American Board of Psychiatry and Neurology (ABPN) Practice Exam

A patient involved in a car accident is found on MRI to have a spinal fracture and a partial crush lesion to the cervical spinal cord that effectively causes a functional hemisection of the cord. His deficits would be expected to include:

1. Contralateral loss of motor control and pain and temperature sensation with ipsilateral loss of proprioception and vibration sensation

2. Ipsilateral loss of motor control and pain and temperature sensation with contralateral loss of proprioception and vibration sensation

3. Ipsilateral loss of motor control and proprioception and vibration sensation with contralateral loss of pain and temperature sensation

4. Contralateral loss of motor control and proprioception and vibration sensation with ipsilateral loss of pain and temperature sensation

The correct answer is: Ipsilateral loss of motor control and proprioception and vibration sensation with contralateral loss of pain and temperature sensation

In cases of a spinal cord injury that results in a functional hemisection, known as Brown-Séquard syndrome, specific sensory and motor deficits are observed based on the anatomy and pathways of the nervous system. When a partial crush lesion causes hemisection, the motor pathways that descend from the brain (the corticospinal tract) are affected on the same side as the injury (ipsilateral side), leading to ipsilateral weakness or loss of motor control. This is because these motor fibers decussate (cross over) at the level of the brainstem, so an injury on one side of the spinal cord affects motor function on that same side. Sensory pathways function differently: the dorsal columns, which carry proprioception and vibration sensation, also present this ipsilateral loss. These pathways ascend in the same side of the spinal cord before they decussate (cross over) at the medulla oblongata to reach the thalamus. On the other hand, the spinothalamic tract, which carries pain and temperature sensation, crosses over at the level of the spinal cord soon after entering. Therefore, a hemisection would result in a contralateral loss of these sensations, as the fibers on the opposite side of the