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FC6.4 Somatosensory evoked potential monitoring during carotid endarterectomy
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Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
FC6.4 Somatosensory evoked potential monitoring during carotid endarterectomy F. Traverso 1, B. Peluffo 2, C. Bertoglio 3, A. Cristiani 3, C. Serrati 2 1 2 3
Sanremo Hospital, Neurology, Italy Imperia Hospital, Neurology, Italy Imperia Hospital, Vascular Surgery, Italy
Carotid endarterectomy (CEA) is a widely accepted treatment of carotid disease. Controversy still remains with regards to the optimal method to protect the brain from possible hemodynamic ischaemia during CEA: local or general anaesthesia, with or without shunt, EEG or somatosensory evoked potential (SEP) monitoring. Although the SEPs for CEA are widely used, the published studies are few and generally done on small cohorts of patients. A >50% decrease in the cortical peak (N20) amplitude of the median nerve evoked potential during the intraoperatory carotid occlusion is considered a reliable method of monitoring for detecting possible intraoperative cerebral ischemia and shunt utilizing. We reviewed retrospectively 599 consecutive CEAs performed with SEP monitoring and general anaesthesia between 1997 and 2005. One hundred eighty-four of them were considered symptomatic as they have recently suffered some relevant neurological symptom (minor stroke or TIA) in the carotid territory. Forty-five patients received a shunt because of a significant change (>50% decrease in N20 amplitude) after cross clamping in a one minute test preceding surgery (31 patients) or, during CEA (14 patients). All patients who received shunt showed a rapid complete recovery of potential and no neurological deficit at arousal. In other 24 patients shunting was pre-established or individually decided by the surgeon during surgery. Other 31 patients showed a significant (>50%) but slow decrease (>5 min) of N20 amplitude and shunt was not used. Eight of them had a transient neurological deficit (TIA or RIND). There were no mortalities and only four major strokes (0.66%) in the symptomatic patients group. We conclude that CEA can be safely performed with SEP monitoring and insertion of the shunt is recommended in every cases of >50% N20 amplitude reduction; the slowness of the potential amplitude reduction is not suggested as a negative predictor of central ischemia.
ters such as motor unit size (the number of muscle fibres), size of the innervation zone, and observation distance (the electrode to motor unit distance) has been discussed for long time. The effects mentioned cause a complex pattern if the signal is looked upon as a time-dependent event. With certain methods, such as the Fourier transform, this time pattern can be expressed as products in the frequency domain, with each factor separately describing one of the underlying physical phenomena. Methods: Using a well-established model describing the power spectrum of the myoelectric signal, we fitted experimental data on single motor unit potentials recorded with surface electrodes from the biceps muscle in 63 children of all ages. The unknown quantities ‘‘observation distance’’ and ‘‘number of motor unit fibres’’ were varied until the model’s output fitted experimental data. Results: The results show that the observation distances ranged from 1 to 12 mm as expected from ultrasound scanning on the children’s upper arms. The numbers of fibres of the motor units show a surprisingly large range: 15–1900. There was virtually no correlation between the distance and signal strength. However, when the strength was compensated for the number of single fibre sources contributing to the motor unit potential, an inverse proportionality emerged with very small deviations. Duration as function of distance was found to increase slightly from an initial value of about 6 ms (extrapolated value) close to the motor unit with an increasing slope for larger distances. Conclusions: With the method presented we can compensate for the influence of the observation distance on the surface EMG in order to obtain ‘‘true’’ measures of the potential. The method also gives us estimates of the number of fibres of the motor unit and of the propagation velocity of the potential. doi:10.1016/j.clinph.2006.06.024
FC7.2 Using high-density surface electromyography (HDsEMG) in detecting neuromuscular disorders in children J.P. van Dijk, D. Kusters, N. van Alfen, M.J. Zwarts, D.F. Stegeman, G. Drost Radboud University Medical Centre Nijmegen, Clinical Neurophysiology, Netherlands
doi:10.1016/j.clinph.2006.06.023
FC7.1 Influence of observation distance and motor unit size on the surface EMG J. Malmstrom, L. Lindstrom Queen Silvia Children’s Hospital, Sweden Background: The complicated interplay between surface derived myoelectric potential characteristics and parame-
Background: Needle EMG is a standard technique that is used in the diagnostic process of many neuromuscular diseases. Needle EMG is painful and cooperation of the patient is required. So, its use is limited especially in children. Aim: To develop a protocol that is suitable to measure multiple muscles in young children and to investigate which of the variables that can be derived from HD-sEMG are able to discriminate between healthy children and children with a neuromuscular disease.
Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
FC6.4 Somatosensory evoked potential monitoring during carotid endarterectomy F. Traverso 1, B. Peluffo 2, C. Bertoglio 3, A. Cristiani 3, C. Serrati 2 1 2 3
Sanremo Hospital, Neurology, Italy Imperia Hospital, Neurology, Italy Imperia Hospital, Vascular Surgery, Italy
Carotid endarterectomy (CEA) is a widely accepted treatment of carotid disease. Controversy still remains with regards to the optimal method to protect the brain from possible hemodynamic ischaemia during CEA: local or general anaesthesia, with or without shunt, EEG or somatosensory evoked potential (SEP) monitoring. Although the SEPs for CEA are widely used, the published studies are few and generally done on small cohorts of patients. A >50% decrease in the cortical peak (N20) amplitude of the median nerve evoked potential during the intraoperatory carotid occlusion is considered a reliable method of monitoring for detecting possible intraoperative cerebral ischemia and shunt utilizing. We reviewed retrospectively 599 consecutive CEAs performed with SEP monitoring and general anaesthesia between 1997 and 2005. One hundred eighty-four of them were considered symptomatic as they have recently suffered some relevant neurological symptom (minor stroke or TIA) in the carotid territory. Forty-five patients received a shunt because of a significant change (>50% decrease in N20 amplitude) after cross clamping in a one minute test preceding surgery (31 patients) or, during CEA (14 patients). All patients who received shunt showed a rapid complete recovery of potential and no neurological deficit at arousal. In other 24 patients shunting was pre-established or individually decided by the surgeon during surgery. Other 31 patients showed a significant (>50%) but slow decrease (>5 min) of N20 amplitude and shunt was not used. Eight of them had a transient neurological deficit (TIA or RIND). There were no mortalities and only four major strokes (0.66%) in the symptomatic patients group. We conclude that CEA can be safely performed with SEP monitoring and insertion of the shunt is recommended in every cases of >50% N20 amplitude reduction; the slowness of the potential amplitude reduction is not suggested as a negative predictor of central ischemia.
ters such as motor unit size (the number of muscle fibres), size of the innervation zone, and observation distance (the electrode to motor unit distance) has been discussed for long time. The effects mentioned cause a complex pattern if the signal is looked upon as a time-dependent event. With certain methods, such as the Fourier transform, this time pattern can be expressed as products in the frequency domain, with each factor separately describing one of the underlying physical phenomena. Methods: Using a well-established model describing the power spectrum of the myoelectric signal, we fitted experimental data on single motor unit potentials recorded with surface electrodes from the biceps muscle in 63 children of all ages. The unknown quantities ‘‘observation distance’’ and ‘‘number of motor unit fibres’’ were varied until the model’s output fitted experimental data. Results: The results show that the observation distances ranged from 1 to 12 mm as expected from ultrasound scanning on the children’s upper arms. The numbers of fibres of the motor units show a surprisingly large range: 15–1900. There was virtually no correlation between the distance and signal strength. However, when the strength was compensated for the number of single fibre sources contributing to the motor unit potential, an inverse proportionality emerged with very small deviations. Duration as function of distance was found to increase slightly from an initial value of about 6 ms (extrapolated value) close to the motor unit with an increasing slope for larger distances. Conclusions: With the method presented we can compensate for the influence of the observation distance on the surface EMG in order to obtain ‘‘true’’ measures of the potential. The method also gives us estimates of the number of fibres of the motor unit and of the propagation velocity of the potential. doi:10.1016/j.clinph.2006.06.024
FC7.2 Using high-density surface electromyography (HDsEMG) in detecting neuromuscular disorders in children J.P. van Dijk, D. Kusters, N. van Alfen, M.J. Zwarts, D.F. Stegeman, G. Drost Radboud University Medical Centre Nijmegen, Clinical Neurophysiology, Netherlands
doi:10.1016/j.clinph.2006.06.023
FC7.1 Influence of observation distance and motor unit size on the surface EMG J. Malmstrom, L. Lindstrom Queen Silvia Children’s Hospital, Sweden Background: The complicated interplay between surface derived myoelectric potential characteristics and parame-
Background: Needle EMG is a standard technique that is used in the diagnostic process of many neuromuscular diseases. Needle EMG is painful and cooperation of the patient is required. So, its use is limited especially in children. Aim: To develop a protocol that is suitable to measure multiple muscles in young children and to investigate which of the variables that can be derived from HD-sEMG are able to discriminate between healthy children and children with a neuromuscular disease.