n_spinalcord

Spinal cord syndromes and lesions

Arterial supply of the cord:

2 main sources:

  • paired vertebral arteries form the rostral origin of:
    • single anterior spinal artery
      • runs the entire length of cord in midline supplies the anterior 2/3rds of the cord
    • paired posterior spinal arteries
  • radicular arteries (the largest being the artery of Adamkiewicz which arises on the left side of the aorta between the T8 and L1 segments):
    • provide important contributions to the ant & post. spinal arteries
    • the artery of Adamkiewicz sends branches cephalad as high as T4 and also provides supply to the lower two-thirds of the spinal cord (conus medullaris) and thus lesions of this artery produce motor deficits of the legs and faecal and urinary incontinence

Vertebral movements:

cervical spine:

  • flexion - 50% at atlanto-occipital joint, remainder evenly spread between other Cx vertebrae although slightly more at C5-6.
  • rotation - 50% at atlanto-axial joint, remainder spread between other Cx vertebrae

thoracic spine:

  • limited ROM with little or no flexion or extension but rotation occurs

lumbar spine:

  • flexion/ext. ROM proportional to thickness of discs & joint surface area ie. maximal @ L5-S1.

Cord syndromes:

complete cord syndrome:

  • complete transections can be either:
    • acute (over minutes)
      • ⇒ loss of motor, sensory &autonomic function below the level
      • ⇒ in addition, all reflex function below level of lesion is lost due to spinal shock
      • ⇒ if Cx then may interrupt all sympathetic fibers before they exit in T1-10 roots
      • ⇒ functional sympathectomy
      • ⇒ decreased systemic & pulm. vascular resistance
      • ⇒ relative increase in vagal tone ⇒ decreased cardiac contractility & output
      • ⇒ bradycardia & hypotension
      • ⇒ gastric atony, bowel & bladder dysfunction, impaired temp. regulation
      • ⇒ if C3-5 lesion ⇒ diaphragmatic paralysis
      • usually due to trauma, but also infarction, haemorrhage & acute disc herniation
    • subacute (over hours to weeks)
      • ⇒ may have hyperactive DTRs below level of lesion & an upgoing plantar response
      • transverse myelitis (hrs to days)
      • spinal epidural tumours

Brown-Sequard syndrome:

  • hemisection of the cord is rare & usually caused by penetrating trauma
  • ⇒ ipsilat. loss of motor function & proprioception with contralat. loss of pain & temp. sensation.
  • ⇒ ipsilat. loss of pinprick at level of lesion as fibers haven't crossed to contralat. lat. spinothalamic tract yet
  • ⇒ analgesia may be noted 1-2 segments above lesion to as fibers in lat. spinothalamic tract move up & down 1-2 segments before crossing.

Anterior cord syndrome:

  • rare (5-8% of acute myelopathies, ~1% of strokes; aka Beck's syndrome) with different aetiologies depending upon age:
    • children:
      • most common causes are cardiac malformations and trauma
    • adults:
  • onset is usually rapid, peaking within 12 hours in over half of patients and within 72hrs in the majority
  • most have initial severe back pain at the level of the lesion followed by urinary dysfunction and may have initial paradoxical sensory symptoms rather than motor, although paraplegia then develops over hours
  • severity and extent is variable
  • there is sparing of the posterior columns ⇒ position & vibratory sense are intact
  • thus results in loss of motor function with flaccidity and loss of reflexes, pinprick & light touch below level of lesion
    • autonomic dysfunction may be present and can manifest as hypotension (either orthostatic or frank hypotension), sexual dysfunction, and/or bowel and bladder dysfunction - most require IDC
    • spasticity and hyper-reflexia develop during ensuing days and weeks
    • incomplete syndromes
      • acute paraplegia without sensory or bladder dysfunction
      • man-in-the-barrel syndrome if cervical: painful bilateral brachial diplegia
      • progressive distal amyotrophy
  • MRI: hallmark of spinal cord infarction is the presence of abnormal T2 signal within the cord and if the region is small, resulting in pencil-like hyperintensities which give two bright dots, the so-called owl eye appearance on axial imaging.
  • prognosis: of those who survive, 20% will be wheelchair bound and require permanent IDC

Central cord syndrome:

  • this is the most prevalent of the partial cord syndromes.
  • ⇒ mnemonic:
    • Motor > sensory
    • Upper limb involved > lower limb
    • Distal involved > proximal
  • ⇒ bilateral motor paresis with variable sensory & bladder dysfunction

Syringomyelia:

  • progressive cavitation of spinal cord that extends over several metameric segments, usually Cx & Tx.
  • causes of syringomyelia:
    • frequently found in assoc. with Arnold Chiari I malformations
    • development defects
    • arachnoiditis
    • previous spinal column surgery
  • ⇒ involvement of the decussating fibers of the lateral spinothalamic tract
  • ⇒ segmental loss of pain & temperature bilaterally
  • ⇒ late manifestations may include lower motor neuron disturbances owing to lateral extension of cavity into anterior grey horns.

Conus medullaris syndrome:

  • isolated lesions of the conus medullaris (the terminal end of the cord - at L1 in adults) are rare
  • ⇒ denervated autonomic bladder
  • ⇒ primary sphincteric involvement
  • ⇒ loss of sexual function
  • ⇒ sensory may involve lower sacral/coccygeal segments or be a complete saddle anaesthesia
  • ⇒ mixed upper & lower motor neuron deficits involving gluteal muscles depending on extent
  • ⇒ absent bulbocavernosis reflex
  • causes of this syndrome:
    • trauma, neoplasms, acute centrally herniated lumbar disc, vascular insufficiency.

dissociated sensory loss:

  • spinothalamic (pain & temperature) loss only:
    • syringomyelia ('cape' distribution)
    • Brown-Sequard syndrome (contralateral leg)
    • anterior spinal artery thrombosis
    • lateral medullary syndrome (contralat. to the other signs)
  • dorsal column (vibration & proprioception) loss only:
    • B12 deficiency
    • Brown-Sequard syndrome (ipsilat. leg)
    • spinocerebellar degeneration (eg. Friedrich's ataxia)
    • multiple sclerosis
    • tabes dorsalis
    • peripheral neuropathy - diabetes, hypothyroidism

Mnemonic for differential diagnosis of disease states that cause spinal pathology:

  • Vascular
  • Infectious, idiopathic
  • B12 deficiency
  • Radiation
  • Amyotrophic lateral sclerosis
  • Tumour, trauma, toxic/metabolic
  • Epidural abscess, electricity
  • Developmental, hereditary
  • Spondylosis
  • Paraneoplastic
  • Arachnoiditis
  • Syringomyelia
  • Myelitis, MS
  • Systemic disorders

References:

  • Wagner R, Jagoda A Spinal Cord Syndromes: Em Med Clin North Am 15(3):699-711 August 1997.
n_spinalcord.txt · Last modified: 2018/08/08 09:16 by wh