Table 2

Cases of false negative intraoperative monitoring

Case No	Diagnosis	Target of IOM	Postoperative findings	Classification
ACA, anterior communicating artery; AVM, arteriovenous malformation; BA, basilar artery; CPA, cerebellopontine angle; CT, computed tomography; ICA, internal carotid artery; intraop, intraoperatively; IOM, intraoperative monitoring; MCA, middle cerebral artery; postop, postoperatively; preop, preoperatively.
1	Right MCA aneurysm	Cerebral hemisphere	Seizures and left hemiparesis 8 h postop, MCA ischaemia, marked attenuation of M-SEP postop	Delayed deficit
2	Intradural schwannoma C4-C6	Spinal cord	Increased sensorimotor paresis of the right arm, normal M-SEP postop	Minor deficit
3	Petroclival meningioma	Brain stem	Reversible, incomplete right hemiparesis, moderate attenuation of M-SEP postop	Minor deficit
4	Left temporal AVM	Cerebral hemisphere	Reversible, incomplete paresis of the right arm, moderate attenuation of M-SEP intraop, small ischaemic internal capsule lesion, unchanged M-SEP postop	Minor deficit
5	BA aneurysm	Brain stem	Delayed MCA ischaemia 18 h postop, complete loss of M-SEP	Delayed deficit
6	Pontine cavernoma	Brain stem	Right hemiparesis, normal M-SEP postop	Severe deficit
7	Left ICA aneurysm	Cerebral hemisphere	Delayed MCA ischaemia 12 h postop, complete loss of M-SEP	Delayed deficit
8	Intramedullary astrocytoma D4-D6	Spinal cord	Moderate T-SEP attenuation intraop, reversible mild paraparesis, unchanged T-SEP postop	Minor deficit
9	Left sphenoidal meningioma	Cerebral hemisphere	Right hemiparesis, partial MCA ischaemia, normal M-SEP postop	Severe deficit
10	Left MCA aneurysm	Cerebral hemisphere	Myocardial infarct 12 h postop, partial MCA ischaemia, right hemiparesis, marked M-SEP attenuation postop	Delayed deficit
11	Left parietal metastasis	Cerebral hemisphere	Reversible mild right hemiparesis and aphasia, normal M-SEP postop	Minor deficit
12	Spinal ependymoma D12 - S5	Spinal cord	Attenuated T-SEP preop, increased distal paraparesis, unchanged T-SEP postop	Minor deficit
13	Left parietal meningioma	Cerebral hemisphere	Attenuated M-SEP preoperatively, reversible mild right hemiparesis, unchanged M-SEP postop	Minor deficit
14	Right sphenoidal meningioma	Cerebral hemisphere	Progressive left hemiparesis 6 h postop, partial MCA ischaemia, marked attenuation of M-SEP postop	Delayed deficit
15	Left parietal glioblastoma	Cerebral hemisphere	Right hemiparesis, normal CT and M-SEP postop	Severe deficit
16	Left parietal astrocytoma	Cerebral hemisphere	Reversible, mild right hemiparesis, normal M-SEP postop	Minor deficit
17	Right MCA aneurysm	Cerebral hemisphere	Left partial hemiparesis, internal capsule ischaemia, normal M-SEP postop	Severe deficit
18	Intradural schwannoma L3-L5	Spinal cord	Reversible incomplete cauda syndrome, normal T-SEP postop	Minor deficit
19	Angioblastoma D11	Spinal cord	Reversible mild paraparesis, normal T-SEP postop	Minor deficit
20	Intradural meningioma D5-D6	Spinal cord	Reversible mild paraparesis and ataxia, no SEP recording postop	Minor deficit
21	Right parietal meningioma	Cerebral hemisphere	Reversible mild left hemiparesis, normal M-SEP postop	Minor deficit
22	Left CPA haemangiopericytoma	Brain stem	Incomplete right hemiparesis and cranial nerve dysfunction, normal M-SEP postop	Severe deficit
23	Left MCA aneurysm	Cerebral hemisphere	Aphasia, partial MCA ischaemia, normal M-SEP postop	Severe deficit
24	ACA aneurysm	Cerebral hemisphere	Right hemiparesis, left thalamic ischaemia, no SEP recording postop	Severe deficit
25	Bilateral cerebellar metastases	Brain stem	Right hemiparesis, left internal capsule ischaemia from presumed embolic insult, normal M-SEP postop	Severe deficit
26	Right parietal metastasis	Cerebral hemisphere	Reversible incomplete left hemiparesis, normal M-SEP postop	Minor deficit
27	Left MCA aneurysm	Cerebral hemisphere	Reversible aphasia, normal CT, normal M-SEP postop	Minor deficit