Abstract Details

Title Concentric Needle Jitter Abnormalities in Patients with Ocular and Generalized MG

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P7 - Poster Session 7 (8:00 AM-9:00 AM)

Poster/Presentation
Number 11-005

Objective To describe the differences in single-fiber electromyography (SFEMG) between patients with the ocular and generalized form of Myasthenia Gravis.

Background The jitter measurement through the SFEMG is the most sensitive electrophysiological test in neuromuscular junction disorders.

Design/Methods Ninety-seven patients were studied (53.6% male; 46.4% female), 85 (87.6%) with the generalized form (MGG) and 12 (12.4%) with the ocular form (MGO). Antibodies against acetylcholine receptors were analyzed from all patients. The jitter was measured with a concentric needle electrode through voluntary or stimulated activation of the Orbicularis Oculi, Frontalis, and Extensor Digitorum muscles. Results were expressed as MCD (“mean consecutive difference”) and/or as a percentage of MCD above the normal limit.

Results The antibody against acetylcholine receptor was observed in 89.4% of patients with MGG and 50% of MGO patients, with a mean dosage of 16.9 nmol/L in MGG and 1.83 in MGO (p<0 .05). Some jitter parameter was abnormal in 91/97 patients (93.8%). Abnormal jitter was detected in 92.9% of MGG patients and 100% of MGO patients, with a mean of 66.3 µs for MGG and 33.3 µs for MGO (p<0.05). Impulse block was observed in 20.9% of MGG patients and 5.8% of MGO patients. MCD > 86µs was observed only in patients with MGG. The six patients with a normal jitter value were already under treatment when the SFEMG was performed, and in two, only one muscle was tested. All MGO patients had at least two muscles tested.

Conclusions Abnormal jitter was observed in all MGO patients and 92.9% of MGG patients. Patients with MGG and normal jitter had already started treatment, and only one muscle was tested. The analysis of the second muscle showed increased sensitivity in MGO patients.

Authors/Disclosures
Gabriel P. Paiva, MD (FAMERP) PRESENTER	Dr. Paiva has nothing to disclose.
	No disclosure on file

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