Table 4.

Analysis of monitoring data on motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs).

	MEP			SSEP
	Overall ACDF	Single level ACDF	Multi-level ACDF	Overall ACDF
Total (n)	177	103	74	196
True positive (n)	4	2	2	0
False positive (n)	5	1	4	2
True negative (n)	164	100	64	188
False negative (n)	1*	0	1*	6
Indeterminate (n)	3	0	3	0
Sensitivity (%)	80	100	66.7	0
Specificity (%)	97	99	94.1	98.9
Positive predictive value (%)	44.4	66.7	33.3	0
Negative predictive value (%)	99.4	100	98.5	96.9

^*False negative case on MEP monitoring: weakness due to hematoma (Case 3, Table 3).