Which neurological disorder is characterized by both upper and lower motor neuron signs?

Amyotrophic Lateral Sclerosis (ALS) is the correct choice because it is a progressive neurological disease that affects both upper and lower motor neurons. Upper motor neurons are located in the brain and send signals to the lower motor neurons in the spinal cord, which then transmit signals to the muscles. In ALS, degeneration of both types of neurons occurs, leading to muscle weakness, atrophy, spasticity, and a variety of movement difficulties.

The presence of both upper and lower motor neuron signs is distinctive in ALS. Upper motor neuron signs include increased reflexes and spasticity, while lower motor neuron signs include muscle weakness and atrophy. This combination helps clinicians in diagnosing ALS and is a key characteristic that distinguishes it from other neurological disorders.

In contrast, Guillain-Barré Syndrome primarily affects the peripheral nervous system's lower motor neurons without typical upper motor neuron involvement. Multiple Sclerosis involves demyelination that affects upper motor neurons but does not typically include lower motor neuron damage. Myasthenia Gravis is characterized by a problem at the neuromuscular junction, primarily affecting lower motor neurons without direct upper motor neuron involvement. Thus, ALS is unique in its simultaneous impact on both types of motor neurons.