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This review deals with the diagnostic usefulness of neurophysiological testing in patients with craniofacial pain. Neurophysiological testing of trigeminal nerve function relies on trigeminal reflexes and laser-evoked potentials (LEPs). This review briefly describes the physiology of trigeminal reflexes and LEPs, reports normal values and highlights the neurophysiological abnormalities in the main clinical conditions.
OBJECTIVE: To provide an educational service to the intraoperative neurophysiologist community by publishing a position statement by the American Society of Neurophysiological Monitoring on the recommended appropriate and correct use of somatosensory evoked potentials as an intraoperative neurophysiological monitoring tool to protect patient well-being during surgery. This position statement presents the somatosensory evoked potential utilization basis, relevant anatomy, patient preparation, important systemic factors, anesthesia considerations, safety and technical considerations, documentation requirements, neurophysiologist credentials and staffing practice patterns, and monitoring applications for protecting brain, spinal nerve root, peripheral nerve, plexus and spinal cord function. In conclusion, a summary of major recommendations regarding the use of somatosensory evoked potentials in intraoperative neurophysiological monitoring is presented.
OBJECTIVE: To describe finding of various neurophysiologic tests in patients with mucopolysaccharidosis III (MPS III) early in the disease course. METHODS: Patients were evaluated with flash visual evoked potentials (VEP), brainstem auditory evoked potentials (BAEP), electroencephalography (EEG), and nerve conduction studies (NCS) before they underwent hematopoietic stem cell transplantation (HSCT). RESULTS: Thirteen children underwent at least one neurophysiologic test before HSCT. The mean age at testing was 2.7 years. Ten of 11 (91%) patients had a normal flash VEP, and all 9 who had BAEP had normal central conduction. EEG was normal in 7/13 (54%), with the others showing diffuse slowing. NCS was normal in 10/11 (91%) patients. CONCLUSIONS: Despite extensive central nervous system involvement in MPS III, flash VEP and BAEP are almost always normal. EEG is often abnormal early in the disease. SIGNIFICANCE: This is the first report of neurophysiologic tests in a large series of MPS III patients.
Understanding how complex neuronal circuits in the brain perform advanced computations is a central question in neuroscience that can only be addressed using a combination of approaches, including neurophysiology and behavioral analyses. In the olfactory bulb, neurophysiological studies have revealed that neuronal interactions reorganize odor-evoked activity patterns so that their discriminability is enhanced. Recent behavioral studies have examined the role of this computation in odor discrimination tasks and generated working models of behavioral odor discrimination strategies. The results appear consistent with a role of pattern reorganization in odor discrimination behavior but further studies are necessary to resolve this issue. These studies advance the understanding of neuronal circuit function in the olfactory bulb and illustrate benefits and caveats of comparing behavioral and neurophysiological results.
The Neurophysiological Index (NI) consists of a mathematical derivation of three standardised neurophysiological measurements. Since these measurements are part of routine practice in any clinical neurophysiology laboratory, calculation of the NI is within the capability of any laboratory. The NI is derived from the CMAP, the DML and the F-wave frequency (CMAP amplitude/DML) x F frequency %), representing aspects of the effects of denervation and reinnervation, of degeneration of the terminal part of the motor axons, and of the excitability of anterior horn cells. We have shown that this simple index is reproducible in consecutive studies of normal subjects and of patients with ALS (intra-rater reliability), and is sensitive to change. In ALS, the NI differentiates rapidly and slowly progressive disease at least as sensitively as other measures in common use, including the ALS-FRS. We propose that the NI could be used as a sensitive measure of change during the course of ALS and its treatment. In combination with relevant measures of clinical benefit, such as ALS-FRS and a QoL measure, this could simplify trial design and allow more rapid determination of the efficacy of putative new therapies in clinical trials.
OBJECTIVE: The purpose of this report is to describe a neurophysiological monitoring technique that can decrease the incidence of complications while maintaining the effectiveness of the nucleus caudalis dorsal root entry zone (DREZ) operation. METHODS: Needle electrodes were used to stimulate the supraorbital, infraorbital, mental, and median nerves after the nucleus caudalis was surgically exposed. The DREZ electrode was used to record responses from the various areas in and near the nucleus. The target site was localized. Before lesioning, the site was stimulated with the DREZ electrode and electromyographic activation was sought. If no activation was observed, a lesion was made. RESULTS: Five patients underwent a total of seven nucleus caudalis DREZ procedures with complete neurophysiological monitoring. The mean number of lesions per procedure in this series was 5.4. Six procedures (86%) resulted in immediate pain relief, and five (71%) produced persistent benefit after a mean follow-up period of 12 months. Only one patient (20%) (one of seven procedures) who underwent a unilateral DREZ procedure had ataxia, which resolved within a few days. No complications were noted at follow-up. CONCLUSION: Despite patients in this series receiving fewer lesions, the efficacy of the DREZ operation was comparable to that reported in earlier studies. There were fewer complications when neurophysiological monitoring was used. Such monitoring should be considered for nucleus caudalis DREZ operations.
The discovery of the gene for Friedreich's ataxia (FRDA) has not only broadened the FRDA phenotype, but has also identified patients with early-onset cerebellar ataxia who resemble FRDA clinically but who do not carry a mutation in the frataxin gene. In order to identify subgroups that may represent a uniform underlying disorder, we performed neurophysiologic studies, including nerve conduction studies, electromyography, and transcranial magnetic stimulation, in 15 patients with a slowly progressive, unexplained, early-onset cerebellar ataxia (EOCA). In addition, sural nerve biopsy data were available in four patients. The neurophysiologic data identified three distinctive groups of EOCA patients: three patients with normal motor and sensory conduction velocities and borderline sensory amplitudes (group 1); three patients with a mild, predominantly motor, axonal neuropathy (group 2); and nine patients with a highly uniform syndrome characterized by pyramidal features and a severe sensory and motor axonal neuropathy (group 3). We conclude that, on the basis of neurophysiologic studies, distinctive groups of patients with EOCA can be delineated, and that differentiation between patients with EOCA can be useful for differential diagnostic consideration. Whether this splitting also reflects a fundamental phenotypic difference and, therefore, may direct future DNA studies, remains to be established.
Clinical Neurophysiology is rapidly moving towards complete dependence on digital instrumentation and computer-based systems. ASTM E 1467-92 "Standard Specification for Transferring Digital Neurophysiological Data Between Independent Computer Systems" was developed to allow exchange of multichannel electrophysiological waveforms, embedded textual annotations, results of mathematical processing, and clinical interpretive reports between various instruments and systems. This will permit integration of the neurophysiology laboratory interaction with hospital and clinic informations systems, and sharing of data between institutions for clinical or research purposes.
BACKGROUND: A high percentage of patients who undergo cardiac surgery experience persistent cognitive decline. The costs to insurers from brain injury associated with cardiac surgery is enormous. Furthermore, the same processes that injure the brain also appear to cause dysfunction of other vital organs. Therefore, there are great clinical and economic incentives to improve brain protection during cardiac surgery. This article discusses the methods of monitoring neurophysiologic function during heart surgery, including electroencephalography (EEG), near-infrared spectroscopy (NIRS), transcranial doppler (TCD) ultrasound, and cerebral oximetry, and analyzes the effectiveness of multi-modality neuromonitoring. METHODS: Neurophysiologic studies have implicated hypoperfusion and dysoxygenation as major causative factors for brain injury during cardiac surgery. Since these functional disturbances are often detectable and correctable, there is a new impetus to examine the role of neurophysiologic monitoring in brain protection. We have used a retrospective, single-surgeon case-control study to examine the influence on outcome following myocardial revascularization of multi-modality neuromonitoring, with modalities that include 4-channel EEG, bilateral cerebral oximetry, and single channel TCD. RESULTS: The majority of noteworthy functional disturbances detected by neuromonitoring can be corrected by simple adjustments in perfusion, oxygenation, or anesthetic administration. In more recalcitrant cases, pharmacological neuroprotection has proven effective. In addition to the substantial reductions in length of hospital stay, costs, and neurologic complications, the results of neuromonitoring suggest a possible benefit to other vital organ systems. Future studies of neuromonitoring efficacy should not overlook these important accessory benefits. CONCLUSION: This study provides the clearest evidence to date that multi-modality neuromonitoring for cardiac surgery is safe, clinically beneficial, and cost-effective. Although neuromonitoring involves negligible risk and modest costs, it's benefits for patient outcome and cost control are substantial.
Many years ago, we introduced advanced neurophysiological and psychobehavioural methods to our laboratory and have since applied our techniques on workers exposed to various occupational factors. In this article, we summarized our recent findings on the neurophysiological subclinical effects of lead, mixed solvents, toluene, styrene, local vibration and visual display terminal (VDT) work in relation to psychobehavioural effects. The methods used were as follows: 1) cerebral evoked potentials, i.e. short-latency somatosensory and visual evoked potentials (SSEP and VEP) and brainstem auditory evoked potential (BAEP), 2) event-related potential (P300), 3) psychological performance test, 4) computerized static posturography, 5) electrocardiographic R-R interval variability (CVRR), 6) distribution of nerve conduction velocities (DCV), and 7) conventional nerve conduction velocity (NCV). The following results were obtained: 1) Delay in SSEP latency in lead workers, in VEP latency in lead and VDT workers, in BAEP latency in vibrating tool workers and in P300 latency in lead workers, as well as significant correlations of P300 latency with blood lead concentrations in lead workers and of BAEP latency with length of work in brush saw operators; 2) Increase in postural sway and its significant correlation with urinary hippuric acid in toluene workers; 3) Decrease in CVRR in lead, mixed solvent, toluene, styrene and vibrating tool workers, and a significant correlation of the CVRR with length of exposure in mixed solvent workers; 4) Slowing of faster nerve fibre conduction in DCV and of NCV in lead, mixed solvent, styrene and vibrating tool workers, and their correlations with blood lead and length of work in lead and chain saw operators, respectively; 5) Decrease in the score on picture completion test in lead and styrene workers and its correlation with blood lead in lead workers. These findings suggest that recent advances in neurophysiological methods have enabled the detection of subclinical effects of various occupational and environmental factors.
Understanding the neurophysiological basis of learning enables nurses working with spinal cord injured persons to astutely assess potential for learning. This is particularly relevant when head injury or drug effects are influencing neurological systems relevant to learning. The neuroanatomical and neurophysiological bases of learning are related to attention, memory, concept formation/abstraction, reasoning, and executive systems. Concept formation/abstraction, reasoning and executive systems are discussed as they relate to learning in this article. This information is incorporated into expanded assessment. More in-depth nursing assessment related to cognitive systems necessary for learning enables nurses to identify intact and deficit cognitive systems and quantify deficits. Astute assessment is fundamental to planning effective teaching and learning strategies for spinal cord injured persons especially when learning deficits exist, e.g., in head injured persons who have sustained a spinal cord injury. Implications for client and family education derive from an understanding of the normal neurophysiological basis of learning and normal and abnormal assessment findings.
The rise of neurophysiology in the 19th century was kindled by Luigi Aloysius Galvani's revolutionary claim for animal electricity at the end of the preceding century. He was first challenged by Allessandro Giuseppe Antonio Anastasio Volta who showed that the muscle twitch in Galvani's experiment was the result of electric stimulation rather than of an enabled biological current. The controversy between Galvani and Volta became a predominant and stimulating issue among the scientists of the early century and found its ultimate elucidation only 40 years later by the pioneering work of Carlo Matteucci of Pisa and Emil Heinrich Du Bois-Reymond of Berlin, who both deserve the reknown as founders of modern neurophysiology. As the first influential promoter and mastermind of the experimental physiology, François Magendie of Paris primarily investigated the nervous system and inaugurated the lesion experiments to clarify specific functions of neural structures. Johannes Müller founded the German school of physiology with its eminent neurophysiological offspring: Du Bois-Reymond, Hermann Ludwig Ferdinand von Helmholtz, and Eduard Friedrich Wilhelm Pflüger. It was Helmholtz's merit to have for the first time precisely assessed the motor conduction velocity by measuring the time interval between two different stimulation sites of the sciatic nerve of the frog. In their brilliant work published in 1870 Gustav Theodor Fritsch and Eduard Hitzig demonstrated that appropriately located focal electrical stimulation of the exposed cortex of dogs induces movement of the contralateral limbs and unequivocally disproved the then prevailing dogma of holistic capacity of the hemispheres, which denied localised functions within the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)
Motor threshold is a means of quantifying stimulus in transcranial magnetic stimulation. Two methods are used. One involves neurophysiology techniques and the other is visualization of movement. The aim was to compare the percentage of total machine output (PTMO) necessary to achieve motor threshold using these different methods. Neurophysiological and visualization of movement thresholds were determined in six subjects. In all subjects, the two thresholds were achieved with a < 10% difference in PTMO. Determination of motor threshold with a neurophysiological and a visualization of movement method produced similar results.
INTRODUCTION: Forty two years after the first EEG had been done in our community we decided (encouraged by the Sociedad Aragonesa de Neurofisiología Clínica) to write a biographical synopsis of the specialty of neurophysiology in Aragón, since knowledge of the past usually makes for a better future. DEVELOPMENT: Initially, seven specialists, many others with their smaller contributions, the proceedings of the Sociedad Aragonesa de Neurofisiología Clínica, the proceedings of Serrate and the archives of the chair of Psychiatry of Zaragoza University have all provided information about the history of neurophysiology in Aragón. We studied the activities of public hospitals, private centres as well as academic neurophysiology activities. We also evaluated influences from outside our community in training different specialists, finding information about training in France and Germany an, in our country, in Barcelona and Pamplona. CONCLUSIONS: We observed that the specialty has now become fully developed in our community. However, it had done so in close relationship with the specialties of Neurology and Psychiatry, with which it is perfectly integrated. The university has been successfully involved in development of the specialty and, in recent years, so has the Sociedad Aragonesa de Neurofisiología Clínica.
This paper discusses the following routine examinations and new neurophysiological examinations that will likely be adopted in future. 1) EEG: a) The source derivation method and intracranial EEG recording method are useful for the detection of the exact focus in epileptic seizure. b) Polysomnography is applied to sleep disorders (ex. apnea syndrome). c) EEG topograph mapping and brain electric source analysis (BESA) are not only applied to neurological disorders, but also used for the detection of electrical equivalent dipole source localization. 2) Evoked potential (EP): ABR, SSEP and P-VEP by routine techniques are useful for the diagnosis of brain tumors and demyelinating diseases. Recently, event-related potential (ERP) has attracted attention in examining human recognition. 3) EMG and evoked EMG: a) MUP analysis with the template-matching method and single fiber EMG are topics of electromyography. b) M wave of evoked EMG has been used for the measurement of maximum nerve conduction velocity. Furthermore, the collision technique and microneurography can be applied to many kinds of nerves with different conduction velocities. c) The technique of magnetically stimulating the motor cortex was applied for the measurement of central motor conduction time (CMCT). 4) In the near future, neurophysiological examinations will include an EEG automatic diagnostic support system, neurophysiological network system, paperless digital EEG machine and non-invasive functional mapping with multichannel near infrared spectroscopic topography et al.
We describe a girl with late infantile metachromatic leukodystrophy. The patient has been followed up with serial neurologic and neurophysiologic examinations for 8 years following bone marrow transplantation, which she underwent when she was 4 3/4 years old. Her older sister died from metachromatic leukodystrophy at the age of 8 years, whereas our patient has retained significant cognitive and motor skills. Serial neurophysiologic studies initially demonstrated continued deterioration after the bone marrow transplantation, but since then, most results have remained stable or improved. Although, to our knowledge, there have been no previous serial studies of metachromatic leukodystrophy, individual case studies suggest that these findings in our patient are very unusual. With the advent of possible treatment for this condition, there is a need for further serial neurophysiologic studies to characterize the natural progression and the possible detection of progression or reversal with treatment.
To clarify the chronic effect of lead exposure on the central and peripheral nervous systems (CNS and PNS), we performed neurophysiological tests on 41 lead-exposed male workers. Unexposed workers (controls, N = 39) were examined for auditory brain stem response (ABR), and their ABR parameters were compared with those of 15 lead-exposed workers age-matched to the controls. Neurophysiological tests included those of motor and sensory nerve conduction velocity of the radial nerve (MCV, SCVwa and SCVfw), electroretinograms, pattern reversal visual evoked potential (VEP), ABR, and short-latency somatosensory evoked potentials (SLSEP). Neurophysiological parameters were analyzed by regression analysis [independent parameters: age, exposure duration, and current and time-weighted average lead concentration in whole blood (PbB and TWA-PbB)]. ABR parameters were also tested by Student's t test. Significant negative correlations were found between radial MCV and TWA-PbB and SCVwa and PbB, while significant positive correlations were found between the latency of component N145 of VEP and exposure duration and between the latency of component N20 of SLSEP and PbB. The mean of interpeak latency between component III and V of ABR of 15 lead-exposed workers was significantly prolonged compared with that of the control group. These results suggested that lead exposure has a greater effect on the conduction function in the PNS than in that of the CNS in somatosensory and auditory pathways, and inversely in visual pathway.
Prospective clinical and electrophysiological follow-up was performed on nine patients under thalidomide treatment in order to detect the very beginning of possible drug-induced peripheral neuropathy. For neurophysiological assessment, nerve conduction measurements of the median, peroneal and sural nerves (7 conduction parameters) and needle EMG examination of the anterior tibial muscle were performed. The results of a first control after about 3 months of treatment were compared with the starting point examination, and the patients were then classified as "affected" or "not affected" according to clinical and neurophysiological criteria. At this point, three patients showed clinical and electrophysiological, and another two only electrophysiological alterations suggesting early neuropathy. This classification did not change after further clinical and electrophysiological controls. Without starting-point values, the early detection of neuropathy would not have been possible in all patients. No single reliable neurophysiological parameter for detection of thalidomide-induced neuropathy could be found. Pharmacogenetic classification with regard to hydroxylation and acetylation phenotypes was then performed in some patients and interpreted with relation to thalidomide neurotoxicity. A possible relationship between slow acetylators and development of thalidomide-induced neuropathy was found.