Somatosensory evoked potentials in patients with cervical spondylotic myelopathy

Somatosensory evoked potentials (SEPs) to posterior tibial nerve (PTN) and median nerve (MN) stimulations were recorded in 30 patients with cervical spondylotic myelopathy. Measurements performed include N20-P2 interpeak latency (IPL) for PTN-SEPs, EP-N13 IPL and EP-N20 IPL for MN-SEPs. Limits of normal IPL were defined by the mean + 3S.D. of the normal control group. PTN-SEPs was more sensitive (with 73.3% abnormal) than MN-SEPs (with 33.3% abnormal) and strongly correlated with the clinical signs of posterior column, but not with those of anterolateral column indicated by superficial sensory disturbances and spasticity of lower limbs. Severities of cord compression (sagital diameter/transverse diameter ratio) calculated from the picture of metrizamide CT were not correlated with SEPs findings and clinical signs. In patients with cervical myelopathy, SEPs, especially PTN-SEPs, were thought to be very useful examination.     

Somatosensory evoked potentials after multisegmental lower limb stimulation in focal lesions of the lumbosacral spinal cord

OBJECTIVES: Recording techniques permit the separate analysis of the response from cauda equina roots and the spinal potential that is probably generated by the activation of dorsal horn cells. To improve the functional assessment of focal lesions of the lumbosacral cord, lower limb somatosensory evoked potentials (SEPs) were measured by multisegmental stimulation. METHODS: Common peroneal and tibial nerves SEPs were recorded in 14 patients in whom MRI demonstrated compressive cord damage ranging from T9 to L1 levels. SEPs were recorded in each patient at the lumbar level (cauda equina response), lower thoracic level (spinal response), and from the scalp (cortical response). RESULTS: Abnormalities in spinal response occurred in 50% and 70% of tibial and common peroneal nerve SEPs respectively; these findings were well explained by the radiological compression level, involving in most of the patients lumbar rather than sacral myelomeres. The SEPs were often more effective than the clinical examination in showing the actual extension of damage. CONCLUSIONS: The recording of spinal SEPs after multisegmental lower limb stimulation proved useful in assessing cord dysfunction and determining the cord levels mainly involved by the compression.     

Motor evoked potentials in the post-surgical follow-up of cervical spondylotic myelopathy

Eighteen patients (6 female, 12 male; average age 51 years, range 37–79) with clinical and radiological evidence (MRI) of cervical spondylotic myelopathy (CSM) were examined. The subjects were divided into two groups depending on whether radiology indicated single level (9 patients) or multilevel (9 patients) compression of the cervical cord. All of the patients underwent surgical decompression. Seriate exam with trans-cranial magnetic stimulation was performed in double session before surgery, and 3 and 12 months after surgery. The follow-up study of these patients revealed a statistically significant neurophysiological improvement only in those patients with single-level compression. In these cases, the cervical cord pathology revealed by MRI signal hyperintensity in T2 may at least partially consist of an edematous component and/or an initial demyelinization that has still a chance of recovery. In patients with multilevel damage, the compression may cause irreversible lesions.

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Sommario Sono stati esaminati 18 pazienti (6 femmine, 12 maschi), età media 51 anni (range 37–79), con evidenza clinica e radiologica (RMN) di mielopatia spondilosica cervicale (CSM). Essi sono stati suddivisi in due gruppi in base al dato radiologico di compressione midollare monofocale (9 pazienti) o multifocale (9 soggetti). Tutti i pazienti sono stati sottoposti ad intervento chirurgico decompressivo. È stato effettuato esame seriato con stimolazione magnetica a livello cranico nel preoperatorio in due distinte sedute (al fine di valutare l'effetto sui dati della variabilità legata alla metodica), a 3 e 12 mesi dopo l'intervento. I risultati ottenuti sono stati paragonati con i valori normali relativi a 20 soggetti normali.Le alterazioni dei parametri neurofisiologici considerati (Tempo di conduzione centrale, ampiezza delle risposte evocate), più evidenti a carico delle vie destinate agli arti inferiori, non sono risultate di entità statisticamente differente nel gruppo dei soggetti con lesione mono e multifocale. Lo studio del follow up di questi pazienti ha rivelato un miglioramento statisticamente significativo sul piano neurofisiologico solo nei pazienti con compressione monofocale. Si può ipotizzare che in caso di compressione monofocale, la sofferenza midollare evidenziata alla NMR come iperintensità di segnale in T2, possa essere costituita, almeno in parte, da una componente edematosa e/o una iniziale demielinizzazione, ancora suscettibile di miglioramento. Nei pazienti con danno di tipo multifocale invece la compressione a più livelli più frequentemente dà luogo ad un danno di tipo ischemico che rende impossibile il recupero.

     

Superior sensitivity of motor over somatosensory evoked potentials in the diagnosis of cervical spondylotic myelopathy

Myelopathy secondary to cervical spondylosis is often a difficult clinical diagnosis. Furthermore, with the introduction of magnetic resonance imaging (MRI) an increasing number of patients are identified with spondylotic cervical spinal cord compression. We analyzed the value of functional assessment of the spinal cord by motor and sensory evoked potentials (MEP and SEP) in the detection of myelopathy, with special emphasis on the correlation of clinical and electrophysiological findings. Fifty-one patients with at least some degree of spinal cord compression because of cervical spondylosis, as shown by MRI, were included in the study, grouped according to clinical symptoms. We found that patients who had no clinical symptoms whatsoever indicating myelopathy (they were referred to MRI examination mostly because of cervical radiculopathy), had in the large majority normal MEP and SEP findings. Patients with slight, unspecific and non-confirmative symptoms without pyramidal signs had mostly abnormal MEP but normal SEP findings. This points to the superior sensitivity of MEP over SEP in detecting myelopathy in its early stages. Patients with obvious clinical signs of myelopathy, including pyramidal signs had both abnormal MEP and SEP findings. Altogether these findings may help clinicians in interpreting MRI signs of cervical spinal cord compression.     

Somatosensory and spinal evoked potentials in patients with upper cervical neurinoma.

Scalp somatosensory evoked potentials (SEPs) and spinal evoked potentials (SpEP) were simultaneously recorded from the exposed surface of the upper cervical cord after median nerve stimulation in five patients undergoing surgery for upper cervical neurinomas. Two of the neurinomas were localized at C1 nerve root, two at C2, and one at C3. All patients showed good postsurgical recovery, suggesting that the tumors had not progressed to the stage where most of the nerve fibers were irreparably damaged. In patients with unaffected superficial and deep skin sensation, both SEP and SpEP were normal. In patients with more advanced tumor, the superficial sensation was abnormal but the deep skin sensation was intact. In these patients, the action potential propagation slowed down but continued partially through the tumor site on the relatively less affected side contralateral to the tumor; however, it stopped at the site of the tumor on the ipsilateral side. It is possible that full functional recovery becomes more difficult during the next stage of tumor development when the propagation of action potentials ceases bilaterally. The intraoperative monitoring of both SEP and SpEP thus appears useful for inferring details of functional integrity and prognosis of the spinal cord near a space-occupying tumor during the critical first two stages of neoplasm in which the spinal function is normal, or a sufficiently large fraction of ascending and descending nerve fibers are functionally suppressed, but are capable of recovery after a surgical intervention.     

Somatosensory evoked potentials after stimulation of digital nerves in upper limbs: normative data

Normative data for somatosensory evoked potentials (SEPs) after stimulation of digital nerves from the first, third and fifth digits, which reach the spinal cord through C6, C7 and C8 roots are presented in 20 normal adults. SEP peak latencies and amplitudes are indicated for Erb's point, the level of the seventh and second cervical vertebrae and contralateral cortical hand area.     

Somatosensory evoked potentials reflect the upper limb motor performance in multiple sclerosis

OBJECTIVE: The aim of this multicentric study was to multidimensionally evaluate the relationship among somatosensory evoked potentials (SEPs) parameters, patient's perspective and clinical measures of the upper limb impairment in patients with multiple sclerosis (MS). METHODS: We consecutively enrolled 39 MS patients. For median nerve SEPs we acquired the N9, P14, N20 responses and the N9-P14 and P14-N20 interpeak latencies on the dominant side. We also used a validated patient-oriented questionnaire (Disabilities of the Arm, Shoulder and Hand - DASH) and a test of dexterity quantification as the 9-Hole Peg Test (9-HPT). RESULTS: A significant longer time to complete the 9-HPT (p<0.00006) was observed in patients with abnormal SEPs. Patients with undetectable N20 or P14 responses performed the 9-HPT in a significant longer time than patients with detectable responses (p<0.0006 and p<0.001 respectively). Concerning the perspective of patient (evaluated with the DASH questionnaire) significant differences in patients with undetectable P14 response (p<0.01) were observed. CONCLUSIONS: Our data provide further information useful for interpretation of SEPs results, being the median nerve SEPs related to the upper limb performance in MS patients. SIGNIFICANCE: These data increase the significance of SEPs both in clinical practice and in experimental studies in MS.     

Somatosensory evoked potentials following stimulation of the lower limb in cortical reflex myoclonus.

Generating mechanisms of giant somatosensory evoked potentials (SEPs) following stimulation of the posterior tibial nerve as well as the big toe were investigated in three patients with cortical reflex myoclonus. Scalp distributions of recognisable components were very similar to those in normal subjects, except that their amplitude was much larger. The tibial nerve SEPs were remarkably attenuated by interfering tactile stimulation. Therefore, the giant SEPs observed in the present cases seem to be, at least partially, due to input from cutaneous nerve fibres on the background of extremely enhanced excitability in area 3b of the primary sensory cortex where normal SEPs are generated.     

Somatosensory evoked response evaluation of cervical spondylytic myelopathy

There were 13 patients with cervical spondylytic myelopathy (CSM) evaluated. All had extradural defects with distortion of the cervical cord and partial or complete obstruction of myelographic dye. Posterior tibial scalp (SSEPs) were absent or delayed in all 13, whereas median SSEPs were abnormal in 9. Median SSEP abnormalties were limited to those with cord lesions at C5-C6 or above. There were eight patients with associated radiculopathies confirmed by electromyography. No meaningful differences in SSEPs were noted between those with or without root injury. Surgery confirmed the level of cord injury in 10. CSM is common with a high morbidity. The results indicate SSEPs using leg stimulation can be a sensitive indicator of cord injury in these patients and that the more commonly used arm stimulation is of value primarily for localizing the level of the myelopathy.     

Somatosensory evoked potentials after median and tibial nerve stimulation in healthy newborns.

Cortical and spinal somatosensory evoked potentials (SEPs) have been recorded after median and tibial nerve stimulation in healthy newborns. Spinal SEPs were readily obtained and recorded in all but one neonates after stimulation of both nerves. Cortical SEPs were more frequently recorded after median nerve (87%) than after tibial nerve stimulation (73%) but the shape of cortical SEPs obtained after tibial nerve stimulation was less variable. The mean feature of cortical SEPs was a negative wave (N27) for median nerve and a positive wave (P32) for tibial nerve. The present results demonstrate the feasibility of obtaining in the same baby, spinal and cortical SEPs after stimulation of median and tibial nerve, giving information on the functional integrity of central and peripheral somatosensory pathways which supply upper and lower limbs.     

Functional evaluation using several evoked spinal cord potentials in elderly patients with cervical spondylotic myelopathy

INTRODUCTION In elderly patients who have cervical spondylotic myelopathy (CSM), magnetic resonance imaging (MRI) frequently demonstrates multiple intervertebral level compressions of the cervical spinal cord. However, it should be taken into account that…     

多种脊髓诱发电位测评高龄脊髓型颈椎病患者颈脊髓机能

目的调查高龄脊髓型颈椎病患者的颈脊髓机能状态,并结合磁共振影像学（MRI）及X线放射学探讨其病理生理形成机制.方法对23例MRI显示为多椎间脊髓压迫的高龄脊髓型颈椎病患者,采用经颅电刺激-脊髓硬膜外记录、经脊髓硬膜外刺激-脊髓硬膜外记录、经正中神经刺激-脊髓硬膜外记录的三种脊髓诱发电位进行颈脊髓机能测定.结果17例患者（73.9%）显示为颈脊髓单一椎间的障碍,其中10例位于C3-4、5例位于C4-5、2例位于C5-6.另外6例患者（26.1%）的正中神经刺激-脊髓硬膜外记录结果表现为多个或两个椎间的障碍.结论在MRI影像学上显示为多椎间脊髓压迫的高龄脊髓型颈椎病患者,其多数在脊髓电生理上：表现为单一颈椎椎间的脊髓白质损伤,特征是不仅脊髓后索的感觉传导束,而且侧索的皮质脊髓束也受到损伤.结合X线放射学结果分析,C3-4或C4-5颈椎椎间的过大活动度或不稳是导致高龄脊髓型颈椎病患者脊髓传导束损伤的一个重要原因.     

Distribution of brainstem somatosensory evoked potentials following upper and lower limb stimulation.

OBJECTIVE: Because somatosensory evoked potentials (SEP) to lower limb stimulation have not been recorded from the brainstem to the extent that upper limb SEPs have been studied, we compared brainstem recordings in response to both median nerve (MN) and posterior tibial nerve (PTN)stimulation. METHODS: SEPs were recorded directly from the dorsal surface of the brainstem in four patients with fourth ventricle tumors. RESULTS: Following MN stimulation, medullary SEPs were characterized by a major negativity (N1) preceded by a small positivity (P1) and followed by a large positivity (P2). In the pons, triphasic waves with predominant negativity were obtained. With PTN stimulation, similar medullary SEPs with a P1'-N1'-P2' configuration and pontine SEPs with a triphasic waveform were obtained. CONCLUSIONS: Since the distribution of PTN SEP was identical to that of MN SEP, PTN SEPs are thought to be generated by mechanisms similar to those for MN SEP. Thus, the P1' and N1' of medullary SEP would be generated by the dorsal column fibers that terminate in the nucleus, with P2' possibly arising postsynaptically in the nucleus. The triphasic PTN SEP from the pons reflects an axonal potential generated in the medial lemniscal pathway.     

Somatosensory evoked potentials after posterior tibial nerve stimulation in focal spinal cord diseases.

We investigated the somatosensory evoked potentials (SEPs) produced by posterior tibial nerve (PTN) stimulation in 8 infants and children with focal spinal cord disorders. The spinal responses of the PTN-SEPs were considered to assist in the localization of spinal lesions because their abnormalities were consistent with the neurologic and/or radiologic findings in all 6 examinations that revealed abnormal spinal SEPs. The cortical responses correlated significantly with proprioception in the lower limbs because proprioception was only disturbed when the cortical SEPs were absent (3 examinations). When both the spinal and cortical responses were abnormal, the spinal lesion probably involved the dorsal column so extensively that it completely interrupted the afferent impulses. In contrast, when SEP studies demonstrated abnormal spinal and normal cortical SEPs (3 examinations), the dorsal column involvement was probably less severe; therefore, both the spinal and cortical responses provided useful information regarding afferent conduction in the dorsal column. PTN-SEPs appear to have the potential to be of value in the diagnosis of focal spinal disease, especially in infants and young children who cannot cooperate with detailed neurologic examinations.     

Somatosensory evoked potentials by paraspinal stimulation in acute transverse myelitis.

Somatosensory evoked potentials by paraspinal stimulation were studied in 6 patients with acute transverse myelitis. In one patient in whom posterior tibial somatosensory evoked potentials were not recordable, a poorly formed response was seen with paraspinal stimulation. Slowing of conduction across the involved segment was seen in the remaining 5 patients and fairly correlated with the clinical localization.     

Somatosensory evoked potentials from cervical and lumbosacral dermatomes

A method for recording the somatosensory evoked potentials after stimulation of the cervical and lumbosacral dermatomes is described. Normative values and their ranges are given for each dermatome including left-right differences. A significant correlation was found between latencies and conduction distance. Dermatomal SEPs may play a role in diagnosing cervical and lumbosacral radiculopathies.