Cervicothoracic radiculopathy treated using posterior cervical foraminotomy/discectomy

Transcription

1 J Neurosurg (Spine 2) 98: , 2003 Cervicothoracic radiculopathy treated using posterior cervical foraminotomy/discectomy JAMES S. HARROP, M.D., MARCO T. SILVA, M.D., ASHWINI D. SHARAN, M.D., STEVEN J. DANTE, M.D., AND FREDERICK A. SIMEONE, M.D. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania Object. The authors conducted a study to identify the effectiveness and morbidity rate associated with treating cervicothoracic disc disease (radiculopathy) via a posterior approach. Methods. Nineteen patients underwent posterior cervicothoracic laminoforaminotomy during a 5.6-year period. Medical records, imaging studies, office charts, hospital records, and phone interview data were reviewed. Specific information analyzed included patient demographics, side of lesion, and conservative treatment, symptoms, and preand postoperative pain levels. Pain was rated using a visual analog scale and classified into a radicular and neck component. Data in 19 patients (seven women and 12 men) who underwent 20 procedures (one patient underwent separate bilateral foraminotomies) were analyzed. The mean patient age was 54.8 years (range years), and the follow-up period ranged from 23 to 62 months. Symptom duration ranged from 1 to 14 months (mean 3.4 months) and consisted of weakness, numbness, and painful radiculopathies in 11, 16, and 20 cases, respectively. Motor weakness was identified in 11 of 19 patients (mean grade of 4.35), and postoperatively strength normalized in eight of 11 (mean grade of 4.79). The improvement in motor scores was significant (p = 0.007). Pain was the most common presenting symptom. Preoperative radiculopathies were rated between 0 and 10 (mean 7.45), and postoperatively scores were reduced to 0 to 3 (mean 0.2) which was significant (p ). Preoperative neck pain was rated between 0 and 8 (mean 2.55), and on follow up ranged from 0 to 2 (mean 0.5), which was also significant (p = 0.001). Conclusions. Posterior cervicothoracic foraminotomy was a safe and effective procedure in the treatment of patients with laterally located disc herniations. KEY WORDS cervicothoracic spine foraminotomy posterior approach radiculopathy discectomy A NTERIOR cervical decompression with fusion has become the chosen surgical therapy for the treatment of cervical radiculopathy after failure of conservative therapy. An anterior cervical exposure is more difficult at the extremes of the cervical spine. In particular, the caudal cervical spine is confined by large vascular structures, the esophagus, pharynx, trachea, sternum, and the thoracic rib cage. This region is also the transition zone from the thoracic kyphosis to the cervical lordosis, making bone fusion difficult because of a biomechanical disadvantage. An alternative treatment option in this region is a posterior cervical foraminotomy alone or with a concurrent discectomy. To access the efficiency and safety of such approach, we retrospectively analyzed data obtained in a relatively large group of patients with cervicothoracic radiculopathy in whom surgery was performed via a posterior approach only. J. Neurosurg: Spine / Volume 98 / March, 2003 Clinical Material and Methods Patient Population Nineteen patients were treated with posterior laminoforaminotomy for either lateral disc herniation or foraminal stenosis between July 1995 and February All patients were evaluated by the senior authors (F.A.S. and S.J.D.) and were offered surgery when clinical symptoms correlated with findings on appropriate neuroimaging studies and after conservative therapy failed or when they presented with acute motor loss of hand function. During the initial evaluation, if myelopathy due to congenital cervical stenosis with a lordotic cervical spine was found, cervical laminectomy and concurrent foraminotomy were performed. No patients had sustained work-related injuries, were involved in Worker s compensation cases, or had legal representation concerning their lesions. All medical records and imaging studies were reviewed. Data were also collected through office charts, hospital records, and phone interviews. Specific information analyzed included patient demographics, side of lesion, conservative therapy regimen, symptoms (numbness and weakness), and pre- and postoperative pain levels. Pain was assessed using a visual analog scale. Pain was also divided into a radicular and isolated neck component. Muscle strength was graded using a six-point (0 5) scale. 12 Operative reports were also reviewed to determine 131

2 J. S. Harrop, et al. side of operation, number of foramina decompressed, and whether a foraminotomy or discectomy was performed. Operative Technique General anesthesia was induced, and a Mayfield threepin head holder was applied. After positioning the patient prone on laminectomy rolls, the head was secured to the bed in a slightly flexed position. The knees were flexed and supported caudally, allowing the operating table to be placed at an approximately a 30 incline. A detailed description of the positioning has been previously reported. 19 A midline incision (~2.5 cm/level) was made over the affected interspace, and the paraspinal muscles were dissected in a subperiosteal manner. Attention was paid to preserving the interspinous ligaments. Intraoperative radiography confirmed the correct anatomical localization. A key-hole laminotomy was then made, which permitted palpation of the superior and inferior pedicles. The operating microscope was brought into the surgical field, and a high-speed drill was used to thin the bone over the exiting nerve root, prior to its removal by using a curved curette. Approximately one third of the medial facet joint was removed, leaving at least 50% in place. After the vascular cuff was identified, the sleeve was coagulated and divided using microsurgical technique. Once the vascular cuff was opened, the microscope provided clear visualization of both the motor and sensory divisions of cervical nerve. With microdissection, the lateral disc herniation was identified. If the herniated disc was soft, then the posterior ligament was opened and the lesion removed. The decision to open the cuff was made intraoperatively after the osseous component of the foraminotomy was performed. In cases of large disc herniations, the cuff was opened; in smaller ones, palpation of the nerve intraoperatively determined if the cuff required opening. Once the vascular cuff was opened, the nerve was gently retracted cephalad with a Rhoton No. 6 Penfield knife. Using a No. 11 blade, the disc was incised and removed using a Decker pituitary and rosen knife. When the nerve was confirmed to be decompressed, the wound was closed in layers. Statistical Analysis Statistical analysis was performed using univariate methods (chi-square, Fisher exact, and t-tests). A probability value of 0.5 was set for statistical significance. All calculations were performed using the Statview statistical computer software package (SAS, Cary, NC). Literature Review A detailed literature search was performed of the Medline database (1966 present). The following text words were used: cervicothoracic, cervical spine, foraminotomy, and discectomy. The results of these searches, along with the key references from the identified articles and known references on the subject material were reviewed. Results Twenty-one patients who were treated for degenerative cervicothoracic disease were identified (Table 1). Two patients were excluded from analysis because medical and operative records were deficient. Data in the remaining 19 patients (7 women, 12 men) who underwent 20 procedures (in one patient bilateral foraminotomies were performed at separate intervals) were analyzed. The followup period ranged from 17 to 62 months. Patients ranged in age from 38 to 73 years (mean 54.8 years). Eleven patients suffered left-sided radiculopathies and nine right-sided lesions. Onset of symptoms varied between 1 and 14 months (mean 3.4) and consisted of weakness, numbness, and painful radiculopathies in 11, 16, and 20 of 20 cases, respectively. Numbness was localized to the fourth and fifth digits; third, fourth, and fifth digits; and second, third, fourth, and fifth digits in 11, two, and one of 16 patients, respectively. The paresthesias resolved in nine of 16 patients. Seven patients suffered persistent numbness after the decompression, but their status was improved over preoperative condition. The two patients with the most severe numbness also suffered severe motor weakness. Motor weakness (mean score of 4.35) was initially identified in 11 of 19 patients, and noted to be immediately ( 1 week) and completely improved postoperatively in eight (73%) of the patients with weakness (mean score of 4.79) (p = 0.007). Of the four patients with persistent weakness, a delayed recovery occurred in two. The two patients with lingering weakness initially exhibited antigravity strength (Grade 3/5), and this improved in one to Grade 4/5 strength. No patient experienced greater weakness as a result of the decompressive surgery. In seven patients appreciable atrophy of the first dorsal interosseous muscle was observed. Pain was the most common presenting symptom. Preoperative radiculopathies were rated between 0 (no pain) and 10 (intractable pain), and the mean score was Postoperatively the scores decreased to between 0 to 3 (mean 0.2) (p ). Preoperative axial neck pain was rated between 0 and 8 (mean 2.55), and on follow-up examination ranged from 0 to 2 (mean 0.5) (p = 0.001). Statistical analysis of data regarding the patient s age, sex, level of operative treatment, side, motor status, pain symptoms, atrophy, and conservative treatment regimen compared with operative procedure (a foraminotomy alone or a combined foraminotomy/discectomy) demonstrated no positive or negative predictive factors. There was, however, a correlation between the duration of symptoms and treatment (p = 0.035); the mean presentation prior to surgical intervention for a foraminotomy was 4.9 months whereas it was only 2.1 months for those who underwent foraminotomy and concurrent discectomy. In the present series there were no superficial or deep infections. One patient underwent a second operation performed by a different surgeon 4 years after his previous surgery. This consisted of a four-level anterior C2 5, which was entirely cranial to the original posterior operation from which the patient noted complete resolution of symptoms. The second operation was not performed as a revision surgery but instead for new degenerative symptoms. One of the four patients who underwent a cervical laminectomy, instrumentation-augmented fusion, and concurrent foraminotomies developed a sudden onset of left-hand intrinsic weakness. This occurred 7 days after the original operation. Plain, flexion, and extension radiographs demonstrated no remarkable findings. Cervical 132 J. Neurosurg: Spine / Volume 98 / March, 2003

3 Posterior cervical foraminotomy/discectomy TABLE 1 Summary of data obtained in patients undergoing procedures for cervicothoracic radiculopathy* Pain Score Radicular Neck Motor Score Numbness Case Age (yrs), Duration Lamin- No. Sex Side Level(s) Surgery (mos) Preop Postop Preop Postop Preop Postop Preop Postop ectomy 1 52, F lt C7 T1 disc yes no no 2 51, F lt C7 T1 form yes no yes F rt C6 T1 disc yes no no 3 59, M rt C5 T1 form yes yes no 4 61, M lt C6 T1 form yes no no 5 40, M rt C7 T1 disc yes no no 6 73, F rt C7 T1 form yes no no 7 51, M lt C6 T1 disc no no no 8 73, F lt C7 T1 form yes yes no 9 48, M lt C7 T1 disc yes yes no 10 69, M rt C7 T1 disc yes no no 11 62, M lt C6 T1 disc no no no 12 60, M rt T1-2 disc yes no no 13 55, F rt T1-2 disc no no no 14 58, M lt C6 T1, T-12 form yes yes yes 15 38, F lt C6 T1 disc yes yes no 16 39, M lt C7 T1 form no yes no 17 42, M rt C7 T1 disc yes no no 18 70, M rt C6 T1 form yes no yes 19 44, M lt C5 T1 form yes yes yes * disc = discectomy; form = foraminotomy. myelography and postmyelography computerized tomography scanning demonstrated only thinning of the C-7 nerve root, whereas the C8 T1 nerve roots had no filling defects. The patient underwent surgical reexploration, and no nerve root compression was observed. The patient s hand function completely recovered and the cause of the weakness was proposed to be vascular in nature, related to his underlying small vessel disease secondary to diabetes. All patients underwent clinical and radiographic follow-up examination. Although the follow-up period has been brief, no cervical instability or cervical deformity has been demonstrated in any case. Discussion There have been numerous descriptions of procedures for treating cervical radiculopathy via an anterior 9,10,25,34,35 or posterior 1,7,14,18,19,33 approach. Mixter and Barr 26 first reported the posterior approach for resection of lumbar and cervical disc herniations. Their technique was modified by Scoville, et al., 33 Fager, 14 and Guanciale. 18 Recently, there have been additional variations of these procedures involving use of the endoscope 1,7 or a transpedicular route. 18 Cervicothoracic disc herniations and radiculopathies are uncommon. In several large clinical series authors have reported the incidence to be only between 4 and 7%. 1,33,37 There has been no study to address specifically the surgical treatment of this disorder via a posterior approach. In our study, therefore, we have examined this uncommon condition s symptoms and clinical outcomes and will discuss the advantages of a posterior over an anterior approach in the cervicothoracic spine. J. Neurosurg: Spine / Volume 98 / March, 2003 Symptoms of Cervicothoracic Lesion Acute or intractable pain is the major presenting symptom in patients with a monoradiculopathy. 1,21,27,32,33,37 Most patients in our series suffered painful radiculopathies (19 of 20 cases); additionally patients also presented with concurrent hand intrinsic weakness (11 cases) or numbness (16 cases) due to compression of the C-8 or T-1 nerve roots (Figs. 1 and 2). Axial neck pain was present in the majority of cases but was a minor component (mean score of 2) and was most likely secondary to muscle spasms. The T1 2 disc herniations are extremely rare (Fig. 2). Murphey, et al., 27 noted that these lesions represented less than 1% in their series of 648 patients. These patients, contrary to those with C7 T1 lesions, present with more severe hand intrinsic weakness and less pain. In the present series, all three patients with the T1 2 compression presented with atrophy of the first dorsal interosseous muscle, and the two patients with soft-disc herniations also had a Froment sign. Although others 27 have suggested the presence of a Horner syndrome with cervicothoracic disc disease, no patient in this series sustained appreciable sympathetic dysfunction. Clinical Outcome Our clinical results correlate with those reported in other large series of posterior cervical foraminotomy in which outcome of good/excellent recovery ranged from 90 to 100%. 1,2,21,27,33,36,37 In our series there was a reduction in the radicular component of pain, the most common presenting symptom, from a mean score of 7.45 to 0.2 (p ). Improvement in motor function also occurred, as indicated by a mean increase from 4.35 to 4.79 (p 0.007). Henderson, et al., 21 reported the largest series, 133

4 J. S. Harrop, et al. FIG. 2. Imaging studies obtained in a 55-year-old woman who presented with severe radicular pain and weakness of the right hand intrinsic muscles. Upper: Preoperative sagittal T 2 -weighted MR image revealing a large lateral T1 2 disc herniation (arrow). Lower: Axial images demonstrating a lateral disc protrusion. FIG. 1. Imaging studies obtained in a 52-year-old woman who presented with severe neck and radicular pain. Upper: Preoperative sagittal T 2 -weighted magnetic resonance (MR) image illustrating a large C7 T1 disc herniation (arrow). Lower: Axial T 2 - weighted MR image demonstrating no spinal cord compression and the disc fragment occluding the left C-8 foramen (arrow). accrued during 17 years, consisting of 736 patients (846 procedures); radicular symptoms were relieved in 96% and motor defects were resolved in 98%. In their series, no surgery included removal of the herniated disc, and only foraminotomies were performed. Although the goal of surgery was to treat the radicular pain and motor weakness, there was also a statistical correlation in the reduction of axial neck pain (p = ) from a mean score of 2.55 to 0.5, which is in agreement with our series. Herkowitz, et al., 22 performed the only prospective study, which consisted of 33 patients. Seventeen patients were randomized to undergo an anterior procedure and 16 to a posterior decompression. Although a good/excellent result was associated with 85% of the anterior procedures and only 75% of the posterior foraminotomies, the difference was not statistically significant. The authors should be commended for the study. They concluded, however, that anterior discectomy and fusion is the recommended procedure for the surgical management of a cervical anterolateral disc herniation. This is not supported by the results obtained in our study. Anterior cervical discectomy and fusion also is reported to be associated with excellent relief of postoperative pain and neurological deficits. Gore and Sepic 17 have reported a 96% improvement in symptoms in 146 patients. Disc herniations situated more laterally, however, can be difficult to decompress anteriorly because of limited access and visibility. In an anatomical study, Raynor 30 found that, via a posterior decompression, between 3 and 5 mm of the cervical nerve root can be visualized, whereas only 1 to 2 mm can be appreciated via a standard anterior approach. Additionally, through a posterior approach multiple nerve roots can be decompressed simultaneously without requiring complex cervicothoracic anterior reconstruction. Biomechanical Factors Historically, posterior-approach cervical decompressive surgery has been thought to result in cervical instability and the formation of a kyphotic or swan-neck deformity. This was believed to be the result of excessive resection of the facet joints after laminectomy. Investigators of several in vitro studies have shown that the cervical spine maintains its stability if less than 50% of the facet joint is resected bilaterally after laminectomy. 8,31,38 Zdeblick, et al., 38 demonstrated that with less than 50% resection of the facet joint strain, torsional stiffness, and flexion were maintained. These studies involved bilateral laminectomy and removal of the facet joints, whereas typically in cases of a posterior foraminotomy only a unilateral procedure is performed and only a minor portion of the facet is removed. If greater than 50% destruction of the facets is required, then the motion segment may require stabilization with posterior fusion. 134 J. Neurosurg: Spine / Volume 98 / March, 2003

5 Posterior cervical foraminotomy/discectomy Anterior procedures, in contrast, are typically performed in conjunction with fusion. The distraction provided by the bone graft allows the neural foramen to be opened wider and causes the posterior longitudinal ligament to become stretched, reducing any buckling. The elimination of posterior ligamentous buckling theoretically increases the size of the spinal canal. Anterior fusion has been shown to reduce motion by 50 to 100%, 8 which may improve axial neck pain. This, however, may result in increased stresses on the adjacent vertebral segments. 23,24 Hilibrand, et al., 23 have shown that 10 years after cervical interbody fusion 19% of their patients suffered accelerated adjacent-level degeneration. Procedure-Related Complications Posterior cervical foraminotomy is a safe procedure associated with a very low rate of complications (0 4%). 1,2, 21,37 The greatest complications are wound infections or serous drainage. 21,22 Other complications include cerebrospinal fluid leakage secondary to a dural puncture, wound hematomas, and, rarely, transient or permanent nerve root symptoms. An anterior cervical operation requires dissection around soft tissue and vascular structures. Inadvertent traction or dissection can lead to esophageal perforations, 29 vertebral artery injury, 16 pneumothorax, 11 Horner syndrome (due to injured sympathetic nerves), 3,13 and tracheal/laryngeal injury or dysfunction. 4,9,15,20 These laryngeal/tracheal injuries can lead to dysphonia, hoarseness, dysphagia, and aspiration. 28 The reported rates of vocal cord paralysis after anterior cervical spine surgery have been reported between 0.98 and 3% for permanent paralysis, 6,11,20 and 1.7 and 11% for temporary vocal cord injury. 4,20,28 Finally, via either approach the nerve root and spinal cord may also be transiently or permanently injured. Typically, after completion of the anterior discectomy a bone graft is placed, with or without instrumentation, to enhance a fusion. This can be accomplished using autograft or allograft. Allograft is associated with the theoretical risk of transmitting an infection from the donor. Autograft harvest as well can be associated with significant pain and infection. Boockvar, et al., 5 reported a 36% rate of graft/ plate failure after anterior reconstruction at the cervicothoracic junction. This is most likely due to a biomechanical disadvantage created by the transition from the cervical lordosis to a thoracic kyphosis along with a lesser exposure resulting from anatomical constraints. To date in our series, no patient has developed cervicothoracic kyphosis, but further long-term follow-up data are necessary. Conclusions Although posterior foraminotomy is an established treatment, this technique has not been specifically reported on for application in the cervicothoracic region. The procedure can be performed with minimal risks and achieves excellent outcomes, while not exposing the patient to the infrequent but numerous complications of an anterior procedure at the cervicothoracic junction. Acknowledgment The authors thank Edward Benzel, M.D., for his thorough review and revisions of earlier versions of this manuscript. J. Neurosurg: Spine / Volume 98 / March, 2003 References 1. Adamson TE: Microendoscopic posterior cervical laminoforaminotomy for unilateral radiculopathy: results of a new technique in 100 cases. J Neurosurg (Spine 1) 95:51 57, Aldrich F: Posterolateral microdiscectomy for cervical monoradiculopathy caused by posterolateral soft disc sequestration. J Neurosurg 72: , An HA, Vaccaro A, Cotler JM, et al: Spinal disorders at the cervicothoracic junction. Spine 19: , Apfelbaum RI, Kriskovich MD, Haller JD: On the incidence, cause, and prevention of recurrent laryngeal nerve palsies during anterior cervical spine surgery. Spine 25: , Boockvar JA, Philips MF, Telfeian AE, et al: Results and risk factors for anterior cervicothoracic junction surgery. 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