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Blink reflex and CoMEPs recording of patient 13. Blink reflex with a latency of 11.35 milliseconds and amplitude of 610 mV appeared in the first train as an R1 component. While removing an epidermoid cyst at the right cerebellopontine angle, BR suddenly vanished (A), and immediate feedback was given to the surgeon. Facial CoMEPs remained stable throughout the surgery (B). The patient showed severe facial dysfunction postoperatively but made a good recovery. BR, blink reflex; CoMEPs, corticobulbar motor evoked potentials.
Source publication
Purpose:
Blink reflex (BR) under general anesthesia as an intraoperative neuromonitoring method was used to monitor facial nerves in few studies. This study aimed to test the utility of intraoperative BR during cerebellopontine angle and skull base surgeries, assess its prognostic value for facial nerve functions, and compare it with facial cortic...
Context in source publication
Context 1
... The other two patients' BR was initially absent, but a preceding "A train" in spontaneous EMG activity was noted, followed by an instantaneous CoMEPs loss (patient 1). In one patient (patient 13), a sudden and permanent loss of BR did not go along with any impairment of CoMEPs, who presented with HB5 scores and recovered 10 months after surgery (Fig. 3). A temporary loss of BR accompanied a temporary deterioration of the trigeminal CoMEPs in one patient, where a spontaneous EMG activity was also seen (patient 17). Both potentials came back after the surgeon paused and irrigated the area, and the patient had a normal neurological examination postoperatively. Facial CoMEPs lost ...
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Citations
... BR is useful in the study of trigeminal and facial nerve lesions, peripheral neuropathy, posterior fossa lesions, multiple sclerosis, and extrapyramidal diseases [51]. Under general anesthesia in the operating room, only the R1 response can be recorded [52][53][54][55]. represents the setup used to stimulate and record the BR (top scheme, green lines) and the LAR (bottom scheme, purple lines), including a schematic representation of the arc reflex pathways (please, note that discontinued lines are used for afferent fibers and continued lines for efferent pathways), and the brainstem structures involved. ...
Chiari malformation type 1 (CM1) includes a series of congenital anomalies that share ectopia of the cerebellar tonsils below the foramen magnum, in some cases associated with syringomyelia or hydrocephalus. CM1 can cause dysfunction of the brainstem, spinal cord, and cranial nerves. This functional alteration of the nervous system can be detected by various modalities of neurophysiological tests, such as brainstem auditory evoked potentials, somatosensory evoked potentials, motor evoked potentials, electromyography and nerve conduction studies of the cranial nerves and spinal roots, as well as brainstem reflexes. The main goal of this study is to review the findings of multimodal neurophysiological examinations in published studies of patients with CM1 and their indication in the diagnosis, treatment, and follow-up of these patients, as well as their utility in intraoperative monitoring.
... For instance, changes in the brainstem laryngeal adductor reflex during endocrine, vagus nerve, and brainstem lesion surgeries correlate with postoperative laryngeal function (Sinclair et al. 2017, Costa et al., 2018Sandler et al., 2019;Sinclair et al., 2021;Téllez et al., 2021). Methodologies for intraoperative monitoring of cranial nerves with other brainstem reflexes such as the blink reflex (Aydinlar et al., 2020;Deletis et al., 2009) and the H reflex of the masseter muscle have also been described. They are widely used in intraoperative monitoring of posterior fossa and brainstem surgeries. ...
... The BR also was sensitive, foreseeing early postoperative neurological weakness. On the other hand, facial CoMEPs were superior in accurately predicting long-term facial nerve functions [23]. ...
Purpose
Schwannoma, a tumor originating from the peripheral nervous system, may arise from the vagus nerve, although it is not very often. Injury of the vagus nerve by surgical attempts may have consequences that will seriously affect the patient’s quality of life. In recent years, continuous monitoring of the laryngeal adductor reflex (LAR) has become a promising methodology for evaluating vagus nerve function intraoperatively. We refer to our experience changing our surgical strategy due to concurrent deterioration in LAR and CoMEPs intraoperatively. We also provide a literature review and summarize the current knowledge of this technique.
Methods
The LAR was elicited and recorded by an electromyographic endotracheal tube in a 36-year-old man diagnosed with vagal nerve schwannoma. Subdermal needle electrodes were placed in both cricothyroid (CTHY) muscles for corticobulbar motor evoked potentials (CoMEPs) recording.
Results
Recordings of ipsilateral LAR and CTHY CoMEPs were obtained despite preoperative ipsilateral cord vocalis weakness. The surgical strategy was altered after the simultaneous decrease of CTHY CoMEPs and LAR amplitudes, and the surgery was completed with subtotal resection. No additional neurological deficit was observed in the patient except dysphonia, which resolved within a few weeks after the surgery.
Conclusions
We conclude that LAR with vagal nerve CoMEPs are two complementary methods and provide reliable information about the functional status of the vagus nerve during surgery.
... For instance, changes in the brainstem laryngeal adductor reflex during endocrine, vagus nerve, and brainstem lesion surgeries correlate with postoperative laryngeal function (Sinclair et al. 2017, Costa et al., 2018Sandler et al., 2019;Sinclair et al., 2021;Téllez et al., 2021). Methodologies for intraoperative monitoring of cranial nerves with other brainstem reflexes such as the blink reflex (Aydinlar et al., 2020;Deletis et al., 2009) and the H reflex of the masseter muscle have also been described. They are widely used in intraoperative monitoring of posterior fossa and brainstem surgeries. ...
Objective
Brainstem trigeminal-hypoglossal reflexes (THRs), also known as the jaw-tongue reflexes, coordinate the position of the tongue in the mouth in relation to the jaw movement during oromotor behaviors such as mastication, swallowing, vocalization, and breathing. Their use in brainstem surgery however, has never been assessed in spite of its potential benefit possibly due to the lack of a methodology to elicit these reflexes under general anesthesia.
Methods
We proposed a technique to elicit the THRs during total intravenous anesthesia (TIVA) consisting on a V3 infrazygomatic train stimulation paradigm and recording from the Styloglossus (31 patients) and the Genioglossus (21 patients) muscles to elicit long latency responses.
Results
The THR was successfully recorded using the V3 stimulation point in 82.1% of patients, of which 96.9% presented a response on the Styloglossus muscle (Jaw-opening reflex) while 0.06% presented a response on the Genioglossus muscle instead (Jaw-closing reflex).
Conclusions
The THRs can be successfully recorded in surgery under general anaesthesia with the predominant reflex seen being the jaw-opening reflex.
Significance
We provide a novel method to elicit the THRs during general anesthesia, which could be of aid in brainstem surgery.
Backgrounds
Blink reflex (BR) is an oligosynaptic reflex that involves the ophthalmic branch of the trigeminal nerve (TN), ipsilateral main sensory and trigeminospinal nuclei, bilateral facial nuclei, and the facial nerves (FN). Theoretically, as it tests the function of both TN and FN simultaneously, it is an ideal tool for monitoring the status of TN and FN during skull base surgeries. Nevertheless, it is only recently utilized in surgeries as the use of anesthesia limits its use.
Methods
Two authors inputted the search terms: [(Blink Reflex) AND (Intraoperative Neuromonitoring OR Neuro Intraoperative Monitoring OR Intraoperative OR NIOM OR IONM) AND (skull base surgery OR Facial Nerve OR Trigeminal Nerve OR Microvascular Decompression OR Hemifacial Spasm)] in Medline through its Pubmed interface and other search engines. Papers that fulfilled the inclusion and exclusion criteria were obtained and scrutinized.
Results
Only 7 observational papers with a total of 437 participants were included in the current systematic review. All studies (n=5) involving the use of BR in FN surgery noted that IOBR is beneficial, safe, sensitive, specific, and predictive of outcomes while all 2 papers involving trigeminal neuralgia patients recommended BR’s use in microvascular decompression (MVD) of TN.
Conclusion
IOBR is a sensitive, specific and safe monitoring technique that has good predictability of facial paresis and paresthesia among patients undergoing MVD for trigeminal neuralgia and primary hemifacial spasm and those who are for cerebellopontine angle tumor resection.
Chiari malformation type 1 (CM1) includes various congenital anomalies that share ectopia of the cerebellar tonsils lower than the foramen magnum, in some cases associated with syringomyelia or hydrocephalus. CM1 can cause dysfunction of the brainstem, spinal cord, and cranial nerves. This functional alteration of the nervous system can be detected by various modalities of neurophysiological tests, such as brainstem auditory evoked potentials, somatosensory evoked potentials, motor evoked potentials, electromyography and nerve conduction studies of the cranial nerves and spinal roots, as well as brainstem reflexes. The main goal of this study is to review the findings of multimodal neurophysiological examinations in published studies of patients with CM1 and their indication in the diagnosis, treatment, and follow-up of these patients, as well as their utility in intraoperative monitoring.
The recording of brainstem reflexes under general anesthesia allows the ability to monitor the sensory and motor function of cranial nerves, pathways, and nuclei within the brainstem, thereby enabling us to functionally observe these essential structures during a wide variety of surgical procedures. This chapter describes methodologies for eliciting the blink reflex, the masseter H reflex, and the laryngeal adductor reflex under general anesthesia. Monitoring these reflexes helps detect impending injuries to the trigeminal, facial, and vagus cranial nerves and brainstem networks.
Objective:
To evaluate the blink reflex (BR) in estimating the potential injury of trigeminal nerve following percutaneous balloon compression (PBC) surgery, and to determine the association between BR alterations and early surgical outcomes.
Methods:
In this single-center, prospective before-and-after study, a total of 74 patients who had primary trigeminal neuralgia and scheduled for PBC between October 2020 and June 2021 were prospectively included. BR testing and facial sensory assessment were performed pre- and post-PBC. The latency and the area under the curve (AUC) of pre- and postoperative R1 (R1pre /R1post ) and R2 (R2pre /R2post ) were measured.
Results:
The BR components were noticeably delayed or diminished following PBC. R1post was elicited in only 26 patients, and absent in 48 patients. The residual R1post had markedly reduced AUC (median difference [Hodges-Lehmann]: -59.5, 95% confidence interval [CI]: -217.5 to -6.9, p = 0.023). Compared with R2pre , the latency of R2post was considerably delayed (mean difference: 4.3, 95% CI: 2.9 to 5.7, p < 0.001) and the AUC was greatly suppressed (median difference [Hodges-Lehmann]: -388.4, 95% CI: -548.4 to -259.5, p < 0.001). After PBC, 58 patients had immediate total pain relief, and 16 had partial relief. The absence of R1post was found in 46 of 58 (79.3%) patients with complete remission, whereas in only 2 of 16 (12.5%) patients with partial relief. Association analysis showed that the absence of R1post was strongly associated with total pain relief (46/58 [79.3%] vs. 2/16 [12.5%], odds ratio [OR]: 26.8, 95% CI: 5.4 to 134.5, Cramér's V: 0.6, p < 0.001). The latency of R2post in patients with total relief was significantly delayed (mean difference: 2.5, 95% CI: 0.3 to 4.6, p = 0.028). Patients experienced graded facial numbness after PBC, of whom 31 reported mild numbness (Grades I-II) and 43 reported more severe numbness (Grades III-IV). The absence of R1post was significantly associated with facial numbness severity, 33/43 (76.7%) in Grades III-IV vs. 15/31 (48.4%) in Grades I-II (OR: 0.284, 95% CI: 0.105 to 0.771, Cramér's V: 0.3, p = 0.012). In patients with more severe numbness, the latency of R2post was significantly delayed (mean difference: 2.7, 95% CI: 0.1 to 5.3, p = 0.043), and the reduction of AUC was much greater (median difference [Hodges-Lehmann]: 17.2, 95% CI: 0.5 to 35.4, p = 0.041).
Conclusion:
Both R1 and R2 were significantly diminished after PBC and these alterations were associated with early surgical outcomes, suggesting that the BR is useful in evaluating trigeminal injury following PBC and could provide objective information about early prognosis.
