Acute Spinal Cord Compression

Acute compression of the spinal cord is when symptoms occur within 24 hours. As the spinal cord has very limited powers of regeneration, decompression is a matter of urgency.

Anatomy

The following anatomical considerations are relevant:

• The spinal cord is shorter than spinal canal.
• The cord ends between the L1 and L2 vertebrae in adults and between L2 and L3 in children.
• Below the termination of the cord the nerve roots form the cauda equina.
• In the cervical spine segmental levels of cord roughly correspond to bony landmarks.
• Below this level there is increasing disparity between levels.
• Spinal pathology below L1 of the vertebral column produces only root signs.
• Comparing the cross-sectional area of the cord and the vertebral column, there is relatively less room in the cervical region than lower down. Hence tumours such as meningiomas or haematomas have less room to grow before they compress the spinal column.

• Trauma including vertebral body fracture or facet joint dislocation.
• Tumours, both benign or malignant.¹
• This can include tumours of bone, primary or metastatic, lymphomas or even neurofibromata or extramedullary haemopoiesis² in untransfused thalassaemia.
• Prolapsed intervertebral disc.
• Osteophyte formation.
• Haemorrhage may be epidural or subdural haematoma.
• Inflammatory disease, especially rheumatoid arthritis.
• Infection, often tuberculosis or pyogenic infections. The incidence of intraspinous infection is said to be 1 per million per year in the UK. In the UK it is usually a staphylococcal infection but in Africa and Asia, tuberculosis is more common. Pott's disease of the spine (tuberculosis) has its own article. Discitis tends to affect children more than adults. Epidural abscesses can easily be missed and they may cause spinal cord compression.

Risk factors for infection can include diabetes mellitus and intravenous drug abuse.

In rheumatoid arthritis there is often considerable weakness of the ligament that holds the odontoid peg. If this ruptures the atlas can slip forward on the axis and compress the high cervical spine. There are anecdotes of this happening with great rapidity but usually it occurs over weeks or months.

Damage to the spinal column is a very rare complication of chiropractic or osteopathic type manipulation of the neck, as has been described in manipulation - the level of evidence. The incidence of serious adverse reactions such as acute spinal cord compression or dissection of the vertebral arteries is difficult to assess but is probably around 0.5 to 2 cases per million treatments.

Symptoms

Clinical features depend upon the extent and rate of development of cord compression. Signs and symptoms are those of a myelopathy but the common feature of "structural" lesions is pain. Spine or root pain in the presence of myelopathic symptoms strongly implies a surgically remediable cause.

• Motor symptoms including ready fatigue and disturbance of gait.
• Cervical spine lesions produce quadriplegia.
• Thoracic spine lesions produce paraplegia.
• Lumbar spine lesions affects L4,5 and sacral nerve roots.
• Sensory symptoms include sensory loss and paraesthesia.
• Light touch, proprioception and joint position sense are reduced.
• "Root pain" in the legs.
• Spinal pain is typical in cases than are amenable to surgery.
• If movement causes pain this suggests vertebral fracture or collapse.
• Low-grade background pain suggests tumour infiltration or osteomyelitis.

Signs

Tendon reflexes can give false reassurance³ but typical features are:

• Increased below level of compression.
• Absent at level of compression.
• Normal above level of compression.
• Reflex changes may differ from the sensory level.
• Sphincter disturbances are late features of cervical and thoracic cord compression.
• There may be loss of autonomic activity with lack of sweating below the level, loss of thermoregulation and drop in peripheral resistance causing hypotension.

Cauda equina compression produces a characterisitc picture but not all features will be found:

• S2,3,4 gives rise to the parasympathetic outflow and the pudendal nerve supplying the skin, muscles and organs around the perineum. There can be loss of perineal sensation called saddle anaesthesia or "numb bum syndrome", dorsal penile or clitoral, vaginal, and scrotal or labial sensation is impaired. The pudendal nerve supplies the posterior thirs of the scrotum or labia majora, the anterior two thirds coming from L1.
• Painless retention of urine or micturition difficulty may result. Erection, ejaculation and parturition difficulties may occur.
• Lax anal sphincter as shown on digital rectal examination.
• Exquisite tenderness suggests an epidural abscess.

• Multiple Sclerosis
• Transverse Myelitis
• Motor Neurone Disease
• Acute post viral, Guillain Barré syndrome
• Subacute Combined Degeneration of the cord
• Anterior Spinal Artery Syndrome
• Parasagittal Meningioma

• Plain x-rays may show lesions of bone or soft tissues.
• They may show vertebral collapse, osteolytic lesions or loss of vertebral pedicle.
• The state of the of discs may point to the diagnosis.
  • "Good disc = bad news" often indicates malignancy.
  • "Bad disc = good news" may indicate infection.
• MRI is best to define extent of soft tissue disease.
• Bone scan may indicate pattern and extent of bone pathology.

• Acute cord compression is a neurosurgical emergency.⁴
• In those with malignant disease radiotherapy may be the best treatment.
• Tumour, infection and disc disease usually produce anterior compression.
• Surgical decompression should be through an anterior approach.

Cauda equina compression is usually due to central lumbar disc prolapse. Although it is not strictly compression of the spinal cord it is still a neurosurgical emergency requiring immediate admission for MRI and decompression. However, the degree of emergency to operate is a matter of debate.⁵

The complications of acute spinal cord compression are related to irreversible damage to the cord if it is not decompressed very soon. The spinal cord is part of the CNS and so has very limited powers of regeneration. Compression at the level of the thoracic spine causes paraplegia. Compression in the neck causes quadriplegia and if it is above the level of C3,4,5, that is the segmental level of the phrenic nerve, the diaphragm is paralysed and artificial ventilation is required.

• Prognosis depends on severity and duration of neurological deficit before decompression.
• Even in spinal cord compression from metastatic cancer it is possible to relieve pain in 90% and to manage terminal care with dignity.⁶ About 1 case in 6 has metastasis at more than 1 level.
• The prognosis for cauda equina syndrome is good if decompression is not delayed.

• When car seatbelts were introduced, it had a beneficial effect on reducing deaths and injuries in the comparatively few who bothered to wear them before they became compulsory. However, the risk of severe whiplash injury causing trauma to the cervical cord was increased until head restraints became standard in all cars.
• It can be argued that motor cycle crash helmets, because they make the head heavier, increase the risk of damage to the cervical spine. However, on balance, they do far more good than harm.
• Amongst sports, rugby has an unenviable place in terms of injuries to the cervical spine. Recent changes in the rules have attempted to reduce the risk of serious damage to the neck, especially in front row forwards. Hookers represent just 1 player in 15 but they represent 50% of spinal cord injuries in rugby.
• Equestrian sports remain a high risk for cervical spine injuries.