Operative Planning

• Ninety-five percent oxygen/5% carbon dioxide spirometry: patients with decreasing minute volume are at increased risk of postoperative sleep apnea
  
• Pulmonary function tests if suspect contralateral diaphragmatic dysfunction

Equipment

• Basic tray
  
• Radio-frequency lesioning generator
  
• Fluoroscopy suite
  
• May also be done under computed tomography (CT) guidance

Operating Room Set-up

• Headlight
  
• Loupes
  
• Bipolar cautery and Bovie cautery

Anesthetic Issues

• Local anesthesia
  
• Gentle sedation only: patient must be highly cooperative

Positioning

• Patient supine
  
• Level of mastoid process maintained at same height as acromioclavicular joint

Planning of Sterile Scrub and Preparation

• Routine sterile prep and drape of lateral neck contralateral to patient’s pain, from above mastord to mid-cervical region

• One percent lidocaine without epinephrine infiltrate into the region contralateral to the pain, 1 cm inferior to the mastoid tip
  
• A horizontal 18-gauge spinal needle is inserted to the midpoint between the anterior rim of the C2 spinous process and the posterior rim of C2 body directed at the anterior part of the spinal cord (on CT guidance using 1 mm slice thickness).
  
• The needle trajectory is maintained rostral to the lamina of C2 to prevent puncture of the nerve.
  
• Ideal position is nearly perpendicular to the spinal cord
  
• The dura is penetrated; 2 mL of cerebrospinal fluid (CSF) is aspirated and mixed with 2 mL of Pantopaque contrast, and the mixture is injected into the subarachnoid space (alternatively, if using CT guidance, contrast may be injected via lumbar puncture 20 minutes prior to procedure).
  
• The radio-frequency needle electrode is advanced to a point immediately anterior to the dentate ligament.
  
• As the needle penetrates the spinal cord, the impedance should jump to 1200 to 1500 ohms (~400 ohms in the CSF).
  
• Stimulate at 100 Hz for localization; patient should report contralateral tingling at a threshold under 1 V.
  
• Lesion is not performed if muscle tetany is detected
  
• To begin the radio-frequency lesioning, have the patient contract the ipsilateral hand.
  
• The voltage is increased from zero; the voltage is reduced if hand twitching is detected.
  
• Lesioning maintained for 30 seconds
  
• Repeated to perform a second lesion
  
• Patient examined for regions of anesthesia
  
• Supine position maintained for 24 hours

Equipment

• Laminectomy tray
  
• Padded cerebellar headset

Operating Room Set-up

• Headlight
  
• Loupes
  
• Bipolar cautery and Bovie cautery

Anesthetic Issues

• General anesthesia
  
• Intravenous antibiotics (cefazolin 2 g) should be given 30 minutes prior to incision

• Patient prone
  
• Neck flexed to open interlaminar space (be careful to avoid too much flexion to decrease tethering of the cord)
  
• Head lowered to prevent aspiration of air into the subarachnoid space

Sterile Scrub and Prep

Technique

• Midline incision from the inion to C3
  
• Unilateral subperiosteal dissection of muscles from posterior rim of the foramen magnum, C1 lamina, and C2 lamina
  
• A self retaining retractor inserted
  
• Interlaminar space between C1 and C2 identified
  
• Small inferior C1 and superior C2 hemilaminotomies performed
  
• Ligamentum flavum incised
  
• Dura incised between C1 and C2 with a no. 11 blade along lateral third of hemilaminotomy; be careful of the epidural veins in the lateral gutter
  
• Dural leaflets tacked up with sutures
  
• Arachnoid opened, dentate ligament identified, and its lateral dural attachment incised
  
• The dentate ligament used to rotate cord with silk sutures
  
• No. 11 blade used to incise the cord anterior to the dentate ligament to a depth of 5 mm (apply bone wax to the premeasured depth on the blade)
  
• Patient examined for regions of anesthesia

Closure

• Watertight dural closure
  
• Layered muscle, fascial, and skin closure

• Postoperative analgesics as necessary
  
• Taper narcotics used for the chronic pain