THE PLANTAR REFLEX - RePub

showed very little agreement with themselves with regard to the interpretation
of the identical films (only slightly better than was to be expected by
chance alone). Added to this there was a considerable disagreement
between observers.
The effect of bias was investigated in the remaining twenty neurologists,
who rated each film after seeing a slide with a fictitious abstract of history
and examination (minus the plantar reflex); the films that occurred twice
were on each occasion preceded by different information, with opposite
bias as to the probability of a Babinski sign. The mean interpretation of
these identical pictures differed significantly, conforming to the information
given; the former group of neurologists) without prior information,
showed no such systematical change of opinion.
It follows that current interpretation of plantar reflexes is, at least in
some cases, a matter of hazard and prejudice, even when differences in
technique are eliminated. Better criteria are obviously needed.
Chapter III describes an electromyographic study of the normal and
pathological plantar reflex, as a reference for equivocal cases. In 22
patients with a definite Babinski sign and in 49 control subjects, the
electrical activity was recorded from flexor and extensor muscles of the
great toe and from the anterior tibial muscle. Mechanical and electrical
stimulation of the sole was used in each. The Babinski sign was found to be
mediated by the extensor hallucis longus, and was always accompanied by
reflex activity in the tibialis anterior. The normal plantar response is the
result of contraction of the flexor hallucis brevis muscle.
Electrical stimulation of the sole was found to activate the extensor
hallucis longus in many control subjects - this had previously led to the
mistaken idea that the extensor hallucis brevis was the effector of the
Babinski sign. Conversely, electrical stimuli failed to recruit the extensor
hallucis longus in some patients with a Babinski sign. In general, reflex
effects produced by the application of short pulse trains to the skin should
be interpreted with caution - not so much because electrical stimuli are
'unnatural', but because they are punctate, as opposed to moving stimuli
which generate spatial and temporal summation of afferent impulses. The
fact that a stimulus is painful is not in itself sufficient to evoke a possible
Babinski sign; neither is a stimulus which causes a Babinski sign always
painful in an average subject.
In Chapter IV the electromyographic criteria for normal and pathological
plantar reflexes, developed in the preceding chapter, were applied to
thirty patients in whom others found equivocal plantar responses. Bias in
recording or interpretation was excluded. The study was repeated in each
patient after one week, and the electromyographic outcome - considered
in terms of 'pathological' or 'not pathological' - was reproducible in 26
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