Noninvasive Physiologic Evaluation of the Aneurysm Patient

Diagnostic accuracy of somatosensory evoked potentials during intracranial aneurysm clipping for perioperative stroke

Somatosensory evoked potentials (SSEPs) are utilized during aneurysm clipping to detect intraoperative ischemia. We assess the diagnostic accuracy of SSEPs in predicting perioperative stroke during aneurysm clipping. A retrospective review was conducted of 429 consecutive patients who underwent surgical clipping for ruptured and unruptured cerebral aneurysms with intraoperative SSEP monitoring from 2006 to 2013. The relationship between perioperative stroke and SSEP changes was analyzed by calculating the sensitivity, specificity, and area under a Receiving Operating Characteristic curve. Sensitivity and specificity were 42% and 90%, respectively. Area under the curve was 0.66 (95% confidence interval, 0.53-0.79). Reclassification of reversible temporary clip changes to correct for paradoxical classification of SSEP false positives raised the sensitivity from 42 to 65% (p = 0.041, Chi squared test). EEG (electroencephalography) changes increased the specificity (98% vs. 90%, p < 0.001, McNemar's test), but not sensitivity (48% vs. 42%, p = 0.621, McNemar's test) of SSEPs for perioperative stroke. A stepwise logistic regression model selected SSEP amplitude loss (p = 0.006, OR = 3.7 [95% CI 1.5-9.2]) and the SSEP change duration (p = 0.034, OR = 1.8 [95% CI 1.1-3.1]) as independent predictors of perioperative stroke. SSEP changes induced by temporary clipping were highly reversible compared to other SSEP changes (94% vs. 60%, p = 0.003, Fisher exact test), and typically responded to clip removal or readjustment. SSEP changes have high specificity and modest sensitivity for perioperative stroke. Stroke risk is a function of both the magnitude of SSEP amplitude loss and the duration of its loss. Given the modest sensitivity, patients may benefit from multimodal monitoring including motor-evoked potentials during cerebral aneurysm surgery.

Impact of Changes in Intraoperative Somatosensory Evoked Potentials on Stroke Rates After Clipping of Intracranial Aneurysms

BACKGROUND:

Somatosensory evoked potential (SSEP) monitoring is used during intracranial aneurysm surgery to track the effects of anesthesia, surgical manipulation, and temporary clipping.

OBJECTIVE:

To present the outcomes of 663 consecutive patients (691 cases) treated surgically for intracranial aneurysms who underwent intraoperative SSEP monitoring and to analyze the sensitivity and specificity of significant SSEP changes in predicting postoperative stroke.

METHODS:

Of 691 surgeries analyzed, 403 (391 anterior circulation, 12 posterior circulation) were unruptured aneurysms and 288 (277 anterior, 11 posterior) were ruptured. Postoperatively, symptomatic patients underwent computed tomography imaging. Positive predictive value, negative predictive value, sensitivity, and specificity were calculated with a Fisher exact test (2-tailed P value).

RESULTS:

Changes in SSEP occurred in 45 of 691 cases (6.5%): 16 of 403 (4.0%) in unruptured aneurysms and 29 of 288 (10%) in ruptured aneurysms. In unruptured aneurysms, reversible SSEP changes were associated with a 20% stroke rate, but irreversible changes were associated with an 80% stroke rate. In ruptured aneurysms, however, reversible changes were associated with a 12% stroke rate, and irreversible changes were associated with a 42% stroke rate. The overall accuracy of SSEP changes in predicting postoperative stroke was as follows: positive predictive value, 30%; negative predictive value, 94%; sensitivity, 25%; and specificity, 95%.

CONCLUSION:

Intraoperative SSEP changes are more reliable in unruptured aneurysm cases than in ruptured cases. Whereas irreversible changes in unruptured cases were associated with an 80% stroke rate, such changes in ruptured cases did not have any adverse ischemic sequelae in 58% of patients. This information is helpful during the intraoperative assessment of reported SSEP changes.

Multiple intraoperative monitoring-assisted microneurosurgical treatment for anterior circulation cerebral aneurysm

This study investigated the efficacy of multiple intraoperative monitoring techniques including indocyanine green angiography (ICGA), somatosensory evoked potential (SSEP) and motor evoked potential (MEP) in the clinical outcome of microneurosurgical treatment for anterior circulation cerebral aneurysm. Fifty-two anterior circulation cerebral aneurysms (Hunt and Hess [H&H] grades 0, 1 or 2) from 45 Chinese in-patients were completely clipped. In one patient, ICGA directed neurosurgeons to readjust aneurysmal clips in order to eliminate a residual aneurysm and restore patency of a branching artery. SSEP/MEP directed neurosurgeons to implement intervention measures in 12 patients for recovery of SSEP/MEP changes, and SSEP/MEP changes partially/totally recovered in 11 of these 12 patients (91.6%). Postoperative motor deficits were observed in three patients, two of which were Glasgow Outcome Scale level 3 (4.4%). In conclusion, for patients with anterior circulation cerebral aneurysm (H&H grade < 3), multiple intraoperative monitoring was beneficial for finding residual aneurysms, detecting ischaemic events in the perforating arteries and reducing severe postoperative motor deficiency.

Use of intraoperative monitoring of somatosensory evoked potentials to prevent ischaemic stroke after surgical exclusion of middle cerebral artery aneurysms

OBJECTIVE

The aim of this study was to assess the value of monitoring somatosensory evoked potentials (SEP) in the prevention of ischaemic stroke occurring during surgical exclusion of middle cerebral artery aneurysms.

METHODS

SEP monitoring was performed during the surgical exclusion of 131 aneurysms in 122 patients. All SEP variations over 30% were notified to the surgeon and those over 50% were considered as highly significant. If this happened, and in concert with the conduct of the operation, a return to the basal level was systematically sought.

RESULTS

Post-operative ischemic stroke was observed after 15 (11.4%) operations, leading to a permanent neurological deficit in 12 (9.2%). During nine (6.9%) operations there was a highly significant SEP change that persisted, or was only partially reversed, after corrective procedure. Nine of these patients had a post-operative ischaemic stroke. In 25 (19%), operations there was a highly significant SEP change followed by complete recovery. Of these 25 patients, 2 suffered a post-operative ischemic stroke. Following 49 operations (37.4%) with less significant SEP modifications, 4 patients suffered a post-operative stroke (8%). A stroke did not occur in the 48 (36.6%) operations during which there was not a variation in SEP. The strokes were related to temporary clipping in 9 patients to definitive clipping in 3 to sylvian fissure opening in 1 to brain retraction in and to dissection of the aneurysm in 1 (1 case).

CONCLUSION

Changes in the SEP correlated well with the occurrence of post-operative stroke. This early detection of ischemia directs attention to the need for measures such as withdrawal of temporary clipping or identification of another factor (e.g. release of brain retraction or repositioning of an occlusive clip) so that the risk of post-operative is reduced.

Subarachnoid hemorrhage on computed tomography scanning and the development of cerebral vasospasm: the Fisher grade revisited

BACKGROUND

The Fisher grade (FG) is widely used to predict cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). We revisited the grading scale to determine its validity in the era of modern management.

METHODS

We retrospectively reviewed the records of 134 patients with SAH. The amount and distribution of subarachnoid blood on admission computed tomography (CT) scan was quantified according to the FG and compared with development of symptomatic vasospasm.

RESULTS

We reviewed 134 patients (median age, 54) who presented with aneurysmal SAH. Six (5%) were FG 1, 34 (25%) were FG 2, 25 (19%) were FG 3, and 69 (51%) were FG 4. Symptomatic vasospasm developed in no (0%) FG 1, 8 (24%) FG 2, 7 (28 %) FG 3, and 13 (19%) FG 4 patients (28 of 134 total patients; 21%). Development of symptomatic vasospasm was not associated with admission FG, Hunt and Hess grade, age, sex, or location of blood on presenting CT scan. Elevated transcranial Doppler blood flow velocity was associated with blood in the basal cisterns (P = .0047), lateral ventricles (P = .026), or blood in any ventricle (P = .04). Postoperative angiograms were obtained in 57 patients; moderate to severe vasospasm was observed in 5 (15%) FG 2, 6 (24%) FG 3, and 14 (20%) FG 4 patients. Twenty patients (71%) with symptomatic vasospasm had moderate or severe angiographic vasospasm. Angiographic vasospasm was associated with intraventricular blood (P = .054) but not with FG.

CONCLUSIONS

Symptomatic vasospasm occurred in 21% of cases. The FG correlated with symptomatic vasospasm in only half the patients. A new predictive CT grading scale for vasospasm may be necessary.

Prognostic significance of SSEP, BAEP and serum S-100B monitoring after aneurysm surgery

OBJECTIVE

Changes in evoked potentials (EPs) and increased levels of S-100B protein were used to identify cerebral ischemia or glial damage and to predict neurological outcome in aneurysm patients.

MATERIAL AND METHODS

Somatosensory evoked potentials and Brainstem auditory-evoked potentials, and serum S-100B protein were simultaneously investigated pre- and postoperatively over a period of 10 days in 43 patients with 47 aneurysms (six in the posterior fossa).

RESULTS

The EP scores showed a strong correlation with the clinical outcome. Sensitivity was 73%, and specificity 81%. Pathological S-100B levels >0.5 mg/l were equal in predictive values (correct positive eight, false positive six, correct negative 26, false negative three). Initially increased S-100B levels, long-lasting S-100B elevation, and secondary increasing S-100B values correlated with an unfavorable outcome. High peak S-100B values correlated with bad EP scores at discharge. EP deterioration was the first indicator anticipating S-100B elevation and clinical deterioration in five patients. There was a good correlation between pathological S-100B values or EP findings and infarction on CT scan.

CONCLUSIONS

Both EPs and S-100B protein showed a comparable high predictive value for outcome. S-100B reflects the extent of primary brain damage after subarachnoid hemorrhage and time course of ongoing secondary brain damage. Evoked potentials assess the functional integrity and tended to react earlier than S-100B protein before definitive structural damage occurred.