Characteristics of generalised epileptiform activity

OBJECTIVE

To study the age-related occurrence of specific features of generalised epileptiform activity (GEA), their correlation with EEG background activity (BA), and their internal correlation.

METHODS

17,723 consecutive routine EEGs from 12,511 patients were annotated and categorised into a database. The first EEG containing GEA from all 325 patients with such activity were selected and categorised for GEA features. The BA was studied in multivariable fractional polynomial regression models including intervening variables. The GEA features were studied in similar models for age-dependency and internal correlation.

RESULTS

High GEA-amplitude and low GEA-frequency correlated with BA slowing. The occurrence of 'irregular spike/sharp slow wave' pattern increased with age (p=0.003). Hyperventilation sensitivity was not age-related. There was no correlation between hyperventilation sensitivity and photoparoxysmal response. The age-related probability for specific GEA-types was established.

CONCLUSIONS

High GEA-amplitude and low GEA-frequency correlate with BA slowing, indicating cerebral cortical dysfunction. Hyperventilation sensitivity and photoparoxysmal response independently increase the yield of EEG. There is no age-dependency for hyperventilation sensitivity showing that an upper age threshold for hyperventilation provocation is inappropriate.

SIGNIFICANCE

The results extend our understanding of GEA and help the electroencephalographer in weighing the various GEA components.

Focal epileptiform activity described by a large computerised EEG database

OBJECTIVE

To study the age-related topographical tendency of expressing epileptiform activity, and the effect of focal epileptiform activity (FEA) on the general cortical brain activity.

METHODS

1647 consecutive routine EEGs containing FEA were visually assessed for FEA location and asymmetry. Background activity was compared with that in normal EEGs from 3268 drug-free outpatient controls.

RESULTS

FEA localisation was age-related (p<0.0005) except for the temporal region (p=0.22) where FEA was found equally often in the young and the old. The left hemisphere was more prone to FEA (p=0.018). The left-right asymmetry varied by age (p=0.013). FEA asymmetry occurred most frequently in EEGs from patients older than 80 years, and least frequent in the age-group 20-39 years. FEA was associated with lower alpha rhythm (AR) frequencies (p=0.0041) and higher AR amplitudes (p=0.0023), as well as higher general background activity (GBA) amplitude (p<0.0005), while GBA frequencies were the same (p=0.96).

CONCLUSIONS

Topographical localisation of FEA was age-dependent. There was an overall left dominance, but the side asymmetry was modest and varied by age. FEA was associated with changes in AR and GBA.

SIGNIFICANCE

The results demonstrate that FEA is associated with cerebral cortical dysfunction also distant from the epileptic focus.

EEG background activity described by a large computerized database

OBJECTIVE

To show how our newly developed software for classification and storage of visually routinely assessed EEGs are used to evaluate the general background activity (GBA) and the alpha rhythm (AR) in a large number of prospective EEGs.

METHODS

EEGs from 4651 consecutive patients were visually assessed using a computerized description system connected to an EEG database. The AR and the GBA apart from the AR were described separately for frequency and amplitude.

RESULTS

AR frequencies declined from the age of 45 years and slowed with increasing age independently of non-AR pathology and gender. Females had higher AR frequencies than males. EEGs with non-GBA pathology had lower GBA frequencies and higher GBA amplitudes. Higher GBA amplitudes were associated with lower GBA frequencies in normal EEGs for all age groups. EEG interpretations by 4 independent electroencephalographers showed the same trends, but differed in exact assessment of frequencies and amplitudes.

CONCLUSIONS

EEG interpretations stored in a categorized database with easy access to data have successfully been used to evaluate interobserver variation and other quality control measurements. Statistical analysis of the data has at the same time produced new information regarding the development of AR and GBA throughout life.

Molecular genetic analysis of Charcot-Marie-Tooth 1A duplication in Norwegian patients by quantitative photostimulated luminescence imaging

Around 70% of Charcot-Marie-Tooth 1 (CMT1) cases are caused by a dominantly inherited 1.5-Mb duplication at 17p11.2-12 (CMT1A). Using photostimulated luminescence (PSL) imaging of MspI Southern blots, hybridization signals of the probe pVAW409R3a in relation to cohybridized probe SF85a, were densitometrically quantified and an RFLP allele-band ratio determined. A total of 55 Norwegian CMT patients and 16 asymptomatic family members from 26 separate families, clinically and neurophysiologically classified as CMT1 (n=46) and CMT2 (n=9), were studied. Thirty-two of 46 CMT1 cases (69.6%), all heterozygous but one homozygous for the pVAW409R3a MspI polymorphism, from 12 of 21 families (57.1%) were positive for the CMT1A duplication. In autosomal dominant familial cases (n=30), 26 of 30 cases (86.7%), all heterozygous, from six of seven families (85.7%) were positive for duplication. None of the CMT2 patients, asymptomatic family members or healthy controls were positive for duplication. The CMT1A frequency of duplication in Norwegian CMT1 patients is in general agreement with those reported in other European countries and the present results show that quantitative densitometric PSL imaging is a highly reliable test in diagnosing CMT1A duplication.

[Hereditary neuropathy with pressure palsies]

BACKGROUND

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant polyneuropathy usually caused by a deletion in the gene coding for the peripheral nerve myelin protein 22 (PMP22). The patients usually get relapsing and remitting focal nerve symptoms due to mechanical factors like pressure or minor trauma that normal nerves tolerate.

MATERIAL AND METHODS

Two patients from different families have been examined clinically, neurophysiologically and genetically by Southern blot and PCR techniques.

RESULTS

The clinical and neurophysiological findings were typical of this disorder, and the DNA tests showed deletions in the PMP22 gene.

INTERPRETATION

We discuss clinical, neurophysiological and molecular diagnostics, pathomechanisms, treatment and secondary prevention. Early diagnosis may be important for optimal management of the patients.

[Neurological diseases associated with celiac disease]

During the period from May 1997 to October 1998, eight patients with coeliac disease or dermatitis herpetiformis and neurological disorders were admitted to the Department of Neurology, University Hospital of Bergen. The most frequent conditions were polyneuropathy (seven patients) and spinocerebellar ataxia (three patients). Other conditions were lower motor neuron disease, myelopathy, epilepsy and encephalopathy. The patients used various degrees of gluten-free diet at the time of admission. It remains unclear whether there is a shared common pathogenetic mechanism or the neurological disorder is a complication to the coeliac disease. Both vitamin depletion and immunological mechanisms may cause neurological disorder. Neurological manifestations may occur before the gastrointestinal symptoms. With reference to our patients and available literature we discuss prevalence, clinical picture, pathogenesis, treatment and prognosis. Neurologists, gastroenterologists and general practitioners should be aware that coeliac disease can cause neurological diseases, especially polyneuropathy, cerebellar ataxia and encephalopathy.

A new way of building a database of EEG findings

Whereas computer-based electroencephalography (EEG) is widely applied, the EEG interpretations are usually not stored in a way that favours exploitation of modern computer technology. This paper reports an EEG description system facilitating categorization of EEG data in a computerized database. The system interactively communicates with the digital EEG system and also with the general patient administrative system. The main new quality of this system is the methods for data input and automatic data retrieval from several systems, rather than the establishment of a database of EEG data itself. The EEGs are visually analysed and categorized. Manually marked EEG events are automatically transferred to the database and such events as well as defined electrode positions within these epochs are directly linked to their corresponding descriptions. The database is updated without demand for filling in the events in the database in a second operation. Thereby, the EEG interpreter builds the database while analysing the EEG. This system provides an improved accessibility of EEG data for clinical, normative, educational and scientific use.

[Wound botulism in heroin addiction]

Botulism is a rare disease which usually is caused by preformed botulinum toxin in food. However, this article describes a case of wound botulism in a 29-year-old male heroin addict who developed progressive diplopia, dysphagia and proximal weakness of skeletal limb muscles. He needed mechanical ventilation for two weeks. The clinical diagnosis of botulism was supported by neurophysiological tests. Assays for detection of botulinum toxin and Clostridium botulinum were negative. The patient had not eaten any contaminated food the last two weeks before symptoms appeared, but he had multiple contaminated skin wounds. After treatment with botulinum antitoxins and antibiotics he gradually recovered, and six weeks later he was discharged from hospital in good condition. To the best of our knowledge this is the first case of wound botulism reported in Norway.

[The POEMS syndrome--a rare multiorgan disease]

POEMS syndrome is a rare multisystemic disorder characterized by a variable constellation of polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin changes. The syndrome is believed to be immune-mediated and is probably related to the pathological monoclonal component caused by a myeloma or a plasmocytoma. The treatment is aimed at the underlying plasma cell dyscrasia. We have studied three patients with this rare syndrome. This article presents the clinical picture of each one and a survey of the literature.

[Ataxia due to vitamin E deficiency]

Few metabolic or degenerative ataxias can be treated pharmacologically. However ataxia due to vitamin E deficiency can be treated effectively with vitamin E supplementation if it is diagnosed early. We describe two ataxic patients with vitamin E deficiency where this was the definite or probable cause of the ataxia. Both polyneuropathy and cerebellar dysfunction were found. The deficiency was due to intestinal resection in one case, whereas the exact mechanism was unknown in the other case. In one of the patients there was a clear improvement of the ataxia after vitamin E supplementation, but this had to be taken for about six to 12 months. In the other patient the symptom progression was halted, but only slight improvement was observed. This patient therefore underwent leftsided stereotaxic thalamotomy, which markedly alleviated his rightsided ataxic symptoms. We stress the importance of testing for vitamin E (alpha-tocopherol) in all patients with ataxia where there is no other known cause.

Cerebrospinal fluid protein concentrations in patients with sciatica caused by lumbar disc herniation: an investigation of biochemical, neurologic, and radiologic predictors of long-term outcome

We studied 180 adult patients admitted to the Neurological Department, Haukeland Hospital in Bergen, Norway, for a period of 5 years from 1984 to 1988. One hundred fifty-seven patients were followed up 3.9-9.0 years after admittance to the Neurological Department. The purpose of this study was to find out if the total cerebrospinal fluid (CSF) protein concentration could predict the outcome of lumbar disc surgery or conservative treatment in patients with sciatica. Neurologic and radiologic parameters were also included in the investigation. The increase of the CSF total protein concentration in sciatica without spinal block is assumed to be due to leak of plasma proteins into the CSF from the nerve root. A relationship between CSF protein concentrations and certain clinical parameters has been found. At myelography, 10 ml of CSF was collected for analysis. The patients were evaluated for involvement of the nerve root and/or the dural sac, respectively. The neurologic parameters investigated were: straight leg raising tests, paresis, disturbances of sensibility, and altered reflexes. At follow-up, the patients were asked to fill in questionnaires concerning job function, sick leave or disability pension, subjective physical disability and pain perception, and a clinical examination with the same neurologic parameters was performed. Elevated CSF total protein concentration was related to chronic leg pain, leg pain, and subjective physical disability at follow-up. Nonoperated women reported higher subjective physical disability scores and were more often on sick-leave or disability pension than were men at follow-up. Lateral prolapses were associated with good job function outcome and less risk for sick-leave or disability pension. Reduced lower extremity reflexes, laterally located disc herniation and elevated CSF total protein concentration were associated with a favorable long-term outcome in patients with sciatica. CSF proteins as objective measures on nerve root injury are discussed. CSF total protein concentration can be regarded as an indicator of the functional status of the nerve root and a prognostic factor in patients with sciatica.

The course of epilepsy during pregnancy: a study of 78 cases

We have compared frequency and severity of epileptic seizures during pregnancy with the 9 months prior to pregnancy in 66 patients with a total of 78 pregnancies. Data on total number of seizures and major seizures are analysed separately. No statistically significant differences between frequency before and during pregnancy were found. Cases with seizures before pregnancy tended to have seizures during pregnancy, but there was no association between occurrence of seizures prior to pregnancy and increased frequency during pregnancy. There was no evidence that seizures became more severe during pregnancy. No relationship was found between type of epilepsy and change in seizure frequency during pregnancy. The data suggest that our therapeutic interventions may have influenced seizure frequency in at most a minority of cases. Serum concentrations of the anti-epileptic drugs were monitored regularly during pregnancy. Only data on patients on constant drug dosages and, therefore, presumedly with the mildest seizure disorders were analysed. In the majority of cases there was a decrease in drug levels during pregnancy. Most cases tolerated this decrease without an increase in seizure frequency. On the other hand, most cases with increased frequency also had decreased drug levels.

Cerebral schistosomiasis presenting as a brain tumor

A patient with cerebral Schistosoma mansoni schistosomiasis is described. The infection presented as a cerebral tumor, and the patient did not have the usual hepatic or intestinal symptoms of this disease. The computed tomography (CT) findings in histologically proven cerebral schistosomiasis are reported. The pathological CT findings developed at a late stage of the disease, and the CT scans were normal at a time when the EEG recordings were pathological.