Vigabatrin for refractory complex partial seizures: multicenter single-blind study with long-term follow-up

The irreversible GABA transaminase inhibitor vigabatrin (VGB) was given in a single-blind fashion to 89 patients with complex partial seizures (CPS) refractory to conventional drugs. The median number of CPS per month decreased from 11.0 to 5.0 after addition of VGB, and 51% of patients had a 50% or greater decrease in CPS frequency (p less than 0.001). Side effects (principally drowsiness, ataxia, and headache) occurred mainly during the initiation of therapy and decreased during therapy. After 12 weeks on VGB, side effects significantly interfered with functioning in only 13% of patients, and the efficacy:toxicity ratio warranted continued administration in 74% of patients. Coadministration of VGB resulted in a mean decrease of 20% in phenytoin serum concentration (p less than 0.001). Sixty-six patients with a favorable response to VGB during the single-blind study have been followed for a median of 16.7 months on VGB. No serious systemic or neurologic toxicity has been detected, and most patients have retained their initial favorable CPS control.

Cholinergic modulation of human P3 event-related potentials

A paradigm for studying relations between behavioral, neurochemical, and electrophysiologic processes is presented. Scopolamine, a centrally acting anticholinergic agent, abolished the human auditory P3 event-related potential, but had no measurable effect on the pattern reversal visual evoked potential or alpha rhythm. Recent memory was significantly impaired, but assessment of digit span, reaction time, and distant memory showed no impairment. Physostigmine, an anticholinesterase, restored the P3 and reversed the recent memory impairment. These results strongly suggest a cholinergic role in generation of P3 potential and support the concept that P3 generation is related to memory processes.

Neuropharmacology of zonisamide, a new antiepileptic drug

Zonisamide readily crosses the blood-brain barrier and is readily absorbed after oral administration with a Tmax of about 3 hr. The half-life of ZNA in epileptic patients is about 28 hr. Zonisamide has a broader therapeutic range than other antiepileptic drugs. Neurotoxic, hemapoietic, renal, and liver effects have been minimal in patients participating in controlled clinical studies. It is effective in several experimental models of epilepsy and in initial clinical trials has been shown to be effective in generalized tonic-clonic, simple, and complex partial seizures.

Procedures requiring signed consent. A survey of practice

Despite extensive discussion of informed consent within the medical and legal literature, those diagnostic or therapeutic procedures which may specifically require written consent remain poorly identified. Survey results from 105 JCAH-approved hospitals show that 56 percent set forth a general policy statement regarding when and for which procedures consent is needed. The remaining hospitals specify individual procedures for which signed authorization is required by the hospital or medical staff guidelines. The potential liability, advantages and disadvantages of a general versus specific consent practice are discussed. A listing of those procedures itemized by responding hospitals from this national survey is also presented.

Quality assessment of tetanus prophylaxis in the wounded patient

New guidelines on tetanus prophylaxis in wound management have been prepared by the American College of Surgeons and are available in a poster format or in bulletins. The purpose of this study was to determine the impact of these educational brochures on tetanus prophylaxis in a hospital setting. The results of this study indicate that these informational brochures and posters had insignificant impact on the quality of prophylaxis against tetanus in our hospital. Innovative programs of information exchange and quality assurance are urgently needed to improve the delivery of health care.

Effect of gamma-vinyl GABA on human pattern evoked visual potentials

We studied the effects on human visual evoked potentials of gamma-vinyl GABA, an anticonvulsant drug that increases cerebral levels of gamma-aminobutyric acid. The subjects were 15 epileptic patients undergoing a clinical trial of this drug. Serial recordings were made from each patient periodically for 1 year. The stimulus was a reversing checkerboard pattern with a check size of 50 minutes. Plasma levels of other antiepileptic medications remained constant throughout the study. No changes, other than a normal variation of +/- 5 msec, were observed in peak latency throughout the study. These results indicate that there are no GABA-ergic effects on the P100 component evoked by large checkerboard pattern-reversal.

Effects of gamma-vinyl-GABA on the human electroencephalogram

Gamma-vinyl-GABA (GVG) is a new anticonvulsant drug that significantly raises the level of the gamma-aminobutyric acid in the brain (GABA). The effects of gamma-vinyl-GABA on the human electroencephalogram were studied to assess the role of GABAergic mechanisms on electrocortical activity. Serial EEGs were recorded in 15 epileptic patients undergoing a controlled clinical trial of gamma-vinyl-GABA. The effects of gamma-vinyl-GABA on alpha, beta, or theta activity, sleep spindles and epileptiform activity were studied. No changes could be detected in any of the intrinsic brain rhythms. Three patients showed a mild amelioration of epileptiform activity; no increase in epileptiform activity was seen.

Auditory brain-stem potentials with unilateral pontine hemorrhage

Although there have been extensive anatomical and physiological studies in animals, the actual neural sources, or even the laterality, of some components of auditory brain-stem evoked potentials in humans are uncertain. We studied these responses in a 56-year-old patient who had a clearly demarcated pontine hemorrhage on the right side. The patient was somnolent, with dense left hemiplegia and signs of involvement of right cranial nerves V, VI, and VII. Stimulation of the left ear (ie, contralateral to the lesion) evoked a normal series of waves with clearly resolved positive components peaking at 2.0, 3.3, 4.8 (wave IV), and 6.0 ms (wave V). Stimulation of the right ear (ie, ipsilateral to the lesion) evoked only waves I, III, and IV. These results suggest that a pathway ipsilateral to the stimulated ear is necessary and sufficient for generation of auditory wave V and that wave IV is generated in bilateral pathways.

Bedside resuscitation bags: a source of bacterial contamination

Resuscitation bags at the bedside of 12 intubated ICU patients with known culture positive sputum were evaluated as possible reservoirs of pathogenic bacteria. As oxygen was constantly flowing into the bags, sampling of gas continuously emitted from the exhalation valve assembly was sampled to detect if a bacteria-laden aerosol was being created. Positive cultures were obtained from 75% of the valves and 25% of the aerosol samples. In those patients with gram-negative bacteria in their sputum, 71% of the valves and 29% of the gas samples were positive for the same organisms. Various methods to control this possible contributing factor to nosocomial infection in the ICU are discussed.

Enhanced auditory postauricular evoked responses after corticobulbar lesions

The auditory postauricular response is an evoked "microreflex" that is generated in the posterior auricular muscle. This potential, which has two prominent components at latencies of 12 and 16 msec, is best recorded with neck extensor or facial muscles under tension, but it is not recorded if scalp muscles are relaxed. We describe markedly enlarged postauricular responses after upper motor neuron lesions above the foramen magnum.

Selenium, zinc, and copper changes with valproic acid: possible relation to drug side effects

Side effects of treatment with the anticonvulsant valproic acid (VPA) suggested the possibility of alteration of trace metal status. Administration of VPA for 1 week produced significant depletion of zinc and selenium in plasma of rats and a one-third reduction of hepatic selenium. Patients who were treated chronically, with VPA as the sole anticonvulsant medication, had decreased plasma selenium levels. Most cases of VPA-associated hepatotoxicity occur in children. This could be due to decreased selenium concentrations when mechanisms for protection against peroxidative damage are not fully developed.

Comparison of valproic acid and phenytoin in newly diagnosed tonic-clonic seizures

Sixty-one newly diagnosed epileptic patients with generalized tonic-clonic, clonic, or tonic seizures were randomly allocated to treatment with valproate (VPA) and phenytoin (PHT). After 6 months, both drugs had been effective in preventing recurrence of seizures. Seventy-three percent of patients receiving VPA and 47% of patients receiving PHT had no recurrences. Side effects of either drug were mild. Laboratory abnormalities were similar for both drugs. Except for one PHT patient with toxic hepatitis, therapy was not discontinued.

"Baltic" myoclonus epilepsy: hereditary disorder of childhood made worse by phenytoin

A survey of 15 families in the USA with Baltic myoclonus epilepsy showed that the 27 individuals who were affected had the following clinical picture from about the age of 10: photosensitive, occasionally violent, myoclonus, usually worse upon waking; generalised tonic-clonic seizures, sometimes associated with absence attacks; and light-sensitive, generally synchronous, spike-and-wave discharges on EEG that preceded clinical manifestations. Necropsy revealed marked loss of Purkinje cells of the cerebellum, but no inclusion bodies. Since the disease was confined to sibs and consanguinity was present in two families, autosomal recessive inheritance is probable. The disease progressed more rapidly in these families than it did in the early cases, seen in the Baltic region. This difference could be due to a toxic effect of phenytoin because phenytoin given alone or with other antiepileptic drugs was associated with progressive motor and intellectual deterioration, marked ataxia, and even death. Treatment with valproic acid, and the concomitant reduction or elimination of phenytoin, has been associated with marked improvement in at least 8 patients. Baltic myoclonus epilepsy must be distinguished from Lafora body disease, which is invariably fatal and discernible on clinical grounds.

Treatment of valproate tremors

Chronic valproate therapy induces symptomatic tremor in about 10% of patients. We studied the effects of propranolol, amantadine, diphenhydramine, benztropine, and cyproheptadine on these tremors in 19 patients by using serial accelerometric recordings. Propranolol was clearly the most therapeutic. Amantadine was moderately effective, but cyproheptadine, diphenhydramine, and benztropine gave little or no relief.

Twice-daily dosing of valproate with divalproex

Equivalent doses of enteric-coated divalproex were substituted for valproic acid in 15 epileptic patients who were on a three- or four-times-a-day dosing schedule. After 2 wk the dosing regimen was changed to twice-daily divalproex dosing, and plasma levels were determined during the 12-hr period after the morning dose. Peak absorption was reached at 4 hr; extended plateaus were noted thereafter. The mean fluctuation between low and high plasma values for the group was 46%, with a decrease of less than 50% of peak levels in 9 of the 15 patients at a sampling time just before the second dose. Breakthrough seizures did not occur as a result of twice-daily dosing.

A double-blind study comparing carbamazepine with phenytoin as initial seizure therapy in adults

Carbamazepine was compared with phenytoin in a double-blind study. Of 87 patients, data on 70 patients were complete and used for analysis. Thirty-five patients were treated with each drug. The incidence of major side effects, minor side effects, and complete control (85%) was the same in both groups. A mild but significant elevation of WBC count was found before initiation of drug treatment in the patients presenting with generalized convulsive seizures. Sporadically, elevations in SGOT and LDH were seen; WBC counts below 4,000 were reported, but these were not clinically significant.

Evoked potentials in olivopontocerebellar atrophy

Pattern-reveral visual evoked potentials, far-field and cortical somatosensory evoked potentials, and auditory brainstem potentials were recorded in two patients with olivopontocerebellar atrophy. In one patient, visual evoked potentials exhibited prolonged latency and interocular latency differences in the absence of clinical visual dysfunction. Median and tibial nerve evoked cortical potentials were severely attenuated in the absence of somatosensory deficit or peripheral nerve slowing. The far-field somatosensory potentials, however, were well preserved. All components of the auditory brain-stem potentials had latencies within normal limits. In the other, more severely afflicted, patient, all visual, somatosensory, and auditory evoked potentials were abnormal.

Gastrointestinal tolerance of divalproex sodium

Divalproex sodium (DS), a new enteric-coated preparation of valproate, was administered to 27 patients who had not tolerated valproate because of gastrointestinal symptoms. Twenty-three (85%) tolerated DS and continued therapy. Of 34 patients previously naive to valproate, DS therapy was discontinued in only 4 patients (12%) because of gastrointestinal intolerance. Enteric-coated DS tablets had fewer gastrointestinal effects than VA capsules. Although the absorption of DS was delayed, the bioavailability of VA capsules and DS tablets was equivalent. After oral doses, peak plasma levels occurred within 1 hour with VA and at 3 hours with DS. Seven patients were maintained on a twice-daily schedule of DS.

Immunofluorescent evidence for a specific binding site for phenytoin in the cerebellum

The regional distribution of phenytoin in the brains of experimental animals was studied using the indirect fluorescent antibody technique. Using antibodies directed against phenytoin, we observed a specific pattern of staining the Purkinje and granule cell layers of the cerebellum. An identical pattern of staining was seen in phenytoin-treated and untreated animals. Several control procedures and studies indicated that the observed pattern was not caused by nonspecific staining or autofluorescence. The distinctive staining pattern obtained using this technique can be attributed to the high molecular specificity of antigen-antibody reactions and a discrete binding site for phenytoin in the vicinity of cerebellar Purkinje and granule cells.

The effect of diphenylhydantoin (phenytoin) on the sequential stages of intestinal folate absorption

The drug diphenylhydantoin (phenytoin) (DPH) is thought to interfere with the bioavailability of dietary folate through an effect on intestinal folate deconjugation and/or monoglutamate folate transport. In order to determine whether DPH inhibition occurs in the sequential steps of folate deconjugation, uptake, or reduction-methylation, the effect of the drug on the intestinal absorption of hexaglutamate folate (PteGlu6), pteroylmonoglutamate folate (PGA), and N-5-methyltetrahydrofolate (CH3FH4) was studied. Folate absorption was directly quantified by the method of triple lumen tube perfusion in 12 subjects serving as their own controls. All 12 received PGA mixed with and without DPH (20 micrograms/ml), while 6 of the 12 subjects received hexaglutamate and 6 received reduced methylated folate with and without added DPH. With this model DPH was shown not to impair significantly folate absorption by any action upon the process of folate deconjugation, absorption, or reduction-methylation. The previously reported association between DPH intake and reduced levels of serum folate remains unexplained by these studies.