Lumbar spinal stenosis: analysis of pre- and postoperative somatosensory evoked potentials

Cortical somatosensory evoked potential (CSEP) examinations were performed of 20 patients with lumbar spinal stenosis a day prior to surgery and 10 to 12 days after spinal decompression and bilateral lateral fusion. CSEPs were recorded to Cz-Fz (10-20 international EEG system) following stimulation of 32 tibial, peroneal and sural nerves and 16 saphenous nerves. A total of 110 nerves were examined. Using CSEP P1 latency as criteria for inclusion in the study, 21 tibial, 20 peroneal and 17 sural nerves were subjected to paired two-tailed t tests to determine whether the CSEP changes that occurred postoperatively were statistically significant (p less than 0.05). Postoperative P1 latencies of tibial, peroneal, and sural nerves changed significantly as well as N1 latencies and P1-N1 amplitudes of tibial and peroneal nerves. Nineteen patients improved clinically. It is postulated that pathologic narrowing of the spinal canal in spinal stenosis leads to nerve root compression and ischemia with resultant dysfunction primarily affecting large diameter myelinated fibers and that decompression procedure may adequately relieve the underlying pathologic processes. Improvement in CSEPs may be from increase in available numbers of functioning large diameter myelinated fibers, conversion to normal from a conduction block, and, perhaps, improved axoplasmic flow.     

Relationship between electroneurographic changes and serum ubiquitin levels in patients with type 2 diabetes

OBJECTIVE: The aim of the present study was to investigate any relationship between serum ubiquitin levels and electroneurographic changes in peripheral nerves for patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: The study involved 34 patients (19 men, 15 women; mean age 46 +/- 13 years) with type 2 diabetes. Serum ubiquitin values were measured by sandwich enzyme-linked immunosorbent assay Measurement of nerve conduction velocity (NCV) was performed on three motor (median, tibial, and peroneal) and three sensory (median, ulnar, and sural) nerves. The value of motor compound muscle action potential (CMAP) was obtained from the sum of median, tibial, and peroneal motor nerve amplitudes, and sensory compound nerve action potential (CNAP) was computed as the sum of median and ulnar sensory nerve amplitudes. RESULTS: Patients with diabetes were divided into three groups: group 1 (n = 8) had normal electroneurography results, group 2 (n = 8) had slowed NCV, and group 3 (n = 18) had low values of motor CMAP and/or sensory CNAP as well as slowed NCV. Mean ubiquitin level in group 3 (20.4 +/- 2.9 ng/dl) was significantly higher than that in group 1 (11.2 +/- 1.1 ng/dl, t = 11.5, P < 0.0001) and group 2 (13.2 +/- 2.7 ng/dl, t = 5.9, P < 0.0001). Serum ubiquitin levels were inversely correlated with motor CMAP (r = -0.68) and sensory CNAP (r = -0.61) values. CONCLUSIONS: The results of this study indicate that there could be a relationship between the diminished amplitudes of axons of the peripheral nerve and the increase in serum ubiquitin levels in patients with type 2 diabetes. Further studies are required to confirm this relationship.     

Quantification of intraoperative somatosensory evoked potential

Cortical (C) and spinal (S) somatosensory evoked potentials (SEP) were measured and quantified in 30 patients undergoing scoliosis surgery during the following periods: I, preincision; II, hypotension; III, instrumentation; IV, postinstrumentation; and V, skin closure. Paired two-tailed t tests were performed on all commonly measured SEP parameters comparing values obtained at periods I and II with each subsequent period. CSEP were obtained with Cz-Fz recording sites of the international 10-20 system while SSEP were obtained with recording electrodes at C7-Fz, following bilateral posterior tibial nerve stimulation at the ankles. From period I, CSEP P1 prolonged significantly across all periods but not from period II to subsequent periods. N1 remained stable from either period I or II until period V when latencies increased. P1-N1 amplitude decreased significantly between period I and other periods until period V when near base value was regained. Compared to period II however, P1-N1 amplitude did not differ significantly until period V when it increased beyond base. CSEP P2 and N2 latencies and amplitudes were less distinct and had high variability under our anesthetic technique which consisted of N2O-O2 and isoflurane 0.25%-0.50%, narcotics, nondepolarizing blocking agents, and induced hypotension. When attainable, they behaved in a similar pattern to the early CSEP. SSEP were obtained in 23 cases. The stability of latencies and amplitudes compared favorably with CSEP P1 and N1. Graphs of relative percent changes were developed for clinical use. It is concluded that the noninvasive monitoring technique described is practical, and that P1 and N1 CSEP and SSEP values are reliable monitoring parameters.     

Temporal effects of isometric contraction maneuvers on threshold sural amplitude

OBJECTIVE: To investigate the effect of isometric biceps brachii contraction and neck flexion on the time course of threshold sural amplitude. DESIGN: Twelve healthy subjects, who were asked to lie supine on an examination bench, performed 1 min of muscle contraction. The sural sensory nerve action potential was recorded before, immediately after, and at 2-min intervals after muscle contraction. The preexercise level of stimulus intensity remained unchanged for sural readings throughout the entire course of the experiment. RESULTS: The temporal changes in sensory nerve action potential amplitudes for both maneuvers were similar (P = 0.9734, two-way interaction). The mean sural amplitude after neck flexion increased from 6.0 +/- 2.9 microV (SD) to 10.6 +/- 6.6 microV (SD) 10 min after contraction. Similarly, mean sural amplitude increased from 6.5 +/- 1.8 microV (SD) to 14.5 +/- 9.7 microV (SD) 8 min after biceps brachii contraction. Statistical analysis performed using repeated measures with post hoc least significant difference showed a significant temporal effect in the two groups (P = 0.04). CONCLUSION: The temporal responses of threshold sural amplitudes after isometric biceps brachii contraction and central reinforcement neck flexion maneuvers are nearly identical with regard to increase in the amplitude.     

Physical activity: its influence on nerve conduction velocity

In a group of 40 healthy subjects, distal and proximal latencies of the median, tibial, and peroneal motor, and sural sensory nerves and their respective skin surface temperatures (Tsk) were measured before and after walking or bicycling. The baseline tests were performed 30 minutes after resting in a constant room temperature of 24C. The ambulation or bicycling task was continued for 30 minutes at a constant rate. Postactivity tests were performed within 30 minutes and between 45 to 60 minutes after termination of activity. Another test was done 75 to 90 minutes after bicycle exercise. After walking, there was a significant increase in Tsk in all lower extremity nerves tested (p less than 0.01). The increases were accompanied by faster distal and proximal latencies in both testing periods (p less than 0.01). Median nerve Tsk, distal and proximal latencies did not differ significantly from baseline values initially, but 45 minutes after walking Tsk was elevated and proximal latency had become faster (p less than 0.01). Following bicycling, lower extremity Tsk was significantly reduced over tibial, peroneal, and sural nerves by the third testing period (p less than 0.01) but only sural latencies were significantly prolonged (p less than 0.05) by this time. In the upper extremities median Tsk was significantly elevated and distal latency had become significantly faster 45 minutes after bicycling. Our data suggest that activity significantly influences nerve conduction latency results due to tissue temperature alteration. In addition, 30 minutes of rest after activity may not be sufficient time for the lower extremity temperatures to become stable.     

Sural and saphenous 14-cm antidromic sensory nerve conduction studies

OBJECTIVE: To create a large database of normal values for the sural and saphenous nerve conduction studies and to compare the results for the two nerves. DESIGN: Using a 14-cm antidromic technique, data were collected for onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, duration, side-to-side variability, and between-nerve variability. A total of 230 subjects were included in the study. RESULTS: For the sural nerve, the upper limits of normal, defined as the 97th percentile of observed values, for onset latency, peak latency, and duration were 3.6, 4.5, and 2.1 msec, respectively. The comparable values for the saphenous nerve were 3.8, 4.4, and 1.9 msec, respectively. The lower limits of normal (third percentile) for sural onset-to-peak amplitude and peak-to-peak amplitude were 4 and 4 microV. The comparable values for the saphenous study were 2 and 1 microV. The upper limit of normal difference in onset latency between the two nerves was: saphenous 0.7 msec longer than sural or sural 0.3 msec longer than saphenous. The corresponding values for peak latency were: 0.6 and 0.5 msec. CONCLUSION: Normal ranges are presented for a large database of subjects for the sural and saphenous nerve conduction studies.     

Sensory nerve evoked responses in spinal cord injury

Previous studies have documented the presence of fibrillations, positive waves, and decreased motor evoked response amplitudes in spinal cord injury (SCI) subjects. The purpose of this study was to further evaluate sensory nerve status in this population. Twenty-eight subjects with SCI for at least five months and evidence of spasticity were included. Sural sensory and tibial motor evoked response amplitudes were measured. The mean sural sensory amplitude was 8.0 +/- 5.9 microV (normal = 15.0 +/- 5.3 microV). The mean tibial motor amplitude was 5.1 +/- 4.3 mV (normal = 11.7 +/- 3.8 mV). In six subjects with significantly reduced sural sensory amplitudes, more extensive electrodiagnostic testing was performed. These studies showed diffusely decreased lower extremity sensory and motor evoked response amplitudes and diffuse positive waves and fibrillations in no particular distribution. Thus, subjects with SCI may have sensory as well as motor nerve abnormalities. An intact connection between the second order and primary sensory neuron may be necessary for maintenance of axonal integrity of the primary neuron.     

Electrodiagnostic changes of the lower limbs in subjects with chronic complete cervical spinal cord injury

OBJECTIVE: To assess the electrodiagnostic changes in the lower limbs as measured by nerve conduction studies (NCSs) and electromyography in individuals with chronic complete tetraplegia. DESIGN: Prospective testing of NCS and electromyography. SETTING: Model spinal cord injury rehabilitation center. PARTICIPANTS: Twenty-five individuals with chronic complete tetraplegia without risk factors for peripheral neuropathy or other lower motoneuron disorders. INTERVENTIONS: Nerve conduction parameters recorded from the peroneal, tibial, and sural nerves, and compared with normal values. The presence of spontaneous activity (SA), including fibrillation and positive sharp waves, recorded in 5 muscle groups-2 proximal (vastus medialis, iliopsoas), 2 distal (tibialis anterior, medial gastrocnemius), and L4 lumbar paraspinals. Analysis to see if the presence of SA correlated with the distance of the muscle from the spinal cord or with spasticity (measured by the modified Ashworth scale). MAIN OUTCOME MEASURES: Nerve conduction latencies and velocities; motor and sensory conduction latencies; compound muscle action potential (CMAP) and sensory nerve action potential amplitudes; spontaneous potentials: fibrillation and positive sharp waves; and spasticity. RESULTS: NCS responses were obtained at a decreased frequency relative to able-bodied subjects. Statistically significant results in comparison to normal means included a diminished sural amplitude, and diminished peroneal and tibial CMAP and nerve conduction velocity (p <.0001). SA was recorded in at least 1 of the muscles tested in 92% of subjects, with 72% having SA in more than 1 of the muscles tested affected. A significant difference was seen for SA in the medial gastrocnemius as compared with the iliopsoas (p =.039). No correlation was noted in terms of SA with degree of spasticity. CONCLUSION: A statistically significant difference in NCS responses in the lower limbs in chronic tetraplegia was found relative to normal control values. However, only the frequency of responses elicited and the decreased CMAP of the peroneal nerve are clinically significant. SA was present in many of the lower extremity muscles in the subjects. Predominantly axonal changes were evident in individuals with chronic complete tetraplegia.     

Impairment of trigeminal sensory pathways in cluster headache

Cluster headache (CH) typically presents in clusters of attacks of intense (peri)orbital, unilateral pain. The distribution of the pain implies involvement of central and/or peripheral trigeminal pathways. These can be investigated by means of trigeminal somatosensory evoked potentials (TSEP) and blink reflexes (BR). We aimed to relate functional changes in trigeminal sensory pathways to the presence of cluster periods. TSEP and BR were performed in 28 episodic CH patients during a cluster period and repeated in 22 outside a cluster period. TSEP latencies (N1, P1 and N2) and amplitude (N1-P1 and P1-N2) and BR latencies (R1, R2 ipsilateral and R2 contralateral) were compared between sides, during and outside a cluster period and with healthy control data (n = 22). During a cluster period, N2 TSEP latencies were longer on the symptomatic side compared with the non-symptomatic side (27.2 +/- 3.0 ms vs. 26.3 +/- 3.4 ms, P = 0.02), and compared with the same side outside the cluster period (26.7 +/- 3.1 ms vs. 25.1 +/- 3.0 ms, P = 0.01). N1, P1 and N2 latencies on the symptomatic side in patients during the cluster period (14.8 +/- 2.3 ms, 20.4 +/- 2.5 ms and 27.2 +/- 3.0 ms, respectively) were significantly longer than those of healthy controls (13.4 +/- 1.9 ms, 18.8 +/- 2.4 ms and 25.0 +/- 2.6 ms, respectively, P < 0.03). Outside the cluster period, N1 latencies of both sides (15.3 +/- 2.8 ms symptomatic side and 15.4 +/- 2.6 ms asymptomatic side) were longer compared with controls (13.4 +/- 1.9 ms, P < 0.04). TSEP amplitudes and BR latencies revealed no significant differences. We conclude that abnormalities of the afferent trigeminal pathway are present in patients with cluster headache, most prominent during the cluster period, and on the symptomatic side. This seems primarily due of changes within the higher cerebral regions of the system.     

Contraction-induced upper extremity H reflexes: normative values.

OBJECTIVES: To determine the reliability of contraction-induced upper extremity H reflexes; to calculate normal values for latency, amplitude, and side-to-side variation; and to correlate latency to arm length. DESIGN: Case series. SETTING: Electrophysiology laboratory of a tertiary care center. PARTICIPANTS: Twenty-three healthy volunteers (4 men, 19 women), aged 19 to 42. INTERVENTION: Volunteers were tested bilaterally for H reflexes in four to six upper extremity muscles during an isometric contraction. MAIN OUTCOME MEASURES: H reflex onset latency, onset to negative peak amplitude, side-to-side variation, normal ranges, and latency versus arm-length correlation. RESULTS: H reflexes were found at all 264 sites tested. Mean latencies varied from 9.5 to 27 msec. Maximum normal side-to-side variation was 1.5 to 2.7 msec. Maximum normal amplitude ratios (larger to smaller) ranged from 2.06 to 4.80. Abductor pollicis brevis (APB) and abductor digiti minimi (ADM) H reflex latencies were strongly correlated to arm length. Correlation for APB = .64 (p<.0001) and for ADM = .70 (p<.0001). CONCLUSIONS: Contraction-induced upper extremity H reflexes occur consistently in healthy adults, with latencies, amplitudes, and side-to-side variation occurring in predictable ranges.     

两种手术体位安置对阴式子宫全切患者循环功能和腓总神经损伤的观察

目的探讨两种体位摆放对阴式子宫全切除患者循环功能和腓总神经损伤的影响。方法选择妇科阴式子宫全切除术患者76例,按手术顺序分成观察组和对照组各38例。对照组患者采用截石位;观察组患者采取平卧位,双下肢水平分开100-110°。术中监测心率、无创血压,术后了解下肢腓总神经损伤情况。结果对照组术中血压、心率波动较观察组明显,术后下肢疼痛、麻木等不良反应显著高于观察组（P〈0.05）。结论阴式子宫全切除术采用平卧位,双下肢水平分开,可稳定和改善患者循环功能,减少下肢腓总神经损伤,提高了手术的安全性。     

An electrodiagnostic study in chronic alcoholic subjects

Electrodiagnostic tests were performed on 16 alcoholic subjects and 15 age-matched controls. The tests were done to determine whether nerve conduction parameters differentiate between healthy and alcoholic subjects, and if so, which of these are most useful. Significant differences between alcoholic subjects and controls were found in the following variables: median nerve motor velocity; median nerve sensory latency, amplitude and velocity; ulnar nerve motor amplitude and velocity; ulnar nerve sensory amplitude, latency and velocity; sural nerve sensory amplitude and velocity; and peroneal motor amplitude and velocity. The combination of ulnar and sural sensory conduction velocity tests identified 85% of the chronic alcoholic subjects by stepwise discriminant analysis. Tibial nerve H-reflex latencies were either absent or prolonged in 63% of the subjects. Bilateral facial nerve amplitudes and latencies were normal. The ulnar sensory amplitude and ulnar sensory velocity inversely correlated with the duration of excessive alcohol drinking.     

Influence of posture and muscle length on stretch reflex activity in poststroke patients with spasticity

OBJECTIVE: To investigate the influence of different positions on stretch reflex activity of knee flexors and extensors measured by electromyography in poststroke patients with spasticity and its expression in the Ashworth Scale. DESIGN: Crossover trial with randomized order of positioning. SETTING: Outpatient rehabilitation center in the Netherlands. PARTICIPANTS: Poststroke patients (N = 19) with lower-limb spasticity. INTERVENTION: Changing position: sitting versus supine. MAIN OUTCOME MEASURES: Root mean square (RMS) values of muscle activity and goniometric parameters, obtained during the pendulum test and passive knee flexion and extension, and Ashworth scores. RESULTS: RMS values of bursts of rectus femoris activity were significantly higher in the supine compared with the sitting position (P = .006). The first burst of vastus lateralis activity during the pendulum test (P = .049) and semitendinous activity during passive stretch (P = .017) were both significantly higher in the supine versus the sitting position. For both the pendulum test and passive movement test, the duration and amplitude of the cyclic movement of the lower leg changed significantly as well. In the supine position, we found significantly higher Ashworth scores for the extensors (P = .001) and lower scores for the flexors (P = .002). CONCLUSIONS: The outcome of clinical and neurophysiologic assessment of spasticity is influenced considerably by subject positioning.     

Physiological responses to the early mobilisation of the intubated, ventilated abdominal surgery patient

The aim of this study was to investigate the effects of mobilisation on respiratory and haemodynamic variables in the intubated, ventilated abdominal surgical patient. Mobilisation was defined as the progression of activity from supine, to sitting over the edge of the bed, standing, walking on the spot for one minute, sitting out of bed initially, and sitting out of bed for 20 minutes. Seventeen patients with age (mean +/- SD) 71.4 +/- 7.1 years satisfied inclusion criteria. Respiratory and haemodynamic parameters were measured in each of the above positions and compared with supine. In the 15 subjects who completed the protocol, standing resulted in significant increases in minute ventilation (VE) from 15.1 +/- 3.1 l/min in supine to 21.3 +/- 3.6 l/min in standing (p < 0.001). The increase in VE in standing was achieved by significant increases in tidal volume (VT) from 712.7 +/- 172.8 ml to 883.4 +/- 196.3 ml (p = 0.008) and in respiratory rate (fR) from 21.4 +/- 5.0 breaths/min to 24.9 +/- 4.5 breaths/min (p = 0.03). No further increases were observed in these parameters beyond standing when activity was progressed to walking on the spot for one minute. When supine values were compared with walking on the spot for one minute, inspiratory flow rates (VT/TI) increased significantly from 683 +/- 131.8 ml/sec to 985.1 +/- 162.3 ml/sec (p = 0.001) with significant increases in rib cage displacement (p = 0.001) and no significant increase in abdominal displacement (p = 0.23). Arterial blood gases displayed no improvements following mobilisation. Changes in VT, fR, and VE were largely due to positional changes when moving from supine to standing.     

Race effect on nerve conduction studies: a comparison between 50 blacks and 50 whites.

OBJECTIVE: To determine whether there are any differences in nerve conduction study results between blacks and whites. DESIGN: The following studies were performed: median, ulnar, peroneal, and tibial motor studies; median and ulnar mixed motor/sensory studies; sural and radial sensory studies; and H-reflex studies. SETTING: Private office or university-based clinic. PARTICIPANTS: Fifty adult blacks and 50 adult whites who met inclusion criteria, recruited through advertisements. MAIN OUTCOME MEASURES: Differences between blacks and whites were compared to determine whether they exceeded a cutoff of 0.2 msec for latencies, 20% difference for amplitudes, 5 m/sec for conduction velocity, and 1.2 msec for H-reflex times. A repeated analysis of variance was performed to detect statistically significant differences (defined as p< or =.01). RESULTS: Only values for the mean peroneal and tibial motor latencies exceeded the cutoff times. The mean peroneal response was faster by 0.3 msec and the mean tibial response was slower by 0.3 msec in blacks than whites. These differences were not statistically significant at a level of p< or =.01. CONCLUSION: There is no significant difference between blacks and whites in normal nerve conduction study findings in healthy adults.     

Sural nerve conduction: a standardized technique.

Occasionally patients with symptoms and signs suggestive of mild peripheral neuropathy, after routine nerve conduction and electromyographic studies, are found to have values within normal limits. Several authors have suggested that sural nerve conduction studies might be more sensitive indicators of mild peripheral neuropathy. Normal values for sural nerve latencies, amplitudes and conduction velocities have been reported; however, the techniques used have not generally been rigidly standardized. This study describes a standardized and reproducible method of performing human sural nerve conduction studies and presents values obtained from systematically studying a series of 56 normal volunteers.     

Early detection of microcirculatory impairment in diabetic patients with foot at risk

OBJECTIVE: To assess microcirculatory impairment and alterations of the skin oxygen supply in diabetic patients with foot at risk. RESEARCH DESIGN AND METHODS: This study evaluated skin blood flow in 21 type 2 diabetic patients with a foot at risk (defined as a foot with neuropathy but without ulceration or previous ulcerations), 20 type 2 diabetic patients without foot lesions or neuropathy, and 21 normal subjects as a control group. The skin blood flow was determined by measuring the transcutaneous oxygen pressure (TcPO(2)) at the dorsum of the foot in supine and sitting position. The clinical assessment included standard measures of peripheral and autonomic neuropathy, but peripheral vascular disease was excluded by Doppler ultrasound. RESULTS: In supine position, TcPO(2) was significantly reduced (means +/- SE) in diabetic patients with foot at risk (6.04 +/- 0.52 kPa) compared with diabetic (7.14 +/- 0.43 kPa, P = 0.035) and nondiabetic (8.10 +/- 0.44 kPa, P = 0.01) control subjects. The sitting/supine TcPO(2) difference was higher in diabetic subjects with foot at risk (3.13 +/- 0.27 kPa) compared with both diabetic (2.00 +/- 0.18, P = 0.004) and nondiabetic (1.77 +/- 0.15 kPa, P = 0.0003) control subjects. The mean sitting/supine ratio was 1.70 +/- 0.12 in diabetic patients with foot at risk, 1.32 +/- 0.04 in diabetic control subjects, and 1.25 +/- 0.03 in nondiabetic control subjects (P = 0.007). The sitting/supine TcPO(2) ratio was negatively correlated with the heart rate variation coefficient at rest (r = -0.32, P = 0.044) and at deep respiration (r = -0.31, P = 0.046). CONCLUSIONS: Our data indicate that skin oxygen supply is reduced in type 2 diabetic patients with foot at risk. This is probably due to an impaired neurogenic blood flow regulation and may contribute to capillary hypertension, followed by disturbed endothelial function leading to edema and skin damage of the foot. The determination of TcPO(2) appears to be a useful tool in screening type 2 diabetic patients for foot at risk.     

Trigeminocervical reflex in fibromyalgia patients

OBJECTIVE: To describe the properties of trigeminocervical reflex in normal subjects and in patients with primary fibromyalgia syndrome (PFS) having neck pain. DESIGN: Prospective testing of trigeminocervical reflex. SETTING: University hospital electromyography laboratory in Turkey. PARTICIPANTS: Patients with PFS (n=16) and healthy volunteers (n=20). INTERVENTIONS: Trigeminocervical reflex is a brainstem reflex that is evoked by stimulating the sensory branches of the trigeminal nerve and can be recorded from the neck muscles. Electric stimulation of the supraorbital nerve evokes a reflex response (C3) and early reflex response (C1). The mean latencies of C1 and C3 of patients with PFS were compared with normal values.Main Outcome Measure: The C1 and C3 latencies of trigeminocervical reflex. RESULTS: In healthy volunteers, C3 latency +/- standard deviation was 54.17+/-6.00ms ipsilaterally and 51.25+/-9.26ms contralaterally. The difference was not significant (P=.26). The C1 latency was 17.46+/-4.89ms. In patients with PFS, C1 latency was 13.83+/-4.48ms and the C3 latency was 62.70+/-18.22ms. The difference was not significant between the patients (P=.08) and healthy volunteers (P=.17). CONCLUSION: In patients with PFS having neck pain, trigeminocervical connections were not influenced and some other mechanisms may be responsible for pain in these patients.