Historical notes

The first recognized case of cervical radiculitis caused by herniation of the nucleus pulposus was operated on by Professor Angelo Chiasserini, one of the founders of Italian neurosurgery, in January 1937. Previously, cases of cervical ‘chondromas’ had been described but the specific pathophysiology of discogenic cervical radiculitis was not recognized.¹

Cervical disc disease was initially treated by posterior foraminotomy or discectomy, similar to that which had already been performed in the lumbar region.

The advent of the Smith—Robinson technique, later popularized with methodology by Cloward, led to a dramatic shift of the direction of treatment for cervical radiculopathy from posterior to anterior. Indeed, Angevine et al. reported that the United States national rates for cervical discectomy with and without anterior fusion had changed dramatically during the 1990s with a marked increase in the inclusion of a fusion procedure.² There was a significant geographic distribution in the rate of fusion for cervical disc disease, with the South having the highest fusion rate. Although the rate of surgery for cervical disc disease did not increase significantly during the 1990s, the rates of fusion procedures did rise significantly.

Indications

The reasons for surgery for cervical radicular pain are:

The nonoperative measures which usually precede surgery for cervical radiculopathy are described elsewhere in these pages, and will not be discussed at this point.

The indications for treatment of cervical radiculopathy for weakness vary somewhat with the nerve root involved. Generally speaking, a surgeon is more aggressive with C5 radiculopathy, during which paralysis of the deltoid muscle could evolve and which ultimately is disabling. Similarly, surgery for a C8 radiculopathy is generally not delayed because intrinsic hand muscle weakness can essentially disable fine movement hand functions. However, C6 and C7 motor deficits are less disabling.

Furthermore, surgery for cervical radiculopathy depends on the acuity of the onset and the severity. Neurological deficit of a mild to moderate degree, which has evolved over several days or weeks, can be treated nonoperatively, at least in its initial phases. Acute cervical radiculopathy with profound weakness is generally considered an urgent surgical matter, and nonoperative measures are likely to be ineffective. With acute and profound weakness, there is only a small window of time during which decompression can be effective before permanent neural damage evolves. In view of the relative safety of these operative procedures with modern techniques, permanent loss of cervical nerve root motor function, particularly C5 and C8, should not be risked by attempts to relieve the syndrome with nonoperative measures. Generally speaking, nonoperative measures are more effective for pain relief than for relief of neurological deficit. Although spontaneous improvement in pain may occur, patients could be left with permanent neurological deficit if treatment is inordinately delayed.

Contraindications

There are definite and, in the author’s opinion, controversial contraindications to surgery.

The definite contraindications, of course, are patient’s ill health which will not tolerate an operative procedure. Another contraindication for surgery for improvement of strength would evolve if the patient had profound weakness for a long interval of time, with atrophy, as a result of which permanent nerve damage is suspected. Obviously, cervical nerve root decompression would not be effective in patients with permanent injury. The patients may request that something be done to help them regain their strength, but after a long duration of profound weakness in any cervical nerve root, the surgeon should either refuse the operation or at least indicate to the patient that recovery is unlikely, depending on his assessment of each individual case.

The relative contraindications, as discussed below, are, in the author’s opinion, important but somewhat controversial.

Posterior cervical nerve root decompression

In the author’s opinion, this highly effective operation is dramatically underused in the United States for reasons which remain mysterious. The posterior operation provides nerve root decompression, long-term relief of radicular symptoms, without the necessity to fuse the cervical spine. The complication rate is substantially less than anterior discectomy. The procedure, however, cannot be used for midline cervical disc herniations where a spinal cord compression is the principal pathology (Figs 60.1–60.8).

Fig. 60.1 Posterior cervical foraminotomy. Axial view of cervical spine showing disc herniation. The shaded area shows the extent of the foraminotomy and medical facetectomy.

Fig. 60.2 Posterior cervical foraminotomy. The patient is placed in the prone position with the cervical region elevated above the level of the right atrium to reduce venous pressure. Head fixation is by Mayfield tongs.

Fig. 60.3 Posterior cervical foraminotomy. The extent of the ‘keyhole’ prior to foraminotomy.

Fig. 60.4 Posterior cervical foraminotomy. Right-angle rongeur beginning the ‘keyhole’ opening.

Fig. 60.5 Posterior cervical foraminotomy. A probe is inserted into the foramen to determine its degree of stenosis.

Fig. 60.6 Posterior cervical foraminotomy. When the foramen is tight, the overlying bone is drilled first until it is thin and then chipped away with a right-angle curette. The right-angle rongeur should not be forced through the foramen in order to decompress the root.

Fig. 60.7 Posterior cervical foraminotomy. Overlying the nerve root are veins which can be cauterized in order to visualize the dura.

Fig. 60.8 Posterior cervical foraminotomy. Under microscopic guidance, the nerve root is gently retracted to expose the posterior surface of the bulging or extruded disc, which is then removed with fine instruments such as a Rosen knife or microsurgical Penfield elevator.

The patient is placed on the operating table in a kneeling position so that the cervical spine is above the right atrium. This requires tilting the table in a reversed Trendelenburg fashion to an appropriate distance, and that the patient be adequately fixated to avoid sliding during this table positioning.

For a single-level nerve root decompression, an incision of approximately 2.5 cm is made over the affected spinous processes. The level is confirmed radiographically, intraoperatively. The cervical muscles on one side are dissected free from the lamina and held in place with the retractor. Under microscopic control, the inferior margin of the lamina of the superior vertebra and the superior margin of the lamina of the inferior vertebra are removed with drills or rongeurs so that the top of a ‘keyhole’ is visualized. The bottom of the keyhole, of course, is the bony structures over the affected nerve root. Under microsurgical control, the dorsal portion of the intervertebral foramen through which the affected nerve root passes is drilled down to a thin eggshell which is then removed with a small curette. Alternatively, a small Kerrison rongeur can be used to complete the foraminotomy without compressing the underlying nerve root. At the end of this procedure, one should easily be able to pass an instrument through the foramen and determine that there is no pressure on the nerve root. This dissection can be carried out pedicle-to-pedicle and generally involves only the medial half of the facet joint. As such, instability has not been demonstrated when the procedure is performed unilaterally. In young patients with an acute history, and in preoperative studies, where one suspects a free disc fragment, it is possible to remove the extruded disc material to obtain even more immediate relief. Generally, it is necessary to coagulate the overlying venous cuff in order to expose the disc herniation. When the herniation is incised there can be a spontaneous extrusion of the disc material, and in the author’s experience, this generally portends an excellent result with immediate relief of arm pain. When the pathology is ‘hard,’ that is secondary to an osteophyte, a wide decompression as described above is sufficient to relieve the patient’s symptoms permanently. It is not necessary to attempt to flatten, remove, or otherwise manipulate the anterior osteophytes since the pathology is apparently a ‘sandwich’ effect and removing one portion of the sandwich on either side adequately releases the pressure of the foraminal contents. As discussed elsewhere in this book, this procedure can be performed using even more minimally invasive techniques. Narrow retractors which access the foramen by splitting the paraspinous muscles through an even smaller incision (1.5 cm) have facilitated a less painful recovery. There are several advantages to this approach over the anterior operation specifically for cervical radiculopathy. First of all, several roots can be examined, and it is frequent that multiple roots are involved, without fusing multiple spine segments and thereby applying undue stress on the remaining non-fused motion segments. Secondly, the mechanics of the spine are not altered by surgical immobilization. Furthermore, the risk to the esophagus, larynx, and adjacent structures is eliminated because the approach will only involve the paracervical musculature before the level of the pathology is reached.