Amyotrophic lateral sclerosis usually starts subtly.
 While PMA is associated with longer survival on average than classic ALS, it still progresses to other spinal cord regions over time, eventually leading to respiratory failure and death
== Pathophysiology ===== Neuropathology ===The defining feature of ALS is the death of both upper motor neurons (located in the motor cortex of the brain) and lower motor neurons (located in the brainstem and spinal cord)

