Final answer:
Proprioception defect pertains to sensory deficits involving the dorsal column, conveying fine touch and proprioception, whereas pyramidal tract diseases involve motor pathways. Pain perception is maintained in a paralyzed leg if the spinothalamic pathway is intact. The Romberg test is used to assess proprioception deficits which can be indicative of dorsal column pathway damage.
Step-by-step explanation:
To differentiate between a proprioception defect and a pyramidal tract disease, we consider the sensory and motor pathways affected. With a pyramidal tract disease, motor symptoms predominate, usually manifested as spastic paralysis. Conversely, proprioceptive defects involve sensory pathways, particularly the dorsal column, which conveys fine touch, vibration, and proprioceptive information.
As per the given information, on the paralyzed leg, a patient may sense pain (due to the intact spinothalamic pathway which crosses immediately upon entering the spinal cord), but not fine touch or proprioceptive sensations (due to the ipsilateral damage of the dorsal column pathway). This observation is indicative of a hemisection of the spinal cord, which might affect the dorsal columns and corticospinal tracts on the same side, suggesting a condition known as Brown-Séquard syndrome.
The Romberg test specifically assesses the dorsal column pathway's proprioception by testing the patient's balance without visual input. Damage to the dorsal column or spinocerebellar tracts can thereby be detected using this method.