Supplementary Material for: Unilateral wing-beating tremor in neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease with various neurological manifestations, including tremor. Here, we report a case involving a 68-year-old man with an 8-year history of tremor in his right arm. Subsequently, examination revealed that the patient was suffering from a low-frequency, high-amplitude, and posture-induced proximal arm tremor elicited by sustained arm abduction with flexed elbows (wing-beating tremor), which was partially improved by zonisamide treatment. Abnormal expansion of GGC repeats in the NOTCH2NLC gene confirmed the diagnosis of NIID. This case highlights the fact that unilateral wing-beating tremor can be a manifestation of NIID. Zonisamide may be effective for controlling tremors associated with NIID.