Upregulation of Nav1.8 in demyelinated facial nerves might be relevant to the generation of hemifacial spasm

Pathogenesis and Therapy of Neurovascular Compression Syndromes: An Editorial

Neurovascular compression syndromes (NVC) remains a challenging disorders resulting from the compression of cranial nerves at the transition zone [...].

The blink reflex and its modulation - Part 2: Pathophysiology and clinical utility

The blink reflex (BR) is integrated at the brainstem; however, it is modulated by inputs from various structures such as the striatum, globus pallidus, substantia nigra, and nucleus raphe magnus but also from afferent input from the peripheral nervous system. Therefore, it provides information about the pathophysiology of numerous peripheral and central nervous system disorders. The BR is a valuable tool for studying the integrity of the trigemino-facial system, the relevant brainstem nuclei, and circuits. At the same time, some neurophysiological techniques applying the BR may indicate abnormalities involving structures rostral to the brainstem that modulate or control the BR circuits. This is a state-of-the-art review of the clinical application of BR modulation; physiology is reviewed in part 1. In this review, we aim to present the role of the BR and techniques related to its modulation in understanding pathophysiological mechanisms of motor control and pain disorders, in which these techniques are diagnostically helpful. Furthermore, some BR techniques may have a predictive value or serve as a basis for follow-up evaluation. BR testing may benefit in the diagnosis of hemifacial spasm, dystonia, functional movement disorders, migraine, orofacial pain, and psychiatric disorders. Although the abnormalities in the integrity of the BR pathway itself may provide information about trigeminal or facial nerve disorders, alterations in BR excitability are found in several disease conditions. BR excitability studies are suitable for understanding the common pathophysiological mechanisms behind various clinical entities, elucidating alterations in top-down inhibitory systems, and allowing for follow-up and quantitation of many neurological syndromes.

The Underlying Pathogenesis of Neurovascular Compression Syndromes: A Systematic Review

Neurovascular compression syndromes (NVC) are challenging disorders resulting from the compression of cranial nerves at the root entry/exit zone. Clinically, we can distinguish the following NVC conditions: trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia. Also, rare cases of geniculate neuralgia and superior laryngeal neuralgia are reported. Other syndromes, e.g., disabling positional vertigo, arterial hypertension in the course of NVC at the CN IX-X REZ and torticollis, have insufficient clinical evidence for microvascular decompression. The exact pathomechanism leading to characteristic NVC-related symptoms remains unclear. Proposed etiologies have limited explanatory scope. Therefore, we have examined the underlying pathomechanisms stated in the medical literature. To achieve our goal, we systematically reviewed original English language papers available in Pubmed and Web of Science databases before 2 October 2021. We obtained 1694 papers after eliminating duplicates. Only 357 original papers potentially pertaining to the pathogenesis of NVC were enrolled in full-text assessment for eligibility. Of these, 63 were included in the final analysis. The systematic review suggests that the anatomical and/or hemodynamical changes described are insufficient to account for NVC-related symptoms by themselves. They must coexist with additional changes such as factors associated with the affected nerve (e.g., demyelination, REZ modeling, vasculature pathology), nucleus hyperexcitability, white and/or gray matter changes in the brain, or disturbances in ion channels. Moreover, the effects of inflammatory background, altered proteome, and biochemical parameters on symptomatic NVC cannot be ignored. Further studies are needed to gain better insight into NVC pathophysiology.

Treatment of Trigeminal Neuralgia with "Microvascular Decompression Plus" Technique

Objective  Although microvascular decompression (MVD) has been widely accepted as an effective treatment of trigeminal neuralgia (TN), some patients have not been cured. To improve the postoperative outcome, the surgical procedure should be further refined. Design  This is a retrospective study. Setting  Present study conducted at a cranial nerve disorder center. Participants  Clinical data were collected from patients with TN who had undergone surgery in our center, including 685 who had undergone traditional MVD and 576 who had undergone the "MVD plus" procedure, in which any vessel attached to the trigeminal nerve was freed away ("nerve-combing"), which was followed by intraoperative neurolysis. Main Outcome Measures  Postoperative outcomes and complications in the two groups were compared. Results  Among patients who underwent traditional MVD, the rates of immediate relief and 1-year relief were 89.9 and 86.9%, respectively; among patients who underwent MVD plus group, these rates were 95.1 and 94.6%, respectively ( p  = 0.05). Patients who underwent MVD plus initially exhibited a higher rate of facial numbness ( p  < 0.05), but this finding decreased over time and reached the same level as that in the traditional MVD group within 3 months ( p  > 0.05). Conclusion  Sufficient MVD with nerve-combing for the treatment of TN may produce a high rate of cure with less recurrence.

A correlative analysis between inflammatory cytokines and trigeminal neuralgia or hemifacial spasm

BACKGROUND

It is necessary to understand the mechanism of trigeminal neuralgia (TN) and hemifacial spasm (HFS) in order to seek for an effective noninvasive remedy. As previous studies implied that inflammatory cytokines induced by demyelination following the nerve injury may be the initiated factor causing neuropathic pain, we attempt to analyze the correlation between cytokines and these hyperactive cranial nerve disorders.

METHOD

The consecutive patients whose diagnosis were confirmed by microvascular decompression surgery as primary TN or HFS caused by vascular compression and healthy volunteers between March and May 2018 in XinHua Hospital Shanghai JiaoTong University School of Medicine were recruited. Preoperatively, venous blood was collected and the protein concentrations of IL-1β, IL-2, IL-6, IL-8, IL-10, TNF-α and IFN-γ were determined with ELISA. Each cytokine was compared between the patients and healthy volunteers.

RESULTS

Ultimately, 28 healthy volunteers as well as 44 TN and 47 HFS patients were enrolled in this investigation. The serum levels of IL-1β, IL-6, IL-8 and TNF-α in either HFS or TN patients were significantly higher than that in healthy volunteers (p < 0.05), yet which were similar between TN and HFS patients (p > 0.05). Besides, there was a significantly correlation between IL-6 concentration and severity of HFS (r = 0.933, p < 0.05) or TN (r = 0.943, p < 0.05).

DISCUSSION

Vascular compression of trigeminal or facial nerve roots may induce a rise in variety of cytokines, and IL-6 may play an important role in the signaling pathways to generate ectopic impulses from these cranial nerves.

Management of symptomatic hemifacial spasm or trigeminal neuralgia

Hemifacial spasm (HFS) or trigeminal neuralgia (TN) is a kind of hyperactivity disorder of cranial nerves caused by vascular compression. However, sometimes, the disease may arise from nerve damage produced by tumors, which was called as symptomatic HFS/TN. Until now, little is known about the exact mechanism and the necessity of microvascular decompression (MVD) regarding the tumor-induced HFS/TN, which is necessary to be retrospectively analyzed in a considerable sample. Among the 4021 patients who underwent MVD in our department between 2006 and 2014, 44 were finally diagnosed as symptomatic HFS or TN. These patients were focused in this study and their clinical features as well as intraoperative findings and postoperative outcomes were retrospectively investigated. Data analysis exhibited the symptomatic HFS/TN cases accounted for 1.1 % in the study, which were caused by epidermoid in 18 (40.9 %) and meningioma in 15 (34.1 %) followed by neuroma in 7 (15.9 %) as well as aneurysm in 2 (4.5 %) and arteriovenous malformation in 2 (4.5 %). Compared to those with idiopathic HFS/TN, younger females were more susceptible (p < 0.05). After resection of the neoplasm, the offending vessel was identified in 26 (59.1 %), which were followed by MVD process. Postoperatively, the symptoms relief rate was 88.6 %. Our study showed that surgical management of patients with symptomatic HFS/TN may lead to a satisfactory result, yet those primary lesions should be removed firstly. In some cases, a microvascular decompression process might be unnecessary afterward, but the entire nerve root should be checked to exclude any vessel in contact with.