Subcapsular resection of brachial plexus schwannoma

Dear Editor,

Brachial plexus tumors are a rare group of tumors, accounting for 5% of all upper extremity tumors [1]. Schwannomas belong to the peripheral nerve sheath tumors. They arise from Schwann cells, are encapsulated, slow growing and usually benign in nature. Most are sporadic, but the occurrence is associated with some genetic syndromes -⁠ neurofibromatosis type 2 and schwannomatosis, especially when multiple lesions are found [2]. They typically manifest as a palpable, sometimes visible mass. Local pain and neurological deficits in both sensation (paresthesia, dysesthesia, burning pain) and mobility in the distribution area of the affected nerves and/or nerve roots may be present [3]. In the following, we describe a case report of a patient who underwent subcapsular resection of a supraclavicular schwannoma of the brachial plexus.

The patient (53 years old) presented for palpation findings in the left supraclavicular region. Subjectively, he has no complaints and negates pain. On physical examination, only irradiation of pain to the left upper extremity during palpation of the mass is present, neurological findings without impairment of sensation and mobility. MRI was performed with the finding of a suspected brachial plexus schwannoma (Figure 1). The patient was indicated for tumour resection. Surgery was performed under general anesthesia with perioperative electrophysiological neuromonitoring of the brachial plexus using EMG. The procedure was performed from an anterior supraclavicular approach, penetration under the platysma, fascia incision between m. sternocleidomastoideus and m. trapezius, caudally bordering m. omohyiodeus. Subsequent preparation through the fat body and penetration between the fascial fibers, where a tumor (Fig. 2) distracting the fibers of m. scalenus anterior ventrally and medially was evident, along with the course of the n. phrenicus, which was visually evident and its function confirmed by stimulation prior to resection. No nerve fibers were visually evident on the surface. Under neuromonitoring with magnifying glasses at 4.2× magnification, an incision of the capsule was made at the site of negative stimulus responses. The tumor was sequentially subcapsularly resected using an ultrasonic aspirator. The capsule was not resected due to the presence of positive stimulus responses corresponding to the C5 root region. After resection, no obvious bundle of nerve fibers was identified in the sheath outside or inside the sheath. Postoperatively, the patient was pain free. Histopathologically, the tumor closed as a schwannoma with predominance of Antoni A structures. Follow-up MRI was performed 4 months later with the conclusion of no residual tumor (Figure 1).

Peroperative electrophysiological neuromonitoring is an indispensable part of surgical resection of peripheral nerve sheath tumors, not only in the brachial plexus but also in other anatomical locations. There are several basic modalities -⁠ nerve conduction studies, somatosensory evoked potentials and EMG [3]. The choice of modality depends on the type of resection procedure or the localization of the lesion.

Schwannomas of the brachial plexus can occur anywhere from the spinal roots to individual nerves. There are two basic surgical approaches -⁠ anterior supraclavicular and infraclavicular. The choice of approach depends on the localization of the lesion. The anterior supraclavicular approach is used when the lesion is localized in the area of the spinal roots and trunks. In the case of localization at the level of the fascicles and terminal nerves, the anterior infraclavicular approach should be used. If the lesion is larger in extent and involves the retroclavicular part of the plexus, a combined anterior approach with or without clavicular intersection can be applied [2].

The surgical management of schwannomas can be approached by two different concepts. The first option is to perform a complete excision of the tumor with preservation or loss of the nerve from which the tumor originated. The outcome depends on whether the tumor can be separated from the nerve fibers. The method is radical enough, but if it is not possible to separate the nerve fibres, it comes at the cost of loss of nerve function [4]. In the case of benign lesions of the character of schwannoma, a procedure in which the loss of nerve function would occur cannot currently be accepted. The second concept is subtotal salvage surgery aimed at preserving nerve function. The group includes several techniques of similar design, such as intracapsular enucleation or subcapsular resection. Intracapsular enucleation has brought the possibility to resect the tumor with a significantly lower risk of postoperative neurological deficit. The technique was popularized by Netterville, who described a procedure involving incision of the mass in an electrically "silent" area, i.e., without the presence of nerve fibers. He also emphasizes the irreplaceable role of neuromonitoring during the procedure. Over a period of 27 years, he resected 43 cervical schwannomas, 23 of which were operated on using the intracapsular enucleation technique. The results of the enucleations were very favorable, with 22 of the 23 patients having minimal or no neurological deficit [5]. Subcapsular resection is one of the techniques with minimal risk of damage to nerve fibers and surrounding structures, with preservation of nerve continuity and thus function [6]. The technique may be particularly beneficial in such tumors in which the fibers are so distended and distracted that their identification within the pseudocapsule is virtually impossible, and at the same time, the actual differentiation of the true tumor capsule from this pseudocapsule is not visually obvious [6].

Sandler et al. describe the advantages of salvage techniques in a review of the literature on vagal nerve schwannomas, which included 149 case reports, of which 105 underwent complete excision and 44 underwent subtotal resection. In subtotal resections, nerve function was preserved in 97%, whereas in complete excisions only 29%. In terms of postoperative period, patients after subtotal resections had a lower percentage of vocal cord paresis (41 vs. 54.1%) and postoperative hoarseness (23.1 vs. 59.7%) compared with complete excision [4]. However, the nerve fibers may not be compactly localized over the capsule but may be spread out in the pseudocapsule, which may be a source of postoperative neurological deficit with a larger extent of resection [3,7].

The risk of recurrence in sporadic schwannomas is low according to published studies [1,2,8]. In a group of 119 patients with histologically confirmed brachial plexus schwannoma, Jia et al. reported no recurrence during a 3-year follow-up; however, most patients underwent complete resection [1]. For salvage techniques, Torossian et al. reported two cases of recurrence in a group of 15 patients with a mean follow-up time of 4.1 years, which they attributed to inadequate microsurgical dissection of the tumor [8]. The results of these studies indicate a very low risk of recurrence, and therefore the emphasis during surgery is on preserving nerve fiber function.

Schwannomas of the brachial plexus are benign peripheral nerve sheath tumors. They most often present clinically as a palpable mass, pain and neurological deficit in both sensory and motor skills may be present. Treatment is primarily surgical removal of the tumor with emphasis on preservation of nerve or root function. Subcapsular microsurgical resection, presented here, is one possible method, especially for larger tumors that cause distension of nerve fibers in the pseudocapsule, where efforts to visually identify them are very difficult. This approach has the advantage of preserving neurological function with a very low risk of tumour recurrence. At the same time, the surgical technique is simple, fast and effective with minimal risk of damage to nerve fibres and surrounding structures. The use of perioperative electrophysiological monitoring is an essential and integral part of the surgical procedure.

Ethical aspects

The patient whose case is described in this paper signed informed consents for the diagnostic and therapeutic procedures. The authors state that the study of this case was performed in accordance with the ethical standards of the 1975 Declaration of Helsinki, revised in 2000.

Conflict of interest

The authors declare that they have no conflict of interest in relation to the subject of the study.

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version