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Biomedical subjects

J G van Dijk

Publications and source records attributed to J G van Dijk.

At least 37 records · Page 2Linked to original sources
PubMed2003

Impairment of trigeminal sensory pathways in cluster headache.

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

Adult↗
PubMed2002

Reproducibility and feasibility of neurophysiological assessment of the sensory trigeminal system for future application to paroxysmal headaches.

As the distribution of pain in primary headaches suggests involvement of the trigeminal sensory pathways, trigeminal somatosensory evoked potentials (TSEP) and blink reflexes (BR) may provide important information about their functional integrity. Functional differences between symptomatic and non-symptomatic sides and between measurements during and outside attacks may be particularly informative. These tests should therefore be reproducible and should require a suitable number of patients for future studies in patients with primary, paroxysmal headaches. We performed TSEP and BR twice in 22 healthy volunteers, in order to calculate sample sizes based on reproducibility data. This is, to our knowledge, the first study investigating the reproducibility of TSEP and BR measurements. Latencies of TSEP and BR are appropriate for future studies, as their reproducibility allows practical sample sizes (less than 25 subjects). Duration, amplitude and area parameters of the BR responses were less appropriate for longitudinal studies.

Adult↗
PubMed2001

Clinical aspects of multifocal or generalized tonic dystonia in reflex sympathetic dystrophy.

The authors describe 10 patients with reflex sympathetic dystrophy that progressed to a multifocal or generalized tonic dystonia. The neuropsychologic profile was similar to that of other patients with chronic pain, irrespective of its cause. The distribution pattern of dystonia, the stretch reflex abnormalities, and the worsening of dystonia after tactile and auditory stimuli suggest impairment of interneuronal circuits at the brainstem or spinal level. Antibody titers for glutamic acid decarboxylase, tetanus, and Sjögren antigens were all normal.

Adolescent↗
PubMed2001

Obstetric lesions of the brachial plexus.

The few studies on prognosis of obstetric lesions of the brachial plexus that are not hampered by selection bias or a short follow-up suggest that functional impairment persists in 20-25% of cases, more than commonly thought. Electromyography (EMG), potentially useful for prognosis, is often considered of little value. Denervation in the first week of life has been interpreted as evidence of an antenatal lesion, but is the logical result of the short axonal length affected. EMG performed at close to the time of possible intervention (3 months) usually shows a discrepancy: motor unit potentials are seen in clinically paralyzed muscles. This can be explained in five ways: an overly pessimistic clinical examination; overestimation of EMG recruitment due to small muscle fibers; persistent fetal innervation; developmental apraxia; or misdirection, in which axons reach inappropriate muscles. Further research into the pathophysiology of obstetric lesions of the brachial plexus is needed to improve prognostication.

Birth Injuries↗
PubMed2001

The multiple tasks test. Strategies in Parkinson's disease.

The clinical balance tests presently used cannot predict falls in Parkinson's disease (PD), perhaps because they probe fairly isolated "components" of postural control. The Multiple Tasks Test (MTT) is a new balance test that simultaneously assesses multiple components of postural control. We investigated whether this MTT can detect postural abnormalities in PD patients. Fifty young controls (mean age 27.6 years), 20 elderly controls (mean age 62.5 years), and 20 PD patients (mean age 61.8 years, mean Hoehn and Yahr stage 2.2) participated. The MTT consisted of eight separate tasks of increasing complexity, which were executed sequentially. These tasks were composed of several motor components (standing up, walking, avoiding obstacles, touching the floor, turning around, and sitting down) and one cognitive component (answering serial questions). Four additional components included carrying an empty or loaded tray, wearing slippery shoes, and reduced illumination. All components within each task had to be performed simultaneously or directly sequentially. Errors were defined as Hesitations (slowed performance) or Blocks (complete cessation), which were scored separately for execution of the motor and cognitive components. Speed of performance was not stressed, but we did measure the time taken to complete all tasks. The complete MTT was performed by all subjects, except for a subgroup of seven patients and seven elderly controls who performed a shortened version, with only three of the eight sequential tasks (simple, intermediate, and most difficult). The number of subjects that produced Hesitations or Blocks for the motor components differed between the three groups [two-way repeated measures MANOVA, F(2.7) = 20.56; P < 0.001], patients making more errors than young and elderly controls. Furthermore, the number of subjects that made motor errors increased as the tasks became more complex [F(2.7) = 6.69; P < 0.001]. This increase differed across the three groups [significant interaction effect; F(2.7) = 3.31; P < 0.001] because particularly patients produced motor errors during the more complex tasks. In both control groups, 62% performed all eight consecutive tasks without errors in the motor components. In contrast, only 8% of the patients completed all tasks without motor errors (log rank test, P < 0.0001). This difference between patients and controls disappeared if the cognitive component was also scored, because more controls made cognitive errors during complex tasks than patients. Controls apparently gave priority to execution of the motor components, which they performed significantly faster than the patients. Both patients and controls made more errors during the shortened MTT, suggesting that learning effects (gain in performance through practice) influenced performance on the complete test. The MTT is a new balance test that clearly discriminates between healthy subjects and PD patients. Unlike controls, PD patients lend less priority to motor tasks over cognitive tasks. In addition, impaired motor learning may partially explain the higher error rate in PD. Future studies must determine if impaired MTT performance can predict actual falls in daily life.

Adult↗
PubMed2001

Patients with the major and minor form of hyperekplexia differ with regards to disynaptic reciprocal inhibition between ankle flexor and extensor muscles.

The aim of the present study was to investigate the contribution of reciprocal inhibition to muscle tone by examining the transmission in the reciprocal inhibitory pathway in patients with a known defect in the glycine receptor. The study was performed in eight patients with hereditary hyperekplexia, six with the major form and two with the minor form of the disease. A mutation in the alpha1-subunit of the glycine receptor had been demonstrated in the patients with the major form, whereas no mutation was seen in the patients with the minor form. Disynaptic reciprocal inhibition, which is presumed to be mediated by glycine, was not seen in the patients with the major form of the disease, while it could be evoked in the patients with the minor form of the disease. Presynaptic inhibition, which is presumed to be mediated by GABA, was seen in both types of patients. It is concluded that the major form of hereditary hyperekplexia is associated with impaired transmission in glycinergic reciprocal inhibitory pathways. The findings demonstrate the importance of reciprocal inhibition for the muscle tone in man, and it is suggested that the impaired reciprocal inhibition seen in patients with a defect in the glycine receptor may contribute to the increased muscle stiffness that is observed in these patients.

Adult↗
PubMed2001

What is the best way to assess focal slowing of the ulnar nerve?

OBJECTIVE: The study assessed the influence of the length of the across elbow (AE) segment of the ulnar nerve on the true and false positive rates of velocity measurements of the AE segment. Using a short AE length will increase effects of the measurement error (ME), and using a long distance will 'dilute' the slowing due to the focal lesion; it is not known which length is optimal to detect focal slowing. METHODS: A simulation was performed to assess diagnostic yield for AE lengths of 50, 100 and 150 mm, taking into account ME, variation in true velocity, and severity of the lesion. ME of latencies and distances were first determined in a healthy subject. RESULTS: ME proved lower than in a published study. Diagnostic yield was consistently better for an AE length of 50 mm than for 100 or 150 mm. The optimum length is therefore near 50 mm. Yield increased with severity of the lesion, smaller ME, and when interindividual variation in true velocity was small. Judging AE on its own had a slightly better yield than comparing AE velocity to forearm velocity, except for populations with a larger than normal spread in true conduction variability. CONCLUSIONS: The best balance between effects of ME and 'dilution' to detect focal nerve slowing is obtained at nerve lengths of about 50 mm. The need to incorporate all possible compression sites necessitates the use of a suboptimal length of about 80 mm.

Computer Simulation↗
PubMed2001

A convenient method to reduce crosstalk in surface EMG. Cobb Award-winning article, 2001.

OBJECTIVES: Crosstalk in surface EMG can be reduced by the use of spatial filters. We compared a variety of spatial filters to establish the most effective and the least complex method to reduce crosstalk. METHODS: Six different spatial filters described in the literature were tested in 8 healthy volunteers. Electrode arrays were placed over the anterior tibial and triceps surae muscles. Selective muscle activation was achieved both by supramaximal nerve stimulation and by maximal voluntary contraction. Selectivity of activation was guaranteed by using intramuscular wire electrodes. Crosstalk was quantified by dividing the amount of EMG activity recorded during pure agonist activation (i.e. the muscle directly under the electrode array) by the EMG activity recorded during pure antagonist activation. This was done for both compound muscle action potentials and voluntary muscle activation. The amount of crosstalk recorded with the different spatial filters was compared with that recorded with a standard bipolar lead. RESULTS: Crosstalk was most reduced by the "double-differential" (DD) filter, yielding an up to 6-fold improvement of EMG selectivity. We then compared signals recorded with this DD filter with those recorded with the less complex "branched electrode". As expected on theoretical grounds, signals from both filter types were identical. CONCLUSIONS: Crosstalk is best reduced using a "double-differentiating" recording technique, which can be achieved easily using a branched electrode instead of a standard bipolar lead. This technique can be used with all conventional EMG equipment.

Action Potentials↗
PubMed2001

Narcolepsy: clinical features, new pathophysiologic insights, and future perspectives.

Narcolepsy is characterized by excessive daytime sleepiness and abnormal manifestations of rapid eye movement sleep such as cataplexy. The authors review the clinical features of narcolepsy, including epidemiology, symptoms, diagnosis, and treatment, in detail. Recent findings show that a loss of hypocretin-producing neurons lies at the root of the signs and symptoms of narcolepsy. The authors review the current state of knowledge on hypocretin anatomy, physiology, and function with special emphasis on the research regarding the hypocretin deficiency in narcolepsy, which may also explain associated features of the disorder, such as obesity. Lastly, they discuss some future perspectives for research into the pathophysiology of sleep/wake disorders, and the potential impact of the established hypocretin deficiency on the diagnosis and treatment of narcolepsy.

Age of Onset↗
PubMed2000

Effects of startle and laughter in cataplectic subjects: a neurophysiological study between attacks.

OBJECTIVES: Cataplexy, when unequivocally present together with excessive daytime sleepiness, is diagnostic for narcolepsy. Unfortunately, it is difficult to induce cataplexy during consultation. In this study we tried to assess presumed subclinical expressions of cataplexy using neurophysiological tests. METHODS: In this controlled explorative study, we studied 14 patients with a clear history of cataplexy and 12 matched controls using standard H-reflex, H/M ratios, audiospinal reflex, H-reflexes modulated by emotions and startle reflexes. RESULTS: H-reflexes were attenuated during laughter in patients as well as controls. Startle reflexes were increased in patients. Audiospinal reflexes were not influenced. CONCLUSIONS: The patterns found add relevant knowledge concerning pathophysiological mechanisms and involved brain areas in cataplexy, and may reflect subclinical expressions of cataplexy. The presumed specificity of the abolishment of H-reflexes during cataplectic attacks is questioned by our findings. The exaggerated startle reflex is in line with recent findings concerning involved brain areas in narcolepsy.

Acoustic Stimulation↗
PubMed2000

Repetitive nerve stimulation: effects of recording site and the nature of 'pseudofacilitation'.

OBJECTIVES: To describe changes in the waveform of the compound muscle action potential (CMAP) during repetitive nerve stimulation for various recording sites. METHODS: Responses to trains of 10 stimuli given at 0.1, 1, 3, 5, 10 and 30 Hz to the ulnar nerve were recorded simultaneously from 8 hand sites in 15 healthy subjects. Percentile changes of amplitude, duration and area of both negative and positive phases were analyzed. RESULTS: Duration consistently decreased during the trains. At 30 Hz, the mean amplitude of the negative phase increased on 5 sites but decreased on 3. Area consistently decreased, but least for hypothenar sites. Repeated stimulation causes an alteration in the waveform of the CMAP that consists of 4 elements: (1) shorter duration; (2) changed amplitude of the negative phase (up or down); (3) merging of bifid peaks; (4) changes were more pronounced for positive than negative phases. CONCLUSIONS: As the term 'pseudofacilitation' implies an increase in amplitude, it is often not appropriate. Increased muscle fiber conduction velocity can explain most of the waveform alterations. Movement and shortening of muscles may play additional roles. Consequences for diagnostic yield await a comparison with disease groups.

Action Potentials↗
PubMed2000

'Rules of conduct': some practical guidelines for testing motor-nerve conduction.

The testing of nerve conduction using electromyography (EMG) is a frequently used diagnostic method for the identification of various neuropathies. The present article illustrates a variety of conditions on the basis of clinical data, and suggests how one can obtain the best results by observing a few simple rules.

Body Temperature↗
PubMed2000

Long-term results of anterior anal sphincter repair for fecal incontinence due to obstetric injury / with invited commentaries.

AIMS: This study is to report short- and long-term results of anterior sphincter repair for fecal incontinence due to obstetric injury and factors predicting an unsuccessful outcome. METHODS: Thirty-nine consecutive patients, mean age 51 years (range 29-74), who underwent anterior sphincter repair for fecal incontinence due to obstetric injury were investigated. Duration of symptoms ranged from 9 months to 34 years. All patients underwent an anterior overlapping sphincter muscle reconstruction and in most cases a puborectal muscle plasty. RESULTS: Three months after surgery 77% of the patients had regained continence (Parks score of 1 or 2), at 9 months 67% were continent and after 12 months or more (mean, range 12-114) only 62%. Patients with prolonged pudendal latency (>2.2 ms) did significantly worse than patients without it (p < 0.05). Patients who had had lateral episiotomy during labor had significantly better outcome than those without it (p < 0.05). CONCLUSION: The outcome of anterior sphincter repair deteriorates with time after surgery. Assessment should be done at least 1 year after surgery to evaluate the final results of anterior sphincter repair. Prolonged pudendal latency predicts a poor outcome of anterior sphincter repair, and a prior lateral episiotomy is possibly a good prognostic factor.

Adult↗
PubMed2000

Neurophysiological evidence of increased cortical reactivity in migraine.

Cortical reactivity in migraine can be studied with evoked potentials. The majority of the evidence shows increased reactivity in migraine, which may be due to abnormal inhibition. At present, the techniques are not useful for diagnosis. Discrepancies between reports may be due to fluctuations in reactivity over time. Documenting this changing reactivity requires refinement of analysis techniques.

Cerebral Cortex↗
PubMed2000

Clinical and para-clinical tests in the routine examination of headache patients.

Para-clinical examinations in the diagnosis and treatment control of headache patients vary considerably between clinics and headache centers. Among the neurological societies in Europe there has been a consensus that some common procedures and recommendations should be created. In the Fall of 1998, the European Federation of Neurological Societies (EFNS) commissioned a Task Force on Neurophysiological Tests and Imaging Procedures in Headache Patients. Members of the Task Force are the present authors and we have reviewed the literature on 1) neurophysiological tests (EEG and evoked potentials), 2) autonomic nervous system and clinical tests and 3) imaging and cerebrovascular tests (X-ray, CT, MR, fMRI, PET, SPECT and transcranial Doppler). The literature was carefully evaluated with respect to validity and strength of the data. The task was to reach conclusions about each technique in the form of guidelines for clinical use. Finally, selected areas for future research will be outlined. The extensive review and the guidelines will be published by the EFNS during 2000.

Electroencephalography↗