The role of the sphenobasilar synchondrosis (SBS) in health and disease – a structured literature review
sphenobasilar synchondrosis

The role of the sphenobasilar synchondrosis (SBS) in health and disease – a structured literature review

INTRODUCTION:

The sphenobasilar/spheno-occipital synchondrosis/synostosis (SBS) plays a major role in the concept of Osteopathic Cranial Manipulative Medicine (OCMM) and Craniosacral Therapy. Previous research suggests that many individuals, from newborns to adults, present with one or several SBS strain patterns as a result of the birth process and other traumatic forces throughout life. To date, it is unclear whether specific SBS lesion patterns are present in altered health states and disease, and how they compare to healthy controls. 

OBJECTIVE:

To identify research literature that reports on specific SBS strain patterns compared to healthy controls.

METHODS:

Structured literature review of electronic databases and hand-search of publication biographies. Included were observational studies of adults and children/newborns, if they presented information on the occurrence of cranial strain patterns related to the SBS in individuals with impaired health states and also included a healthy control group.

RESULTS:

Out of a total of 1123 citations, 836 records were screened after duplicate removal. A total of 42 articles were evaluated by full-text assessment, and 3 articles were included in this review, including one prospective and two retrospective studies. The age ranges of the populations studied were newborns, children aged 4-14 years and adults. In adults with Parkinson Disease, no significant difference in SBS strain patterns between the PD group and the age-matched healthy control group were seen. In contrast, different SBS strain patterns between children with learning disabilities and newborns with a range of health impairment were observed, compared with their healthy counterparts. However, no statistical analysis was conducted in these two studies, hence results are difficult to interpret. Reporting in all three studies was limited, hence the methodological quality of the three identified studies was deemed unjudgeable.

CONCLUSION:

The identified study landscape of this review highlights a scarcity, poor reporting and unclear methodological quality of research on the topic of SBS strain patterns in health and disease. It is still unclear whether and to what extent specific SBS strain patterns in impaired health states compared to healthy controls occur, both in adults and children. Future studies should seek to improve reporting and minimize risk of bias.

Introduction

The sphenobasilar/spheno-occipital synchondrosis/synostosis (SBS), representing the articulation between the occiput and the sphenoid bone, is regarded a major component of the cranial model which was originated by W.G. Sutherland through his observations that the individual bones of the skull show mobility.1 According to Sutherland, movement or an autonomous event can affect the SBS which in turn may have an impact on the reciprocal tension membranes and sutures of the skull.1 Magoun describes the SBS as the “… key to understanding the entire cranium. Lesions of this mechanism can be profoundly significant.”.2 (p117) According to Magoun, the SBS relates to some of the most vital parts of the nervous system, and SBS strains are reportedly found by practitioners in patients with headache , facial paralysis, salivation, myopic astigmatism, vertigo, hypertension, sinusitis and many other conditions. 2 (p120) Possible wider ranging effects of these lesions may be an alteration of the vascular supply to vital areas of the central nervous system and the normal movement of the cerebrospinal fluid in the subarachnoid space. 2 (p117-121)

The importance of the SBS in the current osteopathic literature is echoed based on these teachings, where strains of the SBS are thought to have an impact on the health of the individual, or where the SBS should be assessed in any complaint referring to the head, ears, nose, throat and eyes.3,4

 

According to Starkey (2015), the term spheno-basilar synchondrosis is still used in much of the recent craniosacral literature without giving reference to the ossification status of the joint.5 He suggests that, in accordance with other authors, until the ossification of cartilaginous joints is complete, the SBS is referred to a synchondrosis, and once complete it becomes a synostosis.5,6

Cranial strain patterns which result from membranous articular strains due to abnormal dural membrane tensions,7 are commonly presented by a free, prompt and full motion of the occiput and sphenoid in only one direction at the SBS.8 Cranial strain patterns are classified as follows:9-11

 

  • Lateral (left or right) – when the sphenoid and occiput rotate in the same direction about their respective vertical axis, creating a shear mode of motion in the SBS
  • Sidebending/rotation (left or right) – occurs when the sphenoid and occipital arches rotate in opposite directions about two parallel vertical axes – one through the body of the sphenoid and the other through the foramen magnum
  • Torsion (left or right) – occurs around an anterior-posterior axis of the skull as the sphenoid and occipital rotate in opposite directions
  • Vertical (superior or inferior) – occurs when the sphenoid and occipital rotation is in the same direction about their respective transverse axes
  • Compression – occurs when sphenoid and occiput have been forced together, so that physiologic flexion/extension is impaired
  • Flexion – is characterized by an elevated SBS, with an increased upward convexity
  • Extension – SBS is lowered, the upward convexity is decreased

 

Some cranial strain patterns, particularly torsion and sidebending/rotation, are considered physiologic, such as due to daily strains on the human body.10 Examples of common conditions with these strain patterns were reported to occur in headache, endocrine disorders, motor disturbances and other musculoskeletal conditions.12 Non-physiologic strain patterns, such as vertical or lateral strain, usually are the result of major trauma, such as birth, surgical procedures, external force.8,12

 

Albeit good quality evidence is lacking, it is commonly speculated that OCMM may be able to reduce cranial strains and restore normal mobility at the SBS and related structures, which would result in improvement of blood flow and flow of cerebrospinal fluid and hence, increase overall health of the patient. 2 (p117-121)

 

However, some authors have recently questioned the clinical significance of primary SBS lesion patterns and their treatment in adults, when considering the age of ossification of the SBS. According to recent research literature, the ossification of the SBS is completed between the 13th and 17th year of age.13,14 Liem (2009) argues that once the SBS becomes ossified in early adulthood, the therapeutic relevance of the SBS region may become reduced.15 Starkey in his review about arguments for or against movement at the SBS concluded that due to ossification during early adulthood and subsequent lack of movement, subsequent SBS lesions could neither develop nor be removed by treatment.5

Previous research suggests that a significant number of individuals, from new-borns to adults, present with one or several cranial strain patterns as a result of the birth process and may encounter other traumatic forces throughout life.16-18

In order to understand the role of the SBS and its accompanying lesions in the process of health and disease in adults as well as children, one step forward may be to understand the occurrence of SBS strain patterns in health and impaired health states.  To date, however, it is unclear whether specific SBS lesion patterns are present in altered health states and disease, and how they compare to healthy controls. 

The aim of this structured literature review is to identify research literature that reports on specific SBS strain patterns compared to healthy controls, as part of prospective or retrospective observational studies.

Methods

A narrative structured literature review was performed by searching the following electronic databases from inception to 13thth May 2018: Pubmed, Physiotherapy Evidence Database, Osteopathic Medicine Digital Repository, Cochrane (all databases), Index to Chiropractic Literature, and the Journal of the American Osteopathic Association (JAOA) database.  Additionally, google scholar was manually searched, and citation tracking was applied to all selected articles. The keywords ‘sphenobasilar synchondrosis’, sphenobasilar synostosis’, ‘spheno-occipital synchondrosis’, spheno-occipitalsynostosis’, and ‘craniosacral’ were used to identify potentially suitable articles and studies. An additional search in all databases described above was performed on 9th October 2018 for the keyword ‘cranial strain pattern’. Included were observational studies of adults and children/newborns, if they presented information on the occurrence of cranial strain patterns related to the SBS in individuals with impaired health states and also included a healthy control group.

Identified eligible information from original studies was narratively synthesized in table format, including study design, objective, and study outcome with respect to SBS strain patterns.

Results

Database searches revealed a total of 678 citations from the initial search and 445 citations from the updated search. After duplicate removal, 836 records were screened. Out of 42 articles which were evaluated by full-text assessment, 3 articles were selected for this review, including one prospective and two retrospective studies (Table 1).

sphenobasilar synchondrosis table 1

The following paragraphs provide a brief description of each included study: 

The study by Frymann and coworkers (1966) examined 1250 newborns for anatomical disorders of the craniosacral system in relation to their symptoms.

Infants were included in this study if a history of labor was available. Each child included in the study was examined by a doctor in the first five days after birth. Abnormal behavior or symptoms of the children were categorized as: asymptomatic (no abnormal symptoms were noted), nervous (children with vomiting, loss of appetite and failure to thrive, muscular hypertension, spasm, tremor and insomnia), circulatory or respiratory problems (difficult breathing or excessive mucus, circulatory stasis with cyanosis), and jaundice mongoloid (infants with jaundice or mongoloid appearance). Examination of the child included observation of the whole child, posture, muscle tone, nervous irritability, color and shape. The examination of the craniosacral system included the sacrum and skull, which included assessment of the condylar parts of the occiput, the mobility of the SBS, flexion and extension patterns, as well as vertical strain patterns and motility of the temporal bones.19

Of 1250 infants, 874 were classified as asymptomatic, 8 infants belonged to the group of jaundice mongolid, 157 had respiratory and circulatory problems, and 211 had nervous symptoms. 

In nervous infants, the incidence of SBS flexion strain patterns was highest (21%) compared to all other classifications (7% of respiratory and circulatory infants, 8% asymptomatic infants, 14% of jaundiced mongoloid infants).19 Compression patterns were found in 36% of nervous infants, compared to 28% of jaundiced mongoloid infants, 19% of respiratory and circulatory infants and 13% of asymptomatic infants.The incidence of SBS torsional stress patterns was highest in infants with respiratory and circulatory symptoms (36%) compared to asymptomatic infants (30%) (Table 2). No statistical analysis was performed between the groups, and the author’s conclusion of the study results was that strain patterns within the developmental part of the occiput were of significance in the development of nervous symptoms, which may be commonly accompanied by flexion strain of the SBS and an extension strain of the sacrum as well as a higher frequency of compression of the SBS. A relationship between a torsion strain of the SBS together with restriction in temporal mobility was suggested in infants with respiratory and circulatory symptoms. 

Another study by Frymann (1976) investigated the influence of cranial somatic dysfunctions on childhood learning disorders. This was a retrospective study, using cases from the author’s own practice. Patients were between 4 and 14 years of age and were divided into the following categories: Group 1 consisted of 74 students with no visual or learning difficulties, Group 2 included 32 students with visual impairment but no learning difficulties, and Group 3 consisted of 103 children with learning difficulties. This resulted in a total of 106 children without and 103 children with learning difficulties.20

According to this study, 73% of children who later showed learning disabilities, suffered from a major traumatic event during or before birth, such as births of 12 hours or more, or prolonged periods of ineffective labor resulting in C-section. In children without learning difficulties, birth trauma was present in only 28% of children.

Of the 103 learning disordered children, 86% were diagnosed withlateral strain, 46% with vertical strain, and 40% of the children displayed a compression of the SBS. Out of the 106 children without learning disabilities, 71% of the children were diagnosed with lateral strain, 38% with vertical strain, and 32% with compression of the SBS (Table 2).20

Based on these results, the author of this study concluded that ‘the whole range of traumatic patterns may be found in children with learning problems as well as in children who do not have a learning disability’. Since no statistical analysis between both groups was performed, this very generalized conclusion matches the results of this study.

Rivera-Martinez (2002) conducted a retrospective study of patients with Parkinson’s disease (PD) to compare palpatory observations of cranial SBS strain patterns with common cranial palpation findings from healthy volunteers.21

30 patients with idiopathic PD and 20 healthy controls of the same age were randomly identified from patient records of three osteopaths (investigators). Records of patients and controls of both sexes were included in the study when patients were between 45 and 90 years old, regardless of ethnicity. The subjects were excluded if there was evidence of head trauma in the last two months, a brain tumor or a life-threatening illness. The primary data collected were evaluated by the respective osteopaths (investigators) of patients or osteopathic manipulative medicine (OMM) scholars under their supervision. 21

The authors of this study found that PD patients had a significantly higher incidence of bilateral atlanto-occipital compression (87%) and bilateral occipito-mastoid compression (40%) compared to healthy controls (50% and 10%, respectively). There was no significant difference in SBS strain patterns between both groups (Table 2). 21

sphenobasilar synchondrosis table 2

Discussion

The aim of this structured literature review was to identify specific SBS strain patterns in impaired health states, compared to healthy controls. Three studies, published in 1966, 1976 and 2003 were identified and included in this review. The age ranges of the populations studied in these publications were newborns, children aged 4-14 years and adults.

In all three studies, the healthy controls all presented with low rates of SBS strain patterns, which were mostly of physiologic nature. This has been described in the literature before and confirms current knowledge. 16-18

In adults with PD, no significant difference in SBS strain patterns between the PD group and the age-matched healthy control group were seen. However, some additional distinct articular restrictions and dysfunctions were seen in the PD patients (bilateral atlanto-occipital compression and bilateral occipito-mastoid compression) which were significantly more present compared to the control group. Arguably, the sample sizes in both groups were small which may have prevented a notable difference in SBS patterns between groups. Additionally, the severity of these SBS lesion patterns is unclear since this was not assessed. It could well be that SBS strain patterns were present at largely the same rates between both groups but that the severity of these may have differed, which may leave clues about a possible influence of these restrictions on the disease process. Liem (2009) and others questioned the clinical significance of the SBS in adults as the ‘primary lesion site’, due to its ossified state.15,5 It appears that in the identified study of adults with PD, this argument might have merit, since no difference between SBS strain patterns was seen in the PD and control groups, however, it is unclear whether addressing these SBS strain patterns in the PD population would improve any of the symptoms or disease processes. Hence, the current evidence is to be interpreted with caution and generalisability to other adult patient populations cannot be made.

In contrary, in infants and young children, the SBS is not yet ossified, and it could be speculated that specific SBS strain patterns may be prevalent in altered health states and that treatment of the SBS as primary lesion site may be more relevant in this patient population.

The two identified studies by Frymann (1966, 1976) showed different SBS strain patterns between the affected groups of children with learning disabilities and newborns with a range of health impairment, compared with their healthy counterparts.19,20 However, no statistical analysis was performed in these studies, so the validity of these results is low and can serve as cause for speculation at best.

 

For applicability of these study results, it is important to note the major study limitations of these included studies. All three studies were published before the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines came into effect in 2014.22 Hence, reporting is limited and poor in the cases of Frymann (1966, 1976). Therefore, the methodological quality of the three identified studies was deemed unjudgeable. Future studies should adhere to the STROBE reporting guidelines and take additional research literature into account which give guidance on how to improve the methodological quality of observational studies and minimise the risk of bias.23

Additionally, the risk of bias inherent to the assessment procedure of SBS strain patterns cannot be underestimated. The physical assessment findings are subjective to each physician performing those assessments and are underlined by a variety of palpatory protocols that most likely differ between studies, so results should not be compared between studies, unless the same physicians perform these assessments. There may be the possibility of physician bias towards particular types of findings and methods of assessment. In all three identified studies, it is unclear whether the examiner who identified SBS strain patterns also took the case history of the patient, i.e. knew about the specific symptoms and problems of the patient, which was mentioned as one of the obstacles of cranial pattern palpation in a review by Liem (2018).24 As previously described, habitual and context-related influences on palpatory outcomes could have impacted the study results, such as pareidolia and cognitive bias as well as intuition or inattentional blindness.25 If one physician assesses strain patterns in both health-impaired and healthy individuals, it may be advantageous to blind the assessor to patient information, in order to avoid those influences.

In terms of the number of physicians performing the assessment of the SBS strain patterns, it is unclear whether multiple assessors or single assessors would be more advantageous. Previous research suggests that there is substantial intra-rater reliability when diagnosing cranial strain patterns.26 An inter-rater reliability study of cranial strain patterns and the Cranial rhythmic impulse by Upldger (1977) reported a match rate of 71% between two palpating osteopaths.27 However, Upledger did not report the reliability of the assessment but provided the raw data from which an intraclass correlation coefficient (ICC) was computed by Wirth-Patullo (1994). The ICC was 0.57 (57%), which was judged to be in the middle range, which Wirth-Patullo considered too low to support Upledger’s conclusion that the investigation can be conducted with an acceptable level of reliability.28 Additionally, Hartman and Norton (2002) comment on the major weaknesses of the study methodology and implementation, as well as negligence in the measurement processes, which may have influenced the study results.29 Hence, inter-rater reliability in the assessment of cranial strain patterns remains to be proven.

 

The present review has the following limitations: Only English language articles were included, which may have led to the exclusion of relevant articles in other languages. Authors of original publications were not contacted for additional information on data, and database searches were restricted to peer-reviewed literature only. The search strategy for this narrative review was very specific with regard to the keywords used. Future reviews should include the keywords ‘osteopathy in the cranial field’ and ‘osteopathic cranial manipulation’ to broaden the search and increase the possibility to identify additional publications on this topic. This research was performed by only one author; hence potential publications may have been missed due to lack of conformation by a second reviewer.

 

Conclusion

The identified study landscape of this review highlights a scarcity, poor reporting and unclear methodological quality of research on the topic of SBS strain patterns in health and disease. Based on the results of this review, it is unclear whether and to what extent specific SBS strain patterns in impaired health states compared to healthy controls occur, both in adults and children. Future research should add to this identified evidence base, taking current research standards with respect to study reporting and minimizing the risk of bias into account, specifically in regard to the assessment of strain patterns of the SBS. 

References

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