Disorders of Spinal Cord – Anatomy Clinical Significance

Disorders of Spinal Cord – Anatomy Clinical Significance

Disorders of Spinal Cord/Spinal cord disorders can originate from either outside or inside the spinal cord. Damage from the outside of the cord is caused by compression of the spinal cord or injury. The spinal cord may be compressed due to a bone fracture, spinal degeneration, or abnormalities, such as a hematoma, tumor, or herniated disk

Your spinal cord is a bundle of nerves that runs down the middle of your back. It carries signals back and forth between your body and your brain. It is protected by your vertebrae, which are the bone disks that make up your spine. If you have an accident that damages the vertebrae or other parts of the spine, this can also injure the spinal cord. Other spinal cord problems include

Classification is based on the level of neurological impairment, as per the American Spinal Injury Association classification:

  • Total loss of motor and sensory function
  • Loss of motor function only
  • Presence of sensory function and less than useful motor function (< grade 3/5).
  • Presence of sensory function and abnormal but useful motor function (>/= 3/5)
  • Intact neurological functions

Specific spinal cord injuries may include the following:

  • Special injuries of the upper cervical vertebra (craniocervical dislocation and atlantoaxial instability)
  • Occipital condyle fracture (mainly associated with accompanying head injuries)
  • Jefferson’s fracture (burst fracture of the C1 ring)
  • Odontoid fractures (can be type I, II or III depending on the extent of the fracture line)

Other special fractures include the following:

  • Wedge fractures: compression of a vertebral body either laterally or anteriorly, forcing it to take the shape of a wedge
  • Hangman’s fracture: fracture of both pedicles of the C2 vertebra. It depicts the pathophysiology behind death in hanging, where fracture of this vertebra leads to compression of the spine at a high level of inhibition of respiratory function as well as allowing for mechanical compression of the airway.
  • Burst fracture
  • Teardrop fracture
  • Facet dislocation

Disease and Disorders of Spinal Cord

Spinal cord disorders, injuries (SCIs), or syndromes may include (but are not limited to)

  • Traumatic (ground-level falls in the elderly, high-energy motor vehicle accidents in any age group)

    • The incidence and prevalence of traumatic SCI in the United States is higher compared to rates reported in the literature for other countries worldwide
    • The average age at clinical presentation continues to increase, corresponding to the aging of the general population
    • Heightened clinical suspicion should be given to vertebral compression fractures which can occur spontaneously (i.e., in the absence of trauma)
  • Infection
  • Tumors/malignancy (including metastatic disease)
  • Disc herniations
  • Spinal stenosis/degenerative conditions/facet arthropathy
  • Syringomyelia

In general, the extent of disability depends on the level of injury and the underlying degree of severity of the corresponding clinical pathology.  For example, injuries at the levels of the cervical segment affect both upper and lower limbs while lesions from thoracic segments downwards affect the lower limb.

Spinal cord injury (SCI) patterns

  • Descriptive

    • Tetraplegia

      • Cervical spine injury resulting in impaired arm/trunk/leg/pelvic organ function
    • Paraplegia

      • Thoracic/lumbar/sacral spinal injury leading to impaired trunk/leg/pelvic organ function
      • Preserved arm function
    • Complete injuries

      • By definition, a complete SCI yields no sparing of the motor or sensory function below the injured level

        • The patient must have already recovered from the acute phase of spinal shock (usually 48 hours from presentation)
        • Spinal shock: by definition, the temporary (typically 48 hours) loss of all spinal cord function (including reflex activity) below the level of injury

          • Absent bulbocavernosus reflex
          • Flaccid paralysis
          • Bradycardia/hypotension
  • Spina bifida – Neural tube defect in which the neural tube does not completely close leaving a dorsal defect. Folate deficiency in early pregnancy is a risk factor. The severity of symptoms depends on the extent of the defect; myelomeningocele is the most severe variant with the spinal cord, meninges both exposed. Other variants include meningocele, which exposes only the meninges, and spina bifida occulta which is the mildest. Symptoms include loss of lower limb sensations, lower limb weakness, urinary incontinence, bowel incontinence

Incomplete spinal cord injuries (SCIs)

  • Central cord syndrome

    • Most common incomplete SCI
    • Pathophysiology: central gray matter injury
    • Mechanism(s): hyperextension (i.e., from a fall) in a patient with underlying cervical spinal canal stenosis
    • Clinical presentation:

      • Upper extremity loss of motor function (lower extremity motor function no affected/minimally affected)
      • Sensory sparing variable
    • Prognosis: Good
  • Anterior cord syndrome

    • Second most common incomplete SCI
    • Pathophysiology: injuries occur secondary to direct compression to the anterior spinal cord (e.g., hyperflexion injuries, anterior spinal artery occlusion, or disc prolapse)
    • Mechanism(s): hyperflexion injuries, anterior spinal artery occlusion, disc prolapse
    • Clinical presentation:

      • Loss of motor, pain, and temperature reception below the level of injury
      • Preserved dorsal column function (i.e., proprioception, vibration sensation, and deep pressure sensation)
    • Prognosis: Poor (for motor recovery specifically)
  • Posterior cord syndrome

    • Very rare/least common incomplete SCI pattern of injury
    • Pathophysiology: injury to the dorsal column
    • Mechanism(s):

      • subacute combined degeneration
      • tabes dorsalis (i.e., secondary to syphilis)
      • multiple sclerosis
      • vascular malformations (arterio-venous malformation – AVM)
      • malignancy (e.g., compressive extramedullary tumors)
      • degenerative conditions (e.g., spondylosis)
    • Clinical presentation:

      • Loss of proprioception, vibration, and deep pressure sensation below the level of injury
      • Preserved ambulatory function

        • patients will complain of difficulty balancing in the dark or with his/her eyes closed
      • Classic exam consistent with a positive Romberg sign
    • Prognosis: Preserved ambulatory function; dorsal column recovery unpredictable
  • Spinal cord hemisection/hemicord (Brown-Sequard syndrome)

    • Rare (2% to 4% of SCIs)
    • Pathophysiology: trauma to one side of the spinal cord (in cross-sectional reference)
    • Mechanism(s):

      • Penetrating trauma (knife, gunshot wound)
    • Clinical presentation:

      • Ipsilateral loss of motor and proprioception (directly below the level of injury)
      • Contralateral loss of pain/temperature

        • Classically the contralateral pain/temperature loss occurs one to two levels below the level of injury)
    • Prognosis: 90% recover ambulatory function
  • Cauda equina syndrome

    • Pathophysiology: Injury to (only) the nerve roots of the cauda equina itself (i.e., spares the spinal cord itself)
    • Mechanism(s):

      • disc herniations
      • burst fractures (e.g., associated hematoma from trauma)
    • Clinical presentation:

      • bilateral buttock/lower extremity pain
      • bowel/bladder dysfunction (urinary retention)
      • saddle anesthesia
      • loss of lower extremity motor/sensory function

        • differentiated from conus medullaris syndrome in that findings are asymmetrical, as opposed to symmetrical (i.e. conus medullaris motor symptoms are symmetrical on presentation)
    • Prognosis: surgical decompression within the first 48 hours appears to yield improved overall outcomes (although the overall prognosis remains guarded)
  • Conus medullaris syndrome

    • Often confused with cauda equina syndrome, although this must be recognized as a separate clinical entity
    • Pathophysiology: injury to the spinal cord at L1-L2 level
    • Mechanism(s):

      • Direct spinal trauma to the thoracolumbar junction
    • Clinical presentation:

      • Saddle anesthesia
      • bowel/bladder dysfunction (often presents with dysfunction more acutely compared to cauda equina which can evolve over a variable period time prior to the patient’s presentation)
      • classically presents with mild, symmetrical motor symptoms (often mixed upper and lower motor neuron syndromes)

        • can present with both spasticity and flaccid paresis
        • hyperreflexia and/or hyporeflexia
      • Prognosis: guarded

Clinical Significance

Any spinal cord lesion can generally be localized quite easily by understanding the anatomy. There is usually impairment or sensory or motor functions in the lower extremities. It is always important to identify the motor or sensory level to determine the lesion’s exact site. In general, the best imaging modality for any suspected spinal cord lesion is magnetic resonance imaging(MRI).

  • Meningitis: It is the infection of meninges (coverings) of the brain. It can be bacterial or viral. Some of the most common being:

    • Bacterial meningitis: It can be because of bacterias’ infection such as Streptococcus pneumoniaeNeisseria meningitidesListeria monocytogenesE. coliPseudomonas aeruginosaKlebsiellaEnterobacterStaphylococcus aureus, and Staphylococcus albusStreptococcus pneumoniae and Neisseria meningitides are known to be the most common.
    • Tubercular meningitis: It is due to infection by Mycobacterium tuberculosis. It presents with typical features like a stiff neck, fever, increased intracranial pressure, and headache. The CSF shows increased proteins and decreased glucose levels. It is common in children with primary tuberculosis, patients with malnourishment, and immunodeficiencies like HIV and cancer. Even though rare compared to bacterial meningitis, this can lead to high morbidity and mortality if not detected early and treated.
  • Traumatic injuries of the spinal cord: It is the commonest, accounting for almost 90% of all spinal cord injuries. It frequently results from road traffic accidents, falls, and sports injuries. They can have devastating effects on the life of a person. Lesions in the lower thoracic region lead to paraplegia, and that in the cervical area leads to quadriplegia.

    • Compression: It can be due to intervertebral disc herniation or the vertebras’ dislocation leading to compression of the spinal cord. Symptoms due to compression can be paresis to paralysis.
    • Hemisection: Traumatic injuries can lead to an incomplete section of a part of the spinal cord. A classical presentation of a hemisection is the Brown-Sequard syndrome. There is ipsilateral motor loss below the section in this syndrome, contralateral loss of pain, and temperature sensations, with no loss of ipsilateral light touch sensations.
    • Complete section: It is a condition where there is the absence of sacral sparing with no sensation in the segment of S4-5 or the lack of voluntary contraction of the anal sphincter.
  • Vascular injuries of the spinal cord:

    • Anterior cord syndrome: When the anterior spinal artery is blocked, it results in ischemia of the anterior two-thirds of the spinal cord’s area supplied by this artery. This ischemia is the commonest cause of spinal cord infarction, often occurs due to aortic manipulation or dissection. The commonest site is the mid-thoracic level due to the best supplies from the origin from the vertebral artery and the artery of Ademkiewicz near its lower end. It presents itself as an incomplete motor paralysis below the site of the lesion. Also seen is the sensory loss relative to pain and temperature; this is called anterior cord syndrome. It may be more easily recognized if the whole cord is affected, sparing only the dorsal columns.
    • Posterior cord syndrome: It is a syndrome that develops due to ischemia of the posterior spinal artery, affecting the area of the spinal cord supplied by it. It presents itself with an absence of proprioception and vibration sensation, hypotonia, ataxic gait, positive Romberg sign, and the lack of deep tendon reflexes.
    • Central cord syndrome: This is a non-vascular injury of the spinal cord, especially seen in a hyperextended neck after a road traffic accident. It is said to be the most common among incomplete spinal cord injuries. It presents itself with severe sensory and motor function loss in the case of the upper limbs compared with the lower limbs.
  • Development anomalies of the spinal cord:

    • Spina bifida: It is a developmental anomaly of the vertebrates where the laminae fail to fuse with the spinal process. It is said to be one of the most frequent developmental defects of the neural tube. It is usually seen in the lumbosacral region and is identifiable by a tuft of hairs in this region. No other external visible abnormality is visible.
    • Meningocele: In this condition, too, laminae fail to cover the spinal cord leading to protruding of arachnoid and pia mater as a cystic swelling in this region covered by skin.
    • Meningomyelocele: This is an extension of meningocele where the cystic swelling will contain a part of the spinal cord with relevant nerves.
    • Syringo-myelocele: Further to the above, here we see distension of the central canal.
    • Rachischisis: It is a condition where the neural tube fails to close or incompletely closed. This anomaly can develop both in the brain and spinal cord. When it affects the brain, it is called anencephalus, and when the spinal cord, then it is myelocele.
  • Herniation: Herniation of the spinal cord is less frequent and usually misdiagnosed for other conditions.
  • Malignancy: They can present themselves as ependymomas, astrocytomas, and hemangioblastomas. Others include lipomas, lymphomas, germ cell tumors, gangliogliomas, and germinomas. They can also rarely metastases from different parts of the body like breast, bone, etc.
  • Syringomyelia: It is a condition where there is a fluid-filled cavity within the spinal cord. This condition can be due to a disturbance of CSF flow, an intramedullary tumor, or spinal cord tethering.
  • Subacute combined degeneration: It is a rare condition arising due to the deficiency of vitamin B12. It leads to neurological complications with demyelination of the lateral and dorsal spinal cord. Similar pathological findings can also be found in patients with copper deficiency, zinc excess, or HIV infection with myelopathy.
  • Tabes dorsalis: this is selective pathology affecting only the dorsal columns as a late manifestation of neurosyphilis.
  • Transverse myelitis: this is a condition caused by inflammation of the spinal cord. It presents with variable involvement of all functional modalities at and below the site of inflammation. It can occur by itself as an immune-mediated post-infectious problem. It is also commonly involved by an acute relapse of multiple sclerosis. Other inflammatory diseases may also affect the spinal cord, such as Sjogren disease, Behcet’s disease, or neuromyelitis optica spectrum disorder.


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