Recognition of the Martin-Gruber anastomosis.
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Action Potentials↗
Biomedical subjects
J G van Dijk
Publications and source records attributed to J G van Dijk.
The effects of clonazepam and vigabatrin in hyperekplexia.
Hyperekplexia is an autosomal dominant disorder caused by a point mutation in the alpha1 subunit of the glycine receptor, characterized by excessive startle responses followed by temporary generalized stiffness. Clonazepam, effective in open case studies, potentiates, through unknown mechanisms, the neurotransmitter gamma-aminobutyric acid (GABA). Vigabatrin increases GABA by inhibition of the GABA catabolic enzyme GABA-transaminase. Effects of clonazepam (1 mg for 1 day) and vigabatrin (1000 mg per day for 5 days) were investigated in a double-blind placebo-controlled cross-over study in 4 patients with hyperekplexia. The pharmacodynamic parameters were startle reflexes, studied 3 times during the day. At each time, 2 trains of 10 auditive stimuli (113 dB) were given at intervals of 10 and 60 s. Startle movements were quantified with summed areas of EMG-bursts of the orbicularis oculi, sternocleidomastoid, biceps and thenar muscles. The degrees of stiffness and drowsiness were quantified with visual analogue scores (VAS) 10 times during the day, by both the patient and the observer. Clonazepam, but not vigabatrin, reduced startle activity significantly in both paradigms. The degree of stiffness and drowsiness was not significantly influenced by either drug.
Acoustic Stimulation↗
When to stop treatment in comatose patients after successful cardiopulmonary resuscitation? A practical approach.
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Cardiopulmonary Resuscitation↗
Hyperekplexia-like syndromes without mutations in the GLRA1 gene.
Hyperekplexia (MIM: 149400), or startle disease, is an autosomal dominant neurological disorder characterized by an extreme generalized stiffness immediately after birth, normalizing during the first years of life. Other features of this disorder are excessive startle reactions to unexpected, particularly auditory, stimuli together with a short period of generalized stiffness during which voluntary movements are impossible. Linkage analysis mapped a gene for this disorder to chromosome 5q33-q35. Subsequently, mutations in the GLRA1 gene encoding the alpha 1-subunit of the glycine receptor proved to be causally related to the disease. In the present study, mutation analysis of all exon and flanking intron sequences of this gene was performed in sporadic patients and their parents. Moreover, a branch of the original Dutch hyperekplexia family with a very severely affected individual was screened for an additional mutation in the GLRA1 gene. Except for two polymorphisms, of which one results in an amino acid change, no potentially disease causing mutations were found in the alpha 1-subunit of the glycine receptor. Together with haplotype analysis these results exclude a recessive inheritance or new mutation etiology in these hyperekplexia-like syndrome and emphasize that hyperekplexia-like syndromes can be caused by other genetic factors. The involvement of other genes encoding subunits of the functional glycine receptor complex has not been excluded.
Adult↗
Periodic fever associated with intermittent rhythmic delta activity: a syndrome of hypothalamic origin?
We report the case of a patient with a 16 year history of periodic (30 day cycle) fever attacks. The infradian cycle, associated clinical features, and the findings of electroencephalogram recorded during two fever attacks suggest a periodic hypothalamic syndrome.
Aged↗
Sleep scoring at a lower resolution.
Sleep scoring of whole-night polysomnograms is labor intensive. Scoring fewer epochs saves labor at the cost of accuracy; this study investigates the trade-off between the two. Whole-night sleep measures of 12 patients with sleep apnea syndrome, 10 patients with narcolepsy, and 35 controls were first computed using conventional successive 30-second epochs. Using the resulting list of sleep stages, a variable number of epochs was skipped among remaining epochs; the measures were recomputed for the reduced lists. The Bland-Altman analysis was used to define the agreements among the sleep measures at the conventional resolution and those at the lower resolutions. Scoring one-half to one-third of the number of epochs changes the duration of sleep stages only up to 2.5% and 5%, respectively, for all groups and sleep stages. In apnea patients, rapid eye movement (REM) latency deviates < 15 minutes when half of the epochs are scored. In controls and narcoleptics, much lower resolutions can be used before reaching the same level. Potential restrictions for the application of the method are discussed.
Adolescent↗
Evolution of epilepsy and EEG findings in Angelman syndrome.
PURPOSE: To evaluate the evolution of epileptic seizures and EEG features in a large group of patients with Angelman syndrome (AS). METHODS: Thirty-six patients with AS with a proven chromosome 15q11-13 deletion were retrospectively analyzed with regard to their epilepsy and EEG findings by examination of patient files and EEGs. AIJ EEGs were reviewed by one of the authors. A logistic regression model, with a follow-up from 1 to 39 years (mean, 15 years), was used for statistical analysis. RESULTS: Epileptic seizures had occurred in 30 (83%) patients. In 43% of them, the initial symptoms of epilepsy were febrile convulsions in infancy. In childhood, epilepsy could start with almost any type of seizure. Atypical absences and myoclonic seizures prevailed in adulthood. Epileptic seizures were present in 92% of the adult patients. The most typical EEG findings were rhythmic triphasic delta waves of high amplitude with a maximum over the frontal regions, identified in 99 (66%) of 150 EEGs, and continuously or intermittently, in 30 (83%) of 36 patients with AS. In 47% it was present even before a clinical diagnosis of AS was considered. High-amplitude rhythmic 4-6/s slow activity, seen in 44 (29%) of 150 EEGs, was not present after the age of 12 years. CONCLUSIONS: In contrast to previous reports suggesting a decreasing frequency of epileptic seizures with age, we found that 92% of the adult patients with AS continued to have epileptic seizures. The most typical EEG finding in AS, in both children and adults, was the presence of frontal triphasic delta waves. In mentally retarded patients, this EEG pattern should point the physician in the direction of AS.
Adolescent↗
Interictal cortical excitability to magnetic stimulation in familial hemiplegic migraine.
We studied interictal cortical excitability with magnetic stimulation in controls, in patients with migraine with aura, and in patients with familial hemiplegic migraine (FHM), in which ictal hemiparesis occurs. Amplitudes (p < 0.05) and amplitude ratios (p < 0.01) revealed heightened excitability in migraine with aura when compared to controls. In patients with FHM, mean thresholds were higher (p < 0.001) and conduction times longer (p < 0.01) than in controls. In FHM, amplitudes were lower on the ictally paretic side of the body than on the other (p < 0.05). Patients with FHM may have increased interictal cortical excitability, complicated by decreased excitability of the affected side.
Adolescent↗
Nerve grafting from spinal cord to spinal nerve: a microsurgical technique in cats.
A ventral surgical approach is described for the grafting of autologous saphenous nerves between the spinal cord and the avulsed C7 ventral root in the cat. To overcome serious blood loss from the epidural venous plexus, the cats were hyperventilated (end tidal PCO2 to about 23 mmHg) and controlled hypotension was induced (mean arterial pressure to about 60 mmHg). After selective avulsion of the ventral rootlets C7 the saphenous grafts were implanted into the spinal cord and coaptated to the avulsed spinal nerve. The combination of advanced anesthetic methods and microsurgical techniques appeared to be mandatory to achieve a low surgical mortality. Regenerated axons were retrogradely traced using retrograde horseradish peroxidase (HRP), and their functional recovery was evaluated by means of electrophysiological methods.
Anesthesia↗
The startle pattern in the minor form of hyperekplexia.
BACKGROUND: The major and minor forms of hereditary hyperekplexia (HE) are characterized by excessive startle responses, which are accompanied by transient stiffness only in major HE; patients with major HE also have continuous stiffness during infancy. A point mutation has been identified for major HE in the gene encoding the alpha 1 subunit of the glycine receptor but not for minor HE. OBJECTIVE: To measure startle reflexes and autonomic responses in the major and minor forms of HE in the original Dutch HE pedigree. DESIGN: Startle reflexes and autonomic responses were studied with 3 series of 20 auditory stimuli with intervals of 10 seconds (at 90 and 113 dB) and 60 seconds (at 113 dB). SETTING: A university hospital neurologic department. PATIENTS: Four patients with minor and 9 patients with major HE (patient groups) (a part of the Dutch HE family pedigree) and 20 healthy controls (control group). MAIN OUTCOME MEASURES: Startle movements were quantified with latencies and areas of electromyographic bursts of the following 4 muscles: the orbicular muscle of the eye, the sternocleidomastoid muscle, the biceps muscle of the arm, and thenar muscles. Autonomic reactions were measured with psychogalvanic responses. RESULTS. The 4 muscles contracted in similar order in the groups. The onset latencies of the orbicular muscle of the eye, the sternocleidomastoid muscle, and the biceps muscle of the arm were significantly prolonged in patients with minor HE (P < .006). The frequencies of occurrence of the electromyographic bursts were not different in the minor HE and major HE groups, but they were significantly higher in both patient groups compared with those in the control group (P < .001). The magnitude of the startle responses did not differ between the 2 patient groups (P = .4), but it was larger in both patient groups than in the control group (P < .001). Startle habituation in the minor HE group was much weaker than in the major HE group (P < .001) or in the control group (P < .001). The size of psychogalvanic responses (P = .1) and the degree of habituation (P = .24) in the minor HE group did not differ from those in the major HE group. Compared with that in the control group, the size of psychogalvanic responses in the minor HE group was larger (P < .001) and they habituated stronger (P < .001). CONCLUSIONS: The differences in the startle pattern between major HE and minor HE agree with the clinical and genetic findings: only major HE constitutes part of the HE phenotype. The cause of the minor HE is, as yet, unknown.
Adult↗
Large electrodes improve nerve conduction repeatability in controls as well as in patients with diabetic neuropathy.
Recording site is an important cause of variability of compound muscle action potential (CMAP) and conduction parameters, which can be reduced by using large electrodes. Repeatability of CMAP and conduction parameters of conventional and large electrodes was compared in 16 controls and 17 diabetic neuropathic patients, using defined recording sites linked to anatomical landmarks. Right-sided median, peroneal, and tibial nerves were investigated twice with a 1-2 week interval by the same examiner. Compared to previous studies, conventional electrodes on strictly defined recording sites resulted in better repeatability: intraindividual coefficients of variation (CV) varied between 4% and 14.4% for all parameters. CV of conduction parameters, not published previously, was smaller than CV of CMAP parameters. The use of large electrodes improved repeatability further: large electrodes resulted in substantially smaller CV for duration, amplitude, area, and changes of amplitude and area over a length of nerve, which were reduced by 10%, 31%, 29%, 27%, and 16%, respectively. Patients had higher CV than controls; large electrodes reduced patient CV more than control CV, resulting in less contrast between groups. Strictly defined recording sites and large electrodes improve repeatability of motor conduction studies to relevant degrees: all CMAP and conduction parameters are suitable for longitudinal studies of neuropathic patients.
Action Potentials↗
Repetitive CMAPs: mechanisms of neural and synaptic genesis.
Repetitive compound muscle action potentials (R-CMAPs) occur when a single nerve shock excites muscle fibers repeatedly. "Double discharges" are due to intramuscular nerve reexcitation. "Synaptic" R-CMAPs, due to excess acetylcholine in the neuromuscular synapse, can occur in congenital myasthenia, the slow-channel syndrome, and acetylcholinesterase inhibition. Secondary nerve excitation can reexcite muscle fibers. Synaptic R-CMAPs in a patient consisted of two discharges. The second diminished during repetitive stimulation and began 3.5-4.0 ms after the first, which is slightly longer than the synapse-muscle refractory period. Neural R-CMAPs, due to ectopic nerve activity, occur in neuromyotonia (NMT). R-CMAPs in a patient consisted of about 20 discharges at 200-300 Hz. Studies in healthy subjects showed that such trains represent added single CMAPs. Impulse frequency in the patient lied close to the threshold of refractoriness. Refractoriness of the synapse-muscle cell assembly determines the characteristics of R-CMAPs regardless of the primary cause.
Action Potentials↗
Influence of dopaminergic medication on automatic postural responses and balance impairment in Parkinson's disease.
It is still unclear why balance impairment in Parkinson's disease (PD) often responds insufficiently to dopaminergic medication. We have studied this issue in 23 patients with idiopathic PD and 24 healthy controls. Our specific purposes were (a) to investigate the contribution of abnormal automatic postural responses to balance impairment in PD and (b) to assess the influence of dopaminergic medication on abnormal automatic postural responses and balance impairment. Standing subjects received 4 degrees "toe-up" rotational perturbations of a supporting forceplate. We bilaterally recorded posturally destabilizing medium latency (ML) responses from the stretched gastrocnemius muscles and functionally corrective long latency (LL) responses from the shortened tibialis anterior (TA) muscles. We also assessed changes in the center of foot pressure (CFP) and the center of gravity (COG). All patients were tested in the "off" and "on" phases. All controls were tested and retested after 1 h. During the off phase, we found enlarged ML amplitudes and diminished LL amplitudes in patients, together with a markedly increased posterior displacement of the COG. The abnormal ML and LL responses were partially responsible for the increased body sway in patients because the initial forward (destabilizing) displacement of the CFP was increased, while the subsequent backward displacement of the CFP (a measure of the corrective braking action of LL responses) was delayed. Abnormal late automatic or possibly more voluntary postural corrections also contributed substantially to the increased body sway. During the on phase, ML amplitudes were reduced in patients but remained increased compared with controls. LL amplitudes no longer differed between both groups due to a modest, possibly dopamine-related increase in patients and a simultaneous decrease in controls. The abnormal CFP displacement was only partially improved by dopaminergic medication. The later postural corrections were not improved at all. Consequently, the increased posterior COG displacement was not ameliorated during the on phase. We conclude that (a) a combination of abnormal automatic and perhaps more voluntary postural corrections contributes to increased body sway in PD and (b) dopaminergic medication fails to improve balance impairment in PD because early automatic postural responses are only partially corrected, while later occurring postural corrections are not improved at all. These electrophysiological results support clinical observations and suggest that nondopaminergic lesions play a significant role in the pathophysiology of postural abnormalities in PD.
Adult↗
Saccadic eye movements in idiopathic blepharospasm.
Visually guided saccades, memory-contingent saccades, and antisaccades were studied with an infra-red reflection technique in 12 patients with idiopathic blepharospasm and in controls. Latencies of the three kinds of saccades were prolonged. Peak velocities and gains did not differ. Our results indicate an initiation defect in the saccadic system, which may be localized in the caudate nucleus.
Adult↗
Interictal cortical hyperexcitability in migraine patients demonstrated with transcranial magnetic stimulation.
Cortical excitability to magnetic stimulation was investigated interictally in 10 patients with migraine with aura, 10 with migraine without aura and in 10 healthy volunteers. Thresholds, latencies and amplitudes of the magnetic-evoked potentials (MEPs) were measured from threshold to 100% stimulus intensity in 10% steps. Compound motor action potentials (CMAPs) evoked with supramaximal electrical stimulation of the ulnar nerve were used to calculate MEP/CMAP amplitude ratios. Thresholds and latencies of MEPs did not differ between patients and controls. MEP/CMAP amplitude ratios were significantly increased at all intensities in patients with migraine with aura (RM-ANOVA, p < 0.01) and without aura (p < 0.05) compared with controls. In migraine patients, MEP amplitudes and MEP/CMAP amplitude ratios were positively related to the frequency of migraine attacks (Spearman's r = 0.47, p < 0.01 and r = 0.56, p < 0.002, respectively). MEP parameters were not related to the side of the headache nor the aura, in either type of migraine, implying that both hemispheres are equally involved in migraine. Migraine with aura and, to a lesser extent, migraine without aura, are associated with increased interictal cortical excitability.
Action Potentials↗
Cortical excitability and response variability of transcranial magnetic stimulation.
The magnetic evoked potential (MEP) following transcranial magnetic stimulation is subject to several sources of variability. In this study, relationships between stimulus intensity and MEP latency, amplitude, duration, and area of the hypothenar muscles were assessed in 12 right- and 14 left-handed subjects. Effects of handedness, coil orientation, intensity of stimulation, and intersubject variability on these relationships were analyzed. The intraindividual variability was analyzed as the standard deviation (SD) and the coefficient of variation (CV) of four trials. The mean response threshold was significantly lower (p < 0.0001) for preferential stimulation (32%) than for nonpreferential stimulation (45%). With increasing stimulus intensities, MEP amplitudes still increased at 100% intensity in some subjects while in others the stimulus response-relations saturated. MEP amplitudes at an intensity of 20% above threshold ranged between 6 and 100% of MEP amplitude at maximum intensity. Differences between dominant and non-dominant hands were not seen, regardless of handedness. The SD of latency, amplitude, duration, or area depended on stimulus intensity. The CV however, was influenced by the intensity of stimulation: The CV for amplitude decreased from 46% at threshold to 10% at higher intensities. The variability of the MEP amplitude is only related to stimulus intensity when it is expressed in relation to it but not when it is expressed in absolute terms. The stimulus-response relation offers a more extensive measure of cortical excitability than the use of thresholds alone for the measurement of cortical excitability. The question can be raised whether high intensities should be used for clinical testing rather than threshold-related intensities.
Adult↗
The outcome of absence epilepsy: a meta-analysis.
We performed a meta-analysis of studies on absence epilepsy (AE) to ascertain whether the outcome of this well-defined type of epilepsy can be stated unequivocally. Using the Index Medicus and Medline CD+, we identified 1,619 publications. After applying the criteria of the International League against Epilepsy (ILAE) for AE, 26 publications on 23 study cohorts with a total of 2,303 patients were included. Remission rates ranged from 0.21 to 0.89; they differed substantially due to heterogeneity between the studies in inclusion criteria, methods, follow-up length, and outcome definitions. One half of the patients developed generalized tonic-clonic seizures (TCS) in the course of the disease. The proportion seizure free was 0.78 for patients with absence seizures (AS) only, and 0.35 for those who developed TCS. The outcome of AE may be worse than previously stated due to the considerable proportion of patients developing TCS in the course of their disease. Early prediction of outcome in patients who present with AS cannot be provided with certainty.
Adolescent↗
Reinnervation of avulsed and reimplanted ventral rootlets in the cervical spinal cord of the cat.
Spinal nerve root avulsions frequently occur in brachial plexus injuries caused by traction. Such lesions are considered to afflict the central nervous system (CNS) and are, therefore, believed to be beyond surgical repair. The present experimental study was initiated to challenge this hypothesis. The ventral rootlets of C-7 were avulsed from the spinal cord in 28 cats via an anterior approach and subsequently reimplanted into the cord at the site of origin. In nonoperated control cats and cats undergoing reimplantation, electrophysiological experiments were performed and horseradish peroxidase was administered to the spinal nerve on the reimplanted side after survival times ranging from 6 to 293 days. Spinal cord sections in all cats were stained for neurofilament, acetylcholinesterase (AChE), Nissl, and glial fibrillary acidic protein. Horseradish peroxidase-labeled ventral horn motoneurons were found as early as 14 days after reimplantation and their number increased with time. On Days 209 and 293, the number of labeled neurons equaled the number of labeled ventral horn neurons in the two control cats that did not undergo surgery. Starting on Day 6 after reimplantation, the appearance of the ventral horn and the white matter in the neurofilament, AChE, and Nissl-stained sections changed as a result of the CNS response to the injury. A return to their normal appearance could be observed in these stainings from Day 209 onward. Glial fibrillary acidic protein-positive astrocytic tissue was consistently found in the ventral horn and in the white matter reimplantation area. From Day 69 onward, electrophysiological stimulation of the spinal nerve C-7 on the reimplanted side elicited an electromyogram response in the spinodeltoid muscle. The latency and threshold intensity of the C-7 responses were initially increased but equalized to match the nonoperated controls between 98 and 122 days after reimplantation. The results of this study show that functional regeneration of ventral horn neurons after root avulsion and subsequent reimplantation in the cat is possible.
Acetylcholinesterase↗