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J Mathis

Publications and source records attributed to J Mathis.

At least 37 records · Page 2Linked to original sources
PubMed1998

Task-dependent facilitation of motor evoked potentials during dynamic and steady muscle contractions.

Task-dependent differences in the facilitation of motor evoked potentials (MEPs) following cortex stimulation were studied in a proximal (deltoid) and a distal muscle (abductor digiti minimi; ADM) in 23 healthy subjects during both dynamic and steady contractions of the target muscle under isometric and under nonisometric conditions. In the deltoid, MEP amplitudes were significantly greater if stimulation was performed during dynamic contractions than during steady contractions, despite equal background electromyographic levels just prior to the stimulus. The same task-specific extra facilitation of deltoid MEP amplitudes was also found with magnetic stimulation of the brain stem instead of the cortex in 3 subjects. In the ADM, no such task-dependent extra facilitation of MEPs during dynamic contractions was found. It is concluded that in the deltoid, during dynamic contractions, a greater proportion of the spinal motoneurons is close to depolarization threshold (greater "subliminal fringe") whereas the number of firing motoneurons is similar to that during steady contraction. The lack of task-dependent extra facilitation of MEPs in the ADM is explained by the predominant recruitment principle for force gradation in small hand muscles, which is in contrast to the predominant frequency principle used in proximal muscles.

Adult↗
PubMed1998

Optic neuropathy associated with sleep apnea syndrome.

OBJECTIVE: The study aimed to determine ocular abnormalities in sleep apnea syndrome (SAS), an entity characterized by repetitive upper airway obstructions during sleep, inducing hypoxia and sleep disruption with the risk of cardiovascular and neurologic sequelae. DESIGN: The study design was a case series. PARTICIPANTS: Nine patients referred for evaluation of suspected SAS participated. INTERVENTION: Complete ophthalmologic examination, including computerized perimetry, was performed. MAIN OUTCOME MEASURES: Correlations between the respiratory disturbance index (RDI) during night sleep, a value used to diagnose and to grade SAS, and visual field indices using the Spearman rank correlation coefficient (r(s)) were measured. RESULTS: One patient was excluded from the statistical analysis because of optic nerve drusen with constricted visual fields, another because of tilted discs with corresponding temporal visual field defects. All three patients with severe SAS and one patient with moderate SAS had relative nasal arcuate visual field defects; two patients with severe SAS also had paracentral relative defects. One patient with normal polysomnographic result and two patients with mild or moderate SAS had normal visual fields. The RDI correlated positively with the mean visual field defect (r(s) = 0.81, P < 0.05) and with the visual field loss variance (r(s) = 0.78, P < 0.05). The clinical ophthalmologic examination results were normal in all seven patients. In two of the three patients with severe SAS treated with continuous positive airway pressure (CPAP), visual field defects remained stable over 18 months. The patient with optic nerve drusen also had severe SAS and was, therefore, treated with CPAP. His constricted visual fields improved dramatically after treatment. CONCLUSIONS: Visual fields of patients with SAS showed defects consistent with an optic neuropathy. The CPAP therapy seems to stabilize or even reverse visual field defects.

Adult↗
PubMed1998

Dependence of the transcranially induced silent period on the 'instruction set' and the individual reaction time.

OBJECTIVES AND METHODS: We looked for influences of the experimental condition on the silent period (SP) from transcranial motor cortex stimulation and analyzed how the instruction given to the subject, as well as the individual reaction time, might affect the duration of the SP in the biceps brachii muscle. RESULTS: The duration of the SP was found to critically depend on the subject's voluntary reaction of the target muscle immediately after the stimulus. With low stimulus intensity and low background force, the duration of the silent period was significantly longer in 10 of 13 subjects (P = 0.002) when they were instructed to relax quickly after the stimulus rather than to maintain the the force at a constant level. A significant shortening of the SP (P = 0.02) was observed when the subjects were instructed to perform a rapid contraction of the target muscle in reaction to the cortical stimulus. With low stimulus intensity and high background force, the same influence of the instruction set was found in 6 of 13 subjects. When the subjects were left without precise instruction, the SP duration was unpredictable. In 10 subjects, the SP corresponded to that obtained with the instruction to maintain the force at a constant level. However, in 3 subjects it was prolonged to the value observed in the 'relax' instruction. With greater stimulus intensities, the effect of the instruction set on the SP duration was generally smaller. A significant prolongation was nevertheless found at low background forces with rapid relaxation (P < 0.001), and a significant shortening was found at high background forces with rapid contraction (P < 0.001) after the stimulus. The SP duration observed with 20% of maximal voluntary contraction (MVC) significantly correlated with the individual reaction time. No such correlation was found for the SP obtained with 80% MVC. The SP was slightly longer at 20% MVC, as compared to 80% MVC within each instruction group. This effect was significant (P < 0.05) at low stimulus intensities. CONCLUSIONS: Therefore, when assessing the SP duration for diagnostic purposes, not only the stimulus intensity but also the background force and the voluntary reaction must be standardized. Furthermore, great stimulus intensities and high background forces should be used to minimise the effects of instruction set and individual reaction time.

Adult↗
PubMed1997

MRI of paramedian thalamic stroke with sleep disturbance.

The paramedian thalamus is believed to play an important role in the regulation of sleep, and disturbances of sleep regulation are known to occur in paramedian thalamic stroke (PTS). We examined 12 consecutive patients with PTS and sleep disturbance by MRI. Two distinct groups of patients could be defined: six presenting with severe hypersomnia (group 1) and six with slight sleepiness (group 2). On MRI, all patients had ischaemic lesions involving the paramedian thalamic nuclei, the centre of the lesions being the dorsomedial and centromedial thalamic nuclei. In group 1 the lesions were bilateral, butterfly-shaped infarcts involving the paramedian nuclei (three cases); or unilateral with an extension into the subthalamic nuclei. In group 2 the lesions were unilateral and limited to the paramedian nuclei, mainly the dorsomedial nucleus. Bilateral lesions can be attributed to a common origin in some cases for both paramedian thalamic arteries and the mesencephalic arteries.

Adolescent↗
PubMed1997

Patterns of muscle activity in legs in sleep apnea patients before and during nCPAP therapy.

Nocturnal muscle activity in legs (MAL) was studied in 19 patients with sleep apnea syndrome before and during nCPAP. We distinguished periodic (P-MAL) and nonperiodic (N-MAL) as well as apnea-associated and independent MALs. N-MALs were strongly associated with apneas and disappeared during nasal continuous positive airway pressure (nCPAP). P-MALs showed a rather long intermovement interval (IMI) of about 54 s when associated with respiratory disturbances and a shorter one of about 38 s when occurring independently. In 5 patients with predominantly independent P-MALs and a short IMI before and during nCPAP an incidental coexistence of sleep apnea with periodic leg movements in sleep syndrome (PLMS) was postulated. Five patients with an equal number of apnea-associated and independent MALs before nCPAP had a long IMI which shortened under nCPAP, while the majority of MALs become independent. This could indicate a facilitating or an unmasking effect of nCPAP on PLMS. Four patients with predominantly apnea-associated MALs with a long IMI before nCPAP showed an unchanged MAL pattern under nCPAP, despite the disappearance of apneas. Since some arousals persisted in these patients, insufficient nCPAP pressure with an upper airway resistance syndrome was suspected. We conclude that when P-MALs persist under nCPAP therapy a long IMI may indicate an upper airway resistance syndrome, whereas a short IMI may indicate a coexisting or even induced PLMS.

Adult↗
PubMed1996

Dissociation of affinity and efficacy in KOR-3 chimeras.

KOR-3 chimeras were constructed in which the first coding exon of KOR-3 was exchanged for the corresponding first coding exon of either MOR-1 (MOR-1/KOR-3) or DOR-1 (DOR-1/KOR-3). All three clones were expressed in CHO cells and characterized with regards to their binding profiles for orphanin FQ/nociceptin (OFQ/N) and a variety of opioids as well as their functional activities in cyclase studies. 125I[Tyr14]OFQ/N labels both KOR-3 (KD 37 pM) and the MOR-1/KOR-3 chimera (KD 39 pM) equally well. Although its affinity for the DOR-1/KOR-3 chimera is quite good (KD 135 pM), it is slightly lower than the other two. Competition studies confirm the high affinity of OFQ/N for all three clones. However, several competitors clearly distinguish the chimeras from KOR-3. OFQ/N(1-11) competes KOR-3 (Ki 55 nM) over 6-fold more potently than either of the chimeras. (Ki values > 350 nM). Conversely, the modest affinity of naloxone benzoylhydrazone for KOR-3 (310 nM) is greatly increased in both the MOR-1/KOR-3 (Ki 69 nM) and DOR-1/KOR-3 (Ki 74 nM) chimeras. The remainder of the opioids tested have no appreciable affinity against any of the clones. Functionally, OFQ/N inhibits forskolin-stimulated cAMP accumulation in both the KOR-3 and the MOR-1/KOR-3 chimera by almost 40%, with IC50 values in the low nanomolar range. Little activity is seen against the DOR-1/KOR-3 chimera. Naloxone benzoylhydrazone inhibits cAMP accumulation in the KOR-3 and the DOR-1/KOR-3 chimera. Although naloxone benzoylhydrazone has higher affinity for the MOR-1/KOR-3 chimera in binding studies than KOR-3 itself, it is inactive in cyclase studies using the MOR-1/KOR-3 chimera, implying that the replacement of the first coding exon increases affinity while decreasing intrinsic activity.

Animals↗
PubMed1996

Hypersomnia following paramedian thalamic stroke: a report of 12 patients.

Paramedian thalamic stroke (PTS) is a cause of organic hypersomnia, which in the absence of systematic sleep-wake studies has been attributed to disruption of ascending activating impulses and considered a "dearoused" state. However, an increasing mount of data suggests a role of the thalamus in sleep regulation and raises the possibility that a sleep disturbance contributes to hypersomnia in PTS. We evaluated 12 patients with magnetic resonance imaging-proven isolated PTS and hypersomnia with 10 to >20 hours of sleep behavior per day. Nocturnal polysomnographic findings paralleled the severity of hypersomnia. All subjects had increased stage 1 NREM sleep, reduced stage 2 NREM sleep, and reduced numbers of sleep spindles. In patients with severe hypersomnia, slow-wave (stages 3-4) NREM sleep was often reduced, but there were no major REM sleep alterations. Daytime sleep behavior was associated mostly with stage 1 sleep by electroencephalogram; there was no correlation between hypersomnia and results of nap tests. We conclude that hypersomnia following PTS is accompanied by deficient arousal during the day and insufficient spindling and slow-wave sleep production at night. These observations support the hypothesis of a dual role of the paramedian thalamus as "final common pathway' for both maintenance of wakefulness and promotion of NREM sleep.

Adolescent↗
PubMed1996

The perception of movements elicited by magnetic cortex stimulation depends on the site of stimulation.

Previous reports suggest that magnetic cortical stimulation (MCS) of the motor cortex can elicit a sensation of movement (kinaesthesia) in paralysed limbs. To assess this sensory effect of MCS, we examined the accuracy of kinaesthetic perception of stimulus-induced right elbow flexion in six blindfolded, healthy subjects. Matching of movements elicited by MCS was compared with matching of passive elbow movements. Small flexion movements between 1.5 and 5 degrees of angle were regularly overestimated by 50-100% when induced by MCS over the parietal cortex, whereas movements elicited by MCS over the frontal cortex or by passive elbow flexion were accurately estimated. Our results provide data compatible with the hypothesis of the existence of a "central sense of movement". Activation of collateral branches projecting from the motor cortex to the sensory could be the underlying mechanism to this phenomenon.

Adult↗
PubMed1996

Facilitation of motor evoked potentials by postcontraction response (Kohnstamm phenomenon).

We have applied repeated transcranial magnetic stimuli during the involuntary postcontraction muscle activity (Kohnstamm phenomenon) or during a tonic vibration reflex, both presumably arising from subcortical levels. The motor evoked potentials (MEPs) were compared with the MEPs evoked during a comparable voluntary contraction (cortical origin). The MEP amplitudes from the deltoid muscle appeared linearly related to the mean amplitude of the smoothed rectified background EMG preceding the stimulus. No differences in the facilitatory effect between voluntary and involuntary preinnervation manoeuvres were found. If we accept the hypothesis of a subcortical origin of the involuntary muscle activity in the Kohnstamm phenomenon, the similar facilitatory effect of involuntary and voluntary background EMG supports a predominantly spinal localisation of the facilitatory mechanism in this proximal muscle both during involuntary and during voluntary activity, at least under the present conditions of rather low stimulus strengths. In about 20-30% of all the trials an extra facilitatory effect on the MEP amplitude was observed during the shortening contraction compared to an MEP elicited during the lengthening contraction, in spite of a similar background EMG. This extra facilitatory effect of the shortening contraction was observed during involuntary and voluntary preactivation, suggesting an elevated excitatory state at the spinal level.

Adult↗
PubMed1996

Early prognosis in coma after cardiac arrest: a prospective clinical, electrophysiological, and biochemical study of 60 patients.

BACKGROUND: The univariate study of clinical, electrophysiological, or biochemical variables has been shown to predict the outcome in postanoxic coma in about 50% of patients for each type of variable. Previous studies did not, however, consider the prognostic accuracy of a multivariate approach. METHODS: Sixty patients in coma for more than six hours after cardiac arrest were prospectively examined by means of repeated clinical examinations (including Glasgow coma score (GCS)), EEG, and medianus nerve somatosensory evoked potentials (SEPs). In 16 patients, the early concentrations of serum neuron specific enolase and ionised calcium were also measured. RESULTS: Within the first year after cardiac arrest, 20% of patients made a good neurological recovery; 80% remained in a vegetative state or died. Clinical examination correctly predicted outcome in 58% of patients, SEP in 59%, and EEG in 41%. The combination of clinical examination, SEP, and EEG raised the percentage of correct predictions to 82%, without false pessimistic predictions. Concentrations of serum neuron specific enolase and ionised calcium were of no additional prognostic help. Multivariate regression analysis identified the association of GCS < 8 at 48 hours with abnormal or absent early cortical SEPs as highly predictive of a bad outcome (risk = 97%, 95% confidence interval = 86-99%). CONCLUSION: The combination of GCS at 48 hours, SEP, and if these are non-conclusive, EEG, permits a more reliable prediction of outcome in postanoxic coma than clinical examination alone.

Adult↗
PubMed1995

[The history of sleep research in the 20th century].

Not until the 19th century theories on sleep were based upon experimental findings in animal and humans. The so-called 'hypnotoxin theory' culminated, when Legendre and Piéron successfully induced sleep in a dog by transmission of cerebrospinal fluid from a dog deprived of sleep. The main discussion concerning the origin of sleep has been the question if sleep is a passive or an active state. Similarities with coma, the positive Babinski sign and pathoanatomical findings in patients who died after encephalitis lethargica were the arguments for the 'deafferentiation hypothesis'. Bremer's classical brainstem-transsections in cats confirmed this idea. Pavlov was the major representative of the idea that sleep was due to a general inhibition of the brain. Hess induced physiological sleep in cats by electrical stimulation of the diencephalon, proving the active nature of sleep. The introduction of the EEG in animals by Caton and in humans by Berger allowed for the first time the measurement of sleep depth without waking the sleeper. After discovery of the REM sleep periods by Aserinsky and Kleitman in 1953 and the demonstration of periodical sleep cycles by Dement and Kleitman, polysomnography with simultaneous whole night recording of EEG, EMG, electrooculogram and other physiological parameters was established as the major diagnostic tool in sleep disorders. One of the most important questions about the function of sleep is still unresolved. NREM sleep is believed to have a restorative function, whereas REM sleep might be involved in learning processes. According to the sleep interpretation of Sigmund Freud, the dream content represents endogenous wishes which cannot be expressed during wakefulness because of an internal 'sensor'. A more recent theory by Hobson explains the dreams by a very unspecific brainstem activity occurring during REM sleep which projects to the frontal brain and activates stored memory. The most important sleep disease of the 20th century is certainly the sleep-apnea syndrome. Charles Dickens described in his 'Pickwick Papers' subjects with this illness already 150 years ago. The pathogenetic significance of the apneas during sleep, however, were recognized in 1965 only by Gastaut and at the same time by Jung and Kuhlo. Treatment for insomniacs was restricted for many years to alcohol, opium and barbiturates. Following the horrible sequelae of thalidomide therapy in 1956, a more efficient treatment was available through the introduction of benzodiazepines after 1960.

Animals↗
PubMed1995

[Screening for sleep apnea: clinical use of Mesam IV and Apnoe-Check].

With the introduction of nasal continuous positive airway pressure as an effective treatment of the sleep apnea syndrome, the demand for costly polysomnographic investigations has markedly increased. Hence a reliable screening method would be desirable. Patients undergoing overnight oxymetry were simultaneously examined by MESAM (n = 54) and by Apnoe-Check (n = 23) in a prospective manner. The results were compared among themselves and with the complete overnight polysomnography (MESAM n = 38, Apnoe-Check n = 20). Simple overnight oxymetry, automatically assessed oxymetry by MESAM and apnea identification by Apnoe-Check correlated well with the polysomnographic findings. On the other hand, variation of heart rate, snoring events and changes of body position as identified by MESAM did not add relevant information. Only the detection of moderate to severe sleep apnea syndrome was satisfactory, though not infallible. Thus, there is still no screening method available to identify or exclude sleep apnea syndrome, particularly the milder form, which is nevertheless a significant disease.

Adult↗
PubMed1995

The boundary effect in magnetic stimulation. Analysis at the peripheral nerve.

The optimal stimulus position for a figure-8-shaped coil for magnetic stimulation of the ulnar nerve at the wrist was not coincident with the optimal electrical stimulus point but was shifted 18.3 mm to the ulnar side (P < 0.01). For the median nerve the optimal stimulus site was 9.6 mm radial to the optimal position for electrical stimulation (P < 0.05). This shift of the stimulus point for magnetic stimulation is significantly smaller after interposition of a homogenous electrically conducting medium between coil and arm but not changed after interposition of distilled water. This so-called boundary effect is therefore due to the different conductivities of the medium interposed between coil and nerve. It may also distort precise localisation of other excitable structures such as cranial nerves, nerve roots and cortical areas by means of magnetic stimuli. The amplitudes of the compound muscle action potentials elicited with identical magnetic stimulus strength were larger after the interposition of isotonic solution between coil and skin but not after interposition of distilled water. Consideration of the boundary effect provided an improved response amplitude to magnetic stimulation, but this could not adequately compensate for its poor localisation compared to electrical stimulation.

Adult↗
PubMed1995

Accuracy of an intelligent CPAP machine with in-built diagnostic abilities in detecting apnoeas: a comparison with polysomnography.

BACKGROUND: In patients with sleep apnoea early diagnostic evaluation and treatment may be delayed due to limited access to full polysomnography (PSG). For "typical" patients, simplified strategies are needed. A study was performed to evaluate the accuracy of a new continuous positive airway pressure (CPAP) device with in-built diagnostic abilities (Autoset) in detecting apnoeas. METHODS: Twenty seven patients underwent full overnight polysomnography. Data with the Autoset were acquired simultaneously. Standard nasal prongs were used. Apnoeas were detected by special analysis of the flow signal. As the Autoset derives all its data from one signal, careful examination of the raw data is important to assess the quality of the flow signal. RESULTS: There was a correlation between the apnoea index (AI) assessed by the Autoset (AI-Autoset) and by polysomnography AI-PSG (r = 0.85) and between the AI-Autoset and the apnoea/hypopnoea index (AHI) during polysomnography (r = 0.87). The Autoset identified patients with an AHI-PSG of > 20 (a level of respiratory disturbance that would warrant consideration for treatment in most centres for sleep disorders) with a sensitivity of 82% and a specificity of 90%. CONCLUSIONS: The good correlation between the apnoea index measured by the Autoset and by polysomnography, and the high sensitivity in detecting patients with an AHI of > 20, may make the Autoset a valuable tool for the management of typical patients with sleep apnoea. However, very low values for nasal ventilation on the printout raises the suspicion of poor signal quality and misleading results.

Adult↗
PubMed1994

Assessment of motor pathways to masticatory muscles: an examination technique using electrical and magnetic stimulation.

To study motor pathways to masticatory muscles, a new recording technique using surface electrodes was developed. The recording electrode was mounted on a spatula and inserted enorally into the pterygomandibular plica over the belly of m. masseter. Using this technique, mean latencies/amplitudes of the compound action potentials (CMAPs) in 18 healthy subjects were 1.2 ms/4.9 mV after electrical stimulation of the trigeminal nerve below the zygomatic arch, and 5.5 ms/1.1 mV after magnetic stimulation of the cortex. In 15 patients with unilateral lesions of the facial nerve, masticatory CMAPs had virtually symmetrical configuration, latency, and amplitude, excluding a major contribution of volume conducted activity from other cranial muscles. The technique was evaluated in patients after surgical treatment for trigeminal neuralgia. Patients with retrogasserian thermocoagulation and central demyelinating lesions were consistently identified.

Action Potentials↗
PubMed1994

A validation study on the intraobserver reproducibility of transcranial color-coded duplex sonography velocity measurements.

Transcranial color-coded duplex sonography (TCCD) is a new method for the measurement of angle-corrected intracranial blood velocities. The insonation angle represents the most important technical variable affecting Doppler velocimetry. The present study was designed to evaluate the intraobserver reproducibility of TCCD for repeated examinations of blood velocity in the anterior, middle and posterior cerebral, basilar and vertebral arteries. Three examinations were performed by the same examiner in each of 20 healthy volunteers within 10 days, with a minimal interval of 2 days between two subsequent examinations. The observer was blinded to previous results. The reproducibility was evaluated by calculating the correlation coefficient (r) and the coefficient of variance (CV) of the difference between the values obtained from the second and the third examination vs. the first examination. The results showed good reproducibility of TCCD velocity measurements in all examined arteries: for maximal systolic velocity r was 0.80-0.94 (p < 0.001), and CV was 5.5-9.4%; for maximal end-diastolic velocities r was 0.89-0.94 (p < 0.001), and CV was 6.6-12.2%.

Adult↗