Spinal somatosensory evoked potential evaluation of acute nerve‐root injury associated with pedicle‐screw placement procedures: An experimental study

Abstract

Pedicle screws for spinal fixation risk neural damage because of the proximity between screw and nerve root. We assessed whether spinal somatosensory evoked potential (SSEP) could selectively detect pedicle-screw-related acute isolated nerve injury. Because pedicle screws are too large for a rat's spine, we inserted a K-wire close to the pedicle in 32 rats, intending not to injure the nerve root in eight (controls), and to injure the L4 or L5 root in 24. We used sciatic-nerve-elicited SSEP pre-and postinsertion. Radiologic, histologic, and postmortem observations confirmed the level and degree of root injury. Sciatic (SFI), tibia1 (TFI), and peroneal function indices (PFI) were calculated and correlated with changes in potential. Although not specific for injuries to different roots, amplitude reduction immediately postinsertion was significant in the experimental groups. Animals with the offending wire left in place for one hour showed a further non-significant deterioration of amplitude. Electrophysiologic changes correlated with SF1 and histologic findings in all groups. SSEP monitoring provided reliable, useful diagnostic and intraoperative information about the functional integrity of single nerve-root injury. These findings are clinically relevant to acute nerve-root injury and pedicle-screw insertion. If a nerve-root irritant remains in place, a considerable neurologic deficit will occur.

Dermatomal laser-evoked potentials: a diagnostic approach to the dorsal root. Norm data in healthy volunteers and changes in patients with radiculopathy

“…This causes a reduced number of fibers in animals [22,23]. It is therefore likely reducing neuronal impulse synchronization or inducing a complete conduction block.…”

An effective intra-operative neurophysiological monitoring scheme for aneurysm clipping and spinal fusion surgeries

“…They are also used for the identification of the sensory portion of the sensorimotor cortex (Celesia 1979). SSEPs are also widely used for intra-operative neurophysiological monitoring (IONM) in surgeries for scoliosis (Schwartz et al 2007, Pastorelli et al 2011, pedicle-screw placement procedures (Jou et al 2003), and spinal cord related surgical procedures (Dinner et al 1986, Nuwer et al 1995, McGarry et al 1984.…”

Value of Dermatomal Somatosensory Evoked Potentials in Detecting Acute Nerve Root Injury

“…There are few techniques for intraoperative neuromonitoring of a single nerve root, and no reliable method has been established. [5][6][7][8][9][10][11][12][13][14]18,19 Spontaneous or evoked electromyographic (EMG) activity recorded from appropriate muscle groups has proven useful, providing information about specific nerve root injuries in the lumbosacral spine. 5,6,10 Dermatomal spinal somatosensory-evoked potentials (D-SSEP) obtained from the stimulation of different dermatomes have been advocated as a useful alternative route because such potentials seem to reflect the specific conduction of the supplying nerve root.…”