- Email: [email protected]
Amplitude asymmetry of hemi-field pattern reversal VEPs
s77
TranscrarQal magnetoelectrical stimulation of the motorcortex was performed (Magstim 200, Novametrix) at threshold intensity, and the peak latency of evoked SMU potentials measured. Recordings were obtained by small concentric needle
tients under anesthesia or drug intoxication, and with anoxic/ metabolic encephalopathiea When these conditions were excluded. GPSC indicated the diagnosis of subacute sclerosing panencephalitis (SSPE). Suppression bursts were noted in cases
electrodes (electrode surface: 0.015 mm) from 25 different SMU in the first dorsal interosseus (FDI) of 10 normal subjects. Activation of SMU occurred at mean latencies of 24.0-30.0 msec (range for all SMU: 23.5-30.6 msec; n = 25 SMU). The onset latency of the corresponding maximum CMAP as measured with surface electrodes over the FDI muscle belly was always shorter (mean difference: 3.9 msec). At repetitive stimulation SMU varied only slightly in latency. The average variability for all SMU was 0.4 msec ( f 1 SD) and the range of the variability for single units was 0.1-0.6 msec (f 1 SD). No significant groupings of SMU latencies and no double discharges of individual SMU were observed. Results were similar for SMU recruited either early or late in .relation to the CMAP. These observations in normal subjects may be due to a variation of synaptic transmission times rather than to excitation by various I-waves. In contrast preliminary results from MS patients show pronounced variability in latencies of SMU.
of deep sedation and of hypoxic encephalopathy. The outcomes of 125 patients with suppression bursts in the literature were assessed. Nine subjects under the effect of CNS depressant were excluded; of the remaining 116 patients, 111 died. A mortality of 96% indicates the grave prognostic importance of suppression bursts in cases of hypoxic encephalopathy. The GPSC pattern is not specific for the diagnosis of SSPE, but occurred in bromide intoxication and phencyclidine hydrochloride drug abuse. Generalized repetitive sharp transients were observed in patients with Creutzfeldt-Jakob’s disease and in those with anoxic encephalopathy causing cortical spongy changes. Generalized triphasic waves occurred only in patients with metabolic/anoxic encephalopathies. Six of our 8 patients died during the first 10 days following the recording. The other 2 patients improved temporarily, but died later from complications of their primary disease. This suggests that periodic triphasic waves are most often recorded in patients with irreversible metabolic encephalopathies. Periodic lateralized epileptiform discharges were associated with clinical seizures in 24/26 cases and were noted almost exclusively in destructive hemispheric lesions.
AMPLITUDE ASYMMETRY REVERSAL VEPs.
OF HEMI-FIELD
PAlTERN
EFFECT OF AGE, SEX AND HEAD SIZE ON PATTERN VEP.
Y. Kuroiwa and Y. Abe (Toranomon
Hospital,
Tokyo,
Japan) Y. Kuroiwa and K. Chiba
The amplitudes of transient and steady-state visual evoked potentials were measured during hem&field stimulation of the left eye in 10 healthy adults. Pattern reversal of a checkerboard was produced at 4 stimulation frequencies: 1, 5, 10 and 15 Hz. The amplitudes of pattern VEPs were evaluated using the paired r-test to determine significant differences between right and left her&fields. The transient VEP amplitudes from midoccipital, ipsilateral occipital and contralateral occipital electrodes were significantly greater with right hemi-field stimulation. The steady-state VEP amplitudes from mid-occipital electrode during 15 Hz stimulation were significantly greater with right hem&field stimulation. Our neurophysiological data may be compatible with neuro-anatomic asymmetries of occipital lobes in humans.
THE PROGNOSTIC NOMENA.
VALUE
OF PERIODIC
EEG
PHE-
Y. Kuroiwa and G.G. Celesia (Toranomon
Hospital,
Tokyo,
Japan)
Generalized and focal periodic EEG patterns were studied in 80 patients. Generalized periodic suppression bursts and generalized periodic slow-wave complexes (GPSC) occurred in pa-
(Toranomon
Hospital,
Tokyo,
Japan)
The subjects consisted of 167 healthy people (71 males, 96 females). Their mean age was 45.7+ 19.1 years. Full-field monocular stimulation was performed using three check sizes (15, 30 and 60 mm), at a rate of 1 Hz. Electrodes were placed 5 cm above the inion and 12 cm above the nasion. We measured (1) head circumference and height; (2) VEP latency (P50, N74, PlOO, N145); (3) VEP amplitude (P50-N75, N75-PlOO, PlOO-N145). Correlation analysis was done between latency and age, head size, or height; between amplitude and age, head size or height; between head size and age; between height and age; and between head size and height. The mean values were compared by r-test between the male and female groups with regard to age, head size, height, latency and amplitude. Mean VEP latency to 15 min checks was significantly longer than that to 30 or 60 min checks. Mean VEP amplitude to 15 min checks was significantly larger than that to 30 or 60 min checks. VEP latency showed a curvilinear relationship with age. VEP amplitude decreased with head size or height. The VEP in males showed a longer latency and a smaller amplitude than that in females. Linear regression analysis between head size or height and age showed a negative relationship. Normative data of the pattern VEP is affected by (1) biological factors, such as neuronal changes due to develop-
TranscrarQal magnetoelectrical stimulation of the motorcortex was performed (Magstim 200, Novametrix) at threshold intensity, and the peak latency of evoked SMU potentials measured. Recordings were obtained by small concentric needle
tients under anesthesia or drug intoxication, and with anoxic/ metabolic encephalopathiea When these conditions were excluded. GPSC indicated the diagnosis of subacute sclerosing panencephalitis (SSPE). Suppression bursts were noted in cases
electrodes (electrode surface: 0.015 mm) from 25 different SMU in the first dorsal interosseus (FDI) of 10 normal subjects. Activation of SMU occurred at mean latencies of 24.0-30.0 msec (range for all SMU: 23.5-30.6 msec; n = 25 SMU). The onset latency of the corresponding maximum CMAP as measured with surface electrodes over the FDI muscle belly was always shorter (mean difference: 3.9 msec). At repetitive stimulation SMU varied only slightly in latency. The average variability for all SMU was 0.4 msec ( f 1 SD) and the range of the variability for single units was 0.1-0.6 msec (f 1 SD). No significant groupings of SMU latencies and no double discharges of individual SMU were observed. Results were similar for SMU recruited either early or late in .relation to the CMAP. These observations in normal subjects may be due to a variation of synaptic transmission times rather than to excitation by various I-waves. In contrast preliminary results from MS patients show pronounced variability in latencies of SMU.
of deep sedation and of hypoxic encephalopathy. The outcomes of 125 patients with suppression bursts in the literature were assessed. Nine subjects under the effect of CNS depressant were excluded; of the remaining 116 patients, 111 died. A mortality of 96% indicates the grave prognostic importance of suppression bursts in cases of hypoxic encephalopathy. The GPSC pattern is not specific for the diagnosis of SSPE, but occurred in bromide intoxication and phencyclidine hydrochloride drug abuse. Generalized repetitive sharp transients were observed in patients with Creutzfeldt-Jakob’s disease and in those with anoxic encephalopathy causing cortical spongy changes. Generalized triphasic waves occurred only in patients with metabolic/anoxic encephalopathies. Six of our 8 patients died during the first 10 days following the recording. The other 2 patients improved temporarily, but died later from complications of their primary disease. This suggests that periodic triphasic waves are most often recorded in patients with irreversible metabolic encephalopathies. Periodic lateralized epileptiform discharges were associated with clinical seizures in 24/26 cases and were noted almost exclusively in destructive hemispheric lesions.
AMPLITUDE ASYMMETRY REVERSAL VEPs.
OF HEMI-FIELD
PAlTERN
EFFECT OF AGE, SEX AND HEAD SIZE ON PATTERN VEP.
Y. Kuroiwa and Y. Abe (Toranomon
Hospital,
Tokyo,
Japan) Y. Kuroiwa and K. Chiba
The amplitudes of transient and steady-state visual evoked potentials were measured during hem&field stimulation of the left eye in 10 healthy adults. Pattern reversal of a checkerboard was produced at 4 stimulation frequencies: 1, 5, 10 and 15 Hz. The amplitudes of pattern VEPs were evaluated using the paired r-test to determine significant differences between right and left her&fields. The transient VEP amplitudes from midoccipital, ipsilateral occipital and contralateral occipital electrodes were significantly greater with right hemi-field stimulation. The steady-state VEP amplitudes from mid-occipital electrode during 15 Hz stimulation were significantly greater with right hem&field stimulation. Our neurophysiological data may be compatible with neuro-anatomic asymmetries of occipital lobes in humans.
THE PROGNOSTIC NOMENA.
VALUE
OF PERIODIC
EEG
PHE-
Y. Kuroiwa and G.G. Celesia (Toranomon
Hospital,
Tokyo,
Japan)
Generalized and focal periodic EEG patterns were studied in 80 patients. Generalized periodic suppression bursts and generalized periodic slow-wave complexes (GPSC) occurred in pa-
(Toranomon
Hospital,
Tokyo,
Japan)
The subjects consisted of 167 healthy people (71 males, 96 females). Their mean age was 45.7+ 19.1 years. Full-field monocular stimulation was performed using three check sizes (15, 30 and 60 mm), at a rate of 1 Hz. Electrodes were placed 5 cm above the inion and 12 cm above the nasion. We measured (1) head circumference and height; (2) VEP latency (P50, N74, PlOO, N145); (3) VEP amplitude (P50-N75, N75-PlOO, PlOO-N145). Correlation analysis was done between latency and age, head size, or height; between amplitude and age, head size or height; between head size and age; between height and age; and between head size and height. The mean values were compared by r-test between the male and female groups with regard to age, head size, height, latency and amplitude. Mean VEP latency to 15 min checks was significantly longer than that to 30 or 60 min checks. Mean VEP amplitude to 15 min checks was significantly larger than that to 30 or 60 min checks. VEP latency showed a curvilinear relationship with age. VEP amplitude decreased with head size or height. The VEP in males showed a longer latency and a smaller amplitude than that in females. Linear regression analysis between head size or height and age showed a negative relationship. Normative data of the pattern VEP is affected by (1) biological factors, such as neuronal changes due to develop-