Indication
- Unilateral pain below ≈ C4–5 in a terminally ill patient.
Mech
- Lesion made in the Lateral spinothalamic tract
- Located anterior to the dentate ligament
Technique
- Radiofrequency current is used to lesion the lateral spinothalamic tract
- Patient does not need to be NPO.
- Usual pain medications should be given.
- The patient must be awake and cooperative (any movement with the needle in the cord may lacerate the cord);
- However, one may give e.g. hydroxyzine 50mg IM on call to procedure for relaxation.
- Done under local or under GA
- Fluoroscopic or CT guidance.
- Fluoroscopy:
- Head placed in a Rosomoff headholder with the height adjusted to keep the mastoid process in the same horizontal plane as the acromioclavicular joint.
- Working on the side contralateral to the pain, local anesthetic without epinephrine is infiltrated 1cm caudal to the mastoid tip.
- An 18 gauge lumbar puncture needle is inserted perfectly horizontal aiming halfway between the posterior margin of the body of C2 and the anterior portion of the C2 spinous process.
- Stay rostral to the C2 lamina to avoid the nerve (which is painful). The dura will be penetrated at about the time that the tip of the needle is approximately even with the midline of the odontoid process on AP fluoro.
- A few ml of CSF are aspirated and shaken in a syringe together with a few ml of Pantopaque®, and several ml of the mixture are injected into the subarachnoid space under lateral fluoro guidance (note: Pantopaque is no longer available, and water soluble agents are less effective).
- A needle endoscopic technique may be able to localize the spinal cord anterior to the dentate ligaments.
- Some dye will layer on the anterior cord, some on the dentate ligament, and most in the posterior thecal space.
- The dye will only stay momentarily on the dentate ligament, thus be ready to immediately advance the needle just barely anterior to this while monitoring the tip impedance, which will jump from ≈ 300–500 Ω (ohms) in the CSF to ≈ 1200–1500 Ω as the spinal cord is penetrated.
- Stimulation at 100Hz should produce contralateral tingling at a threshold of≤ 1 volt.
- No motor response should be elicited with 100Hz in the spinothalamic tract, and if muscle tetany occurs, lesioning must not be performed.
- If tingling is in the arm, lesioning will usually render from the arm and below analgesic.
- If tingling is in the lower extremity it will render only that limb analgesic.
- Stimulation at 2Hz should produce ipsilateral twitching of the arm or neck at ≈ 1–3 volts.
- Radiofrequency lesioning is performed for 30 seconds while the patient sustains contraction of the ipsilateral hand and the voltage is gradually increased from zero.
- Any twitching of the hand is an indication to back down on the voltage.
- A second lesion is performed in the same region and is usually less painful.
- The appropriate body area is then checked for analgesia to pinprick. If the procedure is performed satisfactorily, an ipsilateral Horner syndrome usually occurs.
Post op care
- Patient is kept supine for 24 hrs to prevent “spinal” (post-LP) headache.
- Pain medication appropriate to postoperative management is prescribed.
- If successful, one can rapidly stop the narcotics for the primary pain; withdrawal syndromes occur only rarely.
Complications
Complication | Frequency |
Ataxia | 20% |
Ipsilateral paresis | 5% total 3% permanent |
Bladder dysfunction | 10% total 2% permanent |
Postcordotomy dysesthesia | 8% |
Sleep induced apnea | 0.3% unilateral cordotomy 3% bilateral cordotomy |
Death (respiratory failure) | 0.3% unilateral cordotomy 1.6% bilateral cordotomy |
Outcome
- In experienced hands,
- 94% will achieve at least significant pain relief at the time of hospital discharge.
- The level of analgesia falls with time.
- At 1 year 60% will be pain free,
- At 2 years this will be only 40%.
- CSF leakage
- Spontaneously stop
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