Neuronal activity in primary motor cortex differs when monkeys perform somatosensory and visually guided wrist movements

This study was designed to investigate how activity patterns of primary motor cortical (MI) neurons change when monkeys perform the same movements guided by somatosensory and/or visual cues. Two adult male rhesus monkeys were trained to make wrist extensions and flexions after holding a steady position during an instructed delay period lasting 0.5-2.0 s. Monkeys held against a 0.07 Nm load that opposed flexion movements. Wrist movements were guided by vibratory cues (VIB-trials), visual cues (VIS-trials), or both in combination (COM-trials). Extracellular recordings of 188 MI neurons were made during all three paradigms. Individual neurons were counted twice, once for each movement direction, yielding 376 cases. All neurons had significant task-related activity (TRA) changes relative to delay period activity during at least one of the three paradigms. TRA was analyzed to determine if it was different as a function of the sensory cue(s) that initiated movement and that specified movement endpoints. Cases were grouped by whether the TRA changes were greater in VIB- or VIS-trials; this defined their "bias". One hundred and eighteen cases (31.4%) had greater TRA changes in VIB-trials (Vb-neurons), whereas 185 (49.2%) showed greater TRA changes in VIS-trials (Vs-neurons). The remaining 73 cases (19.4%) had similar TRA changes in VIB- and VIS-trials (Nb-neurons). For Vb- and Vs-neurons, earlier TRA onsets and greater TRA changes were observed in the trials for which these neurons were biased. During the COM-trials, the TRA was intermediate. During the trials for which the activity was not biased, the TRA was the least. For Nb-neurons, no significant TRA differences were observed across paradigms. TRA changes of MI neurons may represent movement planning-related inputs from other central, presumably cortical, sources as well as contribute to motor outflow from the cortex. These data suggest that Vb- and Vs-neurons are affected differently by somatosensory- and visually related central inputs, resulting in different TRAs, even for essentially identical movements. Such differences may depend not only on the type of sensory information that initiates movement but also whether that information specifies movement endpoints or might interfere with movement monitoring.

Principal component analysis of complex multijoint coordinative movements

Principal components analysis (PCA) has not been very much in vogue within the field of movement coordination even though it is useful to reduce data dimensionality and to reveal underlying data structures. Traditionally, studies of coordination between two joints have predominantly made use of relative phase analyses. This has resulted in the identification of principal constraints that govern the Central Nervous System's organization and the control of coordination patterns. However, relative phase analyses on pairwise joints have some drawbacks because they are not optimal for revealing convergent patterns among multijoint coordination modes and for unraveling generic control strategies. In this paper, we present a method to analyze multijoint coordination based on the properties of PC, more specifically the eigenvalues and eigenvectors of the covariance matrix. The comparison between relative phase analysis and PCA shows that both provide similar and consistent results, underscoring the latter technique's sensitivity to the study of coordination performance. In addition, it provides a method for automatic pattern detection as well as an index of performance for each joint within the context of the global coordination pattern. Finally, the merit of the PCA technique within the context of central pattern generators (CPG) will be discussed.

The effect of sleep deprivation on median nerve somatosensory evoked potentials

The purpose of the study was to determine the effect of one night's sleep deprivation on the early and middle-latency median nerve (MN) somatosensory evoked potentials (SEPs). In 20 healthy volunteers, SEPs in response to electrical stimulation of the MN at the wrist were recorded for the 100-ms post-stimulus period, before and after one night of sleep deprivation. The P14 latency was significantly prolonged after sleep deprivation. We found significant increases in the amplitudes of the early parietal (N20-P24) and the frontal middle-latency (P45-N60) components following sleep deprivation. Our results indicate that somatosensory processing is altered after sleep deprivation.

Cerebellar thalamic activity in the macaque monkey encodes the duration but not the force or velocity of wrist movement

The way in which the cerebellum influences the output of the motor cortex is not known. The aim of this study was to establish whether information about force, velocity or duration of movement is encoded in cerebellar thalamic discharge and could therefore be involved in the modulation of motor cortical activity. Extracellular single cell recordings were made from the cerebellar thalamus (66 neurones) and VPLc (49 neurones) of four conscious macaques performing simple wrist movements with various load and gain conditions imposed. A significant correlation (Spearman's; P<0.05) was found between movement duration and the duration of neuronal discharge of most cerebellar thalamic neurones (65%), the velocity of movement and rate of neuronal discharge of some cerebellar thalamic neurones (23%), but not between force of movement and rate of neuronal discharge of any cerebellar thalamic neurones. Similar relationships were found between the activity of VPLc neurones and these movement parameters. The strength of the correlations increased when many cells were grouped and analysed as an ensemble, suggesting that populations of cerebellar thalamic (and VPLc) neurones can encode a signal with higher fidelity than single neurones alone. The ensemble data confirmed that the most robust association was between the duration of neuronal discharge and movement duration. We propose that the cerebellum does not provide the motor cortex with specific information about movement force or velocity, but rather that its major role is in activating many motor cortical regions for a specific duration, thus influencing the timing of complex movements involving many muscles and joints.

In vivo study of nerve movement and mechanosensitivity of the median nerve in whiplash and non-specific arm pain patients

Chronic pain following whiplash injury and non-specific arm pain (NSAP, previously termed diffuse repetitive strain injury) present clinicians with problems of diagnosis and management. In both patient groups there are clinical signs of altered nerve movement and increased nerve trunk mechanosensitivity. Previous studies of NSAP patients have identified altered median nerve movement at the wrist. The present study uses high frequency ultrasound imaging to examine changes to median nerve movement and clinical examination to assess altered mechanosensitivity of the median nerve. Longitudinal median nerve movement was measured in the forearm during maximal inspiration in nine post-whiplash patients with chronic neck and arm pain and eight controls subjects. Eight NSAP patients and seven controls were also studied. Transverse median nerve movement at the proximal carpal tunnel during 30 degrees wrist extension to 30 degrees flexion was also measured. A clinical examination of nerve trunk allodynia was performed in all subjects. Longitudinal nerve movement in the forearm was reduced by 71% in the post-whiplash patients and by 68% in NSAP patients compared to controls. In the whiplash patients the pattern of transverse median nerve movement at the proximal carpal tunnel was significantly different to controls (patient mean=2.57+/-0.80 mm (SEM) in a radial direction; control mean=0.39+/-0.52 mm in an ulnar direction). Signs of neural mechanosensitivity (i.e. painful responses to median nerve trunk and brachial plexus pressure and stretch) were apparent in both patients groups. Change in nerve tension and neural mechanosensitivity may contribute to symptoms in whiplash and NSAP patients.

Attenuation of the effect of remote muscle contraction on the soleus H-reflex during plantar flexion

OBJECTIVE

We investigated to what extent the facilitation of the soleus (Sol) Hoffmann (H-) reflex during a phasic voluntary wrist flexion (Jendrássik maneuver, JM) can be modulated by graded plantar flexion force and conditioning wrist flexion force.

METHODS

The subjects were asked to perform phasic wrist flexion under a reaction time condition. Sol H-reflex was evoked by stimulating the right tibial nerve at various time intervals (50-400ms) after the 'Go' signal for initiating JM while the ankle was at rest and while plantarflexing. The level of tonic plantar flexion force (isometric contraction of 10, 20 and 30% of maximal EMG) and conditioning wrist flexion (isometric contraction of 30, 50 and 80% of maximum voluntary contraction) during JM was graded systematically.

RESULTS

Although JM facilitation could be seen 80-120ms after the flexor carpi radialis (FCR) EMG onset even while plantarflexing, the magnitude of JM facilitation under plantar flexion was significantly decreased compared to that at rest. The degree of decrease in JM facilitation did not depend on the level of plantar flexion force. In contrast, the degree of JM facilitation was proportional to the level of wrist flexion force while the ankle was at rest and while plantarflexing, though the amount of JM facilitation significantly decreased while plantarflexing.

CONCLUSIONS

JM facilitation of Sol H-reflex is decreased while performing tonic voluntary contraction of the homonymous muscle. The degree of decrease in JM facilitation is independent of the level of homonymous muscle contraction, but depends on the level of remote FCR contraction. In clinical application, when we intend to elicit a maximum stretch reflex by JM, full relaxation of homonymous muscle should be carefully confirmed.

SIGNIFICANCE

Our results provide evidence for better understanding of the features of JM and insight into its clinical application.

Wrist median nerve motor conduction after end range repeated flexion and extension passive movements in Carpal Tunnel Syndrome. Pilot study

Carpal Tunnel Syndrome (CTS) can be due to a variety of different pathological conditions. These etiological and epidemiological differences may explain the non-homogeneous response to ordinary conservative therapeutical options observed in this syndrome. The aim of our study was to investigate on the possibility of identifying different sub-groups of patients among conservatively treatable CTS with different susceptibility to physiotherapeutic treatments. We decided to utilize an objective approach measuring some median motor nerve function parameters. Short term variations of Compound Motor Action Potential (CMAP) from the thenar eminence were compared in two groups of 55 hands (CTS patients and normal controls) after performance of two different types of end range passive movement. We found a different distribution of CMAP amplitude modifications within a sub-group of patients that suddenly improved more than the controls after two series of 10 end range passive flexions or after two series of ten end range passive extensions. Amplitude changes proved to be much more useful than latency variation studies in the provocative test neurophysiological approach. The method we propose appears to be useful for better surgical indication and/or for improvement of conservative therapeutic choice.

Anatomic characteristics and clinical importance of the superficial branch of the radial nerve

The aim of this study was to demonstrate anatomic variations of the superficial branch of the radial nerve (SBRN) and to discuss the importance of this branch for surgical approaches. Upper extremities of 24 cadavers without any known history of disease or trauma were examined, the SBRN became subcutaneous at a mean of 9.20 cm and bifurcated at a mean of 4.90 cm proximal to the styloid process of the radius in 48 specimens. At the level of the extensor retinaculum, the mean distance of the closest branch to the first dorsal compartment was 0.54 cm, while its mean distance to the dorsal tubercle (Lister's tubercle) was 1.58 cm. The relations of the three branches of the SBRN (SR1, SR2, SR3) to the anatomic snuffbox and lateral antebrachial cutaneous nerve (LABCN) were also examined. It was demonstrated that on eight wrists, SR2 went through the snuffbox (16.67%). On ten specimens, SR3 had connections with LABCN (20.83%). In four specimens, the SBRN did not have any bifurcation and was directly divided into SR1, SR2, and SR3. It should be very helpful to know the anatomic characteristics of the SBRN, especially for hand surgeons, to minimize the risk of injury of the SBRN during surgical approaches.

Differential generators for N20m and P35m responses to median nerve stimulation

To study the spatial and behavioral dynamics of cortical sources for N20m and P35m at varying stimulus intensities, we measured neuromagnetic cortical responses to left electric median nerve stimulation at the wrist in 17 male healthy adults. The stimulus intensity levels were individually determined according to sensory threshold (ST) for perceiving electric pulses. Using equivalent current dipole (ECD) modeling, we analyzed the peak latencies, amplitudes, and locations of ECDs from 14 subjects for N20m and P35m elicited at 2 ST, 3 ST, and 4 ST. Compared with N20m, P35m was localized 3.3 +/- 0.6 mm more superiorly at 2-4 ST, and 2.9 +/- 1.2 mm more medially at 3-4 ST. Superimposed over subjects' own MR images, N20m ECDs were localized in the area of 3b contralateral to stimulus side in all 17 subjects at 3 ST, whereas P35m ECDs were localized either in the postcentral (in 14 subjects) or in the precentral areas (in 3 subjects). We found no clear correlation between N20m and P35m in terms of peak latencies as well as the corresponding growth of activation strengths along with stepwise increase in stimulus intensity. Our results imply that the two early SEF components, N20m and P35m, have differential cortical generators, with distinctive neurophysiological behaviors in response to varying stimulus intensity levels.

Nerve entrapments of the wrist: early treatment preserves function

Nerve entrapment syndromes may affect as many as one in four office workers. Prompt diagnosis is critical to the selection of an appropriate and effective treatment.

Amelioration by mecobalamin of subclinical carpal tunnel syndrome involving unaffected limbs in stroke patients

Our previous study showed that overuse of the nonparetic hand and wrist of the nonparetic side following stroke result in significantly more abnormal on the nonparetic side than on the hemiparetic side in terms of electrophysiologic indices of median nerve function. The purpose of this study was to evaluate the effects of the orally administered mecobalamin, an analogue of vitamin B12, for carpal tunnel syndrome (CTS) in the nonparetic side in patients following stroke. In a randomized open label and prospective study of stroke patients, 67 received of 1500 mug mecobalamin daily for 2 years, and the remaining 68 (untreated group) did not. At baseline, sensory nerve conduction velocity, motor nerve conduction velocity, sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency, palm-to-wrist SNAP, motor nerve conduction velocity compound motor action potentials, and distal motor latency of median nerve were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Before the treatment 21 patients (31%) of untreated and 20 patients (30%) of treated group met electrophysiologic criteria for CTS. Sensory impairment of the nonparetic side had lessened in the treated group. After 2 years, all electrophysiologic indices of nonparetic side were significantly improved in the treated group compared with those in the untreated group. The improvement from baseline of electrophysiologic parameters in sensory nerve in the treated group was greater than the improvement measured in motor nerve. There were no side effects. Oral mecobalamin treatment is a safe and potentially beneficial therapy for CTS in stroke patients.

Effect of Occupational Keyboard Typing on Magnetic Resonance Imaging of the Median Nerve in Subjects with and without Symptoms of Carpal Tunnel Syndrome

OBJECTIVE

To examine the effects of occupational keyboard typing on median nerve shape and T2 relaxation and on forearm muscle T2 in professional typists with and without symptoms of carpal tunnel syndrome.

DESIGN

Based on the Levine Carpal Tunnel Syndrome Symptom Severity scale (LCTSS), 12 female professional typist volunteers were divided into asymptomatic (LCTSS < 1.3, n = 5) and symptomatic (LCTSS > 1.3, n = 7) groups. Magnetic resonance images were acquired from wrist and forearms of all subjects before, immediately after, and 8 hrs after 3 hrs of typing. Forearm muscle T2 and median nerve T2 cross-sectional area and long/short axis ratio were evaluated by blinded observers.

RESULTS

There was no difference between groups in any measured variable before typing. Median nerve T2 increased and long/short axis ratio decreased in asymptomatic subjects after typing, but there were no significant changes in symptomatic subjects. T2 increased in finger flexor muscles after typing, but there was no difference in the pattern of muscle T2 changes between groups.

CONCLUSION

In magnetic resonance images of the median nerve at the carpal tunnel, swelling and T2 increases from baseline are a normal response to typing and may be less likely to occur in subjects with symptoms of carpal tunnel syndrome.

Acustimulation wrist bands are not effective for the control of chemotherapy-induced nausea in women with breast cancer

This experiment examined the efficacy of an acustimulation wrist band for the relief of chemotherapy-induced nausea using a randomized three-arm clinical trial (active acustimulation, sham acustimulation, and no acustimulation) in 96 women with breast cancer who experienced nausea at their first chemotherapy treatment. Five outcomes related to wrist band efficacy (acute nausea, delayed nausea, vomiting, QOL, and total amount of antiemetic medication used) were examined. The five outcomes were examined separately using analysis of covariance controlling for age and severity of past nausea. There were no significant differences in any of these study measures among the three treatment conditions (P>0.1 for all). Study results do not support the hypothesis that acustimulation bands are efficacious as an adjunct to pharmacological antiemetics for control of chemotherapy-related nausea in female breast cancer patients.

Localization of the human female breast in primary somatosensory cortex

RATIONALE

Despite an extensive body of research on the topography of the primary somatosensory cortex (S1) little is known about the representation of the trunk.

AIM

The aim of this study was to determine the representation of the breast in S1 in human females.

RESULTS

The representation of the human breast in primary somatosensory cortex was determined in ten healthy female subjects. Non-painful electrical stimulation of the mammilla (Th4 dermatome), groin (L1 dermatome) and the first digit of both sides of the body activated cutaneous receptors and thus elicited somatosensory evoked potentials. The representation of these body parts in primary somatosensory cortex (S1) was determined using neuroelectric source imaging. Equivalent current dipole localizations were overlaid with individual structural magnetic resonance images to account for individual cortical differences. The breast representation was localized between the representation of the groin and the first digit. In the medial-lateral direction the representation of the breast was approximately 15 mm lateral of the longitudinal fissure in the contralateral hemisphere. Source localizations were stable across subjects. However, one subject showed ipsilateral representation of the breast, which might be related to bilateral receptive fields of the ventral body midline representation. This study confirms the Penfield and Rasmussen (1950) invasive data by use of noninvasive source imaging.

Neurovascular relationships of the approaches for arthroscopic total trapeziectomy with ligamentous stabilization

The aim of this study was to define the neurovascular relationships of the approaches used during arthroscopic total trapeziectomy with the Thompson "suspension-plasty." Fifteen fresh cadavers in which trapezio-metacarpal arthritis had been confirmed by preoperative radiographs were chosen. There were 12 women and 3 men (average age: 87 years), and small joint arthroscopy equipment was used. Two approaches for the trapezio-metacarpal joint were used: an ulnar approach situated at the ulnar border of the extensor pollicis brevis tendon and a radial approach placed at the middle of a line joining the tendons of the flexor carpi radialis and the abductor pollicis longus. A new transosseous approach at the base of the first metacarpal ("trans-M1" approach) is suggested and was used to do the ligamento-plasty. After the operation, a large skin flap was elevated in order to measure the distance between each surgical approach and the different neurovascular structures (radial artery, dividing branches of the superficial branch of the radial nerve and the end of the lateral cutaneous nerve of the forearm) and to verify the absence of neurovascular lesions. The different neurovascular structures at risk during this arthroscopic maneuver were the radial artery for the ulnar approach, the branches of the superficial branch of the radial nerve for all of the approaches and the ending of the lateral cutaneous nerve of the forearm for the radial and "trans-M1" approaches. The use of the approaches described allows arthroscopic trapeziectomy with the Thompson suspension-plasty without us having noted neurovascular lesion.

Prevalence and severity of carpal tunnel syndrome (CTS) during pregnancy

Carpal Tunnel Syndrome (CTS) is the entrapment of Median nerve at wrist. Pregnancy can affect prevalence and severity of CTS. In this study frequency and severity of CTS in pregnancy was evaluated. In this study 100 pregnant women were evaluated by Hand symptoms, CTS provocation tests (Tinel and Phalen) and for definite diagnosis of CTS standard EDX studies were used. For this purpose sensory and motor distal latency of Median were measured and compared with ulnar nerve. 17% of pregnant women had CTS with 23.5% bilateral involvement and 17.5% severe CTS. Prevalence of hand symptom and clinical sign of CTS (phalen and tinel sign) were 36% and 26% respectively. Results indicated that prevalence of CTS in pregnant women was significant. Although hand signs and symptoms are useful, EDX study is more reliable.

Acceleromyography vs. electromyography: an ipsilateral comparison of the indirectly evoked neuromuscular response to train-of-four stimulation

BACKGROUND

There is a considerable body of evidence which suggests that data obtained using acceleromyography (AMG) cannot be used interchangeably with observations obtained by mechanomyographic (MMG) or electromyograhic (EMG) methods. All previous such studies evaluated the responses from contralateral limbs. This investigation was undertaken to determine if these previously described differences were in part a function of observing the responses from opposing limbs.

METHODS

We compared the ipsilateral EMG and AMG response to an ED(95) bolus of atracurium in 50 subjects. In half of the individuals the thumb was free to move freely; in half, a small elastic preload was applied to the thumb. Train-of-four (TOF) recovery was followed until a TOF ratio >0.90 was recorded by both monitors. Acceleromyography vs. EMG differences and the resultant 95% confidence limits for twitch height (T1) and the TOF ratio were determined.

RESULTS

When the AMG TOF value had recovered to a value of 0.72 +/- 0.03; the simultaneously evoked EMG value averaged only 0.59 +/- 0.08. This difference was statistically significant (P < 0.001). Although the mean difference AMG vs. EMG was little more than 0.10, differences in an individual might be twice that amount. When the AMG TOF value had recovered to 0.90, the simultaneously evoked EMG value averaged 0.85. Again the 95% confidence limits for individual observations was very wide. With EMG, once the TOF ratio returns to a value of 0.70, T1 has returned to 95% of control. In contrast with AMG, return of T1 -95% of control requires a TOF ratio of almost 0.90. Addition of an elastic preload to the thumb decreased control TOF variability without effecting the relationship between twitch height and the TOF ratio.

CONCLUSION

Acceleromyographic TOF values tend to overestimate the extent of EMG recovery. Acceleromyographic TOF values <0.90 are indicative of incomplete neuromuscular recovery.

Dose-response relationship of rocuronium: a comparison of electromyographic vs. acceleromyographic-derived values

BACKGROUND

Acceleromyography (AMG) is being employed with increasing frequency as a research tool. However, there is almost no information available regarding the accuracy of values for drug potency obtained using AMG. This study was an attempt to determine if AMG-derived ED(50/95) values are interchangeable with those measured with a more traditional neuromuscular monitor.

METHODS

Thirty adult patients were studied. Anesthesia was induced and maintained with N20, propofol, and supplementation opioid. Tracheal intubation was accomplished without muscle relaxants. Simultaneous ipsilateral AMG and EMG responses to 0.10 Hz stimulation was recorded. Following instrument calibrations, a single dose of rocuronium was administered. The first patient received a bolus of 0.17 mg kg(-1) of rocuronium. Using the Hill equation with a postulated slope of 4.50, the ED(50) was calculated. The second subject received a dose which approximated the calculated ED(50) for patient no. 1. Successive subjects were given a dose based on the running average of the estimated ED(50).

RESULTS

The AMG-derived ED50/95 values for rocuronium (0.163 +/- 0.055 and 0.314 +/- 0.105 mg mg(-1)) were virtually identical to those established using EMG (0.159 +/- 0.043 and 0.306 +/- 0.084 mg kg(-1)). While mean peak twitch depression (Delta T1) was the same in both groups for individual subjects Delta T1 differed by +/- 20% (95% confidence interval).

DISCUSSION

Acceleromyography-derived twitch heights for individual patients are not necessarily interchangeable with information obtained using electromyography. Nevertheless, acceleromyography appears to be a valid methodology for determining the drug potency when a population rather than an individual subject is being studied.

Excitability of chronic hemiparetic muscles: determination of chronaxie values and strength-duration curves and its implication in functional electrical stimulation

Central nervous system disorders affect the anatomy and physiology of the lower motoneuron. This fact has an impact on the stimulation parameters, especially on the duration of the stimulating impulses, for functional electrical stimulation in chronic hemiparetic patients. The aim of this study was thus to test the excitability and to determine chronaxie values and strength-duration curves of weak wrist and finger extensor muscles and spastic finger and wrist flexor muscles in the hemiparetic arm. Twelve patients with chronic hemiplegia (>6 months after the onset of the cerebral lesion) participated in the study. A constant current stimulator was used. As to chronaxie values no significant differences were found between the extensor muscles (mean+/-SD: 0.44+/-0.16 ms) and flexor muscles (mean+/-SD: 0.36+/-0.22 ms). A moderate variability was seen for both extensor muscles (0.2-0.8 ms) and flexor muscles (0.1-0.9 ms). These values are well within the normal range determined for innervated muscles. All strength-duration curves were completely normal for each muscle. We conclude that in chronic hemiparetic muscles, impulses of the same duration can be used as in muscles of healthy subjects.

Intraneural perineurioma in a child with Beckwith-Wiedemann syndrome

To the authors' knowledge, this is the first report of an intraneural perineurioma in a child with Beckwith-Wiedemann syndrome. Intraneural perineurioma, previously known as localized hypertrophic neuropathy, is a rare benign peripheral nerve sheath tumor arising from perineurium. This report adds a new entity in the spectrum of tumor formation in Beckwith-Wiedemann syndrome.

What symptoms are truly caused by median nerve compression in carpal tunnel syndrome?

OBJECTIVE

This study aims to identify the symptoms, signs and distributions which are associated with neurophysiological carpal tunnel syndrome (N-CTS), defined by the finding of a median nerve lesion at the wrist through neurophysiologic studies, and to compare them with those of patients with sensory or motor complaints in the upper limbs whose electrophysiologic investigation did not show evidence of this syndrome.

METHODS

A cross-sectional study was performed, with prospective gathering of data, following a predetermined protocol. We included all patients older than 12 years who were referred for nerve conduction studies and electromyography of at least one of the upper limbs between August 2001 and January 2003. The patients answered a clinicoepidemiologic questionnaire and painted the areas in which they felt pain and those in which they felt paresthesia, and were also examined to test for classical signs CTS.

RESULTS

A neurophysiological diagnosis of CTS was reached in 1549 upper limbs (39%). Approximately 6% of the upper limbs with N-CTS and 16% of those without median nerve lesion do not have any hand or wrist symptoms (P<0.001). Paresthesia, pain, hand weakness and cramps were the symptoms statistically associated to N-CTS, with paresthesia being the one with the greatest power of association. This is usually felt in median innervation's territory, and is frequently extended to the whole hand, but without association with N-CTS when felt in proximal region.

CONCLUSIONS

One concludes that the most characteristic manifestation of carpal tunnel syndrome (CTS) is paresthesia. Pain also occurs very frequently but it is less specific, and weakness, meanwhile, seems to have a low frequency. We believe that the variability in the clinical presentation of CTS is largely due to the presence of associated diseases and our results provide information which could help to better define the clinical criteria used in the diagnosis of this syndrome.

‘Neurographic’ palmaris brevis sign in type II° ulnar neuropathy at wrist

OBJECTIVE

To investigate the source of an unusual and previously unreported volume conducted potential on motor nerve conduction studies. In a case of subacute ulnar neuropathy at wrist (UNW) selectively involving the deep motor branch, we recorded from the hypothenar eminence a large positive wave (2.5 ms-2 mV) preceding the negative takeoff of the delayed distal ulnar motor response.

METHODS

We performed multiple channels motor and sensory ulnar nerve (UN) conduction studies; these included selective electrical stimulation and anaesthetic block of UN branches and also selective recording of motor responses by single fibre needles; data were confirmed by an intraoperative neurophysiological study and correlated with MRI and surgical findings.

RESULTS

Detailed neurophysiological investigation demonstrated the generation of this waveform from the palmaris brevis (PB) muscle. MRI and surgical exploration documented a hypertrophy of this muscle.

CONCLUSIONS

In type II degrees UNW, depolarization of a spared palmaris brevis muscle may be recorded as a positive wave preceding the delayed abductor digiti minimi motor response.

SIGNIFICANCE

We underline the peculiar localizing value of this volume conducted 'meaningful artefact' in that particular setting. It actually represented an early neurographic analogue of what is known as the clinical 'Palmaris Brevis Sign' in long standing type II degrees UNW.