Question 8

College Answer

The clinical condition that results from this lesion is the so called Brown-Sequard syndrome.
However only a very small proportion of points were given to mention of the latter, with the
majority of points allocated to knowledge relating to spinal cord anatomy and physiology.
The expected 4 main clinical features that are associated with this lesion are -
1. There is loss of pain and temperature sensation on the contralateral side below the level of
the lesion due to interruption of ascending fibres in the crossed lateral spinothalamic tract.
2. There is loss of vibration, joint position and 2 point discrimination on the ipsilateral side
below the level of the lesion due to interruption of ascending fibres in the posterior [dorsal]
columns.
3. There is paralysis of voluntary movement on the ipsilateral side below the level of the
lesion due to interruption of descending fibres in the lateral corticospinal [pyramidal] tracts.
Initially the paralysis is flaccid, later it becomes hypertonic and hyperreflexic with extensor
plantar response [upper motor neurone lesion].
4. Finally there is segmental anaesthesia of the dermatome at the level of the lesion on the
ipsilateral side due to damage of the nerve roots and anterior horn cells at this level.
Some candidates described the clinical features of complete section of the spinal cord which
was not asked for.

Discussion

You could organise this answer in a couple of different ways. Separating things into motor sensory and autonomic seemed like the most sensible breakdown, with each category further split into "ipsi" and "contra". The exam candidate is warned against trying to draw a diagram of the spinal cord here, as it is likely to produce confusion and consume precious minutes. It should be possible to describe the main features of cord hemisection in point form.

• Damaged motor tracts and their effects:
  • Ipsilateral deficits:
    • Ipsilateral segmental loss of all motor function and flaccid paralysis at the dermatomal level of the injury due to the destruction of anterior and posterior horn cell bodies
    • Ipsilateral loss of all motor function and spasticity (later) below the dermatomal level of the injury (corticospinal, rubrospinal, reticulospinal tracts are severed)
• Damaged sensory tracts and their effects:
  • Ipsilateral deficits:
    • Ipsilateral segmental loss of all sensation at the dermatomal level of the injury due to the destruction of anterior and posterior horn cell bodies
    • Ipsilateral loss of light touch, vibration sense and proprioception below the level of the lesion (dorsal column tracts)
  • Contralateral deficits:
    • Contralateral loss of pain and temperature sensation, beginning a few levels below the lesion (spinothalamic tracts)
• Effect of damage to autonomic white matter tracts:
  • Ipsilateral loss of autonomic innervation below the level of the lesion
  • Ipsilateral Horner's syndrome (if the lesion is above T1)

Kunam, Vamsi K., et al. "Incomplete cord syndromes: clinical and imaging review." Radiographics 38.4 (2018): 1201-1222.

Diaz, Eric, and Humberto Morales. "Spinal cord anatomy and clinical syndromes." Seminars in Ultrasound, CT and MRI. Vol. 37. No. 5. WB Saunders, 2016.