BRACHIAL PLEXUS IMAGING - PowerPoint Presentation

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BRACHIAL PLEXUS

IMAGING

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BRACHIAL PLEXUS IMAGING :

Basic anatomy

Pathologies affecting Brachial Plexus

Modalities of Imaging :

Conventional methods.

Ultrasound

CT and CT

Myelography

MR

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ANATOMY : FORMATION :

Derived from anterior primary rami of C5 to C8 and T1.Also has variable contributions from C4 and T2.Pre-fixed Plexus : derived from C4 to C8. Is associated with presence of cervical rib.Post-fixed Plexus : derived from C6 to T2. Is associated with an anomalous 1st rib.

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ANATOMY : COMPONENTS - RTDC

Roots : 5 roots – C5,C6,C7,C8 and T1.Trunks : 3 trunks – Upper,Middle and Lower.Divisions : 2 divisions of each trunk – Anterior and Posterior.Cords : 3 cords – Lateral, medial and posterior.

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ANATOMY : RELATIONS : ROOTS :

Emerge from the intervertebral foramina.C5,C6 and C7 root pass behind the foramen transversarium of respective Cx vertebra and then lie over the gutter between the anterior and posterior tubercles of the corresponding transverse process.Then become sandwiched between the Scalenus anterior and medius muscles.Roots lie above the second part of subclavian artery

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ANATOMY : RELATIONS : ROOTS :

INTERVERTEBRAL FORAMINA  INTERSCALENE TRIANGLERoots within groove are contained in a fibro-fatty space between 2 layers of fibrous tissue – Interscalene sheath / space.Covers the plexus from here upto the apex of axilla.Forms the basis of Interscalene brachial plexus block.Related to Roots, Trunks and Divisions of BP.

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ANATOMY : RELATIONS : TRUNKS :

INTERSCALENE TRIANGLE

 LATERAL MARGIN OF 1

st

RIB

Formed within Interscalene triangle – within the

fascial

sheath.

Pass in a closely grouped cluster – downwards and laterally-across the base of the posterior triangle and then across the 1

st

rib.

Within posterior triangle – superficially placed covered only by

skin,platysma

and deep fascia.

Across the 1

st

rib – Upper and Middle trunk lie above the

subclavian

artery, Lower trunk lies behind artery and may groove 1

st

rib behind

subclavian

groove.

Divides into Divisions at – lateral margin of 1

st

rib, behind the clavicle.

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ANATOMY : RELATIONS : DIVISIONS :

LATERAL BORDER OF 1

st

RIB

 APEX OF AXILLA.

Situated behind the Clavicle,

Subclavius

muscle and

Suprascapular

vessels.

Project

into the axilla through its apex – then regroup to form the cords.

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ANATOMY : RELATIONS : CORDS :

WITHIN AXILLA

Lateral, Medial and Posterior : Named after their relation with the axillary artery.

Initially the medial cord lies posterior to axillary artery and lateral and posterior cord lie lateral to axillary artery.

Later they assume the positions as per their name.

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ANATOMY : BRANCHES OF BRACHIAL PLEXUS :

FROM ROOTS : Nerve to longus cervicisNerve to serratus anteriorNerve to scalene musclesNerve to RhomboidsContribution to phrenic nerve.FROM TRUNKS :Nerve to SubclaviusSuprascapular nerve.

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ANATOMY : BRANCHES OF BRACHIAL PLEXUS :

FROM CORDS :LATERAL CORD {LML}:Lateral pectoral nerve Musculocutaneous nerveLateral head of median nerveMedial cord {Medial4 Ulna}: Medial pectoral nerveMedial cutaneous nerve of armMedial cutaneous nerve of forearmMedial head of median nerveUlnar nerve

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ANATOMY : BRANCHES OF BRACHIAL PLEXUS :

FROM CORDS :3. Posterior cord : Upper and lower subscapular nerveNerve to Latissimus dorsiAxillary nerveRadial nerve

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Pathologies affecting Brachial Plexus :

Traumatic :

Nerve root avulsion

Impingement of

neighbouring

structures – Clavicular fracture callus, Hematoma, Vascular – aneurysms.

Nontraumatic

:

Radiation induced changes

Viral / Idiopathic

plexitis

Neoplastic :

Schwannoma

Plexiform

neurofibroma

Lipoma

/

Liposarcoma

Pancoast’s

tumor involving BP

Metastasis.

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IMAGING : CONVENTIONAL METHODS

Are of limited use.

Provide indirect evidence of BP pathology rather than its actual demonstration.

X-RAYS :

Specific sites of involvement may raise suspicion about possibility of brachial plexus involvement.

Chest

Xray

: S/o Pancoasts tumour may raise doubts about BP involvement.

Clavicular fractures : May be associated with BP injury

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IMAGING : CONVENTIONAL METHODS

CONVENTIONAL MYELOGRAPHY :Rarely needed and performed nowadays.Grainger “ May be needed if MRI is equivocal for BP avulsion injury.Most reliable sign is the failure to visualise the intradural rootlets of avulsed spinal nerves, when the contralateral uninvolved rootlets are clearly visible.”Finding of Pseudomeningoceles is also s/o Root avulsion, however not specific as both may exist irrespective of each other too.Anterior roots are far more vulnerable to avulsion than the posterior roots.AP view of Cervical myelogram : small pseudomeningoceles on right at C6-C7 and C7-T1 levels.

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IMAGING : HIGH RESOLUTION ULTRASOUND

HRU refers to use of high

frequency probes (7 – 15

Mhz

).

Based on identification of “Typical characteristics of peripheral nerves :”

More echogenic than muscles but less echogenic than tendons.

Honeycomb appearance

Less mobile than tendons.

Characteristics of diseased nerves :

Nerve enlargement

Hypoechoic

signal resulting from nerve edema.

Discontinuity of nerve

fascilcles

- Complete or Partial.

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IMAGING : 2-D ULTRASOUND

Probe is placed in 30 degree angle in the coronal oblique plane in the mid-lower neck behind the sternocleidomastoid

muscle.The

3 trunks are seen to lie in the interscalene triangle.

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IMAGING - 2-D ULTRASOUND

Start with 30 degree angle in the oblique coronal plane identifying trunks in the interscalene triangle and then trace them proximally and distally.

Patient position : Sitting position with head neutral or turned to opposite side by 10 – 20 degrees.

Roots C8-T1 are most difficult to

visualise

due to greater penetration required.

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IMAGING : 2-D ULTRASOUND

Swollen and distorted C6 root with indistinct root borders in the

inferomedial

region.

Normal C7 root.

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IMAGING : 3 – D ULTRASOUND

HR Freehand

Stradix

– 3D ultrasound system – Cambridge University Engineering Department.

Preserves much of the 2D data resulting in a highly accurate 3D data set with a point location accuracy of within 0.5mm.

Basic technique remains the same with patient seated, head rotated 30 degrees to contralateral side and arms by the side.

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IMAGING : 3 – D ULTRASOUND

Probe placed in axial plane at apex of posterior triangle and swept across it into the supraclavicular fossa now in the sagittal plane.

At the end of sweep transducer is angled anteriorly to

visualise

structures lying deep to lateral third of clavicle.

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IMAGING : 3 – D ULTRASOUND

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IMAGING : 3 – D ULTRASOUND

Whole data set obtained

 Structures Manually segmented  Series of representative outlines obtained.

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IMAGING : 3 – D ULTRASOUND

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IMAGING : 3 – D ULTRASOUND

Surface rendered 3D reconstruction : Relation of BP to segments of carotid and

subclavian

artery and 1

st

rib is demonstrated from a lateral and antero-posterior perspective.

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IMAGING : 3 – D ULTRASOUND

Advantages of 3D ultrasound :

Allows frame by frame analysis of anatomy – better

deliniation

and better

idetification

of anatomical variations.

Spatial reconstruction can be used in radiotherapy planning.

With the advent of 3D conformal

radiotherapy and

intensity-modulated radiotherapy (IMRT

) ,

a spatial map of the brachial plexus could

be imported

into the planning system and the dose to

the plexus

adjusted

accordingly.

Better resolution by elimination of operator

dependant

factors such as probe pressure and tremors.

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IMAGING : CT STUDIES

CT scans were used for BP imaging but :

Limited to the axial plane imaging. May be overcomed by recent softwares enabling reconstruction along

C

or

and Sag planes.

Dense shoulder bones and contrast within the

Subclavian

/Axillary vessels cause severe beam hardening artefacts and degrade the image quality.

Poorly timed bolus of contrast may make the identification of neighboring vessels difficult. These vessels need to be identified for correct evaluation of the BP.

Axial CT views are, in some centers, still considered as the Standard Reference in the pre-op assessment of Cx nerve root involvement in trauma cases.

Due to greater soft tissue resolution and multiplanar imaging MRI has gradually replaced CT in evaluation of pathologies of BP.

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IMAGING : AXIAL CT MYELOGRAPHY

TECHNIQUE AND RESULTS :

Contiguous axial images were obtained from C3 vertebra to upper part of T2 vertebra.

For Infants : 1 mm thick sections at 1mm intervals.

For Adults : 3 mm thick sections at 3 mm intervals.

High resolution reconstruction algorithm used.

Results : For complete nerve root avulsions :

Sensitivity and Specificity of 95 % and 98 % resp.

Positive and Negative Predictive value of 95 % and 98 %.

Partial nerve root avulsions are difficult to evaluate.

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IMAGING : CT MYELOGRAPHY

Axial CT

Myelogram

at C6-C7 neural foramina : Shows normal exiting right C7 nerve

rootlets.Nonvisualisation

of nerve rootlets on left and the presence of

pseudomeningocele

is s/o Avulsion.

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IMAGING : CT MYELOGRAPHY

Axial CT

myelogram

at C6-C7 neural

foraminal

level :

Nonvisualisation

of right C7 rootlets but with normal appearing right C7 root

sleeve,without

any deformity of subarachnoid space or

pseudomeningocele

.

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IMAGING : CT MYELOGRAPHY

LIMITATIONS OF AXIAL CT MYELOGRAPHY :

Spinal nerve rootlets run in an oblique

direction,so

in axial plane entire

visualisation

from cord to exit foramina not possible.

As seen previously results though good for complete avulsion

injury,are

poor for partial injuries.

These shortcomings can be overcome by using Coronal and Oblique coronal reconstruction images of the Axial CT

Myelogram

.

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IMAGING : CT MYELOGRAPHY

Coronal and Oblique coronal view delineate ventral and dorsal roots in detail respectively.

Number,Size

of rootlets and Connection with cord are important assessment parameters.

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IMAGING : CT MYELOGRAPHY

At C5 level, reduced number or redundant rootlets are well

visualised

.

In most cases these findings corresponded to intra-op finding of partial pre-ganglionic avulsion injury.

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IMAGING : MRI

WHY MR

iS

THE BEST FOR BP IMAGING ?

Conventional radiography is far less sensitive.

CT has improved sensitivity but has poor soft tissue resolution to identify nerves.

With MRI detailed evaluation of all the components of brachial plexus –

Roots,Trunks,Divisions

and Cords – is possible.

Has excellent soft tissue contrast.

Has advantage of

Multiplanar

imaging.

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IMAGING : MRI : IMAGING TECHNIQUE AND PARAMETERS :

Radiofrequency coil : Surface coil has better resolution but has greater artefacts.Body coil has inferior resolution but has very less artefacts.Hence combination of both is used : Surface coil used for imaging spinal cord and exiting roots, Body coil used for BP lateral to interscalene triangle.

Parameters/Plane

Coronal

Oblique

sagital

FOV

17 – 22 cm

14

– 17 cm

Section thickness

4

mm

4 mm

Intersection

gap

0 – 0.5 mm

1 – 1.5 mm

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IMAGING : MRI : IMAGING TECHNIQUE AND PARAMETERS :

Orientation :

Direct coronal plane imaging and Oblique

sagital

plane imaging is preferred as BP runs in a coronal plane from medial-superior to lateral-inferior

direction.The

individual nerve roots can be

visualised

in Axial plane

alongwith

sagital

views of the exiting nerve roots.

Sequences :

Coronal T1 and STIR.

Sag T1

Axial T1 and T2 fat sat or STIR images.

Post contrast T1fat sat if required

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IMAGING : ANATOMY

Sagittal images – At level of Intervertebral foramen and at Interscalene triangle.

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IMAGING : ANATOMY

Three trunks at lateral border of middle scalene muscle.

Divisions are formed just at the level where the BP crosses the clavicle.

Lateral to 1

st

rib cords are formed, surrounding the axillary artery.

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IMAGING : ANATOMY

Coronal image : Showing the retro-

clavicular

,

infraclavicular

portions of the BP.

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IMAGING : ANATOMY

Coronal images : At level of middle scalene muscle and at level of anterior scalene muscle.

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IMAGING : MRI

NERVE ROOT AVULSION :

Result most commonly traction injury

With complete

avulsion,nerve

roots retract leaving behind fluid filled

pseudomeningoceles

.

Nerve avulsions at root entry zones may lead to adjacent SAH, Edema Hemorrhage in cord.

COR T2WI showing

pseudomeningocele

from avulsion of the left C7 nerve root.

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IMAGING : MRI

NERVE ROOT AVULSION :

Axial T1W image showing

pseudomeningocele

in the region of avulsed nerve root.

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IMAGING : MRI

CLAVICULAR FRACTURE :

Shows excess callus formation which is contiguous with the brachial plexus.

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IMAGING : MRI

VASCULAR INJURIES AFFECTING BP :

Subclavian artery injury may cause

pseudoaneurysm

formation resulting in mixed sensory and motor neuropathy

BP may also be damaged during placement of central catheters

Coronal T1WI showing a round laminated appearing

Rt

subclavian

artery

pseudoneurysm

.

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IMAGING : MRI

VASCULAR INJURIES AFFECTING BP :

Sag T1WI shows typical concentric layers of varying signal abnormality.

The BP is compressed and is not

visualised

.

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IMAGING : MRI

VIRAL / IDIOPATHIC PLEXITIS :

Predominantly sensory and have an

insidius

onset.

Most patients are in age 30 – 70

yrs

and they resolve spontaneously.

COR FATSAT T2WI showing thickening and increased signal in roots and trunks of left BP.

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IMAGING : MRI

RADIATION INDUCED BRACHIAL PLEXITIS :Occurs with doses greater than 6000cGy.If presents in Acute phase, is permanent due to blood vessel injury and nerve ischemia.If subacute(> 6m after exposure), is usually transient and reversible.Most radiation induced plexopathies are predominantly sensory.COR FATSAT T2WI shows increased signal intensity from the retroclavicular portion of BP in a pt op for Ca Breast and on radiotherapy.

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IMAGING : MRI

NEOPLASMS :BRACHIAL PLEXUS SCHWANNOMA:Most common primary tumour of BP.Most commonly involve the roots and trunks.Most common present as sensory plexopathy. Typical appearance is extension into and expansion of the corresponding neural foramen with nonspecific enhancement pattern.COR T2W image showing a mass in the region of roots and trunks of BP and extending into the neural foramen.

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IMAGING : MRI

NEOPLASMS :BRACHIAL PLEXUS SCHWANNOMA :Axial noncontrast T1W image in same patient shows schwannoma expanding the neural foramen.

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IMAGING : MRI

NEOPLASMS :BP PLEXIFORM NEUROFIBROMAS :Found only in NF 1 and are a hallmark of the disease.Initially only mild enlargement of DRG is present.Later attain large size,may be bilateral and involve all of the plexus.Enhancement is variable but significant change in size and enhancement may indicate malignant transformation.Masses arising between the Anterior – Middle –Posterior scalene muscles are nearly always primary in the trunks.Axial T2WI shows extensive bilateral,bright Plexiform neurofibromas

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IMAGING : MRI

NEOPLASMS :BP LIPOMA AND LIPOSARCOMA :Lipoma :Common, asymptomatic unless very large and do not enhance and have a homogenous appearance with a few inner strands.Liposarcoma :Rare,inhomogenous contrast enhancement,aggressive appearance and invade adjacent structures Cor T1W noncontrast image appearing bright (fatty),BP lies under it.COR T1W fat suppressed postcontrast image – nodular peripheral enhancement.BP also enhances s/o invasion.

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IMAGING : MRI

NEOPLASMS :BP METASTASES :Occur in elderlyMost are from breast,lung and lymphoma.May present as focal masses – due to large tumourous lymph nodal masses.Or as diffusely infiltrating the plexus – difficult to distinguish from post-irradiation changes.COR T1W noncontrast image showing a mass which displaces the cords of BP superiorly

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IMAGING : MRI

NEOPLASMS :BP METASTASES :Postcontrast fatsuppressed T1WI showing 2 enhancing masses with thick and enhancing cord of BP s/o involvement.

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IMAGING : MRI

NEOPLASMS :PANCOAST’S TUMOR INVOLVING BP :MC arise in the apical pleuru-pulmonary groove (Superior sulcus) and are squamous,adenoca and large cell carcinomas in descending freq.When involve the BP (Stage T4) prognosis is poor.Mixed sensorymotor plexopathy common.In 25 % it extends intraspinally causing cord compression.COR T1W noncontrast image showing the normal Rt Interscalene fat triangle.on Left a large pancoast’s tumour has invaded and obliterated this fat.

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IMAGING : MRI

NEOPLASMS :PANCOAST’S TUMOR INVOLVING THE BP :SAG T1W noncontrast image showing the tumor completely encircling the subclavian artery.BP not seen as it is diffusely infiltrated.

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