PubMed Health⌕ Search

Biomedical subjects

D Cros

Publications and source records attributed to D Cros.

At least 55 records · Page 3Linked to original sources
PubMed1991

Magnetic stimulation of the human motor cortex: ipsilateral and contralateral facilitation effects.

Voluntary contraction of a muscle greatly increases the amplitude and decreases the latency of the motor potentials evoked by electromagnetic coil brain stimulation (facilitation). Facilitation has also been observed with contraction of a nearby ipsilateral and a contralateral homologous muscle. We studied these facilitatory relationships in 5 normal subjects in small hand, forearm and upper arm muscles using surface-recorded compound motor action potentials, single motor unit recordings, and post-stimulus time histograms. There was no evidence for spread of facilitation between any pair of muscles if the muscle from which motor evoked potentials (MEPs) were recorded was completely at rest during brain stimulation, although this sometimes required training to accomplish or could not be achieved. Thus, although spread of facilitation has been observed by others under these conditions, we did not find this effect. There may be significant interindividual variations in the degree of facilitatory spread.

Action Potentials↗
PubMed1990

RR interval variation and the sympathetic skin response in the assessment of autonomic function in peripheral neuropathy.

The diagnostic value of two simple tests of autonomic function, the RR interval variation and the sympathetic skin response, was evaluated relative to symptoms of dysautonomia in 53 patients with peripheral neuropathy. Of 22 patients with peripheral neuropathy and clinical dysautonomia, 15 showed abnormal results on both tests, and 7 had abnormal results on one test only. In none of the patients with dysautonomia were both tests' results normal. Conversely, all 15 patients with abnormal results of both sympathetic skin response and RR interval variation had symptoms of dysautonomia, while 7 of 15 patients with abnormalities limited to one test had such symptoms. No patient with normal results on both tests had clinical dysautonomia. These data indicate that RR interval variation and sympathetic skin response, both of which can easily be performed in the electromyography laboratory, are helpful in combination in the assessment of autonomic function in peripheral neuropathies.

Adolescent↗
PubMed1990

Spatial dispersion of magnetic stimulation in peripheral nerves.

To assess the longitudinal dispersion of the stimulus induced by the magnetic coil, collision experiments were performed in seven normal ulnar nerves. A supramaximal electrical stimulus S1 was delivered at the wrist, and followed by a supramaximal stimulus S2 in the upper arm, which was either electrical (electrical collision studies), or magnetic (magnetic collision studies). The interstimulus interval was varied by 0.2 msec increments from the time of complete cancellation of the S2 evoked motor response onwards, to include the entire span of recovery of that compound motor action potential. Collision curves were obtained for both magnetic and electrical stimuli by plotting the amplitude of the motor response elicited by S2 as a function of the interstimulus interval. In all seven normal ulnar nerves, comparison of the collision curves showed that the S2 evoked motor response is restored significantly more slowly when magnetic stimulation is used. This finding is best explained by longitudinal dispersion of the stimulus induced by the magnetic coil relative to conventional electrical stimulation, the large fibers being stimulated further away from the coil than the small ones. This interpretation is confirmed by the findings obtained with the same method in two cases of ulnar neuropathy, and by comparison of different intensities of magnetic stimulation.

Action Potentials↗
PubMed1990

Superior sagittal sinus thrombosis in a patient with protein S deficiency.

A 30-year-old man presented with sagittal sinus thrombosis. He had a history of multiple thrombotic events since adolescence, and his father had had a similar history. Laboratory studies revealed the complete absence of free protein S in his plasma. Protein S deficiency, an autosomal dominant disorder, is an identifiable cause of cerebral thrombosis. The literature and our experience with this case suggest that long-term anticoagulant therapy may prevent thrombotic episodes in patients with this disorder.

Adult↗
PubMed1990

Herpes simplex labialis and trigeminal neuropathy.

Three patients had a transient trigeminal sensory disturbance associated with an ipsilateral herpes simplex (HS) labialis lesion. These cases support the theory that isolated trigeminal sensory disturbance may be caused by intermittent reactivation of HS virus in the trigeminal ganglion.

Adult↗
PubMed1990

Cervical magnetic stimulation.

We stimulated the cervical region with a 9-cm-diameter magnetic coil on centered on the spinous processes in 21 normal subjects. We obtained maximal amplitudes with clockwise coil current in right-sided upper extremity muscles and counterclockwise coil current in left-sided upper extremity muscles. Optimal stimulation sites for biceps, triceps, and abductor digiti minimi were C-3 or C-4, C-4 or C-5, and C-4, C-5, or C-6, respectively. The latencies of the muscle responses varied little in the same subject in spite of marked amplitude changes due to suboptimal position of the coil or submaximal stimulator output. In abductor digiti minimi, the amplitude of the muscle response on cervical magnetic stimulation was 9 to 100% of the supramaximal amplitude on wrist electrical stimulation. We established normal values for latency, amplitude, and interside differences for the above 3 upper extremity muscles. The findings were reproducible, and the latencies obtained with large coils from different manufacturers in the same subjects were comparable. We found no advantage in bipolar recording over tendon-belly montage. Comparison of magnetic and electrical needle root stimulation in the same subjects showed that the magnetic stimulus was more proximal in biceps and triceps, and that the site of excitation was approximately the same in abductor digiti minimi. Indirect assessment of the longitudinal site of excitation based on F-wave minimal latency indicated that excitation occurred within millimeters of the emergence of axon of the peripheral motor neuron.

Adult↗
PubMed1990

Variability of quantitative sensory testing: implications for clinical practice.

The conventional estimation of motor, sensory, and mixed nerve conduction velocities reflects activity in the fastest conducting, heavily myelinated nerve fibers that are only a small proportion of the total. Unmyelinated and thinly myelinated fibers are not evaluated by this technique and numerically represent the largest group of fibers in human cutaneous nerves. The availability of new quantitative techniques to study this aspect of sensory function is an important addition to standard electrodiagnosis. Patient understanding and cooperation is essential because subjective responses are evaluated. We evaluated a reference range for 20 healthy subjects as well as variability on repeated testing. Vibration and thermal thresholds were measured bilaterally at several sites. Measurements were repeated at intervals ranging from two days to three months. There was no side difference but substantial site differences were noted for all measurements. Intraindividual variation was substantial but within the expected range for a psychophysiologic test. Close correlation was noted between various measurements at same and different sites, indicating a great degree of interindividual variation. The Marstock method is recommended for routine clinical use.

Adult↗
PubMed1990

Magnetic stimulation F-responses.

We used the 9 cm Cadwell magnetic coil, stimulating at the wrist, to obtain simultaneous median and ulnar nerve F-responses. Surface recording was performed from conventional thenar and hypothenar sites. It is known that with this type of coil it is difficult to accomplish selective supramaximal stimulation of the median or ulnar nerve individually. We found it possible, however, to record a compound muscle action potential of supramaximal or near supramaximal amplitude, as well as F-responses, in both thenar and hypothenar muscles simultaneously. We assessed this technique for F-response latency determination in controls and patients with carpal tunnel syndrome. In controls, there was no significant difference in the F-minimal latency or the F-minimum-maximum range obtained by the two methods. In patients with carpal tunnel syndrome, with median F-responses very delayed or absent on conventional testing, magnetically elicited thenar F-responses were of shorter latency, similar to F's recorded in the hypothenar muscles, suggesting they were recorded from ulnar innervated thenar muscles. Although magnetic stimulation allows simultaneous determination of median and ulnar F-latencies, sparing patients several painful stimuli, and shortening the electrophysiologic examination, magnetic stimulation in patients with carpal tunnel syndrome may elicit thenar recorded F-responses that are not of median origin. Use of this technique is limited by the lack of focality of the stimulus, which has been the major limiting factor in its use on peripheral nerves.

Action Potentials↗
PubMed1989

Relapsing bilateral brachial plexopathy during pregnancy. Report of a case.

We describe a case of relapsing bilateral brachial plexopathy occurring during pregnancy and the postpartum period. This condition is known to occur with a familial predilection, but it has not been previously reported on a sporadic basis. The outcome was poor and associated with several psychosocial consequences.

Adult↗
PubMed1989

Muscle hypertrophy in Duchenne muscular dystrophy. A pathological and morphometric study.

In order to investigate the pathological basis of muscle hypertrophy in Duchenne dystrophy, 9 biopsy specimens of the lateral gastrocnemius and 7 of the vastus lateralis were compared. All patients had calf hypertrophy and normal strength in gastrocnemius-soleus, whereas the quadriceps biopsied were all atrophied and weak. The patients' ages ranged from 4 to 11 years. The pathological and histochemical changes were assessed semi-quantitatively. Comparison of the gastrocnemius and quadriceps groups showed that the number of hypercontracted fibres, the degree of endomysial fibrosis and the degree of fat infiltration were significantly higher in the quadriceps. The fibre type differentiation was better in the gastrocnemius group. The mean fibre diameter was above normal in all gastrocnemius biopsies and showed no increase with age. In the quadriceps, fibre hypertrophy was found early in the disease but had changed into fibre atrophy in the three oldest patients. When present, fibre hypertrophy involved both fibre types. The amount of fat-fibrosis per unit area was increased in both groups, but more severely so in the quadriceps. These results indicate that there is no true muscle hypertrophy in the gastrocnemius, in which the fat-fibrosis component was increased in all patients and that the dystrophic process is more active in the quadriceps. The finding of persistent fibre hypertrophy in the gastrocnemius is discussed with respect to the postural abnormalities observed in the lower limbs in Duchenne dystrophy.

Biopsy↗
PubMed1989

Liquid crystal thermography: quantitative studies of abnormalities in carpal tunnel syndrome.

We performed liquid crystal thermography (LCT) in 38 normal hands and in 23 hands with carpal tunnel syndrome (CTS) documented by nerve conduction studies (NCS). Two of the authors unaware of the clinical situation read the 2 palmar thermograms taken at a 5-minute interval. They determined the absolute temperatures of the tip of digit 1 (D1), D2, D3, D4, D5, and of the thenar and hypothenar eminences. We calculated the temperature differences (absolute values throughout) between any 2 of these 7 sites, and computed the median index (MI = [D1 - D2] + [D1 - D3] + [D2 - D3]). Comparison of the control and CTS groups revealed greater temperature differences in CTS between D1 - D3, D1 - D4, D3 - D5, D4 - D5, and MI. There was a marked overlap between the 2 groups. Comparison of individual CTS hands with controls revealed definite thermographic abnormalities in 0 of 9 hands with mild NCS abnormalities, and in 7 of 14 hands with marked NCS abnormalities. These findings indicate that the sensitivity of LCT in CTS is low compared with NCS, and previous favorable reports concerning thermography in CTS may have been due to lack of control series or absence of quantitation.

Adult↗
PubMed1989

[Carbamazepine-sensitive neuromyotonia and Charcot-Marie-Tooth disease of the neuronal type].

Following an anti-smallpox vaccination a 17 year-old boy developed spontaneous muscular activity with cramps and fasciculations in the lower limbs. There was distal amyotrophy of the lower limbs and pes cavus. Clinical signs suggested a cholinergic hyperfunction. EMG showed a significant spontaneous activity and was neurogenic in the lower limbs. Nerve conduction velocities were consistent with axonal damage. Muscular biopsy showed aspects of chronic denervation. Neuromyotonia disappeared with carbamazepine treatment. This case can be added to the reported associations of neuromyotonia and Charcot-Marie-Tooth disease. Such cases are an additional argument for the axonal origin of neuromyotonia.

Adolescent↗
PubMed1989

Magnetic stimulation of the human motor cortex: facilitation and its relationship to a visual motor task.

Transcranial magnetic stimulation of the motor cortex can evoke motor responses in small hand muscles. This response can be facilitated by a background muscle contraction of the target muscle, resulting in an enhanced compound muscle action potential (CMAP) with a shorter onset latency. A number of intracortical mechanisms may account for this facilitatory effect, including, in part, direct input from visual to motor cortex. We studied the facilitation produced by a visual-motor task and compared those results with the facilitation produced by the same task without the visual cues. No differences in facilitation of amplitude or latency were observed. This suggests that there is no direct influence exerted by the visual cortex upon those elements of the motor cortex activated by a tangential magnetic stimulus, i.e., corticocortical and corticospinal neurons and their processes. Also, the large majority of facilitation (90%) was produced by a very small background voluntary contraction (less than 5% of maximum), indicating that any mild-to-moderate contraction of the target muscles will produce a consistent response for clinical measurements.

Electromyography↗
PubMed1988

Peripheral neuropathy in myotonic dystrophy: a nerve biopsy study.

Sural nerve biopsies from 13 unselected myotonic dystrophy patients and 6 normal controls were studied morphometrically. The myelinated fiber density was reduced in 11 of the 13 myotonic dystrophy patients, with preferential loss of large myelinated fibers. Unmyelinated fiber densities and diameters were normal. Teased fiber studies commonly revealed focal areas of remyelination and abnormal wrinkling of the myelin sheath. Measurement of internodal length disclosed features of both axonal regeneration and focal demyelination-remyelination. These findings are consistent with a chronic axonopathy of moderate severity, possibly due to axonal atrophy.

Adult↗
PubMed1984

Peripheral neuropathy induced by amiodarone chlorhydrate. A clinicopathological study.

Four cases of amiodarone neuropathy are reported. Patients presented a sensorimotor neuropathy with distal predominance. Improvement occurred after drug discontinuation. Nerve conduction velocities were significantly decreased. Other secondary effects of amiodarone were noted in two cases. In one case serum levels of amiodarone and N-monodesethylamiodarone were evaluated during and after treatment. Pathological study of nerve with morphometric evaluation was performed. Axonal degeneration changes were predominant in 3 cases. Aspects of segmental demyelination and remyelination were noted in one case and related to secondary demyelination. Numerous lysosomal inclusions were present in Schwann cells, fibroblasts, capillary endothelial and perithelial cells and in perineural cells. Similar inclusions have been observed in other drug-induced lipidosis. The factors responsible for this neuropathy are unknown. In one case, amiodarone-induced hepatic failure might explain the persisting high serum levels of the drug.

Adult↗
PubMed1984

[Tendon areflexia in congenital myopathies accompanied by atrophy of type I fibers. Electrophysiologic study].

A predominance and/or an atrophy of type I fibers and a loss of deep tendon reflexes are often observed in different types of congenital myopathy. Various data indicate that both findings can be linked: dysfunction of the myotatic reflex can induce predominant involvement of type I fibers. In order to specify the mechanism of the loss of tendon reflex, an investigation of the Hoffmann reflex (H reflex) was performed in one case of centronuclear myopathy and in one case of congenital type fiber disproportion with type I hypertrophy. The Achilles tendon reflex was absent but the H reflex showed normal recruitment amplitude and latency. The Jendrassik maneuver reinforced the H reflex. These results indicate the involvement of muscle spindles or impairment of the fusimotor system. Nuclear bag intrafusal fibers have common characteristics with type I extrafusal fibers. Both types of fibers could be involved simultaneously in congenital myopathies, thus explaining the loss of tendon reflex.

Child↗
PubMed1984

[Association of polymyositis, myasthenia, and thymoma. A case and review of the literature].

We report the case of a 51 years old woman with myositis, myasthenia gravis and thymoma. First apparent sign is myositis in 1976 but chest X ray show a mediastinal opacity and the patient reports an intermittent diplopia since 1973. The evolution of myositis occurs in two bouts in 1976 and 1981, Myasthenia gravis restricted to diplopia from 1973 to 1979 grow worse first alone then in association with increase of myositis signs in 1981. The mediastinal opacity seen on chest X ray in 1976 don't change and is revealed to be a thymoma at operation in 1981. After thymoma ablation myasthenic and myositis signs decrease. This pathologic association is found 24 times in literature and involves "giant cells" in muscle biopsy in about 50 p. 100 of cases and a myocarditis also with "giant cells". Those "giant cells" unusual in common myositis appears to have a prognostic value.

Adult↗