Voltage-dependent action of valproate on potassium channels in frog node of Ranvier.

The influence of the anti-epileptic drug, valproate, on K conductance (gK) was investigated in voltage-clamped Ranvier nodes of Xenopus laevis. A double pulse method was used in order to eliminate the effect of accumulation of potassium ions in the perinodal space, thus enabling the determination of the 'true' magnitude of gK. Valproate (2.4 mM) had a voltage-dependent action on the magnitude of gK. With small step depolarizations more negative than about -50 mV, valproate increased gK (20 ms after the step) to approximately 12% of the maximal gK, an increase which disappeared due to a relatively rapid (less than 200 ms) inactivation process. However, with step depolarizations more positive than about -50 mV, valproate markedly reduced gK (20 ms after the step) at greater depolarizations, with a maximum of about 40% of the maximal gK. Moreover, at these voltages gK was inactivated completely (less than or equal to 10 s), whereas under control conditions the inactivation was only partial. Both the temporary increase and the steady state decrease of gK could contribute to an anti-epileptic effect by increasing the action potential threshold and by preventing excessive depolarizations of the nerve during epileptic seizures, respectively.

Facilitation of early and masking of late cortical responses in dementia.

Topographic differences in longlatency SSEP and flash VEP data are compared in 3 different psychiatric patient groups. Differences between schizophrenia and affective disorder are restricted to somatosensory P100 amplitude gradients along the antero-posterior axis. In contrast EP-differences between psychiatric patients and dementia are prominent, encompassing both late and early (< 100 ms) responses. Our flash P 2 and somatosensory P 3 data are in accordance with previous findings. Multi-modal positive responses with a latency of 40-80 ms are significantly increased in dementia. This facilitation suggests cortical dysfunction and/or subcortical gating impairment.

Impaired early visual processing in disorganised schizophrenia.

Topographic differences in flash/pattern shift VEP data are evaluated in paranoid (n: 38), disorganized (n: 23) and residual (n: 23) schizophrenic subtypes and compared to normal controls. Increased early P1 and a restricted diffusion of the late P2 responses suggest dopaminergic over- and cholinergic underactivity in paranoid and residual schizophrenia. A distinctive pattern N145 reflects well-preserved attentional resources in the paranoid subtype. Latency increase and amplitude decrease of the pattern N145 concur with abnormal antisaccades documented in disorganized behaviour. VEP-data might help differentiate between schizophrenic subtypes.

Automatic breath-to-breath analysis of nocturnal polysomnographic recordings.

Diagnosis of sleep-disordered breathing is based on the presence of an abnormal breathing pattern during sleep. In this study, an algorithm was developed for the offline breath-to-breath analysis of the nocturnal respiratory recordings. For that purpose, respiratory signals (nasal airway pressure, thoracic and abdominal movements) were divided into half waves using period amplitude analysis. Individual breaths were characterized by the parameters of the half waves (duration, amplitude, and slope). These values can be used to discriminate between normal and abnormal breaths. This algorithm was applied to six polysomnographic recordings to distinguish abnormal breathing events (apneas and hypopneas). The algorithm was robust for the identification of breaths (sensitivity = 96.8%, positive prediction value (PPV) = 99.5%). The detection of apneas and hypopneas was compared to the manual scoring of two experienced sleep technicians: sensitivity was, respectively, 89.2 and 88.9%, PPV was 54.1 and 59.3%. The classification of apneas into central, obstructive, or mixed was in concordance with the observers in 68% of the apneas. Although the algorithm tended to detect more hypopneas than the clinical standard, this study shows that the extraction of breath-to-breath parameters is useful for detection of abnormal respiratory events and provides a basis for further characterization of these events.

Neuropsychiatric aspects of patients with hypothalamic hamartomas.

Hypothalamic hamartomas (HH) are developmental malformations that are associated with gelastic seizures, other types of seizures, cognitive decline, and symptoms related to hypothalamic dysfunction. Although aggressive behavior is frequently described, data on the neuropsychiatric profile are limited. In this article, five patients with HH are described who displayed a wide variety of psychiatric symptoms that, dependent on the time frame, met the criteria for several categorical diagnoses. Major neuropsychiatric symptoms comprised aggression that is only partial context dependent, compulsive behavior, psychotic symptoms not responding to treatment, and organic mood instability. HH should therefore be considered a neuropsychiatric syndrome with a highly variable expression that can be best captured by a thorough description of behaviors, symptoms, sequelae of epilepsy, and hypothalamic dysfunction.

Auditory information processing in schizophrenia.

Early N1P2 and late N2P3 responses generated in an auditory oddball paradigm are topographically compared in three psychiatric patient groups. In schizophrenia N1 and N2 amplitude is comparable with dementia and significantly decreased with respect to affective disorder. In contrast, P3 amplitude does not allow discriminating schizophrenia from affective disorder but is significantly diminished in dementia. The late N2P3 response shows a topographic effect along the fronto-occipital axis. Schizophrenia is characterized by an iCNV and N2 maximum over the frontal planes and a compound P3 lacking distinct frontal and parietal components. The findings are discussed in reference to literature data and current hypotheses/theories concerning information processing. Our findings favour an important dysfunction of automatic processing including early selection in schizophrenia.

Neurological sequelae in mycosis fungoides. Report of a case.

Central nervous system (CNS) involvement in mycosis fungoides (MF) usually occurs in the presence of active skin lesions and infiltration of many visceral organs. A case of MF is presented, associated with a neurological syndrome, characterized by ataxia and motor-neuron disease. Autopsy revealed widespread infiltration of the CNS by MF, in the presence of only one minimal skin lesion and with no involvement of visceral organs. The importance of being aware of this discrepancy is stressed in the light of the possibility of radiotherapy in CNS involvement.