Tag: Monitoring

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Intraoperative surveillance of the vertebral artery using indocyanine green angiography and Doppler sonography in craniovertebral junction surgeries

Neurosurg Focus 50 (1):E5, 2021

The authors sought to evaluate the usefulness of indocyanine green (ICG) angiography and Doppler sonography for monitoring the vertebral artery (VA) during craniovertebral junction (CVJ) surgery and compare the incidence of VA injury (VAI) between the groups with and without the monitoring of VA using ICG angiography and Doppler sonography.

METHODS In total, 344 consecutive patients enrolled who underwent CVJ surgery. Surgery was performed without intraoperative VA monitoring tools in 262 cases (control group) and with VA monitoring tools in 82 cases (monitoring group). The authors compared the incidence of VAI between groups. The procedure times of ICG angiography, change of VA flow velocity measured by Doppler sonography, and complication were investigated.

RESULTS There were 4 VAI cases in the control group, and the incidence of VAI was 1.5%. Meanwhile, there were no VAI cases in the monitoring group. The procedure time of ICG angiography was less than 5 minutes (mean [± SD] 4.6 ± 2.1 minutes) and VA flow velocity was 11.2 ± 4.5 cm/sec. There were several cases in which the surgical method had to be changed depending on the VA monitoring. The combined use of ICG angiography and Doppler sonography was useful not only to monitor VA patency but also to assess the quality of blood flow during CVJ surgery, especially in the high-risk group of patients.

CONCLUSIONS The combined use of ICG angiography and Doppler sonography enables real-time intraoperative monitoring of the VA by detecting blood flow and flow velocity. As the arteries get closer, they provide auditory and visual feedback to the surgeon. This real-time image guidance could be a useful tool, especially for high-risk patients and inexperienced surgeons, to avoid iatrogenic VAI during any CVJ surgery.

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Role of electrophysiology in guiding near-total resection for preservation of facial nerve function in the surgical treatment of large vestibular schwannomas

J Neurosurg 128:903–910, 2018

In large vestibular schwannoma (VS) surgery, the facial nerve (FN) is at high risk of injury. Near-total resection has been advocated in the case of difficult facial nerve dissection, but the amount of residual tumor that should be left and when dissection should be stopped remain controversial factors. The objective of this study was to report FN outcome and radiological results in patients undergoing near-total VS resection guided by electromyographic supramaximal stimulation of the FN at the brainstem.

METHODS This study was a retrospective analysis of a prospectively maintained database. Inclusion criteria were surgical treatment of a large VS during 2014, normal preoperative FN function, and an incomplete resection due to the strong adherence of the tumor to the FN and the loss of around 50% of the response of supramaximal stimulation of the proximal FN at 2 mA. Facial nerve function and the amount and evolution of the residual tumor were evaluated by clinical examination and by MRI at a mean of 5 days postoperatively and at 1 year postoperatively.

RESULTS Twenty-five patients met the inclusion criteria and were included in the study. Good FN function (Grade I or II) was observed in 16 (64%) and 21 (84%) of the 25 patients at Day 8 and at 1 year postoperatively, respectively. At the 1-year follow-up evaluation (n = 23), 15 patients (65%) did not show growth of the residual tumor, 6 patients (26%) had regression of the residual tumor, and only 2 patients (9%) presented with tumor progression.

CONCLUSIONS Near-total resection guided by electrophysiology represents a safe option in cases of difficult dissection of the facial nerve from the tumor. This seems to offer a good compromise between the goals of preserving facial nerve function and achieving maximum safe resection.

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The diagnostic accuracy of brain microdialysis during surgery

Microdialysis

Acta Neurochir (2013) 155:345–353

Monitoring of brain function and metabolism during surgery may be of benefit for patient outcome. Microdialysis is the only sampling technique to date that allows continuous monitoring of drug or metabolite concentrations in the extracellular fluid of multiple tissues in the brain. This qualitative systematic review aimed to determine whether microdialysis is a valid tool for detecting changes in tissue composition as would be expected upon changes in (induced) tissue metabolic composition during brain surgery.

Methods A systematic review was conducted by performing a MEDLINE search using the terms “Intraoperative Period” (Medical Subject Heading [MeSH]) OR “Surgery” [Subheading] OR “Monitoring, Intraoperative” [MeSH] AND “Microdialysis” [MeSH] AND “Brain” [MeSH]. Two reviewers independently assessed the methodological quality of the studies. For each study the grades of recommendation were determined.

Results The search strategy yielded 46 publications in Medline. Data extraction was performed on 16 studies. The methodological quality of studies was low, with overall scores of 4 or 5. A quantitative analysis could not be performed because of lack of sufficient data. A qualitative analysis was positive with regard to the detection of different states of tissue composition by microdialysis. However, the levels of recommendation on the outcome statements were low, resulting in a grade D level of recommendation on all statements.

Conclusions The available evidence for the validity of cerebral microdialysis as a diagnostic tool during brain surgery is of low scientific quality. In order to develop cerebral microdialysis as a valid instrument for monitoring of brain metabolism during surgery, standardised clinical prospective studies in homogeneous patient populations are required.

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A Real-Time Monitoring System for the Facial Nerve

Neurosurgery:June 2010 – Volume 66 (6):1064–1073. DOI:10.1227/01.NEU.0000369605.79765.3E

Damage to the facial nerve during surgery in the cerebellopontine angle is indicated by A-trains, a specific electromyogram pattern. These A-trains can be quantified by the parameter “traintime,” which is reliably correlated with postoperative functional outcome. The system presented was designed to monitor traintime in real-time.

METHODS: A dedicated hardware and software platform for automated continuous analysis of the intraoperative facial nerve electromyogram was specifically designed. The automatic detection of A-trains is performed by a software algorithm for real-time analysis of nonstationary biosignals. The system was evaluated in a series of 30 patients operated on for vestibular schwannoma.

RESULTS: A-trains can be detected and measured automatically by the described method for real-time analysis. Traintime is monitored continuously via a graphic display and is shown as an absolute numeric value during the operation. It is an expression of overall, cumulated length of A-trains in a given channel; a high correlation between traintime as measured by real-time analysis and functional outcome immediately after the operation (Spearman correlation coefficient [ρ] = 0.664, P < .001) and in long-term outcome (ρ = 0.631, P < .001) was observed.

CONCLUSION: Automated real-time analysis of the intraoperative facial nerve electromyogram is the first technique capable of reliable continuous real-time monitoring. It can critically contribute to the estimation of functional outcome during the course of the operative procedure.

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