In a randomized, prospective, double-blind study, Cuckler and associates 13 were not able to ascertain a benefit from interlaminar injection of methylprednisolone acetate compared with physiologic saline at 24-hour and approximately 20-month follow-up. This study was somewhat limited by the authors' definition of 75% or greater subjective improvement over preinjection symptoms as a successful result and their failure to look at outcomes in the interval between a day and a year after injection. Interlaminar and caudal injections once were in common use and still may be best for multilevel pathology.
In a retrospective study, Narozny and associates (2001) investigated the clinical effectiveness of nerve root blocks (., peri-radicular injection of bupivacaine and triamcinolone) for lumbar mono-radiculopathy in patients with a mild neurological deficit. These researchers analyzed 30 patients (aged 29 to 82 years) with a minor sensory/motor deficit and an unequivocal MRI finding (20 disc herniations, 10 foraminal stenoses) treated with a SNRB. Based on the clinical and imaging findings, surgery (decompression of the nerve root) was justifiable in all cases. Twenty-six patients (87 %) had rapid (1 to 4 days) and substantial regression of pain, 5 required a repeat injection. Furthermore, 60 % of the patients with disc herniation or foraminal stenosis had permanent resolution of pain, so that an operation was avoided over an average of 16 months (6 to 23 months) follow-up. The authors concluded that SNRBs are very effective in the non-operative treatment of minor mono-radiculopathy and should be recommended as the initial treatment of choice for this condition.
Magnetic resonance imaging (MRI) has been used increasingly in recent years since introduction of titanium-based implants with reduced artifact compared to formerly used stainless-steel devices. These artifacts could be decreased even more by changing imaging parameters such as reducing echo time, increasing bandwidth and decreasing voxel size. Aligning the implant along the axis of the magnetic field also reduces artifact although it is often not completely achievable due to the multidirectional configuration of most hardware. Spin echo sequences are less vulnerable to magnetic susceptibility artifact and give better quality images compared with gradient echo sequences. MRI is useful in detecting infection (Figure 9) and assessing recurrent tumor. MRI is the modality of choice in assessing intraspinal contents. Myelography (Figure 6) is an alternative when MRI is contraindicated or is nondiagnostic because of artifact.