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Biomedical subjects

D Cros

Publications and source records attributed to D Cros.

At least 19 recordsLinked to original sources
PubMed2006

Facial onset sensory and motor neuronopathy (FOSMN syndrome): a novel syndrome in neurology.

A 'syringomyelia-like' syndrome has been infrequently reported in neurological disorders such as Tangiers disease and lepromatous leprosy. This study reports a novel 'syringomyelia-like' syndrome in four adult male patients, which we have termed facial onset sensory and motor neuronopathy, or FOSMN syndrome, that appears to have a neurodegenerative aetiology. Clinical, neurophysiological and pathological data of four patients were reviewed, including the autopsy in one patient. Four male patients (mean age at onset 43), initially developed paraesthesiae and numbness in a trigeminal nerve distribution, which slowly progressed to involve the scalp, neck, upper trunk and upper limbs in sequential order. Motor manifestations, including cramps, fasciculations, dysphagia, dysarthria, muscle weakness and atrophy developed later in the course of the illness. Neurophysiological findings revealed a generalized sensory motor neuronopathy of caudally decreasing severity in all four patients. Autopsy in one patient disclosed loss of motoneurons in the hypoglossal nucleus and cervical anterior horns, along with loss of sensory neurons in the main trigeminal sensory nucleus and dorsal root ganglia. FOSMN syndrome appears to be a slowly progressive neurodegenerative disorder, whose pathogenesis remains to be determined.

Adult↗
PubMed2006

[Multifocal motor neuropathies with conduction block: long-term follow-up of ten patients treated with IVIg].

UNLABELLED: Multifocal motor neuropathy (MMN) with conduction block responds to high-dose i.v. polyvalent immunoglobulins (IVIg) over the short term, but several studies have demonstrated a long-term increase in the degree of axonal degeneration and the number of conduction blocks, factors indicating a poor prognosis. The objective of this study was to evaluate the long-term effect of IVIg on clinical and neurophysiological parameters. METHODS: We reviewed the records of ten patients who had initially responded well to IVIg and received regular, long-term treatment. The parameters studied were muscular strength, motor function status (modified Rankin scale), as well as the number and progression of conduction blocks and the degree of axonal degeneration. Patients were followed up for a mean of 7.25 years (range, 3.5-12). They were all initially treated with 2 g IgIV/kg in 5 days every 4 weeks for 3 months. Maintenance therapy was administered every 4 weeks with dose adjustment to prevent muscular strength deterioration. RESULTS: We noted a significant and persistent improvement in muscular strength and in the Rankin motor function score over the long term, with no escape phenomenon. The number of conduction blocks and the degree of axonal degeneration decreased markedly. CONCLUSION: IVIg treatment remains effective over the long term in MMN. These conclusions differ from those of other authors in earlier studies, but our patients were treated with significantly higher doses of IVIg. These results have important implications for long-term treatment of patients with MMN.

Adult↗
PubMed2004

Thromboembolic complications of intravenous immunoglobulin treatment.

Intravenous immunoglobulin (IVIg) preparations are increasingly being used in the treatment of neuroautoimmune diseases. Although for most part this treatment is safe, serious side effects such as thromboembolic events have been reported. We report on 7 patients who suffered a thromboembolic event while being treated with IVIg. Four patients suffered a stroke or transient ischemic attack, 1 an inferior wall myocardial infarction, 1 a deep venous thrombosis, and 1 a retinal artery infarct. The age range of the patients was 57-81 and most had underlying risk factors, such as hypertension, hypercholesterolemia, atrial fibrillation, history of vascular disease and stroke, and deep venous thrombosis. Three patients received multiple IVIg infusions before suffering a thromboembolic complication. Therefore, the clinicians should be vigilant about the possibility of thromboembolic complications with each IVIg infusion and be especially judicious with the use of IVIg in patients with underlying risk factors.

Aged↗
PubMed2004

Pure motor mononeuropathy with distal conduction block: an unusual presentation of multifocal motor neuropathy with conduction blocks.

OBJECTIVE: To report an hitherto undescribed presentation of Motor Neuropathy with Multifocal Conduction Block (MMNCB). METHODS: Description of two patients presenting with complete paralysis of the 3 heads of the trapezius muscle (case one) and progressive weakness of finger extension (case 2). RESULTS: Nerve conduction studies (NCS) established that the corresponding nerves were distally inexcitable. In the affected muscles, no voluntary activity was elicited in both patients with spontaneous activity noted in patient 2. Systematic NCSs documented an asymptomatic, partial conduction block (CB) in a median nerve forearm segment in both patients. Neurophysiological follow-up after a dramatic response to intravenous immunoglobulins demonstrated recovery of the initially unobtainable motor responses. CONCLUSIONS: This indicates that a complete, distal CB of the motor fibers destined to the trapezius muscle in patient 1, and to the extensor indicis proprius in patient 2, had caused the heralding deficits. SIGNIFICANCE: These findings underscore the possibility of distal CB in this disorder and the need for extensive NCSs, including asymptomatic nerves, for an accurate diagnosis.

Adult↗
PubMed2002

Using posturography to detect unsteadiness in 13 patients with peripheral neuropathy: a pilot study.

Our aims were to use posturography to see if sway pattern differed between patients with large-fiber peripheral neuropathy and normal control subjects and, if it did, to compare posturography with conventional electromyography (EMG) as screening tools for large-fiber peripheral neuropathy. Thirteen patients who came to our neurophysiology laboratory with a preliminary diagnosis of peripheral neuropathy (made by their referring physicians) were compared with 7 nonmatched control subjects. All subjects received a neurologic examination and underwent posturography and conventional EMG. Results of posturography and conventional EMG were compared. Posturography showed abnormal sway patterns only in patients who had EMG abnormalities consistent with large-fiber peripheral neuropathy. These sway patterns differed significantly from those of the control subjects. Posturography seems to be a useful and well-tolerated screening test for patients with a history suggestive of peripheral neuropathy, and results of posturography agree with those of conventional EMG. Moreover, posturography directly measures increased sway in these patients and may be used as a more direct screen for risk of falls in this population.

Electromyography↗
PubMed2001

Analysis of the rutile-ring method of frequency-temperature compensating a high-Q whispering gallery sapphire resonator.

The rutile-ring method of dielectrically frequency-temperature compensating a high-Q whispering gallery (WG) sapphire resonator is presented. Two and three-dimensional finite element (FE) analysis has been implemented to design and analyze the performance of such resonators, with excellent agreement between theory and experiment. A high-Q factor of 30 million at 13 GHz and compensation temperature of 56 K was obtained. It is shown the frequency-temperature compensation can occur either because the rutile adds a small perturbation to the sapphire resonator or because of a mode interaction with a resonant mode in the rutile. The characteristics of both of these methods are described, and it is shown that for high frequency stability, it is best to compensate perturbatively.

Journal Article↗
PubMed2001

Compact, high-Q, zero temperature coefficient, TE011 sapphire-rutile microwave distributed Bragg reflector resonators.

Some novel new resonator designs based on the distributed Bragg reflector are presented. The resonators implement a TE011 resonance in a cylindrical sapphire dielectric, which is confined by the addition of rutile and sapphire dielectric reflectors at the end faces. Finite element calculations are utilized to optimize the dimensions to obtain the highest Q-factors and zero frequency-temperature coefficient for a resonator operating near 0 degree C. We show that a Q-factor of 70,000 and 65,000 can be achieved with and without the condition of zero frequency-temperature coefficients, respectively.

Journal Article↗
PubMed2000

Median neuropathy at the wrist: diagnostic utility of clinical findings and an automated electrodiagnostic device.

Clinical findings have limited value in predicting electrophysiologically confirmed median neuropathy at the wrist (MNW). To determine the value of clinical findings and an automated electrophysiologic neurodiagnostic device (AEND) in diagnosing MNW, we studied two groups of 75 consecutive patients (an initial group and a validation group, 150 total) referred to an academic electrophysiology laboratory for upper extremity complaints. The definitive standard for MNW was the neurologist's diagnosis after formal clinical and electrodiagnostic evaluation. The neurologist was blinded to the results of the AEND (NC-Stat, NeuroMetrix, Inc). In the validation group, the AEND yielded a distal motor latency (DML) in 97% of hands with a conventional motor response, and the correlation of the AEND DML with the conventional DML was 0.94 (P < 0.001). Of 248 symptomatic hands, the neurologist diagnosed 117 (47%) with MNW. At 90% specificity, the AEND DML had a sensitivity of 86% for MNW. Age, body mass index, sensory symptoms in digits 1 to 3, and nocturnal awakening were independent clinical predictors of MNW. Each 1-msec increase in the adjusted AEND DML was independently associated with an OR of 298 (95% confidence interval, 40 to 2233) for MNW. Each 1-msec increase in the F-wave latency was independently associated with an OR of 2.6 (95% confidence interval, 1.3 to 4.9) for MNW. Compared with a model based solely on clinical variables, an algorithm including symptom variables plus the AEND DML had an odds ratio for correct diagnostic classification of 6.3 (95% confidence interval, 3.8 to 12.3). The sensitivity at 90% specificity improved from 40% for the clinical model to 86% for the model with DML. A practical method for integrating clinical and electrophysiologic findings to assess the risk of MNW was proposed. This method correctly stratified 79% of control and MNW patients into very low- and high-risk groups, respectively. We concluded that MNW diagnosis is significantly improved with an AEND.

Adult↗
PubMed1999

Transcranial magnetic stimulation identifies upper motor neuron involvement in motor neuron disease.

OBJECTIVE: To evaluate the sensitivity of transcranial magnetic stimulation (TMS) to identify upper motor neuron involvement in patients with motor neuron disease. BACKGROUND: Diagnosis of ALS depends on upper and lower motor neuron involvement. Lower motor neuron involvement may be documented with electromyography, whereas definite evidence of upper motor neuron involvement may be elusive. A sensitive, noninvasive test of upper motor neuron function would be useful. METHODS: TMS and clinical assessment in 121 patients with motor neuron disease. RESULTS: TMS revealed evidence of upper motor neuron dysfunction in 84 of 121 (69%) patients, including 30 of 40 (75%) patients with only probable upper motor neuron signs and unsuspected upper motor neuron involvement in 6 of 22 (27%) patients who had purely lower motor neuron syndromes clinically. In selected cases, upper motor neuron involvement identified with TMS was verified in postmortem examination. Increased motor evoked potential threshold was the abnormality observed most frequently and was only weakly related to peripheral compound muscle action potential amplitude. In a subset of 12 patients reexamined after 11+/-6 months, TMS showed progression of abnormalities, including progressive inexcitability of central motor pathways and loss of the normal inhibitory cortical stimulation silent period. CONCLUSIONS: TMS provides a sensitive means for the assessment and monitoring of excitatory and inhibitory upper motor neuron function in motor neuron disease.

Adult↗
PubMed1999

Proximal sensory neuropathies of the Leg.

This article addresses the proximal sensory neuropathies of the leg, concentrating on those nerves that are purely sensory or have a predominately sensory onset. These include the lateral femoral cutaneous nerve, the ilioinguinal nerve, the genitofemoral nerve, and the posterior femoral cutaneous nerve. The obturator and femoral nerves are also summarily mentioned with respect to their sensory symptoms.

Diagnosis, Differential↗
PubMed1998

Pilot study of myoblast transfer in the treatment of Becker muscular dystrophy.

We evaluated myoblast implantation therapy in three subjects with Becker muscular dystrophy who received 60 million myoblasts in one tibialis anterior (TA) muscle 2 months after beginning cyclosporine immunosuppression (5 to 10 mg/kg) that continued for 1 year. Strength of the implanted and control TA muscles was measured before and after treatment using a gauge to record TA contraction force. Our protocol controlled for the effects of cyclosporine and myoblast injections. In this pilot study, myoblast implantation did not improve strength of the implanted TA muscles.

Adult↗
PubMed1996

Mice lacking the myotonic dystrophy protein kinase develop a late onset progressive myopathy.

Myotonic dystrophy (DM) is an autosomal dominant disorder resulting from the expansion of a CTG repeat in the 3' untranslated region of a putative protein kinase (DMPK). To elucidate the role of DMPK in DM pathogenesis we have developed Dmpk deficient (Dmpk-/-) mice. Dmpk-/-mice develop a late-onset, progressive skeletal myopathy that shares some pathological features with DM. Muscles from mature mice show variation in fibre size, increased fibre degeneration and fibrosis. Adult Dmpk-/-mice show ultrastructural changes in muscle and a 50% decrease in force generation compared to young mice. Our results indicate that DMPK may be necessary for the maintenance of skeletal muscle structure and function and suggest that a decrease in DMPK levels may contribute to DM pathology.

Animals↗
PubMed1996

Guillain-Barré syndrome: clinical neurophysiologic studies.

Guillain-Barré syndrome is a well-defined clinical entity corresponding to primary inflammatory demyelinating lesions of peripheral nerves and spinal roots in the majority of cases seen in Western Europe and North America. Documentation of conduction abnormalities characteristic of demyelination in the context of rapidly developing weakness confirms the clinical diagnosis of acute inflammatory demyelinating polyradiculoneuropathy. These abnormalities include (1) conduction block, (2) markedly prolonged distal latencies, (3) marked slowing of motor conduction velocities, and (4) absent or impersistent F responses. Other abnormalities are of ambiguous significance: (1) low amplitude compound muscle responses, (2) absent sensory nerve potentials, (3) reduction in the maximum EMG recruitment pattern, which may all (1, 2, and 3) indicate conduction block or axonal degeneration, and (4) fibrillation potentials due to breakdown of motor axons, a frequent non-specific effect of primary inflammatory demyelination. A Guillain-Barré variant due to immune-mediated primary axonal degeneration has also been recently described.

Acute Disease↗
PubMed1995

Modulation of motor activity by cutaneous input: inhibition of the magnetic motor evoked potential by digital electrical stimulation.

We examined the inhibitory effect of a brief train of digital (D2) electrical stimuli at 4 times perception threshold on transcranial magnetic motor evoked potentials (MEPs) recorded from abductor pollicis brevis (APB) and flexor carpi radialis (FCR) muscles ipsilateral to the side of D2 stimulation. We compared this to the inhibitory effect of ipsilateral D2 stimulation on averaged rectified EMG recorded at 10% maximum voluntary contraction and on F-responses and H-reflexes recorded from these same muscles. We also compared MEPs recorded following D2 stimulation just above perception threshold to MEPs following higher intensity D2 stimulation. As well, we assessed the effect of preceding D2 stimulation on MEPs recorded from a relaxed versus tonically contracted hand muscle. D2 stimulation elicited a triphasic response of modest MEP facilitation followed by inhibition and further facilitation. The duration and onset of MEP inhibition correlated with those of the initial period of rectified EMG inhibition, however, the magnitude of MEP inhibition was generally less than the magnitude of EMG inhibition, consistent with a greater inhibitory effect of digital afferents on smaller motor neurons. MEPs were not facilitated during the rebound of EMG activity (the E2 period) that usually followed the initial period of EMG inhibition (I1 period). The behavior of H-reflexes and F-responses following ipsilateral D2 stimulation suggested that inhibition of both EMG and MEPs is not mediated via presynaptic inhibition of Ia afferents, and that inhibition is augmented by descending rather than segmental input to spinal motor neurons. Tonic contraction of the target muscle during D2 stimulation decreased the inhibitory effect of the preceding digital stimulus possibly due to recruitment of larger spinal motor neurons less likely to be inhibited by cutaneous input.

Adult↗
PubMed1995

Assessment of cortical motor output: compound muscle action potential versus twitch force recording.

To determine whether motor evoked potential (MEP) amplitude and area are accurate measurements of the magnitude of response to magnetic cortical stimulation, we simultaneously recorded the twitch and MEP in the first dorsal interosseous muscle of 8 normal subjects. Consecutive stimuli were delivered at increasing stimulus intensities (SI) or with increasing levels of background voluntary muscle contraction (BVC). There was stimulus to stimulus variability in MEP amplitude, area and twitch force. At low SI and at low levels of background contraction, there was a good correlation between twitch amplitude and MEP amplitude and area (r = 0.6-0.96, P < 0.005). Increasing either variable caused the correlation to decrease significantly (r = 0.02-0.31, P > 0.01). With increasing SI, MEP amplitude and area plateaued but twitch force continued to increase. A similar pattern was observed with higher levels of background muscle contraction although in some subjects a second increase in MEP amplitude and area was seen. Collision experiments demonstrated that the amplitude of the EMG activity resulting from repetitive motoneuron firing increased as SI was increased. This is due to multiple descending volleys which result in repetitive firing of some spinal motoneurons. Rapid, repetitive firing of some motor units is likely to result in phase cancellation and, therefore, the MEP amplitude, and to a lesser extent area, do not accurately reflect the net motor output.

Action Potentials↗
PubMed1995

Crossed inhibition in the human motor system.

We used transcranial magnetic stimulation in humans to investigate the effect of focal unilateral stimulation of the motor cortex on the function of the contralateral motor cortex. Surface-recorded, rectified, averaged electromyography (EMG) showed relative silent periods in small hand muscles at 35-64 and 123-158 ms following ipsilateral cortical stimulation over the hand area. The first inhibitory phase started 11 ms after the minimum corticospinal conduction time from the contralateral cortex, appropriate for transcallosal conduction. Foot muscles (with focal stimulation over the ipsilateral hand area) also showed silent periods at 61-104 ms, indicating a marked spread of the inhibitory effect throughout the opposite motor cortex. H-reflex studies in the upper limb showed that this inhibitory effect was not mediated at the level of the alpha motoneuron. Single motor unit peristimulus time histogram studies in upper limb muscles showed inhibition similar to that seen in the surface recordings and no evidence of excitation following ipsilateral motor cortex stimulation. Transcranial magnetic stimulation performed with large circular coils centered at the vertex activates both excitatory and inhibitory processes bilaterally so that focal unilateral stimulation is preferable in detailed studies of motor system physiology.

Adult↗
PubMed1994

Physiological motor asymmetry in human handedness: evidence from transcranial magnetic stimulation.

We hypothesized that human handedness might be associated with measurable differences in the excitability of the motor system. We compared the thresholds for electromyographic activation of the left and right abductor pollicis brevis (APB) and biceps muscles in 30 left-handers and 30 right-handers, by varying the direction of a brief monophasic pulse in a circular electromagnetic coil centered over the vertex of the scalp. In right-handers, we found that the threshold for activation of muscles in the right arm was lower than the threshold for activation of corresponding muscles in the left arm. In left-handers, the reverse was true. Threshold asymmetry was influenced significantly by the consistency with which each subject used the writing hand to perform other motor tasks, and was not significant between non-consistent left-handers and right-handers. Our results indicate that human handedness, and in particular, consistency of hand preference, are associated with lateralized differences in the excitability of motor system projections activated by transcranial magnetic stimulation. Our findings might reflect physiological differences in corticospinal tract function or cortical motor representation.

Adult↗