Abstract & Commentary
How Best to Do the Jolly’ Test
By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Rubin reports no financial relationships relevant to this field of study.
In the electrophysiological evaluation of patients with myasthenic syndromes, adding 1 minute of exercise is the most sensitive method of eliciting a significant decremental response.
Oh SJ, et al. One-minute exercise is best for evaluation of postexercise exhaustion in myasthenia gravis. Muscle Nerve 2014;50:413-416.
Friedrich Jolly (1844-1904), German neurologist and psychiatrist, student of Georg Meissner (Meissner’s corpuscles), and pioneer of myasthenia research, described the electrophysiological aspects of myasthenic fatigue, which form the basis of the repetitive nerve stimulation (RNS) test that bears his name. An abnormal "Jolly" test is a reproducible decrement of muscle amplitude of > 10% during 3 Hz repetitive stimulation, and results from a decreased safety margin, due to abnormal acetylcholine (Ach) receptors, and consequent failure to reach threshold depolarization with progressively fewer muscle fibers depolarizing as nerve terminals become partially depleted of ACh. Exercise exacerbates this decrement, known as postexercise exhaustion (PEE), but the best exercise duration to achieve PEE is debatable, and is the subject of this study.
Among 45 myasthenia gravis (MG) patients who consented to this study, 32 patients (17 men and 15 women, with a mean age of 54.6 years) had an abnormal decremental response on Jolly testing either at rest or postexercise. MG diagnosis was based on positive testing of any of acetylcholine receptor antibodies (n = 24), muscle-specific kinase antibodies (1 of 8 seronegative patients), RNS, or single-fiber electromyography (positive in all 16 who underwent testing).
To determine the exercise duration that would elicit maximum decrement, RNS on the abductor digiti quinti (ADQ) muscle was performed using supra-maximal stimulation at 3 Hz for 2 seconds, under standard technique, immediately following exercise lasting 10, 30, and 60 seconds, as well as 30, 60, 120, 180, and 240 seconds postexercise. Exercise of the ADQ was performed by having the subjects spread their fingers against maximal resistance from the examiner. Anticholinesterase medications were held for at least 12 hours prior to RNS, skin temperature was kept at or above 32° C, peak-to-peak amplitude was used for measurements, and decrement was measured by comparing the smallest response to the initial response. Statistical analysis comprised the paired t-test or chi-square test, with P < 0.05 considered statistically significant.
At rest, the mean decrement was 16% among all 32 patients, with an abnormal decrement observed at rest in 21 (66%), and in 11 patients only postexercise. Decrement was significantly increased at 2 and 3 minutes following 30 seconds of exercise, and at 2, 3, and 4 minutes following 60 seconds of exercise. Significantly, in 11 patients who only demonstrated decrement after exercise but not at rest, it was observed in 8 of 11 after 60 seconds of exercise, but in only 5 of 11 after 30 seconds of exercise. Postexercise decrement in myasthenia is best elicited by performing RNS after 1 minute of exercise.
Commentary
A non-progressive, or U-shaped, pattern of decrement to 3 Hz RNS is characteristic of MG. How does this compare to Lambert-Eaton myasthenic syndrome (LEMS)? To address this question, retrospective review was undertaken of RNS studies performed on 58 muscles in 34 LEMS patients and on 54 muscles in 44 MG patients. Calculations were made of the "early decrement" (percent fall in peak motor amplitude from the first to the fourth or fifth response), and the "late decrement" (percent fall of first to the ninth or tenth response), and the ratio between the early and late decrement was calculated as well ("Late/Early"). Despite overlap in individual cases, late decrement was greater than early decrement in LEMS, with the reverse true in MG, indicating that when the decrement becomes progressively greater during 3 Hz-RNS, the diagnosis is more likely to be LEMS rather than MG.1
Reference
- Sanders D, et al. Is the decremental pattern in Lambert-Eaton myasthenic syndrome different from that in myasthenia gravis? Neurology 2014;82(Suppl P2):80.
