza CNS complications are unknown. The treatment is symptomatic, with control of vital functions in the intensive care unit, antiepileptic medication and treatment against brain oedema.

Panic Attack Symptoms in a Patient with Left Temporal Lobe Epilepsy

We describe a 56-year-old woman with left temporal lobe epilepsy who developed symptoms of a panic attack. Owing to normal electroencephalography and brain magnetic resonance imaging results, she was initially diagnosed as suffering from panic attacks and treated for anxiety neurosis. The symptoms persisted and she was re-examined in our department. An interictal electroencephalogram showed paroxysmal spike waves in the left mesial temporal lobe region and this was the basis for a diagnosis of left temporal lobe epilepsy. This report suggests that left temporal lobe epilepsy should be considered as the differential diagnosis when patients frequently complain of fear or anxiety.

Periodic lateralized epileptiform discharges in children

Thirteen children in whom electroencephalography revealed periodic lateralized epileptiform discharges in the acute phase of cerebral involvement were included in this study. Four were diagnosed as having influenza-associated encephalopathy, two nonherpetic limbic encephalitis, two theophylline-associated seizures, one Mycoplasma pneumoniae encephalitis, one acute encephalopathy, and one bacterial meningitis. All patients developed seizures; six developed hemiconvulsions. As to prognosis, two died, six had some neurologic sequelae, and five had no neurologic sequelae. Although periodic lateralized epileptiform discharges are not disease specific, the importance of these disorders had not been focused on as a cause of periodic lateralized epileptiform discharges.

Encephalitis associated with influenza B virus infection in 2 children and a review of the literature

Two children with influenza B-associated encephalitis (IBAE) presented to our hospital during the winter of 2000-2001, both of whom had cases notable for mutism in association with encephalitis. A review of the literature identified 13 additional reports consistent with IBAE that contained sufficient data for analysis. Eleven of 15 reported cases occurred in children aged <or=18 years; of these, more than one-half occurred in children <11 years of age. Neurologic symptoms appeared within the first 4 days of illness in 13 cases. Speech abnormalities were observed in 4 patients and consisted of mutism in 3. Although the majority of patients recovered fully, 3 were left with neurologic sequelae, and 1 died. These cases reveal the spectrum of IBAE and its potential for long-term sequelae. Clinicians caring for children should remain vigilant for this rare complication of influenza B virus infection.