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Biomedical subjects

P S Sándor

Publications and source records attributed to P S Sándor.

At least 19 recordsLinked to original sources
PubMed2006

EFNS guideline on the drug treatment of migraine - report of an EFNS task force.

Migraine is one of the most frequent disabling neurological conditions with a major impact on the patients' quality of life. To give evidence-based or expert recommendations for the different drug treatment procedures of the different migraine syndromes based on a literature search and an consensus in an expert panel. All available medical reference systems were screened for all kinds of clinical studies on migraine with and without aura and on migraine-like syndromes. The findings in these studies were evaluated according to the recommendations of the EFNS resulting in level A,B, or C recommendations and good practice points. For the acute treatment of migraine attacks, oral non-steroidal anti-inflammatory drugs (NSAIDs) and triptans are recommended. The administration should follow the concept of stratified treatment. Before intake of NSAIDs and triptans, oral metoclopramide or domperidon is recommended. In very severe attacks, intravenous acetylsalicylic acid or subcutaneous sumatriptan are drugs of first choice. A status migrainosus can probably be treated by steroids. For the prophylaxis of migraine, betablockers (propranolol and metoprolol), flunarizine, valproic acid, and topiramate are drugs of first choice. Drugs of second choice for migraine prophylaxis are amitriptyline, naproxen, petasites, and bisoprolol.

Advisory Committees↗
PubMed2006

EFNS guidelines on the treatment of cluster headache and other trigeminal-autonomic cephalalgias.

Cluster headache and the other trigeminal-autonomic cephalalgias [paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) syndrome] are rare but very disabling conditions with a major impact on the patient's quality of life. The objective of this study was to give evidence-based recommendations for the treatment of these headache disorders based on a literature search and consensus amongst a panel of experts. All available medical reference systems were screened for any kind of studies on cluster headache, paroxysmal hemicrania and SUNCT syndrome. The findings in these studies were evaluated according to the recommendations of the European Federation of Neurological Societies resulting in level A, B or C recommendations and good practice points. For the acute treatment of cluster headache attacks, oxygen (100%) with a flow of at least 7 l/min over 15 min and 6 mg subcutaneous sumatriptan are drugs of first choice. Prophylaxis of cluster headache should be performed with verapamil at a daily dose of at least 240 mg (maximum dose depends on efficacy or tolerability). Although no class I or II trials are available, steroids are clearly effective in cluster headache. Therefore, the use of at least 100 mg methylprednisone (or equivalent corticosteroid) given orally or at up to 500 mg i.v. per day over 5 days (then tapering down) is recommended. Methysergide, lithium and topiramate are recommended as alternative treatments. Surgical procedures, although in part promising, require further scientific evaluation. For paroxysmal hemicranias, indomethacin at a daily dose of up to 225 mg is the drug of choice. For treatment of SUNCT syndrome, large series suggest that lamotrigine is the most effective preventive agent, with topiramate and gabapentin also being useful. Intravenous lidocaine may also be helpful as an acute therapy when patients are extremely distressed and disabled by frequent attacks.

Advisory Committees↗
PubMed2006

Normobaric hypoxia and nitroglycerin as trigger factors for migraine.

Migraine prevalence is increased in high-altitude populations and symptoms of acute mountain sickness mimic migraine symptoms. Here we tested whether normobaric hypoxia may trigger migraine attacks. As positive control we used nitrolgycerin (NTG), which has been shown to induce migraine attacks in up to 80% of migraineurs. Sixteen patients (12 females, mean age 28.9 +/- 7.2 years) suffering from migraine with (n = 8) and without aura (n = 8) underwent three different provocations (normobaric hypoxia, NTG and placebo) in a randomized, cross-over, double dummy design. Each provocation was performed on a separate day. The primary outcome measure was the proportion of patients developing a migraine attack according to the criteria of the International Headache Society within 8 h after provocation onset. Fourteen patients completed all three provocations. Migraine was provoked in six (42%) patients by hypoxia, in three (21%) by NTG and in two (14%) by placebo. The differences among groups were not significant (P = 0.197). The median time to attacks was 5 h. In conclusion, the (remarkably) low response rate to NTG is surprising in view of previous data. Further studies are required to establish fully the potency of hypoxia in triggering migraine attacks.

Adult↗
PubMed2005

Efficacy of coenzyme Q10 in migraine prophylaxis: a randomized controlled trial.

Riboflavin, which improves energy metabolism similarly to coenzyme Q10 (CoQ10), is effective in migraine prophylaxis. We compared CoQ10 (3 x 100 mg/day) and placebo in 42 migraine patients in a double-blind, randomized, placebo-controlled trial. CoQ10 was superior to placebo for attack-frequency, headache-days and days-with-nausea in the third treatment month and well tolerated; 50%-responder-rate for attack frequency was 14.4% for placebo and 47.6% for CoQ10 (number-needed-to-treat: 3). CoQ10 is efficacious and well tolerated.

Adult↗
PubMed2005

MR-spectroscopic imaging during visual stimulation in subgroups of migraine with aura.

Migraine pathophysiology possibly involves deficient mitochondrial energy reserve and diminished cortical habituation. Using functional magnetic resonance spectroscopic imaging (fMRSI), we studied cortical lactate changes during prolonged visual stimulation to search for different pathophysiological mechanisms in clinically distinct subgroups of migraine with aura. Eleven healthy volunteers (HV) and 10 migraine patients were investigated interictally: five with visual aura (MA) and five with visual symptoms and at least one of the following: paraesthesia, paresis or dysphasia (MAplus). Using MRSI (Philips, 1.5 T) (1)H-spectra were repeatedly obtained from a 25 mm-thick slice covering visual and non-visual cortex, with the first and fifth measurements in darkness and the second to fourth with 8-Hz checkerboard stimulation. In MAplus lactate increased only during stimulation, only in visual cortex; in MA resting lactate was high in visual cortex, without further increase during stimulation. This is compatible with an abnormal metabolic strain during stimulation in MAplus, possibly due to dishabituation, and a predominant mitochondrial dysfunction in MA.

Adult↗
PubMed2005

Blinking and schizotypal thinking.

Spontaneous eye blink rate (SBR) is thought to be a biological marker for cerebral dopamine (DA) activity. Accordingly, positive psychotic symptoms have been found to be associated with an increased SBR and negative psychotic symptoms with a decreased SBR. However, modulations of the DA system in patient populations also result from prior neuroleptic treatment. Here, we tested the possible relationship between SBR and positive and negative schizotypal thought. To test the direct influence of DA on SBR in general and as a function of schizotypy, half of a sample of 40 healthy men received levodopa and the other half placebo in a double-blind procedure. SBR did not differ between substance groups suggesting that a pharmacologically induced DA increase in healthy individuals does not generally increase SBR. However, in the levodopa group, increasing SBR correlated with increasing negative schizotypy scores, while no relationship was found between SBR and (1) negative schizotypy in the placebo group, or (2) positive schizotypy in either substance group. We conjecture that a pre-existing hypodopaminergic state in high negative schizotypy scorers, made these individuals susceptible to an increased DA concentration, as it has been observed in Parkinson's disease. Furthermore, the absence of any relationship in the placebo group might suggest that variations in DA concentration as a function of schizotypy are too subtle to influence SBR. Finally, the lack of any association of SBR with positive schizotypy might indicate that SBR and positive schizotypy are mediated by functionally distinct neural circuits.

Adult↗
PubMed2003

Three-dimensional vestibular eye and head reflexes of the chameleon: characteristics of gain and phase and effects of eye position on orientation of ocular rotation axes during stimulation in yaw direction.

We investigated gaze-stabilizing reflexes in the chameleon using the three-dimensional search-coil technique. Animals were rotated sinusoidally around an earth-vertical axis under head-fixed and head-free conditions, in the dark and in the light. Gain, phase and the influence of eye position on vestibulo-ocular reflex rotation axes were studied. During head-restrained stimulation in the dark, vestibulo-ocular reflex gaze gains were low (0.1-0.3) and phase lead decreased with increasing frequencies (from 100 degrees at 0.04 Hz to < 30 degrees at 1 Hz). Gaze gains were larger during stimulation in the light (0.1-0.8) with a smaller phase lead (< 30 degrees) and were close to unity during the head-free conditions (around 0.6 in the dark, around 0.8 in the light) with small phase leads. These results confirm earlier findings that chameleons have a low vestibulo-ocular reflex gain during head-fixed conditions and stimulation in the dark and higher gains during head-free stimulation in the light. Vestibulo-ocular reflex eye rotation axes were roughly aligned with the head's rotation axis and did not systematically tilt when the animals were looking eccentrically, up- or downward (as predicted by Listing's Law). Therefore, vestibulo-ocular reflex responses in the chameleon follow a strategy, which optimally stabilizes the entire retinal images, a result previously found in non-human primates.

Adaptation, Physiological↗
PubMed2003

Electrophysiological studies in migraine: a comprehensive review of their interest and limitations.

Electrophysiological methods may help to unravel some of the pathophysiological mechanisms of migraine. Lack of habituation is the principal and most reproducible interictal abnormality in sensory processing in migraineurs. It is found in evoked potential (EP) studies for every stimulation modality including nociceptive stimuli, and it is likely to be responsible for the increased intensity dependence of EP. We have hypothesized that deficient EP habituation in migraine could be due to a reduced preactivation level of sensory cortices because of hypofunctioning subcortico-cortical aminergic pathways. This is not in keeping with simple hyperexcitability of the cortex, which has been suggested by some, but not all, studies of transcranial magnetic stimulation (TMS). A recent study of the effects of repetitive TMS on visual EP strongly supports the hypothesis that migraine is characterized by interictal cortical hypoexcitability. With regard to pain mechanisms in migraine, electrophysiological studies of trigeminal pathways using nociceptive blink and corneal reflexes have confirmed that sensitization of central trigeminal nociceptors occurs during migraine attacks.

Brain↗
PubMed2002

A neural network model of sensitization of evoked cortical responses in migraine.

Migraine patients show abnormalities of cerebral electrophysiology that manifest themselves mainly during the attack interval. Cortical-evoked potentials of migraineurs fail to habituate to repetitive presentations of visual stimuli, and the amplitude of components of their auditory cortical-evoked potentials have a higher dependence on the stimulus intensities than in healthy subjects. A computer model of a neural hetwork has been developed that is able to reproduce both these neurophysiological dysfunctions. It predicts a positive correlation between the magnitudes of both these dysfunctions. The model also offers an explanation of why mutations in the same ion channel gene with opposite consequences on channel function, e.g. P/Q Ca2+ channels in migraine, may lead to similar electrophysiological abnormalities.

Arousal↗
PubMed2001

Spatial- and verbal-memory improvement by cold-water caloric stimulation in healthy subjects.

We investigated the effects of unilateral cold-water vestibular stimulation on healthy subjects' performance in two cognitive tasks known to be differentially mediated by the two cerebral hemispheres. In a first experiment (right-hemisphere task), subjects memorized object-location associations while being stimulated with cold water in the left ear or right ear or not at all (control group). In the second experiment (left-hemisphere task), subjects memorized a list of sequentially presented function words while being stimulated in the same manner as the subjects in the first experiment. A recall phase followed each encoding phase. In the first experiment, subjects who had been stimulated in the left ear recalled the object locations significantly faster than subjects who had been stimulated in the right ear and those in the control group. The second experiment yielded the reverse pattern: correct word recognition was faster for subjects who had been stimulated in the right ear than for subjects stimulated in the left ear and those of the control group. We suggest that unilateral caloric stimulation leads to a selective activation of contralateral cerebral structures and speeds up cognitive processes mediated by these structures. These results are discussed with respect to findings in neglect patients and functional-imaging studies in healthy subjects.

Adult↗
PubMed2001

Chameleon eye position obeys Listing's law.

Listing's law (LL) states that 3D-eye positions lie in a plane, when they are described as single-axis rotations from the primary position. This implies that the degrees of freedom of eye movements are reduced from three to two. Various hypotheses exist, regarding the implementation of LL. These include facilitation of binocular vision, optimization of oculomotor control, and mechanical constraints in the orbit. We recorded the 3D-eye position during saccadic scanning in the chameleon, to investigate whether LL is valid in an animal with different anatomical and behavioral characteristics compared to primates. We show that in chameleons, the eye position obeys LL with a high precision. Since the anatomical arrangement of the orbit in chameleons is very different from that in primates, and binocular fused vision is virtually absent, we suggest that in the chameleon, LL mainly optimizes oculomotor control.

Animals↗
PubMed2001

Subclinical cerebellar impairment in the common types of migraine: a three-dimensional analysis of reaching movements.

Mutations in the CACNA1A gene can cause familial hemiplegic migraine (FHM) and/or cerebellar ataxia CACNA1A codes for the alpha1 subunit of P/Q-Ca2+ channels and is highly expressed in the cerebellum. Using a pointing paradigm and infrared optoelectronic tracking system, we found subclinical hypermetria and other subtle cerebellar signs in the common forms of migraine. These were more pronounced in migraine with than without aura. Whether this reflects involvement of Ca2+ channel genes in the common types of migraine needs to be investigated by genetic analyses.

Adult↗
PubMed2000

Comparison of visual and auditory evoked cortical potentials in migraine patients between attacks.

OBJECTIVE: As both habituation of pattern reversal visual evoked potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ. Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks. Eur J Neurol 1995;2:115-122) and intensity dependence of auditory evoked cortical potentials (IDAP) (Wang W, Timsit-Berthier M, Schoenen J. Intensity dependence of auditory evoked potentials in migraine: an indication of cortical potentiation and low serotonergic neurotransmission? Neurology 1996;46:1404-1409) were found abnormal in migraine between attacks, we have searched for intraindividual correlations between both tests in 59 migraine patients (22 with aura [MA], 37 without aura [MO]) and in 23 healthy volunteers (HV). METHODS: Amplitude change of the PR-VEP N1-P1 was measured between the 1st and 5th block of 50 sequential averagings during continuous stimulation at 3.1 Hz. IDAP was computed from N1-P2 amplitudes of 100 averagings during stimulations at 40, 50, 60 and 70 dB SL. Amplitude-stimulus intensity function (ASF) slopes and amplitude changes between 40 and 70 dB were calculated. MO and MA differed from HV in PR-VEP amplitude change (P=0.007) and IDAP slope (P = 0.0004). RESULTS: There was no significant correlation between VEP amplitude changes and IDAP slopes, nor between the latter two and attack frequency or disease duration. A negative correlation was found between the amplitude of the first block of averaged responses and potentiation of VEP in all subject groups (P = 0.03) as well as between the amplitude of the auditory evoked potential, at 40 dB, and the percentage of amplitude increase between 40 and 70 dB in MO (P = 0.004) and MA (P = 0.007). ASF slopes and 40 dB amplitudes were significantly correlated only in the MA group (P = 0.002). These results confirm the interictal deficit of habituation in cortical processing of repetitive visual and auditory information in migraine. Since there is no intraindividual correlation between the cortical responses to these sensory modalities they are complementary tools for the study of migraine and may help to identify subgroups of patients with distinct pathophysiological mechanisms. CONCLUSIONS: The strong negative correlation between the initial amplitude of evoked potentials and their amplitude increase during subsequent averaging confirms that the response potentiation in migraine is likely to be due to a reduced preactivation level of sensory cortices.

Adult↗
PubMed2000

Prophylactic treatment of migraine with beta-blockers and riboflavin: differential effects on the intensity dependence of auditory evoked cortical potentials.

OBJECTIVE: To investigate the influence of different pharmacological treatments on the intensity dependence of auditory evoked cortical potentials in migraineurs. BACKGROUND: Between attacks, patients with migraine show abnormalities in cortical information processing and decreased brain mitochondrial energy reserve. Both are most probably relevant for migraine pathogenesis, and they could be differentially modified by prophylactic drug therapy. Design.-The intensity dependence of the auditory evoked cortical potentials is, on average, increased in migraine. We have studied this intensity dependence in 26 patients before and after a 4-month period of prophylaxis with beta-blockers (n = 11, all migraine without aura; metoprolol or bisoprolol) or riboflavin (n = 15, migraine without aura: 13, migraine with aura: 2). Recordings were performed at least 3 days before or after an attack. RESULTS: After the treatment with beta-blockers, the intensity dependence of the auditory evoked cortical potentials was significantly decreased (before: 1.66+/-1.02 microV/10 dB; after: 0.79+/-1.06 microV/10 dB, P=.02). The decrease in intensity dependence was correlated significantly with clinical improvement (r = .69, P = .02). There was no change in intensity dependence after riboflavin treatment (before: 1.80+/-0.81 microV/10 dB; after: 1.56+/-0.83 microV/10 dB, P = .39), although the majority of patients showed improvement. CONCLUSIONS: These results confirm that beta-blockers and riboflavin act on two distinct pathophysiological mechanisms. Combining both treatments might enhance their efficacy without increasing central nervous system side effects.

Adrenergic beta-Antagonists↗
PubMed2000

Habituation of visual and intensity dependence of auditory evoked cortical potentials tends to normalize just before and during the migraine attack.

Between attacks, migraine with (MO) or without aura (MA) patients show deficient habituation of pattern-reversal visual evoked potentials (PR-VEP) and a strong intensity dependence of auditory evoked cortical potentials (IDAP). Clinical observations of migraine prodromes and previously published electrophysiological studies suggest that cortical information processing may vary in close temporal relationship to the attack. We studied PR-VEP and IDAP just before (11 MO pts), during (23 MO, 3 MA), 1 day following (27 MO, 1 MA) and 2 days following (14 MO) a migraine attack. The results were compared with a large group of MO patients recorded at a distance of at least 3 days from an attack (n = 66 for IDAP; n = 39 for VEP). Patients recorded the day before the attack had on average an habituation of -13.6+/-20.5% (mean +/- SD) between the 5th and 1st block of 100 averaged VEP responses and a flat (0.38+/-1.06 microV/10 dB) amplitude-stimulus intensity function (ASF) slope of the auditory evoked cortical potential. Both values were significantly different from those obtained in the attack interval (P=0.003; P=0.020). During the attack, VEP habituation was less pronounced (-0.17+/-26.2%) and ASF slopes remained flat (0.32+/-1.44 microV/10 dB; P=0.002 compared to interval). During the 2 days following the attack, VEP habituation was replaced by potentiation (+0.09+/-29.1% the 1st day; 19.5+/-45.7% the 2nd day) and ASF slopes increased markedly (0.87+/-1.39 and 1.14+/-1.12 microV/10 dB). The normalization of evoked cortical responses just before and during the attack, might reflect an increase in the cortical preactivation level due to enhanced activity in raphe-cortical serotonergic pathways.

Adult↗
PubMed2000

Effects of optokinetically induced rotatory self-motion on spatial perception and representation.

OBJECTIVE: Our aim was to investigate the influence of optokinetically induced rotatory self-motion sensation (circular vection [CV]) on asymmetries in real and representational space in normal subjects. BACKGROUND: Vestibular and optokinetic stimulation (particularly when accompanied by rightward CV) can reduce left-sided hemineglect in patients. METHOD: Twenty healthy right-handed men were administered a line bisection (LB) task and a stimulus-response compatibility task monitoring mental representation of space (the RULER task). The RULER task required speeded unimanual decisions ("smaller than 6?" vs. "larger than 6?") to foveally presented numbers between 1 and 11. Both tasks were performed in a baseline condition (no stimulation) and with full-field optokinetic stimulation to induce CV to either side. RESULTS: The bisection marks of both hands were shifted significantly to the left during leftward CV, introducing a pseudoneglect for the left and right hands. Rightward CV did not influence LB. In the RULER task, we found a stimulus-response compatibility, namely, faster right-hand responses to large numbers (i.e., 7-11) and faster left-hand responses to small numbers (i.e., 1-5). Although optokinetic stimulation did not significantly affect subjects' representation of space, the overall pattern of observed deviations was strikingly similar to that obtained in LB. CONCLUSIONS: Optokinetic stimulation affects healthy subjects' exploration and, to a lesser extent, their representation of space. In contrast to previous studies in neglect patients and healthy subjects, we found that leftward CV rather than rightward CV induced a leftward deviation of the subjective midpoint. This discrepancy is most likely a consequence of the exclusively peripheral visual field stimulation in our experiment. We suggest that the leftward deviation during rightward CV described in former studies may be due to the cuing effect of the leftward moving dots in the central visual field. In the absence of these central cues, the direction of CV seems to be the main determining factor for observed hemispatial effects.

Adult↗
PubMed2000

From neurophysiology to genetics: cortical information processing in migraine underlies familial influences--a novel approach.

Migraine patients show impaired cortical information processing between attacks with deficient habituation of pattern-reversal visual evoked potentials (VEP), and strong intensity dependence of auditory cortical evoked potentials (IDAP). This could be a genetic trait as certain genetic patterns are known for evoked potentials in healthy subjects. VEP-habituation and IDAP were studied in 40 migraine patients, i.e. pairs of 20 parents and their children. We developed a novel approach based on Monte Carlo statistics to selectively assess vertical familial influences. Both groups, parents and children, were characterized by abnormal VEP-habituation and IDAP. However, similarity between related pairs was far more pronounced than similarity between unrelated pairs. Assessed with a novel statistical approach, familial influences proved to be highly significant in determining cortical information processing in migraineurs, thus supporting the important role of genetic factors.

Adolescent↗