PMC8555621_01
(A) Characteristic furrowing of the hypothenar eminence seen in our patient with palmaris brevis syndrome. (B) There was no visual evidence that the non-dominant hand was similarly affected. (C) Worsening of palmaris brevis contractions triggered by grasping a pipettor. (D) Patient's workspace shows evidence of extreme wear with erosion of the countertop (arrow). He did not use a mouse pad or wrist support while handling the mouse. (E) EMG recording of spontaneous activity from the right palmaris brevis muscle.
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F1
At the time of neurological presentation, the spasms were present during most of the waking day and associated with dimpling or creasing of the right hypothenar eminence (Figure 1A and B). Precise pipetting of microliter and submicroliter volumes required substantial activation of the pinky finger for stabilization of the pipettor body or handle (Figure 1C). He had worn down the countertop on the computer table where the mouse was stationed (Figure 1D). Needle EMG of the palmaris brevis showed prolonged bursts of spontaneous motor unit activity of fluctuating amplitude (Figure 1E).