AJR:167, November 1996 1283

Detection of Nerve RootletAvulsion on CT Myelography inPatients with Birth Palsy andBrachial Plexus Injury AfterTrauma

Andrew T.Walker1John C. Chaloupka1’2Alain C. J. de Lotbiniere3

Scott W. Wolfe4Richard Goldman5E. Leon Kier1

OBJECTIVE. Recent advances in neurosurgical tteatment of traumatic and birth-related

brachial plexus injuries require differentiation of preganglionic nerve rotlet avulsion from

postganglionic lesions. The purpose of this study was to evaluate the efficacy of thin-section

high-resolution CT myelography f�r revealing cervicothoracic nerve rootlet avulsion in

patients with brachial plexus injuries before surgery.

MATERIALS AND METHODS. We evaluated eight patients with psttraumatic or

birth-related brachial plexus injury on cervical plain film myelography and high-resolution

CT myelography befbre surgical exploration and repair. CT myelograms were retrospectively

evaluated for nerve rootlet avulsion. traumatic pseudonieningocele. and deformity of the sub-

arachnoid space. Results were correlated with surgical exploration and intraoperative soma-

tosensory evoked potentials.

RESULTS. Seventy-two (95C% ) of 76 imaged cervicothoracic levels were adequately

shown on CT myelography. Nerve rootlet avulsion. or preganglionic disruption. was shown at

2 1 levels. Associated pseudomeningocele. or deformity of’ the suharachnoid space. was seen

at I 2 (57�k ) of the 2 1 avulsion levels. Surgical exploration and intraoperative somatosensory

evoked potentials showed complete preganglionic nerve ro()tlet avulsion at 22 levels. One of

the complete avulsions revealed by surgery was not included on the patient�s CT myelogram.

Of the 2 1 imaged levels, 20 were correctly revealed on CT myelography (9Y% sensitivity.

98% specificity). At surgery. partial nerve rootlet avulsion was found at three other levels.

None ofthe partial avulsions was correctly identified on the CT myelograms.

CONCLUSION. High-resolution CT myelography with thin contiguous axial sections is

sensitive for revealing complete nerve rootlet avulsion in patients with brachial plexus birth

palsies and brachial plexus injuries after trauma. Preoperative CT myelographv in these

patients allows a more complete injury evaluation for accurate prognosis and surgical planning.

Received March 5, 1996; accepted after revisionMay 16,1996.

t Section of Neuroradiology, Department of Diagnostic Ra-

diology, Yale University School of Medicine, 333 Cedar St..New Haven, CT 06510. Address correspondence to A. T.Walker.

2The Interventional Neuroradiology Service, Departmentsof Diagnostic Radiology and Surgery (Neurosurgery), YaleUniversity School of Medicine, New Haven, CT 06510.

3Section of Neurosurgery, Department of Surgery, YaleUniversity School of Medicine, New Haven, CT 06510.

4Department of Orthopaedics and Rehabilitation, Yale Uni-versity School of Medicine, New Haven, CT 06510.

5Section of Neuroradiology, Department of Radiology.

Hartford Hospital, 180 Seymour St., Hartford, CT 06106.

AJR 1996:167:1283-1287

0361-803X196/1675-1283

© American Roentgen Ray Society

R ecent advances in microneurosur-

gery have made exploration and

repair of traumatic and birth-

related brachial plexus injuries possible I I-

3j. Adequate surgical planning requires dii-

ferentiation of preganglionic from postgan-

glionic lesions. Avulsion of ventral or dorsal

nerve rootlets from the spinal cord results in

preganglionic nerve root injury with no

potential for nerve regeneration. In these

cases. surgical treatment consists of neuroti-

zation. or rnicrosurgical reinnervation of the

distal portions of the brachial plexus by

nerve transfer ftotii spinal accessory. cervical

plexus. or intercostal nerves [ l-3J. Postgan-

glionic brachial plexus lesions may he

treated by microsurgical neurolysi s of

perineural scar tissue if nerve continuity is

maintained or by interpo)sition nerve grafting

if the nerve is completely transected ( I -31.Myelography and CT myelography have

been the neuroradiologic examinations of

choice for evaluating brachial plexus tnjuries.

MR imaging has also been shown to be useful

in evaluating brachial plexus injuries 4-61.

The diagnosis of nerve root avulsion has gen-erally been based on showing def�rmity of the

suharachnoid space or a pseudoii�eningocele.

Although a strong association exists between

nerve root avulsion and pseudomeningoceles.

a significant percentage of avulsions show no

evidence of pseudomeni ngocele. and pseudo-

If�1��Surgica1 and CT Myelographic Correlation

Surgical Findings

CT Myelographic Findings

CompleteAvulsion

Partial AvulsionInadequate

EvaluationLevel Not Included Normal

Complete avulsion

Partial avulsion

Normal

20

1

0

0

0

0

1

1

2

1

0

3

0

1

50

.. :;

� . � . �0

Walker et al.

1284 AJR:167, November 1996

nieningoccles can occur withoitt nerve r(x)t

avulsion 17-91.Because of the �vider range o1 available

therapeutic options. appropriate surgical plan-

fling and deterniination of prognosis require

accurate deterniination of spinal nerve root

integrity at each level fioiii C5 to T I

Although a recent report documented the use-

fulness of plain film myelography in specifi-

cally evaluating the cervical nerve rootlets 171.

adequate cervical nyelography is often dilti-

cult to perlorni in acutely injured individuals

and small infants. Our objective was to evalu-

ate the efficacy of thin-section high-resolution

CT niyelography for detecting cervicotho-

racic nerve rootlet avulsion in birth palsy and

brachial plexus injury after trauma.

Materials and Methods

Eight tiutle patients ( 8 nionths to 67 years old)

with cotiiplete or incotiiplete brachial plexits

injury were evaluated with cervical tnyelography

and high-resolution CT myelography before sur-

gical exploration and repair. Seven injuries were

sustained in motor vehicle accidents. and the

other was related to traumatic birth. Cervical

tiyelography was performed with a water-soluble

contrast agent (Oninipaque I 80: Nycomed. New

York. NY: 10-14 ml in adults and 3-4 ml ininfants). After fluoroscopic and plain film evalua-

tion. patients underwent CT scanning. Contiguous

axial images were obtained froni C3 to T2 at I-rntii intervals with I -turn slice thickness in infants

and at 2- to 3-miii intervals with 3-mm sltce

thickness in adults. using the standard. detail. or

high-resolution hone reconstruction algorithm on

a 9f�()() or HiSpeed Advantage scanner General

Electric Medtcal Systems. Mtlwaukee. WI. The

CT scans were tncorrectlv intttated at the C4 ver-

tebral body level tn the earliest two examtnattons

in the sertes. Myelogratiis and CT mvelograms

were retrospectively evaluated for nerve rootlet

avulsion, traunuttic pseudotiieningocele. and

deformity 0) the suharaclitioid space by two neti-

roradtologtsts who ltd not know surgtcal find-

Ings. A level was deeti�ed inadequately shown

wheti neither exatiutier cottkl detect the contralat-

eral normal nerve rootlets withtn the subarach-

tioid space. Radiologic findings were correlated

with surgical findings and intraoperative soma-

tosensorv evoked potentials.

Results

Seventy-two (95Y ) of 76 imaged cervi-

cothoracic levels were adequately shown on

CT myelography in eight patients with uni-

lateral brachial plexus injury. In two

patients the CT scan was initiated below the

rootlet origins of the C5 nerve roots. In two

patients the TI nerve rootlets were made-

quately shown bilaterally because of beam

hardening and streak artifact. Nerve rootlet

avulsion. or preganglionic disruption. was

diagnosed at 2 1 levels by the lack of contig-

uous ventral and dorsal rootlets between the

spinal cord rootlet entry or exit zone and the

neural foranien (Table I ). Small noncontig-

uous fragments were intermittently seen at

the avulsion levels and were thought to rep-

resent small residual tags of rootlet tissue or

fibrotic scar. Pseudomeningocele or defor-

mity of the subarachnoid space was seen at

I 2 of the avulsion levels (Fig. I ). However,

at nine levels no evidence of pseudomenin-

gocele or significant deformity of the sub-

arachnoid space was seen (Fig. 2). No

instance of pseudomeningocele with intact

nerve rootlets was seen in our series. Surgi-

cal exploration and intraoperative soma-

tosensory evoked potentials showed

preganglionic nerve root injury at 22 levels,

consistent with nerve rootlet avulsion

(Table I ). Partial nerve rootlet avulsion was

diagnosed at three additional levels by

visual continuity of some nerve rootlets and

by the presence of diminished but main-

tai ned somatosensory evoked potentials.

Twenty of the 22 surgically proven avul-

sions were correctly identified at CT myel-

ography. The two avulsions not detected

occurred at levels not adequately evaluated

on the CT myelograms, one at a level not

included on a scan, and the second at a level

inadequately evaluated because of an arti-

fact. None of the three partial preganglionic

injuries were correctly identified on CT

Fig. 1.-Left C7 nerve rootlet avulsion and associatedpseudomeningocele in 10-month-old boy with left

brachial plexopathy after traumatic delivery.A, Axial CT myelogram at level of C5 vertebral bodyshows normal right Cl nerve rootlets exiting and en-tering cervical cord (arrowl. Note that left C7 nerverootlets are not seen.B, Axial CT myelogram at level of C6-C7 neural fo-ramina shows normal right Cl nerve rootlets exitingthecal sac (closedarrow). Note pseudomeningoceleon left (open arrow). No left C7 nerve rootlets areseen, consistentwith avulsion.

CT Myelography of Nerve Rootlet Avulsion

AJR:167, November 1996 1285

Fig. 2.-Avulsion of right Cl nerve rootlets withoutpseudomeningocele in 23-year-old man with right bra-chial plexopathy after motorcycle accidentA, Axial CT myelogram at level of C6 vertebral bodyshows absence of right Cl nerve rootlets entering andexiting cervical cord. Note normal left Cl rootlets.B, Axial CT myelogram at level of C6-C7 neural foram-na shows absence of right Cl rootlets and normal

right Cl root sleeve (open arrow), without deformity ofsubarachnoid space or pseudomeningocele.Closed arrow = left Cl rootlet.

Fig. 3.-Surgically proven partial avulsion of left Cl nerve rootlets interpreted as complete avulsion on CT myelogram in 67-year-old man with left brachial plexopathy aftermotor vehicle accidentA, Axial CT myelogram at level of C6 vertebral body shows absence of left C7 nerve rootlets. Streak artifact and narrowing of spinal canal limit examination, but normalright Cl rootlets are seen (arrow).B and C, Axial CT myelograms at level of C6-C7 neural foramina show minimal linear density, which may represent residual ventral rootlets exiting cord (arrow in B), butthey are difficult to differentiate because of streak artifact. Note normal left Cl root sleeve (arrow in C).

myelography (Table 1). One level was

interpreted as a complete avulsion (Fig. 3).

one as normal (Fig. 4), and one level was

inadequately evaluated. Excluding the onesurgically proven avulsion that was not

included on the patient’s CT myelogram.

we found a 95% sensitivity and 98% speci-ficity for the detection of complete nerve

rootlet avulsion on CT myelography.

Discussion

The brachial plexus is formed by the yen-

tral rami of the fifth through the eighth cervi-

cal and first thoracic spinal nerves. The fifth

and sixth cervical nerve rootsjoin to form the

superior or upper trunk. The seventh rootcontinues as the intermedius or middle trunk.

and the eighth cervical and first thoracic roots

join to fbrm the inferior or lower trunk. The

trunks further divide into anterior and poste-

nor divisions, forming the lateral. medial.

and posterior cords. Traction and compres-

sion forces may result in brachial plexus inju-

ries at any of these levels. Adequate surgical

planning requires differentiating pregangli-

onic lesions of the nerve rootlets from post-

ganglionic injury. Surgical treatment of

preganglionic lesions consists of neurotiza-

tion by nerve transfer of spinal accessory,

cervical plexus. or intercostal nerves to distal

portions of the brachial plexus. This transfer

is performed to try to restore some level of

elbow flexion to the paralyzed limb. Neuroti-

zation by nerve transfer is used because com-

plete avulsion of nerve rootlets confers no

possibility of nerve regeneration I l-3J. Post-

ganglionic lesions may be treated segmen-

tally by microsurgical removal of perineural

scartissue and adhesions (neurolysis) if’ nerve

continuity is maintained, or by interjxsition

nerve grafting at levels of complete brachial

plexus transection I 1-31.

Prior reports have documented the impor-

tance of showing cervical nerve rootlet avul-

sion in birth palsy and posttraumatic brachial

plexus injury (7, 81. The demonstration of aposttraumatic pseudomeningocele is not suf’-

ficient for diagnosing nerve rootlet avulsion.

In the 21 instances of nerve rootlet avulsion

seen in our series. nine (4Y4 ) had no associ-

ated deformity of the subarachnoid space or

pseudomeningocele . Other studies havereported nerve rootlet avulsion without

pseudomeningocele in 20�% and only mini-

mal deformity of the subarachnoid space in44c/� of cases 16-91. The length of time

Fig. 4.-Surgically proven partial avulsion of left Cl nerve rootlets interpreted as normal on CT myelogram in 21-year-old man with left brachial plexopathy after motorcycle accident.A, Three-millimeter axial CT myelogram at level of C6 vertebral body shows some left C7 nerve rootlets. Infoldingof dura near left Cl nerve root sleeve origin may mimic exiting ventral rootlets (arrow). One-millimeter imagesmay have been useful in limiting partial volume averaging and possibly detecting asymmetry of left Cl rootlets tosuggest partial avulsion.B, Axial CT myelogram at level of C6-C7 neural foramina shows normal left Cl root sleeve.

Walker et al.

1286 AJR:167, November 1996

required for pseudomeningocele develop-

ment is unknown. and no patient in our series

was examined at two different times to deter-

mine whether delayed pseudomeningoceleformation occurs. However. we found no

difference in the incidence of nerve rootlet

avulsion without pseudomeni ngocele

between patients imaged acutely. within 8

weeks of injury. and those imaged a mean of

4-5 months after injury.

A recent report has emphasized the

i mportance of meticulous myelographic

evaluation of the individual nerve rootlets

in patients with brachial plexus injury and

suspected avulsion [71. However, we have

found that a significant number of cervical

myelograms in these patients are made-

quate to evaluate the nerve rootlets at all

levels. especially in stiiall infants under

general anesthesia and in patients with

acute multisystem trauma (Fig. 5). MR

imaging has recently been shown to be as

sensitive as plain f’ilm myelography in

showing nerve rootlet avulsion in the upper

cervical spine 161. However. no compari-

son of MR imaging to CT myelography

was made. and the study was limited to

evaluation of the C5 and C6 nerve rootlets

because visualization of the lower rootlets

was limited by decreased signal-to-noise

ratios and loss of soft-tissue contrast.

Although MR imaging may improve with

further technical developments. it is cur-

rently unable to evaluate the status of all

brachial plexus rootlets at each level.

Even in cases in which the plain film myel-

ographic images were suboptimal because of

difficulty in visualizing the small nerve root-

lets in infants, poor contrast opacification of

the cervical subarachnoid space, or immobil-

ity of the patient. CT myelography was able to

show ventral and dorsal rootlets exiting or

entering the spinal cord at 95% of the levels

evaluated (Fig. 5). Both instances of made-

quate evaluation occurred at TI because of

beam hardening and streak artifact caused by

the shoulders. We now position patients

obliquely in the CT scanner to offset the

shoulders and prevent alignment of the two

sides on a single axial image.

In any evaluation of brachial plexus inju-

ries. all contributing cervicothoracic nerve

Fig. 5.-Right Cl and C8 nerve rootlet avulsion in 27-year-old man with right brachial plexopathy after motorcycle accident.A, Anteroposterior view from cervical myelogram shows small pseudomeningoceles at C6-C7 and Cl-Ti on right )arrows), but nerve rootlets are not well seen. Study wasmarkedly limited by patient immobility caused by multiple acute fractures.B, Coronal reconstruction of CT myelogram shows avulsion of right Cl and C8 nerve rootlets with associated pseudomeningoceles arrows).

C. Axial CT myelogram at level of C6-C7 neural foramina shows avulsion of right Cl rootlets with pseudomeningocele arrow) and normal left Cl rootlets.

CT Myelography of Nerve Rootlet Avulsion

AJR:167, November 1996 1287

rootlet origins from C5 to TI must be

included. In two of our early cases, the scan

was initiated below the origin of the CS nerve

rootlets, which is typically as high as C3

because of the oblique downward course of

the nerve rootlets in the subarachnoid space.

Incomplete evaluation of all contributing 1ev-

els limits presurgical planning and may neces-

sitate a more extensive surgical exploration.

Despite reports that CT myelography is

unable to delineate individual nerve rootlets

[7, 10], we have found high-resolution CT

myelography with thin contiguous axial see-

tions to be highly useful for evaluating

nerve rootlet avulsions in brachial plexus

birth palsies and posttraumatic brachial

plexus injuries. We found a 95% sensitivity

and 98% specificity for complete nerve

rootlet avulsion with a positive predictive

value of 95% and a negative predictive

value of 98%. Preoperative CT myelogra-

phy allows more complete injury evaluation

for accurate prognosis and surgical plan-

ning. Detection of partial avulsion injury

was much less promising, with none of the

three instances in our series correctly identi-

fled, although one occurred at a level made-

quately evaluated. Partial avulsion is also a

management dilemma, because the potential

for regeneration is difficult to predict and

many cases show no significant functional

recovery. The detection of partial avulsions

may be aided by correlation with plain film

myelography or by decreasing partial-vol-

ume artifact with 1-mm axial images at sus-

picious levels, but their presence in our

series underscores the continued need for

careful surgical exploration and somatosen-

sory evoked potentials for complete analysis

of brachial plexus injuries.

In summary, we found high-resolution CT

myelography helpful when evaluating brachial

plexus injuries. We recommend the use of 1-

mm contiguous axial images in infants and a 3-

mm slice thickness in adults with a 2-mm over-

lapping interval. A high-resolution reconstruc-

tion algorithm is used to improve visualization

of the individual nerve rootlets. In adults,

repeat imaging at selected levels with 1-mm

contiguous axial images may be of further help

if subtle injury is suspected, or if the imaging

findings do not correlate with physical exami-

nation or electromyelographic data. Imaging

from the C3 vertebral body to the superior

aspect of T2 is required to include all nerve

rootlet contributions to the brachial plexus.

References

1. Millesi H. Brachial plexus injury in adults: opera-

tive repair. In: Gelberman RH, ed. Operative

iieri’e repair and reconstruction. Philadelphia:

Lippincott, 1991:1285-1301

2. Samardzic M. Grujicic D, Antunovic V. Nerve

transfer in brachial plexus traction injuries. J

Neurnsurg 1992:76: 19 1-197

3. Laurent JP. Lee R, Shenaq S. Ct al. Neurosurgical

correction of upper brachial plexus birth injuries.

J Neurosurg 1993:79:197-203

4. Popovich MJ, Taylor FC, Helmer E. MR imaging

of birth-related brachial plexus avulsion (abstr).

AJNR 1989: lOlsuppll:S98

5. Miller SF, Glasier CM. Griebel ML. Boop FA.

Brachial plexopathy in infants after traumatic

delivery: evaluation with MR imaging. Radiology

1993:189:481-484

6. Ochi M, lkuta Y, Watanabe M, Kimori K, Itoh K.

The diagnostic value of MRI in traumatic hr�chial

plexus injuty. J HandSurg (BrJ l9�:l9-B:55-59

7. Ha.shimoto T, Mitomo M. Hirabuki N, et al. Nerve

root avulsion of birth palsy: comparison of myelog-

raphy with CT myelography and somatoscnsory

evoked potential. Radiolog�’ 1991:178:841-845

8. Trojaborg W. Clinical. electrophysiological. and

myelographic studies of 9 patients with cervical

spinal root avulsions: discrepancies between

EMG and x-ray findings. Muscle Nerve 1994:

17:913-922

9. Davies ER, Sutton D, Bligh AS. Myelography in bni-

chial plexus injury. BrJ Radial 1%6:39:362-37l

10. Vielvoye GJ. Hoffmann CFE. Neuroradiological

investigations in cervical rsx�t avulsion. Cli,, Ne,,-

rol Neurosurg 1993:95lsuppll:S36-S38