July 2012 - Donna Magid, M.D., M.Ed.
Don’t kill or paralyze the patient. Make no assumptions. Be nervous. You are attempting to clear IMAGES, not the PATIENT. Clearly state limitations of exam FIRST: “Limited exam odontoid and T1, visualized portions unremarkable”. If you instead say “Normal, with limited exam odontoid and T1”, it is highly likely the busy emergency medicine clinicians saw nothing past the word “normal.”
WHEN TO OBTAIN C SPINE RADIOGRAPHS: Our Emergency Dept patients are unusually complex, are often unable to give reliable histories, and may have modified mental status or compromised physical exam; one must err on the side of caution. In the community setting the Canadian C Spine Criteria (see below) have been assessed as effective (NEJM 2003; 349:2510-2518) in triaging patients to avoid unnecessary radiography. At the AChm from The Canadian C-spine rule performs better than unstructured physician judgment, see below:
ACR AC: the American College of Radiology Appropriateness Criteria (www.acr.org) also gives an excellent summary of 14 variants of C-spine injury scenarios with best-study summaries, review of the Canadian C Spine Criteria and discussion of the role of several imaging modalities (radiographs, CT, MR, etc.) in c spine trauma.
Figure 1. Cervical spine anatomy
VIEWS: LATERAL, AP, ODONTOID. Additional views “Censored” (hence EMed radiology title): FLEX/EXT, OBLIQUES. Start with LATERAL, get in habit at looking at all same way (L. lateral)
ADEQUACY: must see superior half T1 or ‘limited’ (since 8 cervical nerve roots but 7 cervical bodies) . Swimmer’s view may provide C7-T1. Traction on arms to drop shoulders not advised.
ALIGNMENT: Posterior (NOT Anterior; less consistent) vertebral line: vertebral bodies form smooth continuous lordosis; straightening may = collar, positioning, or muscle spasm.
Spinolaminar line also continuous, smooth (ok for C2 to project 1-2 mm further posterior than C1, C3)
Spinolaminar spaces symmetric, no abrupt changes level-to-level (if narrowed/widened suspect ligamentous injury but check old images—may be chronic/old)
End plates grossly smooth and symmetric; may be straight or slightly concave (check Nl.Variants)
Disc spaces/disc height similar level-to-level (narrowing common with disc disease, will see secondary spondylosis, will be on old studies)
Vertebral bodies: Vertebral body trabeculae regular, similar radiodensities, heights and shapes grossly symmetric
C1-C2 Atlanto-dens interval (ADI): Space between the posterior margin of anterior ring C1 and anterior margin apposed odontoid peg <2.5-3 mm (and stable between flex/ext. if acquired) (see drawing) Can =3-4mm, kids.
Pre-vertebral soft tissues (posterior air column; ETT distorts) ~1/4 AP diameter vertebral bosies C1-C4; approximately triples ledge-like C4-5 (Oropharynx bifurcates to collapsed posterior esophagus, anterior trachea). Pre-vertebral tissues (and adenoids) more prominent in children and may be expanded in crying/screaming child
Odontoid should be ‘straight backed’ relative to the body of C2, anterior margin more pot-bellied where peg joins body (hence the ‘schmoo’ nick-name—Google it); no obvious fracture lines, fragments, angles. (drawing)
Soft Tx calcifications - mostly ignore; anteriorly mostly vascular and/or thyroid, hyoid, cricoid cartilages (check Normal Variants and AP and old images); posterior to spinous process tips, smooth mature well-defined oval radiodensities are ‘incidental nuchal calcification/ossification’ (reflect old healed soft tissue trauma). Sella, Mandible, base of skull, perimeter of image, ‘corners’: responsible for anything unusual on image
AP: never shows C1-C3 (therefore Odontoid AP routine 3rd image) so need to count retrograde.
T1 usually the level with 1st rib BUT cervical ribs (usually small, unilateral or asymmetric but can be surprising large and symmetric), C7 or T1 anomalies, or partial rib resections not uncommon esp. at Hopkins.
TRANSVERSE PROCESSES C7 are transverse or slope DOWN, transverse processes T1 slope UP, confirming vertebral numbering.
ROTATION: Spinous processes define midline; variable inverted-V appearances (see normal variants)
Medial margins clavicles center over spinous processes or patient is ROTATED which modifies tracheal assessment Trachea should be centered over spinous processes and roughly cylindrical caudal to subglottic narrowing. Rotation (check medial clavicles) far more common than tracheal shift or deviation, CAVEAT! If trachea appears truly deviated, compressed, or bowed: check old studies (radiographs of chest or C spine, CTs) for chronicity and to assess if changing (substernal thyroid is common, can be known and unchanged for years; enlargement unusual but must detect; other anterior mediastinal masses more worrisome; new or rapidly enlarging mass compressing trachea is urgent finding, can be neoplasm, hematoma, abscess).
LATERAL MARGINS spine should be sine waves, undulating and continuous
FACET JOINTS symmetric bilaterally
SOFT TISSUES neck, shoulder, symmetric
MANDIBLES level, centered, symmetric (rotation can be positional, pain or spasm, facet subluxation, torticollis, neuromuscular, developmental, acquired but describe if position suboptimal)
LUNG APEX check for symmetry. Not uncommon to detect unsuspected mass, cavity, scar, pneumothorax, clavicular trauma or infection, sternoclavicular abnormality, rib fracture or metastasis—any of which can produce ‘neck pain’. If anything seen/suspected check for older images (C spine, chest, CT) or information in clinicians’ notes (eg, “Pt reports treated for TB 1995”, “Pt states told had small scar in lung elsewhere”), report if relevant: “incompletely seen 6 mm tissue radiodensity superimposing medial L clavicle, cannot r/o in lung. Hx of breast carcinoma surgery 3 yrs ago, no comparison images. If available elsewhere request comparison, otherwise advise CT” or ‘4 mm irregular at least partially calcified radiodensity L lung apex, without change from radiograph 9/24/2010 and by CT 9/30/10, granuloma.”
ODONTOID VIEW open-mouth to frame C1-C2 between maxilla, mandible, and occiput. Tech will try 2ce but if unable to get, ‘cannot clear C1-C2 without CT.’
ODONTOID PEG upright, intact, no transverse line suggesting fracture. Apparent fragment at tip: check lateral, current hx (acute trauma? Vs. 6 months’ vague neck pain) old images, check Normal Variants (hypoplasis, os odontoidum). Transverse line base of peg: Type II odontoid fractures are the most common—and lethal—of 3 types. R/o but do not assume Mach line (pseudofracture).
LATERAL MASSES C1 appears trapezoidal, centered around peg.
LATERAL MARGINS C1 should line up with LATERAL MARGINS C2 vertebral body within 3 mm total (R, L). >3 mm step off implies expanded ring C1 ie BURST FX (axial load injury)
FLEXION/EXTENSION: Patient must be out of collar. Often requested to assess ligamentous stability and/or help determine if finding on neutral lateral is acute vs. chronic or stable vs. unstable. patient must be alert, oriented, sober, compliant. Do not touch or help the patient. If intoxicated, post-ictal, obtunded can be held in collar until able to comply. Proprioception in neck excellent, if patient states, “I know what you are asking but feels as if my head will fall off,” PUT COLLAR BACK ON! Spinolaminar spaces and lines should open and close symmetrically without abrupt gaps or changes. POSTERIOR FACET JOINTS should maintain contact (vs. ‘perched’ or subluxing)
CT: Check ACR AC. CT is best for bony structures. Usually indicated if radiographs incomplete or equivocal, if abnormalities are found, if clinical suspicion/mechanism of injuries/patient factors increase risk or cloud clinical scenario. Usually reformatted (coronals, sagittals) which helps assess vertebral columns, enhances sensitivity to fracture lines, thecal space, disc and end plate changes, etc. Patient w/ altered mental status, other distracting injuries, unexplained limited range of motion, may need CT.
MRI: Check ACR AC. MR is best for neurologic tissues, soft tissues; takes longer than CT. Indicated if neurologic findings, radiographic or CT findings, suggest need.
July 2012 - Donna Magid, M.D., M.Ed.