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R J Porter

Publications and source records attributed to R J Porter.

At least 37 records · Page 2Linked to original sources
PubMed1994

Postictal behavior. A clinical and subdural electroencephalographic study.

OBJECTIVE: To examine postictal behaviors after temporal lobe complex partial seizures (CPSs) and to correlate these behavioral phenomena with side of origin and ictal spread pattern. DESIGN: Review language and other behavioral phenomena after seizures defined by subdural electroencephalography. SETTINGS: A surgical epilepsy center. PATIENTS: We studied postictal behavior following 65 CPSs in 18 patients with left hemisphere language dominance using subdural electrode recordings. INTERVENTION: Subdural electrodes. MAIN OUTCOME MEASURES: Language function, affect, orientation, and postictal automatisms. RESULTS: Following the CPS ictal discharge, the mean interval for initial nonreflexive response to an environmental stimulus was 43 seconds (left foci, 57 seconds; right foci, 29 seconds; not significantly) and for first correct verbal response was 219 seconds (left foci, 275 seconds; right foci, 167 seconds; not significant). Impaired comprehension with fluent but unintelligible speech, as well as anomia, occurred after seizures arising from either temporal lobe. All nine seizures followed by global or nonfluent aphasia originated on the left side. Paraphasic errors were significantly more common after left temporal CPSs. Prolonged disorientation for place and flat affect were significantly more common after right temporal CPS. Postictal automatisms were frequent and included rubbing of the face, fumbling and picking hand movements, and repetitive oral movements. CONCLUSIONS: Postictal paraphasias, disorientation for place, and flat affect most likely reflect the functions of the area from which seizures arise but not the areas involved by spread.

Adolescent↗
PubMed1994

The secondarily generalized tonic-clonic seizure: a videotape analysis.

We studied 120 generalized tonic-clonic seizures (GTCSs) in 47 patients with video-EEG telemetry. GTCSs were preceded by antecedent seizures, including 13 simple partial, 70 complex partial, 17 simple partial leading to complex partial, seven tonic, seven clonic, and one typical absence. We divided GTCSs into the following phases: onset of generalization, pretonic clonic, tonic, tremulousness, and clonic. The mean GTCS duration was 62 seconds. There was a non-significant trend toward longer duration on reduced antiepileptic drug doses. Marked heterogeneity in GTCS phenomenology was present; only 27% of seizures included all five phases. Individual phase duration and clinical expression, including tonic and clonic phases, was highly variable. The clinical phenomena suggest that multiple cortical and subcortical routes of spread may exist. When GTCSs last longer than 2 minutes, intravenous antiepileptic drug treatment should be initiated.

Adolescent↗
PubMed1993

New developments in the search for improved antiepileptic drugs.

Recent advances in neurobiology have yielded clues about the abnormal physiology of epilepsy and a better understanding of the action of the established anticonvulsants, which were discovered fortuitously or in animal screening tests. Some newer antiepileptic drugs may represent an important improvement over existing therapy, especially if they show efficacy in patients with intractable seizures or fewer limiting neurological side effects. Many developmental agents are designed to interact with a specific target and employ one of three strategies: enhancement of central inhibition; diminution of central excitation; or modulation of ionic channels regulating neuronal excitability. This article reviews the anticonvulsant compounds in development, with a focus on those being investigated in man. Updated information is also provided about the mechanisms of action of the antiepileptic drugs presently used as first line therapy.

Animals↗
PubMed1993

The absence epilepsies.

Four syndromes comprise the absence epilepsies. Each is classically associated with the absence seizure, although other syndromes also have absence attacks as part of their repertoire. The most common syndrome is childhood absence epilepsy; it usually occurs in the age range of 6-7 years. The absence seizures may occur many times daily, and the electroencephalographic (EEG) characteristics are the most typical of the absence epilepsies. The second form of absence epilepsies is juvenile absence epilepsy; it begins near puberty and may represent a continuum from the childhood form. Myoclonic seizures are more common than in the childhood form, and the spike-wave discharges in the EEG are often faster than that seen in childhood absence epilepsy. The third form of absence epilepsy is juvenile myoclonic epilepsy, characterized especially by myoclonic jerks in the morning; these attacks occasionally progress to generalized tonic-clonic seizures. The final form of absence epilepsy is epilepsy with myoclonic absences, a rare disorder with a specific form of absence seizures. The absence seizure itself is observed to a greater or lesser extent in all of these syndromes. This seizure is a curious event, and its causes are poorly explained by current knowledge of the fundamental mechanisms of the epilepsies. Although the etiology of the absence seizure at a biochemical level is unknown, some studies suggest that certain low-threshold calcium ion currents (T currents), which are partially controlled by GABA-B mechanisms, may activate burst firing of thalamic neurons, initiating an absence seizure. The evidence of a genetic predisposition for the absence epilepsies is overwhelming.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Antiepileptic drugs: future development.

The development of new compounds for seizure disorders has moved from serendipity to screening to newer, more rational approaches. We are entering an exciting era, with the advent of novel drugs that may have a profound effect on the manner in which we treat patients with epilepsy.

Animals↗
PubMed1992

New antiepileptic drugs: from serendipity to rational discovery.

Antiepileptic drug discovery has made enormous progress from the serendipity and screening processes of earlier days to the rational drug development of today. The modern era of research began with the recognition that enhancement of inhibitory processes in the brain might favorably influence the propensity for seizures, gamma-aminobutyric acid (GABA) being the main inhibitory transmitter. Work in this field led to the development of vigabatrin, which inhibits the enzyme responsible for the degradation of GABA. More recently, research has focused on the therapeutic potential of blocking excitatory amino acids--in particular glutamate. Of the three receptors for glutamate, the N-methyl-D-aspartate (NMDA) receptor is considered the one of most interest in epilepsy, and research on a series of competitive NMDA receptor antagonists--especially those that are orally active--is in the forefront of antiepileptic drug development today. A further alternative for diminishing neuronal excitability is to modulate sodium, potassium, or calcium channels. The latter are especially implicated in absence seizures.

Animals↗
PubMed1992

Current medical therapy of epilepsy.

The treatment of epilepsy firstly depends upon the correct diagnosis, with emphasis on considerations of etiology, seizure type, and epilepsy syndrome. Following an appropriate diagnostic conclusion, the patient may be started on the medication matched to the seizure type. A full understanding of the pharmacology of antiepileptic drugs will enable the physician to obtain maximum benefit from the available pharmaceutical armamentarium.

Anticonvulsants↗
PubMed1991

A case of mosaicism involving an unstable 13/14 Robertsonian translocation.

Prenatal diagnosis of mosaicism involving an apparently unstable 13/14 Robertsonian translocation is reported. This illustrates the difficulties encountered in counselling when mosaicism is ascertained prenatally. Other reported examples of apparently unstable Robertsonian translocations are discussed.

Adult↗
PubMed1991

Disorders of consciousness and associated complex behaviors.

Behavioral events during epileptic seizures, while varied, comprise only a portion of the total spectrum of human behavior. Studies using intensive video monitoring have permitted insight into the common and uncommon events in epileptic seizures. Comparison of data from these studies with data from other disorders, notably psychiatric disease, allows a more complete understanding of the nature of these disorders and of the differential diagnosis of each. Disorders in which consciousness is altered are common and heterogeneous; it is now possible to differentiate these various disorders. The information presented here provides a framework for the physician confronted with these diagnostic dilemmas.

Behavior↗
PubMed1991

Different phase-stable relationships of the upper lip and jaw for production of vowels and diphthongs.

Relational invariants have been reported in the timing of articulatory gestures across suprasegmental changes, such as rate and stress. In the current study, the relative timing of the upper lip and jaw was investigated across changes in both suprasegmental and segmental characteristics of speech. The onset of upper lip movement relative to the vowel-to-vowel jaw cycle during intervocalic bilabial production was represented as a phase angle, and analyzed across changes in stress, vowel height, and vowel/diphthong identity. Results indicated that the relative timing of the upper lip and jaw varied systematically with changes in stress and vowel/diphthong identity, while remaining constant across changes in vowel height. It appears that modifications in relative timing may be due to adjustments in the jaw cycle as a result of the compound nature of jaw movement for diphthongs as compared to vowels, with further modifications due to the effect of stress on these compound movements.

Adult↗
PubMed1991

Discrimination of formant transition onset frequency: psychoacoustic cues at short, moderate, and long durations.

Two experiments determined the just noticeable difference (jnd) in onset frequency for speech formant transitions followed by a 1800-Hz steady state. Influences of transition duration (30, 45, 60, and 120 ms), transition-onset region (above or below 1800 Hz), and the rate of transition were examined. An overall improvement in discrimination with duration was observed suggesting better frequency resolution and, consequently, better use of pitch/timbre cues with longer transitions. In addition, falling transitions (with onsets above 1800 Hz) were better discriminated than rising, and changing onset to produce increments in transition rate-of-change in frequency yielded smaller jnd's than changing onset to produce decrements. The shortest transitions displayed additional rate-related effects. This last observation may be due to differences in the degree of dispersion of activity in the cochlea when high-rate transitions are effectively treated as non-time-varying, wideband events. The other results may reflect mechanisms that extract the temporal envelopes of signals: Envelope slope and magnitude differences are proposed to provide discriminative cues that supplement or supplant weaker spectrally based pitch/timbre cues for transitions in the short-to-moderate duration range. It is speculated that these cues may also support some speech perceptual decisions.

Attention↗
PubMed1990

General assay for phosphoproteins in cerebrospinal fluid: a candidate marker for paraneoplastic cerebellar degeneration.

The components of protein phosphorylation systems (protein kinases, protein phosphatases, and their phosphoprotein substrates) are highly enriched in neuronal cells compared with other cell types. We exploited this relative neuronal enrichment of protein phosphorylation system components to develop a general assay technique for putative protein kinase substrates (phosphoproteins) in human cerebrospinal fluid. Using this cerebrospinal fluid phosphoprotein assay, we have detected a putative protein kinase C substrate protein of apparent Mr 60 kd in 6 of 14 patients with paraneoplastic cerebellar degeneration but not in any of 55 patients with a variety of other neurological diseases. Phosphoproteins in cerebrospinal fluid may provide novel and unique markers for the diagnosis or staging of neuronal diseases as well as offer potential insights into the biochemical characterization of affected neuronal populations.

Adult↗