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To investigate whether Unverricht–Lundborg disease (ULD) and Lafora body disease (LBD) can be differentiated on the basis of their neurophysiologic profiles.

1The effect of the protein kinase C (PKC) activator 1‐oleoyl‐2‐acetyl‐sn‐glycerol (OAG) on TTX‐sensitive Na+currents in neocortical pyramidal neurones was evaluated using voltage‐clamp and intracellular current‐clamp recordings.2In pyramid‐shaped dissociated neurones, the addition of OAG to the superfusing medium consistently led to a 30 % reduction in the maximal peak amplitude of the transient sodium current (INa,T) evoked from a holding potential of −70 mV. We attributed this inhibitory effect to a significant negative shift of the voltage dependence of steady‐state channel inactivation (of approximately 14 mV). The inhibitory effect was completely prevented by hyperpolarising prepulses to potentials that were more negative than −80 mV. A small but significant leftward shift of INa,Tactivation was also observed, resulting in a slight increase of the currents evoked by test pulses at potentials more negative then −35 mV.3In the presence of OAG, the activation of the persistent fraction of the Na+current (INa,P) evoked by means of slow ramp depolarisations was consistently shifted in the negative direction by 3.9 ± 0.5 mV, while the peak amplitude of the current was unaffected.4In slice experiments, the OAG perfusion enhanced a subthreshold depolarising rectification affecting the membrane response to the injection of positive current pulses, and thus led the neurones to fire in response to significantly lower depolarising stimuli than those needed under control conditions. This effect was attributed to an OAG‐induced enhancement of INa,P, since it was observed in the same range of potentials over which INa,Pactivates and was completely abolished by TTX.5The qualitative firing characteristics of both the intrinsically bursting and regular spiking neurones were unaffected when OAG was added to the physiological perfusing medium, but their firing frequency increased in response to slight suprathreshold depolarisations.6The obtained results suggest that physiopathological events working through PKC activation can increase neuronal excitability by directly amplifying the INa,P‐dependent subthreshold depolarisation, and that this facilitating effect may override the expected reduction in neuronal excitability deriving from OAG‐induced inhibition of the maximal INa,Tpeak amplitude.

Objective: The aim of this study was to evaluate the characteristics of the ictal EEG event accompanying infantile spasms.

1. Neurones of the nucleus reticularis thalami of the rat were studied by intracellular recordings from in vitro slices. The resting membrane potential was ‐56.28 +/‐ 5.86 mV (mean value +/‐ S.D.); input resistance was 43.09 +/‐ 9.74 M omega; the time constant tau was 16.51 +/‐ 3.99 ms. At the resting membrane potential tonic firing is present, while at membrane potentials more negative than ‐60 mV a burst firing mode gradually prevails. 2. Prolonged depolarizing current pulses superimposed on a steady hyperpolarization consistently activated sequences of burst‐after‐hyperpolarization complexes. The all‐or‐none burst response consisted of Na+‐mediated, TTX‐sensitive fast action potentials superimposed on a low threshold spike (LTS). The burst was followed by a stereotyped after‐hyperpolarization lasting 100‐120 ms (BAHP), with a maxima ‐85 mV. The BAHP was blocked by Cd2+ and apamine but not by 8‐Br cyclic AMP. The early component of BAHP was significantly attenuated by TEA. The oscillatory rhythmic discharges were abolished by agents which blocked the BAHP. 3. The presence of strong after‐hyperpolarizing potentials (SAHP and BAHP) in RTN neurones plays a significant role in determining two different functional states, defined as tonic and oscillatory burst firing modes, respectively.

Visual (VEP) and brainstem auditory (BAEP) evoked potentials (EP) were recorded in 21 multiple sclerosis (MS) patients in acute relapse before and after steroid treatment. VEPs were abnormal in 14/21 patients and BAEPs in 10/21 patients before treatment. In 4 patients with acute optic neuritis (ON), an improvement of VEPs paralleled clinical evolution in 3 cases. Substantial and contrasting changes in VEPs or BAEPs, with no clinical counterpart, were related to a spontaneous fluctuation of EPs in acute relapses of MS. These changes suggest frequent subclinical (multifocal and, possibly, sequential) central nervous system involvement in MS bouts. Group analysis showed nonsignificant changes in EP parameters before and after treatment. Our results indicate that evoked potentials (EPs) are of limited value for monitoring the short-term effect of steroid treatment in MS in bouts.

1. We investigated the development of epileptic activity in the limbic lobe of the in vitro isolated brain preparation after induction of a restricted epileptic focus in the rostral portion of the anterior piriform cortex (APC) by means of local bicuculline ejection. 2. The modifications of the local responses evoked by stimulation of the lateral olfactory tract were consistent with an increase in excitability of layer II pyramidal neurons. The abnormal discharge output of the epileptic focus propagated throughout the piriform cortex (PC) and generated late synaptic stimulus-evoked epileptiform potentials in layer Ib, where corticocortical associative fibers contact the distal dendrites of pyramidal cells. 3. Spontaneous epileptiform potentials (SEPs) originated in the primary focus at the bicuculline ejection site 10-15 min after drug application and propagated via associative fibers to the posterior PC (PPC). 4. Autonomous secondary foci generating SEPs independently from the primary anterior focus developed in the PPC within 2 h after the bicuculline application. 5. Ictal events seldom occurred spontaneously in PC but could be induced by tetanic afferent stimulation. Evoked ictal events in PC had the characteristics of afterdischarges, being short in duration and localized in space and showing a progressively decreasing firing rate. 6. Self-sustained spontaneous ictal discharges were observed in the entorhinal cortex and hippocampus but not in PC after activation of the APC focus. 7. We conclude that in an acute pharmacological model of focal epilepsy, associative corticocortical connections hold a primary role 1) in the propagation of interictal epileptiform activity throughout the limbic lobe and 2) in the generation of secondary epileptic foci. We also demonstrate that self-sustained ictal events are not spontaneously generated in PC, although paroxysmal seizure-like discharges occur in hippocampus. We discuss the relevance of the rostral-to-caudal-directed associative fiber system in generation of limbic seizures.

Summary One hundred and twenty-eight adult patients presenting with and operated on for supratentorial neoplasms were studied.

Without Abstract:

Neurological derangement has been reported in haemodialysed patients receiving intravenous desferrioxamine (DFO) for aluminium-related disorders. The possible direct effects of desferrioxamine on EEG recordings were investigated in ten haemodialysed patients who underwent a DFO test 2 h after the end of dialysis. According to a commonly accepted protocol, 40 mg/kg body-weight of desferrioxamine was infused in 60 min. EEG recording was continuously performed, starting 30 min before and stopping 30 min after the desferrioxamine infusion. Besides visual inspection, EEG records were digitised, tapered, and spectrally analysed with Digital PDP 11/73 microcomputer. Basal EEG recording was normal in all patients. In three patients a progressive EEG slowing was detected by visual inspection during desferrioxamine infusion; in these cases automatic analysis revealed a 50% increase in power of slower frequencies 30 min after starting the infusion, when no changes in plasma aluminium concentrations are detected; a complete recovery was observed 30 min after desferrioxamine withdrawal. In one patient bilateral paroxysms of slow waves appeared, so we stopped desferrioxamine infusion. Two of the three patients who developed EEG abnormalities also had an increased aluminium body burden (positive DFO test). Results indicated that desferrioxamine per se can modify EEG in haemodialysis patients and that its effect is not mediated by acute increases of plasma aluminium concentrations. The finding of a positive DFO test in two of three patients with EEG changes may suggest that an aluminium-induced blood-brain barrier derangement could have played a role. However, prompt recovery after ceasing desferrioxamine infusion strongly suggests a direct role of desferrioxamine in the induction of EEG changes. These findings contribute to a better understanding of the acute impairment in neurological status when high doses of desferrioxamine are infused in haemodialysis patients with aluminium overload.