In the described neurological exam, dorsiflexion of the big toe after stroking the lateral sole indicates which sign?

In the described neurological exam, dorsiflexion of the big toe after stroking the lateral sole indicates which sign?

• A. Kernig's sign
• B. Babinski's sign
• C. Brudzinski's sign
• D. Nuchal rigidity sign

Answer: (B)

The sign being described is the Babinski sign. Stroking the lateral sole elicits a distinctive plantar reflex: in a normal adult the toes curl downward (plantar flexion). If the big toe dorsiflexes and the other toes fan out, that upward movement of the big toe and toe spreading is considered a positive Babinski sign. This occurs because an adult’s corticospinal (pyramidal) tract normally exerts inhibitory control over the spinal reflexes that cause toe extension. When there’s an upper motor neuron lesion affecting the corticospinal pathway—such as from a stroke, multiple sclerosis, trauma, or other brain/spinal cord injuries—this inhibition is lost, producing the extensor plantar response. It’s helpful to distinguish this from signs of meningeal irritation, which are unrelated to the plantar reflex: Kernig’s and Brudzinski’s signs involve pain or movement abnormalities with neck or leg maneuvers due to meningitis or meningeal irritation, while nuchal rigidity refers to neck stiffness.

The sign being described is the Babinski sign. Stroking the lateral sole elicits a distinctive plantar reflex: in a normal adult the toes curl downward (plantar flexion). If the big toe dorsiflexes and the other toes fan out, that upward movement of the big toe and toe spreading is considered a positive Babinski sign.

This occurs because an adult’s corticospinal (pyramidal) tract normally exerts inhibitory control over the spinal reflexes that cause toe extension. When there’s an upper motor neuron lesion affecting the corticospinal pathway—such as from a stroke, multiple sclerosis, trauma, or other brain/spinal cord injuries—this inhibition is lost, producing the extensor plantar response.

It’s helpful to distinguish this from signs of meningeal irritation, which are unrelated to the plantar reflex: Kernig’s and Brudzinski’s signs involve pain or movement abnormalities with neck or leg maneuvers due to meningitis or meningeal irritation, while nuchal rigidity refers to neck stiffness.