Differences in F-Wave Characteristics between Spinobulbar Muscular Atrophy and Amyotrophic Lateral Sclerosis

Abstract

There is limited data on the differences in F-wave characteristics between spinobulbar muscular atrophy (SBMA) and lower motor neuron dominant (LMND) amyotrophic lateral sclerosis (ALS). We compared the parameters of F-waves recorded bilaterally from the median, ulnar, tibial, and deep peroneal nerves in 32 SBMA patients, 37 patients with LMND ALS, and 30 normal controls. The maximum F-wave amplitudes, frequencies of giant F-waves, and frequencies of patients with giant F-waves in all nerves examined were significantly higher in the SBMA patients than in the ALS patients and the normal controls. The mean F-wave amplitude, maximum F-wave amplitude, frequency of giant F-waves, and frequency of patients with giant F-waves in the median and deep peroneal nerves were comparable between the ALS patients and normal controls. Giant F-waves were detected in multiple nerves and were often symmetrical in the SBMA patients compared with the ALS patients. The number of nerves with giant F-waves seems to be the most robust variable for differentiation of SBMA from ALS, with an area under the curve of 0.908 (95% CI: 0.835–0.982). A cut-off value of the number of nerves with giant F-waves (≥3) for diagnosing SBMA showed high sensitivity and specificity: 85% sensitivity and 81% specificity vs. ALS patients. No significant correlations were found between the pooled frequency of giant F-waves and disease duration in the SBMA (r = 0.162, P = 0.418) or ALS groups (r = 0.107, P = 0.529). Our findings suggested that F-waves might be used to discriminate SBMA from ALS, even at early stages of disease.

A Retrospective Study of the Characteristics and Clinical Significance of A-Waves in Amyotrophic Lateral Sclerosis

“…In ALS patients, there was differential involvement between different muscles ( 12 , 13 ). Lower motor neuron degeneration in abductor pollicis brevis was faster than that in abductor digiti minimi, while motoneurons innervating extensor digitorum brevis were preferentially affected than those innervating abductor halluces brevis, in accordance with previous studies ( 14 , 15 ). In the present study, the frequency of A-waves and frequency of subjects with A-waves in the ulnar and tibial nerves were significantly increased in the ALS patients, in accordance with the split-hand and split-leg syndrome in ALS ( 16 , 17 ).…”

Evaluation of F wave and split hand index in patients with amyotrophic lateral sclerosis

“…On the contrary, other parameters (F wave persistence, latency, and duration and also the F chronodispersion) were comparable between ALS and aged-matched control group. Similar findings were observed by many researchers [16][17][18]. These discordant findings might result from the difference in sample size or the series of electrical stimuli to elicit F waves.…”

Clinical and Physiological Significance of F-Wave in Spinocerebellar Ataxia Type 3

“…The significantly increased F/M amplitude ratio in SCA3 patients compared to PreSCA3 and normal controls, probably caused by upper motor neuron involvement resulting in either increased tendency of the unaffected neurons to generate F-wave or to synchronization of centrifugal impulses (21). The generation of giant F-wave of patients with anterior horn cell disorders may be attributed to axonal sprouting and subsequent reorganization of a muscle's innervation (18,19). The significant increase in the number of giant F-wave in tibial nerves of SCA3 patients and PreSCA3 may imply the preferential affection of spinal motoneurons innervating the abductor halluces brevis.…”

“…A large amplitude F-wave exceeding the mean value plus 2 standard deviations (SD) of the largest F-wave recorded in healthy subjects was considered a giant F-wave (18). In the present study, we defined the amplitude for a giant F-wave according the previous study (19), which was 1473.80 mV in the median nerve, 1,293.69 mV in the ulnar nerve, and 1,045.46 mV in the tibial nerve.…”