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Biomedical subjects

J K Penry

Publications and source records attributed to J K Penry.

At least 37 records · Page 2Linked to original sources
PubMed1989

The scope and use of valproate in epilepsy.

Valproate has rapidly advanced as an antiepileptic drug in the last 15 years. This simple branched-chain fatty acid is strikingly different from previous antiepileptic drugs. Numerous clinical studies have found valproate to be highly effective in controlling generalized seizures, particularly as monotherapy. Ideally, valproate is given in three to four doses per day, because the elimination half-life varies from 6 to 15 hours, depending on concomitantly administered drugs and metabolic variations. Increasing the dosage raises the peak serum level and also increases the duration of time during which a minimum effective serum concentration is obtained. Drug interactions occur when valproate is administered with other drugs, especially other antiepileptic drugs. Side effects attributed to valproate include tremor, weight gain, hair loss, hair growth, hepatotoxicity, and neural tube defects in offspring of mothers. Monitoring serum valproate concentrations and seizure frequency are essential aspects of patient follow-up.

Epilepsy↗
PubMed1989

Phenytoin and phenobarbital concentrations in serum: a comparison of Ames Seralyzer with GLC, TDX, and EMIT.

A recently developed system for measuring antiepileptic drug concentrations was evaluated for phenytoin and phenobarbital. The apoenzyme reactive immunoassay system was compared with gas-liquid chromatography, EMIT, and TDX systems. Comparisons were performed with control specimens and with sera obtained from patients at three facilities. Precision for all methods was similar, with within-run and between-run coefficients of variation generally 5%. The accuracy of all methods was acceptable, but bias was present in some. However, measurements obtained by a nontechnical person (physician) in a clinical setting were sometimes inaccurate.

Chromatography, Gas↗
PubMed1989

Evaluation of an enzyme immunochromatography method for carbamazepine: a comparison with enzyme-multiplied immunoassay technique, fluorescence polarization immunoassay, and high-performance liquid chromatography.

A noninstrumented enzyme immunochromatography (EIC) method for monitoring carbamazepine using whole blood was compared to the enzyme-multiplied immunoassay technique (EMIT), fluorescence polarization immunoassay (FPIA), and high-performance liquid chromatography (HPLC). Samples from 74 patients were evaluated in the comparison study, yielding correlation coefficients of 0.961 (EMIT), 0.974 (FPIA), and 0.867 (HPLC). The EIC method produced within-run coefficients of variation of 4.3%, 4.9%, and 5.8% for three carbamazepine concentrations. The between-run coefficient of variation over 107 days was 4.9%. The spiked serum sample analysis yielded recovery rates ranging from 98 to 102%. Enzyme immunochromatography was found to be a useful noninstrumented method for on-site testing. The test gives quantitative patient sample results comparable to the results obtained using established laboratory methods.

Adolescent↗
PubMed1988

Valproate monotherapy in partial seizures.

Results of a retrospective study in 30 patients indicate that, contrary to the findings of some earlier studies, valproate monotherapy is highly effective in the treatment of partial seizures, especially those that become secondarily generalized. In 22 of these 30 patients (73 percent), valproate monotherapy either abolished seizures (12 patients) or reduced their frequency by at least 51 percent (10 patients), whereas eight patients experienced minimal or no reduction in seizure frequency. All these patients had previously experienced treatment failure with carbamazepine, phenytoin, or phenobarbital--either alone or combined--because of lack of efficacy or unacceptable side effects. In these patients, failure to have a response to valproate therapy appeared to be related to the type of seizure (simple partial seizures alone/complex partial seizures alone, without secondarily generalized tonic-clonic seizures) and longer duration of uncontrolled seizures. Although these results cannot be generalized to all patients with partial seizures, they do indicate that a double-blind randomized trial of valproate in patients with all types of partial seizures is warranted.

Adolescent↗
PubMed1987

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.

Aminocaproates↗
PubMed1987

Magnetic resonance imaging and complex partial seizures.

Magnetic resonance imaging (MRI) is a new imaging modality with potential usefulness in the evaluation of patients with seizure disorders. We studied 100 consecutive patients with complex partial seizures comparing computerized cranial tomography (CCT) with MRI. Our study revealed 36 patients with CCT abnormalities. Of these, 30 (83%) had focal abnormalities. MRI demonstrated 45 patients with abnormalities, 34 (76%) were focal. Intracranial calcifications were not visualized by MRI, but were easily demonstrated by CCT. MRI was more sensitive in visualizing cerebral atrophy, abnormal cerebral vasculature, and lesions in the posterior fossa and suprasellar region. Most importantly, several patients who had normal CCTs had abnormal MRIs consistent with neoplastic lesions. As MRI becomes more available, this imaging modality along with EEG, should be the studies of choice in evaluating patients with partial epilepsy.

Adolescent↗
PubMed1986

Driving impairment caused by episodic brain dysfunction. Restrictions for epilepsy and syncope.

The potential loss of driving privileges is a major concern of patients with epilepsy and other episodic brain illness. The extreme variation from state to state in reporting requirements and the duration of restrictions illustrate the legal ramifications of uncertain medical advice. We studied the reliability of various methods of predicting recurrences, including electroencephalograms, familial data, and epidemiologic data and concluded that we should offer more flexible, detailed guidelines. These ought to encourage regulators, colleagues, and patients and would perhaps increase highway safety through better compliance. Episodic changes in cognition unrelated to epilepsy or syncope remain a quagmire. When the most reliable risk factors are listed in tabular form, the result appears complex, but such a guideline should be fairer, easier to administer, and often more lenient than the present simplistic, arbitrary codes found in most states.

Accidents, Traffic↗
PubMed1984

Paradoxical contributions of EEG during protracted dying.

Estimates of the potential for recovery from severe brain damage have become more accurate as EEG and imaging techniques evolve. When all modern electrical criteria for brain death are satisfied, useful recovery is probably impossible. Many patients who have no reasonable chance of returning to a cognitive, sapient, or useful state may be nurtured throughout a prolonged final illness primarily because of brain waves that fluctuate in the 2- to 5-microV range. The incidence of such protracted dying is unknown. We illustrate diffuse low-amplitude wave forms and regional fragments recorded from a 27-year-old woman maintained on a respirator for six months after loss of brain-stem reflexes. Considering the limited noise-signal ratio of modern equipment, popular EEG criteria for death may be prematurely rigid, prolonging death in tragic circumstances.

Brain Death↗
PubMed1984

Some clinical and EEG aspects of benign juvenile myoclonic epilepsy.

Twelve patients with benign juvenile myoclonic epilepsy (BJME) representing 4% of our population of epileptics (n = 275) are presented. Only two patients (17%) had myoclonic jerks as the only seizure type. Seven (58%) had generalized tonic-clonic seizures (GTCS) and myoclonus. Three patients (25%) had absence seizures (AS), GTCS, and myoclonic jerks. Electroencephalographic evidence of photosensitivity was found in four (33%). Auditory precipitation of seizures was found in one patient. As is the case with other primary generalized epilepsies, the onset of BJME seems to be age specific. In our series the mean age of onset in years was 4.3 for AS, 14.75 for myoclonic jerks, and 16.4 for GTCS. It took an average of 8.5 years from the onset of BJME (range, 2-20 years) and 6.5 years from the onset of GTCS (range, 2 months-6 years) until the condition was properly recognized. Five patients experienced at least one episode of myoclonic status epilepticus. Generalized, paroxysmal, symmetric polyspike and slow wave discharges are the typical EEG finding. These complexes, however, showed considerable interpatient variability. Sleep deprivation proved to be the most valuable activating procedure. Valproic acid monotherapy effectively controlled myoclonic jerks as well as associated GTCS in most patients.

Adolescent↗
PubMed1984

Disposition of mephenytoin and its metabolite, nirvanol, in epileptic patients.

We investigated the conversion of mephenytoin to nirvanol in five patients with uncontrolled complex partial seizures. After a 50-mg single oral dose, mean peak mephenytoin level was 0.48 microgram/ml and nirvanol 0.37 microgram/ml. After 400 mg, peak mephenytoin level was 3.9 micrograms/ml and nirvanol 2.5 micrograms/ml. On 400 mg daily, mephenytoin reached a mean steady-state level of 1.5 micrograms/ml. Nirvanol mean steady-state level was 18 micrograms/ml. Mean plasma half-life was 17 hours for mephenytoin and 114 hours for nirvanol. Two patients had reduced seizures during mephenytoin therapy and one a transient increase during drug withdrawal. No toxicity was seen, but mephenytoin was not more effective than phenytoin.

Adolescent↗
PubMed1983

Clinical and EEG estimates of absence seizure frequency.

Absence seizure frequency was estimated in 20 patients (5 to 15 years old) before and after treatment with ethosuximide. Estimates were obtained from mothers' histories, observations by nurses, intensive observation by trained observers, physical and neurological examinations, routine EEG, and 12-hour telemetered EEG. Both before treatment (high seizure frequency) and after treatment (low frequency), telemetered EEG was the most reliable method of estimation, and intensive observation was the next best method. After treatment, the mothers' and nurses' estimates of seizure frequency were significantly less than the telemetered EEG estimates. The neurological examination and routine EEG were sufficient to diagnose absence attacks in all 20 patients and to determine if the attacks were completely controlled by therapy in all but two patients.

Adolescent↗
PubMed1983

Long-term follow-up of absence seizures.

The prognosis of absence seizures was evaluated in 83 patients by univariate and multivariate analysis. The mean follow-up period was 9.5 years. Normal intelligence quotient (IQ) was found to be a significant prognostic factor by both methods of analysis, but multivariate analysis showed that normal IQ, no hyperventilation-induced spikes and waves, male sex, and normal neurologic findings were significant prognostic factors associated with cessation of all types of seizures. More than 90% of patients with three or more significant factors stopped having seizures. A multiple logistic regression model describes the population and can be used for estimating the outcome of patients with absence seizures.

Adolescent↗
PubMed1983

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.

Adolescent↗
PubMed1983

Complex partial seizures: clinical characteristics and differential diagnosis.

Videotape analysis of 163 complex partial seizures in 40 patients showed that the mean duration of the attack was 128 seconds. Automatisms occurred in 159 seizures (97%) and involved more than the face and arms in 132 (80%). Most automatisms were simple, stereotypic, or aimless movements. Postural tone increased in 24 seizures and decreased in 62. Clonic movements of the eyelids occurred in 19 attacks, and clonic movements of the extremities in 4. Only nine patients reported auras. Distinct ictal and postictal phases could be distinguished in 132 seizures (80%); in these, the mean ictal duration was 54 seconds and the mean postictal duration 89 seconds. Videotape analysis provides objective criteria by which complex partial seizures may be differentiated from other seizure types.

Adolescent↗
PubMed1983

Petit mal status.

Petit mal status is a heterogeneous clinical syndrome of nonconvulsive status epilepticus. The EEG accompaniment is likewise heterogeneous. Petit mal status occurs at all ages. The characteristics of this syndrome are quite nonspecific and consist of (a) behavioral changes, usually associated with lethargy, slowness, and decreased mental function, (b) abnormal generalized continuous or nearly continuous epileptiform EEG activity, and (c) absence of gross tonic-clonic activity or highly lateralized clonic activity. These criteria do not distinguish petit mal status from complex partial status. Clinical evidence for abruptness of recovery and EEG evidence for localization are required for this distinction, an important factor in therapeutic decisions.

Adolescent↗
PubMed1982

Psychogenic seizures. A study of 42 attacks in six patients, with intensive monitoring.

Intractable complex partial seizures and seizures of unknown type were studied in 78 patients, six of whom were found to have psychogenic seizures. Evaluation by intensive monitoring included simultaneous six-hour telemetered EEG and videotape recordings and daily determination of plasma antiepileptic drug levels. Diagnosis was determined by assessment of four major criteria: deviation of seizures from characteristics of known seizure types, absence of epileptiform activity in the ictal EEG, absence of slowing in the postictal EEG, and relation of seizure frequency to decreasing plasma concentrations of antiepileptic drugs. No single criterion is sufficient for an unequivocal diagnosis of psychogenic seizures.

Adult↗