Babinski sign for upper motor neuron weakness is of low reliability

To identify the reliability and validity of the Babinski sign in the routine neurological examination., researchers at the University of California performed a study of ten physicians (five neurologists and five non-specialists) who examined each foot of 10 subjects, 8 of whom had known unilateral upper motor neuron weakness, 1 had bilateral leg weakness secondary to ALS, and 1 had no known neurologic deficits. They compared the Babinski sign against a less well-known sign of upper motor neuron dysfunction, decreased speed of foot tapping. The main outcome measures were inter-rater reliability (kappa values) and accuracy (agreement with known upper motor neuron weakness).

They found "The reliability of the Babinski sign was fair (kappa 0.30) and was substantial for foot tapping (kappa 0.73). Agreement with known weakness was 56% for Babinski sign and 85% for foot tapping. Reliability and accuracy for both tests were similar for neurologists and non-specialists."

The researchers concluded "The interobserver reliability and validity of the Babinski sign for identifying upper motor neuron weakness are limited. Slowness of foot tapping may be a more useful sign."

Neurology 2005;65:1165-1168 25 October 2005. © 2005 American Academy of Neurology
Should the Babinski sign be part of the routine neurologic examination? Timothy M. Miller, MD, PhD and S. Claiborne Johnston, MD, PhD. Correspondence to Dr. S. Claiborne Johnston clay.johnston@ucsfmedctr.org

Category N. Neurological. Keywords: Babinski sign, neurological examination, upper motor neuron, weakness, foot tapping, observational study
Synopsis edited by Dr Jim Vause, Blenheim, New Zealand. Posted on Global Family Doctor 8 November 2005