Minimally Invasive Posterior Cervical Foraminotomy and Microdiscectomy

Minimally invasive posterior cervical (MIPC) approaches are safe and effective procedures that can be used to treat clinically significant foraminal stenosis resulting from lateral disc herniation or osteophytes. Symptoms improve in more than 90% of patients who undergo the procedure. Until the late 1950s, this was the predominant approach used in the treatment of herniated cervical discs. In 1958, however, Cloward (1958) introduced an anterior approach to cervical discectomy called anterior cervical discectomy and fusion (ACDF), and the popularity of this technique grew as modifications to the technique made it safe and easier to perform. One of the primary advantages of MIPC approaches, however, is preservation of the motion segment.

Numerous series show that patients achieve good relief from their symptoms with the ACDF approach. However, despite these advantages, ACDF is associated with the risk of numerous complications, including recurrent laryngeal nerve injury, dysphagia and speech dysfunction, esophageal injury, and airway compromise, as well as injury to the carotid artery and jugular vein. In addition, ACDF has been implicated in both radiographic and clinically significant adjacent segment degenerative disease, as well as altering the native biomechanics of the cervical spine.

Because MIPC approach avoids a complete discectomy and fusion, it remains a viable option in the treatment of lateral soft discs or osteophytes in the cervical region, and superb decompression of the lateral recess and neural foramen has been well documented. ^{, , , , , ,} MIPC offers direct visualization of the exiting nerve root and avoids fusion, which is not the case with ACDF.

We have previously described our technique for performing an MIPC approach. This approach is best suited for patients with refractory unilateral radicular symptoms secondary to foraminal stenosis and or lateral disc herniation ( Fig. 136.1 ).

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(A) Axial T2-weighted magnetic resonance image of the C3–4 level showing a left lateral disc herniation (arrow) causing foraminal stenosis. (B) Sagittal and corresponding (C) axial computed tomography (CT) myelogram showing a C5–6 soft disc herniation (arrow) causing foraminal stenosis and left C6 radiculopathy. The CT myelogram is an excellent study for visualization of the neural foramen and determining whether lateral disc herniations are calcified or not.

Lateral soft disc herniations can be treated using the MIPC technique by performing a small resection of the superior medial pedicle, thereby allowing access to the herniated disc fragment. Although this technique was described in the past using the endoscope, the senior author has found the microscope offers a number of advantages over the endoscope. The microscope affords three-dimensional visualization of the anatomy as opposed to endoscopes, which are typically two-dimensional. Other advantages of using the microscope over the endoscope include familiarity among neurosurgeons and improved optics for enhanced visualization of the operative field.

Patient Positioning

Following routine presurgical evaluation and medical clearance, the patient is brought to the operating suite and general endotracheal anesthesia is induced. The patient is not given paralytics to visualize any muscular contraction resulting from nerve root manipulation. We routinely perform somatosensory evoked potentials to monitor the intraoperative integrity of the spinal cord. Electromyography of appropriate muscle groups can also be performed for additional intraoperative feedback. Preoperative antibiotics—either cefazolin or clindamycin, if the patient has a penicillin allergy—are administered 30 minutes prior to skin incision. Intravenous steroids are not routinely administered, and as a result of the brevity of the procedure, a Foley catheter is generally not needed.

With the patient initially in the supine position, the head is affixed to the Mayfield head holder, and the body is gradually brought to a semi-sitting position such that the knees are level with the heart. The Mayfield adaptor is attached to the table between the hips and the knees and arched back as necessary to accommodate the patient’s body habitus, connecting to the Mayfield head holder. Care is taken to maintain the neck in a comfortable, neutral position. The surgeon should be able to pass two fingers below the chin to assure adequate venous drainage via the jugular veins. The arms are folded and secured across the chest or supported at the sides; pressure points are padded to prevent nerve palsies and pressure sores ( Fig. 136.2 ).

Precordial Doppler monitoring is used to monitor air emboli in the right atrium; a central venous catheter is usually not necessary because of the brevity of the procedure and its minimal blood loss. The midline of the patient is marked by palpation of the cervical vertebrae spinous processes before draping the patient (see Fig. 136.2C ).