Degenerative cervical Myelopathy (DCM)

Definition

Cervical cord compression causing neck pain and upper motor neurons signs

Numbers

Most patients are first diagnosed in their 50s

DCM is uncommon before the age of 40

Clinical examination

History

Manual dexterity (mobile, tv control, typing)
Balance-Gait
Onset of symptoms can be insidious
Patients with myelopathy tend to have symmetrical involvement of motor and sensory tracts within the spinal cord.
unsteadiness of gait, and recurrent falls.
Bilateral weakness below the affected level (paraparesis or quadriparesis),
Paraesthesia, numbness,
Tingling
Sensory loss with a discrete sensory level
Poor dexterity

Deterioration in hand control especially with fine tasks → progressing to increased clumsiness

Examination

Tandem gait
Increased tone
Reflexes

Brisk and pathological reflexes (Hoffman’s and Babinski sign)
inverted supinator
Clonus

May be symptoms of difficulty with sphincter control.
Seichi 2006 - best to use sensory examination to localize

Classification

Tetreault 2017 mJOA

Severity	mJOA
Mild	15-17
Moderate	12-14
Severe	0-11

Ranawat classification of myelopathy

Class	Description
I	no neural deficit
II	subjective weakness + hyperreflexia + dysesthesia
III	objective weakness + long tract signs Ill A=ambulatory Ill B=quadriparetic & non ambulatory

Nurick Grade For Myelopathy

Grade	Signs and Symptoms
0	Root symptoms only or normal
1	Signs of cord compression; normal gait
2	Gait difficulties but fully employed
3	Gait difficulties prevent employment; walks unassisted
4	Unable to walk without assistance
5	Wheelchair or bed-bound

Pedro 2024 - AO Spine Clinical Practice Recommendations

This might be a better classification than mJOA

Machine learning-based cluster analysis identifies 4 unique phenotypes of patients with degenerative cervical myelopathy

Severe multimodal impairment:

Patients exhibited dysfunction across all symptom domains, with the highest neck pain scores, NDI, and frailty levels.
Despite significant baseline disability, they showed the most substantial improvement in mJOA scores after 1 year, but had the worst quality of life outcomes.

Minimal impairment:

Patients had low level of impairment across all symptom domains and the lowest score for neck pain.
They achieved the highest physical quality of life scores after 1 year, but had the lowest mental quality of life scores.

Motor dominant impairment:

Patients experienced significant motor and sensory dysfunction with minimal/no pain.
They showed modest improvement in both physical and mental quality of life 1 year post-surgery

Pain dominant impairment:

Patients had high neck pain scores but relatively better motor and sensory function than those with severe multimodal impairment.
They achieved the highest mental quality of life scores 1 year after surgery.

Mechanism

Direct compression

Spondylotic cervical myelopathy:

Flexion may be a larger contributor to the etiology as cord impingement is exacerbated.

Deformity

Progressive cervical kyphosis leads to myelopath

Kyphosis forces the spinal cord against vertebral bodies →

Increasing longitudinal cord tension on the cord (since cord is tethered to the dentate ligaments and the cervical nerve roots) → Anterior cord pathology → Neuronal loss + demyelination
Flattening small blood vessels → Reduced blood supply to the cord → Neuronal loss + demyelination

Zhang 2011

cervical cord is significantly longer in flexion than in the neutral or extension positions.
cord available space: greatest > neutral position > flexion > extension

cord impingement more likely on extension than flexion

Primary cervical malalignment:

in which flexion/kyphosis is the predominant position of the spine → myelopathy due to cord lengthening, flattening, and vascular compromise.

The posterior neural arch is responsible for the majority of the load transmission through the cervical spine:

Naturally the C spine is lordotic → allows posterior neural arch to distribute most of the load posteriorly.
Removal of C spine arch → loss of stability (might not be destabilized initially) → Over time, the added there is a shift in load bearing from the posterior column to the anterior column → causes the discs and vertebral bodies become wedged with greater sagittal malalignment during the course of months to years → cervical kyphosis → draping of the cord → myelopathy

Natural hx

The majority of individuals with DCM experience a progressive, stepwise deterioration in their symptoms and functional decline

Without treatment, this may progress to severe disability and complete paralysis

Rate of this progression is highly variable:

some people with DCM can have a long period of neurological stability without progression and more abrupt deterioration can occur following minor trauma.

Asymptomatic spinal cord compression

Population prevalence of asymptomatic spinal cord compression on MRI is 24.6%
A prevalence which increases with age, but no symptoms of myelopathy
A risk factor for acute spinal cord injury.
Bednarik 2008

In series providing longitudinal follow up of asymptomatic spinal cord compression,
8% developed DCM after 12 months
22% developed DCM within 44 months.

Imaging

Xray

<13mm canal with

Grading

Aebli 2013: Torg-Pavlov ratio cutoff value of 0.7 inc. risk of SCI after minor neck trauma.

Kang et al classification

Grade 0: No stenosis (no narrowing of the spinal canal).

Grade 1 (Mild stenosis): Narrowing of more than 50% of the subarachnoid space without signs of spinal cord deformity.

Grade 2 (Moderate stenosis): Spinal canal stenosis with visible deformation (compression) of the spinal cord, but without T2 hyperintensity (no spinal cord signal change).

Grade 3 (Severe stenosis): Spinal cord compression with a hyperintense signal in T2-weighted MRI at the level of compression, indicating myelopathy.

Cord signal change

Position of cord signal change

Disc level

common location

Vertebral body level

less common
can sugget there is dynamic instability

check with global (C2-C7 cobb angle) and local (1 segment) flexion and extension xray
Mech: as the cord that has signal change moves up to the disc level and causes compression

Nouri, et al. 2017

T1WI hypo-intense signal change may be an important finding, associated with higher frequency of myelopathic features and decreased recovery potential.
Multi-level T2WI hyperintense signal changes are also associated with decreased recovery potential.
Single-level T2WI hyperintense changes were only weakly correlated with pre-operative clinical signs, symptoms, and post-operative prognosis.

DTI studies - in research still

Quantify microstructural damage
Column specific degeneration
FA reduction correlates with myelopathy severity

Changes more profound with severity – suggests progressive changes with compression overtime
Jones 2013

FA demonstrated a strong correlation with baseline mJOA (r = 0.62, P < .01) and Nurick (r = −0.46, P = .01) scores.
After surgery, recovery of function demonstrated by improvement in NDI score was associated with higher FA values on preoperative DTI

Predict postoperative improvement (FA >0.55)

Flexion and extension xrays

To look for spinal instability

Standing 3-foot scoliosis X-rays

Indicated:

When significant deformity is clinically or radiographically suspected, regional cervical and relative global spinal alignment should be evaluated preoperatively

Management

Needs to take into account

Location of compression: Ventral vs dorsal

Sagittal alignment

Focal versus diffuse disease

Presence or absence of radiculopathy

Significant axial cervical pain

Comorbidities

Surgical familiarity with an approach

Conservative

Indicated for

Mild DCM

Nouri et al 2022

In patients with symptomatic DCM undergoing non-operative treatment, 20-62% will experience neurological deterioration within 3-6 years.

Badhiwala, et al. 2019 - AO Spine Clinical Practice Recommendations

Surgery should be offered as an option in cases of mild DCM.

The potential improvement in function and quality of life following surgery likely outweighs associated complications, based on moderate quality evidence.
Surgery for mild DCM has been associated with an incremental lifetime increase of 1.26 quality-adjusted life years (QALY) compared to observation.
Due to the lack of comparative evidence against non-surgical management, a strong recommendation in favour of surgery cannot be made.

Structured follow-up remains a viable option in clinically stable patients.

Asymptomatic spinal cord compression

Fehlings 2017 Asymptomatic cord compression but with symptomatic and/or electrophysiological evidence of radiculopathy

are at a higher risk of myelopathy development
Need closer monitoring and if develop signs of myelopathy should be for surgery

patients who are poor candidates for surgery

Options

Bracing

hard collar in slight flexion

Analgesia

NSAIDs
Gabapentin

Physio

Preoperative physiotherapy should only be advised by specialist spinal services
neck strengthening, balance, and gait training

Bed rest
Avoidance of high-risk activities and environments

DO NOT perform neck manipulation, such as cervical traction, in pre-operative DCM due to the risk of causing further damage to the spinal cord

Close monitoring

Evidence

Kadanka 2000: RCT Surgery vs conservative n68 for Moderate and Mild DCM

Bottom line: No difference in mJOA score in surgery vs conservative tx

Kadanka 2003: same RCT as above but 3 years outcome

improved nonoperative outcomes associated with patients with larger transverse area of the spinal cord (>70mm2)
Older age
Normal central motor conduction time (MEPs via Transcranial magnetic stimulator)

Martin 2021:

Neurological deterioration over 2.5 years

57% of newly diagnosed DCM (mild/moderate/severe) patients
73% of recurrent DCM

Some studies have shown improvement with immobilization in patients with very mild symptoms

Surgical (surgical decompression, restoration of lordosis, stabilization)

Indication

Mild DCM with one point drop in mJOA scale
Moderate and severe DCM
Lordotic, neutral or kyphotic alignment

Aims

Prevent worsening of symptoms

The timing of surgery

More controversial in patients with mild features of myelopathy or asymptomatic cord compression.
Is advocated in most patients with cervical myelopathy because the majority (80%) deteriorate over time

Spontaneous regression being uncommon

Patients should be counselled with regard to the risk of cord injury secondary to degenerative disc disease in the context of trauma
Earlier intervention in symptomatic cervical myelopathy is associated with improved outcomes.
Chronic neurological deficit is unlikely to improve

Surgical decision making tree

Farrokhi et al 2016

Pt with cervical lordosis + <3 levels of anterior disease

ACDF or ACDR

Pt with cervical lordosis + >3 levels of posterior disease

Laminoplasty

Pt with loss of lordosis + <3 levels ant/post disease

ACDF + plate

Mild cervical kyphosis (kyphotic angle ≤10°)

ACDF + plate

Instability + >3 involved levels

Posterior decompression and fusion

Young patients who have a stable cervical spine

Laminoplasty

Old patients with ankylosed spine that is stable

Laminectomy

Severe kyphosis, cervical traction is recommended.

If kyphosis is reducible,

posterior decompression and fusion

If kyphosis is irreducible kyphosis,

if the number of involved levels is less than 2

ACDF

if it is more than 2 levels,

anterior cervical corpectomy and fusion

MRI: Subarachnoid space patency

If Patent

only posterior fusion

If not patient

posterior decompression with posterior fusion

Theodore 2001 Algorithm for treatment options for patients with myelopathy.

a:If no postoperative improvement, reimage and consider posterior decompression.

b: If no postoperative improvement, reimage and consider anterior decompression.

c: In young patients, consider adjunct fusion.

d: Discectomy above, below, or both as needed.

Lee 2024:

Lee 2024.pdf

2.2 MB

K-line Classification

K-line (+) group:

OPLL does not exceed the K-line and remains within the ventral area
meaning there is space between the K-line and the OPLL.

K-line (-) group:

OPLL exceeds the K-line and has grown beyond it.
This can occur with a large OPLL size or even an intermediate OPLL size if the cervical spine alignment is kyphotic

Deformity and myelopathy

When performing decompressive surgery for CSM, consideration should be given to correction of cervical kyphosis and cervical sagittal imbalance (C2-C7 SVA) when present.

Surgical management of cervical myelopathy should consider the sagittal alignment, as decompression alone might not suffice if cord tension from kyphosis is not reduced.

Postlaminectomy kyphosis is a common etiology of cervical spinal deformity, often worsening myelopathy.
The preoperative T1 slope is crucial, as a higher slope increases the likelihood of postoperative kyphotic changes after laminoplasty.

Treatment procedures include

Evidence: Anterior vs posterior approaches

Ghogawala 2021 RCT

In DCM affecting two or more levels
At 1 year No difference between anterior and posterior surgery in functional outcomes
Greater complications with anterior surgery 47% vs 29% in posterior surgery
AO Spine Clinical Practice Recommendations

Strong recommendation for surgeons that a ventral or dorsal approach for patients with DCM, in whom there is clinical equipoise, is equivalent in terms of functional recovery, pain, and quality of life.
The differing adverse event profile between ventral and dorsal approaches should be considered as part of a shared decision-making process with the patient.

Anterior compared to posterior approach: ant has:

lower infection rate
less blood loss
less postoperative pain

Anterior cervical diskectomy/corpectomy and fusion

Extensive dorsal osteophytes extending beyond the disc space, especially if associated with OPLL may require a corpectomy for more complete decompression.

ACDF

Indications

Mainstay of treatment in most patients with single or two-level disease
Fixed cervical kyphosis of > 10 degrees

anterior procedure can correct kyphosis

Compression arising from 2 or fewer disc segments
Pathology is anterior (OPLL, soft discs, disc osteophyte complexes)

Approach

Uses Smith-Robinson anterior approach

Cons

Avoid in patients with poor swallowing function

Anterior corpectomy and fusion (ACF)

indications

extensive retrovertebral disease
cervical kyphosis preventing from adequate decompression posteriorly

technique

anterior decompression and plate alone

amenable in up to 2-level corpectomy

Not for 3 level. If need 3 go for 360 fusion

use of static anterior cervical plate with struct graft

corpectomy and strut graft may be required for multilevel spondylosis (see below)

two level corpectomies tend to be biomechanically vulnerable (preferable to combine single level corpectomy with adjacent level diskectomy)
7% to 20% rates of graft dislodgement with cervical corpectomy with associated severe complications, including death, reported.

Graft vs No Graft

Evidence suggests that for a single level discectomy, there is no difference in outcome between decompression alone, compared to decompression with the addition of a graft.
Not using a graft reduces the cost and operative time as well as avoids graft related complications such as harvest site pain.

Autograft vs Allograft

Autograft

gold standard with which other techniques are compared.

Allograft

Modern synthetic cages made of

carbon fibre
Titanium
polyether- ether- ketone (PEEK)

Pros

No morbidity of donor site including

Pain
Wound infection
Haematoma
Peripheral nerve injury or irritation

Anterior plating

For plating

adds stability and strength in extension.
It provides the strongest possible anterior surgical construct
is useful in correcting kyphosis

Not for plating

plates can increase the incidence of dysphagia.

Dynamic vs fixed plates

Dynamic has better fusion rates

Cervical disk arthroplasty

Expert opinion Mark Kotter: Perform arthroplasty if

Radiculopathy
No instability

Evidence

Arguments for Arthroplasty: Arthodesis has the following issues.

Lack of pain relief

Loss of motion

Pseudarthrosis

Sagittal balance

Adjacent segment disease (ASD)

Hilibrand et al. (1999) noted symptomatic ASD requiring treatment in 2.9% per annum.

Debate is ongoing about whether this is due to the arthrodesis or the natural history of the disease.

Studies have demonstrated increased biomechanical strain (intradiscal pressure) and increased motion at adjacent levels following arthrodesis.

Prospective trials have examined the kinematic effect of cervical disc replacements on the spine and have compared the outcomes between arthroplasty and arthrodesis.

Badhiwala 2020 Meta-analysis Cervical disc arthroplasty (CDA) vs ACDF (both myelopathy and radiculopathy)

For one-level outcome = adjacent level surgery

At 2 year

no difference in the rate of adjacent-level operation between CDA (2.3%) and ACDF (3.6%) at 2 years.

At 5 years and persisted to 7 years

A large difference favouring CDA became evident at 5 years and persisted at 7 yrs (4.3% vs. 10.8%, P<0.001).

Significantly fewer patients who underwent CDA required index-level reoperation at all time points out to 7 years (5.2% vs. 12.7%, P<0.001).

For 2 level

At 2 years

No significant difference in adjacent-level operations with two-level CDA (1.7%) versus two-level ACDF (3.4%) at 2 years.

At 7 years

a significant difference favouring CDA became apparent (5.1% vs. 10.0%, P=0.014).

Two-level CDA resulted in fewer index-level reoperations out to 7 years (4.2% vs. 13.5%, P<0.001).

Although arthroplasty is a valid option to offer to patients being considered for anterior cervical discectomy more robust long- term outcome data are awaited.

Heterotopic ossification

Wang et al 2021

Preoperative ossification was identified as a potential risk factor for HO and high-grade HO.
HO and high-grade HO occurred in 67.77% and 11.17% respectively
Patients with high-grade HO had limited ROM of replacement levels and the cervical spine and had a high incidence of ASD compared to those without high-grade HO

Incidence of ASD was higher in patients with high grade HO than without (23% vs 11%)

Bone-graft donor site issue

Arguments against arthroplasty

Cost of implant

250 for arthrodesis
2500 for arthroplasty

Not all patients require arthroplasty

Out of 100 arthroplasty done only 5 actually need arthroplasty

Posterior laminectomy only

Indications

Rarely indicated due to risk of post-laminectomy kyphosis

pros & cons

progressive kyphosis

Evidence

Kaptain 2000: laminectomy only

Incidence of post op kyphosis after multilevel laminectomy =20%
Worst when post op scan showed that the C spine was not lordotic

Posterior laminectomy and fusion

indications

multilevel (=> 3 levels) compression with kyphosis of < 10 degrees/lordotic cervical spine

Diffuse congenital stenosis.

> 13 degrees of fixed kyphosis is a contraindication for a posterior procedure
in flexible kyphotic spine, posterior decompression and fusion may be indicated if kyphotic deformity can be corrected prior to instrumentation
Instability

fusion may improve neck pain associated with degenerative facets

contraindications

fixed kyphosis of > 10 degrees is a contraindication to posterior decompression

will not adequately decompress spinal cord as it is "bowstringing" anterior

Fusion or no fusion

Awaiting for POLYFIX DCM RCT

Decompression Fix vs decompression (2 more or lamina)

For fusion

Kotter 2020 PCT 208

Laminectomy + fusion

Had greater meaningful improvements
Longer operative duration
Similar hospital stay and complication

McAllister et al., 2012:

The incidence of instability following laminectomy is reported as being anywhere from 6% to 46%

Kaptain 2000: laminectomy only

Incidence of post op kyphosis after multilevel laminectomy =20%
Worst when post op scan showed that the C spine was not lordotic

Dios 2021 Swiss registry data

In general fusion patient had more

Smokers
Worse myelopathy scores
Spondylolisthesis
Kyphosis

After correcting for the above

They found fusion was better than non-fusion in terms of patients reported outcomes
Fusion had a greater cost 4700USD per patient

Against fusion

Longer operation
Screw complications
Metal work complications

Posterior Laminoplasty

indications

Pt with cervical lordosis + >3 levels of posterior disease
Young pt with a stable spine but myelopathic

useful when maintaining motion is desired
congenital cervical stenosis

avoids complications of fusion so may be indicated in patients at high risk of pseudoarthrosis

contraindications

cervical kyphosis

> 13 degrees is a contraindication to posterior decompression
will not adequately decompress spinal cord as it is "bowstringing" anterior

severe axial neck pain

is a relative contraindication and these patients should be fused

outcomes

Blizzard 2017 Single surgeon retrospective study 41 Laminoplasty vs 31 laminectomy + fusion

Similar JOA, SF-12 and VAS scores, cervical sagittal alignment between the two cohorts.
Range-of-motion decreased in both cohorts, but to a greater degree after laminectomy with fusion.
Laminoplasty had better complication rates (C5 nerve root Palsy), shorter length of stay and cost

Combined anterior and posterior surgery

Indications

multilevel stenosis in the rigid kyphotic spine
multi-level anterior cervical corpectomies
postlaminectomy kyphosis
Cases requiring in 3-level corpectomy and above

Sasso 2003

6% failure rate after 2-level corpectomy
71% failure rate after > =3-level corpectomy

combined anterior corpectomy and posterior fixation

use of anterior strut graft and plating combined with posterior lateral mass screw construct

Outcome

Karim et al 2021: Does surgery provide benefit for all grades of DCM: YES

12 months after surgery, patients with DCM gain disability and QOL benefit from surgical decompression but not pain and myelopathy benefits

Benefits of surgery are most pronounced in patients with severe disease

Early recognition and treatment prior to spinal cord damage is critical for good clinical outcomes

60– 70% of myelopathic patients improve

30% having stable disease

10% continue to progress

Fusion rates

for a single level discectomy approach 100%,

but decrease with multilevel discectomies.

If multilevel discectomy is indicated, supplemental anterior plating may confer a biomechanical advantage with increased stability while fusion occurs.

Can reduced with

Smoking
NSAIDS

More than one- level corpectomy is associated with a higher rate of implant dislodgment and failure.

Therefore, many surgeons favour multilevel discectomies or augment the anterior construct with posterior instrumented fusion, which improves biomechanical stability and fusion.