Fatigue in patients with acquired brain damage

Fatigue is a complex, multidimensional syndrome that is prevalent in patients with acquired brain damage and has a negative impact on the neurorehabilitation process. It presents from early stages after the injury, and may persist over time, regardless of whether sequelae have resolved. Fatigue is conditioned by upper neuronal circuits, and is defined as an abnormal perception of overexertion. Its prevalence ranges from 29% to 77% after stroke, from 18% to 75% after traumatic brain injury, and from 47% to 97% after brain tumours. Fatigue is associated with factors including female sex, advanced age, dysfunctional families, history of specific health conditions, functional status (eg, fatigue prior to injury), comorbidities, mood, secondary disability, and the use of certain drugs. Assessment of fatigue is fundamentally based on such scales as the Fatigue Severity Scale (FSS). Advances have recently been made in imaging techniques for its diagnosis, such as in functional MRI. Regarding treatment, no specific pharmacological treatment currently exists; however, positive results have been reported for some conventional neurorehabilitation therapies, such as bright light therapy, neurofeedback, electrical stimulation, and transcranial magnetic stimulation. This review aims to assist neurorehabilitation professionals to recognise modifiable factors associated with fatigue and to describe the treatments available to reduce its negative effect on patients.

Fatigue in patients with acquired brain damage

Fatigue is a complex, multidimensional syndrome that is prevalent in patients with acquired brain damage and has a negative impact on the neurorehabilitation process. It presents from early stages after the injury, and may persist over time, regardless of whether sequelae have resolved. Fatigue is conditioned by upper neuronal circuits, and is defined as an abnormal perception of overexertion. Its prevalence ranges from 29% to 77% after stroke, from 18% to 75% after traumatic brain injury, and from 47% to 97% after brain tumours. Fatigue is associated with factors including female sex, advanced age, dysfunctional families, history of specific health conditions, functional status (eg, fatigue prior to injury), comorbidities, mood, secondary disability, and the use of certain drugs. Assessment of fatigue is fundamentally based on such scales as the Fatigue Severity Scale (FSS). Advances have recently been made in imaging techniques for its diagnosis, such as in functional MRI. Regarding treatment, no specific pharmacological treatment currently exists; however, positive results have been reported for some conventional neurorehabilitation therapies, such as bright light therapy, neurofeedback, electrical stimulation, and transcranial magnetic stimulation. This review aims to assist neurorehabilitation professionals to recognise modifiable factors associated with fatigue and to describe the treatments available to reduce its negative effect on patients.

Cortical reorganization after spinal cord injury: always for good?

Plasticity constitutes the basis of behavioral changes as a result of experience. It refers to neural network shaping and re-shaping at the global level and to synaptic contacts remodeling at the local level, either during learning or memory encoding, or as a result of acute or chronic pathological conditions. 'Plastic' brain reorganization after central nervous system lesions has a pivotal role in the recovery and rehabilitation of sensory and motor dysfunction, but can also be "maladaptive". Moreover, it is clear that brain reorganization is not a "static" phenomenon but rather a very dynamic process. Spinal cord injury immediately initiates a change in brain state and starts cortical reorganization. In the long term, the impact of injury - with or without accompanying therapy - on the brain is a complex balance between supraspinal reorganization and spinal recovery. The degree of cortical reorganization after spinal cord injury is highly variable, and can range from no reorganization (i.e. "silencing") to massive cortical remapping. This variability critically depends on the species, the age of the animal when the injury occurs, the time after the injury has occurred, and the behavioral activity and possible therapy regimes after the injury. We will briefly discuss these dependencies, trying to highlight their translational value. Overall, it is not only necessary to better understand how the brain can reorganize after injury with or without therapy, it is also necessary to clarify when and why brain reorganization can be either "good" or "bad" in terms of its clinical consequences. This information is critical in order to develop and optimize cost-effective therapies to maximize functional recovery while minimizing maladaptive states after spinal cord injury.

A practical guide to diagnostic transcranial magnetic stimulation: report of an IFCN committee

Transcranial magnetic stimulation (TMS) is an established neurophysiological tool to examine the integrity of the fast-conducting corticomotor pathways in a wide range of diseases associated with motor dysfunction. This includes but is not limited to patients with multiple sclerosis, amyotrophic lateral sclerosis, stroke, movement disorders, disorders affecting the spinal cord, facial and other cranial nerves. These guidelines cover practical aspects of TMS in a clinical setting. We first discuss the technical and physiological aspects of TMS that are relevant for the diagnostic use of TMS. We then lay out the general principles that apply to a standardized clinical examination of the fast-conducting corticomotor pathways with single-pulse TMS. This is followed by a detailed description of how to examine corticomotor conduction to the hand, leg, trunk and facial muscles in patients. Additional sections cover safety issues, the triple stimulation technique, and neuropediatric aspects of TMS.

CB1 receptor antagonism/inverse agonism increases motor system excitability in humans

CB1 receptor is highly expressed in cerebral structures related to motor control, such as motor cortex, basal ganglia and cerebellum. In the spinal cord, the expression of CB1 receptors has also been observed in ventral motor neurons, interneurons and primary afferents, i.e., in the cells that may be part of the circuits involved in motor control. It is known that the antagonist/inverse agonist of CB1 receptors Rimonabant penetrates the blood-brain barrier and produces a broad range of central psychoactive effects in humans. Based on the occurrence of central effects in humans treated with Rimonabant and on the location of CB1 receptors, we hypothesized that the application of Rimonabant can also affect the motor system. We tested the effects of a single dose of 20mg of Rimonabant on the excitability of motor cortex and of spinal motor neurons in order to detect a possible drug action on motor system at cortical and spinal levels. For this purpose we use classical protocols of transcranial magnetic and electrical stimulation (TMS and TES). Single and paired pulse TMS and TES were used to assess a number of parameters of cortical inhibition and cortical excitability as well as of the excitability of spinal motor neurons. We demonstrated that a single oral dose of 20mg of Rimonabant can increase motor system excitability at cortical and spinal levels. This opens new avenues to test the CB1R antagonists/inverse agonists for the treatment of a number of neurological dysfunctions in which can be useful to increase the excitability levels of motor system. Virtually all the disorders characterized by a reduced output of the motor cortex can be included in the list of the disorders that can be treated using CB1 antagonists/reverse agonists (e.g. stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, fatigue syndromes, parkinsonisms, etc.).

Spinal direct current stimulation modulates the activity of gracile nucleus and primary somatosensory cortex in anaesthetized rats

Afferent somatosensory activity from the spinal cord has a profound impact on the activity of the brain. Here we investigated the effects of spinal stimulation using direct current, delivered at the thoracic level, on the spontaneous activity and on the somatosensory evoked potentials of the gracile nucleus, which is the main entry point for hindpaw somatosensory signals reaching the brain from the dorsal columns, and of the primary somatosensory cortex in anaesthetized rats. Anodal spinal direct current stimulation (sDCS) increased the spontaneous activity and decreased the amplitude of evoked responses in the gracile nucleus, whereas cathodal sDCS produced the opposite effects. At the level of the primary somatosensory cortex, the changes in spontaneous activity induced by sDCS were consistent with the effects observed in the gracile nucleus, but the changes in cortical evoked responses were more variable and state dependent. Therefore, sDCS can modulate in a polarity-specific manner the supraspinal activity of the somatosensory system, offering a versatile bottom-up neuromodulation technique that could potentially be useful in a number of clinical applications.

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.

[Acute transverse myelitis in seven patients with systemic lupus erythematosus]

INTRODUCTION

Although the association between transverse myelitis and systemic lupus erythematosus is rather infrequent, it is important to take this form of clinical presentation into account because it is a serious complication, which can potentially be treated but even when dealt with in the early stages does not always have a good prognosis.

PATIENTS AND METHODS

We conducted a retrospective review over the past 13 years of the cases that have been admitted to our specific centre for the treatment of spinal cord injuries that were diagnosed as suffering from myelitis associated with disseminated lupus erythematosus. Demographic and clinical data, together with data about acute phase and maintenance treatments, as well as the patients' progress and sequelae are described.

RESULTS

The case reports of seven patients, all of whom were young females, are studied. In two cases, myelitis was the initial presentation of lupus. The main disorder was at the dorsal, followed by the cervical, levels. Only two patients had a favourable long-term progression from the neurological point of view (both managed to walk) despite acute treatment with high doses of intravenous corticoids, and regardless of the fact that cyclophosphamide was later used.

CONCLUSIONS

Myelitis associated to lupus is a rare manifestation but, owing to its important functional repercussions, it must be taken into account when faced with an acute clinical picture involving the spinal cord; this is particularly the case when it occurs in young females, with or without a previous diagnosis of autoimmune disease.

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.

Effects of baclofen on temperature perception in humans

The aim of this study was to evaluate the effect of chronic consumption of the GABAB agonist baclofen on temperature perception in humans. We investigated temperature perception thresholds to detect warm and cold stimuli in a group of 21 patients with spinal cord injury, who were chronically consuming oral baclofen at different daily doses to treat spasticity. Temperature perception thresholds were assessed above the level of the lesion, using a psychophysical approach based on the ability of the subjects to perceive precisely quantified sensory stimuli (quantitative sensory testing, QST). The data were compared with a control group of healthy subjects, not receiving baclofen. We found that chronic baclofen consumption increased temperature perception thresholds for both cold and warm stimuli in a dose-dependent manner. Temperature perception thresholds did not depend on the level of the lesion nor on the duration of baclofen treatment, suggesting that our finding represent normal GABAB-mediated modulation in spared nervous structures. We conclude that GABAB therefore plays a role in temperature perception in humans.

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.

Cortical correlates of TMS-induced phantom hand movements revealed with concurrent TMS-fMRI

We studied an amputee patient who experiences a conscious sense of movement (SoM) in her phantom hand, without significant activity in remaining muscles, when transcranial magnetic stimulation (TMS) is applied at appropriate intensity over the corresponding sector of contralateral motor cortex. We used the novel methodological combination of TMS during fMRI to reveal the neural correlates of her phantom SoM. A critical contrast concerned trials at intermediate TMS intensities: low enough not to produce overt activity in remaining muscles; but high enough to produce a phantom SoM on approximately half such trials. Comparing trials with versus without a phantom SoM reported phenomenally, for the same intermediate TMS intensities, factored out any non-specific TMS effects on brain activity to reveal neural correlates of the phantom SoM itself. Areas activated included primary motor cortex, dorsal premotor cortex, anterior intraparietal sulcus, and caudal supplementary motor area, regions that are also involved in some hand movement illusions and motor imagery in normals. This adds support to proposals that a conscious sense of movement for the hand can be conveyed by activity within corresponding motor-related cortical structures.

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.

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.

Reduced sensorimotor inhibition in the ipsilesional motor cortex in a patient with chronic stroke of the paramedian thalamus

OBJECTIVE

Unilateral or bilateral paramedian infarction in the region of the thalamus and upper midbrain may lead to hypersomnia. To determine whether unilateral infarction of the paramedian thalamus leads to changes in excitability of ipsilesional primary motor hand area (M1).

METHODS

We describe a patient with chronic stroke of the right dorsomedian and intralaminar thalamic nuclei, who suffered from mild persistent hypersomnia. We studied the excitability of the right and left M1 with transcranial magnetic stimulation (TMS) in the patient, and in 10 healthy controls.

RESULTS

In contrast to healthy controls, contralateral electrical stimulation of the median nerve failed to induce short-latency afferent inhibition (SAI) in the ipsilesional M1. Other measures of corticomotor excitability and somatosensory evoked potentials were normal.

CONCLUSIONS

The selective loss of ipsilateral SAI in a patient with paramedian thalamic stroke suggests that during wakefulness, the intact paramedian thalamus facilitates the excitability of intracortical inhibitory circuits, which process thalamocortical sensory inputs in the ipsilateral M1. This preliminary finding suggests that measurements of SAI may provide a means of probing the integrity of some neural pathways, which are involved in the control of wakefulness and arousal.

SIGNIFICANCE

In addition to the established role of the paramedian thalamus in arousal and memory, our observation suggests that thalamocortical projections from the paramedian thalamus contribute to the integration of sensory input at the cortical level during wakefulness.

Neurophysiological predictors of long term response to AChE inhibitors in AD patients

BACKGROUND

In vivo evaluation of cholinergic circuits of the human brain has recently been introduced using a transcranial magnetic stimulation (TMS) protocol based on coupling peripheral nerve stimulation with motor cortex TMS (short latency afferent inhibition, SAI). SAI is reduced in Alzheimer's disease (AD) and drugs enhancing cholinergic transmission increase SAI.

METHODS

We evaluated whether SAI testing, together with SAI test-retest, after a single dose of the acetylcholinesterase (AChE) inhibitor rivastigmine, might be useful in predicting the response after 1 year treatment with rivastigmine in 16 AD patients.

RESULTS

Fourteen AD patients had pathologically reduced SAI. SAI was increased after administration of a single oral dose of rivastigmine in AD patients with abnormal baseline SAI, but individual responses to rivastigmine varied widely, with SAI change ranging from an increase in inhibition of approximately 50% of test size to no change. Baseline SAI and the increase in SAI after a single dose of rivastigmine were correlated with response to long term treatment. A normal SAI in baseline conditions, or an abnormal SAI in baseline conditions that was not greatly increased by a single oral dose of rivastigmine, were invariably associated with poor response to long term treatment, while an abnormal SAI in baseline conditions in conjunction with a large increase in SAI after a single dose of rivastigmine was associated with good response to long term treatment in most of the patients.

CONCLUSIONS

Evaluation of SAI may be useful for identifying AD patients likely to respond to treatment with AChE inhibitors.

Short-lasting impairment of temperature perception by high frequency rTMS of the sensorimotor cortex

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) has become a useful tool for investigating and even modulating human brain function. RTMS of the human motor cortex can produce changes in excitability that outlast the period of stimulation. To investigate the persistent effect of high-frequency rTMS of sensorimotor cortex (SM1) on somatosensory function.

METHODS

We evaluated the thermal thresholds (cold and warm sensation) in 14 normal subjects before and after a short train of 5Hz rTMS over the SM1 or occipital cortex (OC).

RESULTS

Threshold for cold perception was increased immediately after rTMS of the left SM1 and no effects at all were noticed after OC stimulation. There was a slight, not significant, increase of warm threshold immediately after the rTMS of the left SM1 and no effects at all were noticed after OC stimulation.

CONCLUSIONS

High frequency rTMS over primary sensorimotor cortex seems to modulate sensory function related to thermal (cold) perception.

SIGNIFICANCE

The method may be useful for both the study of normal human physiology of temperature perception and for rTMS based manipulation of brain plasticity in patients with sensory disturbances.

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.