Increasing the clinical value of the zones of partial preservation â A quantitative comparison of a new definition rule applicable also in incomplete lesions
1Schuld C, 1Franz S, 1Weidner N, 2Kirshblum S, 3Tansey K, 1Rupp R
1Heidelberg University Hospital, Heidelberg, , Germany; 2Kessler Institute for Rehabilitation, West Orange, New jersey, USA; 3Methodist Rehabilitation Center, Jackson, Mississipp, USA
Objective: The zones of partial preservation (ZPPs) as part of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) represent an important piece of information for the characterization of a patient's neurological status. Additionally, ZPPs are among the most important predictors of neurological recovery . In the current ISNCSCI revision, ZPPs are only defined for complete (= AIS A) injuries excluding cases were only one entity of sensorimotor functions in S4-5 is absent. Recording ZPPs only in cases with totally lost sensation (absent deep anal pressure (DAP), absent light touch (LT), absent pin prick (PP)) and motor function (no voluntary anal contraction (VAC)) in S4-5 is not intuitive and restricts the value of ZPP for effective clinical communication to AIS A lesions only.
To overcome these restrictions, we introduce slightly modified ZPP rules for consideration, which are not based on the AIS grade, but defines motor ZPPs in case of absence of VAC and sensory ZPPs in the absence of sensory function in S4-5 (LT, PP and/or DAP) in incomplete injuries. The aim of this study is to simulate the changes in ZPP occurrence frequencies compared to the current ZPP definition.
Design: A benchmark dataset consisting of 1,330 ISNCSCI records of 665 individuals with SCI from the European Multicenter about Spinal Cord Injury (EMSCI) database (April 2013) were included (traumatic SCI, age >= 16, two ISNCSCI examinations <= 30 days and 1 year after injury). All ISNCSCI datasets were reclassified by the EMSCI ISNCSCI calculator  using the modified ZPP rules.
Results: The dataset consist of 40.5% AIS A, 9.8% AIS B, 13.2% AIS C, 35.8% AIS D and 0.8% AIS E lesions. ZPPs for AIS A lesions remained unchanged and ZPPs for AIS E are not applicable. Among the AIS B lesions, a motor ZPP with an extent greater than zero segments could be determined in 65.6% (82/131) of all cases with a mean motor ZPP of 1.49+/-0.91 (right side) and 1.38+/-0.86 (left side) segments. Among the AIS C lesions, 55.4% (97/175) had absent VAC with a mean motor ZPP of 11.1+/-8.5 (right) and 12.5+/-7.9 (left) segments. Of the AIS D cases, 9.2% (44/476) had absent VAC (right preservation: 14.7+/-8.5; left preservation 16.2+/-7.0). Among all motor incomplete AIS C-D lesions, a meaningful sensory ZPP could be found in 0.8% (5/(175+476)) AIS C cases, where only VAC determined the incompleteness. The mean sensory ZPP in these cases was bilaterally 7.0+/-8.9 segments. Overall, ZPPs can be derived in (82+97+44+5)/782 (29.1%, motor: 28.5%, sensory: 0.6%) of all incomplete lesions.
Conclusion: The found proportions of motor incomplete lesions with absent VAC are in line with a recent analysis of the national Spinal Cord Injury Model Systems  (AIS C: 55.4% vs 43.5%, AIS D: 9.2% vs 11.6%). In one third of the incomplete patients meaningful ZPPs can be provided, if ZPPs are not limited to complete lesions only. It seems advisable to redefine the motor ZPP to be applicable if VAC is absent. Likewise, the sensory ZPP should be applicable if absent sensory function in S4-5 is found, although this case is rare in motor incomplete lesions.
Support: This work is partly supported by the Deutsche Stiftung Querschnittlaehmung (DSQ) and the EMSCI network.
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