A standardized protocol for needle placement in suboccipital muscles.

Abstract

The objective of this study was to assess the safety and accuracy of using common anatomic landmarks to guide the placement of needle electrodes into suboccipital muscles. Atrophic changes in suboccipital muscles have been reported in some patients who have tension-type headaches, and in some patients who have headaches resulting from whiplash-type injuries. These atrophic changes most likely result from disuse or denervation. Needle electromyography is a definitive technique for determining the cause of muscle atrophy, but requires that needle electrodes be inserted into the muscle. Suboccipital muscles present a challenge to the electromyographer in that they are physically small and are located in close proximity to one another. Atrophied muscles with fatty replacement and the presence of critical structures such as the vertebral artery further complicate the procedure. Using a standardized protocol, three investigators attempted blind needle insertions into each of the suboccipital muscles of eight embalmed cadavers. A dissector then assessed targeted muscle penetrations, final resting positions of the wires, and their proximity to critical structures. Eighty-one percent of 181 attempted insertions penetrated the targeted muscles: 83% for the rectus capitis posterior minor, 83% for the rectus capitis posterior major, 94% for the obliquus capitis superior, and 63% for the obliquus capitis inferior muscles, respectively. It was concluded that readily palpable external landmarks can be used to safely and reliably guide the insertion of needle electrodes into three of the four pairs of suboccipital muscles.

Full text

Page 1

ORIGINAL COMMUNICATION
A Standardized Protocol for Needle Placement
in Suboccipital Muscles
RICHARD C. HALLGREN,1,2*MICHAEL T. ANDARY,2ANDREW J. WYMAN,3
AND JACOB J. ROWAN1
1Department of Osteopathic Manipulative Medicine, College of Osteopathic Medicine,
Michigan State University, East Lansing, Michigan
2Department of Physical Medicine and Rehabilitation, College of Osteopathic Medicine,
Michigan State University, East Lansing, Michigan
3Department of Radiology, Division of Anatomy and Structural Biology, College of Osteopathic Medicine,
Michigan State University, East Lansing, Michigan
The objective of this study was to assess the safety and accuracy of using
common anatomic landmarks to guide the placement of needle electrodes into
suboccipital muscles. Atrophic changes in suboccipital muscles have been
reported in some patients who have tension-type headaches, and in some
patients who have headaches resulting from whiplash-type injuries. These
atrophic changes most likely result from disuse or denervation. Needle electro-
myography is a definitive technique for determining the cause of muscle atro-
phy, but requires that needle electrodes be inserted into the muscle. Subocci-
pital muscles present a challenge to the electromyographer in that they are
physically small and are located in close proximity to one another. Atrophied
muscles with fatty replacement and the presence of critical structures such as
the vertebral artery further complicate the procedure. Using a standardized
protocol, three investigators attempted blind needle insertions into each of the
suboccipital muscles of eight embalmed cadavers. A dissector then assessed
targeted muscle penetrations, final resting positions of the wires, and their
proximity to critical structures. Eighty-one percent of 181 attempted insertions
penetrated the targeted muscles: 83% for the rectus capitis posterior minor,
83% for the rectus capitis posterior major, 94% for the obliquus capitis supe-
rior, and 63% for the obliquus capitis inferior muscles, respectively. It was
concluded that readily palpable external landmarks can be used to safely and
reliably guide the insertion of needle electrodes into three of the four pairs of
suboccipital muscles. Clin. Anat. 21:501–508, 2008.
V V
C2008 Wiley-Liss, Inc.
Keywords: anatomy;
whiplash
electromyography;suboccipital;cervical;muscles;
INTRODUCTION
Head and neck disorders, resulting in head and
neck pain, present some of the most common prob-
lems seen in medical practice. These can be difficult
to treat because the cause of the head and neck pain
is often not evident. Atrophic changes in suboccipital
muscles at the level of spinal segments C1 and C2
have been reported in some patients who have ten-
sion-type headaches (Ferna ´ndez-de-Las Pen ˜as et al.,
*Correspondence to: Richard Hallgren, PhD, Department of Physi-
cal Medicine & Rehabilitation, Michigan State University, East
Lansing, MI 48824, USA. E-mail: hallgren@msu.edu
Grant sponsor: American Osteopathic Association, Chicago, IL;
Grant number: 07-05-554.
Received 23 January 2008; Revised 1 May 2008; Accepted 5
May 2008
Published online 14 July 2008 in Wiley InterScience (www.
interscience.wiley.com). DOI 10.1002/ca.20660
V V
C2008 Wiley-Liss, Inc.
Clinical Anatomy 21:501–508 (2008)

Page 2

2007), and in some patients who have headaches
resulting from whiplash-type injuries (Hallgren et al.,
1994; McPartland et al., 1997; Andary et al., 1998;
Elliott et al., 2006). While it is not clear how atrophic
changes in these muscles might result in head and
neck pain, it may be significant that these two
groups of idiopathic head and neck pain patients
share a common pathology. The functional implica-
tions of atrophic changes in suboccipital muscles are
unknown, but it is suspected that alterations in pro-
prioceptive activity from these muscles may account
for both a decrease in head and neck repositioning
accuracy and changes in head and neck positioning
patterns (Revel et al., 1991; Heikkila and Astrom,
1996; Feipel et al., 2006). Ruling out a primary myo-
pathic disorder, atrophy of suboccipital muscles may
result from inhibition and/or disuse, or they may be
neurogenic in nature. Since there is a significant dif-
ference in these two muscle disorders, it is important
to be able to determine the cause of atrophy. Needle
electromyography (EMG) would enable a physician
to differentiate between these two muscle disorders,
buthasnotbeenroutinely
because of the absence of a standardized protocol
for the safe and reliable insertion of needle electro-
des into suboccipital muscles.
The four suboccipital muscles are the rectus capi-
tis posterior minor (RCPMi), the rectus capitis poste-
rior major (RCPMa), the obliquus capitis inferior
(OCI), and obliquus capitis superior (OCS) muscles.
The RCPMi arises from the posterior tubercle on the
posterior arch of C1 and inserts on the occipital bone
inferior to the inferior nuchal line and lateral to the
midline. The RCPMa arises from the posterior edge of
the spinous process of C2 and inserts on the occipital
bone inferior to the inferior nuchal line and lateral to
the RCPMi muscles. The OCI arises from the lateral
surface of the spinous process of C2 and inserts on
the inferior surface of the transverse process of C1.
The OCS arises from the superior surface of the
transverse process of C1 and inserts on the smaller
lateral impression between the superior and inferior
nuchal lines on the posterior aspect of the occipital
bone (Moore, 1992).
While the four suboccipital muscles can be function-
ally classified as extensors and rotators, their small
size, relative to larger muscles that act in parallel with
them, minimizes their contribution to motion (Nitz and
Peck, 1986). A parallel combination of muscles (PCM),
i.e., smaller muscles acting across joints in parallel
with much larger muscles, occurs often in humans.
These smaller muscles typically have an average of
3.76 times as many spindles per gram of tissue as do
their large counterparts, with the greatest absolute
value of spindle density occurring in the suboccipital
muscles of the cervical spine (Peck et al., 1984). In
addition to stabilizing the respective joints around a
neutral position, it has been suggested that these
small muscles provide significant proprioceptive input
to the CNS that is directly related to position and
motion of the head (Abrahams, 1977).
The preferred way to perform an electrodiagnostic
examination of the suboccipital muscles would be to
use needle electrodes (Weiss et al., 2004). However,
this procedure is accurate only to the extent that the
performed,partly
physician is able to reliably place the needle into the
correct muscle. The suboccipital muscles present a
challenge in that they are physically small, are
located in close proximity to one another, and have
similar and poorly documented actions, making it dif-
ficult for a patient to recruit them in isolation. Atro-
phied muscles with fatty replacement present an
additional challenge. In addition to being physically
smaller than a normal muscle, the electromyogra-
pher cannot always rely upon insertional activity to
determine when the needle has been inserted into
the atrophied muscle (Haig et al., 2003). The pres-
ence of critical structures such as the spinal cord and
the vertebral artery further complicates the proce-
dure and further emphasizes the need for a standar-
dized protocol to guide the placement of needles.
METHODS
Cadavers
The cervical regions of 11 embalmed cadavers,
prepared by the Division of Anatomy & Structural
Biology, were used in this study. Three of the
cadavers were used to develop a standardized pro-
tocol that could be used to guide placement of nee-
dle electrodes into the four suboccipital muscles.
Using this standardized protocol, three investigators
attempted blind needle insertions into each of the
four suboccipital muscles in each of the remaining
eight cadavers. The age, cause of death, premorbid
weight,andheight of
obtained. However, bodies varied randomly with
regard to these parameters. The ages were esti-
mated to be between 75 and 85 years. None of the
specimens were considered to be heavily muscled
or obese. The selection consisted of 6 males and 5
females. The cadavers were embalmed in a stand-
ard manner using formalin. The cadavers had been
stored in the supine position for a significant period
of time. This, along with tissue texture changes pro-
duced by the embalming process, made palpation of
boney landmarks, insertion of needles, and reposi-
tioning of joints different, and probably more diffi-
cult, than would be experienced with living sub-
jects.
thecadaverswere not
Reference Points and Lines
To standardize the protocol, a number of refer-
ence points and lines were established by consensus
(see Fig. 1). The locations of the external occipital
protuberance (inion) and the spinous process of C2
were palpated and marked. Since the spinous pro-
cess of C2 was used as a reference point for an
approximation of the location of several other struc-
tures, the investigators not only attempted to pal-
pate this structure, but they also attempted to con-
firm its location with a needle probe. A line drawn
between the inion (see Fig. 1, Point A) and the spi-
nous process of C2 (see Fig. 1, Point B) was used to
define the anatomical midline of the posterior cervi-
cal spine.
502Hallgren et al.

Page 3

The posterior arch of C1 (see Fig. 1, Point E) was
approximated by marking a point on the midline that
was 2/3 of the distance between the inion and the
spinous process of C2, measured from the inion.
The lateral impression
and inferior nuchal lines on the posterior aspect of
the occipital bone was palpated and used as an
approximation of the point of insertion of the OCS
muscle (see Fig. 1, Points C). An alternative method
was to mark the intersection of the superior nuchal
line and a line drawn from the spinous process of C2
at a 45-degree angle from the midline (see Fig. 1,
Line B ? C).
A point 1 cm below the inferior border of the
tragus was identified as a first approximation of the
location of the lateral process of C1 (see Fig. 2).
Another point at the same height as this point and 3
cm medial to the posterior medial border of the mas-
betweenthesuperior
toid process was used as the final approximation of
the location of the lateral process of C1 (see Fig. 1,
Points D).
A line drawn from points D ? C was used to ap-
proximate the location of the long axis of the OCS
muscle (see Fig. 1). A line drawn from points D ? B
was used to approximate the location of the long
axis of the OCI muscles. A line drawn from points
B ? C was used to approximate the location of the
long axis of the RCPMa muscles.
Technique For Protocol Testing
A technique for needle localization of muscles in
the lumbar spine in cadavers has been previously
described (Haig et al., 1993). It involves inserting a
thin wire into a hypodermic needle, and then insert-
ing the needle into the target muscle. The tip of the
Fig. 1.
Reference points and lines (Reproduced with permission, copyright Primal Pictures Ltd.).
Fig. 2.
Approximation of the lateral process of C1.
503Protocol for Needle Placement in Suboccipital Muscles

Page 4

wire is bent to form a ‘‘hook’’ (see Fig. 3A). Once the
desired location within the muscle is reached, the
needle can be withdrawn, leaving the wire hooked
within the muscle. A dissector can then trace the
path of the wire and the final resting place of the tip
of the wire. For the current study, a standard 15-
gauge hypodermic needle, 79 mm in length was
used. While wires can be placed in very thin needles,
this needle size was used because the stiffness mini-
mized bending in tissue planes. A 110-mm length of
0.406 mm spring tempered music wire was used for
the hooked reference wire. The hook in the wire was
bent so that it would spring out and be securely
lodged within the muscle when released from the
lumen of the needle (see Fig. 3B). Two investigators
(RCH and JJR) used this technique. An advantage in
using the hooked-wire technique was that it allowed
the dissector to record both the location of the hooked
tip of the wire and the path that the needle had fol-
lowed. Another advantage was that a label, containing
the initials of the investigator and the name of the tar-
geted muscle, could be applied to the protruding end
of the wire. A weakness of this technique was that the
investigator was not able to pull back the needle for a
secondattemptwithout
released and captured within a muscle.
The third investigator (MTA) used a 15-gauge
needle and syringe to inject red latex (0.5 cc) into
the target muscles (Haig et al., 1991). An advantage
to using the latex injection technique was that the
investigator could insert the needle, pull back and
then reinsert the needle, much like an electromyog-
rapher might need to do with a patient. A weakness
of the latex injection technique was that it only left a
record of the final location of the tip of the needle
and not its path of insertion. Consequently, while it
can be determined that the investigator (MTA) hit a
target muscle, it is impossible to know for certain
that the intended muscle was hit.
Since it would have been impractical to blind the
dissector to the intended location of the inserted
wire, the research protocol was not blinded. Each in-
vestigator attempted to make an insertion into each
the hooked wirebeing
of the eight muscles. Immediately following each
insertion, a label, containing the initials of the inves-
tigator and the name of the targeted muscle, was
applied to the protruding end of the wire. The order
was rotated for each cadaver. While the same land-
marks and insertion points were used, each investi-
gator determined their line and angle of insertion in-
dependently. After allowing two days for the latex to
cure, an experienced dissector (AJW), different from
the three investigators, carefully dissected the cervi-
cal spine down to the suboccipital muscles to deter-
mine the locations of the latex and the locations of
the tips of the hooked wires, using techniques
described in the Appendix. An injection was judged
to be a ‘‘hit’’ if the latex adhered to a surface of the
muscle or was contained within the muscle. A
hooked wire was judged to be a ‘‘hit’’ if the wire was
lodged within the muscle (see Fig. 4). The position of
a ‘‘miss,’’ for both techniques, was recorded as supe-
rior, inferior, medial, lateral, posterior, and/or ante-
rior relative to the targeted muscle.
Final Study Protocol
For each of the following four protocols, the final
action taken after insertion of the needle was to
release the wire from the needle and retract the nee-
dle, leaving the wire in the targeted muscle. A simi-
lar procedure was followed for injection of latex into
the targeted muscle.
Rectus Capitis Posterior Minor Muscles
(RCPMi)
The needle was inserted, with the bevel positioned
caudad, at a point 1 cm lateral to the midline at the
level of the approximation of the posterior arch of C1
(see Fig. 5, Points 1). The needle was directed ceph-
alad and angled approximately 80 degrees from an
imaginary line drawn parallel to the surface of the
skin in the midsagital plane. The needle was inserted
until bone (occiput) was reached and withdrawn
slightly.
Fig. 3.A: Reference wire in needle. B: Reference wire released from needle.
504Hallgren et al.

Page 5

Rectus Capitis Posterior Major Muscles
(RCPMa)
The needle was inserted, with the bevel positioned
caudad, at a point 2 cm lateral to the midline at the
level of the approximation of the posterior arch of C1
(see Fig. 5, Points 2). The needle was directed lateral
and cephalad along the approximation of the long
axis of the RCPMa muscle, and angled approximately
80 degrees from an imaginary line drawn parallel to
the surface of the skin and along the approximation
of the long axis of the RCPMa muscle. The needle was
inserted until bone (occiput) was reached.
Obliquus Capitis Superior Muscles (OCS)
The needle was inserted, with the bevel positioned
caudad, at Points 3 (see Fig. 5)—Note that Points 3
in Figure 5 and Points D in Figure 1 are one and the
same. The needle was directed medial and cephalad
along the approximation of the long axis of the OCS
muscles and angled approximately 45 degrees from
an imaginary line drawn parallel to the surface of the
skin and along the approximation of the long axis of
the OCS muscle. The needle was inserted until bone
(occiput) was reached.
Obliquus Capitis Inferior Muscles (OCI)
The needle was inserted at a point 4 cm from the
approximation of the spinous process of C2 (see Fig.
5, Points 4) with the bevel positioned caudad. The
needle was directed medial and caudad along the
approximation of the long axis of the OCI muscle
and angled approximately 90 degrees from an imagi-
nary line drawn parallel to the skin and along the
approximation of the long axis of the OCI muscle.
The needlewas inserted
reached, or until the needle had reached a depth of
no more than 4–5 cm.
untilbone(C2) was
Fig. 4.
Dissected specimen showing location of hooked wires.
505 Protocol for Needle Placement in Suboccipital Muscles