SUBJECTIVE NATURE
OF
LOWER LIMB RADICULAR PAIN
Geoffrey M. Bove, DC, PhD, Asia Zaheen, MD, and Zahid H. Bajwa, MD
ABSTRACT
Background: Lumbar pathologies may cause the perception of leg pain, but the character of this pain has not been
described. Diagnosis is often based on dermatomal charts, but observations reveal that the pain is not typically perceived
on the skin.
Objective: To document the incidence of superficial versus deep pain localization among patients with lumbar
radicular pain.
Methods: Twenty-five patients with lower limb radicular pain were questioned to determine the specific localization of
their pain. The investigator categorized the pain location into general areas (eg, posterior thigh or anterior leg). Patients
were asked if their pain was perceived as being on the skin or deep, as a forced choice question. These data were gathered
in 2 conditions: at rest (spontaneous pain) and during a straight leg raise test (mechanically evoked pain). Data were
recorded using a standardized form for later analysis.
Results: In all cases, symptoms were reported to be in deep structures. Pain was typically reported at sites correlated with
multiple spinal levels.
Conclusion: Because radicular pain symptoms are perceived in deep structures rather than on the skin, the diagnostic
value of dermatomal charts is questioned. Clinicians are advised to be specific when questioning patients with radicular
pain symptoms and to refer to myotomal and sclerotomal charts when making diagnoses. (J Manipulative Physiol Ther
2005;28:12-14)
Key Indexing Terms: Pain; Sciatic Neuropathy; Straight Leg Raise
A
fundamental characteristic of radiating pain is that
it is perceived in a different location than the
causative lesion. The best-known example of
radiating pain is the lower extremity pain associated with
lumbar disk disease and known as bsciatica,Q which affects
up to 40% of the adult population.1 Despite the prevalence of
such painful conditions, the localization of pain has rarely
been described, especially in terms of bdeepQ versus
bsuperficial.Q Because the myotomal and sclerotomal (deep)
and dermatomal (superficial) innervation patterns are dissimilar, the clinical interpretation of symptoms may be
dependent on this sort of localization. The primary goal of
this study was to determine whether lower limb radicular
pain is perceived by patients to be deep or superficial. To this
end, we questioned patients presenting to our pain clinic with
Beth Israel Deaconess Medical Center and Harvard Medical
School, Boston, MA.
Submit requests for reprints to: Dr. Geoffrey M. Bove, DC,
PhD, Beth Israel Deaconess Medical Center, Department of
Anesthesia and Critical Care, 330 Brookline Avenue, Dana 721,
Boston, MA 02215 (e-mail: gbove@bidmc.harvard.edu).
Paper submitted June 16, 2003; in revised form October 10,
2003.
0161-4754/$30.00
Copyright D 2005 by National University of Health Sciences.
doi:10.1016/j.jmpt.2004.12.011
12
diagnoses of lumbar radiculopathy about the localization of
their spontaneous and mechanically evoked leg pain.
METHODS
The Beth Israel Deaconess Medical Center Committee on
Clinical Investigation approved this protocol. All data
collection was performed by one of the authors (AZ), who
was unaware of the main hypothesis of the study. The
records of scheduled patients aged 25 to 65 years were
checked for diagnoses of lumbar radiculopathy. Before their
scheduled examination, such patients were invited and gave
verbal consent to participate.
While lying supine on the examination table, the
investigator asked the patients about the pain they were
currently perceiving (spontaneous pain), using a standardized script. Patients were not asked to provide pain
descriptors, nor were such descriptors recorded. They were
asked to localize their symptoms as specifically as possible.
The investigator categorized the location of symptoms as
anterior, posterior, medial, and/or lateral for the buttocks,
thigh, knee, leg, and/or foot. For each region where pain
was reported, patients were also asked if the pain was
perceived bon the skinQ or bdeep,Q using these standard
terms. All data were recorded on a standardized form.
A straight leg raise (SLR) test was then performed, and
the approximate angle at which symptoms appeared was
Journal of Manipulative and Physiological Therapeutics
Volume 28, Number 1
Bove et al
Lower Limb Radicular Pain
Table 1. Reports of spontaneous and evoked pain from all legs and correlating root levels
Spontaneous pain
Evoked pain
Spinal level
Case
Glut
Thigh
Knee
Leg
Foot
Glut
Thigh
Knee
Leg
Foot
L2
L3
L4
L5
S1
S2
6
3
5
4
23
24
20
29
8
11
27
10
2
7
22
16
25
28
1
9
26
17
18
12
13
14
15
19
21
p
pl
pl
pl
pl
pl
p
l
pl
pl
p
pl
p
p
p
p
p
p
p
pl
pl
apml
pl
pl
pl
p
p
p
l
apml
apml
apml
pl
al
pl
p
pl
p
p
l
pl
apml
pl
pl
pl
p
p
p
l
apml
apml
apml
pl
al
pl
p
pl
p
p
l
apml
pl
pl
pl
p
p
p
l
apml
apml
apml
pl
al
pl
p
apml
l
p
a
p
p
p
al
pl
pl
apml
pl
pl
apml
p
p
apml
apml
se
se
se
se
se
se
e
e
e
se
se
s
se
s
s
se
se
se
s
se
se
se
s
se
s
s
se
s
s
e
s
e
s
se
se
s
se
se
se
s
se
s
s
se
se
e
s
s
se
se
s
se
s
s
s
se
se
se
se
se
se
s
se
s
se
s
s
se
se
se
se
se
s
s
s
se
s
s
s
apml
apml
a
a
a
a
apml
apml
a
a
a
a
apml
apml
a
a
a
a
pl
p
pl
p
ap
p
pl
a
p
ap
p
a
p
a
p
p
p
pl
a
a
a
l
pl
pl
p
p
pl
pl
pl
al
apml
p
p
apml
l
pl
al
pl
al
e
e
p
p
a
a
a
a
s
s
s
se
se
se
se
s
s
s
se
se
se
se
a
l
p
p
a
a
a
a
p
a
a
a
pm
p
a
s
s
se
se
se
se
e
s
s
s
s
se
se
se
se
s
s
se
se
se
se
se
Cases were arranged by the relative extent of the spontaneous pain symptoms. Glut, Gluteal; a, anterior; p, posterior; m, medial; l, lateral.
s, Spontaneous; e, evoked symptom in location consistent with listed nerve root, from myotomal chart.2
recorded. The subjective reports of the patients to the same
questions about pain localization during this test were
recorded. Ankle dorsiflexion was then performed, and
patients were asked if this worsened their pain. The
responses were summarized in chart format.
RESULTS
Subjective pain perceptions from 19 right and 10 left legs
of 25 patients were recorded (Table 1) from the 25
sequential patients who were asked to participate. All 29
legs were reported to generate spontaneous pain. In all
cases, the pain was reported to be deep, not superficial.
Straight leg raising evoked pain in 24 (83%) legs, at a mean
level of 588 (SD 16.7). Evoked pain was also reported to be
deep in all cases. Ankle dorsiflexion aggravated the
symptoms in 20 (83%) of these legs. The 95% exact
binomial confidence interval for both spontaneous and
evoked superficial pain being reported in 0 of 29 cases is
0 to 0.12; in other words, the prevalence of superficial pain
probably lies, in either case, between 0% and 12%.
The regions of spontaneous pain were compared with
myotomal charts of the lower limb, 2 and the corresponding
root levels were recorded. In all but 1 case, multiple roots
seemed affected. In only 1 case did symptoms in the
distribution of multiple roots bskipQ any level. In the majority
of cases, the regions and spinal levels of evoked pain were
either the same or were a subset of the areas of spontaneous
pain (Table 1). In 2 cases, the evoked symptoms were
more widespread than the spontaneous symptoms. Eleven
patients reported spontaneous anterior thigh and/or knee
pain, and in 2 different cases, evoked pain was reported in
these areas, indicating L2 and/or L3 involvement.
DISCUSSION
The most striking finding in this study was that in all
cases, the spontaneous and evoked pains were reported as
deep rather than superficial. This contrasts to previous
reports that 22% of patients with radicular symptoms had
superficially perceived spontaneous leg pain.3,4 The principal difference may be that the cited reports examined cases
13
14
Bove et al
Lower Limb Radicular Pain
in which surgery had been or would be performed, whereas
our patients were mainly referred to the pain clinic as
nonsurgical candidates. In addition, the cited authors
attributed superficial symptoms to more severe nerve
involvement, which is a distinct possibility.
The difference between deep versus superficial pain has
clinical and biologic implications. Clinically, spontaneous
pain and the SLR test are used to help diagnose which nerve
roots are involved in a radiculopathy. The symptoms are
often compared with dermatomal charts. However, in the
absence of reports of spontaneous or SLR-evoked cutaneous
pain, dermatomal charts are clearly not the ideal diagnostic
reference. These data suggest that myotomal and sclerotomal charts2 have more diagnostic potential.
On the other hand, the data may indicate that pain
symptoms have limited diagnostic utility, especially considering that pain was reported correlating to multiple levels in
almost all cases. Biologically, these data imply fundamental
differences within primary afferent nociceptive neurons. The
neurons innervating musculoskeletal structures may respond
differently to pathologic lesions that cause radicular symptoms from the neurons innervating cutaneous structures.
These ideas are consistent with recent reports that intact
afferent neurons innervating muscle develop spontaneous
activity after nerve injury, 5 whereas cutaneous neurons do
not. This could explain deep spontaneous pain after nerve
injury. Also, the axons of deep but not cutaneous afferent
neurons develop spontaneous activity and more importantly
mechanical sensitivity during neuritis.6 This provides a
potential mechanism for both spontaneous and mechanically
evoked pain perceived as bdeep.Q
There was a distinct difference between the number of
spinal levels involved in spontaneous pain compared with
evoked pain. We hypothesize that this reflects different
mechanisms for spontaneous versus evoked pain and that
both could be explained by changes affecting primary
afferent nociceptors. Although little data exist to support
such hypotheses, our previous report showed that when
axons are inflamed, some nociceptive neurons spontaneously generate action potentials (could lead to spontaneous
pain), whereas others become mechanically sensitive (could
lead to evoked pain).6 The present observations could be
caused by such basic neurophysiological differences.
The apparently multiple spinal level involvement of the
symptoms and the different distributions of spontaneous and
evoked pain are not consistent with commonly held
Journal of Manipulative and Physiological Therapeutics
January 2005
concepts of focal pathologies (eg, discal herniation).
However, autologous nucleus pulposus from a compromised
intervertebral disk is known to cause intrathecal inflammation7,8 that would not be expected to be restricted by nerve
root levels, but rather by the spread of the intradiscal
material. The extent of radicular symptoms, assessed by the
number of spinal levels involved, may be related to the
extent of inflammation and may be a measure of severity.
However, there is a confounder in the concept of nonspecific extension of inflammation to other spinal levels as a
cause of the symptoms reported: there were no reports of
contralateral symptoms. We have no hypothesis to offer as
explanation for this.
CONCLUSION
This project indicates that questions regarding bvolume,Q
in addition to area of pain, give qualitatively different
diagnostic information. Future comparisons of symptoms,
physical findings, and imaging will be necessary to clarify
the significance of such symptoms and whether they impact
clinical decision making.
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