Brachial Plexus Schwannoma: Report of 4 cases with Intralesional Enucleation

Brachial plexus tumors are rare. It comprises of only 5% of all tumors of upper limb. The two most common brachial plexus region tumors are schwannomas and neurofibromas. Brachial plexus tumours comprises of only 5% of all tumours of upper limb. Schwannomas are most frequently found in the head and neck region, which comprises 25% of all Schwannomas. There are only about 5% of schwannomas present as brachial plexus tumours. Here we report four cases of brachial plexus schwannoma with surgical removal managed in our centre from 2013 to 2016.


Introduction
Brachial plexus tumours are rare.It comprises of only 5% of all tumours of upper limb [1].The two most common brachial plexus region tumors are schwannomas and neuro ibromas [2][3][4].Both are benign and arise from the nerve sheath.XiaotianJia et al., published a large case series of 143 patients with primary brachial plexus tumors in 2016.In his series, there are 119 schwannoma and 12 neuro ibromas [3].Schwannomas are most frequently found in the head and neck region, which comprises 25% of all Schwannomas.There are only about 5% of schwannomas present as brachial plexus tumours [5].
The most common clinical presentation of primary brachial plexus tumor includes palpable mass, pain, numbness or paresthesias, weakness etc. [3][4][5][6], Brachial plexus schwannoma can present as neck mass, axillary mass, supraclavicular mass or apical lung mass [7][8][9][10].On CT, most schwannomas are iso-dense relative to brain parenchyma.Calci ication or areas of hemorrhage are rare and the enhancement pattern is typically homogeneous.On MRI, schwannomas are iso-intense to hypo-intense on T1-weighted MRI and enhance with gadolinium [11,12].Malignant transformation of schwannoma is very rare, but it has been reported in literature [13].Outcome of surgical removal of brachial plexus schwannoma has been reported to be satisfactory [14].
We report four cases of brachial plexus schwannoma with surgical removal managed in our centre from 2013 to 2016.

Methods
There were four cases of brachial plexus schwannoma managed operatively in our centre from 2013 to 2016.Pre-operatively, magnetic resonance imaging (MRI) and ine needle aspiration (FNA)/biopsy were performed.All the four cases had intranuclear enucleation done under general anesthesia.Microscope was used to assist the procedure intra-operatively.Pre and post excision of the tumor, nerve stimulator was used to con irm intact motor function of the nerve.At the site of enucleation, the nerve was wrapped with commercial anti-adhesive paper made of polylactic acid after removal of tumor.All the excised tumors had histopathological proof of schwannoma.There was no evidence of malignancy in all cases.The clinical information of the four cases was summarized in the following table 1.
there was a well-de ined homogenous T1 hypointense (Figure 2) and T2 hyperintense lesion at right C5 nerve root (Figure 3).Supraclavicular approach was used with a L-shaped incision at the lateral border of sternocleidomastoid muscle and upper border of clavicle (Figure 4).A 1.9x1.4x1.1cmtumor was surgically removed from right C5 nerve root (Figure 5).After the operation, there was temporary numbness at right C5 dermatome for 3 weeks.It completely subsided afterwards.

Case 2
Patient was a 41 year-old male.He presented with left upper limb numbness and weakness.There was no palpable mass.Upon physical examination, there was decreased sensation at left C5 and C6 dermatome.There was also weakness at left supraspinatous, infraspinatous and biceps muscle with MRC grade 3/5.MRI found that there was a well-de ined homogenous T1 hypointense and T2 hyperintense lesion (Figures 6,7) at upper trunk of left brachial plexus.Supraclavicular approach was used to remove the lesion (Figure 8).Post-operatively, there was no more upper limb numbness.The power of the involved muscle improved to MRC grade 4/5.A 32 years-old lady complained of a palpable painless mass at her right supraclavicular fossa.Sensory and motor function was intact.There was positive Tinel sign.Pre-operative MRI scan showed typical feature of schwannoma (Figures 9,10).Supraclavicular approach was adopted for enucleation of lesion.There was a 1.5x1.0x1.5cmschwannoma at the upper trunk of right brachial plexus.No neurological de icit was found after the surgery.

Case 4
A 39 year-old lady had cancer of right breast.There was an incidental inding of an axillary mass during lumpectomy of right breast and sentinel lymph node biopsy surgery.Patient was asymptomatic.She was then referred to our team for further management.MRI and biopsy con irmed the mass was a brachial plexus schwannoma (Figures 11,12).Deltopectoral approach was used in this case (Figure 13).There was a 2.0x2.8x2.3cmlesion located at posterior cord of right brachial.Enucleation was performed.There was no neurological de icit after the operation.

Conclusion
We obtained similar clinical characteristics of brachial plexus schwannoma as those reported in litreture [3,4,[6][7][8][9][10].Brachial plexus schwannoma could be a painless or painful mass.Neurological de icit was not always present.The lesions were found at supraclavicular or axillary region.MRI was a valuable diagnostic tool [15].In our cases, the MRI features of the tumors were consistent.It showed a well-de ined homogenous lesion, hypointense in T1 weighted ilm and hyperintense in T2 weighted ilm.
Since the lesion is benign, the aim of surgery should be maximal debulking of tumor with minimal damage to normal nerve ibres.The described method of intralesional enucleation provided satisfactory outcome in all 4 cases.There was no irreversible neurological damage after the operation.With the mean follow-up period of 27 months, there was no evidence of recurrence of tumor.Our management pathway for brachial plexus schwannoma was summarized below (Table 2).

Figure 4 :
Figure 4: Supraclavicular approach (Head of patient at superior part of the Figure).

Figure 8 :
Figure 8: Lesion at left upper trunk of brachial plexus.

Table 1 :
Summary of clinical information of 4 cases.