Intraoperative spinal cord monitoring using low intensity transcranial stimulation to remove post-activation depression of the H-reflex.

OBJECTIVE: To investigate whether low intensity transcranial electrical stimulation (TES) can be used to condition post-activation depression of the H-reflex and simultaneously monitor the integrity of spinal motor pathways during spinal deformity correction surgery. METHODS: In 20 pediatric patients undergoing corrective surgery for spinal deformity, post-activation depression of the medial gastrocnemius H-reflex was initiated by delivering two pulses 50-125ms apart, and the second H-reflex was conditioned by TES. RESULTS: Low intensity TES caused no visible shoulder or trunk movements during 19/20 procedures and the stimulation reduced post-activation depression of the H-reflex. The interaction was present in 20/20 patients and did not diminish throughout the surgical period. In one case, the conditioning effect was lost within minutes of the disappearance of the lower extremity motor evoked potentials. CONCLUSION: Post-activation depression was used to detect the arrival of a subthreshold motor evoked potential at the lower motor neuron. The interaction produced minimal movement within the surgical field and remained stable throughout the surgical period. SIGNIFICANCE: This is the first use of post-activation depression during intraoperative neurophysiological monitoring to directly assess the integrity of descending spinal motor pathways.

Predicting success or failure of brace treatment for adolescents with idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity. Brace treatment is a common non-surgical treatment, intended to prevent progression (worsening) of the condition during adolescence. Estimating a braced patient's risk of progression is an essential part of planning treatment, so method for predicting this risk would be a useful decision support tool for practitioners. This work attempts to discover whether failure of brace treatment (progression) can be predicted at the start of treatment. Records were obtained for 62 AIS patients who had completed brace treatment. Subjects were labeled as "progressive" if their condition had progressed despite brace treatment and "non-progressive" otherwise. Wrapper-based feature selection selected two useful predictor variables from a list of 14 clinical measurements taken from the records. A logistic regression model was trained to classify patients as "progressive" or "non-progressive" using these two variables. The logistic regression model's simplicity and interpretability should facilitate its clinical acceptance. The model was tested on data from an additional 28 patients and found to be 75 % accurate. This accuracy is sufficient to make the predictions clinically useful. It can be used online: http://www.ece.ualberta.ca/~dchalmer/SimpleBracePredictor.html .

Preservation of motor evoked potentials under anesthesia in children with spinal muscular atrophy type II undergoing spinal deformity surgery.

Spinal muscular atrophy is a progressive condition in which movement is gradually lost as a result of the loss of spinal motor neurons. Individuals with this condition may require surgical correction of a secondary scoliosis. Motor evoked potentials were recorded using transcranial electrical stimulation in four such individuals undergoing surgery. All the patients were nonambulatory and in wheelchairs. Motor evoked potentials were recordable in both upper and lower limb muscles, with similar stimulation parameters to control subjects undergoing surgery for idiopathic scoliosis. The amplitudes of the motor evoked potentials were similar to those in control subjects, although the latencies were shorter reflective of the smaller stature of the spinal muscular atrophy patients. The relative preservation of the motor evoked potentials despite the patients' poor voluntary motor control suggests that there is a selective preservation of the motor neurons mediating the motor evoked potential in spinal muscular atrophy and a maintenance of the conduction velocities of the corticospinal tract.

The effect of time on qualitative compliance in brace treatment for AIS.

Brace treatment is the most commonly used non-surgical treatment method for adolescent idiopathic scoliosis (AIS). This study is to determine the force changes exerted by a brace over time during both day and night-time wear and to explore correlations between force changes to bracing outcomes. Twenty subjects (three male, 17 female) diagnosed with idiopathic scoliosis who had worn their braces for six months participated into this study. However, due to non-continuous brace wear and exclusion of subjects with large curves (Cobb angle >40 degrees), only nine subjects were included into the day-time analysis and 11 subjects were included into night-time analysis. All subjects used a load monitor system from four days up to 14 days with Boston braces. Cobb angle measurements were taken at initiation of brace treatment as well as after weaning upon completion of the treatment. After the monitoring period, the data was extracted and analyzed. Forces were compared between hours 1, 2, and 5 for the day and night groups, and the correlation of force changes to bracing outcomes were analyzed. In daytime wear, a significant decrease in force over time was found. Most of the decrease occurred within hours 1 and 2 of brace wear. There was no significant decrease during night wear. There were no significant correlations between force decline and outcome.

Spontaneous spinal epidural hematoma causing Brown-Sequard syndrome: case report and review of the literature.

Spinal epidural hematoma is a rare clinical entity and has a varied etiology. Urgent surgical evacuation to prevent serious permanent neurologic deficits is generally indicated. We describe a case of a 52-year-old man, on oral anticoagulant therapy, who presented with Brown-Sequard syndrome due to spontaneous spinal epidural hematoma at the cervicothoracic junction. This diagnosis was initially overlooked, given the asymmetric pattern of deficit. He later underwent cervical laminectomy and had complete restoration of neurologic function.

Vertebral body reconstruction for thoracolumbar spinal metastasis--a review of techniques.

The spine is the most common site of skeletal metastases with its involvement occurring in up to 40% of patients. Metastatic spinal involvement can cause a number of sequelae like pain, instability and neurologic compression. About 10% of patients with involvement of the vertebral column will subsequently develop neurologic compression.The metastatic spinal lesions mostly affect the vertebral body and pedicle (85%). Management of spinal metastases remains controversial. Recent reports attest to the beneficial role of surgery. The role of decompressive laminectomy without stabilization, has been questioned. The Involvement of Vertebral Body and anterior compression had led to an increasing attention to anterior decompressive procedures, reconstruction and Stabilization. We Review here the Techniques described in literature for anterior reconstruction after vertebral corpectomy.

Intra-observer reproducibility and interobserver reliability of the radiographic parameters in the Spinal Deformity Study Group's AIS Radiographic Measurement Manual.

STUDY DESIGN: Retrospective cross-sectional assessment of the reproducibility and reliability of radiographic parameters. OBJECTIVE: To measure the intra-examiner and interexaminer reproducibility and reliability of salient radiographic features. SUMMARY OF BACKGROUND DATA: The management and treatment of adolescent idiopathic scoliosis (AIS) depends on accurate and reproducible radiographic measurements of the deformity. METHODS: Ten sets of radiographs were randomly selected from a sample of patients with AIS, with initial curves between 20 degrees and 45 degrees. Fourteen measures of the deformity were measured from posteroanterior and lateral radiographs by 2 examiners, and were repeated 5 times at intervals of 3-5 days. Intra-examiner and interexaminer differences were examined. The parameters include measures of curve size, spinal imbalance, sagittal kyphosis and alignment, maximum apical vertebral rotation, T1 tilt, spondylolysis/spondylolisthesis, and skeletal age. RESULTS: Intra-examiner reproducibility was generally excellent for parameters measured from the posteroanterior radiographs but only fair to good for parameters from the lateral radiographs, in which some landmarks were not clearly visible. Of the 13 parameters observed, 7 had excellent interobserver reliability. CONCLUSIONS: The measurements from the lateral radiograph were less reproducible and reliable and, thus, may not add value to the assessment of AIS. Taking additional measures encourages a systematic and comprehensive assessment of spinal radiographs.

Changes in alignment of the scoliotic spine in response to lateral bending.

STUDY DESIGN: A retrospective cross-sectional review studied the posteroanterior and lateral bending radiographs of 26 preoperative patients with thoracic major adolescent idiopathic scoliosis. OBJECTIVE: To characterize the relation of vertebral axial rotation, apparent vertebral wedging, and disc wedging with lateral bending in patients with severe adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Lateral bending radiographs are used commonly in surgical planning to assess the flexibility of the spine and to establish the placement of instrumentation. However, their use in the assessment of motion in the axial plane has not been clearly established. METHODS: Data were collected retrospectively from 26 subjects immediately before spinal surgery. All the subjects had adolescent idiopathic scoliosis with right thoracic major curves. Axial rotation, vertebral wedging, and disc wedging were measured from T4 to L4 on left and right supine bending and standing posteroanterior radiographs. The apexes of the major and minor curves, the neutral vertebrae, and the Cobb angles were recorded. RESULTS: No significant differences in axial rotation were found at the thoracic apex, neutral vertebrae, or lumbar apex in response to lateral bending. Most of the wedging occurs in the disc, and is maximal at the apex of the curve. The total amount of wedging was higher in more severe curves. CONCLUSIONS: Lateral bending does not improve axial rotation in severe scoliosis (scoliosis for which surgical correction is advised). Structural changes including disc and vertebral wedging may be responsible for the lack of rotational correction of the scoliotic spine. Lack of axial flexibility in the thoracic region may hamper surgical attempts to correct the deformities of the trunk.