From the Research
The Babinski test is a valuable neurological examination for evaluating the integrity of the corticospinal tract, but its reliability and validity are variable, and it should be used in conjunction with other tests such as finger and foot tapping for accurate diagnosis of corticospinal tract lesions. The Babinski test is performed by stroking the sole of the foot and observing the toe response, with a positive sign indicating upper motor neuron damage. In normal adults, the toes curl downward (plantar flexion), which is a negative Babinski sign, while a positive Babinski sign occurs when the great toe extends upward with or without fanning of the other toes. This test is particularly valuable in diagnosing conditions affecting the pyramidal tract such as stroke, multiple sclerosis, spinal cord injury, or brain tumors 1.
To perform the test correctly, use a moderately sharp object like a tongue depressor or reflex hammer handle to stroke the lateral aspect of the sole from the heel toward the ball of the foot in a smooth, continuous motion. The pressure should be firm enough to elicit a response but not cause pain. It's essential to note that a positive Babinski sign is normal in infants up to about 2 years of age due to incomplete myelination of the corticospinal tracts. The test should be interpreted in the context of the patient's complete neurological examination and clinical presentation, as it represents just one component of a comprehensive neurological assessment.
Some key points to consider when interpreting the Babinski test include:
- The sensitivity and specificity of the Babinski sign can vary, with a study finding an overall sensitivity of 49.6% and specificity of 85.8% 1.
- The interobserver agreement between medical students and neurologists was greater for finger and foot tapping (Kappa = 0.83) when compared to Babinski sign (Kappa = 0.45) 1.
- Finger and foot tapping is a valid and reliable test in the clinical diagnosis of corticospinal lesions, with an overall sensitivity of 79.5% and specificity of 88.4% 1.
- The patterns of Babinski sign can be used to predict cortical lesions of the pyramidal tract, with dorsiflexion of the big toe without recruitment of the other toes seen in 71.4% of patients with cortical pyramidal tract lesions 2.
Overall, while the Babinski test is a useful tool in neurological examination, its limitations and variability should be considered, and it should be used in conjunction with other tests and clinical evaluation for accurate diagnosis and management of patients with suspected neurological disorders.