Reappearance of event-related P3 potential in locked-in syndrome.

In a patient affected by locked-in syndrome, because of a lesion of the caudal-ventral pontine tegment, we recorded event-related potentials (ERPs) to an acoustic odd-ball paradigm. We did not record N2 and P3 components in the 50 days following the acute lesion although the patient was able to understand the task and communicate with blinking. 55 days after the acute lesion, N2 and P3 reappeared on scalp derivations. This findings suggest that brainstem structures are involved in P3 or N2-P3 generation.

Delayed and pseudodelayed visual evoked potentials in optic neuritis compared with long time echo-short tau inversion recovery magnetic resonance imaging of optic nerve.

Twenty patients affected by optic neuritis (ON) underwent serial visual evoked potential (VEP) recordings, performed with multiple electrode arrays, and with stimuli of 1 and 3 cycles per degree (cpd) for 1 year. VEP findings were correlated with long time echo-short tau inversion recovery (LTE-STIR) magnetic resonance imaging (MRI) of optic nerves and with visual field tests. MRI showed lesions in 95.2% of acute ON and in 66.6% of the 1 year follow-up. VEPs were classified into really 'delayed' VEPs and 'pseudodelayed' VEPs, based on their scalp distribution. Furthermore, VEPs to 1 or 3 cpd could be 'delayed' or 'pseudodelayed' in the same patient. Real delays could be recorded at onset or shortly after ON, and indicated the possibility of recovery of visual functions and good functional prognosis. Pseudodelays, to 3 cpd, corresponded to prominent central scotomata and indicated poor prognosis for the recovery of visual function, unless a breakthrough of normal or delayed components appeared in the first 4 months following acute ON. Pseudodelayed VEPs clustered in patients with longer demyelinating lesions, as shown by LTE-STIR MRI. There was no correlation between latency of VEPs and length of plaques. Our study addresses some reconsiderations of the pathophysiology of conduction delay in acute optic neuritis.

Long time echo STIR sequence magnetic resonance imaging of optic nerves in optic neuritis.

Magnetic resonance images of optic nerves were obtained in 20 patients with acute optic neuritis (ON), and assessed by means of clinical, visual field and visual evoked potential evaluations; the imaging was repeated 1 year later. The results of the conventional Short Tau Inversion Recovery (STIR) sequence obtained using short time echo (STE-STIR: 22 msec) were compared with those of the long time echo sequence (LTE-STIR: 80 msec). The conventional STE-STIR sequence revealed lesions in 57.2% cases of acute ON and in 42.9% of the optic nerves affected by previous ON; the LTE-STIR sequence was diagnostic in 95.2% of acute ON cases and in 85% of patients with previous ON. The calculated length of the optic nerve lesions was significantly longer in the images obtained using the LTE-STIR sequence than in those obtained using conventional STE-STIR sequences.

Are VEP abnormalities in optic neuritis (ON) dependent on plaque size? A reappraisal of the physiopathology of ON based on improved MRI and multiple-lead recordings.

Twenty patients with optic neuritis (ON) described in the previous study [23] underwent serial VEP recordings (using multiple electrode arrays) for two years. The VEPs could be correlated with the lesions revealed by MRI, Visual Field tests and other clinical findings. On the basis of their scalp distribution, they were classified as "really delayed" VEPs and "pseudo-delayed" VEPs. Real delays could be recorded at the onset of ON or shortly afterwards, and their appearance indicated the recovery of visual function and a good prognosis. Pseudo-delays indicated an alteration in the visual field and, unless a breakthrough of normal or delayed components appeared in the first three months, following acute ON, indicate a poor prognosis for the recovery of visual function. The pseudo-delayed VEPs were mainly observed in patients with longer lesions revealed by means of LTE-STIR MRI [23]; there was no correlation between VEP latency and the length of plaques. Our findings contradict previous theories on the timing of conduction alterations in ON and multiple sclerosis.

Evoked potential (EP) alterations in experimental allergic encephalomyelitis (EAE): early delays and latency reductions without plaques.

Experimental allergic encephalomyelitis (EAE) in its chronic relapsing (CR-EAE), chronic progressive (CP-EAE) and acute (A-EAE) forms was obtained in 24 juvenile strain 13 guinea pigs. Visual, brainstem acoustic and somatosensory evoked potentials (EPs) were recorded in these animals prior to the sensitizing injection and during the course of the disease. Delays in the EPs appeared 15 days post-sensitization (dps), preceding or simultaneously with clinical alterations: electron microscopy revealed myelin stripping and vacuolation in the animals sacrificed 25 dps. Decreases in EP latency were recorded 32 dps; when electron microscopy revealed myelin layers indicating remyelination, whereas light microscopy showed only inflammatory changes. When confluent plaques were revealed by light microscopy 120 dps, the EP wave shapes were distorted or absent. The discussion reviews the literature on early myelin and conduction changes during central demyelination.

Long echo time STIR sequence MRI of optic nerves in optic neuritis.

MRI of the optic nerves was obtained in 13 patients with acute optic neuritis and 13 with a previous optic neuritis (ON), assessed by clinical features, visual fields and visual evoked potentials. Results of the conventional short tau inversion recovery (STIR) sequence obtained with a short echo time (STE-STIR; 22 ms) were compared with those of a long echo time (LTE-STIR: 80 ms) sequence. The conventional STE-STIR sequence revealed lesions in the optic nerves in 78.5% of acute and 58.8% of previous ON. The LTE-STIR sequence showed abnormalities in 92.8% of acutely symptomatic nerves and 94.1% of nerves with previous ON. The optic nerve lesions appeared significantly longer with the LTE-STIR sequence than with the conventional STE-STIR sequences, in both acute and previous ON.

Newborns with hyperbilirubinemia: usefulness of brain stem auditory response evaluation.

We describe brain stem auditory evoked potentials (BAEP) obtained in 48 full-term newborns (20 boys, 28 girls) presenting with high serum total bilirubin concentration (from 238 to 442 mM) without Rhesus of group A, B, O factors incompatibility. Recordings were performed on the 3rd day of life and repeated 5-7 days post-appropriate therapy with photostimulation and exchange transfusion (when bilirubin concentration had decreased below 136 mM). Supplementary recordings were performed 3, 6 and 12 weeks later in order to assess test-retest reliability of components. Mean values of BAEP latencies were compared with those obtained in 40 age-matched control subjects using the same recording procedures. At first recording session (on the 3rd day), latencies of waves III and V obtained in hyperbilirubinemic patients were significantly increased as compared with records in control subjects. Recordings performed 5 to 7 days post-therapy and during subsequent recording sessions showed no significant differences between patients and control groups. Serial neuropsychological evaluations obtained over a 3-year follow-up showed no subsequent neurodevelopmental abnormality for all patients. These findings suggest that hyperbilirubinemia can alter central neurotransmission in auditory brain stem pathways, but this modification is only transient.

Visual evoked potentials generator model derived from different spatial frequency stimuli of visual field regions and magnetic resonance imaging coordinates of V1, V2, V3 areas in man.

Visual evoked potentials (VEPs) to pattern reversal vertical bar stimuli were recorded from 24 scalp derivations (including zygomatic and inion) referenced to digitally linked earlobes in 50 controls. 1, 2 and 4 cpd patterns were presented as full field (FF) stimuli, on Upper Hemifields (UHF) and Lower Hemifields (LHF), upper and lower quadrants and with the occlusion of central and peripheral UHF and LHF. VEPs to octant stimuli were also recorded with 2 cpd patterns. N1, P1 and N2 components were recorded from posterior and inion derivations with FF stimuli, from posterior derivations with LHF stimuli, only from inion leads with UHF stimuli, from derivations ipsilateral to stimuli with quadrants and octants, and consistently from midline derivations only with lower quadrants. Polarity inverted sequences (iN1-iP1-iN2) were recorded from the other scalp derivations, with similar latency and spatial frequency sensitivity as N1-P1-N2. Single Equivalent Dipole (ED) calculations were performed on N1 and P1 recorded in the different stimulus conditions. Our findings contradict previous hypotheses on VEP generators and contradict the predictions of VEPs polarity and distribution based on the "cruciform model" of VEPs generators. In order to explain the distribution of VEPs to upper and lower half fields and to quadrant and octants, we propose a model based on the position of the medial and occipito-polar surface of visual cortex in man.

Event related potentials recorded in Dorsal Simultanagnosia.

Visual evoked potentials (VEPs) to central and lateral half field patterned stimuli of 1, 2 and 4 cycles per degree (cpd) were recorded in a patient with Dorsal Simultanagnosia due to bilateral lesions of parieto-occipital junction. VEPs consisted of the normal N1-P1-N2 components with same spatial frequency sensitivity as in controls. VEPs had similar latencies and amplitudes whether the patient could see or not the patterned stimuli. Event related potentials (ERPs) to visual and acoustic odd-ball paradigm were also recorded in the same patient. Visual ERPs consisted of an early NA-effect, and of N2-P3 components. P3 was recorded only from frontal, central and temporal derivations. The topographical P3 abnormality was, however, the same for visual and acoustic odd-ball paradigms. The amplitude of P3 was smaller when the patient missed visual stimuli. These findings show that severe bilateral lesions at the parieto-occipital junction, inducing Simultanagnosia, do not obliterate VEPs or ERPs components.

Non-dominant dorsal-prefrontal activation during chess problem solution evidenced by single photon emission computerized tomography (SPECT).

Expert chess players can recall meaningful chess positions with extraordinary precision in comparison with inexperienced players. We hypothesized, therefore, that their mental performance during chess deliberation could be an appropriate target for single photon emission computerized tomography (SPECT) studies. We studied cerebral activation with 1110 MBq 99mTc-Bicisate SPECT in five expert male chess players during mental solution of a complex chess problem. Region of interest (ROI) analysis, in comparison with average weighted cerebellar counts, showed activation by 10% or more, of the non dominant prefrontal area (right in four dominant right handed players, left in one dominant left handed player) and by 2-6% in the non-dominant middle temporal areas. Maximum variability of ROI analysis versus cerebellar counts in test/retest evaluation is in our laboratory, as in others, 1.5%. Our results are in agreement with neuropsychological studies suggesting that the non-dominant hemisphere is specialized for chess skill, and show that non-dominant prefrontal and temporal lobe activation during chess deliberation can be detected by SPECT.

P300 asymmetries in focal brain lesions are reference dependent.

In 6 patients with lesions of frontal, parietal and temporal lobe, in 4 patients affected by primary progressive aphasia (PPA) and in 56 age-matched controls, event-related potentials (ERPs) to an auditory odd-ball paradigm were recorded with the linked earlobe reference (LER) and with a computer calculated average reference (AR), excluding the two linked earlobe derivations. Latencies, amplitudes and scalp distribution of the earlier ERP components (P1, N1, P2, N2) were within normal limits for both LER and AR recordings. P300 scalp distribution in patients was normal when LER was used. When P300 was recorded using AR, the scalp distribution was statistically different from normal distributions in all patients. A negativity, instead of the positive P300 observed in controls, was recorded in patients from leads corresponding to the affected hemisphere.

Long time echo stir sequence magnetic resonance imaging of optic nerves in optic neuritis.

Magnetic resonance imaging of optic nerves was obtained in 13 patients with acute optic neuritis and in 13 patients with a previous history of optic neuritis (ON), assessed by clinical, visual fields and visual evoked potentials evaluations. Results of the conventional short tau inversion recovery (STIR) sequence obtained with short time echo (STE-STIR: 22 ms) were compared with long time echo (LTE-STIR: 80 ms) sequence. The conventional STE-STIR sequence revealed lesions in 78.5% of acute ON and in 58.8% of optic nerves affected by previous ON. The LTE-STIR sequence was diagnostic in 92.8% of acutely symptomatic nerves, in 94.1% of nerves with previous ON. The calculated length of optic nerve lesions was significantly longer in imaging obtained with the LTE-STIR sequence than with the conventional STE-STIR sequences, both in acute and previous ON.

Source model and scalp topography of pattern reversal visual evoked potentials to altitudinal stimuli suggest that infoldings of calcarine fissure are not part of VEP generators.

Visual evoked potentials (VEPs) to pattern reversal vertical bar stimuli were recorded from 19 scalp, 2 zygomatic and 3 inion derivations referenced to digitally linked earlobes in 50 controls. 1, 2 and 4 cycles per degree (cpd) patterns were presented as full field (FF) stimuli, on upper and lower hemifields (UHF-LHF), upper and lower quadrants and with the occlusion of central and peripheral UHF and LHF. VEPs to octant stimuli were also recorded with 2 cpd patterns. N1, P1 and N2 components were recorded from posterior and inion derivations with FF stimuli, from posterior derivations with LHF stimuli, only from inion leads with UHF stimuli, from derivations ipsilateral to stimuli with quadrants and octants, and from midline derivations only with lower quadrants. Polarity inverted sequences (iP1-iN1-iP2) were recorded from the other scalp derivations, with similar latency and spatial frequency sensitivity as N1-P1-N2. The orientation of Equivalent Dipoles (ED) was orthogonal with surface coordinates of mesial and occipito-polar calcarine cortex, measured on Magnetic Resonance Imaging. A model of VEP generators is proposed, suggesting that the VEP sequence is elicited only in mesial and occipito-polar surfaces of calcarine cortex.

The abnormality of N30 somatosensory evoked potential in idiopathic Parkinson's disease is unrelated to disease stage or clinical scores and insensitive to dopamine manipulations.

We recorded short latency somatosensory evoked potentials (SEPs) to median nerve stimuli in 40 patients affected by idiopathic Parkinson's disease (PD) classified from I to IV on the Hoehn and Yahr disability scale. SEPs were recorded before and after chronic administration of L-Dopa and bromocriptine, before and after acute administration of L-Dopa. Fourteen patients experiencing wearing off and dystonic-dyskinetic disturbances were recorded during the occurrence of these oscillations of their clinical status. Absent or reduced N30 components were found in 32.5% of patients. SEPs were not modified by acute or chronic administration of L-Dopa or bromocriptine or during off and dystonic or dyskinetic conditions. Multiple correlations of N30 with scores of the Unified Parkinson's Disease Rating Scale showed that N30 abnormality did not classify patients with prominent clinical features, nor did it predict the outcome of treatment.

L-acetylcarnitine as a new therapeutic approach for peripheral neuropathies with pain.

With ST200 as the commercial source of L-acetylcarnitine hydrochloride, 94 patients were enrolled in this study; 31 were assigned to placebo, 31 to ST200 at 0.5 g/die and 32 to ST200 at 1 g/die, the i.m. treatments being injected daily for 15 consecutive days. In general, concerning the efficacy assessment, the administration of ST200 at 1 g/die appeared to be better than ST200 at 0.5 g/die when compared with the placebo administration. Statistically significant differences were revealed by the comparison of ST200 at 1 g/die to placebo, for the following variables: a) total motility as rated at the end of the 15-day study and confirmed by intention-to-treat analysis, b) visual analogue scale for all the patients having observation at day 15, and c) the objective and subjective judgements on efficacy. Safety and tolerability were good over the entire course of the study.

Focal abnormalities of P3 ERPs unveiled in patients with cortical lesions and primary progressive aphasia by average reference recordings.

Event related potentials (ERPs) to an auditory odd-ball paradigm were recorded with the linked earlobe reference (LER) and with a computer calculated average reference (AR), excluding the two linked earlobe derivations. The study was performed in 30 patients with lesions of frontal, parietal, occipital cortex, unilateral and bilateral lesions of the medial temporal lobe (MTL), in four patients affected by Primary Progressive Aphasia (PPA) and in 56 age matched controls. Latencies, amplitudes and scalp distribution of the earlier ERP components (P1, N1, P2, N2) were within normal limits for both LER and AR recordings. P3 scalp distribution in patients was normal when LER was used, with the exception of two patients affected by bilateral MTL lesions. When P3 was recorded using AR, the scalp distribution was statistically different from normal distributions in all patients. A negativity, instead of the positive P3 observed in controls, was recorded in patients from leads corresponding to the affected areas. This finding might have clinical applications, and confirms earlier studies suggesting that P3 is generated simultaneously from different cortical areas.

Effects of drug manipulations on anterior components of somatosensory evoked potentials in a parkinsonian animal model.

Somatosensory Evoked Potentials (SEPs) to median nerve stimuli were recorded in seven Cynomolgus monkeys before and after the induction of the MPTP-parkinsonian syndrome. SEPs recorded after the onset of parkinsonism showed a significant amplitude reduction of an anterior negative component peaking at about 15 ms (N15), independent of the severity of symptoms. The amplitude decrease was not reversed by the administration of I-dopa, despite clinical improvement, or cholinergic, noradrenergic and gabaergic agents. Amplitudes of N15 and of parietal P15 components were increased by the administration of the N-MDA antagonists ketamine and MK 801, and markedly increased when monkeys were given the anaesthetic agent etomidate. The present study shows that the reduced N15 SEP component of parkinsonian monkeys is similar to the reduced frontal N30 SEP component evidenced by other authors in patients affected by Parkinson's disease. The attenuation of N15 is not related to deficitary dopaminergic, noradrenergic, cholinergic and gabaergic systems. The implications of this finding and the role of glutamate toxicity are discussed.

MRI alterations as an early finding in Creutzfeld-Jakob disease.

Two cases of Creutzfeldt-Jakob Disease (CJD) are reported. In both cases, pathologically confirmed, magnetic resonance imaging (MRI) showed bilateral altered signal areas in the basal ganglia, early in the course of the disease. The CT scan, although performed later than MRI, confirmed these findings. Only in one patient did electroencephalography (EEG) show typical triphasic sharp-waves, but this support to clinical diagnosis was obtained 1 month after the appearance of MRI alterations.