In a case of sudden loss of SSEPs and MEPs during surgery, what does it indicate about the condition of the spinal cord?

The indication of sudden loss of somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) during surgery typically points to transient ischemia affecting the spinal cord. This is because SSEPs and MEPs are reliant on the integrity of the neural pathways and their ability to conduct signals effectively. A sudden loss of these potentials suggests a disruption in blood flow to the spinal cord, which can occur transiently due to various surgical manipulations, positioning, or vascular compromise.

Transient ischemia is often reversible; if normal blood flow is restored promptly, the potentials can return, indicating that there hasn’t been permanent damage to the spinal cord. This ability for recovery is aligned with a transient ischemic event rather than a complete transection or permanent damage, which would lead to irreversible loss of function and evoked potentials. Moreover, normal function would imply that there are no significant disruptions occurring, which contradicts the very premise of losing these potentials in the first place. Hence, the sudden loss of SSEPs and MEPs is most consistent with a scenario of transient ischemia.