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Biomedical subjects

J F Brick

Publications and source records attributed to J F Brick.

30 records · Page 2Linked to original sources
PubMed1987

Timber rattlesnake venom-induced myokymia: evidence for peripheral nerve origin.

Facial and limb myokymia occurred in four consecutive cases of timber rattlesnake envenomation and represents the "fasciculations" frequently reported in this entity. The facial myokymia disappears within hours of antivenin therapy and the limb myokymia by increasing serum ionized calcium. These observations suggest that the action of the venom is a biochemical one, increasing peripheral nerve excitability.

Action Potentials↗
PubMed1986

Calcium and myokymia of brainstem origin.

In five patients with Guillain-Barré syndrome, clinical myokymia increased and myokymic burst amplification occurred when ionized Ca++ was lowered by hyperventilation. Myokymia decreased when ionized Ca++ was increased after IV infusion of CaCl2. These responses were absent or diminished in the four patients with myokymia due to brainstem lesions, suggesting that the blood-brain barrier impedes the effects of altered serum ionized Ca++ on axonal excitability. Altering serum Ca++ can distinguish peripheral and central myokymia.

Action Potentials↗
PubMed1986

Exercise-induced membrane failure in paramyotonia congenita.

A marked decrease in the amplitude of the evoked thenar compound muscle action potential followed brief exercise at room temperature in two patients with paramyotonia congenita. This decline was more rapid and pronounced in our patient with coexistent thyrotoxicosis. The prolonged recovery period in paramyotonia congenita differs from the brief exercise-induced decreased compound muscle action potential seen in myotonia congenita and myotonic dystrophy. These findings suggest that exercise, like cold exposure, decreases membrane excitability in paramyotonia congenita.

Action Potentials↗
PubMed1986

Perspective on carbamazepine-induced water intoxication: reversal by demeclocycline.

Carbamazepine (CBZ)-induced water intoxication occasionally limits its usefulness in refractory seizures and trigeminal neuralgia. Fluid restriction, CBZ dose reduction, or concomitant phenytoin therapy may be impractical or ineffective. Demeclocycline (7-chloro-6 demethyl tetracycline) (DMC) corrected the CBZ-induced water intoxication in a 51-year-old man with refractory complex partial seizures and a normal antidiuretic hormone (ADH) level. DMC inhibits ADH-sensitive adenylate cyclase activity in the renal collecting duct and may be useful in correcting the ADH-like or renal antidiuretic effect of CBZ.

Carbamazepine↗
PubMed1982

Calcium effect on generation and amplification of myokymic discharges.

Maneuvers designed to manipulate ionized calcium (Ca++) were carried out in two patients with inflammatory polyradiculoneuropathy and myokymia. Increased clinical myokymia and myokymic burst amplification occurred when ionized Ca++ was lowered by plasma exchange or hyperventilation. Increasing ionized Ca++ (by intravenous infusion of CaCl2) decreased the myokymia. These findings indicate that myokymic discharges are altered by changes in serum ionized Ca++ and effects on axonal excitability.

Adult↗
PubMedDate not supplied

Dipole reversal: an ictal feature of benign partial epilepsy with centrotemporal spikes.

Benign epilepsy with centrotemporal spikes (BECTS) is characterized by brief stereotypical partial seizures with motor and/or sensory symptoms with frequent secondarily generalized seizures. The interictal EEG shows slow, disphasic, high-voltage spikes in the centrotemporal areas. The few published examples of ictal tracings depict focal rhythmic sharp waves and spikes without significant postictal slowing. We report an ictal event in BECTS that is unusual in the evolution and polarity of the ictal discharges. In this subclinical seizure, ictal multiple spike and wave discharges appear as a dipole: they are electropositive in T3-C3 and negative in F3. These surface positive epileptic discharges are unique and require explanation. We postulate that the seizure discharge arises in the depths of the sylvian fissure involving folded cortical areas. This occurs in such a way that the negative component of the discharges is concealed from the scalp electrodes. Thus, a relative positivity is recorded on the surface. This represents a dipole reversal relative to the interictal discharges (characteristic of BECTS). This geometrical explanation allows us to avoid postulating an unusual mechanism of generation of this seizure.

Child↗