Introduction
A pseudohernia is an abdominal wall bulge that there is no actual muscular disruption and all muscle layers remain intact. We report a case that abdominal muscle activities were accurately and quantitatively measured by using ultrasonography (US) and surface electromyography (sEMG) in the patient with abdominal pseudohernia.
Case Report
A 62-year-old man fell from a height of 4 m on March 26, 2020. Compression fracture of thoracic and lumbar spine (T11, T12 and L1) and narrowing of left T11 neural foramina were observed in magnetic resonance imaging. On physical examination, there was no neurological deficit caused by spinal cord injury.
As abdominal pressure increases, for example, when standing up or coughing, approximately 15 x 15 cm marked bulge on the left flank innervated by the 11th thoracic nerve was observed (Fig. 1).
In order to quantitatively analyze the muscle activity, three tests were done. On first test, the thickness of the three muscle layers, external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) muscles was measured by US. We conducted a test in three position : resting in supine position, resting in sitting position, and when measuring the maximum expiratory pressure (MEP) in sitting position (Fig. 2).
Secondly, the activities of abdominal muscles were measured using sEMG by attaching electrodes to a total of 8 channels at the same time; both rectus abdominis (RA), both EO, both IO/TrA muscles, and the most severe herniation area and the opposite side of it. A reference muscle activity value was set during MEP measurement and the degree of muscle activation was compared to it while blowing positive expiratory pressure device at 20 % intensity of MEP. The root mean square (RMS) of three central seconds of the expiratory phase of each muscle was analyzed. The maximum of the mean RMS of three reproducible maneuvers was chosen. The results are in table 1.
On third test, denervation was identified through US guided needle EMG into IO muscle.
Discussion
According to the results of abdominal US, when force was applied to the abdomen, the thickness of the muscle layer on the bulging site became rather thinner. It assumed that the muscles in the lesion area, which are not contracted well, were stretched as the abdominal pressure increased. According to the results of sEMG, the percentage of the reference voluntary contraction (%RVC) value of muscle activity of the left abdominal muscles was greater than that of the right. It is considered that this is because the left abdominal muscle activity increased to maintain muscle strength under the same load.
Using these outstanding assessment methods, we can develop proper rehabilitation treatment strategies. Furthermore, evaluating whether the symptoms have improved through follow-up tests will contribute to improve the patient's quality of life. |
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Approximately 15 x 15cm marked bulge on the left side of abdomen in the area innervated by the 11th thoracic nerve when the supine (A), standing (B) position, and when the valsalva maneuver was performed (C).
The thickness of the three abdominal muscle layers, external oblique muscle (D1), internal oblique muscle (D2), transversus abdominis muscle (D3) were measured by ultrasonography. Measurements were performed in the area with the most severe herniation (L) and the opposite (R). Each measurement was done in three steps : in supine (a), sitting (b) position, and while the patient measures the maximum expiratory pressure in sitting position (c).
Measured RMS and %RVC of each abdominal muscle using sEMG.
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