Anatomy and physiology argue against SARS-CoV-2-associated Parsonage–Turner syndrome if the accessory nerve is affected

Dear Editor,

We read with interest the article by Saade et al. reporting on a 22-year-old male with Parsonage Turner syndrome (PTS) of the right cervico-brachial plexus, attributed to asymptomatic SARS-CoV-2 infection three weeks previously [1]. Corticosteroid treatment resulted in only incomplete recovery after sixth months [1]. The study is appealing but raises concerns that warrant further discussion.

We agree that SARS-CoV-2-related PTS has been previously reported [2,3], but we disagree that the patient reported by Saade et al. had PTS. PTS in the index patient was diagnosed based on the history (pain in cervical spine, pain in right upper limb), clinical neurologic exam (limited shoulder motion in abduction due to pain, right trapezius muscle wasting, weak right upper limb anteflexion, right scapular winging, ropey tendon in the inferior portion of the right trapezius), electromyography (EMG) (trapezius and anterior serratus muscle denervation), magnetic resonance imaging (MRI) (edema (T2 hyperintensity) of the trapezius and serratus anterior muscles), and the beneficial effect of corticosteroids resulting in incomplete recovery at the sixth-month follow-up [1].

The first argument against PTS is that the accessory nerve (pure motor XIth cranial nerve) is not part of the cervicobrachial plexus. The accessory nerve has two roots, one cranial and one spinal. The spinal root comprises contributions from the C1-C5 cervical roots and then runs backward through the foramen magnum to join the cranial root, both leaving the skull together through the jugular foramen. The cranial portion innervates the pharyngeal muscles, whereas the spinal portion innervates the sternocleidomastoid and trapezius muscles.

The second argument against PTS is that the patient had torticollis at least three weeks prior to admission. Torticollis has several etiologies, but one is unilateral denervation of the sternocleidomastoid muscle. Because the patient had weakness and wasting of the right trapezius muscle, it is conceivable that the right sternocleidomastoid muscle was also under-innervated. Therefore, we would need to know whether there was denervation of the right sternocleidomastoid muscle on EMG and whether torticollis was toward the right or the left. Weakness of the right trapezius muscle would lead to leftward laterocollis but not rightward torticollis.

A third argument against PTS is that the clinical manifestations as described could also be due to polyradiculitis (Guillain Barré syndrome (GBS)), which was not appropriately ruled out. The patient did not undergo contrast-enhanced MRI of the cervical spine and no cerebrospinal fluid (CSF) examination was performed. In case of polyradiculitis, MRI could show swelling and enhancement of the lower cranial or cervical spinal roots [4]. CSF examination could show albuminocytologic dissociation [2]. Because radiculitis can be subclinical, nerve conduction (F-wave) study of the proximal portions of peripheral nerves innervating the right upper limb muscles would also be warranted.

Taken together, the clinical presentation of the index patient could also implicate GBS with XIth cranial nerve involvement [5]. If the patient in fact had SARS-CoV-2-associated GBS, the preferred treatment would have been intravenous immunoglobulins or plasmapheresis rather than corticosteroids.

Overall, the study shows limitations that require re-evaluation and discussion. Clarifying these weaknesses would strengthen the conclusions and improve the study. Before diagnosing SARS-CoV-2-related PTS, differential diagnoses, and particularly GBS, need to be thoroughly ruled out.

Author contribution

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

Funding

No funding was received.

Conflicts of interest

None.

Ethics approval

Only secondary data were used.

Consent to participate

Not applicable.