By Dick Greenan

A proper Cephalogram should provide the diagnostician excellent bony detail in addition to an adequate soft tissue profile. Clear visualization of the Lambodial suture (the suture extending up from the floor of the skull at approximately a 45 degree angle posteriorly towards the occipital bone) is a must and a benchmark for all Cephalograms. If the Lambodial suture can be clearly visualized, then too will anatomic porion in addition to the other hard tissue landmarks. A Cephalogram which is too light    (under-exposed, under-developed) will generally afford an adequate soft tissue profile, but the bony landmarks will be washed-out and difficult to interpret. Under such circumstances, following proper darkroom procedures, it would be necessary to increase the exposure time until such time that the Lambodial suture can be clearly seen. Conversely, if the Cephalogram is too dark, and light leakage in the darkroom has been ruled out, then it would be necessary to reduce one's exposure time. The objective of this paper is to review those areas of diagnostic importance which are in addition to those landmarks necessary for one's growth and development analysis. The following checklist will have direct clinical correlations and can only contribute to a more comprehensive and accurate diagnosis and treatment plan.

1. Assess the pharyngeal airway in the area of the soft palate for adenoidal tissue hypertrophy. The airway at this point should be a minimum of 8-10 mm in width. An adequate restriction in airway generally results in a mouth breathing, forward head posture, steeper mandibular angle with open-bite tendencies in addition to lack of both cervical and lumbar lordoses. The clinical importance of the pharyngeal airway should not be underestimated particularly in the adolescent where such maxillary growth and development is necessary.

2. Assess the spatial relationship of C1 to the base of the skull. When the skull is properly positioned with both occipital condyles in their respective fossae of C1, one would expect proper range in both the flexion and extension motions. This normal relationship as measured on a cephalogram will on the average be 8-10 mm for both adults as well as children. In contrast, the patient with a chronic forward head posture will typically have a reduced space of only 2-6 mm with severely limited function in both flexion and extension. The forward head posture will affect mandibular position, airway volume and velocity, increased tetany of the sternocleidomastoid and related masticatory muscles in addition to further degeneration of the entire spine.

3. Although we typically only view C1 to C4 or C5, it is important to evaluate the spinal curve - is it within a normal lordotic range or is it kyphotic (a reverse curve)? Are the intervertebral spaces relatively normal and equal? Are there degenerative changes on the anterior corners of the vertebral bodies, aka. spondylosis? Any abnormality will influence mandibular position and your treatment plan!

4. Evaluate the elevation of the hyoid bone as it relates to a line drawn between the anterior- inferior corner of C3 and Rgn. Is the hyoid intersected by this line or is the hyoid above - indicative of hyperactivity of the Supra/ mylohyoids? The hyoid should be intersected by this line or below it.

5. Is there anti-gonial notching (aka. bone deposition at the gonial angle) and is it unilateral or bilateral? Excessive bone deposition at the origin of the masseter muscle indicates masseter hyperactivity and is usually associated with temporalis hyperactivity. A pre-orthodontic treatment objective may be to restore these muscle groups to their physiologic resting lengths prior to orthodontics or in concert with your orthopedics.

6. Although ossification of both the stylohyoid and stylomandibular ligaments are most typically evaluated with the panoramic view, the cephalogram is equally diagnostic as it allows us to ascertain the true extent of its ossification to their attachments at the outer corner of the hyoid and medial surface of the gonial angles respectfully. Ossification of either ligaments is usually indicative of limited range in cervical motion and is typically supported by the above anomalies.

Remember, "Form always Follows Function"!

 Contact Dick Greenan by email:  imagings@earthlink.net

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