Video 1
Neurological examination. The patient displays a bilateral action tremor in the upper limbs, with a slight left-sided predominance, along with occasional rest tremor. Additionally, she exhibits a jerky tremor affecting the head, accompanied by tremor in the jaw and voice. Furthermore, there is evidence of a dystonic posture in the left fifth finger and a dystonic posture of the head, with a rightward tilt. The patient did not report any sensory trick, nor the presence of a null point. Prolonged eye closure suspicious for blepharospasm can be observed at second 18, 31–33, and 38–39, although the patient did not present a clear hyperactivity of the orbicularis oculi muscles, nor other associated motor manifestations, including apraxia of eyelid opening and increased blink rate. Tremor with a jerky motor component was evident during spiral drawing and when she poured water form one cup to the other. Along with jerky intrusions, mild bradykinesia, i.e., movement slowness, is observed during repetitive finger and hand movements. Despite being slow, her gait appears normal. The remaining neurological examination (not shown in the video) was unremarkable. Please note that the video was recorded under antitremorigenic therapy (Propranolol 120 mg and Clonazepam 0.9 mg daily) and about 4 months after the last injection of Botulinum Toxin type A into the splenius muscles bilaterally.
Figure 1
Kinematic upper limbs and head tremor recordings. The upper panels depict upper limb postural tremor, while the lower panels represent head tremor. Two five-seconds extracts of accelerometric traces from reference markers in 3D space are shown on the left. On the right, Welch periodograms (WP) overlaid on the power spectra (PS) of the corresponding traces are shown. Note that a clear peak with a small full width half maximum is evident for upper limb postural tremor recording. A narrow peak in the frequency spectrum indicates that much of the oscillation falls within a narrow frequency range, so the movement is characterized by high rhythmicity. This constitutes laboratory support for the identification of the abnormal movement as tremor. The frequency peak was slightly wider for head tremor, given to less regular oscillation and supporting a dystonic component. We did not kinematically record tremor during spiral drawing, where the jerky motor component might have been more evident.
Figure 2
Skin biopsy. Exemplificative pictures from the patient’s skin samples, analyzed through indirect immunofluorescence, showing normal intraepidermal nerve fiber density (IENFD) at both distal calf (12 fibers/mm) and proximal thigh (16 fibers/mm). Autonomic innervation was normally represented in dermal annexes, like piloerector muscles and eccrine sweat glands, which could be found only in the distal sample. Red staining represents nerve fibers as marked by antibodies for the pan-axonal marker protein gene product 9.5 (PGP9.5). Green staining represents collagen IV, marking the basal membrane and the connective structure of dermal annexes. White arrows indicate intraepidermal nerve fibers.