Transcranial motor evoked potential monitoring during the surgical clipping of unruptured intracranial aneurysms

doi:10.1016/j.jns.2010.03.013

Journal of the Neurological Sciences

Volume 293, Issues 1–2, 15 June 2010, Pages 29-34

https://doi.org/10.1016/j.jns.2010.03.013 Get rights and content

Abstract

Objective

The aim of the present study was to evaluate the usefulness of transcranial motor evoked potential (MEP) monitoring and its impact on morbidity after surgical clipping of unruptured intracranial aneurysms.

Methods

Motor outcomes were compared before and after the application of MEP monitoring for a one year period. A total intravenous anesthesia was induced and maintained with a continuous infusion of vecuronium. Muscle MEPs were elicited by constant voltage stimulation via subdermal needle electrodes placed at C3 and C4 positions. A more than 50% decrement of MEP amplitudes compared with baseline recordings was regarded as a warning sign and promptly indicated to the surgeon.

Results

Before the application of MEP monitoring, a new motor deficit was observed in 3 of 66 patients. However, in 98 patients operated under MEP monitoring, no new motor deficit was found except for one patient who manifested delayed hemiparesis 30 h after the operation owing to a cortical vein injury during craniotomy. MEPs deteriorated in 12 patients which were related to hypotension (n = 1), temporary clipping (n = 7), and permanent clipping (n = 4), and recovered in all after prompt corrective measures. After surgical clipping of unruptured aneurysms, the absence of new motor deficits could be reliably anticipated by recovered MEPs as well as unchanged MEPs.

Conclusions

Transcranial MEP monitoring is a simple, safe, and reliable tool for the prediction of postoperative motor functions. The ischemic complications can be reduced via prompt corrective measures taken on the basis of MEP changes during aneurysm surgery.

Introduction

Because aneurysm surgery always poses potential risks of ischemic complications, continuous somatosensory evoked potential (SSEP) monitoring has been adopted to identify patients with impending ischemia early during surgery, to enable the surgeon to react in time. However, SSEP monitoring cannot detect isolated damage to structures outside the lemniscal system, at least in theory. Thus, a significant rate up to 10% of cases with new postoperative motor deficits has been observed after surgery for anterior circulation aneurysms, despite unaltered intraoperative SSEP recordings [1], [2], [3], [4].

Consequently, the need for monitoring of the motor pathway was raised and several former studies demonstrated the feasibility of motor evoked potential (MEP) monitoring during aneurysm surgery either elicited by transcranial [3], [5], [6] or direct cortical stimulation [7], [8], [9]. On the basis of MEP changes, the surgeon was able to take corrective measures (e.g. release the clip or retractor blade), which could lead to recovery of deteriorated MEPs in many instances. In some situations, however, the patients suffered hemiparesis despite unchanged or fully recovered MEPs [3], [5], [6], [7], [8], [9]. Thus, the reliability of MEP monitoring is still in doubt. Besides, its impact on the motor outcome has never been studied apart from the enormous effects of subarachnoid and intracerebral hemorrhages. The inclusion of the ruptured cases possibly obscures the surgical results by means of vasospasm, pre-existing hemiparesis, uneven clinical grades, difficulties in exposure and dissection, premature rupture and so on.

We compared motor outcomes before and after the application of transcranial MEP monitoring for a one year period. Only unruptured aneurysms were enrolled in this study population and motor outcomes were correlated with the relevant MEP changes to assess the positive and negative predictive values in a prospective observational design.

Section snippets

Patient population

This study covered the period from January 2007 to December 2008. Transcranial MEP monitoring together with SSEP has routinely been performed for aneurysm surgery in our institute since mid-December 2007. There were only two exceptional cases treated without MEPs monitoring after that, which were operated on an emergent basis. Ruptured cases and aneurysms located in the posterior circulation were excluded to eliminate the effects of hemorrhages and different surgical approaches. Also, cases

Results

Demographic and angiographic profiles are summarized in Table 1. The number of cases treated under MEP monitoring increased. This reflects a recent tendency that surgery for unruptured aneurysms is increasingly performed, in combination with our own policy, which favors open surgery of middle cerebral artery (MCA) aneurysms over endovascular coiling. Nevertheless, no statistical difference was demonstrated between the two cohorts (each p value > 0.5).

In the former surgical cohort, a new

Impact of MEP monitoring on motor outcomes

Aneurysm surgery always poses potential risks of ischemic complications, which encompass unintentional vessel occlusion by the permanent clip, temporary occlusion for proximal control, iatrogenic vasospasm or thromboembolism by surgical manipulation, small vessel injury during dissection, and local ischemia during brain retraction [10], [11], [12]. Thus, even for unruptured aneurysms located in the anterior circulation, the risk of a new postoperative motor deficit still exists in approximately

Conclusions

Conflicts of interest

We have no conflicts of interest to disclose.

Financial disclosure

We have nothing to declare.

References (20)

A. Szelenyi et al.
Transcranial and direct cortical stimulation for motor evoked potential monitoring in intracerebral aneurysm surgery
Neurophysiol Clin
(2007)
D.O. Wiebers et al.
Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment
Lancet
(2003)
D.D. Langeloo et al.
Criteria for transcranial electrical motor evoked potential monitoring during spinal deformity surgery: a review and discussion of the literature
Neurophysiol Clin
(2007)
N.R. Holland
Subcortical strokes from intracranial aneurysm surgery: implications for intraoperative neuromonitoring
J Clin Neurophysiol
(1998)
K.T. Min et al.
The monitoring of somatosensory evoked potentials and neurologic complications in aneurysm surgery
Yonsei Med J
(2001)
G. Neuloh et al.
Monitoring of motor evoked potentials compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery
J Neurosurg
(2004)
H. Wiedemayer et al.
False negative findings in intraoperative SEP monitoring: analysis of 658 consecutive neurosurgical cases and review of published reports
J Neurol Neurosurg Psychiatry
(2004)
A. Quinones-Hinojosa et al.
Transcranial motor evoked potentials during basilar artery aneurysm surgery: technique application for 30 consecutive patients
Neurosurgery
(2004)
A. Szelenyi et al.
Monitoring of muscle motor evoked potentials during cerebral aneurysm surgery: intraoperative changes and postoperative outcome
J Neurosurg
(2006)
K. Horiuchi et al.
Intraoperative monitoring of blood flow insufficiency during surgery of middle cerebral artery aneurysms
J Neurosurg
(2005)

There are more references available in the full text version of this article.

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In treating anterior choroidal artery (AChA) aneurysms, preserving the AChA main trunk is of course necessary to prevent postoperative ischemic complications. However, in practice, complete occlusions are often limited by small branches.
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The decision for treatment for unruptured intracranial aneurysms (UIAs) is often difficult. Innovation in endovascular devices have improved the benefit-to-risk profile especially for elderly patients; however, the treatment guidelines from the past decade often recommend conservative management. It is unknown how these changes have affected the overall age of the patients selected for treatment. Herein, we aimed to study potential changes in the average age of the patients that are being treated over time.
A systematic search of the literature was performed to identify all studies describing the age of the UIAs that were treated by any modality. Scatter diagrams with trend lines were used to plot the age of the patients treated over time and assess the presence of a potential significant trend via statistical correlation tests.
A total of 280 studies including 83,437 UIAs treated between 1987 and 2021 met all eligibility criteria and were entered in the analysis. Mean age of the patients was 55.5 years, and 70.7% were female. There was a significant increasing trend in the age of the treated patients over time (Spearman r: 0.250; P < 0.001), with a 1-year increase in the average age of the treated patients every 5 years since 1987.
The present study indicates that based on the treated UIA patient data published in the literature, older UIAs are being treated over time. This trend is likely driven by safer treatments while suggesting that re-evaluation of certain UIA treatment decision scores may be of great interest.
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Preventing possible complications during brain aneurysm surgery is mandatory to ensure a better outcome for patients. Currently, it is possible to rely on some technologic innovations such as motor evoked potential, endoscope-assisted surgery, dye with indocyanine green, and video angiography capable of supporting the surgeon's work. The innovation process has mainly assisted the endovascular technique compared with surgery. The latter, apart from some new technical expedients, always requires anatomic knowledge and optimal technical preparation. A careful patient selection, adequate surgical exposure, use of microsurgical techniques in expert hands, and meticulous postoperative management represent the key to success for the surgical treatment of cerebral aneurysms.
Stroke due to middle cerebral artery aneurysm clipping when the intraoperative angiogram was normal
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An intraoperative angiogram (IOA) may be used to check the clipping of middle cerebral artery (MCA) aneurysms. This study analyzes the occurrence of a stroke when the IOA was normal as this has not been looked into before.
The records of all patients with a normal IOA after MCA aneurysm clipping were reviewed. Patients who woke up with a stroke were selected for this study and analyzed in detail.
Thirty-one patients with 34 aneurysms had a normal IOA. Of those, 7 woke up with a new deficit from perforator or small artery ischemia resulting in a stroke rate of 22.6%. Five out of the 7 strokes were potentially avoidable.
An IOA is still an important tool to check the adequacy of clip placement. However, our experience has taught us that the intent to use it should not lessen the amount of time spent dissecting and exposing the aneurysm as completely as possible. The urge to clip the neck and hope that the IOA will be favorable, when the aneurysm is not maximally exposed, should be resisted. Ideally, a full 360 degrees dissection of the aneurysm should be done to identify perforators and small arteries en passage before clipping. If this had been done, it is likely that the stroke rate would have dropped towards 6.5%.
Intraoperative neurophysiological monitoring in aneurysm clipping: Does it make a difference? A systematic review and meta-analysis
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Citation Excerpt :
Indeed, the goal of clipping is to exclude the aneurysm saving the patency of parent and perforating arteries to avoid ischemic brain injuries. In this regard, the reported mortality rate of unruptured aneurysms ranges between 0.4 % and 1.5 %, and the mortality rate of ruptured aneurysms is up to 50 % [1–4]. Morbidity rates of microsurgery for unruptured intracranial aneurysms range from 2.2 % to 21.0 %, and new motor deficit related to ischemic complications is reported up to 7.6 % [3].
The use of intraoperative neurophysiological monitoring (IOM) has been proposed to prevent new neurological deficit during aneurysm clipping. The purpose of this meta-analysis was to evaluate if IOM can prevent neurological injury during clipping of intracranial aneurysm. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews and meta-analysis, we reviewed clinical comparative studies who evaluate the rate of new neurological deficit in patients who had a surgical clipping with and without IOM. Of the 268 citations screened, four studies (including 873 patients) met the inclusion criteria and were included in the meta-analysis. Patients who received surgery with IOM had less new neurological deficit than those who underwent surgery without it (p = 0,04). This finding was more significant in the subgroup analysis of two studies focused on middle cerebral artery (MCA) aneurysm (p = 0,02). However, a specific analysis of the three studies reporting the results of IOM to prevent permanent deficit revealed that there is only a trend for less neurological events in monitored patients without statistically significance (p = 0,05). The use of IOM during clipping of intracranial aneurysm was associated with less new neurological deficit with the obtained evidence of the included studies. However, at long-term follow-up the use of IOM did not correlate with a significant improvement in neurological outcome.
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Citation Excerpt :
Especially, IONM detects insufficient blood flow quantitatively during an aneurysm surgery. The efficacy of IONM has been reported in several studies; IONM using SSEPs and MEPs had higher diagnostic accuracy in predicting blood flow insufficiency [13,17,28]. Therefore, it is considered a useful and reliable tool to prevent postoperative ischemic complications.
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From January 2011 to March 2018, the neurophysiological, clinical, and radiological data of 115 patients who underwent microsurgical clipping for an unruptured AChA aneurysm under IONM were retrospectively analyzed. The incidence of ischemic complications after microsurgical clipping of unruptured AChA aneurysms as well as the false-negative rate, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of IONM during surgery were calculated.
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View full text

Transcranial motor evoked potential monitoring during the surgical clipping of unruptured intracranial aneurysms

Abstract

Objective

Methods

Results

Conclusions

Introduction

Section snippets

Patient population

Results

Impact of MEP monitoring on motor outcomes

Conclusions

Conflicts of interest

Financial disclosure

Neurophysiol Clin

Lancet

Neurophysiol Clin

Subcortical strokes from intracranial aneurysm surgery: implications for intraoperative neuromonitoring

J Clin Neurophysiol

The monitoring of somatosensory evoked potentials and neurologic complications in aneurysm surgery

Yonsei Med J

Monitoring of motor evoked potentials compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery

J Neurosurg

False negative findings in intraoperative SEP monitoring: analysis of 658 consecutive neurosurgical cases and review of published reports

J Neurol Neurosurg Psychiatry

Transcranial motor evoked potentials during basilar artery aneurysm surgery: technique application for 30 consecutive patients

Neurosurgery

Monitoring of muscle motor evoked potentials during cerebral aneurysm surgery: intraoperative changes and postoperative outcome

J Neurosurg

Intraoperative monitoring of blood flow insufficiency during surgery of middle cerebral artery aneurysms

J Neurosurg