Neuromonitorisation in prevention of motor-deficit during pediatric spine surgeries *M. Biscevic 1, S. Biscevic 2, F. Ljuca 3, B. Smrke 4, C. Ozturk 5, M. Tiric-Campara 6 1 Spine centre, Orthopedics, KCUS, Sarajevo, Bosnia & Herzegovina - B&H 2 General hospital Prim. dr Abdulah Nakaš Sarajevo, B&H 3 Medical faculty, University of Tuzla, Bosnia and Herzegovina 4 Department of Neurosurgery, Clinical Center Ljubljana, Slovenia 5 Istanbul Spine Center, Florence Nightingale Hospital, Turkey 6 Department of neurology, Clinical center University of Sarajevo, B&H
INTRODUCTION But, it puts a spinal cord under the higher risk (force applied by implants, instruments, or bony impingement, and ishemic changes related to vessel ligation or stretching of spinal arteries). Since 1913., and Hibbs first scoliosis surgery, patient s expectations are shifting toward ideal spine shape. Surgeons can meet that expectations thanks to improved spinal implants, peri-operative care, safer anesthesia, invention of cell saver, etc.
A fear of neurological deficit follows patients and surgeons (pct. of dyplomyelia).
Quick identifying impending spinal cord injury gives surgeon and anesthesiologist the potential to act before the injury became irreversible. The first intraoperative test of motor function was the Stagnara wake-up test from 1973, which has a lot of drawbacks. Era of neuromonitorisation begins 1977 (Nash et al somatosensory evoked potentials - SSEP), then 1980 Merton s descriebes motor evoked potentials - MEP, and year 1992 Calancie triggered EMG.
5 MEP alert criteria: amplitude 65%.
Most common monitoring modality Cortical or sub-cortical responses to repetitive electrical stimulation of a peripheral nerve The dorsal column pathway Continuous 6 SSEP alert criteria: latency 10%, or amplitude 50%. Sensitivity up to 92%, specifity up to 100%, not need a special anestesia.
- spontaneus EMG: a healthy nerve root should have no muscle activity (baseline), nerve root irritation in electrical activity; no stimulation needed required, monitor selective nerve root function, sensitivity 100%, specifity 23,5%, - trigered EMG: usseful in testing of pedicle wall, very useful in minimally invasive spine surgery. 7
MEP has sensitivity and specificity up to 100%, but requires avoiding of halogenated anesthetics, and neuromuscular blockade, like EMG. Combination of different modalities is the best, but impractical in everyday surgeries (neurophysiologist and device). Surgeon directed MEP mode of NIM Eclipse system allows surgeon to monitor his patients during the surgery without assistance of neurophysiologist.
In surgery of pediatric spine deformities additional neurological risk posses patients with neglected scoliosis/kyphosis, congenital deformities, revision surgeries, marfanoid patients with lordoscoliosis, patients with younger age, undeveloped body, other anomalies, low VC, already distracted medulla, etc. Aim of this work is to present our experiences in surgeon directed MEP during surgical corrections of the hardest pediatric spine deformities, pointing on the most dangerous aspects.
PATIENTS AND METHODES Including criteria were: posterior corrective spondylodesis of pediatric types of spine deformities with higher neurological risk (rigid scoliosis 70 of Cobb angle, midthoracic Schoerman kyphosis 90, lowthoracic Schoerman kyphosis 50, hemivertebras and other congenital scoliosis), normal neurological status prior surgery, and surgery performed during April '11- October '14 on our Spine department.
Excluding criteria were: anterior corrective spondylodesis, flexible spine deformities (correction of Cobb angle on traction/bending films more than 40%), non adherence to protocol (total intravenous anesthesia-tiva), degenerative spine deformities. Preoperative protocol, positioning of patient, surgical technique, system of drainage, wound closure, and postoperative care were identical. Above described requirements have completed 49 patients, average 15,3 (8-23) years old, mostly female gender (35:14).
Analyzed group has consisted of: - adolescent idiopathic scoliosis -AIS 70 :34 pts. (69,4%), - revision of anterior surgeris:3 pts. (6,1%), - lordoscoliosis at Sy Marfan patients:3 pts. (6,1%) - midthoracic Schoerman kyphosis 90 :2 pts. (4,1%), - thoracic hemivertebras:3 pts. (6,1%), - lowthoracic Schoerman kyph. 50 :one pat. (2,0%), - other congenital spine deformities:3 pts. (6,1%).
Transcranial electric motor evoked potentials - TcMEP are generated using an electric stimulus applied electrodes inserted into the cranial scalp over the motor cortex (device NIM Eclipse, Medtronic). Distal recordings are typically acquired through needle electrodes inserted bilaterally into the abductor pollicis brevis, quadriceps, anterior tibialis, abductor digiti minimi, and the abductor hallucis.
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RESULTS average SD min. max. age (years) 15,3 4,1 8 23 correction of Cobb angle (%) 71 24 50 94 blod loss (l) 1,2 0,5 0,3 2,1 number of fused vertebras 11,3 2,7 5 18 duration of surgery (hours) 5,3 0,9 2,0 8 All surgeries were performed without MEP, and changes of postoperative neurological status except in two casses.
First patient was 23 year old man with neglected right thoracic AIS of 130. After application of 16kg on halofemoral traction- HF, insertion of screws, and posterior release (SPO-osteotomies), MEPs on left, concave side were decreased about 80%.
Reduction of HF on 10 kg restaurated potentials on baseline. Pre and postoperative clinical and radiological outcome justify such extensive procedure.
Second patient was 19 year old boy with rigid Th-L lordo-scoliosis of 70 due to Marfan syndrome, he had bilateral loss of MEPs, solved on same way.
Second patient wake up without any neurological deficit, too.
DISCUSION Two patients in our group experienced MEP changes, which recovered after discontinuation of distraction, without postop. deficit. In MEP changes, first should be excluded technical factors (electrodes, positioning), anesthesia related factors (inhalation agents, check hypotension, hypoxia, hypothermia), surgical factors (tension of retractors, spinal instrumentation, screw positioning).
If potentials fail to return, then should be considered the wake-up test and corticosteroids, since all deficits are preceded by electrophysiologic changes. The most dangerous moments are curve correction, distraction, osteotomy, hypotension, screw insertions.
Although before 1980 a reported spinal cord injury rate was 0,5-0,8%, after 1980, in monitoring era, there was same incidence of SCI, probably because of underreporting of neurologic events in the past, better capture of current data, or operating of more cases nowadays. Other applications of IONM in spine surgery are assessment of neurological status of unconsciousness patients, spontaneous EMG of LS roots in LS surgery, and rec. laryngeal nerve at cervical disectomy, triggered EMG for intrapedicular screw position, or C5 during posterior decompression.
Neuromonitorisation is reliable method which allows us to catch early signs of neurological deficits, when they are still in reversible phase. It reduces risk of paraplegia about 75%), or at least afford a comfort to the surgeon being fear-free that his patient is neurologicaly intact during long-lasting procedures. Further, surgeon directed MEP is practical, effective and relatively simple to use in everyday spine surgery, making a surgeon independent of neurophysiologist. In the future, function of spinal cord should be part routine monitorisation, like we monitoring of heart, lungs and kidney function is today.