Trigeminal Root Research Articles

A study to evaluate neurovascular conflict of trigeminal nerve in trigeminal neuralgia patients with the help of 1.5\xa0T MR imaging

IntroductionTrigeminal neuralgia is a neuropathic pain that occurs in the sensory supply region of the trigeminal nerve (V cranial nerve). The common etiology of trigeminal neuralgia is said to be vascular compression on the trigeminal nerve root. In our day-to-day practice, we see many asymptomatic patients having vascular loops around the trigeminal nerve root. We undertook this study to see the significance of nerve root compression by the vascular loop as a cause for trigeminal neuralgia.Materials and methodsA total of 67 classical trigeminal neuralgia patients with NVC involving the trigeminal nerve as diagnosed on MRI brain sequences including FIESTA sequence were included in the study. NVC in all the patients were studied for the side, site of neurovascular contact of cisternal segment of the trigeminal nerve from the brainstem, deviation of nerve at NVC, atrophy of nerve, nature and origin of vascular loop causing NVC and correlated with TGN symptoms.ResultsOut of 67 patients studied, all of them (100%) had NVC on ipsilateral side and 26 patients (34%) had NVC at contralateral trigeminal nerve. Incidence of trigeminal neuralgia was most commonly seen between the 41 and 60 years age (64%) followed by 61–80 years with mean age of 55.6 years. Incidence in females (64%) was found to be more common than in males (35%). NVC was observed at the root entry zone (< 7 mm from brain stem) in 63 trigeminal nerves on symptomatic side and 5 trigeminal nerves on the asymptomatic side. NVC occurring at REZ on symptomatic side was found to be statistically significant with P < 0.001. Mean distance of NVC from brain stem at symptomatic side was 3.4 mm and was 8.4 mm in asymptomatic side NVCs. Atrophy was seen in 8 trigeminal nerves, all on symptomatic side and NVC occurring at root entry zone. No displacement of nerve root at the point of neurovascular contact was observed in our study. Most common vessel causing was found to be ipsilateral superior cerebellar artery followed by the ipsilateral anterior inferior cerebellar artery.ConclusionsNeurovascular contact of trigeminal nerve occurring at the nerve root entry zone has a strong association with ipsilateral trigeminal neuralgia symptoms. In addition, the presence of the trigeminal nerve thinning is also associated with ipsilateral trigeminal neuralgia. With the increase in age, there are higher chances of association of NVC with ipsilateral trigeminal neuralgia symptoms.

A Preliminary Study of the Efficacy of Transcranial Direct Current Stimulation in Trigeminal Neuralgia.

The purpose of this study is to assess the efficacy of transcranial direct current stimulation (tDCS) in patients with treatment-refractory trigeminal neuralgia (TN) and examine the utility of neuroimaging methods in identifying markers of such efficacy. Six patients with classical TN refractory to maximal medical treatment, underwent tDCS (three cases inhibitory/cathodic and three cases excitatory/anodic stimulation). All patients underwent pre- and posttreatment functional magnetic resonance imaging (fMRI) during block-design tasks (i.e., Pain, Pain + tDCS, tDCS) as well as single-shell diffusion MRI (dMRI) acquisition. The precise locations of tDCS electrodes were identified by neuronavigation. Five therapeutic tDCS sessions were carried out for each patient with either anodic or cathodic applications. The Numeric Rating Scale of pain (NRS) and the Headache Disability Index (HDI) were used to score the subjective efficacy of treatment. Altered activity of regional sites was identified by fMRI and associated changes in the spinothalamocortical sensory tract (STCT) were measured by the dMRI indices of fractional anisotropy (FA) and mean diffusivity (MD). Fiber counts of the bilateral trigeminal root entry zone (REZ) were performed as an added measure of fiber loss or recovery. All patients experienced a significant reduction in pain scores with a substantial decline in HDI (P value < 0.01). Following a course of anodic tDCS, the ipsilateral caudate, globus pallidus, somatosensory cortex, and the contralateral globus pallidus showed a significantly attenuated activation whereas cathodic tDCS treatment resulted in attenuation of the thalamus and globus pallidus bilaterally, and the somatosensory cortex and anterior cingulate gyrus contralaterally. dMRI analysis identified a substantial increase (>50%) in the number of contralateral sensory fibers in the STCT with either anodic or cathodic tDCS treatment in four of the six patients. A significant reduction in FA (>40%) was observed in the ipsilateral REZ in the posttreatment phase in five of the six patients. Preliminary evidence suggests that navigated tDCS presents a promising method for alleviating the pain of TN. Different patterns of activation manifested by anodic and cathodic stimulation require further elaboration to understand their implication. Activation and attenuation of responses at various sites may provide further avenues for condition treatment.

Treatment of redo-microvascular decompression or internal neurolysis plus microvascular decompression for recurrent trigeminal neuralgia: a review of long-term effectiveness and safety.

ObjectiveWe examined the clinical characteristics and outcomes of patients with recurrent trigeminal neuralgia (TN) and assessed the long-term efficacy and safety of microvascular decompression (MVD) to treat typical recurrent TN.MethodsWe identified 3024 patients who underwent MVD for treatment of TN at the China-Japan Friendship Hospital from March 2009 to December 2020. We retrospectively analyzed the data and outcomes of 137 patients who underwent redo-MVD and 74 patients who did not undergo redo-MVD as the control group. These outcomes were evaluated using the Barrow Neurological Institute scoring system.ResultsRecurrence in 68 of the 137 patients was due to incomplete or absent decompression or new responsible vessels. To ensure thorough pain relief, redo-MVD should include decompression of both the trigeminal root entry zone and the peripheral nerve segments, where blood vessels can cause symptoms. Factors associated with reduced effectiveness of redo-MVD were no period of initial pain relief after the first MVD and a longer duration of symptoms before the first MVD.ConclusionsRedo-MVD should not be excluded as a treatment option for patients with refractory TN who develop recurrent pain after a first MVD procedure.

Hyperintense areas in the cisternal segments of the cranial nerves: a magnetic resonance imaging study.

The study aimed to explore hyperintense areas in the cisternal segments of the cranial nerves using magnetic resonance imaging (MRI). Seventy outpatients underwent thin-sliced, coronal constructive interference steady-state (CISS) sequence and sagittal T2-weighted MRI following conventional MRI examination. With the coronal CISS sequence, hyperintense areas were located in the central parts of the olfactory bulbs in 65.7% of patients. For the intracranial optic nerve and optic chiasm, hyperintense areas were detected in 98.6% of the CISS sequences and 100% of the T2-weighted images. In the optic tract, hyperintense areas were detected in 51.4% of cases. In 35% of the patients who underwent the CISS sequence, the intracranial optic nerves were considerably compressed by the internal carotid and anterior cerebral arteries, with hyperintense areas similar to those in patients without vascular compression. Hyperintense areas of the cisternal segments of the oculomotor nerve and trigeminal root were identified in 52.9% and 87.1% of the patients, respectively. The hyperintense areas found within the cisternal segments of the cranial nerves delineated on the coronal CISS sequence and sagittal T2-weighted imaging may indicate the intracranial part of the glymphatic pathway through the cranial nerves. The cranial nerves may function as part of the glymphatic pathway.

Efficiency and Efficacy of Real-Time Fluoroscopic Image-Guided Percutaneous Gasserian Glycerol Rhizotomy (PGGR), for Intractable Cases of Trigeminal Neuralgia.

To evaluate the ease, efficiency, effectiveness, and associated complications of the technique of percutaneous Gasserian glycerol rhizotomy (PGGR) under real-time fluoroscopic image guidance, for management of severe and refractory cases of primary trigeminal neuralgia, in medical compromised patients. To also assess the long-term efficacy and the necessity, if any, for repeat procedures to salvage recurrences. In a prospective study conducted at a single institution over a period of three years, 25 cases of Idiopathic Trigeminal Neuralgia refractory to conservative modalities of treatment including medication were managed with PGGR under real-time fluoroscopic image guidance. All the 25 patients included in this study were known surgical risks for relatively invasive treatment procedures, owing to factors such as advanced age and/or presence of co-morbidities. In order to minimize the risks related to the conventional techniques of Trigeminal root rhizotomy based on cutaneous landmarks alone, and to eliminate the need for frequent repositioning of the needle/cannula, we adopted a technique of real-time fluoroscopic image-guided negotiation of a 22 gauge (0.7mm dia), 10-cm-long spinal nerve block needle through the foramen ovale, to reach the trigeminal cistern within the Meckel's cave. The efficiency of the technique was assessed in terms of time taken, effort, and ease in performing it. Associated intra- and post-procedural complications were recorded. The immediate and long-term effectiveness of the procedure was evaluated by analysing the degree and duration of pain control achieved, time to recurrence, and the necessity for repeat procedures. There were nil intra- or post-procedural complications encountered, and no failures associated with this procedure. Real-time fluoroscopic imaging enabled easy, quick, and successful negotiation of the nerve-block needle through the Foramen Ovale, so as to reach the Trigeminal cistern within the Meckel's cave, within 11min on an average. An immediate and long lasting post-procedural pain relief was achieved in all the patients. During the follow-up period of 36months, recurrence of pain was observed in six cases, the mean timing of the recurrence being 26months or more. Five of these cases were manageable with medication alone, and only one required a repeat procedure. These results indicate that PGGR under real-time fluoroscopic image guidance is a safe, simple, time-efficient, convenient, efficacious, reliable, and minimally invasive means of treating refractory and intractable cases of trigeminal neuralgia.

Serpinin in the Skin.

The serpinins are relatively novel peptides generated by proteolytic processing of chromogranin A and they are comprised of free serpinin, serpinin-RRG and pGlu-serpinin. In this study, the presence and source of these peptides were studied in the skin. By Western blot analysis, a 40 kDa and a 50 kDa protein containing the sequence of serpinin were detected in the trigeminal ganglion and dorsal root ganglia in rats but none in the skin. RP-HPLC followed by EIA revealed that the three serpinins are present in similar, moderate amounts in rat dorsal root ganglia, whereas in the rat skin, free serpinin represents the predominant molecular form. There were abundant serpinin-positive cells in rat dorsal root ganglia and colocalization with substance P was evident. However, much more widespread distribution of the serpinins was found in dorsal root ganglia when compared with substance P. In the skin, serpinin immunoreactivity was found in sensory nerves and showed colocalization with substance P; as well, some was present in autonomic nerves. Thus, although not exclusively, there is evidence that serpinin is a constituent of the sensory innervation of the skin. The serpinins are biologically highly active and might therefore be of functional significance in the skin.

Neurapraxia in patients with trigeminal neuralgia but no identifiable neurovascular conflict during microvascular decompression: a retrospective analysis of 26 cases

BackgroundMicrovascular decompression (MVD) is the first choice in patients with classic trigeminal neuralgia (TGN) that could not be sufficiently controlled by pharmacological treatment. However, neurovascular conflict (NVC) could not be identified during MVD in all patients. To describe the efficacy and safety of treatment with aneurysm clips in these situations.Methods A total of 205 patients underwent MVD for classic TGN at our center from January 1, 2015 to December 31, 2019. In patients without identifiable NVC upon dissection of the entire trigeminal nerve root, neurapraxia was performed using a Yasargil temporary titanium aneurysm clip (force: 90 g) for 40 s (or a total of 60 s if the process must be suspended temporarily due to bradycardia or hypertension).ResultsA total of 26 patients (median age: 64 years; 15 women) underwent neurapraxia. Five out of the 26 patients received prior MVD but relapsed. Immediate complete pain relief was achieved in all 26 cases. Within a median follow-up of 3 years (range: 1.0–6.0), recurrence was noted in 3 cases (11.5%). Postoperative complications included hemifacial numbness, herpes labialis, masseter weakness; most were transient and dissipated within 3–6 months.ConclusionsNeurapraxia using aneurysm clip is safe and effective in patients with classic TGN but no identifiable NVC during MVD. Whether this method could be developed into a standardizable method needs further investigation.

Gadolinium chelates inhibit intracellular calcium signaling in rat trigeminal ganglion neurons similar to rat dorsal root ganglion neurons, but less effective

Objectives: Gadolinium (Gd3+) based MR contrast agents (GBMCA) are manufactured with a chelation process, where organic ligand molecules form a stable complex around Gd3+. The aim of the present study was to investigate the possible impact of free gadolinium and GBMCA in ganglia (trigeminal and dorsal root) neuron cell cultures on intracellular calcium (Ca2+) since these agents could dissociate and lead to the release of toxic Gd3+ ions in metabolic conditions. Methods: Ganglia cells were studied for responses to agents and nonspecific depolarization by high KCl+ in Fura 2 AM loaded neurons by monitoring the changes in [Ca2+]i using a microscopic digital image analysis system. GBMCA and molecular gadolinium doses of 0.1 mmol/kg were prepared with the same pH and temperature and applied to the cells. Results: Application of Gd3+, gadobenate dimeglumine, gadobutrol and gadodiamide to rat ganglia neurons led to significant decreases in basal intracellular calcium levels, while gadoterate meglumine administration did not have a significant impact. As expected, Gd3+ was more effective when compared tı GBMCA. While the impact was almost full with gadodiamide, Gd3+ and other GBMCAs had irreversible effects at different levels. The impact of gadoterate meglumine was neglectable when compared to Gd3+ and other GBMCAs, although it exhibited slightly gadodiamide-like effects. Conclusions: In conclusion, gadolinium chelates released gadolinium and irreversibly reduced the intracellular calcium levels in identical TG and DRG cells at different levels.

Unearthing what lies beneath: A case series of 2 patients with secondary trigeminal neuralgia

Trigeminal Neuralgia also known as Tic Douloureux or Fothergill's disease is one of the most commonly encountered neuralgic pain in a dental set-up. Although the cause is unknown for most of the times, vascular compression of trigeminal nerve roots is one of the most commonly accepted etiology for the same. In some cases, clinical feature of trigeminal neuralgia have been seen secondary to those of other intracranial causes such as epidermoid tumor, multiple sclerosis etc. This is known as secondary trigeminal neuralgia. In this case series, we describe 2 cases of secondary trigeminal neuralgia and discuss the importance of MRI as an essential diagnostic approach in cases of TN.

White matter volume loss drives cortical reshaping after thalamic infarcts

ObjectiveThe integration of somatosensory, ocular motor and vestibular signals is necessary for self-location in space and goal-directed action. We aimed to detect remote changes in the cerebral cortex after thalamic infarcts to reveal the thalamo-cortical connections necessary for multisensory processing and ocular motor control. MethodsThirteen patients with unilateral ischemic thalamic infarcts presenting with vestibular, somatosensory, and ocular motor symptoms were examined longitudinally in the acute phase and after six months. Voxel- and surface-based morphometry were used to detect changes in vestibular and multisensory cortical areas and known hubs of central ocular motor processing. The results were compared with functional connectivity data in 50 healthy volunteers. ResultsPatients with paramedian infarcts showed impaired saccades and vestibular perception, i.e., tilts of the subjective visual vertical (SVV). The most common complaint in these patients was double vision or vertigo / dizziness. Posterolateral thalamic infarcts led to tilts of the SVV and somatosensory deficits without vertigo. Tilts of the SVV were higher in paramedian compared to posterolateral infarcts (median 11.2° vs 3.8°). Vestibular and ocular motor symptoms recovered within six months. Somatosensory deficits persisted. Structural longitudinal imaging showed significant volume reduction in subcortical structures connected to the infarcted thalamic nuclei (vestibular nuclei region, dentate nucleus region, trigeminal root entry zone, medial lemniscus, superior colliculi). Volume loss was evident in connections to the frontal, parietal and cingulate lobes. Changes were larger in the ipsilesional hemisphere but were also detected in homotopical regions contralesionally. The white matter volume reduction led to deformation of the cortical projection zones of the infarcted nuclei. ConclusionsWhite matter volume loss after thalamic infarcts reflects sensory input from the brainstem as well the cortical projections of the main affected nuclei for sensory and ocular motor processing. Changes in the cortical geometry seem not to reflect gray matter atrophy but rather reshaping of the cortical surface due to the underlying white matter atrophy.

Automated Segmentation of Trigeminal Nerve and Cerebrovasculature in MR-Angiography Images by Deep Learning.

Trigeminal neuralgia caused by paroxysmal and severe pain in the distribution of the trigeminal nerve is a rare chronic pain disorder. It is generally accepted that compression of the trigeminal root entry zone by vascular structures is the major cause of primary trigeminal neuralgia, and vascular decompression is the prior choice in neurosurgical treatment. Therefore, accurate preoperative modeling/segmentation/visualization of trigeminal nerve and its surrounding cerebrovascular is important to surgical planning. In this paper, we propose an automated method to segment trigeminal nerve and its surrounding cerebrovascular in the root entry zone, and to further reconstruct and visual these anatomical structures in three-dimensional (3D) Magnetic Resonance Angiography (MRA). The proposed method contains a two-stage neural network. Firstly, a preliminary confidence map of different anatomical structures is produced by a coarse segmentation stage. Secondly, a refinement segmentation stage is proposed to refine and optimize the coarse segmentation map. To model the spatial and morphological relationship between trigeminal nerve and cerebrovascular structures, the proposed network detects the trigeminal nerve, cerebrovasculature, and brainstem simultaneously. The method has been evaluated on a dataset including 50 MRA volumes, and the experimental results show the state-of-the-art performance of the proposed method with an average Dice similarity coefficient, Hausdorff distance, and average surface distance error of 0.8645, 0.2414, and 0.4296 on multi-tissue segmentation, respectively.

Flow cytometry analysis of immune and glial cells in a trigeminal neuralgia rat model

Microvascular compression of the trigeminal root entry zone (TREZ) is the main cause of most primary trigeminal neuralgia (TN), change of glial plasticity was previously studied in the TREZ of TN rat model induced by chronic compression. To better understand the role of astrocytes and immune cells in the TREZ, different cell markers including glial fibrillary acidic protein (GFAP), complement C3, S100A10, CD45, CD11b, glutamate-aspartate transporter (GLAST), Iba-1 and TMEM119 were used in the TN rat model by immunohistochemistry and flow cytometry. On the post operation day 28, GFAP/C3-positive A1 astrocytes and GFAP/S100A10-positive A2 astrocytes were activated in the TREZ after compression injury, there were no statistical differences in the ratios of A1/A2 astrocytes between the sham and TN groups. There was no significant difference in Iba-1-positive cells between the two groups. The ratios of infiltrating lymphocytes (CD45+CD11b−) (p = 0.0075) and infiltrating macrophages (CD45highCD11b+) (p = 0.0388) were significantly higher than those of the sham group. In conclusion, different subtypes A1/A2 astrocytes in the TREZ were activated after compression injury, infiltrating macrophages and lymphocytes increased, these neuroimmune cells in the TREZ may participate in the pathogenesis of TN rat model.

Extracellular ATP and cAMP signaling promote Piezo2-dependent mechanical allodynia after trigeminal nerve compression injury.

Trigeminal neuralgia (TN) is a type of severe paroxysmal neuropathic pain commonly triggered by mild mechanical stimulation in the orofacial area. Piezo2, a mechanically gated ion channel that mediates tactile allodynia in neuropathic pain, can be potentiated by a cyclic adenosine monophosphate (cAMP)-dependent signaling pathway that involves the exchange protein directly activated by cAMP 1 (Epac1). To study whether Piezo2-mediated mechanotransduction contributes to peripheral sensitization in a rat model of TN after trigeminal nerve compression injury, the expression of Piezo2 and activation of cAMP signal-related molecules in the trigeminal ganglion (TG) were detected. Changes in purinergic P2 receptors in the TG were also studied by RNA-seq. The expression of Piezo2, cAMP, and Epac1 in the TG of the TN animals increased after chronic compression of the trigeminal nerve root (CCT) for 21days, but Piezo2 knockdown by shRNA in the TG attenuated orofacial mechanical allodynia. Purinergic P2 receptors P2X4, P2X7, P2Y1, and P2Y2 were significantly up-regulated after CCT injury. In vitro, Piezo2 expression in TG neurons was significantly increased by exogenous adenosine 5'-triphosphate (ATP) and Ca2+ ionophore ionomycin. ATP pre-treated TG neurons displayed elevated [Ca2+ ]i and faster increase in responding to blockage of Na+ /Ca2+ exchanger by KB-R7943. Furthermore, mechanical stimulation of cultured TG neurons led to sustained elevation in [Ca2+ ]i in ATP pre-treated TG neurons, which is much less in naïve TG neurons, or is significantly reduced by Piezo2 inhibitor GsMTx4. These results indicated a pivotal role of Piezo2 in peripheral mechanical allodynia in the rat CCT model. Extracellular ATP, Ca2+ influx, and the cAMP-to-Epac1 signaling pathway synergistically contribute to the pathogenesis and the persistence of mechanical allodynia.

Tools for analysis and conditional deletion of subsets of sensory neurons

Background: Somatosensation depends on primary sensory neurons of the trigeminal and dorsal root ganglia (DRG). Transcriptional profiling of mouse DRG sensory neurons has defined at least 18 distinct neuronal cell types. Using an advillin promoter, we have generated a transgenic mouse line that only expresses diphtheria toxin A (DTA) in sensory neurons in the presence of Cre recombinase. This has allowed us to ablate specific neuronal subsets within the DRG using a range of established and novel Cre lines that encompass all sets of sensory neurons. Methods: A floxed-tdTomato-stop-DTA bacterial artificial chromosome (BAC) transgenic reporter line (AdvDTA) under the control of the mouse advillin DRG promoter was generated. The line was first validated using a Na v1.8 Cre and then crossed to CGRP CreER (Calca), Th CreERT2, Tmem45b Cre, Tmem233 Cre, Ntng1 Cre and TrkB CreER (Ntrk2) lines. Pain behavioural assays included Hargreaves’, hot plate, Randall-Selitto, cold plantar, partial sciatic nerve ligation and formalin tests. Results: Motor activity, as assessed by the rotarod test, was normal for all lines tested. Noxious mechanosensation was significantly reduced when either Na v1.8 positive neurons or Tmem45b positive neurons were ablated whilst acute heat pain was unaffected. In contrast, noxious mechanosensation was normal following ablation of CGRP-positive neurons but acute heat pain thresholds were significantly elevated and a reduction in nocifensive responses was observed in the second phase of the formalin test. Ablation of TrkB-positive neurons led to significant deficits in mechanical hypersensitivity in the partial sciatic nerve ligation neuropathic pain model. Conclusions: Ablation of specific DRG neuronal subsets using the AdvDTA line will be a useful resource for further functional characterization of somatosensory processing, neuro-immune interactions and chronic pain disorders.

Hemimasticatory spasm. Own experience of using botulinum neuroprotein type A

Нemimasticatory spasm (HMS) is a rare disorder of the nervous system, in which there are unilateral, violent spasms of the masticatory muscles innervated by the motor portion of the trigeminal nerve. The causes of HMS remain largely unexplored, but microvascular compression is most likely. Anticonvulsants, surgical treatment and botulinum therapy can be applied for the treatment of HMS.We presented a clinical case of HMS in a 38-year-old woman who had been suffering from this disease for 18 years. The diagnosis of HMS was established only 10 years after the first visit to the doctor. Spasms could occur up to several hundred times a day with a duration up to 15 seconds. The magnetic resonance imaging allowed to exclude neurovascular conflict. Electroneuromyography revealed axonal lesion of the right trigeminal motor root and spontaneous activity in the right masseter muscle. Anticonvulsant treatment was ineffective. The patient received botulinum therapy with a good treatment result.

Post SRS Reversal of Masticator Muscles Atrophy in Idiopathic Trigeminal Neuralgia

The trigeminal nerve conducts both sensory and motor impulses through sensory root (50 fascicles) and motor root of wrisberg (about 6-7 fascicles). Separate superior and inferior motor roots typically emerge from the pons just antero-superomedial to the entry point of the sensory root. Motor nerve root of trigeminal nerve receives considerable radiation dose during SRS. Purpose of the study is to evaluate MRI the changes in the muscles of mastication before and after SRS in patients with idiopathic Trigeminal neuralgia MATERIALS/METHODS: Data analysis was limited to 23 patients over the age of 65 years who had undergone a first-time frameless SRS for the treatment of idiopathic TN with at least 1 year of follow-up between 2015 and 2019. Standardized collection of preoperative demographics, radiosurgical dosimetric data, and postoperative outcomes was performed. Detailed CISS / 3D TOF sequences were acquired to study the neurovascular conflict zones. In addition, MRI the thicknesses of the temporalis, pterygoid, and masseter muscles were measured on both pre- and post-SRS MRI in a blinded fashion. Changes in the muscles like fatty infiltration, MRI signal, or atrophy were noted. Logistic regression analysis was used to define the parameters like site of contact of offending vessels, number of motor roots involved, pain distribution zones and preop BNI score which mostly influenced masticator muscle atrophy.The median follow-up was 26 months (range 13- 60 months). On MR imaging while sensory roots were identified in 100% pts, in 13 pts (56%) single motor root, 8 pts (35%) had two motor roots, and remaining pts (9%) had three motor roots identified by neuroradiologist. Among the 23 patients eligible for inclusion in the study, 46 temporalis muscles, 46 medial pterygoid muscles, 46 lateral pterygoid muscles, and 46 masseter muscles were assessed. Pre-SRS atrophy of the masseter, medial pterygoid, lateral pterygoid, and temporalis muscles was seen in 7 (31%), 6 (26%), 4 (17%), and 6 (26%) patients, respectively. Logistic regression analysis showed that distribution of pain in the involvement of at least 2 motor nerve roots (P = 0.01, OR 5.34, 95% CI 1.8 - 19.12), superior cerebellar artery contact (P = 0.01, OR 5.43, 95% CI 1.46-20.12), V3 territory (P = 0.01, OR 5.27, 95% CI 1.21-20.67) and significant pain on chewing (P = 0.02, OR 5.32, 95% CI 1.25-22.48) were predictive of pre-SRS atrophy. Reversal of atrophy of these muscles occurred after SRS in a 22 of 23 patients post radiosurgery as evident in 1 year follow-up scan. The incidence of new-onset permanent post-SRS muscle atrophy correlated with one patient who had 3 roots and received marginal dose of 82gy.While a subset of patients with TN with significant pain on chewing have pre-SRS disuse atrophy of the muscles of mastication, a reversal of the atrophy occurs in a majority of the patients following SRS. New-onset motor neuropathy post-SRS was rare suggesting to fact that motor roots are very sturdy to surgical doses of radiation.

External Neurolysis in Microvascular Decompression for Magnetic Resonance Imaging–Negative Idiopathic Trigeminal Neuralgia

Internal neurolysis has been proposed as an alternative to microvascular decompression in patients with idiopathic trigeminal neuralgia (TN) in whom neurovascular compression is not confirmed by magnetic resonance imaging (MRI). External neurolysis, which straightens and realigns the trigeminal nerve root axis by dissecting the arachnoid membranes around the nerve, was reported 20 years ago in the context of so-called negative exploration when MRI did not confirm the absence of the offending vessel, but is not currently used. External neurolysis was performed in 4 patients with idiopathic TN with typical evoked neuralgic pain despite the absence of suspected offending vessels on MRI. The surgical findings that caused TN were summarized and the outcomes were evaluated using the Barrow Neurological Institute Pain Intensity Scale (BNI-PS). Tethering and distortion of the nerve root by surrounding arachnoid membranes were commonly found. All 4 patients showed complete pain relief immediately after surgery. During the follow-up period of 26.5 ± 16.92 months (±standard deviation), 3 of 4 patients had no pain (score I, BNI-PS). One patient received a score of IIIa on the BNI-PS assessment. There was no instance of recurrence or side effects associated with the surgery. Idiopathic TN can be induced by individual variation of the surrounding inner arachnoid membranes supporting the trigeminal nerve root, and the condition cannot be identified by MRI. Intradural external neurolysis may be considered an effective treatment for MRI-negative idiopathic TN.

Technical note: A spiral fluid-attenuated inversion recovery magnetic resonance imaging technique for stereotactic radiosurgery treatment planning for trigeminal neuralgia.

Magnetic resonance imaging (MRI) is commonly used in treatment planning for stereotactic radiosurgery (SRS) of trigeminal neuralgia (TN). With current MRI techniques, the delineation of the trigeminal nerve root entry zone (REZ) may be degraded due to poor contrast and artifacts. The purpose of this work is to develop an MRI technique with better delineation of the trigeminal nerve REZ to improve SRS treatment planning for TN. A spiral fluid-attenuated inversion recovery (FLAIR) MRI technique was developed to improve image quality by improving tissue contrast, fluid suppression, artifact reduction, and signal-to-noise ratio (SNR). A concomitant-phase compensation method based on spiral gradient waveforms was implemented to minimize artifacts due to magnetic field change induced by the metal frame used in Gamma Knife treatment planning. The image quality of spiral FLAIR was assessed in four healthy volunteers. The geometric accuracy was quantitatively evaluated by registering spiral FLAIR to computed tomography (CT) images and comparing it with existing MRI techniques. The spiral FLAIR technique demonstrated better delineation of the trigeminal nerve REZ, improved tissue contrast of the brain stem, and minimized flow artifacts, compared to steady-state free precession (SSFP) MRI. Spiral FLAIR also improved fluid suppression, SNR, and artifacts, which contributed to better delineation of the trigeminal nerve REZ compared to conventional Cartesian FLAIR. The measured mean (± standard deviation) distance between spiral FLAIR and CT images is 0.98 ± 0.56mm, comparable to 0.40 ± 0.26mm in 3T T1 spoiled gradient echo (T1-SPGR), 0.59 ± 0.25mm in 3T SSFP, 0.66 ± 0.38mm in 1.5T T1-SPGR, and 0.61 ± 0.25mm in 1.5T Cartesian FLAIR. A spiral FLAIR technique with improved image quality and good geometric accuracy provides a potential alternative for treatment planning in SRS for TN patients.

Comparison of Prognostic Scoring Systems to Predict Durable Pain Relief After Microvascular Decompression for Trigeminal Neuralgia

Microvascular decompression (MVD) is an effective treatment for trigeminal neuralgia, but pain recurs in a substantial minority of patients. Two recently published scoring systems by Hardaway etal. and Panczykowski etal. use simple preoperative clinical and imaging features to predict durable pain relief following MVD, but their predictive performance has not been independently validated. This study aimed to compare predictive performance of the Hardaway etal. score (HS) and Panczykowski etal. score (PS) for 1-year, 3-year, and long-term pain-free outcomes after MVD for trigeminal neuralgia. HS and PS were computed for a retrospective, single-institution cohort of 68 patients with trigeminal neuralgia who underwent MVD. Primary outcome was pain recurrence after MVD. Predictive performance of HSs and PSs was evaluated with area under the curve sensitivity analysis and regression models for survival analyses at 1 year, 3 years, and last follow-up. Area under the curve for predicting pain-free outcome was higher for PS versus HS at 1 year (0.873 vs. 0.775) and 3 years (0.793 vs. 0.704). Cox proportional hazard models showed that PS better predicted long-term pain-free outcomes compared with HS (P < 0.05). One-year pain-free outcome was best predicted by pain type; longer-term outcomes were better predicted by presence and degree of neurovascular compression on preoperative imaging. PS is superior to HS in predicting pain-free outcomes after MVD, which may aid in patient selection and counseling. Overall, more significant neurovascular compression of the trigeminal nerve root, and to a lesser extent classical paroxysmal pain, are good predictors of durable pain relief after MVD.

Historical aspects of the problem of treatment of trigeminal neuralgia and the role of neurosurgical methods in its solution (literature review)

The trigeminal nerve is a mixed fifth cranial nerve, consisting of motor and sensory components. The sensitive component receives somesthetic information from the skin and mucous membranes of the face into the central nervous system, and the motor component is responsible for the innervation of chewing muscles. One of the manifestations of the pathology of the trigeminal nerve is pain syndrome. Trigeminal neuralgia occupies the main place among neurogenic pain syndrome in the face, is characterized by а severe course and the absence of sufficiently effective methods of treatment. According to the World Health Organization (WHO), the prevalence of trigeminal neuralgia in different countries is 2–5 cases per 100 thousand people per year. Trigeminal neuralgia is classified into 3 etiologic categories. Idiopathic trigeminal neuralgia occurs without apparent cause. Classical trigeminal neuralgia is caused by vascular compression of the trigeminal nerve root. Secondary trigeminal neuralgia is the consequence of a major neurologic disease, e. g., a tumor of the cеrеbеllоpоntine angle or multiple sclerosis. Today, there are many different options for the surgical treatment of trigeminal neuralgia. microvascular decompression of the root, radiosurgical destruction of the Gasser’s node, radiofrequency destruction, glycerol rhizotomy, balloon microcompression are considered the main effective and proven surgical methods for treating trigeminal neuralgia. But the questions of diagnosing the cause of the disease and choosing an adequate surgical method for treating therapeutically resistant trigeminal neuralgia for a particular patient remain open. The development of surgical methods begins from ancient times to the present day. The main stages in the development of neurosurgical treatment methods are presented. The following surgical techniques are described: open method – microvascular decompression, and closed percutaneous destructive methods – radiofrequency destruction, glycerol rhizotomy, balloon compression, radiosurgery, cryodestruction, laser destruction, botulinum toxin injections.