Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which neurological condition is characterized by both motor and sensory loss?

1. Multiple sclerosis

2. Brown-Sequard syndrome

3. Parkinson's disease

4. Myasthenia gravis

The correct answer is: Brown-Sequard syndrome

Brown-Sequard syndrome is characterized by a hemisection or injury to one side of the spinal cord, leading to a distinctive pattern of neurological deficits. This condition results in ipsilateral (same side) motor loss due to damage to the corticospinal tract, which impacts voluntary muscle control. Simultaneously, there is contralateral (opposite side) loss of sensory functions such as pain and temperature, attributed to damage in the spinothalamic tract. This unique combination of sensorimotor deficits makes Brown-Sequard syndrome stand out from other neurological conditions, which may predominantly affect either motor or sensory pathways but not typically both in the manners described. In contrast, multiple sclerosis can cause a wide array of neurological symptoms, but the presence of both motor and sensory loss is not as characteristic of any single event within the disease. Parkinson’s disease primarily presents with motor symptoms, like tremors and rigidity, without significant sensory loss. Myasthenia gravis mainly affects neuromuscular transmission, leading to muscle weakness, but does not usually result in sensory loss. Thus, the defining features of Brown-Sequard syndrome make it the prominent answer for a condition that results in both motor and sensory loss.