Why and when to refer patients for vestibular evoked myogenic potentials: A critical review.

Cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs respectively) are now used by an increasing number of laboratories to evaluate otolith inner ear function and their pathways through the central nervous system. However, the literature is incomplete or unclear as to what information both c- and oVEMPs can add beyond what a good clinical examination can provide, and what other paramedical tests can provide also, and the present review aims to clarify what is known so far. The following review will describe what is known with regards to both c- and oVEMPs and their use. MEDLINE (accessed by PubMed, years 1994-2018) was searched with the following string: ("vestibular evoked myogenic potentials" [all fields]). Only articles published in English were evaluated. Both c- and oVEMPs are useful not only for confirming the presence of superior semicircular canal dehiscence (SSCD), but also for confirming the presence of acoustic neuromas when MRI is not available, bilateral vestibulopathies, inferior vestibular neuritis and vestibular dysfunction in inherited neuropathies. Further work is required, especially with respect to oVEMPs. The usefulness of both c- and oVEMPs goes beyond the confirmation of SSCDs, and is useful in many clinical cases.

Pharmacoresistant partial-onset epilepsy misdiagnosed as panic disorder: a case report.

The clinical differentiation between simple partial epileptic seizures of temporal lobe origin and panic attacks is often difficult on clinical grounds alone, because both conditions are characterized by common symptomatology which includes the feeling of fear, autonomic system dysfunction, disorientation and alternation of the level of consciousness when these conditions evolve clinically. The symptoms stem from common pathophysiologic and anatomic substrates of these two conditions, localized in the limbic system, especially the amygdala. We present the case of a young woman who had a febrile seizure in childhood and subsequent episodes of fear accompanied by tremor and possible alteration of consciousness followed by headache. These spells were diagnosed as panic attacks during her teenage years and she was given Clobazam in order to suppress them. The patient responded well for several years without attacks but her symptoms reappeared following discontinuation of her medication in order to conceive. At that time a detailed history was taken from her spouse and further clinical evaluation raised the suspicion of seizures especially due to the fact that her spells were characterized by alteration of consciousness; she was therefore referred for additional investigations which included admission to a monitoring unit for epilepsy. Long-term video-EEG recording revealed the presence of simple partial seizures with secondary generalization confirming the clinical impression. She was subsequently treated with antiepileptic medications; however the patient's condition worsened to the point where she became pharmacoresistant having failed several antiepileptic drug trials in monotherapy or combination. An MRI scan of the brain revealed the presence of right-sided mesial temporal sclerosis, a known consequence of febrile seizures. Her seizures were nocturnal tonic-clonic and gradually worsened to the point of occurring during most nights. She was therefore referred for a presurgical evaluation which confirmed that the epileptic focus was associated with the area of mesial temporal sclerosis. The epileptic focus was successfully removed from the right anterior temporal lobe and since then she remained free of seizures whereas, in addition, the presumed symptoms of panic attacks also resolved. This case indicates the occasional difficulty in diagnosing simple partial seizures and how it may be confused with psychiatric conditions. Therefore, the treating physician, especially the psychiatrist, should remain vigilant when treating cases of panic attacks, especially when they present with either atypical symptomatology, such as the case described, or when they do not respond to appropriately chosen treatment; such cases may warrant referral for further investigation.

Management of obstructive sleep apnea in Europe.

OBJECTIVES: In Europe, the services provided for the investigation and management of obstructive sleep apnoea (OSA) varies from country to country. The aim of this questionnaire-based study was to investigate the current status of diagnostic pathways and therapeutic approaches applied in the treatment of OSA in Europe, qualification requirements of physicians involved in diagnosis and treatment of OSA, and reimbursement of these services. METHODS: Two questionnaires were sent to 39 physicians in 22 countries in Europe. In order to standardize the responses, the questionnaire was accompanied by an example. RESULTS: Sleep centers from 21 countries (38 physicians) participated. A broad consistency among countries with respect to the following was found: pathways included referral to sleep physicians/sleep laboratories, necessity for objective diagnosis (primarily by polysomnography), use of polygraphic methods, analysis of polysomnography (PSG), indications for positive airway pressure (PAP) therapy, application of standard continuous PAP (CPAP) therapy (100% with an CPAP/APAP ratio of 2.24:1), and the need (90.5%) and management of follow-up. Differences were apparent in reimbursement of the diagnostic procedures and follow-up, in the procedures for PAP titration from home APAP titration with portable sleep apnea monitoring (38.1%) up to hospital monitoring with PSG and APAP (85.7%), and in the qualification requirements of sleep physicians. CONCLUSIONS: Management of OSA in different European countries is similar except for reimbursement rules, qualification of sleep specialists and procedures for titration of the CPAP treatment. A European network (such as the one accomplished by the European Cooperation in Science and Technology [COST] B26 Action) could be helpful for implementing these findings into health-service research in order to standardize management in a cost effective perspective.

Brainstem lesions may be important in the development of epilepsy in multiple sclerosis patients: an evoked potential study.

OBJECTIVE: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system, with epileptic seizures sometimes observed in the same patients. In this study, we used evoked responses to study the pathogenesis of epilepsy in MS. METHODS: Patients with a diagnosis of definite MS and who had EPs performed (visual (VEP), brainstem auditory (BAEP) and short latency somatosensory (upper (USSEP) and lower (LSSEP))) were retrospectively included in this study. They were divided into three groups; Group I: Patients with no epilepsy and who were not taking anti-epileptic drugs (AED); Group II: Patients with epilepsy and taking AEDs; and Group III: Patients with no epilepsy who were taking AEDs for symptoms related to neuropathic pain. RESULTS: Three hundred and fifty-five patients were included in this study; Group I: 229 patients (64.5%), Group II: 20 patients (5.6%) and Group III: 106 patients (29.9%). The proportion of patients with abnormal BAEP and USSEP was higher in Group II. CONCLUSIONS: A positive association exists between the presence of epilepsy in MS patients and BAEP and USSEP abnormalities. Analysis of Group III ruled out AED use as a factor. SIGNIFICANCE: Brainstem lesions may be the cause of epileptogenicity in MS.

Induction of central-type sleep apnea by vagus nerve stimulation.

Vagus nerve stimulation (VNS) is an acceptable and effective adjunctive therapy for pharmacoresistant epilepsy. It is generally well tolerated and the most frequent side effects reported include respiratory dysfunction. We report the case of a female patient with intractable epilepsy who was implanted with the device and achieved a significant reduction in the number of her seizures. However, she developed central-type sleep apnea documented polysomnographically. Upon reduction of her VNS parameters, the apnea resolved and her sleep study reverted to normal. To our knowledge, this is the first case reported with polysomnographic evidence of VNS induction of central-type sleep apnea.

Vertigo and imbalance caused by a small lesion in the anterior insula.

The exact location of the vestibular cortex in humans has not yet been established. Isolated lesions in the insula are exceptional. We describe a patient with recurrent episodes of vertigo and imbalance following a small lesion in the anterior insula. Myogenic and neurogenic vestibular evoked potentials were both performed using auditory stimuli. The former was recorded from the sternocleidomastoid muscle and the latter from the parietal areas on the scalp. Brainstem auditory evoked potentials, threshold latency series, pure tone audiometry and video nystagmography were also performed, as was brain MRI. All evoked potential studies and pure tone audiometry were within normal limits, ruling out peripheral and brainstem causes for the patient's symptoms. Video nystagmography revealed high slow phase velocities bilaterally with caloric stimulation, and saccadic tracking on the smooth pursuit examination. The MRI revealed a small lesion in the right anterior insula. To our knowledge this is the first reported case of vestibular symptoms and signs from a lesion in the anterior insula on MRI. In addition, its effects on the nystagmogram suggest that this area may be part of the pathway that controls smooth pursuit.

Parallel auditory vestibular evoked neurogenic and myogenic potential results in a case of peripheral vestibular dysfunction, showing that the former originates from the vestibular system.

PURPOSE: Vestibular evoked myogenic potentials (VEMPs) uses high intensity clicks with recording from the tonically active sternocleidomastoid muscle, taking advantage of the close proximity of the saccule to the oval window. Our group has used the same stimulus to record Vestibular Evoked Neurogenic Potentials (VENPs) directly from the brain. VEMPs are now regarded the electrophysiological gold standard in peripheral vestibular system examination. We present a case of peripheral vestibular dysfunction to show that both VEMPs and VENPs provide similar results during recovery. METHODS: A case of Meniere's Disease in recovery is examined. VEMPs were recorded using a 105 dB nHL click stimulus from the ipsilateral sternocleidomastoid muscle. VENPs were recorded using an ipsilateral parietal to Fpz montage and a 1 kHz tone-pip stimulus. Standard BAEPs and threshold latency series (TLS) were performed. RESULTS: VEMP and VENP were unobtainable from the left side at initial presentation in a patient with Meniere's Disease, with normal BAEP and TLS bilaterally. After one month of therapy both the VEMP and VENP normalized. CONCLUSIONS: As VEMPs are known to originate from the vestibular system, the parallel VENP result suggests the same for the latter VENP may prove to be useful and complement VEMP in determining vestibular dysfunction.

Vestibular symptoms and signs are correlated with abnormal neurogenic vestibular evoked potentials in patients with multiple sclerosis.

OBJECTIVES: Symptoms of disequilibrium in multiple sclerosis (MS) are common. Neurogenic vestibular evoked potentials (NVsEPs) are saccular responses to tone-pip acoustic stimuli and are recordable from the parietal areas ipsilaterally to the stimulated ear. We wished to determine possible correlations of abnormal findings in NVsEP with clinical neurological findings related to the vestibular system, and demyelination seen on MRI. PATIENTS AND METHODS: NVsEPs were performed by delivering a 1 kHz tone-pip stimulus monoaurally with contralateral masking noise via headphones. Brainstem auditory evoked potentials were performed in the standard manner. RESULTS: Thirty-three patients had either been diagnosed with MS or had possible MS. There is statistical evidence that the presence of symptoms is likely to give an abnormal NVsEP, but no correlation exists between the presence or absence of vestibular symptoms and signs and an abnormal BAEP. No correlation was found between the presence of brainstem lesions on MRI and an abnormal NVsEP. Correlation exists between abnormal NVsEP and the level of disability using Expanded Disability Status Scale scores. CONCLUSION: We have found that with increasing involvement of abnormal NVsEPs, there is a significant correlation with symptoms and signs that can be referred to the vestibular system.

Ulnar neuropathy at Guyon's canal: electrophysiological and surgical findings.

Published correlations between electrophysiological and surgical findings are relatively rare in cases of ulnar nerve compression at the wrist, compared to the more common compression of the ulnar nerve at the elbow. We describe a patient who presented with clinical and electrodiagnostic findings of a pure motor ulnar neuropathy involving the territory of the deep branch. Surgical exploration revealed that a ganglion cyst caused compression of the deep ulnar motor branch at Guyon's canal. This case illustrates the usefulness of electrodiagnostic studies in the localization of nerve entrapment prior to surgery.

Neurogenic vestibular evoked potentials in three cases of vestibular system dysfunction.

OBJECTIVES: To demonstrate that neurogenic vestibular evoked potentials (NVsEP) may be specific to the vestibular system using three cases of vestibular system dysfunction and normal auditory function, METHODS: Neurogenic vestibular evoked potentials were performed by recording from the parietal areas of the scalp using a tone-pip auditory stimulus via headphones. Brainstem auditory evoked potentials (BAEPs) and NVsEP were performed in all three cases. RESULTS: Brainstem auditory evoked potentials were within normal limits in all three cases. All three patients showed abnormalities in their NVsEP In the third case, the responses normalized after treatment. CONCLUSIONS: The findings support further the hypothesis that NVsEP are specific to the vestibular system and are a separate response from the BAEP SIGNIFICANCE: Neurogenic vestibular evoked potentials is an easy examination to carry out and can be performed in any clinical neurophysiological laboratory that is familiar with BAEPs. Examinations used to diagnose vestibular system disorders at present include the glycerol dehydration test, electrocochleography, myogenic vestibular evoked potentials and electronystagmography. Neurogenic vestibular evoked potentials may also prove to be useful.

Neurogenic vestibular evoked potentials in the diagnosis of multiple sclerosis.

OBJECTIVES: To determine the value of neurogenic vesibular evoked potential (NVESTEP) studies in comparison with other paraclinical tests in demonstrating dissemination in time and space in Multiple Sclerosis (MS) and in identifying clinically silent lesions. METHOD: All patients in whom MS was suspected but the diagnosis of MS was not possible based on the McDonald criteria were included in this study. We studied 14 patients and performed visual, brainstem auditory, somatosensory and neurogenic vestibular evoked potentials in all patients, together with MRI and CSF analysis of oligoclonal bands (OB). RESULTS: Two out of the thirteen patients could be movedfrom the category of "possible MS" to "MS" using the McDonald criteria based on an abnormal NVESTEP result. CONCLUSION: Neurogenic vestibular evoked potentials are potentially useful in identifying clinically silent lesions in patients with possible MS.

Neurogenic vestibular evoked potentials using a tone pip auditory stimulus.

OBJECTIVES: To obtain neurogenic vestibular evoked potentials (NVESTEPs) with surface scalp recording using a tone pip auditory stimulus. METHODS: Fourteen neurologically normal volunteers (Age range 26-45 years, 10 females and 4 males), and two patients with sensorineural hearing loss and possible multiple sclerosis respectively, were examined. Two channel recordings were obtained, the first channel being P3 referred to Fpz, and the second channel being P4 referred to Fpz. A 1 kHz tone pip stimulus with two cycles was delivered via headphones monoaurally with contralateral masking noise. RESULTS: A consistent negative wave with a mean absolute latency of 4.72 msec was obtained, which we have named N5. 25% of the ears tested had better responses at the ipsilateral parietal electrode. In the patient with bilateral sensorineural hearing loss, NVESTEPs was present, suggesting that the NVESTEP is not a cochlear response. In the patient with possible multiple sclerosis, an abnormal NVESTEP response and a normal BAEP response were found. CONCLUSION: Use of a tone-pip rather than a click auditory stimulus allows a lower click intensity to be used in the production of NVESTEP responses, leads to a shorter testing time, and is therefore more comfortable for the patient. This study adds to our impression that the NVESTEP may be a physiological response that can be used to assess the vestibular system and is different from the BAEP response. Further testing in patients with symptoms of dizziness and with disorders specific for the vestibular nerve is required.

Radial nerve F-waves: normative values with surface recording from the extensor indicis muscle.

OBJECTIVES: In the present study we set out to obtain normative values for radial nerve F-waves, with surface recording from the extensor indicis muscle. METHODS: Forty-nine patients with unrelated complaints were tested. Surface recording electrodes were placed on the extensor indicis muscle. This was found by asking the patient to extend the second digit against resistance. The active surface recording electrode was placed over the most distal portion of the muscle, near the radial border of the ulnar bone near the wrist. Stimulation was performed near the lateral epicondyle between the radial and ulnar bones. RESULTS: The mean F-wave minimum latency was found to be 20.55 ms, with an upper limit of 24.35 ms. The absolute interside minimum latency difference was found to have a mean of 0.55 ms, with a maximum of 1.7 ms. The mean amplitude of the F-waves was 145.61 microV and the mean mF/M ratio was 0.022. F-waves were unobtainable in 2/62 (3.2%) of limbs. Normative values for the radial nerve motor response were also obtained. Three cases are described to illustrate the usefulness of the above technique. CONCLUSIONS: It is technically feasible to record radial nerve F-waves from the extensor indicis muscle.