Gerit Kulik

Qualitative grading of severity of lumbar spinal stenosis based on the morphology of the dural sac on magnetic resonance images.

Study Design. Retrospective radiologic study on a prospective patient cohort. Objective. To devise a qualitative grading of lumbar spinal stenosis (LSS), study its reliability and clinical relevance. Summary of Background Data. Radiologic stenosis is assessed commonly by measuring dural sac cross-sectional area (DSCA). Great variation is observed though in surfaces recorded between symptomatic and asymptomatic individuals. Methods. We describe a 7-grade classification based on the morphology of the dural sac as observed on T2 axial magnetic resonance images based on the rootlet/cerebrospinal fluid ratio. Grades A and B show cerebrospinal fluid presence while grades C and D show none at all. The grading was applied to magnetic resonance images of 95 subjects divided in 3 groups as follows: 37 symptomatic LSS surgically treated patients; 31 symptomatic LSS conservatively treated patients (average follow-up, 2.5 and 3.1 years); and 27 low back pain (LBP) sufferers. DSCA was also digitally measured. We studied intra- and interobserver reliability, distribution of grades, relation between morphologic grading and DSCA, as well relation between grades, DSCA, and Oswestry Disability Index. Results. Average intra- and interobserver agreement was substantial and moderate, respectively (k = 0.65 and 0.44), whereas they were substantial for physicians working in the study originating unit. Surgical patients had the smallest DSCA. A larger proportion of C and D grades was observed in the surgical group. Surface measurements resulted in overdiagnosis of stenosis in 35 patients and under diagnosis in 12. No relation could be found between stenosis grade or DSCA and baseline Oswestry Disability Index or surgical result. C and D grade patients were more likely to fail conservative treatment, whereas grades A and B were less likely to warrant surgery. Conclusion. The grading defines stenosis in different subjects than surface measurements alone. Since it mainly considers impingement of neural tissue it might be a more appropriate clinical and research tool as well as carrying a prognostic value.

Interspinous distraction in lumbar spinal stenosis: a neurophysiological perspective.

Study Design. Prospective neurophysiological study. Objective. To identify and quantify the neurophysiological effects of interspinous distraction during spine surgery for lumbar spinal stenosis (LSS). Summary of Background Data. Interspinous devices have been introduced as an alternative treatment of LSS in selected patients aiming at obtaining indirect decompression. Nevertheless, there is no data on the immediate neurophysiological effect of distraction. Methods. Thirty patients with LSS undergoing decompression (14 at single level, 16 at multiple levels) were enrolled, resulting in a total of 48 levels to be analyzed. Before decompression, calibrated incremental distraction simulating interspinous device implantation of 8, 10, 12, 14, and 16 mm was performed. Intraoperative motor evoked potentials were acquired before any distraction, during distraction at each incremental value and after bilateral decompression. We evaluated relative changes of motor evoked potentials normalized to hand muscles and related them to the number of affected levels, LSS radiological severity based on the A to D grading, lordosis, and disc height. Results. For single-level disease, 8-mm distraction and open decompression yielded similar improvement in motor evoked potentials not only in levels with morphological grades A or B, but also in levels with morphological grades C or D (i.e., severe or extreme stenosis) (P = 0.32). In contrast, distraction superior to 8 mm was less effective (P ⩽ 0.05). In multiple-level stenosis, decompression was significantly more effective than any degree of distraction (P < 0.001). No correlation of those results to disc height or lordosis was observed. Using &khgr;2 trend test to analyze the effect of distraction, a linear trend favoring moderate over severe stenotic morphology was observed (P = 0.0349). Conclusion. Interspinous distraction of 8 mm is sufficient to replicate electrophysiological improvements obtained during full decompression even in severe single-level stenosis but not in multilevel disease. Interspinous distraction has therefore an immediately measurable neurophysiological effect. Level of Evidence: 4

Secular changes of spinal canal dimensions in Western Switzerland: a narrowing epidemic?

Study Design. Computed tomography–based anatomical study. Objective. To study the secular changes in lumbar spinal canal dimensions. Summary of Background Data. Development of symptomatic lumbar spinal stenosis, among other factors, is related to the dimensions of the bony canal. The canal reaches its adult size early on in life. Several factors, including protein intake, may influence its final dimensions. As with increases in human stature from improvements of socioeconomic conditions, we hypothesized that adult bony canal size has also grown larger in recent generations. Methods. This study analyzes computed tomographic reconstructions from 184 subjects performed for either trauma (n = 81) or abdominal pathologies (n = 103) and born either between 1940 and 1949 (n = 88) or 1970 and 1979 (n = 96). The cross-sectional area of the bony canal was digitally measured at the level of the pedicle (i.e., at a level not influenced by degenerative changes) for each lumbar vertebra. Intra- and interobserver reliability was assessed. Results. Intra- and interobserver measurement reliability were excellent (interclass correlation coefficient = 0.87) and good (interclass correlation coefficient = 0.61), respectively. Contrary to our hypothesis, the 1940–1949 generation patient group exhibited larger lumbar canals at all levels as compared with the 1970–1979 group. Statistically this difference was highly significant (P < 0.001) and particularly pronounced in the trauma subgroup. Conclusion. Given that human stature evolution has stabilized and adult height is established during the first 2 years of long bone growth, it is possible that antenatal factors are responsible for this surprising finding. Maternal smoking and age may be possible explanations. This finding may have significant implications. An increasing number of patients may emerge with lumbar spinal stenosis as degenerative changes develop, putting a strain on health resources. Further studies in different population groups and countries will be important to further confirm this trend. Level of Evidence: 3

Neurophysiological changes during shortening osteotomies of the spine

BACKGROUND CONTEXT Kyphotic deformities with sagittal imbalance of the spine can be treated with spinal osteotomies. Those procedures are known to have a high incidence of neurological complications, in particular at the thoracic level. Motor evoked potentials (MEPs) have been widely used in helping to avoid major neurological deficits postoperatively. Previous reports have shown that a significant proportion of such cases present with important transcranial MEP (Tc-MEP) changes during surgery with some of them being predictive of postoperative deficits. PURPOSE Our aim was to study Tc-MEP changes in a consecutive series of patients and correlate them with clinical parameters and radiological changes. STUDY DESIGN/SETTING Retrospective case notes study from a prospective patient register. PATIENT SAMPLE Eighteen patients undergoing posterior shortening osteotomies (nine at thoracic and nine at lumbar levels) for kyphosis of congenital, degenerative, inflammatory, or post-traumatic origin were included. OUTCOME MEASURES Loss of at least 80% of Tc-MEP signal expressed as the area under the curve percentual change, of at least one muscle. METHODS We studied the relation between outcome measure (80% Tc-MEP loss in at least one muscle group) and amount of posterior vertebral body shortening as well as angular correction measured on computed tomography scans, occurrence of postoperative deficits, intraoperative blood pressure at the time of the osteotomy, and hemoglobin (Hb) change. RESULTS All patients showed significant Tc-MEP changes. In particular, greater than 80% MEP loss in at least one muscle group was observed in five of nine patients in the thoracic group and four of nine patients in the lumbar group. No surgical maneuver was undertaken as a result of this loss in an effort to improve motor responses other than verifying the stability of the construct and the extent of the decompression. Four patients developed postoperative deficits of radicular origin, three of them recovering fully at 3 months. No relation was found between intraoperative blood pressure, Hb changes, and Tc-MEP changes. Severity of Tc-MEP loss did not correlate with postoperative deficits. Shortening of more than 10 mm was linked to more severe Tc-MEP changes in the thoracic group. CONCLUSIONS Transcranial MEP changes during spinal shortening procedures are common and do not appear to predict severe postoperative deficits. Total loss of Tc-MEP (not witnessed in our series) might require a more drastic approach with possible reversal of the correction and wake-up test.

Do intra-operative neurophysiological changes predict functional outcome following decompressive surgery for lumbar spinal stenosis? A prospective study

Background To analyse the relation between immediate intraoperative neurophysiological changes during decompression and clinical outcome in a series of patients with lumbar spinal stenosis (LSS) undergoing surgery. Methods Twenty-four patients with neurogenic intermittent claudication (NIC) due to LSS undergoing decompressive surgery were prospectively studied. Intra operative trans-cranial motor evoked potentials (tcMEPs) were recorded before and immediately after surgical decompression. Lower limb normalised tcMEP improvement was used as primary neurophysiological outcome. Clinical outcome was assessed using the Zurich Claudication Questionnaire (ZCQ) self-assessment score, before surgery (baseline) and at an average of 8 and 29 months post-operatively. Results We found a moderate positive correlation between tcMEP changes and ZCQ at early follow-up (R=0.36). At late follow-up no correlation was found between intra-operative tcMEP and ZCQ changes. Dichotomizing the data showed a statistically significant relationship between tcMEP improvement and better functional outcome at early follow-up (P=0.013) but not at later follow-up (P=1). Conclusions Our findings suggest that intra-operative neurophysiological improvement during decompressive surgery may predict a better clinical outcome at early follow-up although this is not applicable to late follow-up possibly due to the observed erosion of functional improvement with time.