Recovery of nerve conduction following microvascular decompression for trigeminal neuralgia

Outcomes of Trigeminal Ganglion Sparing Surgical Resection of Nonacoustic Cerebellopontine Angle Tumors Causing Trigeminal Neuralgia

OBJECTIVE

Tumors may be responsible for up to 5% of trigeminal neuralgia cases. Predictors of long-term pain relief after surgical resection of various cerebellopontine angle tumor types are not well understood. Previous studies found that size and extent of resection predict long-term pain status, although resection of tumor involving the trigeminal ganglion may be associated with high morbidity. This study evaluated predictors of TN pain freedom after resection of a nonacoustic CPA tumor, with avoidance of any portion involving the TG.

METHODS

In a retrospective cohort study, we evaluated clinical outcomes and complications after surgical resection of nonacoustic CPA tumors with purposeful avoidance of the TG causing trigeminal neuralgia. The primary outcome was pain-freedom. We performed logistic regression analyses to examine the relationship between pain-freedom at last follow-up and age, side of symptoms, preoperative symptom duration, tumor diameter, tumor type, and concurrent neurovascular compression (NVC).

RESULTS

Of 18 patients with nonacoustic CPA tumors causing TN treated with surgical resection, 83.3% were pain-free at last follow-up (mean 44.6 months). Age (P = 0.12), side (P = 0.41), preoperative symptom duration (P = 0.85), tumor diameter (P = 0.29), tumor type (P = 0.37), and NVC presence (P = 0.075) were not associated with long-term pain freedom.

CONCLUSIONS

This study provides additional evidence that various tumor types causing TN may safely undergo surgical resection and decompression of the trigeminal nerve to treat TN. This study presents a cohort of patients that underwent resection of a nonacoustic CPA tumor, with purposeful avoidance of the TG to minimize complications, demonstrating high rates of long-term pain freedom.

Trigeminal neuralgia

Trigeminal neuralgia (TN) is a facial pain disorder characterized by intense and paroxysmal pain that profoundly affects quality of life and presents complex challenges in diagnosis and treatment. TN can be categorized as classical, secondary and idiopathic. Epidemiological studies show variable incidence rates and an increased prevalence in women and in the elderly, with familial cases suggesting genetic factors. The pathophysiology of TN is multifactorial and involves genetic predisposition, anatomical changes, and neurophysiological factors, leading to hyperexcitable neuronal states, central sensitization and widespread neural plasticity changes. Neurovascular compression of the trigeminal root, which undergoes major morphological changes, and focal demyelination of primary trigeminal afferents are key aetiological factors in TN. Structural and functional brain imaging studies in patients with TN demonstrated abnormalities in brain regions responsible for pain modulation and emotional processing of pain. Treatment of TN involves a multifaceted approach that considers patient-specific factors, including the type of TN, with initial pharmacotherapy followed by surgical options if necessary. First-line pharmacological treatments include carbamazepine and oxcarbazepine. Surgical interventions, including microvascular decompression and percutaneous neuroablative procedures, can be considered at an early stage if pharmacotherapy is not sufficient for pain control or has intolerable adverse effects or contraindications.

Preclinical orofacial pain assays and measures and chronic primary orofacial pain research: where we are and where we need to go

Chronic primary orofacial pain (OFP) conditions such as painful temporomandibular disorders (pTMDs; i.e., myofascial pain and arthralgia), idiopathic trigeminal neuralgia (TN), and burning mouth syndrome (BMS) are seemingly idiopathic, but evidence support complex and multifactorial etiology and pathophysiology. Important fragments of this complex array of factors have been identified over the years largely with the help of preclinical studies. However, findings have yet to translate into better pain care for chronic OFP patients. The need to develop preclinical assays that better simulate the etiology, pathophysiology, and clinical symptoms of OFP patients and to assess OFP measures consistent with their clinical symptoms is a challenge that needs to be overcome to support this translation process. In this review, we describe rodent assays and OFP pain measures that can be used in support of chronic primary OFP research, in specific pTMDs, TN, and BMS. We discuss their suitability and limitations considering the current knowledge of the etiology and pathophysiology of these conditions and suggest possible future directions. Our goal is to foster the development of innovative animal models with greater translatability and potential to lead to better care for patients living with chronic primary OFP.

Advances in diagnosis, classification, pathophysiology, and management of trigeminal neuralgia

Trigeminal neuralgia is a very painful neurological condition with severe, stimulus-evoked, short-lasting stabbing pain attacks in the face. The past decade has offered new insights into trigeminal neuralgia symptomatology, pathophysiology, and treatment, leading to a change in the classification of the condition. An accurate diagnosis is crucial because neuroimaging interpretation and clinical management differ among the various forms of facial pain. MRI using specific sequences should be a part of the diagnostic workup to detect a possible neurovascular contact and exclude secondary causes. Demonstration of a neurovascular contact should not be used to confirm a diagnosis but rather to facilitate surgical decision making. Carbamazepine and oxcarbazepine are drugs of first choice for long-term treatment, whereas microvascular decompression is the first-line surgery in medically refractory patients. Advances in neuroimaging techniques and animal models will provide further insight into the causes of trigeminal neuralgia and its pathophysiology. Development of more efficacious treatment options is highly warranted.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Trigeminal neuralgia secondary to multiple sclerosis: from the clinical picture to the treatment options

BACKGROUND

Trigeminal neuralgia is one of the most characteristic and difficult to treat neuropathic pain conditions in patients with multiple sclerosis. The present narrative review addresses the current evidence on diagnostic tests and treatment of trigeminal neuralgia secondary to multiple sclerosis.

METHODS

We searched for relevant papers within PubMed, EMBASE and the Cochrane Database of Systematic Reviews, taking into account publications up to December 2018.

RESULTS

Trigeminal neuralgia secondary to multiple sclerosis manifests with facial paroxysmal pain triggered by typical manoeuvres; neurophysiological investigations and MRI support the diagnosis, providing the definite evidence of trigeminal pathway damage. A dedicated MRI is required to identify pontine demyelinating plaques. In many patients with multiple sclerosis, neuroimaging and surgical evidence suggests that neurovascular compression might act in concert with the pontine plaque through a double-crush mechanism. Although no placebo-controlled trials have been conducted in these patients, according to expert opinion the first-line therapy for trigeminal neuralgia secondary to multiple sclerosis relies on sodium-channel blockers, i.e. carbamazepine and oxcarbazepine. The sedative and motor side effects of these drugs frequently warrant an early consideration for neurosurgery. Surgical procedures include Gasserian ganglion percutaneous techniques, gamma knife radiosurgery and microvascular decompression in the posterior fossa.

CONCLUSIONS

The relatively poor tolerability of the centrally-acting drugs carbamazepine and oxcarbazepine highlights the need to develop new selective and better-tolerated sodium-channel blockers. Prospective studies based on more advanced neuroimaging techniques should focus on how trigeminal anatomical abnormalities may be able to predict the efficacy of microvascular decompression.

Prognostic factors for outcome of microvascular decompression in trigeminal neuralgia: A prospective systematic study using independent assessors

Introduction

There is a lack of high-quality prospective, systematic studies using independent assessors of outcome of microvascular decompression as treatment for trigeminal neuralgia.

Methods

Clinical characteristics and outcome data were recorded prospectively from consecutive classical trigeminal neuralgia patients, using standardized interviews. Degree of neurovascular contact was evaluated by a 3.0 Tesla MRI blinded to symptomatic side. Patients were assessed before and 12 months after surgery by a neurologist.

Results

Twenty-six men and 33 women completed 12 months follow-up. Forty-one patients (69%) had an excellent outcome (no pain, no medication). Ten (18%) patients had a good outcome. Eight (12%) patients had no improvement or had worsening of pain. MRI showed neurovascular contact with morphological changes in 34 patients (58%). Odds ratio between neurovascular contact with morphological changes and excellent outcome was 4.4 (Cl 1.16–16.26), p = 0.029. Odds ratio between male sex and excellent outcome was 11.38 (Cl 2.12–59.52), p = 0.004. No significant association was found between excellent outcome and concomitant persistent pain, current age or disease duration.

Conclusion

Neurovascular contact with morphological changes and male sex are positive predictive factors for outcome of microvascular decompression. The findings enable clinicians to better inform patients before surgery.

Absence of neurovascular conflict during microvascular decompression while treating essential trigeminal neuralgia. How to proceed? Systematic review of literature

INTRODUCTION

Neurovascular conflict is the most accepted hypothesis for the cause for trigeminal neuralgia. Microvascular decompression of the trigeminal nerve is the most common surgical treatment for these patients. However, despite advances in diagnostic techniques, neurovascular conflict is sometimes not detected during surgery. The aim of this paper is to systematically review all the options available to best manage this scenario.

RESULTS

Several techniques that could be used during microvascular decompression for trigeminal neuralgia in the absence of neurovascular conflict have been described. The success rates of these techniques, pain recurrence rates and rates of complications are also reported. Finally, we provide suggestions based on our experience.

CONCLUSIONS

There is no gold standard, but several techniques could be successfully used in the absence of neurovascular conflict. The use of destructive techniques, such as PSR, should be held as treatments of last resort.

A technique to assess perineuronal mediators

Perineural activity of a variety of inflammatory and immune system mediators can activate peripheral nerves leading to the perception of pain. One example of such effects includes the activity of interleukin 1 beta (IL-1β); this inflammatory mediator, upon binding to IL-1R1 neuronal membrane receptors will rapidly induce protein kinases in damage-sensing neurons, consequently altering heat-activated ionic inward currents leading to increased neuronal sensitivity to harmful heat. The ability to detect such mediators in proximity to sensory nerves is therefore crucial to investigating the contributing roles of inflammation in human chronic pain. To date there is no recognized method to assess mediator profiles around human sensory nerve roots in vivo. A novel method is described that can assess these mediators in the human trigeminal system where the nerve leaves the brain stem in its pre-ganglionic portion. Mediator levels are shown to change between sample locations on the trigeminal nerve root in patients with trigeminal neuralgia. This methodology may therefore be used to shed insights as to the pathophysiology of trigeminal neuralgia, which may in turn influence clinical decisions concerning the natural history, and treatment options.

Neurovascular Compression at the Root Entry Zone Correlates with Trigeminal Neuralgia and Early Microvascular Decompression Outcome

BACKGROUND

Trigeminal neurovascular contact (NVC) is hypothesized to be the etiology of classical trigeminal neuralgia (TGN). We aimed to seek a correlation between types of NVCs and the presence of TGN as well as early surgical outcome in patients with TGN treated with trigeminal microvascular decompression (MVD).

METHODS

We blindly analyzed preoperative high-resolution magnetic resonance images with respect to the degree (none, "touch," or compression) and location of bilateral NVC in 57 retrospectively identified Burchiel Type 1 TGN patients treated by MVD. Location of NVC was noted as either at the root entry zone or distal to it. Using a logistic regression model, we assessed the degree and location of trigeminal NVC for correlation with the symptomatic side. Furthermore, the NVC characteristics on the symptomatic side were correlated with early postoperative pain relief.

RESULTS

Although the degree and location of NVC were not statistically correlative independently, a combined interaction analysis of both statistically correlated with the symptomatic side and with early postoperative pain relief.

CONCLUSIONS

We conclude that in TGN patients treated with MVD, magnetic resonance imaging identified neurovascular compression at the root entry zone (correlates with the affected side and early postoperative pain relief.

Hemibody pain relieved by microvascular decompression of the contralateral caudal medulla: case report

Microvascular decompression (MVD) of cranial nerves has become an established treatment for trigeminal and (vago)glossopharyngeal neuralgia and for hemifacial spasm. The authors present the case of a 64-year-old man who had a 3.5-year history of severe, drug-resistant hemibody pain with sensory and autonomic disturbance. The ipsilateral trigeminal, cochlear, and glossopharyngeal function also was affected. The contralateral posterior inferior cerebellar artery was seen on magnetic resonance imaging to be indenting the caudal medulla anterolaterally, causing displacement. After MVD of the medulla, there was an immediate and complete resolution of the pain and almost complete resolution of the sensory and autonomic disturbances. The pain later recurred mildly and transiently. The residual symptoms had resolved by 2 years.

Tongue somatosensory-evoked potentials in microvascular decompression treated trigeminal neuralgia

Somatosensory-evoked potentials of the tongue (tSSEP) provide useful information about trigeminal-afferent pathway. The aim of this study was to evaluate tSSEP in trigeminal neuralgia (TN) treatment with microvascular decompression. Two patients with trigeminal neuralgia refractory to conservative treatment underwent microvascular decompression of the trigeminal nerve. tSSEP was performed a month prior to surgery and in the month after the surgery in both patients. Pain frequency and tSSEP were analyzed before and after surgery. In both patients, a complete resolution of pain occurred. In patient 1, tSSEP latencies became shorter than before surgery and wave N1 appeared. The intensity of stimulation necessary to reach the threshold was 4 mA before the surgery and 1 mA after the surgery. A complete recovery of tSSEP after the operation was achieved in patient 2. The results of present study demonstrate potential value of tSSEP in pre-surgery evaluation and post-surgery follow-up of TN patients.

The trigemino-cervical reflex in patients with trigeminal neuralgia

OBJECTIVES

To investigate the central trigeminal system in idiopathic trigeminal neuralgia (TN).

MATERIALS AND METHODS

Short latency responses can be recorded in sternocleidomastoid (SCM) muscles after stimulation of the trigeminal nerve (trigemino-cervical reflex). This brainstem reflex was investigated in 40 healthy subjects and in 17 patients suffering from idiopathic TN before and after therapy for 2 months with carbamazepin.

RESULTS

Before therapy, six patients presented abnormalities of SCM responses on the painful side, six patients with bilateral abnormalities, and five patients with normal responses. A significant variation in the responses after therapy was found only in the patients with unilateral abnormalities: these patients and the patients with normal reflexes before therapy also had a good response to the therapy with significant pain relief.

CONCLUSIONS

Our findings suggest that the trigemino-cervical reflex could be useful in the clinical assessment of TN prior to instituting non-surgical treatment. The bilateral location of the abnormalities in some patients seems to point to a centrally located dysfunction; therefore, this study supports the idea that mechanisms in the central nervous system may play an important role in the pathophysiology of trigeminal neuralgic pain.

Trigeminal neuralgia secondary to posterior fossa tumor

Trigeminal neuralgia (TN) is by no means an uncommon entity presenting as typical or atypical pain syndrome with a standard treatment protocol consisting of medical and surgical therapies. The diagnosis of TN is mainly dependent on the characteristics of symptoms conveyed by the patient and the clinical presentation. Careful history taking, proper interpretation of the signs and symptoms and cranial nerve assessment are necessary for proper diagnosis. Here, we report a case of TN, treated for dental problems and then for neuralgia with only short-term relief. Subsequently, the patient underwent neuroimaging and was found to be having an uncommon space-occupying lesion in the posterior cranial fossa.

A rodent model of trigeminal neuralgia

Trigeminal Neuralgia (Tic Douloureux) is a neuropathic pain syndrome caused by compression of the trigeminal nerve root and is characterized by severe paroxysms of pain in the face commonly triggered by light mechanical stimulation to the peri-oral area. Trigeminal neuralgia is very difficult to treat in part due to the lack of an suitable animal model for testing novel therapeutic approaches. This chapter describes a model of trigeminal neuralgia in which crystals of a superabsorbent polymer are placed next to the trigeminal nerve root of rats, producing ongoing mechanical compression of the nerve root. The chapter then describes means of behaviorally assessing the robust mechanical hypersensitivity consequent to the compression that can be used to determine the efficacy of potential therapies for this devastating condition.

Different pain, different brain: thalamic anatomy in neuropathic and non-neuropathic chronic pain syndromes

Trigeminal neuropathic pain (TNP) and temporomandibular disorders (TMD) are thought to have fundamentally different etiologies. It has been proposed that TNP arises through damage to, or pressure on, somatosensory afferents in the trigeminal nerve, whereas TMD results primarily from peripheral nociceptor activation. Because some reports suggest that neuropathic pain is associated with changes in brain anatomy, it is possible that TNP is maintained by changes in higher brain structures, whereas TMD is not. The aim of this investigation is to determine whether changes in regional brain anatomy and biochemistry occur in both conditions. Twenty-one TNP subjects, 20 TMD subjects, and 36 healthy controls were recruited. Voxel-based morphometry of T1-weighted anatomical images revealed no significant regional gray matter volume change in TMD patients. In contrast, gray matter volume of TNP patients was reduced in the primary somatosensory cortex, anterior insula, putamen, nucleus accumbens, and the thalamus, whereas gray matter volume was increased in the posterior insula. The thalamic volume decrease was only seen in the TNP patients classified as having trigeminal neuropathy but not those with trigeminal neuralgia. Furthermore, in trigeminal neuropathy patients, magnetic resonance spectroscopy revealed a significant reduction in the N-acetylaspartate/creatine ratio, a biochemical marker of neural viability, in the region of thalamic volume loss. The data suggest that the pathogenesis underlying neuropathic and non-neuropathic pain conditions are fundamentally different and that neuropathic pain conditions that result from peripheral injuries may be generated and/or maintained by structural changes in regions such as the thalamus.

Classification of trigeminal neuralgia: clinical, therapeutic, and prognostic implications in a series of 144 patients undergoing microvascular decompression

OBJECT

Trigeminal neuralgia (TN) presents a diagnostic challenge because of the variety of symptoms, findings during microvascular decompression (MVD), and postsurgical outcomes observed among patients who suffer from this disorder. Recently, a new paradigm for classification of TN was proposed, based on the quality of pain. This study represents the first clinical analysis of this paradigm.

METHODS

The authors analyzed 144 consecutive cases involving patients who underwent MVD for TN. Preoperative symptoms were classified into 1 of 2 categories based on the preponderance of shocklike (Type 1 TN) or constant (Type 2 TN) pain. Analysis of clinical characteristics, neurovascular pathology, and postoperative outcome was performed.

RESULTS

Compared with Type 2 TN, Type 1 TN patients were older, were more likely to have right-sided symptoms, and reported a shorter duration of symptoms prior to evaluation. Previous treatment by percutaneous or radiosurgical procedures was not a predictor of symptoms, surgical findings, or outcome (p = 0.48). Type 1 TN was significantly more likely to be associated with arterial compression. Venous or no compression was more common among Type 2 TN patients (p < 0.01). Type 1 TN patients were also more likely to be pain-free immediately after surgery, and less likely to have a recurrence of pain within 2 years (p < 0.05). Although a subset of patients progressed from Type 1 to Type 2 TN over time, their pathological and prognostic profiles nevertheless resembled those of Type 1 TN.

CONCLUSIONS

Type 1 and Type 2 TN represent distinct clinical, pathological, and prognostic entities. Classification of patients according to this paradigm should be helpful to determine how best to treat patients with this disorder.

Predictors of long-term success after microvascular decompression for trigeminal neuralgia

OBJECT

Microvascular decompression (MVD) is an effective treatment for trigeminal neuralgia (TN). However, many patients do not experience complete pain relief, and relapse can occur even after an initial excellent result. This study was designed to identify characteristics associated with improved long-term outcome after MVD.

METHODS

One hundred seventy-nine consecutive patients who had undergone MVD for TN at the authors' institution were contacted, and 95 were enrolled in the study. Patients provided information about preoperative pain characteristics including preponderance of shock-like (Type 1 TN) or constant (Type 2 TN) pain, preoperative duration, trigger points, anticonvulsant therapy response, memorable onset, and pain-free intervals. Three groups were defined based on outcome: 1) excellent, pain relief without medication; 2) good, mild or intermittent pain controlled with low-dose medication; and 3) poor, severe persistent pain or need for additional surgical treatment. Results Type of TN pain (Type 1 TN vs Type 2 TN) was the only significant predictor of outcome after MVD.

RESULTS

were excellent, good, and poor for Type 1 TN versus Type 2 TN patients in 60 versus 25%, 24 versus 39%, and 16 versus 36%, respectively. Among patients with each TN type, there was a significant trend toward better outcome with greater proportional contribution of Type 1 TN (lancinating) symptoms (p < 0.05).

CONCLUSIONS

Pain relief after MVD is strongly correlated with the lancinating pain component, and therefore type of TN pain is the best predictor of long-term outcome after MVD. Application of this information should be helpful in the selection of TN patients likely to benefit from MVD.

Microvascular decompression for trigeminal neuralgia: the importance of a noncompressive technique--Kaplan-Meier analysis in a consecutive series of 330 patients

OBJECTIVE

Microvascular decompression, although a well-established procedure for treating primary trigeminal neuralgia, still has no standardized protocol. The practical consequences of having the implant keep the conflicting vessels apart, whether or not in contact with the root, is still in debate. The present work was undertaken to answer this question.

METHODS

Patients were segregated into 2 groups: Group I (260 patients) had a Teflon prosthesis implanted without contact to the root, and Group II (70 patients) had a similar implant with contact to the root. Cure rates in the 2 groups were compared at the latest follow-up (</=15 yr; average, 8.2 yr) using Kaplan-Meier analysis.

RESULTS

In Group I, the cure rate was 82% (214 of 260 patients), whereas in Group II, the cure rate was 67% (47 of 70 patients) (P = 0.01). Kaplan-Meier analysis of the follow-up period up to 15 years also shows a significant difference (P = 0.05).

CONCLUSION

These results strongly support the goal of performing the procedure without the implant in contact with the root. This is easier with the superior cerebellar artery, because of its laxity and small number of perforating branches, than with the anteroinferior cerebellar artery, which has perforators to the brainstem and labyrinthine artery arising from its cisternal portion. The significantly better long-term cure rate when the implant is not in contact with the root favors the "pure" decompressive effect of the microvascular decompression procedure, rather than a conduction block mechanism.

Trigeminal neuralgia in a patient with multiple sclerosis and chronic inflammatory demyelinating polyneuropathy

BACKGROUND

Trigeminal neuralgia (TN) is characterized by unilateral, severe, brief, stabbing, recurrent pain in the distribution of one or more branches of the fifth cranial nerve. Symptomatic or secondary TN involves TN-like pain that develops owing to a central nervous system lesion (benign or malignant) or to multiple sclerosis (MS).

CASE DESCRIPTION

The authors present a report of a unique case of a 43-year-old patient with unilateral TN, MS and concomitant chronic inflammatory demyelinating polyneuropathy. The facial pain preceded any other manifestations of the systemic disorders, and only after repeated neurological examinations were these diagnoses established.

CLINICAL IMPLICATIONS

Magnetic resonance imaging of the brain and repeated neurological evaluations should be implemented in all patients with TN to rule out the presence of underlying disease. The dental practitioner should be familiar with TN to avoid unnecessary dental interventions and ensure prompt initiation of appropriate treatment.

Trigeminal neuralgia: definition and classification

Based on specific, objective, and reproducible criteria, a classification scheme for trigeminal neuralgia (TN) and related facial pain syndromes is proposed. Such a classification scheme is based on information provided in the patient's history and incorporates seven diagnostic criteria, as follows. 1) and 2) Trigeminal neuralgia Types 1 and 2 (TN1 and TN2) refer to idiopathic, spontaneous facial pain that is either predominantly episodic (as in TN1) or constant (as in TN2) in nature. 3) Trigeminal neuropathic pain results from unintentional injury to the trigeminal nerve from trauma or surgery. 4) Trigeminal deafferentation pain results from intentional injury to the nerve by peripheral nerve ablation, gangliolysis, or rhizotomy in an attempt to treat either TN or other related facial pain. 5) Symptomatic TN results from multiple sclerosis. 6) Postherpetic TN follows a cutaneous herpes zoster outbreak in the trigeminal distribution. 7) The category of atypical facial pain is reserved for facial pain secondary to a somatoform pain disorder and requires psychological testing for diagnostic confirmation. The purpose of a classification scheme like this is to advocate a more rigorous, standardized natural history and outcome studies for TN and related facial pain syndromes.

Trigeminal neuralgia and glossopharyngeal neuralgia

Trigeminal neuralgia and glossopharyngeal neuralgia are extremely painful conditions that typically afflict an older population. Distinct clinical characteristics guide the diagnosis of these unique syndromes. Treatment involves medication first and then surgical procedures if a patient is refractory to medicinal therapy. Antiepileptic medications are the most effective agents for these disorders.

Impairment of trigeminal sensory pathways in cluster headache

Cluster headache (CH) typically presents in clusters of attacks of intense (peri)orbital, unilateral pain. The distribution of the pain implies involvement of central and/or peripheral trigeminal pathways. These can be investigated by means of trigeminal somatosensory evoked potentials (TSEP) and blink reflexes (BR). We aimed to relate functional changes in trigeminal sensory pathways to the presence of cluster periods. TSEP and BR were performed in 28 episodic CH patients during a cluster period and repeated in 22 outside a cluster period. TSEP latencies (N1, P1 and N2) and amplitude (N1-P1 and P1-N2) and BR latencies (R1, R2 ipsilateral and R2 contralateral) were compared between sides, during and outside a cluster period and with healthy control data (n = 22). During a cluster period, N2 TSEP latencies were longer on the symptomatic side compared with the non-symptomatic side (27.2 +/- 3.0 ms vs. 26.3 +/- 3.4 ms, P = 0.02), and compared with the same side outside the cluster period (26.7 +/- 3.1 ms vs. 25.1 +/- 3.0 ms, P = 0.01). N1, P1 and N2 latencies on the symptomatic side in patients during the cluster period (14.8 +/- 2.3 ms, 20.4 +/- 2.5 ms and 27.2 +/- 3.0 ms, respectively) were significantly longer than those of healthy controls (13.4 +/- 1.9 ms, 18.8 +/- 2.4 ms and 25.0 +/- 2.6 ms, respectively, P < 0.03). Outside the cluster period, N1 latencies of both sides (15.3 +/- 2.8 ms symptomatic side and 15.4 +/- 2.6 ms asymptomatic side) were longer compared with controls (13.4 +/- 1.9 ms, P < 0.04). TSEP amplitudes and BR latencies revealed no significant differences. We conclude that abnormalities of the afferent trigeminal pathway are present in patients with cluster headache, most prominent during the cluster period, and on the symptomatic side. This seems primarily due of changes within the higher cerebral regions of the system.

Reproducibility and feasibility of neurophysiological assessment of the sensory trigeminal system for future application to paroxysmal headaches

As the distribution of pain in primary headaches suggests involvement of the trigeminal sensory pathways, trigeminal somatosensory evoked potentials (TSEP) and blink reflexes (BR) may provide important information about their functional integrity. Functional differences between symptomatic and non-symptomatic sides and between measurements during and outside attacks may be particularly informative. These tests should therefore be reproducible and should require a suitable number of patients for future studies in patients with primary, paroxysmal headaches. We performed TSEP and BR twice in 22 healthy volunteers, in order to calculate sample sizes based on reproducibility data. This is, to our knowledge, the first study investigating the reproducibility of TSEP and BR measurements. Latencies of TSEP and BR are appropriate for future studies, as their reproducibility allows practical sample sizes (less than 25 subjects). Duration, amplitude and area parameters of the BR responses were less appropriate for longitudinal studies.

Operative findings in cases of trigeminal neuralgia without vascular compression: proposal of a different mechanism

Trigeminal neuralgia is known to be caused by vascular compression at the trigeminal root entry zone (REZ) and microvascular decompression provides good outcome in most of cases. However, in some cases, no vascular compression was observed at the REZ. Over the last 2(1/2) years, the first author operated on 53 cases of trigeminal neuralgia with microvascular decompression and encountered nine cases where no offending vessels were noted at or near the REZ. They were divided into two groups: five cases involving an initial operation and four cases involving a second operation. In the former, arachnoid thickening, angulation or torsion of the root axis were common findings. Dissection of thick arachnoid around the root along the whole length reversed the root to be straight and flaccid. Complete pain relief was noted in four of five cases. In one case of atypical pain, constant facial pain remained. In the latter four cases, where the first operations were done more than 4 years before, thick granulation was noted around REZ without new offending vessels in two cases. In the remaining two cases, where no offending vessels were noted in the first operation, thick adhesion of a distal portion of the root with dura on the pyramidal bone was noted. Meticulous dissection of t he whole length of the root was done and complete pain relief was obtained. Delayed but complete pain relief in these nine cases was noted. Based on operative findings, arachnoid thickening or granulomatous adhesion between the root and surrounding structures can cause an abnormal course of the trigeminal nerve root, which causes root angulation and/or torsion. They can also cause pulsatile movement of the trigeminal nerve root. This tethering effect can promote abnormal root stretching force, especially at REZ, which might promote hyperexitability of the nerve. This speculative mechanism suggests that it is important to make the root free along the entire length, especially at its distal portion in cases with no offending vessels.

Neurosurgery and facial pain

This article reviews the diagnosis, differential diagnosis and management of trigeminal neuralgia, the commonest facial pain condition treated by the neurosurgeon. The advantages offered by microvascular decompression as a treatment are reviewed and compared with medical treatment and percutaneous techniques.

Headshaking in horses: possible aetiopathogenesis suggested by the results of diagnostic tests and several treatment regimes used in 20 cases

Twenty mature horses with typical headshaking of 2 week-7 year duration were studied. Clinical examinations included radiography of the head and nasopharyngeal endoscopy. All were assessed at rest and at exercise, both before and after fitting an occlusive nasal mask, application of tinted contact lenses and the perineural anaesthesia of the infraorbital and posterior ethmoidal branches of the trigeminal nerve. Infraorbital anaesthesia had no effect in 6/7 cases but 11/17 (65%) cases showed a 90-100% improvement following posterior ethmoidal nerve anaesthesia. Tinted contact lenses had no apparent long-term benefit, although 2 cases showed a transient improvement. We found no other evidence to suggest a photic aetiology in the current series of cases. Treatment regimens based on the results of the diagnostic investigative methods included sclerosis of the posterior ethmoidal branch of the trigeminal nerve. This was effective in some cases but the benefits were temporary. Cyproheptadine alone was ineffective but the addition of carbamazepine resulted in 80-100% improvement in 80% of cases. Carbemazepine alone was effective in 88% of cases but results were unpredictable at predefined dose rates. The positive response to carbamazepine, combined with the clinical features is consistent with involvement of the trigeminal nerve, particularly the more proximal branches such as the posterior ethmoidal nerve. Headshaking has some clinical features in common with trigeminal neuralgia in humans. As a result of the findings detailed in this paper, we conclude that a trigeminal neuritis or neuralgia may be the basis of the underlying aetiopathology of equine headshaking. Initial observations of the positive response of headshakers to carbamazepine therapy is encouraging. However, future studies will include a more detailed investigation of dosages, duration of effectiveness (in some cases it appears short-lived) and other effects. In practice there is a realistic possibility of controlling but not curing headshaking with carbamazepine therapy at the present time. Other future investigations will include details of the functional anatomy of the trigeminal nerve and the role of the P2 myelin protein in headshaking and other neurological disease.

Microvascular decompression for trigeminal neuralgia in Charcot-Marie-Tooth disease

The authors report on three patients suffering from coexistent trigeminal neuralgia (TGN) and Charcot-Marie-Tooth disease who, based on preoperative magnetic resonance tomographic angiography findings, underwent microvascular decompression. All patients had demonstrable neural compression and all experienced immediate postoperative pain relief. Symptoms recurred in one patient and required a second procedure in the form of a neurotomy. Two patients suffered from bilateral TGN. When a patient with TGN suffers coexistent neurological disease and experiences bilateral symptoms, preoperative imaging and subsequent decompressive surgery may avoid the unacceptable risk of morbidity associated with bilateral ablative procedures.