The cases of two patients with delayed paraplegia after segmental spinal
instrumentation with sublaminar wiring are reported. Both patients had
complex spinal deformities and had transient neural deficits after the
first-stage procedure of anterior release and spine fusion. They had
uneventful spinal-cord monitoring during the second-stage procedure of
posterior instrumentation and fusion, and function of the lower extremities
was present immediately after that operation. Paraplegia then ensued, and
was recognized thirty hours later in one patient and six days later in the
other. Considering our reproducible and reliable experience (no
false-negative results) with spinal cord monitoring in 307 operations, we
propose that the delayed onset of paraplegia resulted from a progression of
ischemic and edema-producing events that had not developed sufficiently
intraoperatively to be reflected by the monitoring. The paraplegia became
evident only when the subarachnoid space was obstructed because of
progressive postoperative neural edema. The presence of sublaminar implants
in narrow, kyphotic segments of the spinal canal probably exacerbated the
neural irritation by dural impingement, which was seen
myelographically.