The Photoparoxysmal Response Reflects Abnormal Early Visuomotor Integration in the Human Motor Cortex.

BACKGROUND: Visual-paired associative stimulation (V-PAS) is a transcranial magnetic stimulation (TMS) technique able to investigate long-term potentiation (LTP) and depression (LTD)-like plasticity in the primary motor cortex (M1) arising through early visuomotor integration. OBJECTIVE/HYPOTHESIS: Abnormal early visuomotor integration might contribute to the pathophysiology of intermittent photic stimulation (IPS)-induced photoparoxysmal response (PPR). METHODS: We applied V-PAS in 25 healthy subjects (HS), 25 PPR-positive patients, with and without idiopathic generalized epilepsy (IGE), and 8 PPR-negative patients with IGE. V-PAS consisted of primary visual area activation achieved by visual evoked potentials coupled with TMS-induced M1 activation at 100 ms interstimulus interval (ISI) (V-PAS100). Before and after V-PAS, we measured changes in motor evoked potentials (MEPs). We compared MEPs after 1 Hz repetitive TMS (rTMS) and 0.25 Hz-V-PAS100. To examine possible V-PAS-induced after-effects at other ISIs, we delivered V-PAS at 40 (V-PAS40) and 140 ms ISIs (V-PAS140). To clarify whether V-PAS100 increases parieto-/premotor-to-M1 connectivity, before and after V-PAS100, we examined MEPs evoked by paired-pulse techniques. RESULTS: V-PAS100 increased MEPs more in PPR-positive patients than in HS. PPR-negative patients had normal response to V-PAS100. 1 Hz-rTMS, 0.25 Hz-V-PAS100 and V-PAS40 elicited similar responses in HS and PPR-positive patients, whereas V-PAS140 induced stronger after-effects in PPR-positive patients than HS. After V-PAS, MEPs elicited by facilitatory paired-pulse protocols decreased similarly in HS and PPR-positive patients. Conversely, MEPs elicited by inhibitory protocols decreased in HS, whereas in PPR-positive patients, they turned from inhibition to facilitation. CONCLUSION: We suggest that abnormal early visuomotor integration contributes to the pathophysiology of PPR.

Early visuomotor integration processes induce LTP/LTD-like plasticity in the human motor cortex.

To investigate whether visuomotor integration processes induce long-term potentiation (LTP) and depression (LTD)-like plasticity in the primary motor cortex (M1), we designed a new paired associative stimulation (PAS) protocol coupling left primary visual area (V1) activation achieved by hemifield visual evoked potentials (VEPs) and transcranial magnetic stimulation (TMS) over the left M1, at specific interstimulus intervals (ISIs), delivered at 1 Hz (V-PAS). Before and after V-PAS, we measured motor evoked potentials (MEPs). To clarify the mechanisms underlying V-PAS, we tested the effect of 1-Hz repetitive TMS (rTMS), 0.25-Hz V-PAS and rTMS, and a shorter 0.25-Hz V-PAS protocol. To examine V-PAS with contralateral V1 activation, we delivered V-PAS activating the right V1. To clarify whether V-PAS increases V1 activity or parieto- and premotor-to-M1 connectivity, before and after V-PAS, we examined VEPs and MEPs evoked by paired-pulse techniques. V-PAS increased, decreased, or left MEPs unchanged according to the ISI used. After 1-Hz rTMS MEPs decreased. Although 0.25-Hz rTMS elicited no aftereffect, 0.25-Hz V-PAS modulated MEPs according to the ISI used. The short 0.25-Hz V-PAS protocol left MEPs unchanged. Contralateral V-PAS inhibited MEPs. After V-PAS, VEPs remained unchanged and the premotor-to-M1 inhibitory connections decreased. V-PAS induces M1 LTP/LTD-like plasticity by activating premotor-to-motor connections.

Anterior cervical discectomy and fusion with "mini-invasive" harvesting of iliac crest graft versus polyetheretherketone (PEEK) cages: a retrospective outcome analysis.

BACKGROUND: Limited outcome data suggested a minimal evidence for better clinical and radiographic outcome of polyetheretherketone cages compared with bone grafts in the anterior cervical discectomy and fusion. We proposed a "mini-invasive" surgical technique for harvesting iliac crest grafts that provides bicortical autografts of sufficient size to be used in multilevel cervical procedures and is not associated with long-term significant donor site pain. METHODS: All patients undergoing discectomy and fusion during a three years period were consecutively extracted from computer database and retrospectively evaluated by means of telephonic interview, independently from surgical procedure (iliac crest autograph or prosthesis). Two procedure-blinded neurologists retrieved baseline clinical-demographic data and pre-surgical scores of routinely performed scales for pain and functional abilities. Afterwards, a third blinded neurologist performed clinical follow up by a semi-structured interview including Verbal Analog Scale for pain and Neck Disability Scale for discomfort. RESULTS: 80 patients out of 115 selected cases completed the follow up. 40 patients had been treated by mini-invasive bone graft harvesting and 40 with PEEK cages for cervical fusion. VAS for both neck and arm pain were significantly reduced within groups. Patients did not complaint any significant pain and/or paraesthesias at donor site from the first week after intervention. Neck Disability Scale was significantly lower at the end of follow up in both groups. CONCLUSIONS: "Miniinvasive" bicortical autografts is a less invasive, inexpensive technique to harvest iliac graft that may produce a reduced amount of general and local donor-site complications without outcome differences with prosthetic cages.

Somatosensory temporal discrimination threshold may help to differentiate patients with multiple system atrophy from patients with Parkinson's disease.

BACKGROUND AND PURPOSE: Somatosensory temporal discrimination threshold (STDT) is defined as the threshold at which two tactile stimuli applied to the skin are perceived as clearly distinct. The aim of the study was to investigate whether the extent of STDT alterations differs between patients with parkinsonian type multiple system atrophy (MSA-P) and patients with Parkinson's disease (PD). Possible differences between the two groups may help to differentiate MSA-P from PD. METHODS: STDT was investigated in 20 patients with MSA-P, 21 patients with PD and 18 age-matched healthy subjects. The clinical evaluation included the Mini-Mental State Examination, Hoehn and Yahr Scale, Frontal Assessment Battery, Unified Multiple System Atrophy Rating Scale for patients with MSA-P, and Unified Parkinson's Disease Rating Scale for patients with PD. STDT was investigated by delivering paired electrical stimuli starting with an inter-stimulus interval (ISI) of 0 ms (simultaneous pair), and progressively increasing the ISIs in 10-ms steps. RESULTS: Between-group anova showed that STDT statistically differed in MSA-P versus patients with PD and healthy subjects. Post hoc showed that STDT values in patients with MSA-P were significantly higher than those in patients with PD and healthy subjects. Receiver operating characteristic curve analysis showed that STDT testing yielded high diagnostic specificity and sensitivity. CONCLUSIONS: STDT is abnormal in patients with MSA-P and PD. The degree of STDT abnormalities is higher in patients with MSA-P than in patients with PD.

Correlation between cortical plasticity, motor learning and BDNF genotype in healthy subjects.

There is good evidence that synaptic plasticity in human motor cortex is involved in behavioural motor learning; in addition, it is now possible to probe mechanisms of synaptic plasticity using a variety of transcranial brain-stimulation protocols. Interactions between these protocols suggest that they both utilise common mechanisms. The aim of the present experiments was to test how well responsiveness to brain-stimulation protocols and behavioural motor learning correlate with each other in a sample of 21 healthy volunteers. We also examined whether any of these measures were influenced by the presence of a Val66Met polymorphism in the BDNF gene since this is another factor that has been suggested to be able to predict response to tests of synaptic plasticity. In 3 different experimental sessions, volunteers underwent 5-Hz rTMS, intermittent theta-burst stimulation (iTBS) and a motor learning task. Blood samples were collected from each subject for BDNF genotyping. As expected, both 5-Hz rTMS and iTBS significantly facilitated MEPs. Similarly, as expected, kinematic variables of finger movement significantly improved during the motor learning task. Although there was a significant correlation between the effect of iTBS and 5-Hz rTMS, there was no relationship in each subject between the amount of TMS-induced plasticity and the increase in kinematic variables during motor learning. Val66Val and Val66Met carriers did not differ in their response to any of the protocols. The present results emphasise that although some TMS measures of cortical plasticity may correlate with each other, they may not always relate directly to measures of behavioural learning. Similarly, presence of the Val66Met BDNF polymorphism also does not reliably predict responsiveness in small groups of individuals. Individual success in behavioural learning is unlikely to be closely related to any single measure of synaptic plasticity.

[Follow-up of thyroidectomized patients]. / Il follow-up del tiroidectomizzato.

The functional recovery of the patient after thyroid surgery is the primary objective but cannot always be achieved as a result of factors relating principally to the nature of the pathology treated and the extent of the thyroidectomy, though problems linked to possible damage to the recurrent nerves and altered calcium metabolism cannot be ignored. The data obtained from a large case series followed up for an appreciable time show that: Postoperative hypothyroidism is difficult to predict and very much depends on the evolution of the residual thyroid pathology. Subclinical and clinical thyroid insufficiency can be identified by correct assessment of TSH, the TRH test and the clinical picture. Substitution therapy presents no problems but should be personalized for each individual case. Injuries to the recurrent nerves constitute a major complication especially in subjects already afflicted by a monolateral lesion, a possibility that should always be investigated before surgery. The correct surgical technique will always expose and/or prepare the nerve along its entire length. Alterations to calcium metabolism are not always attributable to parathyroid lesions and are in fact almost always the expression of a complex acute deficiency picture that can be cured by correct medical treatment. PTH assays are particularly valuable for this purpose. All the above indicates the outstanding importance of follow-up of thyroidectomy patients who are otherwise destined for dysfunctions or pathologies that are not easy to cure.

Double-rosetting technique for the detection of Fc gamma receptor-positive T lymphocytes.

Lymphocyte populations that bear Fc receptors for immunoglobulin G (IgG) (Fc gamma R) seem to be important in a variety of human diseases and have been studied extensively with several techniques to assess their status in human pathologic conditions. The immunologic role of these cells is quite important as they appear to contain the majority of T lymphocytes with suppressor activity and thus may have important regulatory functions. The Fc gamma R+ T lymphocytes are altered in several immunologic diseases and in some neoplastic conditions. We have studied FcR+ lymphocytes by a new method employing E-rosetting techniques in conjunction with a rosetting technique with chicken erythrocytes sensitized with rabbit antichicken erythrocyte IgG. In this fashion we have been able to define T lymphocytes and identify Fc gamma R+ lymphocytes in one simple step. This technique has been compared to other well-accepted methodologies and has given identical results. We have applied this technique to the examination of a group of women with nonmetastasized mammary carcinoma at different stages during their disease as compared with a group of normal, age-matched subjects. Our results indicate that Fc gamma R+ T lymphocytes detected by our mixed-rosette technique are significantly reduced in mammary carcinoma patients.