The Babinski sign can indicate upper motor neuron lesion constituting damage to the corticospinal tract. Occasionally, a pathological plantar reflex is the first and only indication of a serious disease process and a clearly abnormal plantar reflex often prompts detailed neurological investigations, including CT scanning of the brain or MRI of the spine, as well as lumbar puncture for the study of cerebrospinal fluid.
The phrase "negative Babinski sign" is sometimes used for the normal flexor plantar response