We read with interest the article by Tomomasa et al. about a 76-year-old man with metastatic prostate cancer, concurrent SARS-CoV-2 infection (SC2I) and opsoclonus-myoclonus syndrome (OMS) attributed to SC2I or interpreted as paraneoplastic syndrome (PNS) [1]. The patient benefited from orchidectomy, endocrine therapy (degarelix, bicalutamide) and glucocorticoids and partially recovered [1]. The study is remarkable, but several points need to be discussed.

The first point is that the diagnosis of SC2I was made on the basis of suspicion and not evidence [1]. There is no mention of whether a nasopharyngeal swab was positive for SARS-CoV-2 on PCR or not; a positive PCR test is mandatory for the diagnosis of SC2I. It is also not mentioned what kind of treatment against SC2I the patient has received.

The second point is that the diagnosis of OMS is not confirmed [1]. It was reported that the patient had “right horizontal nystagmus,” but this does not meet the definition of opsoclonus. Opsoclonus is defined as rapid, involuntary, and chaotic eye movements that are conjugate and multidirectional in horizontal, vertical, and torsional planes, are arrhythmic, and have no regular pattern or intersaccadic interval (no pause between eye movements) [2]. In addition to opsoclonus, OMS is characterized by myoclonus, which did not occur in the index patient [1]. Myoclonus is defined as sudden, involuntary, and brief muscle twitching or jerking due to either sudden muscle contractions (positive myoclonus) or sudden muscle relaxation (negative myoclonus) [3].

The third point is that it was not stated whether the MRI of the brain and spinal cord was performed with or without contrast [1]. To exclude autoimmune encephalitis (AIE) or immune myelitis as a complication of SC2I or as a manifestation of PNS, contrast administration would have been mandatory.

The fourth point is that it was not reported whether CSF examinations were performed or not [1]. To possibly differentiate between OMS as a complication of SC2I or as a manifestation of PNS, it would have been useful to examine the CSF for pleocytosis, abnormal proteins, immune parameters, and for antibodies related to AIE, immune myelitis, or PNS [1]. Antibodies associated with AIE or myelitis include NMDA, AMPA, LGI1, CASPR2, GABA-A, GABA-B, DPPX, glycine, neurexin, MIG, or IgLON [4]. Antibodies associated with PNS include anti-Hu (ANNA1), anti-Yo (PCCA), anti-Ri (ANNA2), Ma1, Ma2, CRMP5 (CV2), amphiphysin, Tr, Zic4, ANNa3, PCA2, AGNA, VGCC, VGKC, mGluR1, and NDMAR antibodies [5].

The fifth point is that the patient presented with rotary vertigo but was still diagnosed with peripheral vertigo [1]. Rotational vertigo is usually associated with a central nervous system cause of vertigo. There was also no mention of whether the ultrasound examination of the vertebral and carotid arteries was normal or indicated stenosis or occlusion. Rotational vertigo could also be caused by heart failure.

In summary, this study has limitations that put the results and their interpretation into perspective. Removing these limitations could strengthen the conclusions and support the study's message.

Ethics Statement

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Conflicts of Interest

The author declares no conflicts of interest.

Linked Articles

A Case of Suspected Paraneoplastic Nerve Syndrome Associated With Prostate Cancer or Opsoclonus-Myoclonus Syndrome Associated With COVID-19 Infection, but Symptoms Improved After Treatment of Both, https://doi.org.10.1002/iju5.12825.