Osteopathy in the Cranial Field
Comprehensive OMT reference hub, interactive cheat sheets, and board review notes for COMLEX Level 1, 2-CE, and 3.
Key Takeaway
Osteopathy in the Cranial Field assesses the Primary Respiratory Mechanism (PRM). Master the 5 PRM principles, SBS Flexion (sacral base moves posterior/extension, head widens) vs. Extension (sacral base moves anterior/flexion, head narrows), the 6 Cranial Strain Patterns (Torsion, Sidebending/Rotation, Vertical, Lateral, Compression), and the CV4 Still Point technique for COMLEX.
The 5 Principles of the Primary Respiratory Mechanism (PRM)
Developed by William Garner Sutherland, DO, Cranial OMT is based on the 5 interconnected physiological phenomena of the Primary Respiratory Mechanism (PRM). Normal CRI (Cranial Rhythm Impulse) rate is 10 to 14 cycles per minute.
| Principle Number | PRM Component | Biomechanical Action |
|---|---|---|
| 1 | Inherent Motility of Brain & Spinal Cord | Subtle coiling and uncoiling of central nervous system during flexion/extension. |
| 2 | Fluctuation of Cerebrospinal Fluid (CSF) | Hydrodynamic wave created by CSF production and absorption. |
| 3 | Motility of Intracranial & Intraspinal Membranes | Reciprocal Tension Membrane (RTM) anchored at Falx Cerebri, Tentorium Cerebelli, and C2/C3/S2 dural attachments. |
| 4 | Articular Mobility of Cranial Bones | Micro-motion along cranial sutures (especially Sphenobasilar Synchondrosis - SBS). |
| 5 | Involuntary Mobility of Sacrum | Sacral motion between ilia around the Superior Transverse Axis at S2. |
SBS Flexion vs. Extension Phase Rules
| Anatomical Feature | Flexion Phase (Cranial Inhalation) | Extension Phase (Cranial Exhalation) |
|---|---|---|
| SBS Joint Motion | Sphenoid and Occiput flex (rotate in opposite directions, rising at SBS). | Sphenoid and Occiput extend (falling at SBS). |
| Cranial Vault Shape | Widens transversally (AP diameter decreases, head gets wider). | Narrows transversally (AP diameter increases, head gets narrower). |
| Paired Bones (Temporal/Parietal) | External Rotation. | Internal Rotation. |
| Sacral Motion | Sacral Base moves POSTERIOR (Sacral Extension). | Sacral Base moves ANTERIOR (Sacral Flexion). |
HIGH-YIELD BOARD TRAP: Cranial FLEXION equals Sacral EXTENSION! When the sphenoid flexes, the dural tube pulls the sacral base posteriorly into extension around S2.
The 6 Cranial Strain Patterns
| Strain Pattern | Axis of Motion & Naming Rule | Etiology / Mechanism |
|---|---|---|
| Torsion | 1 AP Axis. Named for the HIGHER Great Wing of Sphenoid. | Blow to top of head or under mandible on one side. |
| Sidebending / Rotation | 1 AP Axis & 2 Vertical Axes. Named for the LOWER / WIDER side. | Lateral impact to head at SBS level. |
| Superior Vertical Strain | 2 Transverse Axes. Sphenoid base tilts ANTERIOR / SUPERIOR relative to occiput. | Impact to top of head posterior to SBS or under chin. |
| Inferior Vertical Strain | 2 Transverse Axes. Sphenoid base tilts INFERIOR relative to occiput. | Impact to forehead or top of head anterior to SBS. |
| Lateral Strain | 2 Vertical Axes. Sphenoid and occiput rotate in SAME direction around vertical axes (Parallelogram shape). | Side impact to head anterior or posterior to SBS. |
| Compression | SBS jammed together along AP axis. CRI severely reduced or ABSENT. | Direct blow to front or back of head; severe birth trauma. |
High-Yield Cranial Techniques
| Technique Name | Hand Placement & Setup | Clinical Indication & Induces |
|---|---|---|
| CV4 (Compression of 4th Ventricle) | Medial border of palms under occiput (thenar eminences medial to occipomastoid sutures). Encourage extension, resist flexion. | Induces a Still Point. Stimulates CSF fluctuation, lowers fever, relaxes uterine contractions / promotes labor. |
| V-Spread Technique | Two fingers on either side of restricted suture; opposite hand on diametrically opposite cranial wall. | Releases jammed interosseous cranial sutures. |
| Venous Sinus Drainage | Sequential finger pressure along Occipital, Transverse, Straight, and Superior Sagittal sinuses. | Clears intracranial venous congestion, tension headaches. |
High-Yield Board Traps & Practice Drills
Q: What sacral movement occurs during the Flexion phase of the Primary Respiratory Mechanism?
A: Sacral EXTENSION (Sacral base moves posterior).
Q: A cranial strain pattern presents with a high right great wing of the sphenoid. What is the strain pattern?
A: Right Torsion (named for the side of the higher great wing of the sphenoid).
Q: Which cranial technique is used to induce a Still Point, lower a fever, and stimulate CSF flow?
A: Compression of the 4th Ventricle (CV4 Bulb Bounce).
Source
Based on the publicly available table of contents and topic organization of OMM Review: A Comprehensive Review of Osteopathic Medicine. All notes are original; no copyrighted text, figures, or full source material is included.