A Study on the Evaluation of Brainstem Dysfunction in Rapid Eye Movement Sleep Behavior Disorder Using Video Nystagmography

Background@#This study aimed to differentiate video nystagmography (VNG) characteristics, including the video head impulse test (vHIT), in patients with idiopathic rapid eye movement behavior disorder (RBD) from healthy controls, which is considered a precursor to degenerative diseases. @*Methods@#One hundred eighty-five patients underwent overnight polysomnography (PSG) and VNG. Based on overnight PSG, 27 patients with RBD or REM sleep without atonia (RWA) and AHI<15 were categorized into the RBD group, 34 patients with RBD/RWA and AHI≥15 were grouped into the combined group. Sixty patients with AHI≥15 and no RBD/RWA were included in the obstructive sleep apnea (OSA) group, and 64 negative participants were assigned to the control group. In VNG, we measured the gain of vHIT in each canal, with the latency, amplitude, and velocity of horizontal saccades and smooth pursuit. We compared the results between groups using ANOVA, after normalization and adjustment for age and sex. @*Results@#The gain of vHIT in the left horizontal canal was decreased in the RBD group, but it was more pronounced in the OSA group. Elevated gain of the left posterior canal was seen in the RBD group, but technical errors were attributable. The RBD group displayed prolonged latency of saccade on the left side and slowed saccade on the right side, but these were statistically insignificant. @*Conclusions@#The VNG study revealed differences between the sleep disorders, potentially reflecting brainstem function in each disorder. However, these differences lacked statistical significance. We anticipate that significant results could be obtained with more controlled conditions.

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.

Intraoperative Neurophysiological Monitoring during Microvascular Decompression Surgery for Hemifacial Spasm

Hemifacial spasm (HFS) is due to the vascular compression of the facial nerve at its root exit zone (REZ). Microvascular decompression (MVD) of the facial nerve near the REZ is an effective treatment for HFS. In MVD for HFS, intraoperative neurophysiological monitoring (INM) has two purposes. The first purpose is to prevent injury to neural structures such as the vestibulocochlear nerve and facial nerve during MVD surgery, which is possible through INM of brainstem auditory evoked potential and facial nerve electromyography (EMG). The second purpose is the unique feature of MVD for HFS, which is to assess and optimize the effectiveness of the vascular decompression. The purpose is achieved mainly through monitoring of abnormal facial nerve EMG that is called as lateral spread response (LSR) and is also partially possible through Z-L response, facial F-wave, and facial motor evoked potentials. Based on the information regarding INM mentioned above, MVD for HFS can be considered as a more safe and effective treatment.

Intraoperative Neurophysiological Monitoring during Microvascular Decompression Surgery for Hemifacial Spasm

Hemifacial spasm (HFS) is due to the vascular compression of the facial nerve at its root exit zone (REZ). Microvascular decompression (MVD) of the facial nerve near the REZ is an effective treatment for HFS. In MVD for HFS, intraoperative neurophysiological monitoring (INM) has two purposes. The first purpose is to prevent injury to neural structures such as the vestibulocochlear nerve and facial nerve during MVD surgery, which is possible through INM of brainstem auditory evoked potential and facial nerve electromyography (EMG). The second purpose is the unique feature of MVD for HFS, which is to assess and optimize the effectiveness of the vascular decompression. The purpose is achieved mainly through monitoring of abnormal facial nerve EMG that is called as lateral spread response (LSR) and is also partially possible through Z-L response, facial F-wave, and facial motor evoked potentials. Based on the information regarding INM mentioned above, MVD for HFS can be considered as a more safe and effective treatment.

Hepatic Myelopathy Involving the Posterior Column

Hepatic myelopathy is a rare neurological complication of chronic liver disease, and is characterized by a progressing spastic paraparesis without any sensory loss. However, a few recent reports suggest that involvement of the sensory system is also possible in hepatic myelopathy. We present a patient with hepatic myelopathy, who had impaired proprioception and a delayed cortical response of somatosensory evoked potentials. This supports the hypothesis that hepatic myelopathy may involve the sensory system as well as the motor system.