Spinal Cord Syndromes

Overview

The spinal cord begins at the base of the skull and terminates at the lower margin of L1 where it becomes the cauda equina. Injuries can occur to the spinal cord itself, nerve roots, or spinal nerves.

Spinal cord injuries may be complete or incomplete:

• Complete injuries – where the ability of the spinal cord to convey signals to or from the brain is entirely lost:
• This results in a total lack of sensory and motor function below the level of the injury
• Partial injuries are where this ability is only partially lost and some signals are still able to travel past the injured area
• There is the retention of some motor and sensory functions below the level of the injury.

Understanding spinal cord tracts, where they decussate, and where upper motor neurones (UMNs) and lower motor neurones (LMNs) synapse is essential for interpreting spinal cord disorders.

To read more about UMNs and LMNs, click here. To read more about sensory tracts, click here.

Spinal Cord Tracts: A Summary

Ascending tracts

Sensory tracts:

• Conscious tracts:
  • Dorsal column–medial lemniscus pathway (dorsal columns) – decussate in the medulla:
    • Fine touch, proprioception, and vibration
• Anterolateral system – both decussate in the spinal cord
  • Anterior spinothalamic tract
    • Crude touch and pressure
  • Lateral spinothalamic tract
    • Pain and temperature

Descending tracts

Motor tracts:

• Pyramidal tracts – voluntary control of muscles in the body and face:
  • Corticospinal tract – decussates in the medulla
    • UMNs terminate in the spinal cord where LMNs emerge
  • Corticobulbar tract – decussates above cranial nerve nuclei
    • UMNs terminate in the cranial nerve nuclei where LMNs emerge
• Extrapyramidal tracts

General Features

• Cervical spine injuries are the most severe:
  • Injuries at C1-C4 or above can lead to quadriplegia
  • Injuries at C3, C4, or C5 or above can cause paralysis of the diaphragm and impair breathing (‘C3, C4, C5 keep the diaphragm alive’)
  • Injuries at C5-C8 affect corresponding nerves that innervate the arms and hand
• Thoracic spine injuries:
  • Injuries at T1-T12 can lead to paraplegia – the inability to move the lower limb
  • Injuries at or above T6 can lead to autonomic dysreflexia which can be fatal
• Tendon reflexes can be affected are usually:
  • Normal above the level of the injury (as no UMNs or LMNs are affected)
  • Absent at the level of the injury (as LMNs are affected)
  • Increased below the level of the injury (as the UMNs for reflexes below are affected. UMNs terminate in the spinal cord)

Cauda Equina Syndrome

Overview

Cauda equina syndrome (CES) occurs when the cauda equina (the nerves post-L1) are involved. This can initially present with lower back pain but can lead to potentially irreversible leg weakness and urinary/bowel incontinence.

Causes

• Central disc prolapse (L4/L5 or L5/S1) – most common cause
• Tumours – primary or metastatic
• Infections (e.g. discitis/infection)
• Trauma
• Haematoma

Presentation

There is no key feature that diagnoses or excludes CES, and it can present in many different ways:

• Lower back pain – particularly if new or worsening
• Bilateral sciatica
• Perianal paraesthesia/anaesthesia
• Urinary/bowel dysfunction – a late sign suggesting irreversible damage

Investigations

• Urgent MRI spine:
  • Confirms or excludes CES
  • If an MRI is not possible/contraindicated (e.g. metal implants/pacemakers), then a CT is appropriate

Management

Management involves surgical decompression. If CES is caused by primary or metastatic malignancy, IV dexamethasone should be given to reduce oedema which can worsen CES.

Anterior Cord Syndrome

Anterior cord syndrome occurs due to direct compression of the anterior cord, injuries due to flexion of the cervical spine, or occlusion (e.g. thrombosis) of the anterior spinal artery. Since the descending corticospinal tract (motor) and the ascending spinothalamic tract (sensory) are found anteriorly, these are involved leading to:

• Paralysis below the lesion due to interruption of the corticospinal tract
• Loss of pain and temperature sensation due to interruption of the spinothalamic tract
• Proprioception and vibration are retained – due to the dorsal columns being found posteriorly.

Central Cord Syndrome

Central cord syndrome occurs due to cervical spinal stenosis, ischaemia of the spinal cord, or spinal hyperextension injuries. Its features include:

• Weakness that is worse in the upper limb compared to the lower limb
  • This is because upper limb motor neurones are found more centrally
• A burning sensation is common, particularly in the upper extremities
• There can be varying levels of sensory loss below the lesion

Brown-Séquard Syndrome

Brown-Séquard Syndrome occurs due to damage to half of the spinal cord (e.g. hemisection or unilateral compression).

• This leads to the involvement of:
  • The descending corticospinal tract (motor):
    • Leads to ipsilateral paralysis and LMN signs at the level of the lesion and UMN signs below the level of the lesion
    • UMN features occur below the lesion because UMNs terminate in the spinal cord to become LMNs
    • Since the lesion is in the spinal cord post-decussation (which happens in the medulla after descending from the cerebral cortex), features are ipsilateral
  • The ascending dorsal columns (sensory):
    • Leads to ipsilateral losses in fine touch, vibration and proprioception sensation
    • Since the lesion is in the spinal cord pre-decussation (which happens in the medulla after ascending from the spinal cord), features are ipsilateral
  • The ascending spinothalamic tract (sensory):
    • Leads to contralateral losses in temperature and pain sensation
    • This is because the spinothalamic tracts decussate in the spinal cord

Spinal Cord Compression

Overview

Spinal cord compression may cause:

• UMN signs below the level of the lesion
• LMN signs at the level of the lesion

Causes

• Tumours – the most common cause
• Haematomas
• Infection (e.g. abscesses)
• Fracture

Spinal Shock

There is initial paralysis, decreased tone, loss of sensation, and areflexia below the level of injury. These features are intact above the lesion. Spinal shock follows a pattern:

• Initially: hyporeflexia/areflexia
• Over days to weeks: hyperreflexia and increased tone emerges

If a spinal cord injury occurs above T6, neurogenic shock may occur.

Autonomic Dysreflexia

Usually seen with injuries above T6 and can be triggered by pain, constipation, or urinary retention – these lead to sympathetic activation, which is normally counteracted by the parasympathetic nervous system. These injuries can impair parasympathetic compensation.

Uncontrolled hypertension, sweating, and flushing are seen at the level of the cord lesion alongside bradycardia.

Management involves removing or treating the stimulus and managing hypertension and/or bradycardia.