Andrew J. Gabor

Treatment of status epilepticus A prospective comparison of diazepam and phenytoin versus phenobarbital and optional phenytoin

In a randomized, nonblinded clinical trial, 36 consecutive patients with generalized convulsive status epilepticus were treated with either combination diazepam and phenytoin (DZ/DPH) or phenobarbital (PB). Phenytoin was added to the PB regimen if seizures persisted for 10 minutes after beginning therapy. The cumulative convulsion time (total time spent in active convulsive movements) was shorter for the PB group than for the DZ/DPH group (median, 5 versus 9 minutes, p < 0.06); the response latency (elapsed time from initiation of therapy to the end of the last convulsion) was also shorter for the PB group (median, 5.5 versus 15 minutes, p < 0.10). The median cumulative convulsion time is between 0 and 14 minutes shorter for the PB regimen than for the DZ/DPH regimen (95% confidence interval). Similarly, the median response latency for the PB regimen is between 1 minute longer and 20 minutes shorter than that for the DZ/DPH regimen (95% confidence interval). The frequencies of intubation, hypotension, and arrhythmias were similar in the two groups. Eleven of 18 patients in the PB group responded to phenobarbital monotherapy. We conclude that the PB regimen is rapidly effective, comparable in safety, and enjoys certain practical advantages in comparison with the DZ/DPH regimen.

Seizure detection using a self-organizing neural network: validation and comparison with other detection strategies

OBJECTIVE A previously described seizure detection algorithm (CNET) (Gabor, A.J., Leach, R.R. and Dowla, F.U. Automated seizure detection using a self-organizing neural network. Electroenceph. clin. Neurophysiol., 1996, 99: 257-266) was validated with 200 records from 65 patients (4553.8 h of recording) containing 181 seizures. DESIGN AND METHODS Performance of the algorithm was manifest by its sensitivity ((seizures detected/total seizures) x 100) and selectivity (false-positive errors/Hr-FPH). Comparisons with the Monitor detection algorithm (Version 8.0c, Stellate Systems) and audio-transformation (Oxford Medilog) were performed. RESULTS CNET detected 92.8% of the seizures and had a mean FPH of 1.35 +/- 1.35. Monitor detected 74.4% of the seizures and had a mean FPH of 3.02 +/- 2.78. Audio-transformation detected all but 3 (98.3%) of the seizures. Selectivity for this detection strategy was not defined. CONCLUSIONS This study not only validates the CNET algorithm, but also the notion that seizures have frequency-amplitude features that are localized in signal space and can be selectively identified as being distinct from other types of EEG patterns. The ear is a specialized frequency-amplitude detector and when the signal is transformed into audio frequency range (audio-transformation), seizures can be detected with better sensitivity as compared to the other strategies examined.

Seizure detection: evaluation of the Reveal algorithm

OBJECTIVE The aim of this study is to evaluate an improved seizure detection algorithm and to compare with two other algorithms and human experts. METHODS 672 seizures from 426 epilepsy patients were examined with the (new) Reveal algorithm which utilizes 3 methods, novel in their application to seizure detection: Matching Pursuit, small neural network-rules and a new connected-object hierarchical clustering algorithm. RESULTS Reveal had a sensitivity of 76% with a false positive rate of 0.11/h. Two other algorithms (Sensa and CNet) were tested and had sensitivities of 35.4 and 48.2% and false positive rates of 0.11/h and 0.75/h, respectively. CONCLUSIONS This study validates the Reveal algorithm, and shows it to compare favorably with other methods. SIGNIFICANCE Improved seizure detection can improve patient care in both the epilepsy monitoring unit and the intensive care unit.

Periodic lateralized epileptiform complexes (PLEDs) in Creutzfeldt‐Jakob disease

The electroencephalogram (EEG) of three patients with typical Creutzfeldt-Jakob disease (CJD) was characterized by periodic lateralized epileptiform complexes (PLEDs), which persisted and became bilateral. This unusual pattern preceded the characteristic EEG change of CJD. Persistence of PLEDs should suggest the diagnosis of CJD.

Intracranial pressure during epileptic seizures.

A comatose 31-year-old male with presumed viral encephalitis and frequent partial motor seizures was paralyzed with pancuronium in an attempt to reduce recurrent elevation of intracranial pressure (ICP) associated with each seizure. ICP was continuously monitored with a Richmond Bolt and 5 electrographic seizures originating in the left frontal area were recorded. Each ictal episode was associated with stable blood pressure and an increase of ICP. The average seizure duration was 78 +/- 17 sec (mean +/- S.D.) and the average maximum increase of ICP above baseline during the seizures was 6.5 +/- 0.6 mm Hg with average peak ICP of 16.0 +/- 0.86 mm Hg. A simple mathematical model predicts the rate of increase of ICP, the peak ICP, the phase difference between maximum spike frequency and maximum ICP, and the rate at which ICP returns to pre-ictal values after termination of the seizure. The predicted values of ICP closely approximate the experimentally derived data. Therefore, the time course of the ICP appears to be determined by the frequency of the fundamental units of abnormal synchronized activity (the epileptogenic spike) and the CSF pressure-volume dynamics existing at the time of the seizure. An average increment of ICP per spike can be calculated for each seizure. The model also predicts that patients may develop high ICPs due to prolonged seizures. Prolonged unrecognized seizures may occur in patients who are therapeutically paralyzed as demonstrated by the case described here.

The human posterior tibial somatosensory evoked potential: Synapse dependent and synapse independent spinal components

Evidence has been obtained for the existence of two separate events occurring in the human spinal cord following posterior tibial nerve (PTN) stimulation. These events can be recorded on the surface in unanesthetized individuals. The first is an ascending wave which is conducted up to the cord at constant velocity and has a relatively short refractory period consistent with a compound nerve action potential. This represents the afferent volley traversing the lumbosacral plexus and the ascending dorsal columns. A second event, the N22/P22 complex, is surface negative on the back and surface positive anteriorly; its amplitude is maximal 5-15 cm above the level of the L4 spine and its peak latency remains constant at all levels. This activity has a relatively long refractory period. These characteristics of N22/P22 indicate that it is a localized synaptically dependent event conforming to a transverse dipole with dorsal negativity and a simultaneous anterior positivity. The N22/P22 is probably generated in the dorsal grey at the root entry zone. The N22/P22 is analogous to the stationary N13/P13 recorded over the neck following median nerve stimulation.

Effect of movement on human spinal and subcortical somatosensory evoked potentials

Sensory transmission in dorsal column nuclei is inhibited during voluntary movement in experimental animals. We have studied the human response by recording spine and scalp somatosensory evoked potentials. Finger movement attenuated the amplitude and duration of the cervical N13 and the scalp N18 and N20 waves. Foot movement did not alter the lumbar N22 after foot stimulation, but the scalp P38 was attenuated. N22 results solely from activation of interneurons in the dorsal gray of the cord at the root entry zone, but N13 may receive contributions from the nucleus cuneatus. Therefore, the movement-induced attenuation of N13 is attributed to decreased contribution from the nucleus cuneatus.

Enhancement of the amplitude of somatosensory evoked potentials following magnetic pulse stimulation of the human brain

In this study we have demonstrated an enhancement of cortically generated wave forms of the somatosensory evoked potential (SEP) following magnetic pulse stimulation of the human brain. Subcortically generated activity was unaltered. The enhancement of SEP amplitude was greatest when the median nerve was stimulated 30-70 msec following magnetic pulse stimulation over the contralateral parietal scalp. We posit that the enhancement of the SEP is the result of synchronization of pyramidal cells in the sensorimotor cortex resulting from the magnetic pulse.

Movement‐induced seizures in nonketotic hyperglycemia

We studied two patients with hyperglycemia and focal seizures induced by repetitive movement. Treatment of the hyperglycemia controlled the seizures. Early diagnosis is necessary for institution of appropriate therapy, and to decrease the morbidity associated with nonketotic hyperglycemic coma, which may evolve.

Paroxysmal genital pain: An unusual manifestation of epilepsy

A male patient who is now 15 years old has experienced a seizure disorder since age 9 years. The seizures were expressed as episodes of excruciating pain localized to the genital region. Appropriate anticonvulsant medication has controlled both pain and seizures.