Blink synkinesis monitoring during microvascular decompression for hemifacial spasm

Advancing Intraoperative Neurophysiological Monitoring With Human Reflexes

Human reflexes are simple motor responses that are automatically elicited by various sensory inputs. These reflexes can provide valuable insights into the functioning of the nervous system, particularly the brainstem and spinal cord. Reflexes involving the brainstem, such as the blink reflex, laryngeal adductor reflex, trigeminal hypoglossal reflex, and masseter H reflex, offer immediate information about the cranial-nerve functionality and the overall state of the brainstem. Similarly, spinal reflexes such as the H reflex of the soleus muscle, posterior root muscle reflexes, and sacral reflexes provide crucial information about the functionality of the spinal cord and peripheral nerves. One of the critical benefits of reflex monitoring is that it can provide continuous feedback without disrupting the surgical process due to no movement being induced in the surgical field. These reflexes can be monitored in real time during surgical procedures to assess the integrity of the nervous system and detect potential neurological damage. It is particularly noteworthy that the reflexes provide motor and sensory information on the functional integrity of nerve fibers and nuclei. This article describes the current techniques used for monitoring various human reflexes and their clinical significance in surgery. We also address important methodological considerations and their impact on surgical safety and patient outcomes. Utilizing these methodologies has the potential to advance or even revolutionize the field of intraoperative continuous monitoring, ultimately leading to improved surgical outcomes and enhanced patient care.

Beyond the observation of all or nothing: The clinical significance of the pre-decompression instability of abnormal muscle response in Microvascular decompression for Hemifacial spasm

BACKGROUND

In microvascular decompression (MVD) surgery, abnormal muscle response (AMR) monitoring was utilized to confirm sufficient decompression. However, the AMR seems to contain more information that could improve surgical results.

METHOD

Patients' records of HFS treated with MVD under AMR monitoring, from January 2018 to December 2019 in our centre, were retrospectively reviewed. MVD procedures were performed via a suboccipital retrosigmoid approach, and AMR monitoring was performed. Pre-Decompression Instability (PDI) of AMR before the final decompression, including amplitude inconsistency and waveform chaos, was inspected and notified to the surgeon.

RESULT

165 cases were found with full follow-up data. In these cases, PDI was recognized in 144 cases. And in the remaining 21 cases, the AMR disappeared abruptly or continued to exist to the end of the MVD surgery. When PDI appeared, the rate of electrophysiological relief was significantly higher (91.7 % vs 66.7 %, P = 0.001). In cases with PDI appearance during MVD procedure, the rate of neurological dysfunction was lower (13.2 % vs 38.1 %, P = 0.004). The relief rate the PDI group tended to be higher without statistical significance.

CONCLUSION

The appearance and observation of pre-decompression instability of AMR monitoring made a positive impact on the surgical outcomes of MVD surgeries. The advent of PDI indicates that the key step of the procedure has arrived. The timely notification of the PDI advent improved the surgical outcomes of MVD surgery by increasing the electrophysiological relief rate, reducing the incidence of neurological dysfunction, and possible elevation of the relief rate. Therefore, continuous intra-operative communication between the surgeon and electrophysiological monitoring staff should be encouraged.

Advances in Intraoperative Neurophysiology During Microvascular Decompression Surgery for Hemifacial Spasm

Microvascular decompression (MVD) is a widely used surgical intervention to relieve the abnormal compression of a facial nerve caused by an artery or vein that results in hemifacial spasm (HFS). Various intraoperative neurophysiologic monitoring (ION) and mapping methodologies have been used since the 1980s, including brainstem auditory evoked potentials, lateral-spread responses, Z-L responses, facial corticobulbar motor evoked potentials, and blink reflexes. These methods have been applied to detect neuronal damage, to optimize the successful decompression of a facial nerve, to predict clinical outcomes, and to identify changes in the excitability of a facial nerve and its nucleus during MVD. This has resulted in multiple studies continuously investigating the clinical application of ION during MVD in patients with HFS. In this study we aimed to review the specific advances in methodologies and clinical research related to ION techniques used in MVD surgery for HFS over the last decade. These advances have enabled clinicians to improve the efficacy and surgical outcomes of MVD, and they provide deeper insight into the pathophysiology of the disease.