Brain-stem trigeminal and auditory evoked potentials in multiple sclerosis: physiological insights

Multi-metric predictors of radiofrequency-treated trigeminal neuralgias

Evaluation of neurovascular compression-related trigeminal neuralgia (NVC-TN) and its resolution through microvascular decompression are demonstrable by MRI and intraoperatively [Leal et al. (Atrophic changes in the trigeminal nerves of patients with trigeminal neuralgia due to neurovascular compression and their association with the severity of compression and clinical outcomes: Clinical article. J Neurosurg. 2014;120(6):1484-1495)]. Non-NVC-TNs treated by radiofrequency (RF) lack such detectable features. Multimodal integration of pre-surgical diffusion tensor imaging (DTI) and volumetry (VOL) with intraoperative neurophysiology (ION) could improve understanding and performance of RF among non-NVC-TN. We hypothesized that DTI disturbances' localization (central relay versus peripherally) rather than their values bares the most significant predictive value upon outcome and that ION could quantitatively both localize and assist RF of affected branches. The first pre-surgical step evaluated the differences between affected and non-affected sides (by DTI and VOL). Four TN's segments were studied, from peripheral to central relay: Meckel's cave-trigeminal ganglion (MC-TGN), cisternal portion, root entry zone (REZ) and spinal tract [Lin et al. (Flatness of the Meckel cave may cause primary trigeminal neuralgia: A radiomics-based study. J Headache Pain. 2021;22(1):104)]. In the second intraoperative step, we used both ION and patient's testimonies to confirm the localization of the affected branch, evolving hypoesthesia, pain reduction and monitoring of adverse effects [Sindou (Neurophysiological navigation in the trigeminal nerve: Use of masticatory responses and facial motor responses evoked by electrical stimulation of the trigeminal rootlets for RF-thermorhizotomy guidance. Stereotact Funct Neurosurg. 1999;73(1-4):117-121); Sindou and Tatli (Traitement de la névralgie trigéminale par thermorhizotomie. Neurochirurgie. 2009;55(2):203-210)]. Last and postoperatively, each data set's features and correlation with short-term (3 months) and long-term outcomes (23.5 ± 6.7 months) were independently analysed and blind to each other. Finally, we designed a multimodal predictive model. Sixteen non-NVC-TN patients (mean 53.6 ± SD years old) with mean duration of 6.56 ± 4.1 years (75% right TN; 43.8% V3) were included. After 23.5 ± 6.7 months, 14/16 were good responders. Age, gender, TN duration and side/branch did not correlate with outcomes. Affected sides showed significant DTI disturbances in both peripheral (MC-TGNs) and central-relay (REZ) segments. However, worse outcome correlated only with REZ-located DTI disturbances (P = 0.04; r = 0.53). Concerning volumetry, affected MC-TGNs were abnormally flatter: lower volumes and surface area correlated with worse outcomes (both P = 0.033; r = 0.55 and 0.77, respectively). Intraoperatively, ION could not differ the affected from non-affected branch. However, the magnitude of ION's amplitude reduction (ION-Δ-Amplitude) had the most significant correlation with outcomes (r = 0.86; P < 0.00006). It was higher among responders [68.4% (50-82%)], and a <40% reduction characterized non-responders [36.7% (0-40%)]. Multiple regression showed that ION-Δ-Amplitude, centrally located only REZ DTI integrity and MC-TGN flatness explain 82.2% of the variance of post-RF visual analogue score. Integration of pre-surgical DTI-VOL with ION-Δ-Amplitude suggests a multi-metric predictive model of post-RF outcome in non-NVC-TN. In multiple regression, central-relay REZ DTI disturbances and insufficiently reduced excitability (<40%) predicted worse outcome. Quantitative fine-tuned ION tools should be sought for peri-operative evaluation of the affected branches.

Intraosseous Meningioma Along the Left Petrous Bone: A Rare Cause of Trigeminal Neuralgia

Trigeminal neuralgia (TN) presents with symptoms of intense recurrent shock-like brief pain localized to specific areas of the face innervated by the fifth cranial nerve. The pathology of trigeminal neuralgia is attributed to the fifth cranial nerve compression or demyelination. Most cases of this diagnosis are not due to bony structures, making this case an uncommon presentation of trigeminal neuralgia. Herein, we present a case of trigeminal neuralgia due to an intraosseous meningioma that formed along the left petrous bone, resulting in trigeminal nerve compression. On head computed tomography (CT), osteomatous growths along the left petrous bone were noticed compressing the trigeminal nerve. After trigeminal nerve decompression and drilling out the protruding part of the petrous bone through middle cranial fossa craniotomy, the patient's symptoms were completely improved postoperatively and at the two-month follow-up. To our knowledge, there are only four reported cases of trigeminal neuralgia caused by petrous bone compression in the literature. We emphasize the significance of considering petrous bone lesions as a cause of trigeminal neuralgia.

The role of the P2X4 receptor in trigeminal neuralgia, a common neurological disorder

Neurological disorders, which include various types of diseases with complex pathological mechanisms, are more common in the elderly and have shown increased prevalence, morbidity and mortality worldwide. Unfortunately, current therapies for these diseases are usually suboptimal or have undesirable side effects. This necessitates the development of new potential targets for disease-modifying therapies. P2X4R, a type of purinergic receptor, has multiple roles in neurological disorders. In this review, we briefly introduce a neurological disorder, trigeminal neuralgia and its' symptoms, etiology and pathology. Moreover, we focused on the role of P2X4R in neurological disorders and their related pathophysiologic mechanisms. Further studies of P2X4R are required to determine potential therapeutic effects for these pathophysiologies.

Evolution of tongue somatosensory evoked potentials in people with multiple sclerosis

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A significant deterioration of the trigeminal sensory pathway function occurs in pwMS.

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Cervical spinal cord lesions were negative predictor of tSSEP improvement.

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There is a moderate to high correlation between ordinal and quantitative tSSEP scores calculations.

Introduction

The aim of the present study was to investigate the long-term evolution of tongue somatosensory evoked potentials (tSSEP) in people with multiple sclerosis (pwMS).

Methods

Out of initial 121 participants, after two-year follow-up, the data were available for 74 and after four-year follow-up for 58 pwMS. In all pwMS complete neurological examination, brain MRI, cervical spinal cord MRI (if available) and tSSEP were performed at baseline visit (M0). Complete neurological examination and tSSEP were performed 2 and 4 years later (M24 and M48). tSSEP results were interpreted in the form of ordinal tSSEP score and quantitative tSSEP zscore calculated from the sum of z-transformed tSSEP latencies.

Results

Differences in tSSEP scores and tSSEP zscores in three different timepoints showed significant worsening of both scores over time. For the tSSEP score the difference was significant for M0-M24 and M0-M48 visits, but not for M24-M48 visits. For the tSSEP zscore the difference was significant for M0-M48 and M24-M48 visits, but not for M0-M24 visits. The only significant negative predictor found for the tSSEP score improvement was presence of cervical spinal cord lesions on the MRI. A moderate to high correlation was observed between both forms of tSSEP score at all three timepoints.

Conclusion

This study demonstrates a significant deterioration of trigeminal sensory pathway in MS over time, giving further insight into trigeminal system damage in pwMS.

Acute vestibular syndrome and hearing loss mimicking labyrinthitis as initial presentation of multiple sclerosis

Acute vestibular syndrome is most often caused by vestibular neuritis or stroke, although demyelinating diseases may be responsible for 4% of all AVS episodes. The authors present the case of a previously healthy 17-year-old female patient complaining of spontaneous vertigo and right-sided hearing loss. Otoneurological examination suggested a peripheral vestibular cause and video head impulse test revealed a reduced vestibulo-ocular reflex gain. The presence of sensorineural hearing loss raised the suspicion of a central cause and prompted imaging evaluation. A brain MRI evidenced demyelinating lesions in the right middle cerebellar peduncle and the patient was ultimately diagnosed with Multiple Sclerosis.

A novel EEG paradigm to simultaneously and rapidly assess the functioning of auditory and visual pathways

Objective assessment of the sensory pathways is crucial for understanding their development across the life span and how they may be affected by neurodevelopmental disorders (e.g., autism spectrum) and neurological pathologies (e.g., stroke, multiple sclerosis, etc.). Quick and passive measurements, for example, using electroencephalography (EEG), are especially important when working with infants and young children and with patient populations having communication deficits (e.g., aphasia). However, many EEG paradigms are limited to measuring activity from one sensory domain at a time, may be time consuming, and target only a subset of possible responses from that particular sensory domain (e.g., only auditory brainstem responses or only auditory P1-N1-P2 evoked potentials). Thus we developed a new multisensory paradigm that enables simultaneous, robust, and rapid (6-12 min) measurements of both auditory and visual EEG activity, including auditory brainstem responses, auditory and visual evoked potentials, as well as auditory and visual steady-state responses. This novel method allows us to examine neural activity at various stations along the auditory and visual hierarchies with an ecologically valid continuous speech stimulus, while an unrelated video is playing. Both the speech stimulus and the video can be customized for any population of interest. Furthermore, by using two simultaneous visual steady-state stimulation rates, we demonstrate the ability of this paradigm to track both parafoveal and peripheral visual processing concurrently. We report results from 25 healthy young adults, which validate this new paradigm.NEW & NOTEWORTHY A novel electroencephalography paradigm enables the rapid, reliable, and noninvasive assessment of neural activity along both auditory and visual pathways concurrently. The paradigm uses an ecologically valid continuous speech stimulus for auditory evaluation and can simultaneously track visual activity to both parafoveal and peripheral visual space. This new methodology may be particularly appealing to researchers and clinicians working with infants and young children and with patient populations with limited communication abilities.

Tongue somatosensory evoked potentials reflect midbrain involvement in patients with clinically isolated syndrome

AIM

To test the hypothesis that tSSEP findings reflect clinical and MRI MS lesions, the aim of this study was to investigate tSSEP changes in patients with clinically isolated syndrome (CIS) in relation to clinical and brainstem MRI findings. The second aim was to investigate whether the interpretation of the tSSEP results in the form of the tSSEP score enables better evaluation of the afferent trigeminal pathway involvement than analyzing each tSSEP parameter separately.

METHODS

115 consecutive CIS patients were enrolled from August 1, 2014 until March 1, 2016. Facial sensory symptoms and brainstem MRI (1.5 T) lesions were analyzed. tSSEP testing was performed for each patient from the raw tSSEP data. The tSSEP score was calculated separately for the left and right side (according to the cut-off values for absent response and prolonged latency of the main component, P1 (0=normal response, 1=prolonged latency, 3=absent response) and the two values were summed.

RESULTS

There was no difference in the absolute values of the tSSEP variables regarding the presence of clinical symptoms. No association was found between tSSEP abnormalities and clinical symptoms (P=0.544). Brainstem lesions (midbrain and pons) were associated with the absent tSSEP responses (P=0.002 and P=0.005, respectively). tSSEP score was significantly higher in patients with brainstem lesions (P=0.01), especially midbrain (P=0.004) and pontine (P=0.008) lesions. Binary logistic regression showed that tSSEP score had a significant effect on the likelihood that patients have midbrain MR lesions, ?2(1)=6.804, P=0.009; and the model correctly classified 87% of cases.

CONCLUSIONS

The consistent finding of this study was the association between tSSEP and midbrain lesions on MRI, indicating that tSSEP evaluates proprioception of the face. This study establishes the value of tSSEP in assessing brainstem function in early multiple sclerosis.

Risk of Ear-Associated Diseases After Zygomaticomaxillary Complex Fracture

PURPOSE

Investigate the risk of ear-associated diseases after zygomaticomaxillary complex (ZMC) fracture in a population-based retrospective cohort study.

MATERIALS AND METHODS

This is a retrospective cohort study using Taiwan's National Health Insurance Research Database of reimbursement claims. A total of 1,330 ZMC fracture patients and 5,320 non-ZMC fracture participants were included and newly developed ear-associated disease data were collected. A Poisson regression and multivariate Cox proportion hazard regression were used for data analysis.

RESULTS

The ZMC fracture cohort had a higher incidence of tinnitus than non-ZMC fracture cohort (IRR 1.64, 95 % CI 1.37-1.96), particularly in younger patients (≤34 years of age; IRR 4.05, 95 % CI 3.18-5.15) and male patients (IRR 2.08, 95 % CI 1.12-3.73). ZMC fracture patients also showed a significantly increased risk of having trigeminal neuralgia [IRR 4.06, 95 % CI 3.34-4.94, adjusted HR 4.07 (1.02-16.3)]. For sudden hearing loss and peripheral vertigo, the incidence densities were higher in the ZMC fracture cohort, but these relationships were not significant in the multivariate Cox proportional hazard regression analyses (HR 2.69, 95 % CI 0.76-9.53 for risk of sudden hearing loss; HR 1.36, 95 % CI 0.77-2.40 for risk of peripheral vertigo).

CONCLUSIONS

The findings of the study suggest an increased risk of ear-associated diseases among individuals with ZMC fractures, particularly within 2-years follow-ups after injury. We suggest performing detailed examinations for ear-associated diseases in patients with ZMC fractures for early diagnosis and adequate treatment.

Clinical neurophysiology of multiple sclerosis

The availability of new treatments able to modify the natural course of multiple sclerosis (MS) has generated interest in paraclinical measures to monitor disease evolution. Among these, neurophysiologic measures, mainly evoked potentials (EPs), are used in the functional assessment of central sensorimotor and cognitive networks affected by MS. EP abnormalities may reveal subclinical lesions, objectivate the involvement of sensory and motor pathways in the presence of vague disturbances, and provide indications of the demyelinating nature of the disease process. However, their diagnostic value is much lower than that of magnetic resonance imaging, and is more sensitive to brain and cervical spinal cord lesions. The application of EPs in assessing disease severity and monitoring the evolution of nervous damage is more promising, thanks to their good correlation with disability in cross-sectional and longitudinal studies, and potential use as paraclinical endpoints in clinical trials. Recent evidence indicates that EPs performed early in the disease may help to predict a worse future progression in the long term. If confirmed, these data suggest the possible usefulness of EPs in the early identification of patients who are more likely to develop future disability, thus requiring more frequent monitoring or being potential candidates for more aggressive disease-modifying treatments.

Incidence of facial pain in the general population

Facial pain has a considerable impact on quality of life. Accurate incidence estimates in the general population are scant. The aim was therefore to estimate the incidence rate (IR) of trigeminal neuralgia (TGN), postherpetic neuralgia (PHN), cluster headache (CH), occipital neuralgia (ON), local neuralgia (LoN), atypical facial pain (AFP), glossopharyngeal neuralgia (GPN) and paroxysmal hemicrania (PH) in the Netherlands. In the population-based Integrated Primary Care Information (IPCI) medical record database potential facial pain cases were identified from codes and narratives. Two medical doctors reviewed medical records, questionnaires from general practitioners and specialist letters using criteria of the International Association for the Study of Pain. A pain specialist arbitrated if necessary and a random sample of all cases was evaluated by a neurologist. The date of onset was defined as date of first specific symptoms. The IR was calculated per 100,000PY. Three hundred and sixty-two incident cases were ascertained. The overall IR [95% confidence interval] was 38.7 [34.9-42.9]. It was more common among women compared to men. Trigeminal neuralgia and cluster headache were the most common forms among the studied diseases. Paroxysmal hemicrania and glossopharyngeal neuralgia were among the rarer syndromes. The IR increased with age for all diseases except CH and ON, peaking in the 4th and 7th decade, respectively. Postherpetic neuralgia, CH and LoN were more common in men than women. From this we can conclude that facial pain is relatively rare, although more common than estimated previously based on hospital data.

Auditory evaluation in Parkinsonian patients

Twenty Parkinson's disease (PD) patients (mean age 69.9 years) and 24 normal individuals' (mean age 63.8) both ears were investigated by brainstem auditory evoked potentials (BAEPs) and pure tone audiometry (PTA). There were no statistically significant age differences between the patients and control subjects. PTA results were significantly elevated for PD patients in 4,000 and 8,000 Hz (P < 0.05). Parkinsonian patients showed significantly increased latencies in wave V and I-V interpeak latencies (P < 0.05). The results of this study suggest that PTA and BAEPs could be affected in parkinson disease.

Neurophysiological markers

After the advent of immunomodulatory treatment in Multiple Sclerosis and after several options for early treatment have become available, the early identification of patients non responder has become a very important issue. Therefore, methods are needed for the detection of disease activity and, particularly in more advanced phases of the disease, of disease progression. Neurophysiological methods, mainly evoked potentials (EPs), are widely used in the functional assessment of sensory and motor pathways. Their usefulness in the assessment of disease activity is limited by the fact that, although they can also reveal clinically silent lesions, EPs abnormalities are present only if their corresponding pathway is involved. With this respect, EPs have been extensively replaced by magnetic resonance imaging (MRI), with the exception of optic nerve in which the sensitivity of EPs and MRI is similar. Nevertheless, EPs can be useful for the assessment of disease progression, since their abnormalities have been demonstrated to be more strictly related to disability than MRI lesion burden. With this perspective, EPs can still be useful in the identification of non responder by providing the clinician with objective functional assessment of eloquent pathways in patients with ambiguous new symptoms, for the confirmation of a dubious relapse, and by providing a method for detecting worsening of nervous conduction for the confirmation of disease progression.

The effects of high stimulus rate on the electrocochleogram in normal-hearing subjects

The use of high stimulus rates has the potential to improve the electrocochleogram's (ECochG) sensitivity and specificity in endolymphatic hydrops and Menière's disease, but is currently hindered by the absence of an acceptable normative database. In response, this study recorded click-evoked ECochG tracings from 51 normal-hearing subjects (102 ears), between 18 and 60 years of age, at 7.1, 51.1, 101.1 and 151.1 clicks/s using a tympanic membrane electrode. As stimulus rate increased, various statistically significant (p < 0.05) changes were observed. In general, summating potential (SP) latency and amplitude and action potential (AP) latency increased, SP/AP amplitude ratio and waveform width increased but then plateaued, and AP amplitude fluctuated. While providing the largest contribution to a high-stimulus-rate ECochG normative database published to date, potential clinical limitations were identified and a possible solution proposed.

Auditory brainstem, middle-latency, and slow cortical responses in multiple sclerosis

The efficacy of auditory brainstem responses (ABRs), middle-latency responses (MLRs), and slow cortical potentials (SCPs) has been evaluated in 40 patients with multiple sclerosis (MS). ABRs and MLRs were averaged to clicks and SCPs to 1-kHz tone bursts of 70-dB nHL intensity. ABR, MLR, and SCP abnormalities were detected in 65.0, 42.5, and 30.0% of the sample, respectively. The combined sensitivity of ABRs and MLRs amounted to 80.0%, of ABRs and SCPs to 75.0%, and of MLRs and SCPs to 60.0%. The joint aptitude of all three responses equalled 87.5%. All three responses were capable to detect MS in seven of nine patients, failing to display neurological signs of brainstem lesion. The responses were also abnormal in three of five subjects with negative magnetic resonance imaging. It is concluded that the combined application of ABRs, MLRs, and SCPs promotes both detecting and confirming MS loci.

Neurophysiological investigations in multiple sclerosis

The advent of magnetic resonance imaging techniques has greatly reduced the diagnostic value of neurophysiological tests, particularly evoked potentials, in multiple sclerosis patients, because of the higher sensitivity in revealing subclinical involvement of the central nervous system. Technical progress and new methods of investigating afferent and efferent nervous pathways would seem to increase the sensitivity in detecting neural dysfunction, but the 'clinical gain' is modest at best. More promising is the utilization of neurophysiological tests to quantify the severity of white matter involvement. Transversal and longitudinal studies have demonstrated good correlations between neurophysiological parameters and disability measures, indicating that a battery of neurophysiological tests could be useful in monitoring the disease evolution in single patients and as surrogate endpoints in clinical trials. Further studies are needed for a better definition of the applications of evoked potentials and other neurophysiological techniques. Finally, event-related potentials and advanced electroencephalogram techniques, such as coherence analysis, could provide useful information on the pathophysiology of cognitive dysfunction, so common in multiple sclerosis patients, and with a strong impact on the quality of life.

Measuring evoked responses in multiple sclerosis

Evoked potentials (EPs) have been widely utilised in Multiple Sclerosis (MS) patients to demonstrate the involvement of sensory and motor pathways. Their diagnostic value is based on the ability to reveal clinically silent lesions and to objectivate the central nervous system damage in patients who complain frequently of vague and indefinite disturbances which frequently occurs in the early phases of the disease. The advent of magnetic resonance imaging (MRI) techniques has greatly reduced the clinical utilisation of EPs, which is not fully justifiable, as the information provided by EPs are quite different from those provided by MRI. The abnormalities of evoked responses reflect the global damage of the evoked nervous pathway and are significantly correlated with the clinical findings, while the vast majority of MRI lesions are not associated to symptoms and signs. Transversal and longitudinal studies have demonstrated that EP changes in MS are more strictly related to disability than MRI lesion burden. On the contrary, MRI is more sensitive than EPs in revealing the disease activity. Evoked responses modifications observed in MS are not disease-specific; moreover longitudinal studies showed latency and morphology changes of evoked responses not always related to clinical changes. Such a dissociation can be explained both by technical factors and by subclinical disease activity. To reduce the negative impact of technical aspects, only reproducible parameters of the evoked responses should be used to monitor disease evolution and therapeutic interventions.

Neurophysiological and cognitive markers of disease evolution in multiple sclerosis

Both evoked potentials and cognitive tests may provide useful information which cannot be derived from the clinical observation. For this reason, there have been some attempts to use EPs in monitoring the natural history of the disease and in assessing the efficacy of therapeutic trials. However, no conclusion can be derived from the few available data. Although MRI is more sensitive than EPs in revealing new lesions in brain, cerebellum and brainstem, EPs are more sensitive in revealing optic nerve and spinal cord lesions. Moreover, the poor relationship between brain MRI abnormalities and disability has raised the possibility that cognitive evaluation may be an additional sensitive marker of brain involvement over time. Since the gold standard for the assessment of disease activity is uncertain, it is therefore advisable that frequent MRI, EPs and cognitive assessment may integrate clinical outcomes measured by conventional scales, both in the study of the natural disease course and in monitoring clinical trials.

A comparison of neural network and Bayes recognition approaches in the evaluation of the brainstem trigeminal evoked potentials in multiple sclerosis

This article describes the application of Multi-Layer Perceptron (MLP), Probabilistic Neural Network and Kohonen's Learning Vector Quantization to the problem of diagnosing Multiple Sclerosis. The classification information is obtained from brainstem trigeminal evoked potential. The performance of the neural networks based classifiers is compared with that of the human experts and the Bayes classifier. The ability of the MLP classifier to generalize is far better than that of the Bayes classifier. The efficiency of the neural network based classifiers in conjunction with several types of well-known evoked potential features, such as Fourier transform space, latency and temporal wave, is examined. Although a large clinical data base would be necessary, before this approach can be fully validated, the initial results are promising.