Cervical Myelopathy

Definition

 

Spinal cord dysfunction
- extrinsic compression of the cord or its vascular supply
- caused by degenerative disease of spine

 

Epidemiology

 

Most common spinal cord dysfunction in patients > 55 years old
 

C5/6 commonest level

Pathophysiology

 

Congenital

- congenital / developmental stenosis
- decreased space available for cord
- average mid cervical spine is 17 – 18 mm

 

Acquired

1. HNP

2. Osteophytes from facet and uncovertebral joints
3. Ligamentum Flavum

4. Instability

5. Kyphosis
- stretches spinal cord over posterior vertebral bodies and discs
- dictates an anterior approach

6. Ossification of PLL
- more common in certain Asian populations i.e. Japanese

 

DDx
 

Need to exclude other causes of spinal cord dysfunction

 

Supratentorial
- CVA / AVM / Tumour / Hydrocephalus

- Metabolic or alcoholic encephalopathy

 

Spinal
- demyelinating disease / MS / MND
- syringomyelia / Tabes dorsalis

- myopathy / peripheral neuropathy

 

History

 

Neck pain

 

Parasthesia
- global, non dermatomal distribution over upper extremities

 

Difficulty walking / unsteadiness on feet

 

UL > LL

- have central cord like presentation
- distal worst than central

 

UL
- pain , numbness and weakness
- clumsiness of hands common
- difficulty with fine motor function
- may also have radicular symptoms

 

Bladder dysfunction uncommonly occurs

 

May present acutely with central cord syndrome

 

Examination

 

UMN in extremities below lesion

LMN signs at level of lesion

 

Ataxia

 

Wide based gait

Unable to heel toe

 

Poor proprioception
 

1.  Finger escape sign
- deficient adduction or extension of ulnar digits of affected hand

 

2.  Romberg Positive

 

Hyper-reflexia

 

1.  Hoffman Reflex
- flexion of ipsilateral IPJ of index and thumb when long finger DIPJ flexed

- extension of neck increases sensitivity

 

2.  Inverted Brachioradial Reflex

- spontaneous flexion of digits when BR reflex elicited
- indicates cord compression at C5 and C6 / commonest levels

 

3.  Babinski Reflex

X-ray

 

Narrowed joint space
- C5/6 commonest level followed by C6/7

 

Osteophytic lipping
- foraminal and uncovertebral osteophytes seen

 

Alignment
- lordosis v kyphosis
 

 

Ossification PLL

 

 

Flexion / Extension views show instability
- > 3 ^o
- > 11 mm

 

Pavlovs Ratio
- AP diameter of spinal canal divided by the AP diameter of body at same level
- indicator of developmental stenosis
- should be 1.0

- < 0.8 is narrowed and stenotic

 

AP diameter / SAC
- normal (17mm)
- relative (13mm)
- absolute stenosis (10mm)

 

NB: X-ray estimates of space available for cord

- do not take into account ST i.e. discs and ligamentum flavum

 

CT

 

Helps distinguish disc from osteophytes

- soft v hard disc

 

OPLL

 

 

MRI

 

Disc herniation

- high incidence of asymptomatic findings
- 19% of asymptomatic patients have abnormality on MRI

 

 

Cord changes
- cord oedema with signal change seen

 

 

AP diameter thecal sac < 10 mm

 

Compression Ratio
- banana cord
- divide the smallest AP diameter by largest transverse diameter at same level of spinal cord
- ratio of < 0.4 after decompression particularly with myelopathy > 6 months has poor prognosis

 

 

Cross sectional area of spinal cord
- < 30 mm² poor prognosis

 

NHx

 

Natural history suggests that > 50% of patients become worse if not treated
- some stable
- most slowly progressive
- < 5% acute deterioration

 

Management

 

Non operative

 

Cervical collar
NSAIDS
Physiotherapy with isometric strengthening
Ice , heat and massage

Follow up every 6-12 weeks initially followed by yearly if no progression

Traction and manipulation contraindicated

Must counsel them to the risks of trauma

 

Operative

 

Absolute Indications

 

1. Progressive neurological deficit
2. Failure of symptoms to improve with 6 months of non operative treatment
- base on severity of clinical neurological fingings

 

Relative indications

 

1. Compression ratio < 0.4
2. Transverse spinal cord diameter of < 40 mm2
3. Increased signal intensity of cord on T2 of MRI
4. Acute central cord syndrome
- initially collar and methylprednisolone
- no operation if near full recovery
- decompress if residual neurological deficit

 

Order

 

The patient with cervical and lumbar stenosis

- should have the cervical spine decompressed first

- risk of intubation damage to cervical spine
- reduces need for lumbar surgery
- leg symptoms may improve after the cervical decompression

 

Prognosis

 

Surgery can be expected to halt progression

- may improve motor, sensory and gait disturbance

 

The best spinal cord recovery seen in those treated
- decompression within 6 - 12 months
- early, mild myelopathic signs
- transverse area of cord greater than 40 mm² postoperatively
- age < 60

 

Preoperative Considerations

 

NSAIDS ceased 2 weeks prior to surgery

 

Positioning should avoid hyperextension of the cervical spine

- may need awake fibreoptic intubation

 

Options

 

1.  Laminectomy & fusion

2.  Laminoplasty

2.  ACDF

3.  Corpectomy

 

1. Laminectomy & Fusion

 

 

Concept

 

Any posterior decompression procedure is an indirect technique

- requires posterior shifting of the cord in the thecal sac

- to diminish the effect of the anterior compression

 

Indications

Lordotic cervical spine / no kyphotic deformity

Ossification of PLL

- dura may be adhered

- high risk of irreparable dural tears with anterior approach

 

Indications for fusion
 

Instability

 

Technique

 

Positioning for the posterior approach
- prone
- Mayfield head tongs in neutral

- protect eyes / elbows (ulna nerve) / knees (CPN)
- pneumatic compression stockings
- IDC
- infiltration of skin with adrenaline solution

 

Decompression

- wide laminectomy +/- foraminotomy

 

Instrumentation
- avoids progressive kyphotic deformity
- lateral mass screws

 

 

Complications

 

Postoperative instability / kyphosis
- > 50% facet resection = instability
- avoid by fusion or laminoplasty

 

2.  Laminoplasty

 

Concept

- divide lamina unilaterally

- elevate to decompress

- insert device to keep lamina elevated

 

Advantage

- maintains stability

- no need to insert pedicle screws

 

Indication

- no kyphotic deformity

 

3. ACDF / Corpectomy and Arthrodesis

 

 

Indication

- anterior cord compression

- pathology primarily at disc level

- kyphotic deformity

 

Advantages
- removes entire disc

- can maintain / restore lordosis

- restores foramina / decompresses nerve root

 

Disadvantages
- difficulty decompressing the nerve roots in foramen from front
- difficult access to the posterior osteophytes

 

Technique

 

Smith - Robinson approach

 

Positioning
- supine with interscapular roll
- head turned slightly to right for left sided approach

 

Disc removal in full
- MRI reviewed carefully to exclude free disc lying behind the PLL
- resect the disc until the longitudinal fibres of PLL seen

- inspect carefully for defect
- if no defect on MRI findings then should not routinely remove the PLL

 

Insertion cage 

- contains autograft / allograft / BMP & collagen
- sized first, check on x-ray
- insert cage, ensuring not too posterior
- aiming to decompress foramina

 

Anterior plate for stability

 

4.  Corpectomy and strut Graft

 

 

 

Indication

- multilevel disease

- soft and hard disc causing compression

- kyphotic deformity

 

Technique

 

Anterior approach
- decompression of disc above and below

- resection of vertebral body with burr
- leave lateral walls to protect vertebral artery
- typical midline channel is 16 – 18 mm

 

Bone Grafting Technique
- single level, iliac crest
- multiple level, fibular strut
- autograft superior to allograft

 

Instrumentation
- maintains alignment / improves graft stability
 

Post op
- usually require HTB

 

Complications

 

1. Transient sore throat or difficulty swallowing

- most common complication

- superior laryngeal nerve

 

2. Recurrent Laryngeal Nerve paralysis
- more common in right sided approach
- post operative hoarseness

 

3. Respiratory compromise
- drains
- strict monitoring

- emergency release of wound stitches if haematoma

 

4. Neurological injury 1 – 2%

 

5. Injury vertebral artery

 

6. Dural tears
- more common if OPLL
- fibrin glue, fascial patch

 

7. Graft related
- dislodgement
- fracture
- severe settling
- pseudoarthrosis

Cervical Radiculopathy

Definition

 

Clinical diagnosis

- based on a sclerotomal distribution of motor &/or sensory symptoms or signs

 

Caused by impingement of exiting nerve roots

- HNP

- zygo-apophyseal / facet joint hypertrophy

- neuro-central joint hypertrophy

 

May be acute or chronic

 

Epidemiology

 

M>F

 

Peak age 50-54

 

C7 > C6

 

Natural History

 

Mayo Clinic Natural History Radiculopathy

- 50% of population at some stage

- ~50% recurrent

- 90% asymptomatic at 5 years

 

Anatomy

 

Each subaxial C-spine motion segment has 5 articulations

 

A. Intervertebral disc

 

B.  2 neurocentral / uncovertebral joints

- along posterolateral vertebral body / Joint of Luschka

- lie between disc & nerve root

- each body has upturned postero-lateral uncinate process

- pedicle is attached below uncinate process

 

C.  2 facet joints

- angulated 30-50° to transverse plane

 

Intervertebral foramina boundaries

 

A. Anterior

- both vertebral bodies, uncinate process & disc

 

B.  Posterior

- facet joints

 

C.  Above & below

- pedicles

 

Foramina are 45° to sagittal plane

 

Transverse process

 

3 elements

1. Embryological TP to posterior tubercle

2. Embryological rib to anterior tubercle

3. Tubercles joined by intertubercular lamella

 

Foramen transversarium in middle with vertebral artery

Dorsal root ganglion and ventral ramus spinal nerve on intertubercular lamella

 

Tubercles

 

Posterior tubercle

- Scalenus medius

 

Anterior tubercle

- Scalenus anterior, longus coli & capitus

- progressively enlarge from C3 down to C6

- C6 Chassaignacs tubercle

 

Cervical Nerve Roots

 

Each cervical root exits above the pedicle for which it is named except C8

- C5/6 – C6

- C6/7 – C7

- C7/T1 – C8

 

Pathophysiology Nerve root compression

 

1.  HNP

- in contrast to lumbar spine

- both posterolateral and central HNP compress exiting nerve root

- inflammatory and ischaemic components

 

A. Central - myelopathy

B. Posterolateral - mainly motor weakness

C. Intraforaminal - most common / often dermatomal distribution

 

 

2.  Spondylosis / Disc degeneration

- loss of height / annular bulging

- foraminal compression

 

3.  Bony 

 

A.  Uncovertebral osteophytes / hard discs

- compress nerve root anteriorly

 

B.  Superior articular facet osteophyte

- extend from ventral surface to compress the neural foramen

- are less common

 

Clinical

 

Pain / parasthesia

- often don’t follow dermatomal distribution

 

Weakness

- 60-70% motor deficiency

 

Spurling maneuver

- hyperextension with tilt toward affected side 

- stimulates radiculopathy symptoms

 

Nerve root signs (C6 and C7 most common)

 

C2 Posterior occipital headaches

C3 Occipital headache

C4 Neck and trapezial pain +/- shoulder / scapula pain

C5 Pain lateral upper arm (epaulet) / deltoid weakness / biceps jerk decreased

C6 Radial forearm and hand pain / weak biceps and wrist extension / BR reflex decreased

C7 MF pain / weak triceps / absent triceps jerk

C8 Pain ring and little fingers / weak finger flexors

T1 Ulna forearm pain / weak hand intrinsics

 

DDx Myopathy

 

Entrapment syndromes (ulna / median nerves)

Thoracic outlet syndrome

RC disease

 

X-ray

 

Demonstrate loss of disc height and degeneration

 

MRI

 

Note

- 19% of asymptomatic patients will have evidence of nerve root compression

- difficult to distinguish between hard and soft discs

 

CT

 

Adds complementary information to MRI in C spine

 

Demonstrates the posterolateral impingement is from “hard” disc

- i.e. uncovertebral spur 

 

Cervical nerve root injections

 

Confirm diagnosis

- should get some temporary symptomatic relief

 

EMG / NCS

 

Indication

- concern re peripheral nerve entrapment

 

SNAP

- are usually normal because lesion proximal to DRG

 

CMAP

- amplitude decreased proportional to muscle atrophy

 

Nerve conduction velocity

- not abnormal unless severe demyelination of axons

 

EMG

- best for differentiating peripheral nerve root compression from central

- fibrillations

 

Management

 

Non operative

 

Options

 

Rest

Pharmaceutical / NSAIDS

Physio

- hot / cold

- electrical stimulation

- ROM / stretching

- isometric strengthening exercises 

Cervical traction

Collar

HCLA / nerve root injections

 

Results

 

Lellad et al Ann Phys Rehabil Med 2009

- RCT demonstrating benefit of reducing symptoms with cervical traction

 

 

Kuijper et al BMJ 2009

- RCT demonstrating benefit of wearing semi-hard collar for 3 weeks 

 

Operative

 

Indications

- severe pain

- severe neurological impairment

- failure non operative treatment

 

Options

 

ACDF

Disc replacement

Corpectomy

Laminoforaminotomy

 

1. ACDF

 

 

Definition

 

Anterior Cervical Discectomy and Fusion

 

Concept

- anterior approach

- interbody fusion

- iliac crest bone graft / synthetic bone graft / allograft / cage

- anterior plate / eliminates need for brace

 

Advantage

- deal with HNP and uncovertebral osteophytes

- opens up the neuroforamina and decompresses the nerve

- fusion relieves pain of spondylosis

- anterior approach dissects little muscle and has little pain

- scar very cosmetically acceptable

 

Technique

 

Smith & Robinson / anterior approach

- divide platysma and deep cervical fascia

- SCM laterally

- divide pretracheal fascia / carotid sheath laterally

- divide prevertebral fascia in midline, separate longus colli

 

Discectomy

- decorticate end plates

- excision of osteophytes controversial

- generally only if causing compression

- otherwise will absorb with stability

 

Complications

- pseudarthrosis

- graft / cage displacement posteriorly

- wrong level

- insufficient decompression

- neurological injury (quadriplegia /  nerve root / RLN / Superior Laryngeal Nerve)

- injury to other structures (carotid artery / oesophagus)

- degeneration at second level

 

 

 

 

2. Disc replacement

 

Technique

- as above

- insert disc replacement

- no anterior plate

 

Advantage

- maintain some motion

- preserve other disc segments

 

Results

 

Murrey et al Spine 2009

- RCT of ACDF v disc replacement

- disc replacement maintained 4^o of motion

- significant reduced reoperation rate in disc replacement (1 v 8%)

 

3. Corpectomy

 

Indication

- multilevel hard and soft compression

- can remove body with disc above and below

- decompress 2 levels

 

 

 

4. Laminoforaminotomy

 

Technique

- posterior approach

- deroofing of foramina

 

Results

 

Herkowitz et al Spine 1990

- compared ACDF with posterior laminotomy / foraminotomy

- patients with both central and posterolateral discs

- combination of radiculopathy and myelopathy symptoms

- 4 year followup

- 95% vs 75% G/E

 

Johnson et al Spine 2000

- prospective study of patients with posterolateral disc and radiculopathy

- patients had no neck pain

- removal of HNP + uncovertebral osteophytes

- 91% improved or resolved

- 9% revision (ACDF / repeat posterior foraminotomy)

 

 

 

 

Cervical Spondylosis

Definitions

 

Cervical spondylosis

- chronic disc degeneration & associated facet arthropathy

 

Cervical myelopathy

- spinal cord dysfunction

- secondary to extrinsic compression of cord or its vascular supply

 

Cervical radiculopathy

- sclerotomal distribution of motor &/or sensory symptoms or signs

- due to compression of nerve root

 

Epidemiology

 

Usually begins at age 40-50

 

M>F

 

Most common at C5/6 > C6/7 > C4/5

 

Pathology

 

Spondylosis

 

Degenerative changes at disc / facet joints / uncovertebral joints

 

Clinical Features

 

Neck pain / headaches / local tenderness

 

Reduced ROM

 

X-ray

 

Typical changes of spondylosis

- disc space narrowing

- osteophyte formation

- degenerative facet & uncovertebral joints

 

May be present in asymptomatic individuals

 

 

CT scan

 

Degenerative changes

 

 

MRI

 

Degenerative disc changes

- dessicated (loss of fluid), narrowed, end plate changes

 

Space available for cord

 

Neural compression

- intrinsic cord changes

- cord compression / ratio / cross sectional area

 

 

Management

 

Non-operative

 

Education & Reassurance

- analgesics

- local modalities

- exercise programme

- traction

 

Operative

 

Indications

 

Spondylosis

- failure non operative treatment

- disease isolated to 1 or 2 levels

 

Options

 

Posterior Instrumented Fusion

 

 

ACDF

 

 

Advantage

- restores disc height and aligment

- decompresses foramina

 

Options

- autograft

- allograft

- cage

 

Jacobs et al Cochrane Database Review 2011

- autograft superior to discectomy alone

- autograft superior to cage in fusion rate but with higher complications

 

Disc Replacement

 

Advantage

- elevate / decompress foramin

- maintain motion / decrease degeneration at subsequent levels

 

Burkus et al J Neurosurg Spine 2010

- prospective multicentred RCT 541 patients with single level disc degeneration

- disc replacement v ACDF

- improved outcome scores and neurological outcome in disc replacement

- no difference in rates of subsequent level surgery

Technique ACDF

Anterior Cervical Discectomy and Fusion

 

 

Position

 

Place the patient in the supine position

- small roll placed under the shoulder blades to drop the shoulders from the field

- exposes the anterior neck

- strap the shoulders at the side with minimal traction 

- allows visualization of the lower cervical spine on lateral radiographs

- apply skull traction with Gardner-Wells tongs

- keep head rotation to a minimum because deep dissection will depend on identifying the vertebrae midline

- prevents inadvertent injury to adjacent structures

- reverse Trendelenburg position facilitates venous drainage and results in less bleeding during surgery

 

Dissection

 

Anatomic landmarks for incision 

- hyoid bone overlying C3

- thyroid cartilage overlying the C4/5 interspace

- cricoid cartilage overlying the C6 level

 

Use transverse incision for exposure in most cases

- more cosmetic

- from the midline to the anterior border of SCM in Langer's lines

- divide the deep cervical fascia and platysma muscle exposing the middle layer of the cervical fascia

- bluntly dissect the pretracheal fascia and palpate the carotid pulse

 

When three or more levels are approached, use a longitudinal incision

 

Dissection through the pretracheal fascia places several structures at risk

- superior and inferior thyroid arteries extend through the pretracheal fascia from the carotid artery to the midline

- travel at the C3/4 and C6/7 levels, respectively

- intervening area provides a relatively avascular plane for dissection

 

Recurrent laryngeal nerves

- right recurrent laryngeal nerve ascends in the neck after passing around the subclavian vessels

- courses medially and cranially at the C6–C7 level, often along with the inferior thyroid artery

- left recurrent laryngeal nerve ascends after curving around the aortic arch along the tracheoesophageal groove

- more midline and protected position

- left-sided procedure may be safer, especially when lower cervical segments are approached

- the thoracic duct is often visible on the left at the C7–T1 level and must be protected

 

Retract the sternocleidomastoid muscle and the carotid sheath medially

- contents (common carotid artery, internal jugular vein, and vagus nerve)

 

Retract the midline structures, including the trachea, esophagus, and thyroid gland medially

- complete blunt dissection through the deeper levels to the prevertebral fascia and vertebral bodies

 

Once the midline is identified, incise the prevertebral fascia

- elevate the medial edges of the longus colli muscles

- place blunt self-retaining retractors under the leading edges of the muscle

- Tramline retractor is used (Medial Lateral)

- take care to avoid dissecting along the longus colli muscle because of injury to the cervical sympathetic plexus

- screws in vertebral bodies for vertebral distraction

 

Discectomy

 

Identify

- vertebral bodies by their concave appearance 

- the discs by their more convex contour

 

Localize the disc space with a radiopaque marker and lateral radiograph

 

Remove disc

- incise the disc with an annulotomy blade

- cut lateral to medial away from the vertebral artery

- remove the disc contents and endplate cartilage to the PLL

- use thorough evaluative preoperative imaging to determine the presence of a sequestered disc behind the PLL

- palpate the PLL for the presence of a rent that may also indicate a sequestered fragment

- in the event that a rent is noted, or if an expected disc fragment is not identified, remove the PLL with Kerrison rongeurs

- beware of routine removal of the PLL, because reports of postoperative epidural hematoma have been associated with this technique

 

Removal of endplate and uncovertebral osteophytes is controversial

- disc space distraction reduces ligamentum flavum buckling and increases neuroforaminal area

- it is believed that fusion will arrest spur progression, and stability may allow for resorption over time

- however, this is not a consistent phenomenon

- the location and size of the offending spur must be carefully considered when performing decompression

- exposure of the uncinate processes is critical to safely remove osteophytes

- utilize a high-speed burr to excise the spur from medial to lateral

 

Foraminotomy

- judge the adequacy of foraminotomy

- ability to place the tip of a curret anterior to the exiting nerve root without significant resistance