- Email: [email protected]
C19 Late responses and reflexes: the H and T reflexes
Abstracts of the 13th European Congress of Clinical Neurophysiology / Clinical Neurophysiology 119 (2008), S1–S131 and sensory action potentials are informative in differentiation of myelin or axanol lesion. Though the method seems to be simple, there easily may be some errors. These may be due to stimulation or recording techniques. Stimulation may not be given close to the nerve or may be of submaximal intensity which may erroneously suggest conduction block. Stimulation of an unintended nerve is another possibility, and it should be excluded by inspecting unwanted muscle contraction. Unintended activation of a nerve in close proximity as in stimulation of facial or axillary nerves may lead to erroneus diagnosis or even prognosis. Collision technique may me used in that case. Inappropriate recording of the electrode is another technical problem. Positive initial deflection of the action potential must be avoided. On the other hand problems with the wire, wrong connections and ossiloscope settings are important technical factors. There may be structural anomalies of the nerves such as Martin Gruber Anastomosis from median to ulnar nerve or presence of an accessory peroneal nerve which should be analyzed carefully to avoid misinterpretation. NCSs investigate large myelinated fibers therefore it cannot exclude small fiber neuropathy. In cases of acquired demyelinating neuropathies localization of a possible focal block also needs a careful investigation during the study. Besides technical factors there may be biological factors as well such as obesity, temperature of the skin and sweating of the patient which will be mentioned in detail.
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with paresthesias/dysesthesias; 2) motor restlessness; 3) worsening of symptoms at rest with at least temporary relief by activity, and 4) worsening of symptoms in the evening or night. Polysomnographic techniques led to the recognition that the syndrome had a significant motor counterpart in the form of jerking movements arising during sleep and sometimes also wakefulness prior to sleep, called “periodic leg movements in sleep” and now defined as “periodic limb movements in sleep”. PLMS are a sleep related phenomenon with periodic episodes of repetitive and higly stereotypical movements of the lower extremities. PLMS are considered as a disorder, the “Periodic Limb Movement Disorder” (PLMD) when there are potential impact on sleep quality and as a possible source of excessive daytime sleepiness. Besides clinical symptoms, PLMS may influence some physiological measures such as heart rate, blood pressure and EEG-spectra during sleep. The actual pathophysiological mechanisms underlying the RLS and the PLMS are still unknown. PLMS may represent a spinally organized motor pattern arising upon changes in subcortical excitability recurring every 20-40 seconds during sleep. Dysfunction of the endogenous opioid and dopaminergic systems has been implicated in RLS based on the favourable effects of pharmacological interventions with opiates and with levodopa and dopaminergic agonists. The evidence however for a central dopaminergic defect based on functional neuroimaging studies is still controversial. Findings of low CSF ferritin and high transferrin in RLS have been taken to indicate a role for iron metabolism defects restricted to the central nervous systems. Finally, an animal model has been produced by lesioning the A11 hypothalamic dopaminergic system in the rat.
C14 Clinical utilization of somatosensory evoked potentials: critical review and future perspectives
C18 Late responses and reflexes: F-wave and A-wave
D. Restuccia IRCCS “La Nostra Famiglia - E. Medea”, Polo Friuli Venezia Giulia, Udine, Italy
C. Bischoff Neurologische Gemeinschaftspraxis München and Department of Neurology, Technische Universität München, Germany
In recent years, the increasing ability of neuroimaging techniques in revealing not only anatomical, but also functional abnormalities of the central nervous system has progressively reduced the clinical impact as well as the wide utilization of standard neurophysiological techniques, such as Somatosensory Evoked potentials (SEPs). Furthermore, most sophisticated SEP recording techniques often require ressources (in time and technical equipment as well) that cannot be easily provided by all laboratories. Despite tese limitations, the review of the previous Literature clearly demonstrates that the clinical use of SEPs remains still mandatory in the functional assessment of many diseases involving the somatosensory system, often justifying the utilization of expensive and/or sophisticated recording techniques. We critically review the clinical use of SEP, keeping in mind two different points: a) gold standards and widely accepted utilizations, taking into account “when and how” we have to employ either simplified or sophisticated recording tecniques; b) future perspectives, especially looking at new promising techniques, such as High-Frequency (HF) SEPs or High Frequency oscillations (HFOs), which seem to be able to provide useful informations also when the dysfunction is not necessarily linked to an anatomical lesion of somatosensory pathways.
The meaningfulness of routine nerve conduction studies can be increased when so called late responses (F-waves, and intermediate late responses) are taken into account. Stimulating a nerve at a distal site the pulses are travelling orthodromically as well as antidromically. The techniques to elicit different types of late responses are described as well as their occurrence in physiological and pathological conditions. F-waves are recurrent discharges of α-motoneurons with variable latencies, amplitudes, and configurations. They are elicited by supra-maximal stimulation travelling to the alpha motoneurons where some of them are reactivated. Parameters are minimum F-wave latency and persistence. The reference values are different in different nerves. They are of diagnostic value in patients with acquired demyelinating neuropathies and with proximal damages of peripheral nerves, e.g. reduced persistence in patients with proximal conduction block. In patients with radiculopathies they are not very helpful. A-waves follow the M-wave and are as well elicited using supra-maximal stimuli. This is different to axon reflexes which cannot be found using routine nerve stimulation. A-wave latencies may be shorter, equal or longer than those of F-waves. Unlike F-waves, they are constant in shape, latency, and configuration. Most of them have low amplitudes. The persistence is variable, between 30 and 100%. They are helpful in patients with neuropathies, but occur also in other lesions of peripheral nerves and sometimes in healthy people. In patients suffering from an acute inflammatory demyelinating neuropathy (Guillain Barré syndrome) they are of high significance as they are found prior to changes of F-waves as well as of cerebrospinal fluid confirming the diagnosis at a very early state.
C16 Sleep M. Massimini USA Abstract not received.
C19 Late responses and reflexes: the H and T reflexes C17 Neurophsiological and clinical aspects of sleep related movement disorders D. Karadeniz Kaynak Istanbul University, Cerrahpasa Faculty of Medicine Department of Neurology Sleep Disorders Unit Turkey Restless Legs Syndrome (RLS) is sleep related sensory-motor disorder in which the criteria for diagnosis is purely clinical. The proposed four minimal diagnostic criteria: 1) a desire to move the extremities, often associated
J. Valls-Sole Unitat d’EMG. Servei de Neurologia, Hospital Clínic, Barcelona, Spain Electrical stimuli over the course of a nerve activate nerve fibers, leading to different types of responses. Weak stimuli activate the largest nerve fibers, typically the Ia afferents from muscle spindles. These afferent fibers have a predominantly monosynaptic connection to the alpha motoneurones and lead to a large reflex response when recording over the target muscle, known as the H reflex. The H reflex is obtained easily at rest in the soleus, flexor
S68
Abstracts of the 13th European Congress of Clinical Neurophysiology / Clinical Neurophysiology 119 (2008), S1–S131
carpi radialis and quadriceps muscles and during voluntary activation in most muscles of the limbs. Responses of similar characteristics can be obtained by tapping on the muscle tendon, which elicits the T reflex. The study of T and H reflexes helps in the physiological study of motor control and in the clinical assessment of peripheral and central nervous system dysfunctions. Increasing the stimulus intensity induces an increase in the size of the reflex response until a significant number of motor fibers are recruited and there is collision between orthodromic and antidromic volleys. The H reflexes elicited with a stable stimulus intensity reflect the excitability of the segmental refex circuit and, therefore, they can be used to evaluate dysfunctions of the pyramidal tract. The H reflex is the probe used for testing spinal cord interneuronal function, such as reciprocal inhibition, presynaptic inhibition, recurrent inhibition or autogenetic inhibition, circuits that may be abnormal in many central nervous system disorders. Since they are elicited by activation of the largest nerve fibers, the abnormality of the H reflexes may also be due to peripheral neuropathies that involve large myelinated fibers. In distal axonopathies, the T reflex may be absent while the H reflex is still preserved. In radiculopathies, the H reflex may be absent or abnormally reduced while the sensory nerve conduction is preserved, as evidence for preganglionic lesion topography.
C21 Neurophysiological approach to dysphagia C. Ertekin Turkey Dysphagia is a severe and frequent symptom complex that can be lifethreating in a considerable number of patients. Three-forth of oropharyngeal dysphagia is caused by neurological diseases. The neurophysiology of swallowing has been reviewed in regard to deglutitional clinical problems, such as aspiration. There are many methods to investigate the swallows and its problems. But in this course, the EMG and other clinical neurophysiological methods are emphasized. Afterward the neurogenic dysphagia will be classified according to the clinical and electrophysiological data. Clinical and EMG data from cortex to the striated muscles of the oropharynx including cricopharyngeal sphincter will be given according to the disorders of pyramidal, extrapyramidal, bulbar central pattern generator or peripheral neuromuscular system
C22 Neurophysiological approach to dysphagia E. Alfonsi Italy Abstract not received.
C23 Contributions of microneurography to the study of the pathophysiology of neuropathic pain and other types of positive sensory phenomena J. Serra Department of Neurology, MC Mutual, Barcelona, Spain Patients with peripheral neuropathy commonly express positive sensory symptoms, such as paresthesias, dysesthesias and different types of pain. As opposed to negative sensory phenomena whose electrophysiological correlate can be readily measured through conventional laboratory methods, the study of positive sensory phenomena is problematic. In animals, possible electrophysiological correlates of positive sensory phenomena have been documented in traumatic neuromas and in demyelinated nerve fibers. In experimental human volunteers, ectopic nerve impulses generated in single myelinated sensory fibers have been correlated with post-ischemic and posttetanic paresthesias. In patients with peripheral neuropathy, abnormal nerve impulse activity in afferent fibers has occasionally been recorded. In all cases, such activity was either spontaneous or elicited by mechanical stimuli applied at injured mid-axon level. Recent microneurographic techniques permit recording from individual unmyelinated C fibers and allow their segregation into different functional classes having discrete electrophysiological properties of their membranes. Particularly important for the study of neuropathic pain is the recording from
mechano-sensitive as well as mechano-insensitive, or silent, nociceptors. Stimulation at low rates following a pause differentiates between them, while stimulation at 2 Hz for 3 minutes differentiates patterns of slowing among functional types of C fibres. Different abnormalities have been identified: spontaneous ectopic impulse generation, sensitization to mechanical, heat and cold stimuli, and “multispike” responses. It is becoming clear that Cnociceptor function abnormalities may explain some of the positive sensory phenomena expressed by patients with peripheral neuropathic pain. This has important implications to design future research strategies. References: [1] Two types of C nociceptors in human skin and their behavior in areas of capsaicin-induced secondary hiperalgesia. J Serra, M Campero, H Bostock, JL Ochoa. J Neurophysiol 2004 Jun;91:2770-81. [2] Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin. J. Serra, M. Campero, J. Ochoa, H. Bostock. J Physiol 1999;515:799-811.
C24 Routine EEG for epilepsy G. Rubboli Department of Neurosciences, Bellaria Hospital, Bologna, Italy Electroencephalography (EEG) remains an essential tool in the diagnosis and management of epilepsy. Indeed, it is still essential: a) in a first unprovoked seizure either for the diagnosis and for the prognosis, being able to predict the risk of seizure recurrence. After a first unprovoked seizure, EEG evidence of epileptiform activity (such as generalized spike and wave discharges or focal spikes) may indicate a greater risk of recurrence. Some data suggest that routine EEG performed within 24 hours from the first seizure, associated with sleep EEG and neuroimaging studies (CT/MRI scans) may yield information allowing a syndromic diagnosis of the epilepsy type. b) in the definition of the epileptic syndrome. Some EEG epileptiform abnormalities can be considered highly specific of certain epileptic syndromes (i.e., 3 c/sec generalized spike-and-wave discharge in childhood absence epilepsy). EEG supplemented by polygraphic channels may be crucial in some diagnostic processes: for instance, implementation of EMG polygraphic channels may add helpful data for the syndromic classification of epilepsies (i.e., demonstrating the occurrence of positive/negative myoclonia in relation of epileptiform activities). c) in the choice of antiepileptic treatment. EEG “per se“ has no absolute value regarding orientation for the treatment of epilepsy; however, when it is used to supplement the clinical data is a most valuable aide in choosing and modifying a treament. d) in the presurgical assessment of drug-resistant focal epilepsies. Interictal epileptiform abnormalities may have a diagnostic and prognostic significance in the selection of surgical candidates; however, issues such as when interictal epileptiform abnormalities may be relied upon in the absence of ictal recordings or whether different types of interictal temporal epileptiform abnormalities with different diagnostic and prognostic implications do exist are not completely resolved.
C25 Routine EEG for epilepsy P. Jallon Switzerland Abstract not received.
C26 Laser EPs M. Valeriani Italy In the seventies, the technique of laser evoked potential (LEP) has been introduced for pain research. Indeed, unlike the electrical stimuli used for the recording of the standard somatosensory evoked potentials, CO2 laser pulses delivered to the hairy skin activate the nociceptive A delta and C fibers selectively, without any concurrent stimulation of the non-nociceptive A beta
S67
with paresthesias/dysesthesias; 2) motor restlessness; 3) worsening of symptoms at rest with at least temporary relief by activity, and 4) worsening of symptoms in the evening or night. Polysomnographic techniques led to the recognition that the syndrome had a significant motor counterpart in the form of jerking movements arising during sleep and sometimes also wakefulness prior to sleep, called “periodic leg movements in sleep” and now defined as “periodic limb movements in sleep”. PLMS are a sleep related phenomenon with periodic episodes of repetitive and higly stereotypical movements of the lower extremities. PLMS are considered as a disorder, the “Periodic Limb Movement Disorder” (PLMD) when there are potential impact on sleep quality and as a possible source of excessive daytime sleepiness. Besides clinical symptoms, PLMS may influence some physiological measures such as heart rate, blood pressure and EEG-spectra during sleep. The actual pathophysiological mechanisms underlying the RLS and the PLMS are still unknown. PLMS may represent a spinally organized motor pattern arising upon changes in subcortical excitability recurring every 20-40 seconds during sleep. Dysfunction of the endogenous opioid and dopaminergic systems has been implicated in RLS based on the favourable effects of pharmacological interventions with opiates and with levodopa and dopaminergic agonists. The evidence however for a central dopaminergic defect based on functional neuroimaging studies is still controversial. Findings of low CSF ferritin and high transferrin in RLS have been taken to indicate a role for iron metabolism defects restricted to the central nervous systems. Finally, an animal model has been produced by lesioning the A11 hypothalamic dopaminergic system in the rat.
C14 Clinical utilization of somatosensory evoked potentials: critical review and future perspectives
C18 Late responses and reflexes: F-wave and A-wave
D. Restuccia IRCCS “La Nostra Famiglia - E. Medea”, Polo Friuli Venezia Giulia, Udine, Italy
C. Bischoff Neurologische Gemeinschaftspraxis München and Department of Neurology, Technische Universität München, Germany
In recent years, the increasing ability of neuroimaging techniques in revealing not only anatomical, but also functional abnormalities of the central nervous system has progressively reduced the clinical impact as well as the wide utilization of standard neurophysiological techniques, such as Somatosensory Evoked potentials (SEPs). Furthermore, most sophisticated SEP recording techniques often require ressources (in time and technical equipment as well) that cannot be easily provided by all laboratories. Despite tese limitations, the review of the previous Literature clearly demonstrates that the clinical use of SEPs remains still mandatory in the functional assessment of many diseases involving the somatosensory system, often justifying the utilization of expensive and/or sophisticated recording techniques. We critically review the clinical use of SEP, keeping in mind two different points: a) gold standards and widely accepted utilizations, taking into account “when and how” we have to employ either simplified or sophisticated recording tecniques; b) future perspectives, especially looking at new promising techniques, such as High-Frequency (HF) SEPs or High Frequency oscillations (HFOs), which seem to be able to provide useful informations also when the dysfunction is not necessarily linked to an anatomical lesion of somatosensory pathways.
The meaningfulness of routine nerve conduction studies can be increased when so called late responses (F-waves, and intermediate late responses) are taken into account. Stimulating a nerve at a distal site the pulses are travelling orthodromically as well as antidromically. The techniques to elicit different types of late responses are described as well as their occurrence in physiological and pathological conditions. F-waves are recurrent discharges of α-motoneurons with variable latencies, amplitudes, and configurations. They are elicited by supra-maximal stimulation travelling to the alpha motoneurons where some of them are reactivated. Parameters are minimum F-wave latency and persistence. The reference values are different in different nerves. They are of diagnostic value in patients with acquired demyelinating neuropathies and with proximal damages of peripheral nerves, e.g. reduced persistence in patients with proximal conduction block. In patients with radiculopathies they are not very helpful. A-waves follow the M-wave and are as well elicited using supra-maximal stimuli. This is different to axon reflexes which cannot be found using routine nerve stimulation. A-wave latencies may be shorter, equal or longer than those of F-waves. Unlike F-waves, they are constant in shape, latency, and configuration. Most of them have low amplitudes. The persistence is variable, between 30 and 100%. They are helpful in patients with neuropathies, but occur also in other lesions of peripheral nerves and sometimes in healthy people. In patients suffering from an acute inflammatory demyelinating neuropathy (Guillain Barré syndrome) they are of high significance as they are found prior to changes of F-waves as well as of cerebrospinal fluid confirming the diagnosis at a very early state.
C16 Sleep M. Massimini USA Abstract not received.
C19 Late responses and reflexes: the H and T reflexes C17 Neurophsiological and clinical aspects of sleep related movement disorders D. Karadeniz Kaynak Istanbul University, Cerrahpasa Faculty of Medicine Department of Neurology Sleep Disorders Unit Turkey Restless Legs Syndrome (RLS) is sleep related sensory-motor disorder in which the criteria for diagnosis is purely clinical. The proposed four minimal diagnostic criteria: 1) a desire to move the extremities, often associated
J. Valls-Sole Unitat d’EMG. Servei de Neurologia, Hospital Clínic, Barcelona, Spain Electrical stimuli over the course of a nerve activate nerve fibers, leading to different types of responses. Weak stimuli activate the largest nerve fibers, typically the Ia afferents from muscle spindles. These afferent fibers have a predominantly monosynaptic connection to the alpha motoneurones and lead to a large reflex response when recording over the target muscle, known as the H reflex. The H reflex is obtained easily at rest in the soleus, flexor
S68
Abstracts of the 13th European Congress of Clinical Neurophysiology / Clinical Neurophysiology 119 (2008), S1–S131
carpi radialis and quadriceps muscles and during voluntary activation in most muscles of the limbs. Responses of similar characteristics can be obtained by tapping on the muscle tendon, which elicits the T reflex. The study of T and H reflexes helps in the physiological study of motor control and in the clinical assessment of peripheral and central nervous system dysfunctions. Increasing the stimulus intensity induces an increase in the size of the reflex response until a significant number of motor fibers are recruited and there is collision between orthodromic and antidromic volleys. The H reflexes elicited with a stable stimulus intensity reflect the excitability of the segmental refex circuit and, therefore, they can be used to evaluate dysfunctions of the pyramidal tract. The H reflex is the probe used for testing spinal cord interneuronal function, such as reciprocal inhibition, presynaptic inhibition, recurrent inhibition or autogenetic inhibition, circuits that may be abnormal in many central nervous system disorders. Since they are elicited by activation of the largest nerve fibers, the abnormality of the H reflexes may also be due to peripheral neuropathies that involve large myelinated fibers. In distal axonopathies, the T reflex may be absent while the H reflex is still preserved. In radiculopathies, the H reflex may be absent or abnormally reduced while the sensory nerve conduction is preserved, as evidence for preganglionic lesion topography.
C21 Neurophysiological approach to dysphagia C. Ertekin Turkey Dysphagia is a severe and frequent symptom complex that can be lifethreating in a considerable number of patients. Three-forth of oropharyngeal dysphagia is caused by neurological diseases. The neurophysiology of swallowing has been reviewed in regard to deglutitional clinical problems, such as aspiration. There are many methods to investigate the swallows and its problems. But in this course, the EMG and other clinical neurophysiological methods are emphasized. Afterward the neurogenic dysphagia will be classified according to the clinical and electrophysiological data. Clinical and EMG data from cortex to the striated muscles of the oropharynx including cricopharyngeal sphincter will be given according to the disorders of pyramidal, extrapyramidal, bulbar central pattern generator or peripheral neuromuscular system
C22 Neurophysiological approach to dysphagia E. Alfonsi Italy Abstract not received.
C23 Contributions of microneurography to the study of the pathophysiology of neuropathic pain and other types of positive sensory phenomena J. Serra Department of Neurology, MC Mutual, Barcelona, Spain Patients with peripheral neuropathy commonly express positive sensory symptoms, such as paresthesias, dysesthesias and different types of pain. As opposed to negative sensory phenomena whose electrophysiological correlate can be readily measured through conventional laboratory methods, the study of positive sensory phenomena is problematic. In animals, possible electrophysiological correlates of positive sensory phenomena have been documented in traumatic neuromas and in demyelinated nerve fibers. In experimental human volunteers, ectopic nerve impulses generated in single myelinated sensory fibers have been correlated with post-ischemic and posttetanic paresthesias. In patients with peripheral neuropathy, abnormal nerve impulse activity in afferent fibers has occasionally been recorded. In all cases, such activity was either spontaneous or elicited by mechanical stimuli applied at injured mid-axon level. Recent microneurographic techniques permit recording from individual unmyelinated C fibers and allow their segregation into different functional classes having discrete electrophysiological properties of their membranes. Particularly important for the study of neuropathic pain is the recording from
mechano-sensitive as well as mechano-insensitive, or silent, nociceptors. Stimulation at low rates following a pause differentiates between them, while stimulation at 2 Hz for 3 minutes differentiates patterns of slowing among functional types of C fibres. Different abnormalities have been identified: spontaneous ectopic impulse generation, sensitization to mechanical, heat and cold stimuli, and “multispike” responses. It is becoming clear that Cnociceptor function abnormalities may explain some of the positive sensory phenomena expressed by patients with peripheral neuropathic pain. This has important implications to design future research strategies. References: [1] Two types of C nociceptors in human skin and their behavior in areas of capsaicin-induced secondary hiperalgesia. J Serra, M Campero, H Bostock, JL Ochoa. J Neurophysiol 2004 Jun;91:2770-81. [2] Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin. J. Serra, M. Campero, J. Ochoa, H. Bostock. J Physiol 1999;515:799-811.
C24 Routine EEG for epilepsy G. Rubboli Department of Neurosciences, Bellaria Hospital, Bologna, Italy Electroencephalography (EEG) remains an essential tool in the diagnosis and management of epilepsy. Indeed, it is still essential: a) in a first unprovoked seizure either for the diagnosis and for the prognosis, being able to predict the risk of seizure recurrence. After a first unprovoked seizure, EEG evidence of epileptiform activity (such as generalized spike and wave discharges or focal spikes) may indicate a greater risk of recurrence. Some data suggest that routine EEG performed within 24 hours from the first seizure, associated with sleep EEG and neuroimaging studies (CT/MRI scans) may yield information allowing a syndromic diagnosis of the epilepsy type. b) in the definition of the epileptic syndrome. Some EEG epileptiform abnormalities can be considered highly specific of certain epileptic syndromes (i.e., 3 c/sec generalized spike-and-wave discharge in childhood absence epilepsy). EEG supplemented by polygraphic channels may be crucial in some diagnostic processes: for instance, implementation of EMG polygraphic channels may add helpful data for the syndromic classification of epilepsies (i.e., demonstrating the occurrence of positive/negative myoclonia in relation of epileptiform activities). c) in the choice of antiepileptic treatment. EEG “per se“ has no absolute value regarding orientation for the treatment of epilepsy; however, when it is used to supplement the clinical data is a most valuable aide in choosing and modifying a treament. d) in the presurgical assessment of drug-resistant focal epilepsies. Interictal epileptiform abnormalities may have a diagnostic and prognostic significance in the selection of surgical candidates; however, issues such as when interictal epileptiform abnormalities may be relied upon in the absence of ictal recordings or whether different types of interictal temporal epileptiform abnormalities with different diagnostic and prognostic implications do exist are not completely resolved.
C25 Routine EEG for epilepsy P. Jallon Switzerland Abstract not received.
C26 Laser EPs M. Valeriani Italy In the seventies, the technique of laser evoked potential (LEP) has been introduced for pain research. Indeed, unlike the electrical stimuli used for the recording of the standard somatosensory evoked potentials, CO2 laser pulses delivered to the hairy skin activate the nociceptive A delta and C fibers selectively, without any concurrent stimulation of the non-nociceptive A beta