Before attributing peroneal neuropathy to entrapment, proximal lesions of the ischiadic nerves need to be ruled out

We read with interest the article by Parra et al. about six patients with unilateral compression neuropathy of the peroneal nerve being attributed to the sedentary lifestyle during an alarm stage of the ongoing pandemic.¹ It was concluded that inability to perform usual activities may have given rise to a more sedentary lifestyle, facilitating compression of the peroneal nerve at the knee.¹ The study is appealing but raises concerns that should be discussed.

We disagree with the notion that entrapment of the peroneal nerves has increased in frequency during the alarm period of the COVID pandemic from the 14th March to the 21st June 2020.¹ The design of the study is not apt to investigate the question if the frequency of peroneal nerve entrapments indeed increased during the period of interest. There was no control group comprising patients who were recruited from a non-pandemic period and there was no provision of the population cohort to which the diseased cohort could be related.

Supposing that the prevalence of peroneal nerve entrapments had truly increased during the observational period from 14th March to 21st June 2020 in Spain, it is conceivable that also other entrapment neuropathies, such as those of the ulnar nerves or the median had increased as well. However, this is not the case according to available published data.

A limitation of the study is that it is not mentioned how proximal affection of the ischiadic nerve was ruled out. Because slowing of the nerve conduction velocity of the common peroneal nerve over the poplitea may be also attributable to a nerve lesion proximal to the knee, it is crucial that proximal lesions of the ischiadic nerve are appropriately ruled out. Therefore, we should know if all six patients had a normal magnetic resonance imaging (MRI) of the lumbar spine, had a normal MRI of the lumbo-sacral plexus, had normal cerebrospinal fluid (CSF) investigations, and had normal lumbar magnetic or electrical stimulation with recordings from thigh muscles.

It should be also mentioned how local pathologies of the poplitea were ruled out that could explain compression of the common peroneal nerve at the level of the knee. Did all six included patients undergo a MRI of the knee and an X-ray of the knee? Had any of the six patients a Baker cyst?

Altogether 11 patients with peroneal nerve neuropathy were identified during the alarm period.¹ Seven developed clinical manifestations during the observational period.¹ One of these patients was excluded because neuropathy was attributed to a ganglion compressing the superficial peroneal nerve. We should be informed why the other four patients were excluded although it is mentioned that they presented with clinical signs of peroneal nerve involvement.¹ This discrepancy should be solved.

Overall, the interesting study has limitations that call the results and their interpretation into question. Clarifying these weaknesses would strengthen the conclusions and could improve the study. Proximal lesions of the ischiadic or common peroneal nerve need to be appropriately ruled out before attributing symptomatic lesions of the peroneal nerve to compression neuropathy of the peroneal nerve at the level of knee.

Level of evidence

Level of evidence iii.

Authors’ contribution

xx: design, literature search, discussion, first draft, critical comments, final approval.

Disclosures

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Compliance with ethics guidelines

This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Funding

No funding was received.