A 53-year-old woman was presented for the evaluation of visual disturbances, generalized and multifocal myoclonus, and progressive ataxia that began at age 30 years (cf. Video 1). Bilateral cherry-red spots in the macula (figure) and a cortical origin in the EEG-EMG coregistration with back-averaging were observed. Reduced neuraminidase activity in fibroblasts and the homozygous mutation c.403G>A in the NEU1 gene confirmed the diagnosis of sialidosis type I.
Video 1
Cortical Myoclonus. We observed generalized and multifocal myoclonus at rest (segment 1). It worsens during a sustained posture, such as holding arms or legs out against gravity. The myoclonus activity also increases with tactile sensory stimulation (segment 2). It worsens with activities such as finger-nose-finger test (segment 3). The patient shows dysarthria. The speech facility deteriorates with myoclonus (segment 4).Download Supplementary Video 1 via http://dx.doi.org/10.1212/012464_Video_1
The dilated fundus examination showed bilateral cherry-red spots on the retina. This is a red zone at the center of the macula surrounded by retinal opacification. It is due to the accumulation of different lipids, sphingolipid, or oligosaccharide material in the ganglion cells of the retina.
Sialidosis or cherry-red spot–myoclonus syndrome is classified into normomorphic or type I, beginning usually after 20 years old, whereas dysmorphic or type II begins at birth or in early childhood. In both, generalized myoclonus and ataxia can be found. EEG-EMG coregistration may show cortical potential followed by the myoclonus, proving a cortical origin. Differential diagnosis is necessary for other inherited metabolic disorders such as Tay-Sachs disease or Unverricht-Lundborg disease. Cherry-red spots on the retina, cortical myoclonus, and progressive ataxia are essential keys to suspicion.1,2
Study Funding
This research was supported by grants from the Spanish Ministry of Science and Innovation [RTC2019-007150-1], the Instituto de Salud Carlos III-Fondo Europeo de Desarrollo Regional (ISCIII-FEDER) [PI14/01823, PI16/01575, PI18/01898, and PI19/01576], the Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía [CVI-02526 and CTS-7685], the Consejería de Salud y Bienestar Social de la Junta de Andalucía [PI-0471-2013, PE-0210-2018, PI-0459-2018, and PE-0186-2019], and the Fundación Alicia Koplowitz. Silvia Jesús has a “Acción B Clínicos-Investigadores” (Action B Clinicians-Researchers) contract [B-0007-2019] funded by the “Consejería de Salud y Familiar,” and Daniel Macías-García has a Río Hortega contract [CM18/00142] funded by the Health Institute Carlos III.
Disclosure
B. Vélez Gómez has received honoraria from Sanofi; S. Jesús has received honoraria from AbbVie, Bial, Merz, UCB, Italfarmaco, and Zambon; D. Macías-García has received honoraria from AbbVie, Teva, and Zambon; B. Lechon reports no disclosures relevant to the manuscript; and P. Mir has served in the advisory boards or received honorarium for lecturing from Abbott, Allergan, AbbVie, Bial, Britannia, Italfarmaco, Merz, UCB, Teva, and Zambon. Go to Neurology.org/N for full disclosures.
Appendix Authors
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Teaching slides links.lww.com/WNL/B466
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