[Value of anal sphincter electromyography, orthostatic hypotension and dizziness in diagnosing multiple system atrophy].

Objective: To explore the value of anal sphincter electromyography (ASEMG), orthostatic hypotension (OH), and dizziness in diagnosing multiple system atrophy (MSA).

Method: The characteristics of ASEMG and OH were compared among patients with dizziness (MSA and non-MSA), patients without OH (MSA and non-MSA), and patients with probable MSA (OH and non-OH).

Results: Totally 476 patients underwent ASEMG examinations. Dizziness was the onset symptom in 69 patients. Between the MSA group and non-MSA group, the mean duration of dizziness [(14.6 +/- 2.1) vs. (12.8 +/- 2.0) ms, P < 0.01] and satellite potential occurrence rate [(22.7 +/- 11.8)% vs. (12.2 +/- 8.9)% , P < 0.01] were significantly different, while the OH rate (84.6% vs. 55.2% ) and the difference of the blood pressure between standing and supine positions were not significantly different. In 162 patients with symptom of dizziness, the mean duration of dizziness [(15.3 +/- 2.7) vs. (12.8 +/- 1.9) ms, P < 0.001], satellite potential occurrence rate [(25.4 +/- 12.8)% vs. (13.5 +/- 10.4)%, P < 0.001] , and difference of the diastolic blood pressure [(18.5 +/- 17.0) vs. (11.7 +/- 12.7) mmHg, P < 0.05] were significantly different between the MSA group and non-MSA group, while the normal rate of blood pressure at standing position (60% vs. 41.9%) and the difference of systolic blood pressure were not significantly different. In 146 patients with abnormal blood pressure at standing and supine positions, the mean duration of dizziness [(15.0 +/- 2.4) vs. (12.8 +/- 1.7) ms, P < 0.001] and satellite potential occurrence rate [(22.0 +/- 12.2)% vs. (10.6 +/- 8.5)%, P < 0.001] were significantly different between the MSA group (n = 61) and non-MSA group (n = 85). In 125 patients with probable MSA, the mean duration of dizziness [(15.5 +/- 2.4) vs. (15.9 +/- 2.2) ms, P > 0.05] and satellite potential occurrence rate [(24.3 +/- 12.6)% vs. (22.7 +/- 12.4)%, P > 0.05] were not significantly different between those with OH and those without OH. The rates of dizziness and the percentage of dizziness as the onset symptom were 93.2% and 52.3% in OH group and 44.4% and 8.3% in non-OH group.

Conclusions: ASEMG is better than OH in diagnosing patients with dizziness suspected as MSA. Neurogenic lesion can be found by ASEMG in patients without OH, which is helpful in the early diagnosis of MSA.