Faculty Bibliography

Although occipitocervical fusion is frequently used for instability of the upper cervical spine and the occipitocervical articulation, most currently used techniques have one or more of the following disadvantages: the necessity for sublaminar wires, the use of occipital screws, a fixed angle of instrumentation, or the necessity for routine postoperative halo immobilization. Moreover, many reported techniques are associated with a high rate of nonunion or instrumentation failure. We present our experience with a technically simple method of obtaining rigid occipitocervical arthrodesis using a 5-mm malleable rod that is fixed to the skull by a pair of wires passed through four suboccipital burr holes. Segmental spinal fixation is achieved with Wisconsin interspinous wires and is occasionally supplemented with sublaminar wires. Supplemental autogenous bone graft is used in all cases. A cervical collar is routinely used for postoperative immobilization. The results of treatment were retrospectively reviewed in 16 patients with an average age of 49.4 years (range, 9-69). Mean follow-up was 24 months (range, 12-36 mo). The indication for fusion was instability of the occiput-C1-C2 complex as a result of Chiari malformation, rheumatoid disease, skull base tumor resection, basilar invagination, ankylosing spondylitis, Down's syndrome, cervical laminectomy, and trauma. The average number of levels fused was 5.4 (range, O-C3 to O-T3). Successful occipitocervical arthrodesis was achieved in all but one of the surviving patients. The single patient with a pseudarthrosis was successfully managed with supplemental bone grafting and halo immobilization. There were two deaths from medical complications in chronically ill patients. Other complications included one postoperative instrumentation loosening, one myocardial infarction, and one superficial occipital decubitus. In conclusion, rodding and segmental interspinous wiring is an effective, technically simple method of obtaining rigid occipitocervical fixation, which obviates the need for bulky orthoses

Tiny metallic particles produced by the contact of untempered surgical instruments with a diamond drill produce magnetic susceptibility artifacts that can both limit the diagnostic quality of postoperative magnetic resonance imaging of the cervical spine and cause diagnostic error. A case of cervical pseudospondylosis with apparent cord compression due to such an artifact is presented. The source of these metallic particles is considered, and the nature of the susceptibility artifact is discussed

Thickening of the ligamenta flava with and without ossification in the thoracic and lumbar regions is a frequent finding on CT scanning; however, it is not widely appreciated as a possible primary cause of compressive cord, cauda equina, and nerve-root symptoms. We present observations from a series of seven patients whose symptoms were caused exclusively or largely by thickened ligamenta flava in the thoracic and lumbar regions. The findings were best demonstrated on myelography. One of our cases had been missed on previous MR, as would be expected with the null signal of calcification. CT scanning necessitates an extended window to ensure discrimination of an ossified ligament from thecal metrizamide. Thickened ligamenta flava are often found in conjunction with degenerative disease and spinal stenosis at multiple levels and should not be ignored as a possible major contributing factor to the patient's symptoms. In addition, those patients with a secondary block from a thickened ligamentum flavum should be studied from above with C1-C2 puncture to rule out other levels of clinically significant disease. Attention to the particular findings of thickened ligamenta flava is important since surgical intervention must involve removal of the entire offending ligament(s); otherwise clinical symptoms may not be relieved

Calcification of the posterior longitudinal ligament occurs in about 3% of adults in Japan, and in about 0.7% of hospitalized adults with spinal symptoms in the United States. The condition may be asymptomatic, however, in patients with a stenotic spinal canal or when the calcification is large, it may cause compression of the spinal cord and myelopathy. The radiographic diagnosis is made when a band of calcification is noted in the spinal canal directly posterior to the vertebral bodies. Lateral tomograms of the spine are helpful for detection and measurement of the exact thickness of the calcification. Computed tomography is particularly helpful because it reveals the thickness and the extent of lateral extension of the calcification, as well as the size of the spinal canal and the extent of its narrowing by the calcification. Seventeen patients evaluated by computed tomography are reported

Somatosensory evoked potentials (SEP's) were monitored during 42 angiographic examinations and 33 therapeutic embolization procedures in 41 patients. The SEP amplitude decreased in 36 of the 42 angiographic techniques, but recovered to baseline within 2 to 4 minutes in all but one case. Angiographic opacification of the anterior spinal artery reduced SEP amplitude in all but two patients, who had lost their proprioceptive sense and had no recognizable SEP prior to the procedure. No neurological complications resulted from any of the angiography procedures. Of the 33 embolizations, 15 were performed in 12 patients with arteriovenous malformations (AVM's) and 18 in 17 patients with spinal canal tumors. There was only one complication associated with embolization: that occurred in a patient with an intramedullary spinal cord AVM. Monitoring SEP amplitude in this series of patients provided a means of rapidly and reliably identifying the anterior spinal artery, served to assess the potential risk of contemplated steps in embolization, and aided in the execution of the angiographic procedures

Computed tomography (CT) of the lumbar spine was performed with selectively positioned 5-mm-thick axial cross sections to examine each disk level from the top of the neural foramen to the pedicle of the next caudad vertebra. One hundred consecutive patients with 116 surgical disk explorations were reviewed. There was agreement between the CT and surgical findings in 89 patients (104 explorations) in determination of presence or absence of a herniated nucleus pulposus (HNP). Discrepancy occurred in 12 instances (11 patients): two because of incorrect interpretations, five in previously operated patients, three in spondylolisthesis, and two in spinal stenosis. There were 97 true-positives, eight false-negatives, seven true-negatives, and four false-positives. If nine previously operated patients are excluded from the study, then CT was accurate in detection of presence or absence of an HNP in 93% of the disk explorations

Acute surgical decompression accompanied by stabilization and fusion is a safe procedure in patients with spinal cord injury. No patient was made worse by surgery. Patients with partial preservation of function and myelographic defects, i.e., surgical candidates, made better recoveries than those with normal myelograms who were, therefore, not operated upon. These results probably signify greater intrinsic cord damage in the nonsurgical group, but confirm the safety of surgery. We doubt the value of decompression for swollen cords except where there are hematomas. The treatment of cord swelling and ischemia will depend on improved pharmacological regimens

Spinal stenosis is a well defined clinical entity that is occasionally encountered in patients with acromegaly. Persistent elevation of growth hormone promotes hypertrophy of the bones and ligaments, resulting in widening of the thoracolumbar vertebral bodies, and developmental narrowing of the spinal canal. This report describes the case of a 54-year-old acromegalic man with a 30-year history of low-back pain. Who developed symptoms of spinal stenosis. This case and two similar cases from the literature are discussed, and the appropriate therapeutic approaches reviewed