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Table of Contents    
Year : 2019  |  Volume : 67  |  Issue : 2  |  Page : 481-484

Brachial plexus neuropathy by hibernoma compression: An unusual presentation of peripheral non-neural sheath nerve tumor and a systematic review of literature

1 Department of Neurosurgery, Cajuru University Hospital, Curitiba, Brazil
2 Citopar Laboratory, Curitiba, Brazil

Date of Web Publication13-May-2019

Correspondence Address:
Dr. Luis Henrique A Sousa
Avenue Sao Jose, 300, Curitiba, Parana - 80050-350
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.258049

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 » Abstract 

Brachial plexus neuropathies are uncommon and are rarely caused by a tumor. The clinical presentation of a brachial plexus neuropathy caused by a tumor depends on the degree of malignancy of the tumor and its localization. We report an illustrative case of a 27-year old female subject with a progressively increasing mass lesion causing brachial plexus compression, ipsilateral shoulder pain, C8 dermatomal paresthesia, and impairment of motor power. The patient underwent surgical resection of the mass and neurolysis of the nerves in the vicinity. Following the surgical procedure, the patient had improvement in the pain and paresthesia that he was suffering from. The histopathological diagnosis revealed a hibernoma, an extremely rare tumor described only once previously in this location. A systematic review of the literature was performed utilizing the PubMed database to access articles published before March 2018, using: A – the term 'hibernoma' in the title/abstract associated with the following MeSH terms: brachial plexus neuropathies OR brachial plexus neuropathy OR nerve compression syndrome, OR brachial plexus; B – the MeSH term 'brachial plexus' associated with the term 'non neural sheath nerve tumor' or 'peripheral non-neural sheath nerve tumor'. The origin of the hibernoma, as well as its metabolic influence, pathology, and treatment have been discussed.

Keywords: Adipose tissue neoplasm, brachial plexus injury, brachial plexus neuropathy, hibernoma, peripheral non-neural sheath tumor
Key Message: Peripheral non-neural sheath tumors are rare causes of neuropathy. A rare case of a hibernoma with its characteristic features is described, including its propensity to cause a metabolic imbalance. Surgical resection provides a pathological diagnosis, relief from neurological impairment, and occasionally, a subsequent recurrence-free duration.

How to cite this article:
Sousa LH, Chaves JP, Marques RA, Silva LL. Brachial plexus neuropathy by hibernoma compression: An unusual presentation of peripheral non-neural sheath nerve tumor and a systematic review of literature. Neurol India 2019;67:481-4

How to cite this URL:
Sousa LH, Chaves JP, Marques RA, Silva LL. Brachial plexus neuropathy by hibernoma compression: An unusual presentation of peripheral non-neural sheath nerve tumor and a systematic review of literature. Neurol India [serial online] 2019 [cited 2021 Jan 27];67:481-4. Available from:

Brachial plexus injuries occur due to different mechanisms, mainly as a result of nerve stretch or contusion, a gunshot wound, or a laceration.[1] A compression by a tumor is a rare cause of brachial plexus injury.[1],[2] Tumor compression causing brachial plexus neuropathy was first described approximately 150 years ago. Over the years, a wide variety of pathological entities have been discovered to result in brachial plexus involvement. Their real prevalence is unknown as they cannot be accurately estimated due to the existence of only published case series.[2–5]

 » Case Report Top

A 27-year old female patient with a 3-year history of painless mass in the left cervical region that was progressively increasing in size, presented in our department. About 1 year before referral to our service, the patient started to feel pain and paresthesia in the left shoulder and arm. She had a past history of diabetes mellitus, hypothyroidism, hypertension, and depression. All of these medical conditions were being adequately treated. She maintained a good compliance for her medication. She was not being administered any beta-blockers. On physical examination, she was morbidly obese, with a decrease in power in her left arm flexion, extension, and adduction (Medical Research Council grade 4) with coexistent hypoesthesia in the left C8 dermatome. The Tinel's sign was negative.

Her laboratory screening did not reveal any other hormonal or metabolic imbalance. An ultrasound examination demonstrated an 8.2 × 3.2 × 6 cm lesion with echogenicity similar to fat, being of moderate vasculature on the Doppler study [Figure 1]. Computed tomography (CT) demonstrated a hypodense rounded mass with no contrast enhancement in the supraclavicular region, extending from the scaleni to the trapezius muscle [Figure 2]. Magnetic resonance image (MRI) could not be performed due to the incompatibility of the MRI machine in performing the screening, considering the patient's weight and size.
Figure 1: Echography of the cervical/supraclavicular mass. (a) Coronal view. (b) Sagittal view. (c and d) Doppler imaging showing the moderate vasculature inside the mass

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Figure 2: Computed tomography of the cervical region. (a and b) Axial view. A hypodense mass is seen with intermediate density between the subcutaneous tissue and muscle, without contrast enhancement. (c) Sagittal view. Note the lesion extension from the scaleni to the trapezius muscle in the posterior aspect of the cervical region

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The patient underwent a microsurgical gross total resection and neurolysis (the lesion after its excision is shown in [Figure 3], and its histopathological characteristics are shown in [Figure 4]). At a one-year follow up, the patient presented with a partial relief of her pain and there was sensory improvement in the region of dermatomal hypoaesthesia. No recurrence of the lesion was seen until the last available follow-up assessment.
Figure 3: The mass seen after its gross total resection. A bulky soft mass revealing its bright yellow-brown color is seen

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Figure 4: Histopathology of the hibernoma at hematoxylin and eosin staining. Note the presence of multivacuolated cytoplasm, which represents a characteristic feature of the tumor. (a) Original magnification ×10. (b) Original magnification ×400

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 » Literature Review Top

A systematic review of the literature was performed at the PubMed database. The articles published before March 2018 were selected using: A – the term 'hibernoma' in the title/abstract associated with the following MeSH terms: 'brachial plexus neuropathies' OR 'brachial plexus neuropathy' OR 'nerve compression syndrome' OR 'brachial plexus'; B – the MeSH term 'brachial plexus' associated with the following terms: 'peripheral non neural sheath nerve tumor' OR 'peripheral non-neural sheath nerve tumor'. Only human-related case reports and articles published in English, Spanish, or Portuguese were included.

 » Results Top

Just two papers fulfilled criteria A,[6],[7] and a few fulfilled criteria B.[2],[3],[5],[8],[9] Some reports were excluded despite their fulfilling criteria-B because they described tumors other than a hibernoma (such as an Ewing's sarcoma,[8] or a synovial sarcoma[9]). The literature search, therefore, to the best of our knowledge, revealed that our patient was the second reported case in the literature developing a hibernoma that was causing brachial plexus neuropathy by its compression. The first patient was described approximately 1 year ago in the largest case series of brachial plexus lipomatous tumors. That patient shared a similar clinical presentation as ours (a 26-year old female patient with shoulder numbness and pain) but had no improvement in her clinical symptoms after excision of the tumor.[7]

 » Discussion Top

Tumors involving the peripheral nerve system can be classified by their origin as being 'intrinsic' (peripheral neural sheath tumor: PNST) or 'extrinsic' (peripheral non-neural sheath tumor: PNNST); and by their nature into 'benign' or 'malignant'.[4],[10]

Benign lesions are predominantly PNNSTs, and include mainly ganglion cysts, localized peripheral hypertrophy, lipomas, vascular tumors, or desmoid tumors.[2],[5],[7]

Benign fatty tumors of the upper limb are categorized according to their cell of origin into a lipoblastoma (arising from lipoblasts/immature fatty cells), hibernoma (arising from mature brown fat cells), and lipoma (arising from lipocytes/mature white fat cells); the last one is the most common type[6] and rarely causes nerve compression.[10],[11]

Hibernoma does not constitute a well-known entity in the differential diagnosis of PNNST of the brachial plexus; first of all, it is a rare tumor; and second, it was previously not cited in the category of PNNST in the published reports that have included a significant number of patients.[2],[3],[5] It has, however, been described before as an unusual differential diagnosis in the category of cervical and supraclavicular masses.[12],[13],[14]

The patient reported here could have had the hibernoma as a result of an imbalance between her body response to her obesity and diabetes due to two reasons. Firstly, the brown adipose tissue (BAT) and the white adipose tissue (WAT) share the same origin (mesenchymal stem cells) but arise from differing precursors (the former expresses gene Myf-5, related with the skeletal muscle precursor and brown adipogenesis). The result is that BAT is developmentally closer to the skeletal muscles than WAT. Also, there are adipocytes capable of transdifferentiating between BAT and WAT,[15] possibly by the loss of tumor suppressor gene AIP (aryl hydrocarbon receptor interacting protein).[16]

Functionally, the presence of a protein UCP-1 (uncoupling protein 1) in BAT provides thermogenesis, counteracting the energy storage function of WAT.[15],[17] BAT is identified in hibernating animals (justifying the name of the tumor) and human newborns. In the latter, BAT may persist in a few areas during their ageing, like the neck and axilla,[6],[15],[17] with the possibility of increasing its activity inversely with temperature, and directly with the body mass index (in the elderly patients), with advancing age, and the usage of beta-blockers.[15],[17]

Hibernomas arise from fetal brown fat tissue;[12],[14] or, they may be a manifestation of a BAT-mimicking tumor.[18] A high prevalence of intramuscular lesions on the thigh[14] (which is not a usual place of existence of fetal BAT) may be due to the common developmental origin of the skeletal muscle and BAT.[19]

Although, a hibernoma is induced by some drugs in rats, this is not relevant to humans in the therapeutic dose,[20] unlike a lipoma that has been associated with chronic glucocorticoid use.[11] The concomitant loss of MEN-1 (menin1) and AIP (aryl hydrocarbon receptor interacting protein) are acquired mutations in a hibernoma. The loss of MEN-1 is seen in other tumors as well; the latter is associated with the upregulation of UCP-1 and is required for the development of hibernoma cells that arise from BAT.[16] Its development also correlates with metabolic changes and with weight increase.[18]

A painless soft tissue mass that is slow growing is expected; in some cases, however, the progressing clinical presentation has been due to the subsequent compression of nearby structures.[7],[14],[21] On sonography, positron emission tomography (PET)/computed tomography (CT), and magnetic resonance imaging (MRI), a lesion with a lipoma-like appearance with prominent vascularity is seen [the vascularity may be directly observable by the Doppler imaging or angiography, or indirectly by the increased contrast enhancement and avid fluorodeoxyglucose (FDG) uptake].[22]

The differential diagnosis of a hibernoma includes a lipoma or a liposarcoma. These entities cannot be differentiated from a hibernoma by the PET/CT[22] or MRI findings,[14] and therefore, a histopathological evaluation is essential for establishing the diagnosis of a hibernoma.[21],[22]

Benign and small tumors have a better prognosis in part because total tumor resection is more easily achievable. Their gross total resection results in a lower risk of recurrence and usually leads to a significant improvement in the muscle strength and the improvement of sensations of the involved dermatomes that were having a hypoaesthetic sensation prior to the tumor excision.[4]

Patients with neurofibromatosis and a diagnosis of a peripheral nerve sheath tumor (PNST) or a malignant PNST have a higher recurrence rate; malignancy results in a worse prognosis due to the lack of a standardized adjuvant protocol to manage these lesions.[4]

 » Conclusion Top

Brachial plexus manifestations are rarely caused by tumor compression; the presence of a hibernoma resulting in this symptomatology is even rarer. The clinical presentation of patients harbouring a hibernoma depends on the presence of mass effect and the compression of nearby structures. Hibernomas could represent a consequence of metabolic imbalance and are associated with the loss of tumor suppressor gene, AIP. Further studies investigating the association of the development of a hibernoma with an imbalance in the body metabolism are needed. Imaging studies may occasionally rule out other diagnostic possibilities including the malignant ones. Surgery is necessary for establishing the histopathological diagnosis as well as in the treatment of the lesion, and a good outcome is expected following total excision of the lesion.

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Conflicts of interest

There are no conflicts of interest.

 » References Top

Kim DH, Murovic JA, Tiel RL, Kline DG. Mechanisms of injury in operative brachial plexus lesions. Neurosurg Focus 2004;16:1-8.  Back to cited text no. 1
Ganju A, Roosen N, Kline DG, Tiel RL. Outcomes in a consecutive series of 111 surgically treated plexal tumors: A review of the experience at the Louisiana State University Health Sciences Center. J Neurosurg 2001;95:51-60.  Back to cited text no. 2
Lusk MD, Kline DG, Garcia CA. Tumors of the brachial plexus. Neurosurgery 1987;21:439-53.  Back to cited text no. 3
Montano N, D'Alessandris QG, D'Ercole M, Lauretti L, Pallini R, Di Bonaventura R, et al. Tumors of the peripheral nervous system: Analysis of prognostic factors in a series with long-term follow-up and review of the literature. J Neurosurg 2016;125:363-71.  Back to cited text no. 4
Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 146 peripheral non—neural sheath nerve tumors: 30-year experience at Louisiana State University Health Sciences Center. J Neurosurg 2005;102:256-66.  Back to cited text no. 5
Al-Qattan MM, Al-Lazzam AM, Al Thunayan A, Al Namlah A, Mahmoud S, Hashem F, et al. Classification of benign fatty tumors of the upper limb. Hand Surg 2005;10:43-59.  Back to cited text no. 6
Graf A, Yang K, King D, Dzwierzynski W, Sanger J, Hettinger P. Lipomas of the brachial plexus: A case series and review of the literature. Hand (N Y) 2017. doi: 10.1177/1558944717735946.  Back to cited text no. 7
Mohan AT, Park DH, Jalgaonkar A, Alorjani M, Aston W, Briggs T. Intra-neural Ewing's sarcoma of the upper limb mimicking a peripheral nerve tumour. A report of 2 cases. J Plast Reconstr Aesthet Surg 2011;64:e153-6.  Back to cited text no. 8
Ng W, Thway K. Intraneural extension of Synovial Sarcoma. Int J Surg Pathol 2015;23:649-51.  Back to cited text no. 9
Flores LP, Carneiro JZ. Peripheral nerve compression secondary to adjacent lipomas. Surg Neurol 2007;67:258-62.  Back to cited text no. 10
Guha D, Kiehl T-R, Guha A. Lipoma compressing the brachial plexus in a patient with sarcoidosis: Case report. Br J Neurosurg 2011;25:530-1.  Back to cited text no. 11
Khattala K, Elmadi A, Bouamama H, Rami M, Bouabdallah Y. Cervical hibernoma in a two- year old boy. Pan Afr Med J 2013;16:27.  Back to cited text no. 12
Trujillo O, Cui IH, Malone M, Suurna M. An unusual presentation of a rare benign tumor in the head and neck: A review of hibernomas. Laryngoscope 2015;125:1656-9.  Back to cited text no. 13
Beals C, Rogers A, Wakely P, Mayerson JL, Scharschmidt TJ. Hibernomas: A single-institution experience and review of literature. Med Oncol 2013;31:769.  Back to cited text no. 14
Lee P, Swarbrick MM, Ho KKY. Brown adipose tissue in adult humans: A metabolic renaissance. Endocr Rev 2013;34:413-38.  Back to cited text no. 15
Magnusson L, Hansen N, Saba KH, Nilsson J, Fioretos T, Rissler P, et al. Loss of the tumor suppressor gene AIP mediates the browning of human brown fat tumors. J Pathol 2017;243:160-4.  Back to cited text no. 16
Cypess AM, Lehman S, Williams G, Tal I, Rodman D, Goldfine AB, et al. Identification and importance of brown adipose tissue in adult humans. N Engl J Med 2009;360:1509-17.  Back to cited text no. 17
Gadea E, Thivat E, Paulon R, Mishellany F, Gimbergues P, Capel F, et al. Hibernoma: A clinical model for exploring the role of brown adipose tissue in the regulation of body weight? J Clin Endocrinol Metab 2014;99:1-6.  Back to cited text no. 18
Vassos N, Lell M, Hohenberger W, Croner RS, Agaimy A. Deep-seated huge hibernoma of soft tissue: A rare differential diagnosis of atypical lipomatous tumor/well differentiated liposarcoma. Int J Clin Exp Pathol 2013;6:2178-84.  Back to cited text no. 19
Radi Z, Bartholomew P, Elwell M, Vogel WM. Comparative pathophysiology, toxicology, and human cancer risk assessment of pharmaceutical-induced hibernoma. Toxicol Appl Pharmacol 2013;273:456-63.  Back to cited text no. 20
Cipriano CA, Gray RRL, Fernandez JJ. Hibernomas of the upper extremity: A case report and literature review. Hand (NY) 2015;10:547-9.  Back to cited text no. 21
Burt AM, Huang BK. Imaging review of lipomatous musculoskeletal lesions. SICOT-J 2017;3:34.  Back to cited text no. 22


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