Herpes zoster rash illustrating dorsal ramus innervation in the C6 and C8 dermatomes: a report of two cases

Introduction

Compression of the cervical nerve root within the cervical foramen results in cervical radiculopathy, a condition typically manifesting as radicular pain, motor dysfunction, and sensory disturbances extending along the affected nerve’s trajectory into the ipsilateral upper limb (1). Furthermore, it is common to observe unilateral scapular pain prior to the onset of symptoms in the upper extremity (2,3).

Previously, Nomura et al. reported a case involving a simultaneous herpes zoster rash on the upper extremity and interscapular region, originating from the C8 spinal dorsal root ganglion. They proposed that this type of rash could serve as a unique tool to visualize the precise innervation patterns of the dorsal rami of the cervical spinal nerves, providing valuable insight into the mechanism of scapular pain associated with cervical radiculopathy (4). However, evidence from a single case report is insufficient to support this hypothesis.

Building on this, we present a similar case involving a patient with simultaneous herpes zoster rash in the suprascapular region and upper extremity (involving the C6 nerve root). Additionally, we detail a second case involving a C8-related rash affecting the scapular region and upper limb. To the best of our knowledge, this is the first documentation that visually defines the C6 dorsal ramus’s lateral branch innervation zone on the scapula, corresponding to the C6 radiculopathy-related painful area. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-310/rc).

Case presentation

Case 1

A middle-aged, otherwise healthy man presented to Nomura Orthopaedic Clinic with sudden onset of left suprascapular pain associated with neuralgia on the radial side of his left upper extremity, without any history of trauma. He had no significant medical history. Based on his symptoms, we suspected left-sided C6 cervical radiculopathy and prescribed 100 mg/day pregabalin. Three days later, he returned to our clinic complaining of a rash on his left upper body. On the second examination, he had a blistering skin rash simultaneously affecting the left upper extremity and suprascapular region (Figure 1). The rash was mainly distributed along the radial side of the left upper arm, forearm, and the thumb and index fingers of the left hand, including near the dorsal surface of the proximal phalanx of the thumb (arrow in Figure 1), corresponding to the innervation area of the left C6 spinal nerve (Figure 1, upper panels). Concurrently, the rash on his back was localized to the upper half of the left scapular region (Figure 1, lower panel). A diagnosis of herpes zoster was made, and the patient was treated with 1,000 mg/day oral valaciclovir hydrochloride and topical vidarabine ointment for 1 week. His symptoms improved promptly following treatment, and no postherpetic neuralgia was observed.

Figure 1 Clinical photographs of a middle-aged male exhibiting vesicular eruptions. The rash was distributed along the radial aspect of the left upper limb (upper panels) and the left suprascapular area (lower panel). The arrow indicates skin rash near the dorsal surface of the proximal phalanx of the thumb, corresponding to the innervation area of the left C6 spinal nerve.

Case 2

An elderly, otherwise healthy man experienced neuralgia in his right upper extremity without any history of trauma 2 months prior. Three days after the onset of symptoms, a herpes zoster rash appeared on his right upper extremity. He had no significant medical history. He was referred to a dermatologist and treated with antiviral medication. Despite improvement in the skin rash, neuralgia in his right upper extremity—particularly with nocturnal pain—persisted. He was treated with nonsteroidal anti-inflammatory drugs, mirogabalin besylate, and tramadol hydrochloride/acetaminophen, after which he was referred to Tohoku Central Hospital. On initial physical examination, residual blistering skin rash was observed on the ulnar side of his right upper extremity, including near the dorsal surface of the proximal phalanx of the little finger (arrow in Figure 2), and in the scapular region on the same side (Figure 2). The distribution of the rash corresponded to the innervation area of the right C8 spinal nerve (Figure 2, left and right upper panels). Simultaneously, the rash on the back was localized to the outer lower half of the right scapular region (Figure 2, lower right panel).

Figure 2 An elderly male patient showing vesicular skin lesions on the right side. The rash affected the ulnar aspect of the upper extremity (left and right upper panels) and the scapular region (lower right panel). The arrow indicates residual blistering skin rash near the dorsal surface of the proximal phalanx of the little finger, corresponding to the innervation area of the right C8 spinal nerve.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Among cases of neck or scapular pain associated with cervical radiculopathy, Tanaka et al. demonstrated that unilateral scapular pain localizes to the suprascapular, interscapular, or scapular regions, corresponding to C5/C6, C7/C8, and C8 radiculopathy, respectively (5). Mizutamari et al. conducted an anatomical study to clarify the mechanism of scapular pain secondary to cervical radiculopathy by examining the medial branches of the spinal nerve dorsal rami. Their findings indicated that the C5 and C8 dorsal rami descend inferolaterally to the suprascapular and central scapular areas as cutaneous nerves; however, they did not identify C6 or C7 dorsal rami descending to the scapular region (2). This suggests that the classical anatomical approach may be technically challenging for exposing the small branches of the cervical dorsal ramus.

A typical shingles rash is known to occur unilaterally along the dermatome of a single peripheral nerve, except in cases of severe immunosuppression, which was not applicable to our patients (6,7). In herpes zoster stemming from spinal dorsal root ganglia, the reactivated varicella-zoster virus travels from a specific ganglion along sensory nerve microtubules to the skin. This process causes prodromal pain followed by a rash, and since there is no anatomical communication between spinal ganglia, the eruption is dermatomal (8). Thus, herpes zoster rashes appearing on both the upper extremity and scapular region are likely caused by reactivation of the virus from the same spinal dorsal root ganglion.

In Case 1, the rash on the upper extremity and suprascapular region was likely caused by viral reactivation from the C6 ganglion, since the dermatome of the rash in both regions corresponded to the innervation area of the C6 nerve root and the scapular region related to C5 or C6 cervical radiculopathy, respectively. Similarly, in Case 2, the rash in the upper limb and scapular region appeared to result from viral reactivation in the C8 ganglion, as the affected dermatomes corresponded to the C8 nerve root and the scapular region associated with C8 cervical radiculopathy. The rash pattern in Case 2 also resembled that of a previously reported case, although the scapular rash in that case was located in the interscapular region, typically related to C7 or C8 cervical radiculopathy (4). According to the dermatome map of the International Standards for Neurological Classification of Spinal Cord Injury by the American Spinal Injury Association, a key point of the C6 or C8 spinal root area is the dorsal surface of the proximal phalanx of the thumb or little finger, respectively, which is likely compatible with the rash distribution in Case 1 or Case 2, respectively (9).

Nomura et al. further reported a related case of herpes zoster rash occurring simultaneously on the medial and distal parts of the femur and the medial buttock, illustrating the innervation zone of the L3 nerve root and the dorsal ramus of the L3 spinal nerve, respectively (10). Historically, the virological application of herpes zoster rash for visualizing innervation of the dorsal rami from spinal nerves dates back over 120 years (11). In 1900, Head and Campbell examined nearly 500 cases of herpes zoster virus eruption (shingles) and created a dermatome map demonstrating the regions affected by infection in different spinal ganglia; however, cases involving the upper extremities were relatively rare (only 10 from C5–C8) (11). To further refine dermatome maps of the dorsal rami, we suggest a broad survey of herpes zoster rash cases, conducted either in collaboration with dermatologists or through a multicenter study.

Typical causes of common scapular pain include muscle lesions, rotator cuff injury, snapping scapula syndrome, facet or discogenic lesions, and radiculopathy (12,13). Regarding radiculopathy-related scapular pain, a previous report described that among 241 patients with C7 radiculopathy who underwent C6–7 anterior cervical discectomy, 28 (12%) presented with subscapular pain as the sole complaint on the side ipsilateral to the nerve root compression. All 28 patients experienced complete pain relief within 6 months after surgery (14). Correspondingly, based on our anatomical findings using herpes zoster rash, there is a possibility that any pathological condition causing occlusion of a cervical foramen involving the dorsal ramus of the cervical spinal nerves may result in neurological scapular pain.

Segmental zoster paresis is a rare complication (15-17). Its incidence has been reported as only 0.3–5%, but it remains unclear (15,17). The pain in patients with herpes zoster can be sufficiently severe to prevent full exertion during manual muscle testing, potentially giving a false impression of muscle paralysis (15). Electromyography and magnetic resonance imaging (MRI) can be useful as supplementary diagnostic techniques to identify true segmental zoster paresis (18-21). To demonstrate peripheral neuropathy caused by herpes zoster, MRI T2-weighted images or contrast-enhanced T1-weighted images with gadolinium are useful (20-22). A previous study classified four possible patterns of neuropathy based on MRI findings of spinal ganglia and roots: (I) ascending spinal roots; (II) ascending spinal cord; (III) polyradiculopathy; and (IV) intrathecal spread (20). Additionally, a few case reports have described patients with zoster myelitis showing spinal cord lesions on MRI, with pathology characterized by necrosis of cord tissue associated with hemorrhage, perivascular inflammation, and disruption of normal neural architecture (21,23).

Conclusions

Two cases of herpes zoster presenting with simultaneous skin rash in the upper extremity and interscapular region are reported. We suggest that simultaneous herpes zoster rash can serve as a useful model for demonstrating the detailed innervation of the dorsal ramus of the cervical spinal nerves.

Acknowledgments

We would like to thank Editage (http://www.editage.jp) for editing and reviewing the manuscript.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-310/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-310/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-310/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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