Trigeminal Reflex Research Articles

Transient bradycardia during local anaesthesia to the oral cavity under intravenous sedation and its associate factors: a prospective observational study

BackgroundLocal anaesthesia in dental procedures is generally safe, although the occurrence of transient bradycardia (TB) has occasionally been reported. TB is often associated with two reflexes, the trigeminal cardiac reflex (TCR) and the vasovagal reflex (VVR) and is characterised by a rapid decrease in heart rate (HR) and blood pressure (BP). The prevalence of TCR is considered low, and its predictors have not been thoroughly investigated, although an association with the gag reflex has been suggested in recent years.MethodsThis prospective study assessed TB occurrence during local anaesthesia and its potential associated factors. A comprehensive questionnaire was used to categorise discomforts during dental treatment, and various anxiety scales were used to measure patients’ anxiety levels. We investigated HR variability during local anaesthesia administration under sedation and the association between the incidence of TB and gag reflex. Subsequently, logistic regression analysis was performed to assess factors associated with TB occurrence.ResultsThe prospective analysis included 188 patients of 234 initial patients. The analysis revealed a high TB incidence rate of 41% during local anaesthesia administration under sedation. No severe hypotensive events occurred, indicating a relatively benign nature of TB during local anaesthesia. TB occurrence was significantly higher in the group of patients with the gag reflex. Further analysis revealed that both gag reflex and trait anxiety were significantly associated with TB occurrence, whereas dental phobia did not directly correlate with TB.ConclusionThis study highlights the prominent occurrence of TB during local anaesthesia in dental treatment, which is primarily attributed to TCR activation. The identification of gag reflex and trait anxiety as independent factors associated with TB development may pave the way for TB prevention measures. Further research is required to clarify the mechanisms of TCR and perform safer dental procedures under sedation. Future studies should also aim to elucidate the precise mechanisms underlying TB during local anaesthesia through direct measurements of neural activity. A better understanding of TB in dentistry is crucial for improving patient safety and optimising dental practice protocols.

Cardiac Arrest during Temporary Clipping for Ruptured Internal Carotid Artery Aneurysm: A Case Report

Abstract Objectives Mechanical stimulation of the trigeminal nerve during craniofacial, skull base, or dental surgeries may cause bradycardia, hypotension, or cardiac arrest. This phenomenon is called trigeminal cardiac reflex (TCR). We encountered a rare case of a patient who experienced sinus arrest due to temporary clipping of the intracranial carotid artery during the clipping of a ruptured aneurysm. We discuss possible reasons for the occurrence of TCR in this case. Materials and Methods A man in his 30s with no medical history presented with a sudden-onset headache. Computed tomography revealed a subarachnoid hemorrhage in the basal cistern and left Sylvian fissure. Angiography revealed a saccular aneurysm of the left internal carotid-anterior choroidal artery. A left frontotemporal craniotomy and dural incision were performed, followed by a trans-Sylvian approach. Cardiac arrest occurred twice during the temporary clipping of the intracranial carotid artery. After surgery, we performed a cardiac ultrasound echo and a 1-week Holter electrocardiogram. Neither showed abnormalities. No arrhythmia or cardiac events were observed over a one and half-year follow-up period. Results The cardiac arrest might have been triggered by the stimulation of the trigeminal nerve in the internal carotid artery. The repeated and anatomical features of this case suggest that TCR triggered cardiac arrest. Conclusion The high probability that cardiac arrest was induced by trigeminal nerve stimulation should be considered during the temporary clipping of the internal carotid artery. However, the predisposing factors and exact underlying mechanisms for these arrhythmias remain unknown and require further investigation.

Treatment of recurrent trigeminal neuralgia after microvascular decompression: How to select

BackgroundThis study aimed to investigate individualized treatment strategies and clinical outcomes in patients with recurrent trigeminal neuralgia after undergoing microvascular decompression (MVD). MethodsOne hundred forty-four patients with recurrent trigeminal neuralgia after MVD were retrospectively examined and grouped according to treatment. Surgical efficacy and pain recurrence were analyzed as outcomes. ResultsRepeat craniotomy was performed in 31 patients (21.5 %), percutaneous balloon compression (PBC) in 67 (46.5 %), and radiofrequency thermocoagulation (RFT) in 46 (32.0 %). Effectiveness did not differ among the three types of treatment (P = 0.052). The incidence of postoperative complications, including trigeminal nerve cardiac reflex, facial numbness, and mastication weakness, was lower in the craniotomy group than the PBC and RFT groups (P < 0.001). The 5-year pain recurrence rate was significantly higher than the 1-year rate in all groups. Although the 1-year pain recurrence rate did not differ among the groups, the 5-year rate was significantly lower in the repeat craniotomy group than the other groups (P < 0.001). ConclusionPatients with recurrent trigeminal neuralgia after MVD should be treated based on imaging evaluation and general condition. Repeat craniotomy, PBC, and RFT are all effective. Incidence of postoperative complications and long-term pain recurrence-free survival are superior for repeat craniotomy.

Sleep Disorders &amp; Bruxism – Trigeminal Cardiac Reflex a Missing Link!

The trigeminal cardiac reflex (TCR) is a unique and powerful brainstem reflex that has received a great deal of research interest. Sleep bruxism (SB) is sleep disorder that affects the TCR as well as other brainstem reflexes via stimulation of the brainstem; at the level of the gasserion ganglion (GG). TCR play an important role in sleep bruxism while an exaggerated form of this reflex could be responsible for sleep disorders. This paper will discuss the unusual relationship of Trigeminal cardiac reflex – bruxism – sleep disorders.

ВЛИЯНИЕ ПРОЦЕССА ЖЕВАНИЯ НА ГЕМОДИНАМИЧЕСКИЕ ПОКАЗАТЕЛИ

Chewing has been shown to have a significant effect on systemic circulation, with circulatory responses appearing to be largely regulated by autonomic nervous activity through a more complex regulatory system than responses to other activities. However, the results of studies on the relationship between masticatory movements and changes in autonomic nervous activity and systemic circulation are still rare and contradictory. We examined changes in systemic circulation during gum chewing. Blood pressure, heart rate, and chewing electromyograms were recorded during continuous gum chewing as indicators of systemic circulation in 27 healthy subjects with normal occlusion. Nonparametric matched-sample analyzes were performed to determine the chronological changes in each variable during gum chewing, and nonparametric Spearman correlations were calculated to assess the relationship between changes in hemodynamic parameters and masticatory muscle activity. Chewing gum increased heart rate and blood pressure, indicating significant changes in sympathetic activity and vagal tone. We have identified a pronounced, statistically significant strong correlation between changes in heart rate and the magnitude of contractions of the masticatory muscles. These results suggest that changes in the activity of parts of the autonomic nervous system may be due to the trigeminal nerve reflex, which explains some of the features of the autonomic nervous regulation of chewing movements.

ВЛИЯНИЕ ПРОЦЕССА ЖЕВАНИЯ НА РЕСПИРАТОРНУЮ СИНУСОВУЮ АРИТМИЮ

Respiratory sinus arrhythmia (RSA) is a clockwise fluctuation in heart rate at the frequency of the respiratory cycle. RSA is an important homeostatic mechanism, the parameters of which change under various conditions - from stress to physical exercise. However, the direct effect of chewing, the most common form of muscle activity, on RSA has not yet been studied. We studied the dynamic evolution of RSA and the associated heart rate and respiratory rate during the transition from rest to chewing gum in 37 students (15 men). The measure of RSA in this study was the spectral power of high-frequency HF oscillations. Chewing was accompanied by a slight increase in respiratory rate (RR) and a significant increase in heart rate (HR), but a statistically insignificant increase in the HR/HR ratio. Although respiration was an important determinant of RSA in this study, we observed a significant decrease in HF in the presence of relatively stable RR and HR/RR levels, indicating that the main driver of the evolution of RSA during mastication is an increase in sympathetic tone due to the trigeminal reflex.

Clinical adverse events to dexmedetomidine: a real-world drug safety study based on the FAERS database.

Adverse events associated with dexmedetomidine were analyzed using data from the FDA's FAERS database, spanning from 2004 to the third quarter of 2023. This analysis serves as a foundation for monitoring dexmedetomidine's safety in clinical applications. Data on adverse events associated with dexmedetomidine were standardized and analyzed to identify clinical adverse events closely linked to its use. This analysis employed various signal quantification analysis algorithms, including Reporting Odds Ratio (ROR), Proportional Reporting Ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN), and Multi-Item Gamma Poisson Shrinker (MGPS). In the FAERS database, dexmedetomidine was identified as the primary suspect in 1,910 adverse events. Our analysis encompassed 26 organ system levels, from which we selected 346 relevant Preferred Terms (PTs) for further examination. Notably, adverse drug reactions such as diabetes insipidus, abnormal transcranial electrical motor evoked potential monitoring, acute motor axonal neuropathy, and trigeminal cardiac reflex were identified. These reactions are not explicitly mentioned in the drug's specification, indicating the emergence of new signals for adverse drug reactions. Data mining in the FAERS database has elucidated the characteristics of dexmedetomidine-related adverse drug reactions. This analysis enhances our understanding of dexmedetomidine's drug safety, aids in the clinical management of pharmacovigilance studies, and offers valuable insights for refining drug-use protocols.

Update on Cluster Headaches: From Genetic to Novel Therapeutic Approaches

Cluster headaches affect 0.1% of the population and are four times more common in males than in females. Patients with this condition present with severe unilateral head pain localized in the frontotemporal lobe, accompanied by ipsilateral lacrimation, conjunctival injection, nasal congestion, diaphoresis, miosis, and eyelid edema. Recently, the first genome-wide association study of cluster headaches was conducted with the goal of aggregating data for meta-analyses, identifying genetic risk variants, and gaining biological insights. Although little is known about the pathophysiology of cluster headaches, the trigeminovascular and trigeminal autonomic reflexes and hypothalamic pathways are involved. Among anti-calcitonin gene-related peptide monoclonal antibodies, galcanezumab has been reported to be effective in preventing episodic cluster headaches.

Cluster headache: an update on clinical features, epidemiology, pathophysiology, diagnosis, and treatment.

Cluster headache (CH) is one of the worst primary headaches that remain underdiagnosed and inappropriately treated. There are recent advances in the understanding of this disease and available treatments. This paper aims to review CH's recent clinical and pathophysiological findings, diagnosis, and treatment. We performed a narrative literature review on the socio-demographics, clinical presentations, pathophysiological findings, and diagnosis and treatment of CH. CH affects 0.1% of the population with an incidence of 2.07-9.8/100,00 person-years-habitants, a mean prevalence of 53/100,000 inhabitants (3-150/100,000 inhabitants). The male-to-female ratio remains inconclusive, as the ratio of 4.3:1 has recently been modified to 1.3-2.6, possibly due to previous misdiagnosis in women. Episodic presentation is the most frequent (80%). It is a polygenetic and multifactorial entity that involves dysfunction of the trigeminovascular system, the trigeminal autonomic reflex, and the hypothalamic networks. An MRI of the brain is mandatory to exclude secondary etiologies. There are effective and safe pharmacological treatments oxygen, sphenopalatine, and great occipital nerve block, with the heterogeneity of clinical trial designs for patients with CH divided into acute, transitional, or bridge treatment (prednisone) and preventive interventions. In conclusion, CH remains underdiagnosed, mainly due to a lack of awareness within the medical community, frequently causing a long delay in reaching a final diagnosis. Recent advances in understanding the principal risk factors and underlying pathophysiology exist. There are new therapeutic possibilities that are effective for CH. Indeed, a better understanding of this challenging pathology will continue to be a subject of research, study, and discoveries in its diagnostic and therapeutic approach.

Short-latency prepulse inhibition of the trigeminal blink reflex.

Prepulse inhibition (PPI) is a well-established phenomenon wherein a weak sensory stimulus attenuates the startle reflex triggered by a subsequent strong stimulus. Within the circuit, variations in target responses observed for PPI paradigms represent prepulse-induced excitability changes. However, little is known about the mechanism of PPI. Here, we focused on short-latency PPI of the trigeminal blink reflex R1 signal with an oligosynaptic reflex arc through the principal sensory trigeminal nucleus and the facial nucleus. As the facial nucleus is facilitatory to any input, R1 PPI is the phenomenon in the former nucleus. Considering that GABAergic modulation may be involved in PPI, this study investigated whether the PPI mechanism includes GABA-A equivalent inhibition, which peaks at approximately 30 ms in humans. In 12 healthy volunteers, the reflex was elicited by electrical stimulation of the supraorbital nerve, and recorded at the ipsilateral lower eyelid by accelerometer. Stimulus intensity was 1.5 times the R1 threshold for test stimulus and 0.9 times for the prepulse. The prepulse-test interval (PTI) was 5-150 ms. Results showed significant inhibition at 40-and 80-150-ms PTIs but not at 20-, 30-, 50-, 60-, and 70-ms PTIs, yielding two distinct inhibitions of different time scales. This corresponds well to the early and late components of inhibitory post synaptic potentials by GABA-A and GABA-B receptor activation. Thus, the data support the contribution of inhibitory post synaptic potentials elicited by the prepulse to the observed PPI. As inhibitory function-related diseases may impair the different inhibition components to varying degrees, methods deconvoluting each inhibitory component contribution are of clinical importance.

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.

Sick sinus syndrome diagnosed after a sinus arrest during treatment for zygomatic fracture: a case report

BackgroundIntraoperative sinus arrest is rarely seen during zygomatic fracture treatment. The patient was diagnosed with sick sinus syndrome based on repeated postoperative sinus arrest, which could have resulted in death if diagnosed late, making this case very significant to report.Case presentationSick sinus syndrome is an arrhythmia associated with reduced automaticity of the sinoatrial node or impaired sinoatrial node conduction. We report the case of a 67-year-old man diagnosed with the syndrome after a sinus arrest that occurred during a zygomatic fracture treatment. The patient had cheek pain and mouth opening disorder, dizziness after fainting and sustaining a facial injury. Preoperative examination determined that the syncope was due to drug-induced arrhythmia, and surgery was authorized after drug withdrawal. During the operation, sinus arrest was observed due to trigeminal vagal reflex, and heart rate was restarted by stopping the operation and chest compressions. After the surgery, the patient showed symptoms of dizziness and palpitations, and sinus arrest following atrial fibrillation and supraventricular tachycardia, which was diagnosed as sick sinus syndrome, and a pacemaker was implanted. Currently, 8 years have passed since the surgery, and there are no symptoms of mouth opening disorder, dizziness, or palpitations.ConclusionsIn the case of maxillofacial injuries due to syncope, cardiogenic syncope is a possibility, and repeated syncope is a risk for death due to delayed diagnosis. There are no reports of maxillofacial trauma leading to a diagnosis of sick sinus syndrome. The purpose of this case report is to disseminate the importance of diagnosing the cause of syncope as well as injury treatment.

Involvement of trigeminal neuralgia in type 2 diabetes

The aim of this paper is to describe orofacial neuralgic pain related to diabetes mellitus pathology with a clinical report of a female patient who suffered from diabetic polyneuropathy. A 61-year-old female patient was treated neurologically and dentally due to suspicions of Trigeminal Neuralgia (TN) and disorders of the temporomandibular joint. Recent symptoms were burning and heat, electric shock sensation related to the right side of the face and particularly the second right premolar tooth. The patient had received regular insulin therapy (type 2 diabetes mellitus) for the last 10 years and was diagnosed with diabetic polyneuropathy with a higher value of glycosylated hemoglobin HbA1c (59 mmol/mol). The psychological evaluation showed an elevated anxiety level according to Spielberger’s State-Trait Anxiety Inventory. The most common neurogenic complication of type 2 DM is diabetic polyneuropathy. The functional status of the trigeminal reflex pathways was reflected through the blink reflex. There were a few existing reports of the relationship between diabetes mellitus and TN- related orofacial pain, which is discussed in this paper.

Oxygen inhalation has no effect on provoked cranial autonomic symptoms using kinetic oscillation stimulation in healthy volunteers.

Inhalation of oxygen is highly effective in cluster headache, a subtype of trigeminal autonomic cephalgias. Since oxygen has no effect on nociceptive pain, the mechanism of action is still unknown. The present study investigated whether oxygen inhalation modifies the trigeminal autonomic reflex arc in healthy volunteers. 21 healthy volunteers participated in a randomized, placebo controlled, double-blind, cross-over, and within-subject study design. In a randomized order demand valve inhalation of 100% oxygen or medical air were administered. Capillary blood samples were collected to control for blood gas changes. Cranial parasympathetic output (lacrimation) was provoked using kinetic oscillation stimulation of the nasal mucosa. Standardized measurement of lacrimation between baseline and kinetic oscillation stimulation served as a measure of induced cranial autonomic output. There was no significant difference in parasympathetic output after oxygen inhalation when compared to inhalation of medical air. The inhalation of 100% oxygen does not affect the parasympathetic reflex arc of the trigeminal autonomic reflex.

Cranial Autonomic Symptoms and Neck Pain in Differential Diagnosis of Migraine

Cranial autonomic symptoms and neck pain have been reported to be highly prevalent in migraine, although they are rarely considered in clinical evaluation. The aim of this review is to focus on the prevalence, pathophysiology, and clinical characteristics of these two symptoms, and their importance in the differential diagnosis between migraines and other headaches. The most common cranial autonomic symptoms are aural fullness, lacrimation, facial/forehead sweating, and conjunctival injection. Migraineurs experiencing cranial autonomic symptoms are more likely to have more severe, frequent, and longer attacks, as well as higher rates of photophobia, phonophobia, osmophobia, and allodynia. Cranial autonomic symptoms occur due to the activation of the trigeminal autonomic reflex, and the differential diagnosis with cluster headaches can be challenging. Neck pain can be part of the migraine prodromal symptoms or act as a trigger for a migraine attack. The prevalence of neck pain correlates with headache frequency and is associated with treatment resistance and greater disability. The convergence between upper cervical and trigeminal nociception via the trigeminal nucleus caudalis is the likely mechanism for neck pain in migraine. The recognition of cranial autonomic symptoms and neck pain as potential migraine features is important because they often contribute to the misdiagnosis of cervicogenic problems, tension-type headache, cluster headache, and rhinosinusitis in migraine patients, delaying appropriate attack and disease management.

Machine learning for exploring neurophysiological functionality in multiple sclerosis based on trigeminal and hand blink reflexes

Brainstem dysfunctions are very common in Multiple Sclerosis (MS) and are a critical predictive factor for future disability. Brainstem functionality can be explored with blink reflexes, subcortical responses consisting in a blink following a peripheral stimulation. Some reflexes are already employed in clinical practice, such as Trigeminal Blink Reflex (TBR). Here we propose for the first time in MS the exploration of Hand Blink Reflex (HBR), which size is modulated by the proximity of the stimulated hand to the face, reflecting the extension of the peripersonal space. The aim of this work is to test whether Machine Learning (ML) techniques could be used in combination with neurophysiological measurements such as TBR and HBR to improve their clinical information and potentially favour the early detection of brainstem dysfunctionality. HBR and TBR were recorded from a group of People with MS (PwMS) with Relapsing-Remitting form and from a healthy control group. Two AdaBoost classifiers were trained with TBR and HBR features each, for a binary classification task between PwMS and Controls. Both classifiers were able to identify PwMS with an accuracy comparable and even higher than clinicians. Our results indicate that ML techniques could represent a tool for clinicians for investigating brainstem functionality in MS. Also, HBR could be promising when applied in clinical practice, providing additional information about the integrity of brainstem circuits potentially favouring early diagnosis.

Target Site of Prepulse Inhibition of the Trigeminal Blink Reflex in Humans.

Despite the clinical significance of prepulse inhibition (PPI), the mechanisms are not well understood. Herein, we present our investigation of PPI in the R1 component of electrically induced blink reflexes. The effect of a prepulse was explored with varying prepulse test intervals (PTIs) of 20-600 ms in 4 females and 12 males. Prepulse-test combinations included the following: stimulation of the supraorbital nerve (SON)-SON [Experiment (Exp) 1], sound-sound (Exp 2), the axon of the facial nerve-SON (Exp 3), sound-SON (Exp 4), and SON-SON with a long trial-trial interval (Exp 5). Results showed that (1) leading weak SON stimulation reduced SON-induced ipsilateral R1 with a maximum effect at a PTI of 140 ms, (2) the sound-sound paradigm resulted in a U-shaped inhibition time course of the auditory startle reflex (ASR) peaking at 140 ms PTI, (3) facial nerve stimulation showed only a weak effect on R1, (4) a weak sound prepulse facilitated R1 but strongly inhibited SON-induced late blink reflexes (LateRs) with a similar U-shaped curve, and (5) LateR in Exp 5 was almost completely absent at PTIs >80 ms. These results indicate that the principal sensory nucleus is responsible for R1 PPI. Inhibition of ASR or LateR occurs at a point in the startle reflex circuit where auditory and somatosensory signals converge. Although the two inhibitions are different in location, their similar time courses suggest similar neural mechanisms. As R1 has a simple circuit and is stable, R1 PPI helps to clarify PPI mechanisms.SIGNIFICANCE STATEMENT Prepulse inhibition (PPI) is a phenomenon in which the startle response induced by a startle stimulus is suppressed by a preceding nonstartle stimulus. This study demonstrated that the R1 component of the trigeminal blink reflex shows clear PPI despite R1 generation within a circuit consisting of the trigeminal and facial nuclei, without startle reflex circuit involvement. Thus, PPI is not specific to the startle reflex. In addition, PPI of R1, the auditory startle reflex, and the trigeminal late blink reflex showed similar time courses in response to the prepulse test interval, suggesting similar mechanisms regardless of inhibition site. R1 PPI, in conjunction with other paradigms with different prepulse-test combinations, would increase understanding of the underlying mechanisms.

Conscious agency vs. pre-conscious sensory filtering: Disparate suppression of trigeminal blink reflex by self-stimulation and by prepulses.

Modulation of the blink reflex (BR) to supraorbital nerve (SON) stimulation by a weak somatosensory prepulse (sPP) consists of inhibition of R2 and facilitation of R1. Similar BR changes occur with self-stimulation. Our aim was to compare neurophysiological processes underlying both effects. We assessed BR parameters in 18 healthy participants following right SON stimulation either performed by an experimenter (experiment 1A) or following self-stimulation (experiments 1B, 1C). In experiments 1A and 1C, sPPs to digit 2 preceded SON stimuli by 40, 100, 200 and 500 ms. In experiment 1B: self-stimulation was delayed by 40, 100, 200, and 500 ms. In experiment 2, BRs were elicited by an experimenter randomly during a 2-s period before participants applied self-stimulation. In experiment 1, as expected, sPPs caused facilitation of R1 and inhibition of R2, which peaked at 100 ms ISI, similarly in experiments 1A and 1C. Self-stimulation caused a decrease of R2, which was evident in a broad range of time intervals. In experiment 2, R2 was already inhibited at the onset of the 2-s period, while R1 began to rise significantly 1.4s before self-stimulation. Both effects progressively increased until self-triggering. The results concur with a time-locked gating mechanism of prepulses at brainstem level, whereas self-stimulation modulates BR in a tonic manner, reflecting a cognitive influence due to self-agency.

CLUSTER HEADACHE

Cluster headache (CH) is a trigeminal autonomic cephalgia characterized by attacks of severe unilateral headache accompanied by ipsilateral autonomic symptoms. The prevalence of cluster headache in the overall population is 1 in every 1000 people. The exact etiology of cluster headache remains unclear. However, it is thought that there is a connection between the trigeminovascular system, parasympathetic nerve fibers involved in trigeminal autonomic reflexes, and the hypothalamus. Treatment of CH has three stages, namely: abortive, transitional, and preventive. Cluster headaches tend to subside with age with less frequent attacks and longer periods of remission between attacks.

Unravelling the role of unmyelinated nerve fibres in trigeminal neuralgia with concomitant continuous pain

ObjectiveIn this clinical and neurophysiological study, we aimed to test trigeminal nerve fibre function in patients with trigeminal neuralgia, with and without concomitant continuous pain. MethodsWe enrolled 65 patients with a definite diagnosis of primary trigeminal neuralgia. Patients were grouped according to whether they experienced purely paroxysmal pain (36) or also had concomitant continuous pain (29). All participants underwent trigeminal reflex testing to assess the function of large non-nociceptive myelinated fibres and laser-evoked potentials to assess the function of small myelinated Aδ and unmyelinated C fibres. Neurophysiological examiners were blinded to the affected side. ResultsThe only neurophysiological abnormality distinguishing the two groups of patients was the side asymmetry of C fibre-related laser-evoked potential amplitude (p = 0.005), which was higher in patients with concomitant continuous pain than in patients with purely paroxysmal pain (indicative of a reduced C fibre-related laser-evoked potential amplitude in the affected side of patients with concomitant continuous pain). ConclusionsOur clinical and neurophysiological study indicates that in patients with trigeminal neuralgia concomitant continuous pain is associated with unmyelinated C fibre damage as assessed with laser-evoked potentials. SignificanceOur findings suggest that concomitant continuous pain is related to unmyelinated C fibre loss, possibly triggering abnormal activity in denervated trigeminal second-order neurons.