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Australas Radio1 1 9 9 1 : 3%379-381

MRI Scanning in Brachial Plexus NeuropathyV E m Y AHERN,M.B., B.S.

Registrar, Department of Radiation OncologyY.S. SOO, M.B. B.S.(HK),D.M.R.D.(Eng),M.A.R.C.R.

StafSSpecialist,DepartmentofRadiologyALLAN D. LANGLANDS, B.Sc., F.R.A.C.R., F.R.C.S.(Ed.)

Director, Departmentof Radiation OncologyWestmead Hospital, Westmead,NSW, Australia

INTRODUCTIONBrachial plexus neuropathy (BPN) occurring afterradiotherapy for breast carcinoma is uncommon.Distinction between radiation-induced neuropathy andtumour infiltration of the plexus is frequently difficult onclinical grounds, electrodiagnosticstudies or computerised

tomography (CT)canning.We report the use of magnetic resonance imaging(MRI) to diagnose BPN due to tumour infiltration in apatient with breast carcinoma.CASE REPORT

In June 1986, a 39 year old woman developed a 3.5cmcarcinoma of the right breast. There were no lymph nodespalpable nor evidence of metastatic disease. The patientwas treated by total mastectomy and axillary clearance.The primary tumour was an infiltrating duct carcinoma.None of 40 lymph nodes dissected were involved. No fur-ther treatment was advised. Five months later, a 5 x 3cmmass of lymph nodes in the right supraclavicular fossa(SCF) was proven by incision biopsy to be involved withmetastatic breast carcinoma. There was no clinical evi-dence of disease at other sites. Routine blood tests, CXRandCT scan of the thorax were normal.

On 21/11/86 the patient commenced chemotherapyconsisting of 3 cycles of novantrone (N) and cyclophos-phamide (C), followed by 6Mev radiotherapy to the rightSCF and internal mammary chain by a direct anteriorfield. A dose of 50Gy at a depth of 3cm was given in 25fractions over 38 days. Six cycles of cyclophosphamide(C), methotrexate (M), 5 fluorouracil (F),and prednisone(P) were then given.By the commencement of CMFP, there was completeremission of disease.In December 1988, the patient complained of pain inthe right shoulder and left parastemal area. No abnormali-ty was detected on physical examination, bone scan, orCT scan of the thorax.On 10/2/89, she presented with a 3 day history of pro-gressive swelling of the right arm. There was a fullness ofthe right SCF but no discrete mass. No metastatic diseasewas clinically evident. Venography demonstrated throm-bosis of the right subclavian vein, and the patient was

treated with intravenous heparin, andwarfarin. No under-lying cause for the thrombosis was demonstrated on a CTOne month later the patient complained of increasingpain around the right shoulder. Matted lymph nodes overan area of 5 x 5cm were palpable in the right SCF.

Multiple lung metastases were seen on chest X-ray. CMFchemotherapy at intervals of three weeks, was recom-menced on 23/3/89. After a total of 6 cycles ofchemotherapy, the right SCF mass wa s still palpable andmeasured4 3cm, but the patient no longerrequiredanal-gesia to control her pain. A chest X-ray demonstrated sig-nificant reduction in the size of the pulmonary metastases.Within 2 months, the patient returned with severesharp pain in the right arm adiating to the right hand, andsubjective weakness of the fingers of the right hand.On examination, the right SCF mass had not changedin size or consistency, and there were no neurologicalabnormalities of the upper limbs. An MRI scan of thelower cervical and upper thoracic region clearly demon-strated metastatic disease in the right SCF infiltrating intothe right brachial plexus region laterally and inferiorly

into the extrapleural space of the right upper lateral chest(Fig. la,b).She was last seen on 12/2/90, with right arm pain con-trolled by oralmorphine, and increasing difficulty in hold-ing objects in the right hand.

scan.

DISCUSSIONRadiation fibrosis affecting the brachial plexus follow-ing therapy for breast carcinoma can be difficult to distin-guish from tumour infiltration of the plexus.Kori et a1 (1981) (9) in an analysis of 1(Kfpatients withBPN, defined clinical criteria for distinguishing the twoentities. Early severe pain, hand weakness, whole plexusinvolvement and Homers syndrome suggested malignantBPN. These criteria were not supported in studies by

Thomas and Colby (1972) or Bagley et a1(1978). (12,2).Radiation fibrosis is usually assumed to be the cause ifa biopsy of the SCF is negative for malignancy, the= is noevidence of metastases, and the patient survives for a pro-tracted period (5).

A d d m for correspondence:Dr. .AhemDepartment of Radiation OncologyWestmeadHospitalWestmead, NSW 2145 AustraliaSubmitted forpublication on:6th April, 1990Resubmittedfor publicationon: 14thJanuary, 1 9 9 fAccepted forpublicationon:14thJ u e , 1991

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FIGURE I A -Coronal TI weighted image shows an isointense lobulated ma ss (arrows) in the right brachial plexus region, indenting on the apical extrapleural space .These cr i te r ia wi l l not be fu lf i l led f or a l l pa t ients.Negative biopsies were reported by Cascino et a1 ( 1 983)(4) in 2 patients who underwent surgical explorations ofthe brachia l p lexus but repea t b iops ies d i rec ted a t CTabnormalities in the brachial plexus were positive.Lederman and Wilbourn (1984) (10) found tha t t heelectrodiagnostic findings of fasciculation and the occur-rence of myokymia (involuntary muscle movement in anundulating, wavelike manner) ( 1 ) in radiation-inducedBPN, together with certain clinical features, were suffi-ciently diagnostic to allow an accurate differentiation ofthe tw o entities in a majority of patients.Recently CT scanning of the brachial plexus has beenclaimed to be the investigation of choice in distinguishing

the causes of BPN, particularly when thin C T cuts andbolus intravenous enhancement are used (3). With tumourrecurrence, the CT scan should demonstrate a soft tissuemass rather than a hazing of the margins of axillary ves-sels or increased density of the subcutaneous and axillaryfat; (5,3).Prior surgery or radiotherapy to the affected SCF willalter the CT scan appearances of the SC F region, m akinginterpretation based on these criteria difficult.A further limitation of CT scanning interpretation of

(1983): 5 patients with histologically proven metastaticAuwo luc i un Kudio /o , iy W i / .3.5. N o . 4 . N o w r n h f r . 1 Y Y I

FIGURE IB - The mass shows increased signals in T2 weighted th e SCF in was recognised by Cascino ersequence, indicative ofmetastatic disease (a rrows).380

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MRI SCANNING IN BRACHIAL PLEXUS NEUROPATHY

plexopathy had normal CT scans. This may have beenbecause CT scans will not identify perineural infiltrationof the plexus by tumour.The use of MRI in distinguishing radiation inducedBPN from recurrent tumour in breast cancer has been

reported on only 3 previous occasions (7,8,11).Axial and sagittal views are considered complemen-tary in defining the extent and volume of a tissue mass inthe region of the brachial plexus (1 1). On T1 weightedimages, tumour is generally of higher signal intensity thanradiation fibrosis. The higher intensity of tumour com-pared to radiation fibrosis is more pronounced on T2images. In the case reported by Rapoport et a1 1988, themass in the brachial plexus area was of inhomogeneoussignal intensity on T2 images - anteriorly the mass wa s ofhigh signal intensity, and posteriorly, low. Biopsy of theanterior portion was positive for metastatic breast carcino-ma; the posterior lower intensity portion was consideredto be radiation fibrosis.We conclude that the physical symptoms and signs,

and clinical course of radiation induced BPN, may beidentical to those of disease recurrence. Surgical explo-ration, electrodiagnostic tests, and CT scanning of theSCF will not always be helpful in distinguishing the twoentities. MRI scanning may ultimately prove to be theinvestigation of choice. The distinction between BPN dueto radiation or malignant infiltration is not academic, astreatment options exist for breast cancer (the commonestcause of brachial plexus involvement by tumour).

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