James M. Norton, Ph.D.(1)
Department of Physiology
University of New England College of Osteopathic Medicine
11 Hill's Beach Road
Biddeford, ME 04005
Current understanding of the primary respiratory mechanism includes
the concept of a linkage between the movements of the cranium and the
via the spinal dura. To test this model for craniosacral interaction,
were developed to document and analyze the timing of cranial and sacral
cycles in healthy human subjects. A dual examiner protocol was utilized
for a portion of this study, in which two examiners, one at the cranium
and one at the sacrum, could simultaneously and independently document
the cranial mechanism. A significant correlation was found between
and sacral cycle lengths documented separately by individual examiners,
but pairs of examiners monitoring cranial and sacral cycle lengths of
simultaneously did not agree. These findings support predictions of the
tissue pressure, or interactive, model for the cranial rhythm and do
support the concept of cranio-sacral interaction as described in the
key words: cranial rhythm; palpation; manual medicine; craniosacral therapy
Rhythmicity within the neural, respiratory, cardiovascular,
and other systems plays a major role in the maintenance of stable and
conditions within the internal environment of the body. One such rhythm
is the "cranial rhythmic impulse" (CRI)(2)
or "primary respiratory mechanism"(3),
as a rhythmic impulse arising within the cranium that is separate and
from any previously known pulsation and that is discernible on the
surface of the head with gentle palpation2. The movements of
the cranium are thought to be linked with movements in the sacrum
mechanical forces transmitted through the spinal dura2. The
resultant rhythmic activity of the sacrum is manifested by a slight
around a transverse axis slightly anterior to the second sacral segment1.
A recently published model for the palpation of the cranial rhythm(4)
is based on the assumption that cardiovascular and respiratory rhythms
and their contributions to soft tissue pressures of both subject and
are the primary determinants of the cranial rhythm as perceived during
palpation. Experimental validation or refutation of this (or any other)
model for the craniosacral rhythm requires data on frequency that are
and accurate. Our laboratory developed an approach to studying the
mechanism of healthy human subjects that addresses these important
and began a series of experiments designed to test the interactive
pressure model and to assess inter-examiner agreement in the palpation
of the cranial mechanism.
Preliminary findings recently reported by our laboratory indicate
the occurrence of rhythmic cranial cycles can indeed be directly
using an unobtrusive, examiner-operated knee switch. Mean frequencies
healthy human subjects were found to be in the range of 3-6 cycles/min
and examiner experience did not seem to affect the ability to palpate
frequency of the cranial mechanism. These early results suggested that
the cranial mechanism's cycles could indeed be reliably documented, and
that the basic timing of these cycles could be detected even by
If the cranial mechanism produces an independent and palpable physiological rhythm as has been suggested(9), then different examiners should be able to agree on the basic timing (cycle length and frequency) of the cranial rhythm in a given subject under a constant set of experimental conditions. Furthermore, if the linkage between cranial and sacral motion is real, then different examiners palpating the cranium and sacrum should document essentially the same frequency. In order to investigate this hypothesis, a dual examiner palpation protocol was developed in which subjects were monitored by two examiners simultaneously, one at the cranium and the other at the sacrum. This protocol was designed to investigate the presence of palpable cranio-sacral interaction as well as provide an indication of the extent of inter-examiner agreement.
subjects and examiners:
Subjects were students, faculty, or staff at the College of
Medicine of the University of New England. The four men and five women
ranged in age from 22-28 years, claimed to be in good general health,
were not suffering from any acute or chronic illness at the time of
participation in the study. All subjects participated voluntarily in
study, gave their informed consent to cranial palpation only (no
were given), and received no compensation. All of the 6 examiners were
osteopathic physicians with extensive training and experience in
Silent switches activated by examiner knee pressure were attached to
a leg and to the side of a fixed-height, wood-frame examining table.
seated at the head of the table and at its side were asked to depress
switch at the beginning of the flexion (or inhalation) phase of the
mechanism and keep it depressed until the end of the flexion phase. For
the cranium, the beginning of flexion was defined as the point at which
the examiner felt a qualitative change in the direction of cranial
toward "expansion"; the end of flexion was defined as the point at
the direction of movement reversed itself again. For the sacrum, the
were similar and were related to the rocking motion of the sacrum
the cycle. If the cranial mechanism is viewed as a succession of
and extension movements, then this protocol allowed documentation of
duration of one phase of the cycle (flexion or inhalation) and of the
cycle (from the beginning of one flexion to the beginning of the next).
The knee-switches were designed to provide simple, basic information
the timing of the cranial mechanism and was not intended to describe
complex information such as amplitude or the presence of restrictions
A permanent record of the flexion phases was obtained using a chart
recorder (Physioscribe, Stoelting, 620 Wheat Lane, Wood Dale, IL
Activation of the knee switch produced an upward deflection in a
channel corresponding to the flexion phase of the craniosacral cycle.
paper speed used was 2 mm/sec in all measurement sessions; this speed
sufficient to allow direct measurements of flexion duration to the
0.5 sec or estimates of flexion duration to the nearest 0.25 sec. Cycle
lengths were routinely 15-20 sec in duration; measurement error was
in the range of 2.5-3.3%.
The basic data obtained for each measurement session using the
described above consisted of the duration of flexion (in seconds) and
cycle length (in seconds, from the beginning of one flexion to the
of the next) for 8-10 cycles. Cranial frequency (cycles/min) was
as 60 ÷ the mean cycle length in seconds. Calculated frequencies
were validated by visually counting the number of flexions (or
over a period of one minute on the permanent record.
For the dual examiner protocol, six  examiners trained and
in craniosacral techniques were paired and asked to monitor the cranial
mechanism of subjects simultaneously, with one examiner at the cranium
and the other at the sacrum. The two examiners were asked not to speak
or otherwise communicate with one another and were prevented from
up audible or visual cues from one another by a combination of soft
music and a large hanging curtain separating the examiners at the level
of the subject's chest. During a measurement session, simultaneous
of flexion determined at the two sites were obtained using the separate
knee switches for each examiner. Following a 1-2 min rest, the
switched positions and the measurements were repeated. Four subjects
monitored at the cranium and sacrum by all six examiners, and five
subjects were monitored at the cranium and sacrum by two examiners. A
summary of the experimental data, expressed as frequency (cycles/min)
shown in Table 1. The protocol used allowed
between cranial and sacral cycle lengths determined on a subject by the
same examiner within a short period of time, and between cranial and
lengths determined simultaneously on a subject by two examiners.
Statistical analyses were performed using commercially available software (SigmaStat, Jandel Scientific, 65 Koch Road, Corte Madera, CA 94925). The tests utilized included one- and two-way analysis of variance, Pearson product moment correlation, Spearman rank order correlation, linear regression, Student-Newman-Keuls test for multiple comparisons, and Student's t-test. Sample size requirements for a power of 0.8, an of 0.05, and a mean difference in cycle length of 1 sec were met for the statistical tests used in this study.
A significant correlation was found between the cranial cycle
measured separately at the cranium and at the sacrum by the same
In the dual examiner protocol, the two examiners first palpated the
cranial and sacral rhythms of a subject and then switched positions for
a second set of measurements. Each examiner was therefore able to
the cranial mechanism of a subject at two separate sites, the cranium
the sacrum, within a very short period of time, usually less than 10
A highly significant correlation was found between cycle lengths (and
frequencies) documented separately by individual examiners at the
and at the sacrum of subjects, as shown in Figure
1 (top panel) and Table 2.
Agreement among examiners with respect to cranial and sacral
lengths was low.
Although cranial and sacral cycle lengths of subjects determined
by individual examiners are correlated with one another, interexaminer
agreement was low among the experienced examiners utilized in the dual
examiner protocol with respect to cycle lengths measured at the cranium
or the sacrum. Two-way analysis of variance of the dual examiner data
statistically significant degrees of variability in cranial cycle
attributable to both subjects (F = 4.54, p = 0.003, 7 degrees of
and examiners (F = 20.006, p < 0.001, 5 degrees of freedom). These
indicate not only that the subjects differ from one another with
to cranial cycle length but also that variability among the examiners
the documentation of cranial cycle length is greater than would be
by chance even after accounting for the differences among the subjects.
When pairs of examiners document the cranial and sacral rhythms
a subject simultaneously, their findings do not agree.
In contrast to the highly significant correlation between the cranial and sacral cycle lengths of a subject determined separately by the same examiner, no significant correlation could be demonstrated between the cranial and sacral cycle lengths of a subject determined simultaneously by different examiners in the dual examiner protocol (Figure 1, bottom panel, and Table 2). In addition, as also shown in Table 2, no statistically significant correlations were found between cycle lengths measured separately at the cranium or the sacrum of a subject by the two examiners during a session. Furthermore, no consistent temporal relationship could be established between the onset of flexion as documented by the two examiners on the chart record of the experiment. There was no visual evidence of a time delay or phase shift (suggesting a fluid or mechanical wave moving caudally) or of one rhythm being a simple multiple or harmonic of the other.
Our protocol required the examiners to document their subjective
findings in a manner that produced a permanent record for subsequent
Spoken words, nods of the head, or other gestures used to indicate
findings might be heard or observed by subjects and other examiners,
would require the assistance of an assistant to record the signals. We
wanted the permanent record to represent as accurately as possible the
examiners' actual perceptions, and chose the knee switch as the vehicle
for making the most direct link between examiner perception and
The knee-switch method used to collect the data described in this
did not appear to interfere at all with the interaction between the
and the subjects. Subjects were usually completely unaware of the means
by which the recordings were obtained. The slight movement of the
leg required to depress the switch was nearly imperceptible to a person
lying on the treatment table. When questioned informally after the
sessions were completed, new examiners admitted that it took several
to get used to the switch, but from then on the experimental hardware
setup did not interfere with their ability to palpate the cranial
of a subject. All examiners felt that the switch allowed them to record
their palpatory findings directly and accurately.
Several control studies were performed to assess the ability of
to document the timing of cranial cycles using the knee switch. First,
it was shown that examiners could use the knee switch to palpate and
accurately the timing of the inspiratory phase of the respiratory
using subjects whose respirations were monitored and recorded using a
Respiratory cycles were shorter than the cranial cycles observed in
study and therefore would theoretically have a larger measurement error
using our system. Nevertheless, the correlation between respiratory
lengths recorded directly and those documented by an examiner was
significant (Pearson's r = 0.934, p < 0.001).
In a second test of the measurement system, one examiner was asked
document the cranial cycles of three subjects by marking first flexion
phases for 6-8 cycles and then extension phases for a similar number of
cycles. Mean cycle lengths determined using the flexion and extension
were 24.5 ± 4.5 sec and 25.2 ± 5.6 sec, respectively,
no significant difference between the two sets of measurements. Thus,
of the phase used by the examiner to document the timing of a subject's
cranial mechanism, the mean cycle lengths (and therefore the
were the same.
Cranial cycles do not have to be regular in order for their timing
be documented accurately. Fourier analysis can be used to analyze
with a varying periodicity(10), and
method can also be applied to time-domain signals that are square waves
(periodic step functions) similar to the chart records produced in our
protocol. In a third type of control experiment designed to assess our
protocol, the cranial mechanism of a one subject was monitored by an
examiner for a period of more than 11 min, allowing documentation of 40
cycles with an average duration of 17.19 sec (corresponding to a
of 3.49 cycles/min). Fourier analysis of the record transcribed into a
digital form (1 = flexion, 0 = no flexion) at 0.5 sec intervals (a
of 1,344 data points) produced a sharp peak in the frequency spectrum
3.4 cycles/min. Such agreement supports the use of our knee-switch
to record digitally the timing of an analog process
the potential for varying periodicity.
The overall cycle length was chosen as the measurement for
because it was felt to be less sensitive to differences in examiner
skills than the duration of flexion alone. The underlying assumption
that differences in examiner skill or experience might affect the point
in the cycle at which flexion is perceived to begin, but that this
would be essentially the same from cycle to cycle. Since the beginning
and ending of flexion is sensed as a qualitative change in the
of movement, documentation of the timing of a subject's cranial
by the experienced examiners utilized in this study should not be
affected by variations in the baseline amplitude of the mechanism
All examiners so questioned stated that the cranial rhythms of the
used in this study were readily palpable and no different than those
encountered in their practice.
Although cycle length is not usually discussed formally or
as an important feature of the cranial mechanism, it is directly
to frequency, considered to be an important characteristic. As
above, the data analyses in this report were performed on original
length data rather than on calculated frequencies, in order to enhance
statistical validity. Since the time and frequency domains simply
different ways to describe a rhythmic process, conclusions drawn from
length can be readily applied to frequency, and vice versa. In
of the findings presented here, two recent investigations of the
rhythm in which the methods for documenting frequency are clearly
have yielded average frequencies in the same range as those described
It is difficult for this author to reconcile the lack of
agreement seen in this study with the existence of an independent,
palpable physiological rhythm generated within the cranium of a subject
and transmitted to the sacrum, since simultaneous measurements of cycle
length obtained on a subject at the two locations by different
were not correlated at all (Table 2).
the results seem much more consistent with a rhythm that is only
by an examiner to come from a subject but that actually arises somehow
from the interaction between subject and examiner. This statement is
by the fact that measurements of cycle length obtained separately at
cranium and sacrum of a subject by the same examiner were significantly
correlated with one another, but the cranial (or sacral) cycle lengths
of a subject determined by multiple examiners did not agree. These
are consistent with the interactive tissue pressure model3,
according to which an examiner would be expected to perceive the same
in the soft tissues of a subject regardless of the site of palpation.
examiners would not be expected to perceive the same cranial
on a given subject because the persons involved in the interaction are
different and therefore the physiological rhythms combining to produce
the palpated cranial rhythm would be different.
These data do not support the "membrane pulley model"1 or
"spinal reciprocal tension membrane"2 hypotheses for
interaction, which would predict that movements or rhythms at the
would be causally and temporally related to movements at the sacrum,
respect to both mean frequency and the point of onset of the flexion
We could demonstrate no significant correlation between cranial and
rhythms as palpated simultaneously by two examiners, either
or by visual inspection of the experimental records.
In conclusion, our results do not support the existence of a
rhythm that arises within a subject and that is capable of being
documented by experienced examiners. Several possible explanations of
data come to mind: 1) the cranial rhythm does not exist, as suggested
several recent publications on the subject(15),(16);
2) inter-examiner reliability in cranial palpation, an essential
for any meaningful clinical trials of the efficacy of craniosacral
is very poor; and 3) the perception of motion arises from some
of the interaction between an examiner and a subject, in which case
agreement would be expected to be low and the ability of practitioners
of craniosacral therapy to share accurate and objective information
therefore be limited.
Craniosacral therapy continues to be practiced in various forms by physicians, physical therapists and others. Such widespread use of this modality demands further research to confirm the existence and nature of the cranial mechanism, to establish the reliability of information obtained during cranial palpation, to define the characteristics of a normal mechanism, and to generate criteria for determining the efficacy of craniosacral therapy.
The author would like to acknowledge the significant contributions
this study of Richard Broder-Oldach, D.O., and Gretchen Sibley, D.O.,
students at the University of New England College of Osteopathic
at the time the experiments were performed.
FIGURE 1 (lower panel)
Legend for Figure 1
Scatter plots of data obtained during the dual examiner experiments. Each point represents average values for cranial and sacral cycle lengths for a single measurement session. The upper panel compares cycle lengths from all subjects at the two locations documented separately by the same examiner; the lower panel compares cycle lengths documented by two different examiners simultaneously.
Dual Examiner Data Summary for Cranial and Sacral Frequencies(18),(19)
Correlation(20)of Cranial and Sacral Cycle Lengths(21)
1. James M. Norton, Ph.D., is Professor and Chairman of the Department of Physiology at the University of New England College of Osteopathic Medicine, 11 Hill's Beach Road, Biddeford, ME 04005. Address all correspondence and requests for reprints to Dr. Norton. This study was approved by the Institutional Review Board of the University of New England, and was supported by grant #91-14-345 from the American Osteopathic Association.
2. Upledger JE, Vredevoogd JD. Craniosacral Therapy. Chicago, Eastland Press, 1983, p. 6.
3. Magoun, H.I. Osteopathy in the Cranial Field. Kirksville: the Journal Printing Company, 1976.
4. Norton JM. A tissue pressure model for the palpatory perception of the cranial rhythmic impulse. JAOA 1991;91(10):975-994.
5. Norton JM, Sibley G, Broder-Oldach R. Quantification of the cranial rhythmic impulse in human subjects. JAOA 1992;92(10):1285.
6. Sibley G, Norton JM, Broder-Oldach R. Interexaminer agreement in the characterization of the cranial rhythmic impulse. JAOA 1992;92(10):1285.
7. Norton JM, Sibley G, Broder-Oldach R. Characterization of the cranial rhythmic impulse in healthy human adults. AAO Journal 1992;2(3):9-12, 26.
8. Norton, J.M. Documentation of the cranial rhythmic impulse. STILL Alive 1(1):January 1996. (an electronic journal, URL is http://www.rscom.com/osteo/journal/stalive.htm.)
9. Upledger JE. The reproducibility of craniosacral findings: a statistical analysis. JAOA 1977;76:890-899.
10. Noggle JH. QuickBasic programming for scientists and engineers. Ann Arbor, MI; CRC press, 1992, pp. 301-310.
11. Hanten, WP. personal communication.
12. Wirth-Pattullo, V., and K.W. Hayes. Interrater reliability of craniosacral rate measurements and their relationship with subjects' and examiners' heart and respiratory rate measurements. PhysicalTherapy 1994;74(10)908-920.
13. Lee RP. Primary and secondary respiration. Part II. AAOJournal 1993;3(1):17-19, 27.
14. Lee RP. A report to the statutory advisory committee on medical care: craniosacral manipulation. AAO Journal 1991;1(1):13-14.
15. Wirth-Pattullo, V. Interexaminer reliability of palpating the craniosacral motion in the clinical setting. PhysTher 1993 73(6):S10.
16. Ferre JC, Barbin JY. The osteopathic cranial concept: fact or fiction? Surg Radiol Anat 1991 13:165-170.
17. Johnston WL. Interexaminer reliability studies: spanning a gap in medical research - Louisa Burns Memorial Lecture. JAOA 1982 81:819-29.
18. Frequencies are expressed as cycles/min and were calculated as 60 divided by the mean cycle length (in sec) determined for a subject by an examiner.
19. Subjects are designated as S1-S8, and examiners as E1-E6. Examiner pairings were E1 and E2, E3 and E4, E5 and E6. Data are grouped by session, with examiners switching positions between the cranium and the sacrum.
20. The Pearson product moment correlation was utilized to produce this table; the data given for each comparison are the correlation coefficient, the P value, and the number of samples compared.
21. Data shown is from thirty-four  measurement sessions utilizing the dual examiner protocol as described in the text.
22. The comparisons made in this table are: cranial(A)
to sacral(A), pairs of measurements made separately at the cranium
and sacrum of a subject by the same examiner during a measurement
to cranial(B), pairs of measurements made at the cranium of a
by two different examiners during a measurement session;
to sacral(B), pairs of measurements made simultaneously on a
by two different examiners during a measurement session; sacral(A)
sacral(B), pairs of measurements made at the sacrum of a subject by
two different examiners during a measurement session.