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previously visited OSSIFICATION OF THE POSTERIOR LONGITUDINAL LIGAMENT
Contributed by: John To, Radiologist, Howard Young Health Care Ministry Health Care, Wisconsin, USA.
Patient: 35 year old female
History: Neck pain
Images:[small]larger

Fig. 1: Sagittal Proton Density weighted image

Fig. 2: Sagittal T1-weighted imgage.

Fig. 3: Sagittal FSE T2-weighted image.

Fig. 4: T2*-weighted axial image at the C5-6 level.

Fig. 5: T2-weighted axial image through C4-5 showing severe ventral spinal cord compression by the ossifiied PLL.

Fig. 6: Lateral plain radiograph showing severe ossification of the posterior longitudinal ligament.
Findings: OPLL is diagnosed when ossification originates within or spans the space between two discs to involve the ligament overlying the centrum of the vertebral body in between.
Diagnosis:

Ossification of the Posterior Longitudinal Ligament (OPLL)

Discussion:

Epidemiology

Japanese have high incidence; prevalence of about 2% in asymptomatic adults.

Incidence of 0.2 to 0.7% in Caucasians.

Increases with age. In Japanese men >60 years of age, more than 10% have OPLL.

Male predominance.

Regional Anatomy

PLL provides axial support to the spine; it originates at the basiocciput, extends along the posterior aspect of the vertebral bodies and intervertebral discs and inserts into the sacrum. Spcifically opposes flexion forces to the spine.

PLL has segmental attachments to the disc annuli and adjacent vertebral body cortex, but is usually separated from the cortex of the midvertebral body by a space containing the basivertebral venous plexus. In the cervical level, the ligament is normally uniformly broad and flat, but at lower levels it is contracted to the midline behind the vertebral bodies. Usually 1-2 mm thick. When hypertrophied and ossified, the ligament encroaches upon the spinal canal.

Pathology

Pathogenesis

Etiology unknown, but high incidence of DISH among OPLL patients suggests a hereditary diathesis of spinal ligament ossification.

Decrease in calcium resorption in the small intestine is reported in OPLL.

Possibility of an autosomal dominant inheritance. Incidence of OPLL among family members of second order kinship to the patient is about 30%, (15 times the general incidence).

High incidence of diabetes among patients with OPLL. 28% of patients with OPLL have diabetes and 18% are borderline diabetics. The incidence of OPLL in diabetic patients was 16%.

HLA BW-40 and SA5 more common in Japanese with OPLL. B27 not associated with disease.

The process of OPLL is similar to heterotopic bone formation in response to mechanical stress in other tissues. Cartilage cells proliferate first in the periosteum of the vertebral body and then in the annulus fibrosus, longitudinal ligament and dura. The ligament becomes calcified by endochondral ossification. Mature lamellar bone is eventually formed. Rate of growth varies. May be cuboidal, triangular, or polypoid in shape.

Pathophysiology

Only a minority of patients with OPLL are symptomatic. Therefore, patients may be able to compensate for deep indentations in the ventral spinal cord. Patients with congenital spinal stenosis may be predisposed to earlier symptoms if OPLL present. Symptoms also worsened by formation of degenerative osteophytes and/or hypertrophied ligament flavum.

Natural history of OPLL is that of progressive enlargement laterally, posteriorly, and longitudinally. Mean annual increasse in OPLL size was 1.0 mm in superoinferior dimension and 0.67 mm in the AP direction.

Relatively good spinal cord function perserved through development of ossification; probably due to a high degree of tolerance to slowly increasing mechanical pressure. Decompensation usually occurs after 50-60% of the AP diameter of the spinal canal is occupied.

Mild traumatic forces may cause complete tetraplegia.

Gross

Extensive damage to the cord is seen to gray matter and long tracts, but also to the central cord.

Necrosis, cavitation, and venous stasis are seen in gray matter, and demyelination, axonal loss and status spongiosus occur in the white matter. Probably partial restriction of spinal cord circulation is responsible in part to some of the spinal cord pathology. Corresponds to regions fed by the terminal supply of the central artery after it arises from the anterior spinal artery, i.e. ischemia or venous stasis in the boundary area between the anterior and posterior spianl artery territories in the spinal cord.

Nerve roots may be atrophied and demyelinated especially where they penetrate the dura.

Microscopic

Most severe destruction in the central gray.

Most seriously damaged parts of the spinal cord show tissue necrosis and cavity formation involving the central parts of the gray matter extending to the ventral part of the posterior columns.

Horn cells were reduced in number and size.

Demyelination observed in the white matter.

Stages of Spinal Cord Damage by OPLL

StagePathological Change
0Normal or mild compression of anterior horn without neuronal loss.
1Mild compression of ant. horn with partial neuronal loss.
2Marked deformity of anterior horn ; severe neuronal loss.
3Severe spinal cord damage with cystic loss.

From Mizuno J et al., Neurological Research 14:312, 1992.

Location

OPLL can occur at any level. Cervical, 75%; thoracic, 15%; and lumbar, 10%.

1. Segmental. Discrete sites of ossification adjacent to a single vertebral body.

2. Localized. Span a single disc but involve two adjacent vertebral bodies.

3. Continuous. Span two or more discs.

4. Mixed

(In the cervical spine, 32% segmental, 35% continuous, 32% mixed, 3% localized)

Most commonly seen at C4, C5, and C6. Average number of levels involved is three. The narrowing ratio (ratio of maximal thickness of OPLL to the AP diameter of the spinal canal on lateral C-spine films) is higher in the mixed and continuous types than in the segmental and localized types.

Clinical Features

1. Progressive cervical myelopathy with or withour radiculopathy.

2. Weakness of upper extremity

3. Numbness in the hands.

4. Neck pain.

Initial Symptom of OPLLFrequency
Neck pain42%
Dysesthesia upper extremity48%
Motor dysfunction upper10%
Dysesthesia lower extremity19%
Motor dysfunction lower15%
Bladder disturbance1%

Almost all patients with OPLL have only mild subjective complaints, such as neck pain and numbness in the hand. Most do not have disturbance in activity of daily living.

Spastic gait and clumsiness of the fingers were present in 15 and 10% respectively.

Average age of onset of the initial symptoms was 50 years. From symptoms to diagnosis was 8 months.

Japanese Orthopedic Association (JOA) scoring system of severity of myelopathy.

<7 severe myelopathy

8-12 moderate myelopathy

>13 mild myelopathy

An acute development or aggravation of tetraparesis after minor trauma was noted in 20% of cases.


Laboratory and Imaging

Diagnosis is by radiography.

Plain films only useful in 1/3 or cases.

MRI should be the initial study for a patient with non-traumatic myelopathy. OPLL appears as an area of low signal.

CT-Myelogram provides better resolution of osseous anatomy. Longitudinal retrovertebral opacity seen. On average, 3 levels are involved.

Treatment

Conservative Therapy

If patient does not have myelopathy.

Conservative treatment consists of continuous skull traction with a Halo (not sure I agree with this); elimates dynamic irritating factors.

Almost all those with severe myelopathy cannot be treated sufficiently by conservative therapy.

Study of patients with mild disturbance of ADL after conservative treatment and followup after 5 years showed:

55% No change

27% Improvement

19% Aggravation of symptoms

Surgical Indications

JOA score of 6-12 points.

Young patients with severe spinal stenosis even if their myelopathy is not as severe.

Pain, radiating to the upper arm, refractory to medical management.

Anterior Decompressive Procedure

More extensive surgery than posterior decompression.

The ossified ligaments compressing the spinal cord are either extirpated or are floated.

In the segmental and localized types of OPLL below the C3-C4 level, anterior decompression and vertebral body fusion is generally the preferred approach when fewer than 3 disc levels are affected.

This operation produces particularly good results for patients with clumsiness of the fingers, severe intrinsic muscle atrophy caused by lesions of the anterior horn cells or both.

Posterior Decompressive Procedure

In the continuous type of OPLL, extensive laminectomy and expansive laminaplasty for posterior decompression have been performed.

Posterior decompression is performed as far as one level below and above the stenotic site. Nerve root decompression can also be achieved at the open side.

Although posterior surgery for the spinal cord compressed by OPLL anteriorly is not true decompressive surgery, it is considered a much safer and easier procedure in the severely deteriorated spinal cord compared with anterior surgery.

Hirabayashi devised the open door expansive laminaplasty for posterior decompression because he had observed dural tube pulsation before resection of the laminae as a whole; allows widening of the stenotic spinal canal without structural loss caused by laminectomy, in which postoperative malalignment and instability may occur.

Advantages of Laminoplasty

1. Easier and safer.

2. Postoperative support is better than laminectomy.

3. Postoperative dynamic factor can be eliminated, becuase the range of motion of the preoperative cervical spine has been reduced to 50% by ankylosing of the bony gutter on the hinge side. (In the continuous and mixed types of OPLL, the ossified ligaments may be biologically stimulated by the operative procedure, which may accelerate the postoperative growth of OPLL; the structural weakness caused by laminectomy may evoke postoperative growth of OPLL as a compensatory process.)

Complication of Laminoplasty

1. Closure of the opened laminae. (Adding stay sutures between spinous processes and facet capsules may help keep it open).

2. Transient muscle paraparesis of the shoulder girdle and severe neck pain. Results from tethering effect of the nerve roots of C5 or C6.

Results of Surgery

Operative results influenced by preoperative factors.

degree of disability of ADL

duration of myelopathy

age of patient

onset with or without trauma

stenotic condition of the spinal canal

kyphotic curvature of the spine

Better operative results could not be obtained in patients over 65, those with severe disability of ADL (JOA < 7), myelopathy more than 2 years; traumatic onset; severe spinal canal stenosis; and kyphotic curvature of the spine.

Growth of OPLL is more frequent in the continuous and mixed types, than in the segmental type. After 5 year followup, overall incidences of longitudinal and transverse growth of OPLL were 24 and 11% respectively in nonoperative cases, 28 and 24 % in operative cases.

Incidences of postoperative growth of the continuous and mixed types.

Surgical Approach

Incidence of Post-op Growth

laminectomy

89%

laminoplasty

34%

anterior decompress and fusion

20%

Comparison between laminectomy and laminoplasty showed a significant difference in transverse growth but not in longitudinal growth.

References:

Harsh GR et al., Cervical spine stenosis secondary to ossification of the posterior longitudinal ligament. JNS 67: 349-357, 1989.

Kojima T et al., Anterior cervical vertebrectomy and interbody fusion for multilevel spondylosis and OPLL Neurosurgery 24: 864-873, 1989.

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Additional Details:

Case Number: 8390888Last Updated: 03-09-2007
Anatomy: Spine and Peripheral Nervous System   Pathology: Metabolic
Modality: Conventional Radiograph, MRExam Date: 03-09-2007Access Level: Readable by all users
Keywords: opll, japanese disease

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