A cat shows upper motor neuron signs in the forelimbs and lower motor neuron signs in the hind limbs. The most likely lesion location is which spinal segment range?

A cat shows upper motor neuron signs in the forelimbs and lower motor neuron signs in the hind limbs. The most likely lesion location is which spinal segment range?

• A. C1-C5
• B. C5-T2
• C. T3-L3
• D. L4-S2

Answer: (B)

The main idea is localizing a spinal cord lesion based on the pattern of motor signs in the limbs. Forelimb signs that are characteristic of an upper motor neuron lesion mean disruption of descending motor tracts before they reach the forelimb motor neurons, which reside in the cervical enlargement. Hindlimb signs that look like lower motor neuron involvement point to damage to the hindlimb motor neuron pool itself, which is in the lumbar to sacral enlargement. Putting those clues together, the lesion must lie at a region where the descending pathways to the forelimb are interrupted while the hindlimb motor neuron circuitry is also affected at that same general level—namely the cervicothoracic spinal cord. This location best explains seeing upper motor neuron signs in the forelimbs and lower motor neuron signs in the hindlimbs.

The main idea is localizing a spinal cord lesion based on the pattern of motor signs in the limbs. Forelimb signs that are characteristic of an upper motor neuron lesion mean disruption of descending motor tracts before they reach the forelimb motor neurons, which reside in the cervical enlargement. Hindlimb signs that look like lower motor neuron involvement point to damage to the hindlimb motor neuron pool itself, which is in the lumbar to sacral enlargement.

Putting those clues together, the lesion must lie at a region where the descending pathways to the forelimb are interrupted while the hindlimb motor neuron circuitry is also affected at that same general level—namely the cervicothoracic spinal cord. This location best explains seeing upper motor neuron signs in the forelimbs and lower motor neuron signs in the hindlimbs.