Primary lateral sclerosis is described as?

Primary lateral sclerosis is described as?

• A. A disease affecting lower motor neurons only.
• B. A very rare motor neuron disease involving upper motor neurons only, leading to slow progression and upper motor neuron signs.
• C. Demyelinating disease of peripheral nerves.
• D. A condition causing cognitive decline without motor symptoms.

Answer: (B)

Primary lateral sclerosis is a rare motor neuron disorder that affects the upper motor neurons in the brain and corticospinal pathways. Because it targets upper motor neurons, the main signs are upper motor neuron features—spasticity, increased reflexes, and a positive Babinski sign—with a slow, gradual progression. It typically spares lower motor neurons initially, which helps distinguish it from conditions like ALS that involve both upper and lower motor neurons. It isn’t a peripheral demyelinating disease, which would present with different nerve involvement and sometimes sensory symptoms, nor is it a cognitive disorder without motor symptoms. The description that emphasizes involvement of upper motor neurons only, along with slow progression and upper motor neuron signs, best fits primary lateral sclerosis.

Primary lateral sclerosis is a rare motor neuron disorder that affects the upper motor neurons in the brain and corticospinal pathways. Because it targets upper motor neurons, the main signs are upper motor neuron features—spasticity, increased reflexes, and a positive Babinski sign—with a slow, gradual progression. It typically spares lower motor neurons initially, which helps distinguish it from conditions like ALS that involve both upper and lower motor neurons. It isn’t a peripheral demyelinating disease, which would present with different nerve involvement and sometimes sensory symptoms, nor is it a cognitive disorder without motor symptoms. The description that emphasizes involvement of upper motor neurons only, along with slow progression and upper motor neuron signs, best fits primary lateral sclerosis.