Occurrence and characterization of Pain in immune-mediated neuropathies: a multicentre prospective study

BACKGROUND

pain is a common symptom of peripheral neuropathies that may severely affect patients' Quality of Life. Pain questionnaires, based on verbal descriptors, are a useful way to investigate it.

METHODS

we performed a multicentre study through validated measures to characterize pain in a sample of consecutive patients affected by immune-mediated neuropathies.

RESULTS

ninety-three patients were enrolled in 16 Italian centres. Based on the numeric rating scale, almost half of the patients complained of moderate pain and one-third of the patients severe pain. Overall, up to 50% of our patients with immune-mediated neuropathies complained of neuropathic pain. The most common neuropathic symptoms were paraesthesia/dysesthesia and superficial spontaneous pain. Surprisingly, also patients with neuropathies commonly thought to be painless (such as multifocal motor neuropathy) reported discomfort and painful symptoms.

CONCLUSIONS

pain questionnaires should be considered in the clinical evaluation of immune-mediated neuropathies, also when evaluating therapy efficacy, because they may provide clinicians with useful information on painful symptoms and patients' quality of life.

Seipin S90L mutation in an Italian family with CMT2/dHMN and pyramidal signs

Heterozygous mutations in the Berardinelli-Seip congenital lipodystrophy (BSCL2) gene have been associated with different clinical phenotypes including Silver syndrome/spastic paraplegia 17, distal hereditary motor neuropathy type V, and Charcot-Marie-Tooth disease type 2 (CMT2) with predominant hand involvement. We studied an Italian family with a CMT2 phenotype with pyramidal signs that had subclinical sensory involvement on sural nerve biopsy. Direct sequencing analysis of the BSCL2 gene in the three affected siblings revealed an S90L mutation. This report confirms the variability of clinical phenotypes associated with a BSCL2 Ser90Leu mutation and describes the first Italian family with this mutation.

Correlations between peripheral blood mononuclear cell production of BDNF, TNF-alpha, IL-6, IL-10 and cognitive performances in multiple sclerosis patients

The aim of this study was to investigate the role of Brain Derived Neurotrophic Factor (BDNF) and inflammatory factors in the development of cognitive dysfunctions in Multiple Sclerosis (MS). We correlated peripheral blood mononuclear cell (PBMC) production of BDNF, Tumor Necrosis Factor-alpha (TNF-alpha), Interleukin (IL)-6 and IL-10 with performances on specific neuropsychological tasks in a selected series of MS patients. We studied a sample of 30 patients with relapsing-remitting (RR)MS, segregated by gender and matched for age, education, disease duration, type of immunomodulating therapy, degree of disability and overall cognitive status. We found that low BDNF levels were correlated with increased time of execution on a divided attention and visual scanning task whereas high levels of IL-6 were correlated with low Mini Mental State Examination scores. We did not observe any significant correlations between IL-10, TNF-alpha levels and cognitive performances in our patients. In conclusion our study shows a correlation between low BDNF and high IL-6 production by PBMCs and poorer performances in cognitive tasks in RRMS patients suggesting a possible role of these factors in cognitive impairment in MS.

T-bet and pSTAT-1 expression in PBMC from coeliac disease patients: new markers of disease activity

Coeliac disease (CD) is considered a T cell-mediated autoimmune disease, and up-regulation of T-bet and phosphorylated signal transducers and activators of transcription (pSTAT)1, key transcription factors for the development of T helper type 1 (Th1) cells, has been described in the mucosa of patients with untreated CD. Using transcription factor analysis, we investigated whether T-bet and pSTAT1 expressions are up-regulated in the peripheral blood of CD patients and correlate with disease activity. Using flow cytometry, we analysed T-bet, pSTAT1 and pSTAT3 expression in CD4(+), CD8(+) T cells, CD19(+) B cells and monocytes from peripheral blood of 15 untreated and 15 treated CD patients and 30 controls, and longitudinally in five coeliac patients before and after dietary treatment. We evaluated using enzyme-linked immunosorbent assay (ELISA), interferon (FN)-gamma, interleukin (IL)-17 and IL-10 production by peripheral blood mononuclear cell (PBMC) cultures. T-bet expression in CD4(+), CD8(+) T cells, CD19(+) B cells and monocytes and IFN-gamma production by PBMC was higher in untreated than in treated CD patients and controls. pSTAT1 expression was higher in CD4(+)T cells, B cells and monocytes from untreated than from treated CD patients and controls. pSTAT3 was increased only in monocytes from untreated patients compared with CD-treated patients and controls. The data obtained from the longitudinal evaluation of transcription factors confirmed these results. Flow cytometric analysis of pSTAT1 and T-bet protein expression in peripheral blood mononuclear cells could be useful and sensible markers in the follow-up of CD patients to evaluate disease activity and response to dietary treatment.

Stroke in critically ill patients

Advances in critical care medicine have led to improved survival rates among patients admitted to the Intensive Care unit (ICU), but complications experienced during admittance in an ICU may influence long-term outcome and the neurocognitive state of these patients. Coagulation disorders, glucose intolerance, diabetes, pro-inflammatory state and underlying severe pathologies are common risk factors for stroke development in ICU patients. Stroke may result in very serious consequences like motor function impairment, neglect and aphasia, but in some cases, stroke may not result in any clinical sign in acute phase. Recently, more attention has been given to this condition called ''silent stroke.'' ''Silent stroke'' could be the foundation of the development of neurocognitive impairment and vascular dementia. In ICU survivors, approximately 1/3 of patients or more will develop chronic neurocognitive impairment. With the advent of sensitive techniques for brain imaging, silent brain lesions, including brain infarct and white matter changes, have been frequently recognized. Until now, epidemiological studies in this field evaluating incidence and consequences of stroke in ICU setting are lacking, and prospective studies are required to evaluate the impact of this condition on the quality of life, neurocognitive outcome and mortality of ICU patients. We believe that when stroke occurs in critically ill patients, more attention is typically given to the underlying pathologies than stroke, and this may influence the long-term outcome. Guidelines for the early management of stroke, commonly used in Stroke Units, should be followed, even in critically ill patients in an ICU setting.

Reduced cerebral cortex inhibition in dystonia: direct evidence in humans

OBJECTIVE

A loss of inhibition in central motor circuits resulting in abnormal motor control is the hypothesised cause of dystonia. So far, changes in inhibitory function of cerebral cortex in dystonia, have been revealed only indirectly by recording muscle responses evoked by transcranial magnetic stimulation (TMS) of the brain. The aim of present study was to evaluate more directly cerebral cortex changes in dystonia. We had the almost unique opportunity to record directly motor cortex output after brain stimulation, in a dystonic patient who had epidural electrodes implanted in the upper cervical cord.

METHODS

We evaluated descending activity evoked by single and paired pulse TMS together with the inhibitory effects produced by afferent stimuli on TMS evoked activity, and compared the results with those obtained in thirteen subjects with no central nervous system abnormality who also had cervical spinal electrodes.

RESULTS

The intrinsic inhibitory activity produced by paired TMS of the motor cortex, and the inhibitory effects produced by afferent inputs, were suppressed in the patient with dystonia.

CONCLUSIONS

These findings provide a direct evidence of the abnormality in motor cortex inhibitory systems in dystonia.

SIGNIFICANCE

The abnormality in cortical inhibitory system might have a role in the pathophysiology of dystonia.

Does exposure to extremely low frequency magnetic fields produce functional changes in human brain?

Behavioral and neurophysiological changes have been reported after exposure to extremely low frequency magnetic fields (ELF-MF) both in animals and in humans. The physiological bases of these effects are still poorly understood. In vitro studies analyzed the effect of ELF-MF applied in pulsed mode (PEMFs) on neuronal cultures showing an increase in excitatory neurotransmission. Using transcranial brain stimulation, we studied noninvasively the effect of PEMFs on several measures of cortical excitability in 22 healthy volunteers, in 14 of the subjects we also evaluated the effects of sham field exposure. After 45 min of PEMF exposure, intracortical facilitation produced by paired pulse brain stimulation was significantly enhanced with an increase of about 20%, while other parameters of cortical excitability remained unchanged. Sham field exposure produced no effects. The increase in paired-pulse facilitation, a physiological parameter related to cortical glutamatergic activity, suggests that PEMFs exposure may produce an enhancement in cortical excitatory neurotransmission. This study suggests that PEMFs may produce functional changes in human brain.

T-bet, pSTAT1 and pSTAT3 expression in peripheral blood mononuclear cells during pregnancy correlates with post-partum activation of multiple sclerosis

In pregnant women affected by multiple sclerosis (MS) we observed increased percentages of CD4(+)CD25(+)Foxp3(+) T regulatory cells at the 1st and the 2nd trimester of gestation that was associated with a decreased T-bet expression in CD4(+) T cells. In women showing clinical relapse and/or new lesions at MRI after delivery we found, a higher expression of T-bet, pSTAT1 and pSTAT3 in CD4(+), CD8(+) T cells and CD14(+) cells, associated with an increase of IFNgamma and IL17 production by PBMC at the 3rd trimester of gestation and after delivery. Our data suggest that the expansion of circulating CD4(+)CD25(+)Foxp3(+) regulatory T cells and the lower expression of T-bet in CD4(+) T cells may account for the decreased MS activity during pregnancy. The expression of T-bet, pSTAT1 and pSTAT3 in peripheral blood CD4(+) and CD8(+) T cells and monocytes could be useful to identify MS patients who will develop a relapse after delivery.

Movement disorders in multiple sclerosis: causal or coincidental association?

Despite the relatively frequent involvement of the basal ganglia and subthalamic nucleus by multiple sclerosis (MS) plaques, movement disorders (MD), other than tremor secondary to cerebellar or brainstem lesions, are uncommon clinical manifestations of MS. MD were present in 12 of 733 patients with MS (1.6%): three patients had parkinsonism, two blepharospasm, five hemifacial spasm, one hemidystonia, and one tourettism. MD in patients with MS are often secondary to demyelinating disease. Also in cases without response to steroid treatment and demyelinating lesions in critical regions, it is not possible to exclude that MD and MS are causally related.

ANCA-related vasculitic neuropathy mimicking motor neuron disease

Several conditions have been reported to mimic motor neuron disease (MND) and misdiagnosis remains a common clinical problem. Peripheral neuropathy is a classic feature of many vasculitic syndromes and in some patients it may be the only manifestation of vasculitis. We report a case of ANCA-related vasculitic neuropathy where the clinical presentation was suggestive of MND. A 42-year-old woman was admitted to our centre to confirm a diagnosis of MND made elsewhere. Clinical examination revealed postural tremor at the right hand, mild tongue atrophy with diffuse fasciculations and brisk tendon reflexes without other muscular weakness or atrophies. Electromyography demonstrated denervation in tongue and in the first dorsal interosseous of right hand ; motor evoked potentials disclosed normal central motor conduction time. Laboratory studies revealed only a mild increase of p-ANCA. A muscle biopsy showed a small inflammatory infiltrate around a vessel. The patient started high dosage of oral steroids. After one year of follow-up the patient suspended oral steroids, postural tremor of the right hand disappeared and tongue fasciculations were reduced. Vasculitis may mimic a MND, particularly in the absence of sensory involvement. Caution should be exercised in the clinical diagnosis of MND. Muscle biopsy is indicated in patient with atypical MND especially in those with an exclusive involvement of lower motor neuron.

Low-frequency repetitive transcranial magnetic stimulation suppresses specific excitatory circuits in the human motor cortex

Previous studies have shown that low-frequency repetitive transcranial magnetic stimulation (rTMS) suppresses motor-evoked potentials (MEPs) evoked by single pulse TMS. The aim of the present paper was to investigate the central nervous system level at which rTMS produces a suppression of MEP amplitude. We recorded corticospinal volleys evoked by single pulse TMS of the motor cortex before and after 1 Hz rTMS in five conscious subjects who had an electrode implanted in the cervical epidural space for the control of pain. One of the patients had Parkinson's disease and was studied on medication. Repetitive TMS significantly suppressed the amplitude of later I-waves, and reduced the amplitude of concomitantly recorded MEPs. The earliest I-wave was not significantly modified by rTMS. The present results show that 1 Hz rTMS may decrease the amplitude of later descending waves, consistent with a cortical origin of the effect of 1 Hz rTMS on MEPs.

The physiological basis of the effects of intermittent theta burst stimulation of the human motor cortex

Theta burst stimulation (TBS) is a form of repetitive transcranial magnetic stimulation (TMS). When applied to motor cortex it leads to after-effects on corticospinal and corticocortical excitability that may reflect LTP/LTD-like synaptic effects. An inhibitory form of TBS (continuous, cTBS) suppresses MEPs, and spinal epidural recordings show this is due to suppression of the I1 volley evoked by TMS. Here we investigate whether the excitatory form of TBS (intermittent, iTBS) affects the same I-wave circuitry. We recorded corticospinal volleys evoked by single pulse TMS of the motor cortex before and after iTBS in three conscious patients who had an electrode implanted in the cervical epidural space for the control of pain. As in healthy subjects, iTBS increased MEPs, and this was accompanied by a significant increase in the amplitude of later I-waves, but not the I1 wave. In two of the patients we tested the excitability of the contralateral cortex and found a significant suppression of the late I-waves. The extent of the changes varied between the three patients, as did their age. To investigate whether age might be a significant contributor to the variability we examined the effect of iTBS on MEPs in 18 healthy subjects. iTBS facilitated MEPs evoked by TMS of the conditioned hemisphere and suppressed MEPs evoked by stimulation of the contralateral hemisphere. There was a slight but non-significant decline in MEP facilitation with age, suggesting that interindividual variability was more important than age in explaining our data. In a subgroup of 10 subjects we found that iTBS had no effect on the duration of the ipsilateral silent period suggesting that the reduction in contralateral MEPs was not due to an increase in ongoing transcallosal inhibition. In conclusion, iTBS affects the excitability of excitatory synaptic inputs to pyramidal tract neurones that are recruited by a TMS pulse, both in the stimulated hemisphere and in the contralateral hemisphere. However the circuits affected differ from those influenced by the inhibitory, cTBS, protocol. The implication is that cTBS and iTBS may have different therapeutic targets.

Segregating two inhibitory circuits in human motor cortex at the level of GABAA receptor subtypes: a TMS study

OBJECTIVE

To investigate if different interneuronal circuits in human motor cortex mediate inhibition through different subtypes of the gamma-aminobutyric acid A receptor (GABAAR).

METHODS

Two distinct forms of motor cortical inhibition were measured in 10 healthy subjects by established transcranial magnetic stimulation (TMS) protocols: short interval intracortical inhibition (SICI) and short latency afferent inhibition (SAI). Their modification by a single oral dose of three different positive GABAAR modulators (20 mg of diazepam, 2.5 mg of lorazepam and 10 mg of zolpidem) with different affinity profiles at the various alpha-subunit bearing subtypes of the GABAAR (diazepam: non-selective, lorazepam: unknown, zolpidem: 10-fold higher affinity to alpha1- than alpha2- or alpha3-subunit bearing GABAARs, no affinity to alpha5-subunits) was tested in a randomized crossover design. In addition, the sedative drug effects were recorded by a visual analogue scale.

RESULTS

Diazepam and lorazepam increased SICI, whereas zolpidem did not change SICI. In contrast, diazepam had no effect on SAI, whereas lorazepam and zolpidem decreased SAI. The sedative effects were not different between drugs.

CONCLUSIONS

The dissociating patterns of drug modification of SICI versus SAI strongly suggest that different GABAAR subtypes are involved in SICI and SAI.

SIGNIFICANCE

We provide evidence, for the first time, for a dissociation of effects of diazepam and zolpidem on SAI and confirm the previously reported differential effect of zolpidem and of diazepam and lorazepam on SICI. The differential effects of the three benzodiazepines on SAI and SICI suggest that neuronal circuits in human motor cortex that mediate inhibition through different GABAAR subtypes can be segregated by TMS.

Misdiagnosis of lumbar-sacral radiculopathy: usefulness of combination of EMG and ultrasound

In the presence of sensitive symptoms along the lumbar-sacral dermatomeric region, it is easy to suspect a lumbar-sacral radiculopathy, it being a very common disease. Clinical evaluation, neurophysiology and magnetic resonance imaging are common tools in diagnosing lumbosacral radiculopathy. Nevertheless, sometimes tumour may mimic radiculopathy. With the improvement of ultrasound, most peripheral nerves may be virtually identified. We describe two patients where tumour of sural nerve and tibial nerve mimicked S1 radiculopathy. We diagnosed the tumours only through a comprehensive nerve assessment combining clinical evaluation, US and neurophysiology. The association of neurophysiological and imaging US assessments, possibly in the same session, may avoid misdiagnosis.

SK3 polyglutamine tract polymorphism and acute oxaliplatin neurotoxicity: A translational study

21076

Background: Acute neurotoxicity of l-oxaliplatin (l-OHP), characterized by cold-induced paresthesias, muscle cramps and tightness, seems electrophysiologically related to an abnormal nerve hyperexcitability (NHE) resembling neuromyotonia, an autoimmune disease caused by autoantibodies directed against voltage-gated potassium channels (VGKC). This l-OHP-related channelopathy seems to be reversible, but there is no agreement about the channel involved, most investigators favouring voltage-gated sodium channels. SK3 VGKC are mainly located in the peripheral nervous system and are characterized by an highly polymorphic CAG motif. We hypothesized that SK3 potassium channel dysfunction might be responsible for nerve hyperexcitability in patients treated with l-OHP. Methods: Pts eligible for an l-OHP-containing regimen were enrolled. Detailed neurological examination, nerve conduction studies (NCS) and needle electromyography (EMG) were performed before and after l-OHP administration. Furthermore, a venous blood sample was obtained from each pt in order to perform genetic analysis. Genomic DNA was extracted from pts’ leukocytes and PCR-mediated amplification of the second polyglutamine CAG tract of SK3 gene was carried out; PCR products were analyzed on polyacrylamide gel stained with Ethidium Bromide. Results: We evaluated 20 pts (14M, 6F); mean age was 59 yrs. According to neurophysiologic data it was possible to divide pts into 3 groups: G0 (no symptoms or signs of NHE), 7 pts; G1 (cold induced paresthesias-mild NHE), 8 pts; G2 (muscle cramps-severe NHE), 5 pts. Genetic analysis showed different alleles ranging from 125 to 225 bp. In particular, 75% of pts carrying a 175 bp allele experienced severe acute toxicicy (G2 group), and 15% mild toxicity (G1 group). The 175 bp allele was found only in 1/7 G0 pts (15%); in these pts the alleles distribution was diffusely scattered. Conclusions: Acute and reversible NHE observed in some pts treated with l-OHP might be produced either by an increased sodium conductance or by a decreased activity of VGKC. The high percentage of the 175 bp allele, that we found in the G2 group, induces us to think that the polymorphism at CAG locus of SK3 may be responsible for l-OHP toxicity. Sequence analysis of PCR gene products is ongoing.

No significant financial relationships to disclose.

BDNF plasma levels in acute stroke

The transport of brain derived neurotrophic factor (BDNF) across the blood-brain barrier (BBB) is negligible in normal conditions. However, BDNF might pass through the BBB when BBB is disrupted by a pathological condition such as stroke. This migration of BDNF through the BBB might be important during post-ischemic phase since BDNF can exert a protective action in the site of lesion. This study aimed to investigate plasma levels of BDNF in the acute phase of stroke in humans. Serial venous blood samples were taken in ten patients with acute stroke at the admission to the Stroke Unit and on the following 4 days. In the same samples we also evaluated the plasma levels of S100beta protein, a marker of BBB disruption. There was no significant change in BDNF plasma levels in our patients, even in the presence of a pronounced BBB dysfunction, as demonstrated by a significant increase of S100beta protein concentrations at days 2 and 3 after stroke. Our data, though indirectly, suggest that there is no significant increase in endogenous extracellular BDNF after a stroke in humans.

Direct demonstration of the effects of repetitive paired-pulse transcranial magnetic stimulation at I-wave periodicity

OBJECTIVE

To investigate the central nervous system level at which paired-pulse repetitive transcranial magnetic stimulation at I-wave periodicity (iTMS) produces a facilitation of motor evoked potential (MEP) amplitude.

METHODS

In one conscious patient who had an electrode implanted in the cervical epidural space for the control of pain, we recorded corticospinal volleys evoked before, during and after iTMS of the motor cortex. Moreover, we compared MEPs to TMS and cervico-medullary junction stimulation before and after iTMS in a separate group of five healthy subjects.

RESULTS

In the patient with the epidural electrode, during iTMS there was progressive increase of MEP amplitude, and by the end of the intervention period MEP increased by more than 300%. The pronounced increase in MEP amplitude was paralleled by a slight increase in the amplitude of epidural volleys. An increased MEP amplitude (more than 200%) was still evident 3 min after the end of iTMS. In the five healthy subjects, iTMS produced a facilitation of MEPs evoked by transcranial magnetic stimulation but had no effect on CMEPs evoked by cervico-medullary junction stimulation.

CONCLUSIONS

The results indicate that iTMS leads to an increase in corticomotor excitability at a supraspinal level, and that this may include circuits in addition to those involved in I-wave generation.

SIGNIFICANCE

iTMS increases cortical excitability more widely than the I-wave networks that it targets.

Functional involvement of cerebral cortex in adult sleepwalking

The pathophysiology of adult sleepwalking is still poorly understood. However, it is widely accepted that sleepwalking is a disorder of arousal. Arousal circuits widely project to the cortex, including motor cortex. We hypothesized that functional abnormality of these circuits could lead to changes in cortical excitability in sleepwalkers, even during wakefulness. We used transcranial magnetic stimulation (TMS) to examine the excitability of the human motor cortex during wakefulness in a group of adult sleepwalkers. When compared with the healthy control group, short interval intracortical inhibition (SICI), cortical silent period (CSP) duration, and short latency afferent inhibition (SAI) were reduced in adult sleepwalkers during wakefulness. Mean CSP duration was shorter in patients than in controls (80.9 +/- 41 ms vs. 139.4 +/- 37 ms; p = 0.0040). Mean SICI was significantly reduced in patients than in controls (73.5 +/- 38.4% vs. 36.7 +/- 13.1%; p = 0.0061). Mean SAI was also significantly reduced in patients than in controls (65.8 +/- 14.2% vs. 42.8 +/- 16.9%; p = 0.0053). This neurophysiological study suggests that there are alterations in sleepwalkers consistent with an impaired efficiency of inhibitory circuits during wakefulness. This inhibitory impairment could represent the neurophysiological correlate of brain "abnormalities" of sleepwalkers like "immaturity" of some neural circuits, synapses, or receptors.

Dysfunction of arousal systems in sleep-related migraine without aura

Primary headaches are closely related to sleep. Modifications in the patterns of arousal during sleep have been reported in migraine, especially in the nights preceding a headache attack. We aimed at evaluating the pattern of arousal from sleep in a group of patients affected by sleep-related migraine. We enrolled 10 consecutive patients, three males and seven females, aged between 20 and 62 years, who presented frequent attacks of migraine without aura (more than five per month), closely related to sleep (more than one-half of the attacks occurred during sleep, causing an awakening). A control group was studied, matched for age and sex. Patients and controls underwent a full-night polysomnographic study, following adaptation; arousal pattern was studied by the scoring of the high-frequency EEG arousal and by the cyclic alternating pattern (CAP). Migraineurs showed a lower CAP rate in non-rapid eye movement (NREM) sleep and, in particular, a lower number of A1 phases (low-frequency, high-amplitude EEG bursts) compared with the controls. Migraineurs also showed a lower index of high-frequency EEG arousals during rapid eye movement (REM) sleep. The reduction in the CAP rate indicates a lower level of arousal fluctuation in NREM sleep. The reduced arousal index in REM suggests a dysfunction in neural structures involved in both the control of REM sleep and the pathophysiology of migraine, such as the hypothalamus and the brainstem.

Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: direct recording of epidural activity in conscious humans

A magnetic transcranial conditioning stimulus given over the motor cortex at intensities below active threshold for obtaining motor-evoked potentials (MEPs) facilitates EMG responses evoked at rest in hand muscles by a suprathreshold magnetic stimulus given 10-25 ms later. This is known as intracortical facilitation (ICF). We recorded descending volleys produced by single and paired magnetic motor cortex stimulation through high cervical epidural electrodes implanted for pain relief in six conscious patients. At interstimulus intervals (ISIs) of 10 and 15 ms, although MEP was facilitated, there was no change in the amplitude or number of descending volleys. An additional I wave sometimes was observed at 25 ms ISI. In one subject, we also evaluated the effects of reversing the direction of the induced current in the brain. At 10 ms ISI, the facilitation of the MEPs disappeared and was replaced by slight suppression; at 2 ms ISI, there was a pronounced facilitation of epidural volleys. Subsequent experiments on healthy subjects showed that a conditioning stimulus capable of producing ICF of MEPs had no effect on the EMG response evoked by transmastoidal electrical stimulation of corticospinal tract. We conclude that ICF occurs because either 1) the conditioning stimulus has a (thus far undetected) effect on spinal cord excitability that increases its response to the same amplitude test volley or 2) that it can alter the composition (but not the amplitude) of the descending volleys set up by the test stimulus such that a larger proportion of the activity is destined for the target muscle.

In vivo cholinergic circuit evaluation in frontotemporal and Alzheimer dementias

The test of short latency afferent inhibition (SAI) of the motor cortex is helpful in demonstrating dysfunction of central cholinergic circuits in Alzheimer disease (AD). The authors evaluated SAI in 20 patients with frontotemporal dementia (FTD) and compared data with those from 20 patients with AD and 20 controls. SAI was normal in FTD, whereas it was reduced in AD. SAI may represent an additional tool to discriminate FTD from AD.

NCAM is hyposialylated in hereditary inclusion body myopathy due to GNE mutations

The authors found that the neural cell adhesion molecule (NCAM) is hyposialylated in hereditary inclusion body myopathy (HIBM) muscle, as suggested by its decreased molecular weight by Western blot. This abnormality represented the only pathologic feature differentiating HIBM due to GNE mutations from other myopathies with similar clinical and pathologic characteristics. If further confirmed in larger series of patients, this may be a useful diagnostic marker of GNE-related HIBM.

Effects of aging on motor cortex excitability

To determine whether aging is associated with changes in excitability of the cerebral cortex, we evaluated the excitability of the motor cortex with transcranial magnetic stimulation (TMS). We compared TMS related measures obtained in a group of young people with those of a group of old people. Motor evoked potential (MEP) amplitude was significantly smaller in older than in younger controls (1.3+/-0.8 mV versus 2.7+/-1.1 mV; p<0.0071). Mean cortical silent period (CSP) duration was shorter in older than in younger controls (87+/-29 ms versus 147+/-39 ms; p<0.0071). SP duration/MEP amplitude ratios were similar in both groups. Our results are consistent with an impaired efficiency of some intracortical circuits in old age.

Clinical characteristics, course and prognosis of spinal multiple sclerosis

STUDY DESIGN

Retrospective examination.

OBJECTIVE

To define the clinical characteristics and response to therapy of spinal multiple sclerosis (MS).

SETTING

Italy.

METHODS

Retrospective review was performed on 563 patients with clinical definite MS. Selection criteria were two or more spinal cord lesions in the presence of normal magnetic resonance imaging of the brain.

RESULTS

Spinal MS was diagnosed in 13 patients (2.3%) out of 563 with clinical definite MS. There were seven female and six male patients; nine had a relapsing-remitting (RR) and four, a primary progressive (PP) course. All patients were treated with immunosoppressive or immunomodulatory therapy. Mean disease duration in patients with RR-MS was 13.1+/-10.1 years with a mean age at onset of 29.5+/-14.3 years; the mean Expanded Disability Status Scale (EDSS) at the time of the study was 3.5+/-2.5 with a progression index of 0.28. Mean disease duration in patients with PP course was 7+/-6.2 years with a mean age at onset of 56.7+/-10.4 years; the mean EDSS at the time of the study was 6.2+/-2.0 with a progression index of 1.48.

CONCLUSIONS

Patients with spinal RR-MS are characterised by an early disease onset with minimal or moderate disability progression; patients with spinal PP-MS show a late disease onset and more rapid disability progression. In our series of spinal MS patients, disability progression seems to be mainly due to the disease course and age at onset rather than to the site of lesion.

Neurotrophic Factors and Clinical Recovery in Relapsing-Remitting Multiple Sclerosis

Pathogenic autoimmune cells are demonstrated to be able to produce neurotrophic factors during acute phase of multiple sclerosis (MS). In this study, we determined the production of various neurotrophins [brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF), neurotrophin 3 (NT3) and neurotrophin 4 (NT4)] and some pro-inflammatory cytokines [tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)] by unstimulated peripheral blood mononuclear cells (PBMC) in 21 relapsing-remitting MS patients during different phases of disease (stable, relapse and post-relapse). During acute phase of disease, we detected a considerable increase of BDNF, TNF-alpha and IFN-gamma production, while significantly higher levels of GDNF, NGF, NT3 and NT4 were found in post-relapse phase. When neurotrophin production was correlated with clinical outcome (complete or partial recovery from new symptoms), we found a significantly higher BDNF production in relapse phase followed by increased GDNF, NGF, NT3 and NT4 levels during post-relapse phase in subjects with complete remission only. During relapse phase, we detected a significant increase of pro-inflammatory cytokines, that was more evident in patients with partial recovery. The neuroprotective potential of immune cells seems to be inversely correlated with disease duration and with the age of patients.

Multicenter study on carpal tunnel syndrome and pregnancy incidence and natural course

OBJECTIVE

To evaluate the incidence of carpal tunnel syndrome (CTS) in pregnancy through a validated and multiperspective assessment of CTS and to assess the course of carpal tunnel syndrome after pregnancy.

METHODS

During 2000-2001, the Italian CTS study group in 7 Italian centers studied the occurrence of CTS in women during the last period of pregnancy. The group enrolled and followed-up (10-15 months) 63 women during and after pregnancy with multiple measurements of CTS. In addition to the physician-centered and neurophysiologic traditional evaluations, a validated patient-oriented measurement to obtain more comprehensive and consistent data for severity of symptoms and functional impairment was adopted.

RESULTS

CTS was clinically diagnosed in more than half of women (62%). Neurophysiological evaluation provided diagnosis of CTS in around half of women (43% were positive in one hand at least). Comparison of baseline and follow-up data showed a significant spontaneous improvement of patient-oriented and neurophysiologic measurements. Nevertheless, about half of women with CTS during pregnancy still complained of CTS symptoms one year after delivery.

CONCLUSIONS

Our observations confirmed the frequent occurrence of CTS in pregnancy. At follow-up we observed that most CTS cases improve spontaneously without treatment but only in half of women CTS symptoms disappeared one year after delivery.

Theta-burst repetitive transcranial magnetic stimulation suppresses specific excitatory circuits in the human motor cortex

In four conscious patients who had electrodes implanted in the cervical epidural space for the control of pain, we recorded corticospinal volleys evoked by single-pulse transcranial magnetic stimulation (TMS) over the motor cortex before and after a 20 s period of continuous theta-burst stimulation (cTBS). It has previously been reported that this form of repetitive TMS reduces the amplitude of motor-evoked potentials (MEPs), with the maximum effect occurring at 5-10 min after the end of stimulation. The present results show that cTBS preferentially decreases the amplitude of the corticospinal I1 wave, with approximately the same time course. This is consistent with a cortical origin of the effect on the MEP. However, other protocols that lead to MEP suppression, such as short-interval intracortical inhibition, are characterized by reduced excitability of late I waves (particularly I3), suggesting that cTBS suppresses MEPs through different mechanisms, such as long-term depression in excitatory synaptic connections.

Functional involvement of cerebral cortex in human narcolepsy

The pathophysiology of human narcolepsy is still poorly understood. The hypoactivity of some neurotransmitter systems has been hypothesised on the basis of the canine model. To determine whether narcolepsy is associated with changes in excitability of the cerebral cortex, we assessed the excitability of the motor cortex with transcranial magnetic stimulation (TMS) in 13 patients with narcolepsy and in 12 control subjects. We used several TMS paradigms that can provide information on the excitability of the motor cortex. Resting and active motor thresholds were higher in narcoleptic patients than in controls and intracortical inhibition was more pronounced in narcoleptic patients. No changes in the other evaluated measures were detected. These results are consistent with an impaired balance between excitatory and inhibitory intracortical circuits in narcolepsy that leads to cortical hypoexcitability. We hypothesise that the deficiency of the excitatory hypocretin/orexin-neurotransmitter-system in narcolepsy is reflected in changes of cortical excitability since circuits originating in the lateral hypothalamus and in the basal forebrain project widely to the neocortex, including motor cortex. This abnormal excitability of cortical networks could be the physiological correlate of excessive daytime sleepiness and it could be the substrate for allowing dissociated states of wakefulness and sleep to emerge suddenly while patients are awake, which constitute the symptoms of narcolepsy.

Role of motor evoked potentials in diagnosis of cauda equina and lumbosacral cord lesions

OBJECTIVE

To determine the diagnostic value of motor evoked potentials (MEPs) in the diagnosis of lumbosacral cord disorders.

METHODS

MEPs in 37 patients with sensory and motor deficits in the lower limbs were studied. MRI demonstrated spinal cord involvement in 10 patients and cauda equina lesions in 27 patients. A double determination of central motor conduction time (CMCT), calculated as the difference between the latencies of responses evoked by cortical and paravertebral magnetic stimulation and as the difference between the latency of cortical MEP and the total peripheral conduction time calculated from the F-wave latency, enabled discrimination between a delay along the proximal root and a delay along the corticospinal tract. An abnormality of the CMCT calculated with both techniques is indicative of central motor pathway damage, whereas an abnormality of the CMCT calculated from the latency of responses evoked by paravertebral magnetic stimulation associated with a normal CMCT calculated from the F-wave latency suggests a cauda equina lesion.

RESULTS

Neurophysiologic findings strongly correlated with the lesion site documented by MRI (cauda equina or lumbosacral cord). All patients with MR evidence of cord involvement had an abnormality of CMCT calculated with both methods, suggesting a lesion of central motor pathways. Clinical examination often failed to document a spinal cord lesion, suggesting pure peripheral involvement in 5 of the 10 patients with MR evidence of cord lesion.

CONCLUSION

Motor evoked potential recording is an accurate and easily applicable test for the diagnosis of lumbosacral spinal cord lesions.

Effects of vagus nerve stimulation on cortical excitability in epileptic patients

Vagus nerve stimulation (VNS) is used as adjunctive treatment for medically refractory epilepsy, but little is known about its mechanisms of action. The effects of VNS on the excitatory and inhibitory circuits of the motor cortex were evaluated in five patients with epilepsy using single- and paired-pulse transcranial magnetic stimulation (TMS). Patients were examined with the stimulator on and off. VNS determined a selective and pronounced increase in the inhibition produced by paired-pulse TMS with no effects on the excitability by single-pulse TMS.

Motor cortex hyperexcitability to transcranial magnetic stimulation in Alzheimer's disease

OBJECTIVES

Recent transcranial magnetic stimulation (TMS) studies demonstrate that motor cortex excitability is increased in Alzheimer's disease (AD) and that intracortical inhibitory phenomena are impaired. The aim of the present study was to determine whether hyperexcitability is due to the impairment of intracortical inhibitory circuits or to an independent abnormality of excitatory circuits.

METHODS

We assessed the excitability of the motor cortex with TMS in 28 patients with AD using several TMS paradigms and compared the data of cortical excitability (evaluated by measuring resting motor threshold) with the amount of motor cortex disinhibition as evaluated using the test for motor cortex cholinergic inhibition (short latency afferent inhibition) and GABAergic inhibition (short latency intracortical inhibition). The data in AD patients were also compared with that from 12 age matched healthy individuals.

RESULTS

The mean resting motor threshold was significantly lower in AD patients than in controls. The amount of short latency afferent inhibition was significantly smaller in AD patients than in normal controls. There was also a tendency for AD patients to have less pronounced short latency intracortical inhibition than controls, but this difference was not significant. There was no correlation between resting motor threshold and measures of either short latency afferent or intracortical inhibition (r = -0.19 and 0.18 respectively, NS). In 14 AD patients the electrophysiological study was repeated after a single oral dose of the cholinesterase inhibitor rivastigmine. Resting motor threshold was not significantly modified by the administration of rivastigmine. In contrast, short latency afferent inhibition from the median nerve was significantly increased by the administration of rivastigmine.

CONCLUSIONS

The change in threshold did not seem to correlate with dysfunction of inhibitory intracortical cholinergic and GABAergic circuits, nor with the central cholinergic activity. We propose that the hyperexcitability of the motor cortex is caused by an abnormality of intracortical excitatory circuits.

Comparison of descending volleys evoked by transcranial and epidural motor cortex stimulation in a conscious patient with bulbar pain

OBJECTIVE

To compare the pattern of activation of motor cortex produced by transcranial magnetic stimulation and epidural electrical stimulation.

METHODS

The spinal volleys evoked by transcranial magnetic stimulation and epidural electrical stimulation over the cerebral motor cortex were recorded from an electrode inserted into the cervical epidural space of one conscious subject who also had a cortical epidural electrode over the motor area. The volleys were termed D- and I-waves according to their latency. Magnetic stimulation was performed with a figure-of-eight coil and the induced current flowed either in a postero-anterior (PA) or in latero-medial (LM) direction.

RESULTS

At active motor threshold intensity LM magnetic stimulation evoked a D wave whereas PA stimulation evoked an I(1) wave with later I waves being recruited at increasing stimulus intensities. Electrical epidural stimulation evoked both a D wave and I waves. However, the D wave evoked by electrical epidural stimulation had a longer latency than the LM D wave, suggesting either a more proximal site of activation of the pyramidal axon or activation of slightly faster conducting set of corticospinal fibres by LM stimulation. The I3 wave evoked by electrical epidural stimulation also had a longer latency than the PA I3-wave

CONCLUSIONS

Epidural stimulation of the motor cortex can produce repetitive excitation of corticospinal neurones. The order of recruitment of the volleys, and the latency of the D and I3 waves may be slightly different to that seen after transcranial magnetic stimulation.

SIGNIFICANCE

Our findings suggest that there may be subtle differences in the populations of neurones activated by the two forms of stimulation.

The physiological basis of transcranial motor cortex stimulation in conscious humans

Transcranial stimulation of the human motor cortex can evoke several different kinds of descending activity depending on the type of stimulation, the intensity of stimulation and the area of the cortex being stimulated. Thus, transcranial magnetic stimulation preferentially activates different structures than transcranial electrical stimulation. In addition, the response to magnetic stimulation depends on the direction of the induced current in the brain, the waveform of the stimulating current, and the shape of the coil. Stimulation of the lower limb area of motor cortex recruits different elements than stimulation of the upper limb area. These differences occur because different structures in the motor cortex have a differential threshold to the different techniques of stimulation. We have had the opportunity to perform a series of direct recordings of the corticospinal volley evoked by the different techniques of transcranial stimulation from the epidural space of conscious patients with chronically implanted spinal electrodes. These recordings provide insights about the physiological basis of the excitatory and inhibitory phenomena produced by transcranial stimulation.

Direct recording of the output of the motor cortex produced by transcranial magnetic stimulation in a patient with cerebral cortex atrophy

OBJECTIVE

To examine the descending motor activity evoked by transcranial magnetic stimulation (TMS) in a chronic alcoholic patient with a slight atrophy of the peri-central cortex and compare with that observed in neurologically intact subjects.

METHODS

EMGs from the first dorsal interosseous (FDI) muscle, and descending activity from an electrode implanted in the high cervical epidural space for relief of pain were recorded after TMS of the hand area of motor cortex. A figure-of-8 coil was used to induce either a posterior-anterior (PA) or a latero-medial (LM) flow across the central sulcus.

RESULTS

In intact subjects, LM stimulation evoked the earliest volley, which we termed a D wave. This was followed by later, presumed I waves at intervals of about 1.5 ms. At a stimulus intensity of 120% resting threshold (RMT), up to 5 I waves were seen. PA stimulation rarely evoked D waves at intensities up to 120% RMT, but 3 or 4 I waves were visible in all subjects. The patient had an increased resting threshold, and the descending volleys were dominated by a D wave. I waves were unclear, with two possible small peaks at 5.5 and 7.2 ms.

CONCLUSIONS

The lack of I waves in the patient was probably due to an impairment of interneuronal circuitry in the context of the brain damage related to chronic alcohol abuse, and is consistent with a trans-synaptic origin of the I waves in humans. The intact D wave is consistent with the assumption that the D wave represents direct stimulation of the axons of intact corticospinal neurones in the subcortical white matter. The patient's increased RMT reflects the fact that usually multiple descending volleys are needed to discharge resting spinal motoneurones.

Changes in motor cortex excitability in facioscapulohumeral muscular dystrophy

Previous studies found that some patients with severe, early onset facioscapulohumeral muscular dystrophy (FSHD) present epilepsy and mental retardation. This suggests a functional involvement of central nervous system in severe FSHD. It is unknown whether minor functional changes of central nervous system are also present in less severe forms of FSHD. To investigate this, we examined the excitability of neuronal networks of the motor cortex with a range of transcranial magnetic stimulation paradigms in 20 FSHD patients with heterogeneous clinical severity and compared the data with that from 20 age-matched healthy individuals and from 6 age-matched patients with other muscle diseases. There was significantly less intracortical inhibition in FSHD patients (mean responses +/- SD reduced to 58.1+/-43.5% of the test size) than in controls (mean responses +/- SD reduced to 29.3+/-13.5% of the test size; P=0.025) and in patients with other muscle diseases (mean responses +/-SD, reduced to 30.6+/-11.7% of the test size; P=0.046). No significant difference was found between the control group and patients with other muscle diseases (P=0.970).