Introduction: Peri-operative positional neurophysiological changes in the upper limbs as identified by somatosensory evoked potentials (SSEPs) monitoring have been more extensively studied in anterior surgical approaches to the cervical spine, with a reported incidence of approximately 1% of patients and most commonly affecting the brachial plexus. However, the incidence and clinical implication of positional SSEP changes of upper limbs during posterior thoracolumbar instrumentation surgeries is unknown in the literature.
Methods: Prospective analysis of cases of neurophysiological traces during posterior thoracolumbar instrumentations performed between July 2014 and March 2015 in which intra-operative SSEPs monitoring of upper and lower limbs (either along or in conjunction with MEPs) were employed.
Results: In 2/15 (13%) of cases of thoracolumbar fusions, intermittent changes in SSEP in one of the upper limbs related to brachial plexus compression were identified. Although one of this cases involved a long posterior instrumentation (T10 to sacrum) in a patient with a major scoliosis and a BMI > 30, the other case involved a single level TLIF in a young and non-obese patient. In both patients, these changes completely resolved after relieving axillary pressure from the thoracic pad of the Jackson table and/or releasing the affected arm. None of the patients exhibited sensory of motor neurological changes in the post-operative period.
Conclusions: Our data suggest that, although neurophysiological monitoring may not be necessary for every posterior thoracolumbar instrumentation to the spine, in those cases in which it is employed (either for monitoring of pedicle screw placement or for monitoring of spinal cord function), placement of needles and continuous monitoring of upper limbs (in addition to lower limbs) is recommended, as it may be able to avoid post-operative complications related to positioning-related brachial plexus compression. According to our surgical experience, SSEP monitoring of upper limbs may play an essential role in avoiding positioning-related complications not only in long thoracolumbar instrumentations and those involving prolonged intra-operative time or obese patients, but also in routine single-level degenerative fusions.
Patient Care: By increasing the awareness of the surgical community to the possible role of upper limbs neurophysiological monitoring during posterior thoracolumbar instrumentation, this study is expected increase the overall safeness of such type of procedure by reducing the rates of positioning-related complications related to brachial plexus compression.
Learning Objectives: 1. Understand that the role of neurophysiological monitoring of upper limbs in preventing positioning-related complications in posterior thoracolumbar approaches to the spine surgeries is not well characterized in the literature.
2. Recognize that the true incidence of positioning-related brachial plexus SSEPs changes in posterior spinal instrumentation may be underestimated in the literature.
3. Acknowledge that, in posterior approaches to the thoracolumbar spine in which neurophysiological monitoring is employed (either for monitoring of pedicle screw placement or for monitoring of spinal cord function), placement of needles and continuous monitoring of upper limbs (in addition to lower limbs) is recommended in order to avoid positioning-related upper limbs changes.
References: 1 Smith PN, Balzer JR, Khan MH, Davis RA, Crammond D, Welch WC, et al. Intraoperative somatosensory evoked potential monitoring during anterior cervical discectomy and fusion in nonmyelopathic patients--a review of 1,039 cases. The spine journal : official journal of the North American Spine Society 2007;7:83-7.
2 Kamel I, Barnette R. Positioning patients for spine surgery: Avoiding uncommon position-related complications. World journal of orthopedics 2014;5:425-43.
Chung I, Glow JA, Dimopoulos V, Walid MS, Smisson HF, Johnston KW, Robinson JS, Grigorian AA.
Upper-limb somatosensory evoked potential monitoring in lumbosacral spine surgery: a prognostic marker for position-related ulnar nerve injury.Spine J. 2009 Apr;9(4):287-95. doi: 10.1016/j.spinee.2008.05.004. Epub 2008 Aug 5.