The long-term outcome of revision microdiscectomy for recurrent sciatica

PURPOSE

To study the long-term outcome of revision microdiscectomy after classic microdiscectomy for lumbosacral radicular syndrome (LSRS).

METHODS

Eighty-eight of 216 patients (41%) who underwent a revision microdiscectomy between 2007 and 2010 for MRI disc-related LSRS participated in this study. Questionnaires included visual analogue scores (VAS) for leg pain, RDQ, OLBD, RAND-36, and seven-point Likert scores for recovery, leg pain, and back pain. Any further lumbar re-revision operation(s) were recorded.

RESULTS

Mean (SD) age was 59.8 (12.8), and median [IQR] time of follow-up was 10.0 years [9.0-11.0]. A favourable general perceived recovery was reported by 35 patients (40%). A favourable outcome with respect to perceived leg pain was present in 39 patients (45%), and 35 patients (41%) reported a favourable outcome concerning back pain. The median VAS for leg and back pain was worse in the unfavourable group (48.0/100 mm (IQR 16.0-71.0) vs. 3.0/100 mm (IQR 2.0-5.0) and 56.0/100 mm (IQR 27.0-74.0) vs. 4.0/100 mm (IQR 2.0-17.0), respectively; both p < 0.001). Re-revision operation occurred in 31 (35%) patients (24% same level same side); there was no significant difference in the rate of favourable outcome between patients with or without a re-revision operation.

CONCLUSION

The long-term results after revision microdiscectomy for LSRS show an unfavourable outcome in the majority of patients and a high risk of re-revision microdiscectomy, with similar results. Based on also the disappointing results of alternative treatments, revision microdiscectomy for recurrent LSRS seems to still be a valid treatment. The results of our study may be useful to counsel patients in making appropriate treatment choices.

The role of calcium signaling in early axonal and dendritic morphogenesis of rat cerebral cortex neurons under non-stimulated growth conditions

The effects of depolarizing stimuli on neurite outgrowth have been shown to depend on an influx of extracellular calcium. However, the role of calcium under non-stimulated growth conditions is less well established. Here we investigated the contribution of calcium signaling to early neuronal morphogenesis of rat cerebral cortex neurons at three levels by blocking L-type voltage sensitive calcium channels, by depleting intracellular calcium or by blocking myosin light chain kinase. Detailed quantitative morphological analysis of neurons treated for 1 day revealed that depletion of intracellular calcium strongly decreased the density of filopodia, arrested axonal outgrowth and strongly decreased dendritic branching. Preventing calcium influx through L-type voltage sensitive calcium channels and blocking of myosin light chain kinase activity selectively decreased dendritic branching. Our observations support an essential role for basal intracellular calcium levels in axonal elongation. Furthermore, under non-stimulated conditions calcium entry through L-type voltage sensitive calcium channels and myosin light chain kinase play an important role in dendritic branching.

Depolarization stimulates lamellipodia formation and axonal but not dendritic branching in cultured rat cerebral cortex neurons

Electric activity is known to have profound effects on growth cone morphology and neurite outgrowth, but the nature of the response varies strongly between neurons derived from different species or brain areas. To establish the role of electric activity in neurite outgrowth and neuronal morphogenesis of rat cerebral cortex neurons, cultured neurons were depolarized for up to 72 h and quantitatively analyzed for changes in axonal and dendritic morphology. Depolarization with 25 mM potassium chloride induced a rapid increase in lamellipodia in almost all growth cones and along both axons and dendrites. Lamellipodia formation was dependent on an influx of extracellular calcium through L-type voltage-sensitive calcium channels. Prolonged depolarization for 24 h induced an increase in total axonal length, mainly due to an increase in branching. After three days of depolarization axonal outgrowth was largely the same as in control neurons, suggesting accommodation of the growth cones to chronic depolarization. Dendrites showed very little change during the first three days in culture, and dendritic length or branching were not affected by depolarization. Thus, in early cerebral cortex neurons depolarization specifically stimulates axonal outgrowth through increased branching. This increase in branching may be a consequence of the earlier increase in lamellipodia formation. In contrast, early dendrites seem to be unable to translate the increase in lamellipodia into changes in outgrowth or branching. This difference between axons and dendrites could be due to differences in the stabilization of the tubulin cytoskeleton.