INTRODUCTION:Linked Quadripolar Stimulation (LQP) is a recent adaptation of transcranial electric motor evoked potential stimulation, with proposed advantages over traditional Bipolar (BP) stimulation. This study aims to comprehensively compare BP and LQP stimulation to validate the efficacy of LQP. METHODS:BP and LQP stimulation were performed on 30 patients undergoing anterior cervical discectomy and fusion. A comprehensive assessment involved conducting four trials for each technique on each patient. An Accelerometer placed over the right masseter region recorded movement. A Mann-Whitney U test and Pearson Correlation Coefficient were used to quantitatively compare patient movement, compound muscle action potential (CMAP) response amplitude, and area under the curve (AUC) values. RESULTS:TCMEP recordings were successfully obtained from the entire sample. No statistical significance was found between patient movement, amplitude, or area under the curve (AUC) between BP and LQP stimulation. A weak correlation was found between patient movement and stimulation intensity for both techniques. A strong correlation was found between amplitude and AUC values. CONCLUSION:Patient movement and stimulation parameters showed similar outcomes between BP and LQP. LQP did not demonstrate reduced movement compared to BP stimulation. This study contributes valuable insights into the effectiveness of BP and LQP stimulation in anterior cervical discectomy and fusion surgery.
Injury to the recurrent laryngeal nerve (RLN) during anterior cervical spine surgery is an uncommon yet impactful sequela. This study evaluates the feasibility and intraoperative behavior of laryngeal adductor reflex (LAR) and motor-evoked potentials with vocalis recordings (MEP-VC) during anterior cervical spine surgery. LAR and MEP-VC were employed for 13 patients undergoing anterior cervical spine surgery. LAR alerts were issued when clinically correlated reductions in amplitude, typically ≥20% in previously stable, non-habituating recordings, and/or temporal dispersion of the LAR waveform occurred. MEP-VC alerts were issued for a ≥50% isolated decrease in amplitude or any amplitude reduction that occurred concurrently with an LAR amplitude decline. LAR alerts were observed in five surgeries, with four showing recovery to baseline. In one case, with no LAR recovery, this patient demonstrated post-operative hoarseness. Conversely, another case showed persistent MEP-VC deterioration, despite LAR recovery following the intervention. This patient exhibited right vocal fold paralysis, diagnosed with incomplete glottic closure by an otolaryngologist. All other patients exhibited no RLN deficits post-surgery. Our proof-of-concept study demonstrates the feasibility of LAR and MEP-VC monitoring and suggests that these modalities may provide physiologically relevant information regarding RLN function during anterior cervical spine surgery.
Somatosensory evoked potentials (SSEPs) are used in spinal surgeries to monitor the functional integrity of dorsal column medial lemniscal pathways. Changes to waveform amplitudes can be due to surgical manipulation, in addition to many outside factors. We describe a posterior lumbar decompression/fusion case in which lower extremity (LE) SSEPs were performed and deteriorated bilaterally. These changes were found to be related to a safety strap traversing the posterior thighs that was excessively tight, causing neurological dysfunction. After loosening the strap, SSEP amplitudes and latencies returned to baseline parameters. This observation demonstrates the importance of careful patient positioning and application of external restraints. Numerous reports have described upper extremity (UE) positioning issues, but there are few that detail LE positioning issues. Intraoperative neuromonitoring (IONM) clinicians should be aware of various potential effects of improper positioning on IONM data and be vigilant in recognizing these instances.
Needle-shaped occipital spikes are most often described in children with cortical visual impairment or congenital blindness. We report the case of a 5-year-old child with developmental delay, microcephaly based on an occipitofrontal circumference below the 3rd percentile, and recurrent dystonic movements. Despite the reduced head size, MRI of the brain and spine showed no additional structural abnormalities beyond the microcephaly, and her vision was clinically normal. She underwent ambulatory EEG for episodes of abnormal posturing. The study showed low-voltage, surface-negative spikes maximal at O2 that persisted throughout the recording without associated clinical events, while background activity remained normal. Although these discharges have features that may resemble benign EEG variants, their interpretation should be cautious given the patient's developmental and neurological background. Recognizing such patterns and interpreting them in the full clinical context is essential to prevent misdiagnosis and unnecessary antiepileptic therapy.
Repetitive electrical stimulation of the femoral nerve to record F-waves from the vastus lateralis (VL) muscle can cause significant pain in some participants. This study aimed to develop a method for recording F-waves from the VL with minimal discomfort by adjusting the position of the stimulating electrode. Fifteen healthy participants were recruited. The cathode was positioned at two locations: one at the center of the thigh and the other slightly lateral to it, targeting the physiological motor point of the distal VL. The anode was placed on the lateral thigh, and the recording electrode was placed on the distal VL. F-waves were elicited at each site, with the stimulus intensity set at 1.2 times the level required to elicit the maximum M-wave amplitude. Stimulus duration was 0.2 ms, frequency was 0.2 Hz, and 30 stimuli were delivered per trial. Pain levels were immediately assessed using a visual analogue scale (VAS). The following parameters were analyzed: stimulus intensity, VAS scores, M-wave amplitude, F-wave persistence, F-wave mean latency, F-wave mean amplitude, and F/M amplitude ratio. Stimulation at the lateral site resulted in reduced stimulus intensity, VAS scores, M-wave amplitude, and F-wave persistence compared to the center site. F-wave mean amplitude and the F/M amplitude ratio were higher, while F-wave latency remained unchanged. Shifting the cathode slightly lateral to the center of the thigh enabled F-wave recordings from the VL with lower stimulation intensity and reduced pain. However, changes in M-wave and F-wave parameters were observed.
The National Association of Epilepsy Centers mandates that epilepsy monitoring unit (EMU) patient observers must always be present to minimize risk of patient injury during admissions. To comply with this requirement, our staffing model and workflow were adjusted accordingly. Upon activation of the event button, rather than attending to EMU patients in person, the patient observer responded verbally through the room's speaker system and subsequently contacted nursing staff via a Vocera™ device. This study evaluates the efficiency of this model by measuring the time between event button (PB) activation, observer response, and subsequent evaluation by either nursing staff or physicians. We retrospectively reviewed video EEG files for all available PBs on EMU patients admitted between January 1 and December 31, 2023, and calculated the intervals between PB activation, patient observer's response, and in-person attendance by the health care provider. Patient demographics and event details were examined for statistical differences. Of 129 admissions (402 PBs), the median observer response time was 15 seconds, which increased with age (14 s, 16 s, and 20 s for <45, 45-64, and ≥65 yo, respectively; p = .027). The average time for a nurse or a physician to physically attend to the patient was 94 s (range, 4 to 1808 s). The average observer's response to psychogenic non-epileptic seizures (PNES) was faster (10 s) than responses to epileptic seizures (14 s), accidents (15 s), and other events (17 s) (p < .001). There was no difference in response time between sexes (p = .870) or races (p = .197). Although patient observer response time was short, only 15% of PBs were seizure-related, while > 50% were accidental. These findings highlight the need to critically evaluate EMU staffing models to maintain compliance with the safety requirements, improve the accuracy of seizure detection, and to meet overall goals of EMU evaluation.
BACKGROUND:Spinal cord stimulation (SCS) is a common therapeutic approach for treating intractable chronic pain. A key factor determining SCS efficacy is lead positioning to generate paresthesias in areas of perceived pain. There are two distinct approaches to confirming appropriate coverage. 1) Sedative anesthesia with local anesthetic and intraoperative patient reporting of pain coverage. 2) General anesthesia and intraoperative neurophysiological mapping. Placement guided by neuromonitoring decreases OR times, produces more accurate placement with better pain coverage, less excess paresthesias and adverse events. We aim to determine the prevalence of non-awake SCS placement with neuromonitoring in Canada, given the demonstrated benefits, and to identify possible barriers to implementation. METHODS:A structured questionnaire was designed to assess procedures for SCS implantation in Canada. The survey was distributed via email to members of the Canadian Neuromodulation Society. RESULTS:14 responses were received. 36% perform SCS implantation asleep with neuromonitoring where 75% utilize CMAPs and 25% utilize SSEP collisions. 71% have access to a neurophysiologist yet 93% are at centres where neurophysiologists are used for other procedures. Barriers to utilizing neurophysiologist assisted lead placement include familiarity with the awake procedure, and lack of access and awareness. CONCLUSION:This survey provides a summary of SCS implantation practice patterns in Canada. Although asleep SCS implantation with neuromonitoring is faster and results in more accurate placement while avoiding downsides of the awake procedure, most neurosurgeons currently do not utilize this protocol in part due to a lack of access to neurophysiologists with expertise in this area.
Deep brain stimulation (DBS) has significantly advanced the treatment of moderate to severe motor symptoms in conditions such as Parkinson's disease and essential tremor. Although DBS is generally considered a safe and effective therapy, selecting suitable candidates requires careful diagnostic evaluation and ensuring a stable neuropsychiatric baseline. Effective patient counseling is crucial, as it helps manage expectations regarding the potential benefits, the limitations of DBS, and the typical timeline for symptom improvement. This counseling is as important as the precision in surgical targeting to achieve optimal therapeutic outcomes. Once DBS is implanted, the remaining adjustable component is the programming of the device, which plays a vital role in patient response. Despite the absence of formal programming algorithms, various studies have provided collective insights into best practices, offering guidance on how to approach device programming for improved results. The aim of this review is to equip clinicians with valuable practical knowledge to enhance the management of patients undergoing DBS therapy, ultimately optimizing patient outcomes. By understanding the complexities of patient selection, surgical placement, and ongoing device management, clinicians can better tailor DBS interventions to individual needs and maximize the long-term benefits of the therapy.
Peripheral nerve stimulation (PNS) is defined as the application of electric stimulation to the peripheral nervous system and to a specific nerve. For the most part, the goal of PNS has been treatment of pain. Later, PNS use expanded to indications other than pain including epilepsy and depression, which involves stimulation of the vagus nerve, sleep apnea with stimulation of the hypoglossal nerve, respiratory insufficiency, involving phrenic nerve stimulation, and many others. The overarching peripheral neuromodulation approach involves three modalities: conventional PNS, which implies direct placement of stimulating electrode leads over the affected peripheral nerve(s); percutaneous PNS, which implies insertion of stimulating electrode leads near the target nerve with appropriate guidance; and peripheral nerve field stimulation, which requires placement of electrode leads to stimulate smaller nerves and nerve endings in the affected target area. Monitoring peripheral nerves during surgery through electrophysiological methods is a highly valuable option, offering crucial real-time information to the surgical team. While preoperative testing provides helpful data for decision-making, intraoperative neurophysiological monitoring (IONM) fills in gaps that cannot be addressed by preoperative studies. IONM assesses the nervous system during surgery to prevent potential damage to critical neurological structures. It serves the next main purposes: detecting and minimizing iatrogenic injuries, mapping nervous structures to identify the target nerve, and assessing the functionality of the nerve. In this article we review currently available information about the utilization of IONM during PNS procedures.
Chiari malformation types 1 and 1.5 can be treated with posterior fossa decompression, though surgical techniques vary considerably, with more aggressive approaches often considered for type 1.5. Given this variability, an objective intraoperative marker of adequate decompression would support more tailored surgery. While brainstem auditory evoked potentials (BAEPs) have been explored in pediatric populations, their utility in adults remains unstudied. We present a 26-year-old female with Chiari 1.5 and symptoms including migraines, visual disturbances, balance issues, and right-hand clumsiness. She underwent a BAEP-guided, minimally invasive decompression involving a C1 laminectomy, linear dural opening, and tonsillar cauterization. Intraoperative BAEP monitoring allowed for a targeted, less extensive decompression, resulting in significant clinical improvement. This case highlights the potential utility of BAEPs in adult Chiari decompression, suggesting a role for further investigation of this technique in optimizing outcomes while minimizing invasiveness.
