A parafoveal retinal cones analysis using adaptive-optics retinal camera in patients with primary open angle glaucoma.

Objectives: To study the density, spacing, and regularity of retinal cone photoreceptors using an Adaptive Optics (AO) retinal camera (Rtx1, Imagine Eyes, Orsay, France) in patients with Primary Open Angle Glaucoma (POAG) and to compare the outcomes with those of healthy age-matched control subjects.

Methods: The study included 43 eyes with POAG and 31 eyes of normal subjects. POAG patients were divided into three groups according to the severity of the visual field defect.

Visually induced analgesia during face or limb stimulation in healthy and migraine subjects.

Background: Visually induced analgesia (VIA) defines a phenomenon in which viewing one's own body part during its painful stimulation decreases the perception of pain. VIA occurs during direct vision of the stimulated body part and also when seeing it reflected in a mirror. To the best of our knowledge, VIA has not been studied in the trigeminal area, where it could be relevant for the control of headache.

Correlation between deep brain stimulation effects on freezing of gait and audio-spinal reflex.

Objective: A network of cortical, subcortical and brainstem structures might be involved in freezing of gait (FOG). Subthalamic nucleus (STN) deep brain stimulation (DBS) could modulate this network. The audio-spinal reflex (ASR), reduced in PD, but increased by treatment, can be used to further investigate that locomotor network.

Cerebral metabolism before and after external trigeminal nerve stimulation in episodic migraine.

Background and aim A recent sham-controlled trial showed that external trigeminal nerve stimulation (eTNS) is effective in episodic migraine (MO) prevention. However, its mechanism of action remains unknown. We performed 18-fluorodeoxyglucose positron emission tomography (FDG-PET) to evaluate brain metabolic changes before and after eTNS in episodic migraineurs.

Effects of visual cortex activation on the nociceptive blink reflex in healthy subjects.

Bright light can cause excessive visual discomfort, referred to as photophobia. The precise mechanisms linking luminance to the trigeminal nociceptive system supposed to mediate this discomfort are not known. To address this issue in healthy human subjects we modulated differentially visual cortex activity by repetitive transcranial magnetic stimulation (rTMS) or flash light stimulation, and studied the effect on supraorbital pain thresholds and the nociceptive-specific blink reflex (nBR).

Analysis and clinical correlates of 20 Hz photic driving on routine EEG in migraine.

Enhanced photic driving (PD) during high-frequency flicker stimulation, the so-called H response, is a classical feature of migraine patients between attacks, but is thought to be of poor clinical utility. Visual inspection of the EEG for its detection may not be reliable, however, data on its possible correlations with clinical features and migraine pathophysiology are scarce. We have compared visual inspection and EEG spectral analysis to detect abnormal PD in 280 consecutive migraine patients of our headache clinic (episodic migraine without aura, n = 171; chronic migraine, n = 48; migraine with aura, n = 61) and in a group of 24 non-migrainous neurological controls.

Transcranial Direct Current Stimulation (tDCS) of the visual cortex: a proof-of-concept study based on interictal electrophysiological abnormalities in migraine.

Background: Preventive pharmacotherapy for migraine is not satisfactory because of the low efficacy/tolerability ratio of many available drugs. Novel and more efficient preventive strategies are therefore warranted. Abnormal excitability of cortical areas appears to play a pivotal role in migraine pathophysiology.

Abnormal corticospinal excitability in patients with disorders of consciousness.

Background: Transcranial magnetic stimulation (TMS) has been frequently used to explore changes in the human motor cortex in different conditions, while the extent of motor cortex reorganization in patients in vegetative state (VS) (now known as unresponsive wakefulness syndrome, UWS) and minimally conscious (MCS) states due to severe brain damage remains largely unknown.

Objective/hypothesis: It was hypothesized that cortical motor excitability would be decreased and would correlate to the level of consciousness in patients with disorders of consciousness.

Methods: Corticospinal excitability was assessed in 47 patients (24 VS/UWS and 23 MCS) and 14 healthy controls.

Effects of repetitive transcranial magnetic stimulation on somatosensory evoked potentials and high frequency oscillations in migraine.

Background: In previous studies we found that high-frequency somatosensory oscillations (HFOs) reflecting thalamo-cortical activation were decreased in migraineurs between attacks and that high-frequency repetitive transcranial magnetic stimulation (rTMS) was able to normalize the habituation deficit of visual evoked potentials (VEPs). Here we study the effects of activating (10 Hz) or inhibiting (1 Hz) rTMS on conventional low-frequency (LF) and high-frequency somatosensory evoked potentials (SSEPs).

Subjects And Methods: rTMS was applied on the motor cortex of 13 healthy volunteers (HVs) and 13 migraine without aura (MO) patients.

Habituation of evoked responses is greater in patients with familial hemiplegic migraine than in controls: a contrast with the common forms of migraine.

Background: Familial hemiplegic migraine (FHM) is a rare, dominantly inherited subtype of migraine with transient hemiplegia during the aura phase. Mutations in at least three different genes can produce the FHM phenotype. The mutated FHM genes code for ion transport proteins that animal and cellular studies have associated with disturbed ion homeostasis, altered cellular excitability, neurotransmitter release, and decreased threshold for cortical spreading depression.

Nitroglycerin sensitises in healthy subjects CNS structures involved in migraine pathophysiology: evidence from a study of nociceptive blink reflexes and visual evoked potentials.

Nitroglycerin (NTG), a NO donor, induces an attack in migraine patients approximately 4-6 h after administration. The causative mechanisms are not known, but the long delay leaves room for a central effect, such as a change in neuronal excitability and synaptic transmission of various CNS areas involved in pain and behaviour including trigeminal nucleus caudalis and monoaminergic brain stem nuclei. To explore the central action of NTG, we have studied its effects on amplitude and habituation of the nociceptive blink reflex (nBR) and the visual evoked potential (VEP) before, 1 h and 4 h after administration of NTG (1.

Abnormalities of the vestibulo-collic reflex are similar in migraineurs with and without vertigo.

The amplitude and habituation of the click-evoked vestibulo-collic reflex (VCR) was found reduced between attacks in migraineurs without complaints of ictal or interictal vertigo or dizziness, compared with healthy subjects. As a next step we recorded VCR in 17 migraine patients (eight with migraine without aura and nine with migraine with aura) who presented ictal migrainous vertigo according to the criteria defined by Neuhauser et al., using a method described previously.

Performances in cerebellar and neuromuscular transmission tests are correlated in migraine with aura.

In previous studies, we described subclinical abnormalities of neuromuscular transmission and cerebellar functions in migraineurs. The aim of this study was to search if these two functions are correlated in the same patient. Thirteen migraineurs [five without aura (MO) and eight with aura (MA)] underwent both stimulation-SFEMG and 3D-movement analysis.

The vestibulo-collic reflex is abnormal in migraine.

Interictal evoked central nervous system responses are characterized in migraineurs by a deficit of habituation, at both cortical and subcortical levels. The click-evoked vestibulo-collic reflex (VCR) allows the assessment of otolith function and an oligosynaptic pathway linking receptors in the saccular macula to motoneurons of neck muscles. Three blocks of 75 averaged responses to monaural 95-dB normal hearing level 3-Hz clicks were recorded over the contracted ipsilateral sternocleidomastoid muscle in 25 migraineurs between attacks and 20 healthy subjects, without vestibular symptoms.

Inhibition of the nociceptive R2 blink reflex after supraorbital or index finger stimulation is normal in migraine without aura between attacks.

In order to explore possible interictal brainstem dysfunctions in migraine, we have studied the R2 component of the nociceptive specific blink reflex (nBR) after conditioning by supraorbital or index finger stimuli in 14 untreated migraine without aura patients (MO) between attacks and in 15 healthy volunteers. We determined the R2 recovery curve at increasing inter-stimulus intervals between 50 and 600 ms. The nBR was conditioned by a paired supraorbital stimulus and, in another session, by an ipsilateral electrical shock delivered to the index finger.

Occipital nerve stimulation for drug-resistant chronic cluster headache: a prospective pilot study.

Background: Drug-resistant chronic cluster headache (drCCH) is a devastating disorder for which various destructive procedures have been tried unsuccessfully. Occipital nerve stimulation (ONS) is a new, safe strategy for intractable headaches. We undertook a prospective pilot trial of ONS in drCCH to assess clinical efficacy and pain perception.

Interictal habituation deficit of the nociceptive blink reflex: an endophenotypic marker for presymptomatic migraine?

Habituation of the nociception-specific blink reflex (nBR) is reduced interictally in migraine patients. This could be related to the habituation deficit of evoked cortical responses, a reproducible abnormality in migraine which has a familial character, or to central trigeminal sensitization due to repeated attacks. We compared nBR habituation in healthy volunteers devoid of personal or family history of migraine (HV), in migraine without aura patients (MO) and in healthy volunteers with a family history of migraine in first degree relatives (HV-F).

Nociceptive blink reflex and visual evoked potential habituations are correlated in migraine.

Background: Lack of habituation, as reported in migraine patients between attacks for evoked cortical responses, was also recently found for the nociceptive blink reflex (nBR) mediated by brainstem neurons. It is not known if both brain stem and cortical habituation deficits are correlated in the same patient, which would favor a common underlying mechanism.

Objective: To search for intraindividual correlations between habituation of pattern reversal-visual evoked potentials and that of the nociception-specific blink reflex in migraineurs and in healthy volunteers (HV).

Hypothalamic stimulation in chronic cluster headache: a pilot study of efficacy and mode of action.

We enrolled six patients suffering from refractory chronic cluster headache in a pilot trial of neurostimulation of the ipsilateral ventroposterior hypothalamus using the stereotactic coordinates published previously. After the varying durations needed to determine optimal stimulation parameters and a mean follow-up of 14.5 months, the clinical outcome is excellent in three patients (two are pain-free; one has fewer than three attacks per month), but unsatisfactory in one patient, who only has had transient remissions.

Somatosensory evoked high-frequency oscillations reflecting thalamo-cortical activity are decreased in migraine patients between attacks.

A deficit of habituation in cortical information processing, including somatosensory evoked potentials (SSEPs), is the most consistent neurophysiological abnormality in migraine patients between attacks. To explore further the mechanisms underlying this interictal neural dysfunction, we have studied the high-frequency oscillations (HFOs) embedded in SSEPs because they are thought to reflect spike activity in thalamo-cortical cholinergic fibres (early HFOs) and in cortical inhibitory GABAergic interneurons (late HFOs). Untreated migraine patients with (MA) and without (MO) aura were recorded during (n = 13: nine MO, four MA) and between attacks (n = 29: 14 MO, 15 MA) and compared with healthy volunteers.

Post-stroke reorganization of hand motor area: a 1-year prospective follow-up with focal transcranial magnetic stimulation.

Objective: Focal transcranial magnetic stimulation was used to test prospectively corticospinal excitability changes and reorganization of first dorsal interosseous (FDI) motor cortical representation in 31 patients who experienced a first ischemic stroke in the middle cerebral artery territory. All had severe hand palsy at onset.

Methods: Patients were assessed clinically with the Medical Research Council, Rankin, the National Institutes of Health stroke scales and Barthel Index at days 1, 8, 30, 90, 180 and 360 after stroke.

Lack of habituation causes high intensity dependence of auditory evoked cortical potentials in migraine.

Migraineurs are characterized interictally by lack of habituation, or even potentiation, of cortical evoked potentials during repetitive stimulation and by a strong intensity dependence of auditory evoked potentials (IDAP). To determine whether these two features of sensory processing are interrelated, we have studied them simultaneously on the same recordings of auditory evoked potentials (AEPs). AEPs were obtained at four different stimulation intensities in 14 patients suffering from migraine without aura (MO) and 14 healthy volunteers (HV).

Effects of repetitive transcranial magnetic stimulation on visual evoked potentials: new insights in healthy subjects.

In a previous comparative study with migraineurs, we found in 24 normal subjects that the amplitude of the pattern-reversal visual evoked potential (PR-VEP) in the first block of 100 responses and its habituation over 6 sequential blocks were significantly decreased after 1 Hz repetitive transcranial magnetic stimulation (rTMS), while 10 Hz rTMS had no significant effect. We report here our results on the reproducibility of the rTMS effect studied in ten of these subjects by repeating the recordings for each frequency three times on different days. We have also reanalysed the data obtained in 24 normal subjects, looking separately at the results in those stimulated at an intensity equal to phosphene threshold (group 1; n=14) and those stimulated at 110% of motor threshold because of unelicitable phosphenes (group 2; n=10).

Changes in motor unit numbers in patients with ALS: a longitudinal study using the adapted multiple point stimulation method.

Method: The adapted multiple point stimulation (AMPS) method for calculating motor unit numbers (MUNE) was applied in 12 patients with amyotrophic lateral sclerosis (ALS) before riluzole therapy (T(0)) and again after 4, 8 and 12 months of treatment.

Results: Paired Student's t-test indicated a significant decrease of thenar MUNE and compound muscle action potential (CMAP) size at each 4-monthly interval, while average surface motor unit potential (SMUP) size did not change significantly over time. The rate of motor unit (MU) loss at month 4 was more than 20% in six patients (group 1) and less than 20% in six other patients (group 2).

Single motor axon conduction velocities of human upper and lower limb motor units. A study with transcranial electrical stimulation.

Objectives: To calculate conduction velocities (CV) of single motor axons innervating hand, forearm and leg muscles, weak anodal electrical transcranial stimuli were used and single motor unit potentials were recorded in 17 normal subjects.

Methods: The central motor conduction time and neuromuscular transmission delay were subtracted from the latency of unit response to cortical stimulation and single motor axon CV were calculated.

Results: In extensor indicis proprius (EIP) units, CV ranged from 30.