Cervicothoracic spinal cord (C6-T2)

Disease in this region of the spinal cord typically causes signs of LMN dysfunction in the thoracic limbs and UMN dysfunction in the pelvic limbs. However, patients with C6-T2 disease may have normal thoracic limbs and abnormal pelvic limbs, especially with compressive spinal cord lesions (e.g., intervertebral disk protrusion/herniation). This is because the pelvic limb spinal tracts are more peripherally located than the centrally located lower motor neuron cell bodies in the ventral horn of the grey matter. Mild to moderate external compression of the spinal cord will compress the pelvic limb tracts first causing UMN signs to the pelvic limbs, while still having normal thoracic limbs. As the compression worsens, the thoracic limb LMNs are affected leading to LMN signs in the thoracic limbs as well. Cervical discomfort/rigidity is often present to help distinguish C6-T2 signs from a T3-L3 lesion.

Common clinical signs of cervicothoracic (C6-T2) myelopathy

  • Weakness/paralysis or ataxia in all 4 limbs (tetraparesis/tetraplegia), ipsilateral limbs (hemiparesis/hemiplegia) or only one thoracic limb (monoparesis/monoplegia)
  • Decreased myotatic & withdrawal reflexes in thoracic limbs
  • Normal to exaggerated myotatic & withdrawal reflexes in pelvic limbs
  • Postural reaction deficits in thoracic and pelvic limbs
  • Early denervation atrophy of thoracic limb(s) and late onset disuse muscle atrophy in pelvic limbs
  • +/- Cervical pain, muscle spasms, rigidity
  • +/- Root signature
  • +/- Decreased or absent cutaneous trunci
  • +/- UMN bladder
  • +/- Respiratory difficulty (LMN dysfunction to phrenic and UMN to intercostal nerves
  • +/- Horner Syndrome (1st order sympathetic neurons)

Case example of a Beagle with a C6-T2 spinal cord disorder from a C6-7 intervertebral disc extrusion.