ABSTRACT
Previous studies have suggested that an abnormal release of potassium from muscle may accompany attacks of paramyotonic weakness. We investigated 3 patients with paramyotonia congenita before and after the induction of forearm muscle weakness by exercise in cold water. Two of these patients had paralysis periodica paramyotonica and the 3rd had paramyotonia congenita. At the time of paramyotonic weakness there was a marked increase in the arterialized-venous concentration difference of potassium across forearm muscle. This indicated a significant uptake of potassium by forearm muscle in all 3 patients. Normal controls showed a slight release of potassium both at rest and after exercise in cold water. These results suggest that (1) the sodium-potassium pump of the muscle fiber is operating efficiently during paramyotonic weakness; and (2) there is a different mechanism responsible for the generalized weakness that occurs in hyperkalemic periodic paralysis.
Subject(s)
Muscles/metabolism , Myotonia/metabolism , Potassium/metabolism , Adult , Arteries , Cold Temperature , Exercise , Forearm , Humans , Hyperkalemia/complications , Infant , Lidocaine/analogs & derivatives , Lidocaine/pharmacology , Male , Muscles/physiopathology , Myotonia/etiology , Myotonia/physiopathology , Paralysis/blood , Paralysis/etiology , Paralysis/metabolism , Periodicity , Potassium/blood , Tocainide , VeinsABSTRACT
We studied hyperkalemic attacks in one family with adynamia episodica (AE) and one family with paralysis periodica paramyotonica (PPP). Under exercise, serum potassium increased as in healthy subjects. Thiazide did not affect this increase. Thirty minutes after exercise, a second potassium increase occurred, but could be prevented by thiazide and not by mexiletine. After cooling, muscle relaxation time was normal in AE but increased up to 100 times in PPP; this cooling effect was prevented by mexiletine. Although hyperkalemic attacks are similar in AE and in PPP, the membrane defect in PPP seems more complex.
Subject(s)
Hyperkalemia/blood , Muscular Diseases/blood , Myotonia/blood , Adult , Female , Humans , Hyperkalemia/complications , Hyperkalemia/physiopathology , Male , Muscular Diseases/complications , Muscular Diseases/physiopathology , Myotonia/complications , Myotonia/physiopathology , Paralysis/blood , Paralysis/complications , Paralysis/physiopathology , Physical ExertionABSTRACT
We investigated the effectiveness of tocainide and hydrochlorothiazide on muscular symptoms in a patient with paramyotonia congenita and episodic attacks of hyperkalemic paralysis. Generalized weakness was evoked by exercise and potassium loading. Myotonia and weakness were evoked by local muscle cooling. Tocainide prevented myotonia and weakness induced by cooling, but failed to prevent hyperkalemic weakness. Hydrochlorothiazide prevented hyperkalemic weakness, but did not influence symptoms evoked by cooling. These results suggest that, in this disorder, two different mechanisms cause muscular weakness.
Subject(s)
Hydrochlorothiazide/therapeutic use , Hyperkalemia/drug therapy , Lidocaine/analogs & derivatives , Myotonia Congenita/drug therapy , Paralysis/drug therapy , Adult , Humans , Hyperkalemia/complications , Hypothermia, Induced , Lidocaine/therapeutic use , Male , Myotonia Congenita/etiology , Paralysis/complications , Physical Exertion , Potassium , TocainideABSTRACT
Fourteen patients with paramyotonia congenita were examined clinically. Patients of 3 families had no myotonia in a warm environment while in a cold environment they developed paradoxical myotonia (myotonia aggravated by repeated muscle contraction). Patients of a 4th family had myotonia associated with after-activity in a warm environment which was not paradoxical. This myotonia was aggravated by cooling. In a warm environment the resting muscles of all patients showed no spontaneous electromyographic activity except for occasional myotonic runs. On cooling, spontaneous fibrillations developed. This was most intense at 32 degrees C-28 degrees C (muscle temperature). On deeper cooling it ceased. In contrast, 5 patients with myotonia congenita did not show such activity during cooling. In all paramyotonic patients cooling (30 degrees C-25 degrees C) produced muscle paralysis, which outlasted rewarming by several hours. At 32 degrees C-30 degrees C muscle relaxation was slowed. Recording of electromyographic activity and isometric contractions of the long finger flexors during cooling revealed that the slowing of muscle relaxation in paramyotonia is not as closely linked to after-activity as is the slowing of muscle relaxation in myotonia congenita.
Subject(s)
Cold Temperature , Hot Temperature , Muscle Contraction , Muscle Relaxation , Myotonia Congenita/physiopathology , Adolescent , Adult , Aged , Child , Electromyography , Female , Humans , Lidocaine/analogs & derivatives , Lidocaine/therapeutic use , Male , Middle Aged , Myotonia Congenita/drug therapy , TocainideABSTRACT
Recent studies have shown that the sodium conductance of the sarcolemma is disturbed in paramyotonia. Tocainide is a new antiarrhythmic agent which seems to reduce effectively sodium conductance. Eight patients with paramyotonia were treated with tocainide, whereby the paramyotonic stiffness and weakness brought about by cooling could be prevented.
