Authors: Campbell, William W.
Title: Pocket Guide and Toolkit to DeJong’s Neurologic Examination, 1st Edition
Copyright ©2008 Lippincott Williams & Wilkins
> Table of Contents > Section G – The Reflexes > Chapter 29 – The Superficial (Cutaneous) Reflexes
Chapter 29
The Superficial (Cutaneous) Reflexes
Superficial reflexes are
responses to stimulation of either the skin or mucous membrane.
Cutaneous reflexes are elicited by a superficial skin stimulus, such as
a light touch or scratch. The response occurs in the same general area
where the stimulus is applied. Too painful a stimulus may call forth a
defensive reaction rather than the desired reflex. Superficial reflexes
are polysynaptic, in contrast to the stretch reflexes, which are
monosynaptic. The superficial reflexes respond more slowly to the
stimulus than do the stretch reflexes, their latency is longer, they
fatigue more easily, and they are not as consistently present as tendon
reflexes. The primary utility of superficial reflexes is that they are
abolished by pyramidal tract lesions, which characteristically produce
the combination of increased deep tendon reflexes and decreased or
absent superficial reflexes. The superficial reflexes obtained most
often are the abdominal and cremasteric. Unilateral absence of the
superficial abdominal reflexes may be an early and sensitive indicator
of a corticospinal tract lesion.
responses to stimulation of either the skin or mucous membrane.
Cutaneous reflexes are elicited by a superficial skin stimulus, such as
a light touch or scratch. The response occurs in the same general area
where the stimulus is applied. Too painful a stimulus may call forth a
defensive reaction rather than the desired reflex. Superficial reflexes
are polysynaptic, in contrast to the stretch reflexes, which are
monosynaptic. The superficial reflexes respond more slowly to the
stimulus than do the stretch reflexes, their latency is longer, they
fatigue more easily, and they are not as consistently present as tendon
reflexes. The primary utility of superficial reflexes is that they are
abolished by pyramidal tract lesions, which characteristically produce
the combination of increased deep tendon reflexes and decreased or
absent superficial reflexes. The superficial reflexes obtained most
often are the abdominal and cremasteric. Unilateral absence of the
superficial abdominal reflexes may be an early and sensitive indicator
of a corticospinal tract lesion.
THE SUPERFICIAL ABDOMINAL REFLEXES
The superficial abdominal reflexes consist of
contraction of the abdominal muscles, elicited by a light stroke or
scratch of the anterior abdominal wall, pulling the linea alba and
umbilicus in the direction of the stimulus (Figure 29.1).
The response can be divided into the upper abdominal and lower
abdominal reflexes. The anterior abdominal wall can be divided into
four quadrants by vertical and horizontal lines through the umbilicus.
Light stroking or scratching in each quadrant elicits the response,
pulling the umbilicus in the direction of the stimulus. The stimulus
may be directed toward, away, or parallel to the umbilicus; stimuli
directed toward the umbilicus seem more effective. The response is a
quick, flicking contraction followed by immediate relaxation. The
responses are typically brisk and active in young individuals with good
anterior abdominal tone. They may be sluggish or absent in normal
individuals with lax abdominal tone, in those who are obese, or in
women who have borne children.
contraction of the abdominal muscles, elicited by a light stroke or
scratch of the anterior abdominal wall, pulling the linea alba and
umbilicus in the direction of the stimulus (Figure 29.1).
The response can be divided into the upper abdominal and lower
abdominal reflexes. The anterior abdominal wall can be divided into
four quadrants by vertical and horizontal lines through the umbilicus.
Light stroking or scratching in each quadrant elicits the response,
pulling the umbilicus in the direction of the stimulus. The stimulus
may be directed toward, away, or parallel to the umbilicus; stimuli
directed toward the umbilicus seem more effective. The response is a
quick, flicking contraction followed by immediate relaxation. The
responses are typically brisk and active in young individuals with good
anterior abdominal tone. They may be sluggish or absent in normal
individuals with lax abdominal tone, in those who are obese, or in
women who have borne children.
THE SUPERFICIAL REFLEXES OF THE LOWER EXTREMITIES
The Cremasteric Reflex
This reflex is elicited by stroking or lightly
scratching or pinching the skin on the upper, inner aspect of the
thigh. The response consists of a contraction of the cremasteric muscle
with a quick elevation of the homolateral testicle. The innervation is
through the ilioinguinal and genitofemoral nerves (L1-L2). The
cremasteric reflex must not be confused with the scrotal, or dartos,
reflex,
scratching or pinching the skin on the upper, inner aspect of the
thigh. The response consists of a contraction of the cremasteric muscle
with a quick elevation of the homolateral testicle. The innervation is
through the ilioinguinal and genitofemoral nerves (L1-L2). The
cremasteric reflex must not be confused with the scrotal, or dartos,
reflex,
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which
produces a slow, writhing, vermicular contraction of the scrotal skin
on stroking the perineum or thigh or applying a cold object to the
scrotum. The cremasteric reflex may be absent in elderly males, in
individuals who have a hydrocele or varicocele, and in those who have
had orchitis or epididymitis. There is no female equivalent.
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FIGURE 29.1 • Sites of stimulation employed in eliciting the various superficial abdominal reflexes.
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The Plantar Reflex
Stroking the plantar surface of the foot from the heel forward is normally followed by plantar flexion of the foot and toes (Figure 29.2).
The pathologic variation of the plantar reflex is the Babinski sign. In
ticklish patients there may be voluntary withdrawal with flexion of the
hip and knee, but in every normal individual there is a certain amount
of plantar flexion of the toes on stimulation of the sole of the foot.
The pathologic variation of the plantar reflex is the Babinski sign. In
ticklish patients there may be voluntary withdrawal with flexion of the
hip and knee, but in every normal individual there is a certain amount
of plantar flexion of the toes on stimulation of the sole of the foot.
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FIGURE 29.2 • Method of obtaining the plantar reflex.
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The Superficial Anal Reflex
The cutaneous anal reflex (anal wink) consists of
contraction of the external sphincter in response to stroking or
pricking the skin or mucous membrane in the perianal region.
contraction of the external sphincter in response to stroking or
pricking the skin or mucous membrane in the perianal region.
Bulbocavernosus Reflex
The bulbocavernosus reflex (BCR) is related to the anal
reflex in that both cause contraction of the anal sphincter, but in the
BCR, the stimulus is delivered to the glans penis or clitoris. The
response is best palpated with a gloved finger in the rectum. Some
forewarning and preliminary explanation are necessary, but the stimulus
should still come as a surprise. In the male, a grabbing, pinching, or
tweaking of the glans evokes the response, felt as a tightening of the
sphincter on the finger. The response is much more difficult to elicit
in females and the significance of its absence more dubious. The BCR is
primarily useful is assessing the integrity of the cauda equina, lower
sacral roots, and conus medullaris.
reflex in that both cause contraction of the anal sphincter, but in the
BCR, the stimulus is delivered to the glans penis or clitoris. The
response is best palpated with a gloved finger in the rectum. Some
forewarning and preliminary explanation are necessary, but the stimulus
should still come as a surprise. In the male, a grabbing, pinching, or
tweaking of the glans evokes the response, felt as a tightening of the
sphincter on the finger. The response is much more difficult to elicit
in females and the significance of its absence more dubious. The BCR is
primarily useful is assessing the integrity of the cauda equina, lower
sacral roots, and conus medullaris.
ABNORMALITIES OF THE SUPERFICIAL REFLEXES
The effect on the superficial reflexes of lesions at various sites is summarized in Table 28.3.
The superficial reflexes are impaired or absent with a lesion that
disturbs the continuity of the reflex arc. In addition, a lesion
anywhere along the corticospinal pathway will usually cause either
diminution or absence of the superficial reflexes. The reflex change is
contralateral to a lesion above the pyramidal decussation, and
ipsilateral to a lesion below the pyramidal decussation. Corticospinal
tract disease causes dissociation of reflexes, absence of superficial
reflexes, and exaggerated deep reflexes. So the superficial reflexes,
especially the abdominal and cremasteric reflexes, have a special
significance when their absence is associated with increased deep
tendon reflexes or when they are absent when signs of corticospinal
tract involvement are present. The abdominal and the cremasteric
reflexes may occasionally be absent in persons without other evidence
of neurologic disease.
The superficial reflexes are impaired or absent with a lesion that
disturbs the continuity of the reflex arc. In addition, a lesion
anywhere along the corticospinal pathway will usually cause either
diminution or absence of the superficial reflexes. The reflex change is
contralateral to a lesion above the pyramidal decussation, and
ipsilateral to a lesion below the pyramidal decussation. Corticospinal
tract disease causes dissociation of reflexes, absence of superficial
reflexes, and exaggerated deep reflexes. So the superficial reflexes,
especially the abdominal and cremasteric reflexes, have a special
significance when their absence is associated with increased deep
tendon reflexes or when they are absent when signs of corticospinal
tract involvement are present. The abdominal and the cremasteric
reflexes may occasionally be absent in persons without other evidence
of neurologic disease.
The superficial reflexes may help distinguish
physiologic from pathologic hyperreflexia. In physiologic
hyperreflexia, seen most often in young individuals or patients with
anxiety, the abdominal and cremasteric reflexes are usually present and
active, but in pathologic hyperreflexia due to an upper motor neuron
lesion they are usually absent.
physiologic from pathologic hyperreflexia. In physiologic
hyperreflexia, seen most often in young individuals or patients with
anxiety, the abdominal and cremasteric reflexes are usually present and
active, but in pathologic hyperreflexia due to an upper motor neuron
lesion they are usually absent.