How to do a Cervical Myelogram
Bob Dalley, M.D.
A cervical myelogram is a more complex procedure than a lumbar myelogram. It too often is made into a long ordeal for the resident and patient because of poor technique and poor understanding of the simple geometry and anatomic curvatures involved when making a lumbar or C1-C2 puncture.
Assess and consent the patient
Assess the patientís level of physical comfort or degree of pain. Evaluate the patientís stress level. The patient has an I.V. access (usually a hep-lock). Make the patient comfortable. After asking about allergies, give Versed for anxiety and/or Fentanyl for pain.
Rule: A comfortable patient is a cooperative patient.
A cooperative patient makes the myelogram go smoother and may make a big difference if a cervical myelogram is planned.
Consent the patient for potential complications of local pain, headache, infection, and bleeding. If a C1-2 puncture is being performed, a small chance of injuring the spinal cord is present. Ask about allergies and medication history.
Obtain and USE the scout AP, swimmers, and lateral plain films of the cervical spine.
Consult with technologist if films too dark or too light. Get technique right before you start the time-critical filming after contrast injection.
Before you start, make sure the patient is wearing a gown WITHOUT SNAPS or has PJ bottoms. Too often I see the patient nearly naked during filming, which is unnecessary.
Determine whether to do a lumbar or a cervical C1-2 puncture
Cooperative or mildly uncooperative patient
Relatively straight thoracic spine
Good cervical lordosis when extended
Cervical C1-2 puncture
Usually older patients
Must be cooperative to hold still
Moderate to severe thoracic kyphosis
Straight and/or kyphotic cervical spine (Unable to create lordosis with extension)
Recent thoracic or lumbar surgery Ī infection at surgical site
High suspicion of a high grade spinal block caudal to C2.
Absent availability of MRI, trauma C-spine assessment in Striker frame traction.
(SEE HANDOUT on "HOW TO DO A LUMBAR PUNCTURE & MYELOGRAM" for details)
Choose a level to puncture, usually L2-3.
Fasten the feet to the table with ankle restraints BEFORE you begin the LP.
Lower lumbar levels are generally more prone to focal degenerative canal stenosis than L2-3, so avoid making it hard on yourself and the patient.
Use L1-2 cautiously (ONLY if you have an MRI showing the conus lies ABOVE this level), since the conus medullaris may lie this low in some patients.
Obtain any PRIOR STUDIES before you start!: MR, CT and/or myelogram
CERVICAL C1-2 PUNCTURE
(Requires Attending Neuroradiologist be present!)
A. Prone Method
Ideal method that allows biplane fluoroscopy. C-arm is required for lateral fluoro; AP fluoro is done with tableís image intensifier. Request C-arm from the O.R. prior to beginning procedure.
Fluoro to identify the C1-2 disk level. Make sure patient is in true lateral position (This is a key point!). Center fluoro image on C1-2 to alleviate parallax.
Use the scout lateral and divide the cervical canal into thirds. Pick a point at C1-2 which is at the junction of the middle 1/3 and posterior 1/3 of the bony spinal canal. Use a long metal clamp to find the skin puncture site under lateral fluoro. Mark this with a permanent marker.
Clean and prep the puncture site. You may have to shave a little hair. Cover with fenestrated drape.
Anesthetize the skin generously, and using a 1.5" needle anesthetize along the line of puncture as deep as possible. Forewarn your patient that you cannot numb the deep part of the neck and that they may feel some deep discomfort during the puncture.
Rule: Starting out straight will make finishing easier. Take the time initially to get the needle running straight to your desired point in the first 2-3 cm when you can tilt the needle to steer it. If you start deviating from your target point, PULL BACK and REDIRECT. Deeper down, you will steer the needle by turning the bevel.
Rule: The needle will curve AWAY from the face of the bevel. You can steer the needle a few millimeters in any direction depending on which way you turn the bevel (same side as the notch in the hub).
As you get deeper, use both hands to move the needle. One had at the hub and the other fingers pinching the needle a centimeter or less above the skin surface. This creates more control of depth. You may or may not feel the actual "pop" as you puncture the dura. In fact, you will pass though several fascial planes from this approach, each of which may create a pop sensation. For this reason, you need to empirically and frequently pull the stylette out of the needle and check for CSF, EACH TIME you move the needle (When you are close to the canal).
Trick of the trade: When you are close to the dura, turn the bevel posterior so that the needle tip will dive at a steeper angle into the curved dural surface. An anteriorly directed bevel will be more tangential to the dura and is more prone to bounce off.
If you feel the "pop" or if CSF return is minimal, gently push the needle 1-2 mm deeper with the stylette in. This will often reduce the chance of a mixed subdural/subarachnoid injection.
If you get poor flow or bloody flow, DO NOT INJECT! Especially, do not inject if the patient complains of back or leg pain. It means your needle may have PUNCTURED THE DORSAL SPINAL CORD. PULL THE NEEDLE BACK A LITTLE until you get free, clear CSF flow!
When you are in good position, you will have good dripping of CSF out the needle hub.
B. Supine Method
Also done with C-arm. Same puncture technique as with Prone Method
Use this position if patient has a fixed cervical kyphosis or if he/she canít lie on stomach.
C. Lateral Decubitus Method
This alternative method may be used if no C-arm is available, but does have slight additional risk to the patient since you must rotate the patient from the lateral decubitus position to the supine position with the needle in the subarachnoid spaceÖmere millimeters from the dorsal cord.
As with the prone or supine methods, POSITION IS KEY! Make sure the patientís neck is parallel to the table top using towels to raise or lower the head. Check with fluoro to confirm the C1-2 level is true lateral using the tableís fluoro.
Position the patient and mark the skin puncture site.
Use a long metal clamp to localize the puncture site and mark with a waterproof magic marker. Clean and drape. Perform puncture as directed above.
Confirm the needle tip is in the subarachnoid space.
Rule: If you want to confirm CSF return or if you need to collect CSF and want to aspirate on the syringe to speed the process, make sure the bevel of the needle is either CRANIAL or CAUDAL in the LUMBAR spine or POSTERIOR in the CERVICAL spine. If it is sideways the lumbar cauda equina roots can suck up against the needle tip preventing fluid return and giving the patient a rude shock down the leg. If anterior at C1-2 you could potentially suck up against the dorsal cord. Tipping the table will increase hydrostatic pressure if needed.
If you keep hitting bone after numerous attempts or go all the way to the needle hub without getting CSF, get a cross-table lateral film for a lumbar puncture to determine why your needle is out of position. With a C1-2 puncture, you can use the AP fluouro on the table by sliding the table back away from the C-arm or swing the C-arm 90 degrees. Use this information to then adjust needle angulation and/or depth.
CSF will freely flow from a C1-2 puncture. DO NOT INJECT if poor CSF flow is obtained. You may be only part way through the arachnoid membrane. Try advancing a millimeter at a time.
If you get bloody fluid and/or the patient complains of sudden pain down the spine or extremities, you may have HIT THE CORD. DO NOT INJECT! PULL THE NEEDLE BACK A LITTLE until you get free, clear CSF flow!
Inject the contrast under periodic fluoro. Avoid the heavy foot.
CALL THE ATTENDING TO NOTIFY YOU ARE BEGINNING THIS STEP!!! This is important, because by waiting for the Attending to arrive and supervise the actual injection, the Attending can quickly intervene if a mixed injection is suspected.
Draw up more contrast than you need. Remove any bubbles from the syringe and connecting tubing. Attach the connecting tubing to the spinal needle hub CAREFULLY USING BOTH HANDS FOR NEEDLE SUPPORT. Inject slowly. Use 10 ml of 300 concentration contrast for thoracic or cervical myelograms performed via lumbar puncture or for C1-2 puncture.
For a lumbar puncture, inject slowly and try to pool the contrast in the mid lumbar canal with minimal turbulence to reduce dilution.
For a C1-2 puncture, quick "puffs" of contrast purposely create turbulence and give better mixing of contrast to better surround the cervical cord with contrast.
Fluoro frequently when first injecting. You want to detect a mixed injection as early as possible. If after 3-5 mlís you are concerned about a mixed injection, then STOP! Get a cross table lateral and call the attending Neuroradiologist or fellow for consultation.
If the contrast is in the subarachnoid space it will disperse then collect in a somewhat central pool. A mixed injection will often collect off to one or both sides in a more irregular pattern.
After all the contrast is in, pull the needle out. It wonít hurt, and may help, if you take the time to put the stylet back in the needle before you pull it out.
Pull the drapes off the patient and image intensifier. Put a bandaide on the patientís back.
Preserve the patientís dignity by closing up their gown and/or trowsers.
MIGRATING THE CONTRAST TO THE CERVICAL SPINE.
Prone or Supine Technique: The beauty of this technique is that the contrast should pool in the cervical region just caudal to the needle and give superb contrast density. However, you may need to change the table tilt, putting the patient feet down/head up to assure contrast doesnít dump into the cranial subarachnoid space.
Lateral Decubitus Puncture Technique: With the needle in the dorsal C1-2 subarachnoid space while the patient is still decubitus, replace the stylet. Now with the help of at least 2 others, you need to log roll the patient to the prone position. YOU MUST ASSUME RESPONSIBILITY FOR PERSONALLY STABILIZING THE HEAD AND NECK during the roll. Have the other two helpers lift the patientís shoulders and pull the down side arm through, as you keep the head & neck aligned during the roll. (Personally, I think this is one of the scariest maneuvers in Neuroradiology.)
Once in the prone position, proceed with injection as per the Prone Technique.
This is an art! How do you get all the contrast from the lumbar to the cervical location? It is not as easy as it looks. (Note: This can be a very dynamic process requiring quick observation and changes of tilt and patient rotation! You also have to fluoro back and forth over the cervical, thoracic and lumbar areas rapidly to assess change of contrast position.) Before you start, make sure you have moved the table so that the fluoro tower can cover the cervical spine. CAUTION!: Make sure you donít hit the patientís head with the tower, which is closer to the tower than the C-spine with neck in extension. You may use the towerís vertical lock to prevent this.
Double check that the foot restraints are attached solidly to the table and the handles are located where the patient can comfortably grasp them.
Slow Tilt Method: (Great for patients with straight thoracic spine). Position the patient with the NECK in MAXIMAL EXTENSION for that patient. (Note: This creates a cradle for the contrast to collect.) Having a good sized pillow/bolster under the abdomen will reduce the lumbar lordosis and further improve the drainage of contrast from the lumbar spine. Put a couple of folded towels under the chin. ADMONISH THE PATIENT NOT TO MOVE FROM THIS POINT FORWARD or the exam may be ruined. Slowly tilt the table and eyeball the appropriate tilt necessary to get the contrast flowing north. Repeatedly fluoro first over the C-spine and then down the spine to quickly assess progress of contrast flow. Once you see contrast spilling over the upper thoracic spine into the cervical spine, TILT NO FURTHER! Be patient and let the contrast collect. When most of the contrast has arrived, flatten the table back to neutral position.
Fast Tilt "Avalanche" Method: (Requires a patient with excellent extension of the neck and/or a probable high grade compression of the C-spine, which will act as a temporary "barrier" to prevent the cascading contrast from spilling into the cranial cavity.) Quickly tilt the patient 30-45 degrees head down, watching the C-spine under AP fluoro. As soon as the contrast has dumped into the C-spine, quickly flatten the table into neutral postion.
Prone Oblique Method: (Good for patients with mild to moderate thoracic kyphosis.) Put the patient in the "G.I. position" (Prone, LPO 20-30 degrees). Towels under chin with head remaining somewhat perpendicular to table surface with neck in maximal extension. Slowly tilt and fluoro as per Slow Tilt Method.
Lateral Decubitus Method: (For patients with moderate kyphosis of the thoracic spine. Usually used when you realize too late that you wished you had done a C1-2 puncture.) Inject the contrast in the prone position. Pull the needle out of the L-spine. Log roll the patient 90 degrees into the lateral decubitus position. (Note: If the patient has a thoracic scoliosis, put the convex side down, to facilitate contrast movement.).
To prevent contrast from dumping into the cranial cavity, you MUST TILT THE HEAD AWAY FROM THE TABLE SURFACE! Place enough towels or large pillow to create a cradle for the contrast to collect. Only then, SLOWLY tilt the patient head down using the now lateral table fluoro to gauge contrast progress into the cervical region.
Now with the help of at least 2 others, you need to log roll the patient to the prone position. YOU MUST ASSUME RESPONSIBILITY FOR PERSONALLY STABILIZING THE HEAD AND NECK during the roll. Have the other two helpers lift the patientís shoulders and pull the down side arm through, as you keep the head & neck aligned during the roll.
Filming the Cervical Myelogram
Check to make sure the LEFT or RIGHT marker is visible on the fluoro screen.
The are many "right" ways to film the myelogram. Here is my method:
1. AP SPOT FILMS:
A. AP prone table flat. This view gets the mid & lower cervical canal. (SHOOT THIS AS SOON AS YOU GET THE CONTRAST WHERE YOU WANT IT! THIS IS THE MOST DENSE THE CONTRAST WILL EVER BE! CONTRAST QUICKLY DILUTES OVER THE NEXT FEW MINUTES. THE CLOCK IS TICKING!) You have about 5-10 minutes of working time before the contrast density gets too dilute!
B. AP (Optional) Chin Drop method: When someone can really extend the neck, the disadvantage is the occiput now covers the upper 1/3 of the C-spine. You can get 1-2 additional vertebral levels higher exposure by COACHING the patient to SLOWLY PULL the chin down toward the chest while you fluoro. As soon as the bottom of the occipital bone superimposes with the bottom of the mandible, STOP THE PATIENT. Quickly shoot a full AP neck, then instruct the patient to reverse and re-extend the neck. (You may have to get up at the head of the table to gently help the patient do this.)
C. Coned down (auto coning OFF) AP foramen magnum. Center on odontoid. Use a small, SQUARE collimated format to put the phototimer over the occipital region for proper exposure.
NEVER, NEVER, EVER, EVER LEAVE THE CERVICAL MYELOGRAM PATIENT ALONE IN THE ROOM DURING THE FILMING & DEVELOPING! They will usually be moderately uncomfortable in this position and will move the first chance they get. Constant vigilance and coaching is necessary by you or the technologist while you await the processing of the lateral films.
2. TECHNOLOGIST "OVERHEAD" VIEWS
The lateral views are often the most important view after the AP view. (I prefer to do the spot film oblique views last, since they are the least important.)
Ask the technologist NOT to MOVE THE PATIENT or the TABLE POSITION. Changing table position may result in contrast dumping cranial or caudal!
Request that the technologist shoot the films in the following order and have someone run the 2 lateral views while they set up for the PA view. This maximizes the time necessary to assess the quality of the lateral exposures.
A. Cross Table Lateral
B. Cross Table Swimmers
C. PA Overhead
DO NOT PROCEED until you are satisfied that the LATERALS ARE PROPERLY EXPOSED.
3. OBLIQUE SPOT FILM VIEWS: (I do the spot film oblique views last, since they are the views MOST likely to result in contrast DRAINING AWAY from the C-spine! They are supplemental views, compared with the AP and cross table lateral views)
Two right (RPO) AND two left (LPO) prone shallow obliques.
Unlike the lumbar roots, the CERVICAL roots exit the spinal canal at a much shallower angle. Use only around 10 and 15 degree rotation. Any more and you obscure the root sleeves.
I assist the patient by walking to the head of the table. Leaving one arm by the side, I bring up the other arm and place the hand at shoulder level I ask the patient to do a unilateral rotating push-up while I simultaneously hold and position their head and C-spine in the preferred obliquity. I reverse the position for the opposite obliques.
4. If there is a block to contrast movement, you can try several things.
Wait 1-5 minutes with the patient tilted steeply.
Have the prone patient relax out of extension into a neutral position with the chin toward the chest.
Do the oblique filming maneuvers and then repeat AP and LATERAL views. (Often there is more space for contrast to flow laterally, while the patient is in an oblique position, than there is anterior or posterior to the compressed cord in the flat prone position.)
Turn the patient decubitus or even supine.
Rule: Now you must process and CHECK ALL THE FILMS done so far for quality control. Repeat unacceptable films!
Ask yourself this question: "Have I seen all the cervical roots?" If you havenít, then go back and get some more films until the answer is "YES". You may now move the patient to the stretcher to go to CT.
PUT THE PATIENT FLAT (SUPINE) ON THE GURNEY WITH A SMALL PILLOW UNDER THE HEAD. Slide the patient from the fluoro table to the stretcher. DO NOT let the patient SIT UP. You want to keep the contrast concentration maximal in the C-spine region, until the patient has finished the CT.
After the CT is completed, THEN INSTRUCT the patient to keep the HEAD of BED up 30 Ė45 degrees for the next 4 hours to keep contrast concentration maximal in the lower spine and minimize concentration intracranially.
Label the pedicles on all the films and the vertebral bodies on the lateral film.
This allows you to easily assess the specific roots and write a quick note.
Choose the levels you want to scan with the postmyelogram CT.
It is your responsibility to go to the CT scanner and write down specifically what levels and angles you want the techs to do.
Please bring a LATERAL C-SPINE FILM WITH THE DESIRED LEVELS DRAWN ON THE FILM!
SHOW it to the CT Technologist to assure there is no confusion about which levels you want scanned.
Minimum 3 levels: C5-6, C6-7, C7-T1.
Additional levels if abnormalities seen on the lateral or AP/oblique films.
1.5-2.0 mm sections at 2 mm intervals.
Multiple angles: Pedicle to pedicle contiguous sections parallel to each respective disk.
Write the protocol desired on the CT requisition and discuss with the CT tech.
One single angle if you want to reformat in sagittal or coronal planes: Spondylolisthesis, other subluxations or intradural mass. Then additional 1-3 cuts through each disk parallel to each disk.
Transport patient lying flat on the stretcher, with the head up on a pillow. Avoid putting the patient upright and diluting the cervical contrast.
Write a Progress Note and Post-Myelogram orders.
Progress Note: Briefly state the preliminary findings.
1. Bed rest X 4-6 hrs (Discretion of Attending) with head of bed up 30-45 degrees.
2. Bathroom priveledges with attendant.
3. Encourage p.o. fluids and regular diet.
4. Pain reliever of choice PRN headache.
5. Discharge after 4 hrs (If outpatient)
6. No Phenothiazines