Chapter 8 Spinal Nerve Roots Abdullah Al-Salti R2 24 February 2010.

Chapter 8Chapter 8Spinal Nerve RootsSpinal Nerve Roots

Abdullah Al-Salti R2Abdullah Al-Salti R224 February 201024 February 2010

Outline:Outline:

1.1. The anatomy of the The anatomy of the spinal nerve roots .spinal nerve roots .

2. Their relation to the vertebral structures.

3.3. Regions of Regions of innervations .innervations .

4. Common clinical disorders.

31 pairs spinal nerves: 31 pairs spinal nerves: There are There are 8 cervical8 cervical (C1-C8), (C1-C8),12 12

thoracicthoracic (T1-T12), (T1-T12),5 lumber5 lumber (L1- (L1-L5),L5),55 sacralsacral(S1-S5)and (S1-S5)and 1coccygeal1coccygeal(Co1)spinal segments.(Co1)spinal segments.

Formation: Formation: each spinal nerve is each spinal nerve is formed by union of anterior and formed by union of anterior and posterior roots at intervertebral posterior roots at intervertebral foramen foramen – The anterior rootThe anterior root －－ contains motor contains motor

fibers for skeletal muscles. Those from fibers for skeletal muscles. Those from T1 to L2T1 to L2 contain sympathetic fibers; contain sympathetic fibers; S2 S2 to S4to S4 also contain also contain parasympathetic parasympathetic fibers.fibers.

– The posterior rootThe posterior root －－ ccontains ontains sensory fibers whose cell bodies are in sensory fibers whose cell bodies are in the spinal ganglion.the spinal ganglion.

AAnatomy Of The Spinal Nerve Rootsnatomy Of The Spinal Nerve Roots

General DescriptionGeneral Description In adults , the spinal cord normally

ends with the conus medullaris at the level of the L1 or L2 vertebral bones.

The roots of the cauda equina are The roots of the cauda equina are organized such that the most organized such that the most centrally located roots are from the centrally located roots are from the most caudal segments of the spinal most caudal segments of the spinal cord.cord.

Sensory and motor nerve roots arise from each segment of the spinal cord except for the C1 and Co1 segments,which have no sensory roots.

The cervical enlargements (The cervical enlargements (C5-C5-T1T1))gives rise to the nerve roots for gives rise to the nerve roots for the arms ,and the lumbosacral the arms ,and the lumbosacral enlargments (enlargments (L1-S3L1-S3)gives rise to the )gives rise to the nerves roots for the legs.nerves roots for the legs.

Vertebral Structures.Vertebral Structures. Each vertebral bone has a Each vertebral bone has a

sturdy cylindrical vertebral sturdy cylindrical vertebral body located anteriorly.body located anteriorly.

Posteriorly,the neural Posteriorly,the neural elements are surrounded by elements are surrounded by an arch of bone formed by an arch of bone formed by the (pedicles,transverse the (pedicles,transverse processes,laminae,and processes,laminae,and spinous processes).spinous processes).

The superior and inferior The superior and inferior articular processes or facet articular processes or facet joints form additional points joints form additional points of mechanical contact of mechanical contact between adjacent vertebrae.between adjacent vertebrae.

Intervertebral disc (nucleus Intervertebral disc (nucleus pulposus surrounded by pulposus surrounded by annulus fibrosis).annulus fibrosis).

General DescriptionGeneral Description The spinal cord runs through the spinal The spinal cord runs through the spinal

canal (vertebral foramen) and is canal (vertebral foramen) and is surrounded by pia,arachnoid ,dura surrounded by pia,arachnoid ,dura mater .mater .

Unlike in the cranium , there is a layer of epidural fat between the dura and the periosteum in the spinal canal,which is a useful landmark on MRI scans.

There is a valveless meshwork of There is a valveless meshwork of epidural veins called epidural veins called Batsons plexusBatsons plexus that is thought to play a role in the that is thought to play a role in the spread of metastatic cancers and spread of metastatic cancers and infections in the epidural space.infections in the epidural space.

Ligamentum flavum is particularly prominent in cervical and lumber regions and can sometimes become hypertrophied and contribute to spinal cord or nerve root compression.

The nerve roots exit the spinal canal The nerve roots exit the spinal canal via the neural (intervertebral) via the neural (intervertebral) foramina.foramina.

General DescriptionGeneral Description Disc herniation are most Disc herniation are most

common at the cervical and common at the cervical and lumbosacral levels.lumbosacral levels.

For both cervical and For both cervical and lumbosacral disc herniations, lumbosacral disc herniations, the nerve root involved the nerve root involved usually corresponds to the usually corresponds to the lower of the adjacent two lower of the adjacent two vertebrae. Example C5-C6 vertebrae. Example C5-C6 and L5-S1. and L5-S1.

Cervical discs are usually Cervical discs are usually

constrained by the posterior constrained by the posterior longitudinal ligament to longitudinal ligament to herniate laterally toward the herniate laterally toward the nerve root, rather than nerve root, rather than centrally toward the spinal centrally toward the spinal cord.cord.

General DescriptionGeneral Description

Thoracic ,lumber and sacral Thoracic ,lumber and sacral nerve roots exit below the nerve roots exit below the correspondingly numbered correspondingly numbered vertebral bone.Cervical nerve vertebral bone.Cervical nerve roots,on the other hand, exit roots,on the other hand, exit above the correspondingly above the correspondingly numbered vertebral bone, numbered vertebral bone, except for C8 exit between C7 except for C8 exit between C7 and T1.and T1.

The lumosacral nerve roots exit The lumosacral nerve roots exit some distance above the some distance above the intervertebral discs.As they are intervertebral discs.As they are about to exit, the nerve roots about to exit, the nerve roots move into the lateral recess of move into the lateral recess of the spinal canal and at this point the spinal canal and at this point that they are closest to the that they are closest to the disc.disc.

General DescriptionGeneral Description Posterolateral disc Posterolateral disc

herniations in the herniations in the lumbosacral spine ,usually lumbosacral spine ,usually impinge on nerve roots on impinge on nerve roots on the lower vertebral bone.the lower vertebral bone.

Far lateral disc herniation Far lateral disc herniation result in impingement of result in impingement of the next higher nerve root.the next higher nerve root.

Central disc herniation ,at Central disc herniation ,at the level of cauda equina the level of cauda equina can impinge on nerve roots can impinge on nerve roots lower than the level of lower than the level of herniation.herniation.

Dermatomes and myotomes.Dermatomes and myotomes.Dermatomes:Dermatomes:

The sensory region of the skin The sensory region of the skin innervated by a nerve root.innervated by a nerve root.

Most of the head is supplied by Most of the head is supplied by C2 , via the greater and lesser C2 , via the greater and lesser occipital nerves.occipital nerves.

Common land marks ,T4, Common land marks ,T4, T10 ,T12.T10 ,T12.

There is a skip between C4 and There is a skip between C4 and T2, with C5 through T1 T2, with C5 through T1 represented on the upper represented on the upper extremities. extremities.

There is considerable overlap There is considerable overlap between adjacent dermatomes.between adjacent dermatomes.

Myotome:Myotome:The muscles innervated by a single The muscles innervated by a single

nerve root.nerve root.

Three Important Nerve Roots in the ArmThree Important Nerve Roots in the Arm

Three Important Nerve Roots in the LegThree Important Nerve Roots in the Leg

RadiculopathyRadiculopathy Pain and paresthesiasPain and paresthesias (burning, tingling pain that radiates or shoots down (burning, tingling pain that radiates or shoots down

the nerve root ),radiating in the the nerve root ),radiating in the distribution of a nerve rootdistribution of a nerve root, often , often associated with sensory loss and paraspinal muscle spasmassociated with sensory loss and paraspinal muscle spasm– Sensory loss (often vague or ill defined)Sensory loss (often vague or ill defined)– Weakness (often subjective, not present, or mild)Weakness (often subjective, not present, or mild)– Reflex loss (may be present or absent)Reflex loss (may be present or absent)– Chronic radiculopathy can result in atrophy and fasciculations.Chronic radiculopathy can result in atrophy and fasciculations.– T1 ---- Horner's syndrome .T1 ---- Horner's syndrome .

Herniated diskHerniated disk is by far the most common cause. is by far the most common cause.

InflammationInflammation is important as a pain mechanism: is important as a pain mechanism:– Phospholipase A and E, NO, TNFPhospholipase A and E, NO, TNF, other pro-inflammatory mediators , other pro-inflammatory mediators

are released are released by a herniated diskby a herniated disk– The dura surrounding the ventral and dorsal nerve root is bathed in this The dura surrounding the ventral and dorsal nerve root is bathed in this

exudateexudate– Inflammation or prior injuryInflammation or prior injury to nerve root is necessary to to nerve root is necessary to cause cause

compressioncompression to generate continued pain to generate continued pain

Diagnostic Test

ValsalvaValsalva– Cough, laughter, voluntary Cough, laughter, voluntary

contraction of abdominal wall contraction of abdominal wall muscles, when straining, make muscles, when straining, make radicular pain worseradicular pain worse

Stretching the involved nerve rootStretching the involved nerve root — —L5S1—sitting worsens, C5C6—abduct L5S1—sitting worsens, C5C6—abduct arm over head relieves.arm over head relieves.

Straight leg raising testStraight leg raising test.—L5S1 .—L5S1 worsens.(10-60).worsens.(10-60).

Crossed straight-leg raising testCrossed straight-leg raising test.. specificity over 90% for lumbosacral specificity over 90% for lumbosacral

nerve root compression.nerve root compression.

Percussion of the spinePercussion of the spine.. May indicate metastatic May indicate metastatic

disease ,epidural disease ,epidural abscess,osteomyelitis,or other abscess,osteomyelitis,or other disorders of the vertebral bones, disorders of the vertebral bones, although this sign is often absent in although this sign is often absent in these conditions.these conditions.

Imaging: ModalitiesImaging: Modalities X-rays:: most useful in most useful in traumatrauma to to exclude fractureexclude fracture, not sensitive for , not sensitive for

nerve root or spinal cord pathology.nerve root or spinal cord pathology.

CT: most useful study for most useful study for bony anatomy.bony anatomy.

MRI: most useful study for : most useful study for imaging disk, nerve root and spinal cord imaging disk, nerve root and spinal cord pathology.pathology.– Contrast is used if patient has had prior spine surgery in the affected area b/c Contrast is used if patient has had prior spine surgery in the affected area b/c

can light up scar tissue, or if tumor, infection, or other inflammatory etiology is can light up scar tissue, or if tumor, infection, or other inflammatory etiology is suspected.suspected.

CT myelogramCT myelogram, CT/w dye injected into spine: in patients who cannot , CT/w dye injected into spine: in patients who cannot obtain MRI, often the best study for imaging the nerve roots of a selected obtain MRI, often the best study for imaging the nerve roots of a selected area.area.

Other diagnostic modalitesOther diagnostic modalites::EMG and NCSEMG and NCS

In patients with acute radiculopathy, EMG studies will not be of value until at least 3 weeks .

EMG studies can help the decision making process by identifying the distribution and extent of spinal nerve root damage, the degree of acute axon loss, and the likelihood of conduction block.

Treatment of Radiculopathy:Treatment of Radiculopathy: Natural history of lumbosacral and cervical Natural history of lumbosacral and cervical

radiculopathy:radiculopathy:

– Up to Up to 75% spontaneously75% spontaneously improve improve– Length of time required for improvement may Length of time required for improvement may

be several weeks or up to years!be several weeks or up to years!

If there is a If there is a progressive neurologic deficitprogressive neurologic deficit or or intractable painintractable pain, surgical referral is , surgical referral is appropriate ,otherwise, most patients can appropriate ,otherwise, most patients can avoid surgeryavoid surgery

Empiric Treatment of Empiric Treatment of Radiculopathy:Radiculopathy:

Medications:Medications:– Pain control with NSAIDS and narcotic medications as Pain control with NSAIDS and narcotic medications as

necessarynecessary– Short course of corticosteroids in selected patients; Short course of corticosteroids in selected patients;

justification is to decrease inflammation around the justification is to decrease inflammation around the nerve root.nerve root.

Gentle physical therapy (mobilization and stretching)Gentle physical therapy (mobilization and stretching) Bed restBed rest heating pads, ultrasound, gentle massageheating pads, ultrasound, gentle massage Traction for the cervical spineTraction for the cervical spine Epidural steroid injections for the LS spineEpidural steroid injections for the LS spine

– Risks are higher in cervical spineRisks are higher in cervical spine Transforaminal steroid injections for the LS spineTransforaminal steroid injections for the LS spine

Cauda equina and conus Cauda equina and conus medullaris Syndromes:medullaris Syndromes:

Large midline disk herniation can cause Large midline disk herniation can cause symptoms in both legs in the distribution of symptoms in both legs in the distribution of multiple nerve roots, bilateral symptoms multiple nerve roots, bilateral symptoms with large full bladderwith large full bladder

– Cauda equina syndrome: Cauda equina syndrome: multiple nerve roots multiple nerve roots bilaterallybilaterally are are

affected below the end of the spinal affected below the end of the spinal cord at L1-2cord at L1-2

– Conus medullaris syndrome: Conus medullaris syndrome: the end of the spinal cord from about the end of the spinal cord from about

T11-L1T11-L1

Cauda equina and conus Cauda equina and conus medullaris Syndromes:medullaris Syndromes:

Both are potentially surgical emergencies Both are potentially surgical emergencies depending on the causedepending on the cause

Warning signs that one of these may be Warning signs that one of these may be present are: present are: – Rapidly progressive bilateral lower extremity Rapidly progressive bilateral lower extremity

weaknessweakness– Saddle anesthesiaSaddle anesthesia– Loss of ability to urinate voluntarily with a large Loss of ability to urinate voluntarily with a large

bladder and overflow incontinencebladder and overflow incontinence– Loss of rectal toneLoss of rectal tone

Cauda Equina and conus Cauda Equina and conus medullarismedullaris

Differentiating the two is difficult, and they may Differentiating the two is difficult, and they may coexist:coexist:– Cauda equina: More pain, asymmetric at onset, bladder Cauda equina: More pain, asymmetric at onset, bladder

dysfunction not initially as severe. more of lower motor dysfunction not initially as severe. more of lower motor neuron signsneuron signs

– Conus medullaris: Often little pain, symmetric at onset, Conus medullaris: Often little pain, symmetric at onset, severe bladder dysfunction. more of upper motor neuron severe bladder dysfunction. more of upper motor neuron signssigns

Key points: Key points: – Emergent imaging with MRI is essential Emergent imaging with MRI is essential – Make sure to image high enough to see the full conus! To Make sure to image high enough to see the full conus! To

at least T10at least T10

References :References : Main reference :

Neuroanatomy through clinical cases.Neuroanatomy through clinical cases.HAL BLUMENFELD, M.D., PhD.HAL BLUMENFELD, M.D., PhD.

Other references:Cervical and low back pain and radiculopathy.Cervical and low back pain and radiculopathy.Jenice Robinson, MD Assistant Professor of Neurology Penn State College of Medicine NBS725 Jenice Robinson, MD Assistant Professor of Neurology Penn State College of Medicine NBS725

January 12, 2009.January 12, 2009.

DISEASES OF THE NERVE ROOTS Kerry Levin2008, American Academy of Neurology

SPINAL CORD ANATOMY, LOCALIZATION, AND OVERVIEW OF SPINAL CORD SYNDROMES

Gregory Gruener, Jose´ Biller2008, American Academy of Neurology

Human Anatomy, First EditionMcKinley & O'Loughlin

Lumbar Disc Herniation and RadiculopathyLumbar Disc Herniation and RadiculopathyKS HospitalKS Hospital Spine Center Spine Center

Spinal Nerve RootsSpinal Nerve Roots

Abdullah Al-Salti R2Abdullah Al-Salti R224 February 201024 February 2010