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Noninvasive brain stimulation can modulate neural processing within the motor cortex and thereby might be beneficial in the rehabilitation of hemispatial neglect after stroke.
We review the pertinent literature regarding the use of transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation in order to facilitate recovery of hemispatial neglect after stroke.
Twenty controlled trials (including 443 stroke patients) matched our inclusion criteria. Methodology and results of each study are presented in a comparative approach. Current data seem to indicate a better efficiency of repetitive transcranial magnetic stimulation, compared to tDCS to ameliorate hemispatial neglect after stroke.
Noninvasive brain stimulation has the potential to facilitate recovery of hemispatial neglect after stroke, but until today, there are not enough data to claim its routine use.
Neurologists use a variety of tests to detect subtle upper motor neuron lesion causing a mild motor impairment of the upper limb. The forearm and index finger rolling tests are some of these. Their sensitivity varies, but in general these tests appear to be more likely to be abnormal in mild motor impairment of the arm and hand due to a cortico-spinal tract lesion than tests of power, muscle tone or reflexes. Thumb rolling involves more distal limb segments than forearm rolling and distal limb segments are typically more affected than proximal limb segments after cerebral lesions to the cortico-spinal tract.
Thumb rolling was tested, in comparison to pronator drift, forearm rolling and index finger rolling, for its sensitivity to detect a cerebral lesion of the cortico-spinal tract in 17 consecutive patients with mild pure motor stroke affecting only one arm and hand.
Thumb rolling is more sensitive (88%) than pronator drift (47%), forearm rolling (65%) and index finger rolling (65%) to detect a cerebral lesion of the cortico-spinal tract in mild pure motor stroke of the upper limb.
The thumb rolling test may be a valuable adjunct clinical test to detect a subtle lesion of the cortico-spinal tract causing mild pure motor stroke of the arm and hand when the remainder of routine neurological examination is unremarkable.
This chapter reviews impairments of grasping and other fine motor tasks following disorders of the somatosensory system. The first part reports findings from transient anesthesia induced experimentally in healthy human subjects. The second part summarizes studies on the effects of lesions to the peripheral sensory system. Findings in patients with sensory deficits following polyneuropathy or carpal tunnel syndrome are differentiated from chronic complete somatosensory deafferentation. The latter group of very rare subjects provides the unique possibility of investigating the function of the motor system deprived of sensory input. The last part summarizes the effects of central lesions due to stroke or cerebral palsy that frequently affect the somatosensory system. The results for various motor tasks including prehensile movements are reported. Specific emphasis is placed on analyses of grip-force control during object manipulation since somatosensory feedback is particularly important for these activities and ample research has been performed during the last few years, enabling comparisons between patient groups.
Clarifying the role of sensory information in the control of voluntary movement and force production is one of the most essential questions in sensorimotor research. The most obvious way to investigate this question is to study the effects of damage to the sensory system on movement execution. Indeed, there was controversy about the effects of a complete lack of sensory information at the beginning of the 20th century.
It is widely held that schizophrenia is associated with a variety of subtle sensory and motor impairments – so called neurological soft signs – that may impact on manual dexterity. Neurological soft signs (NSS) in schizophrenia appear to be part of the underlying disorder. The motor deficit of the hand, however, may also worsen as a side effect of antipsychotic treatment. Within the theoretical framework of internal models schizophrenia has been associated with a deficit of self-monitoring and awareness of action. Deficient monitoring of the sensory consequences of voluntary movement may be directly related to the motor deficit to be found in schizophrenia. This chapter summarizes kinetic and kinematic aspects of impaired manual dexterity in schizophrenia and discusses the motor disability within the context of internal models for the sensorimotor processing of voluntary actions.
Early in the 20th century, Bleuler (1908) and Kraepelin (1919) described several motor abnormalities in schizophrenia, such as problems in the sequencing and spacing of steps when walking and dyscoordination of hand and arm movements when performing handiwork and crafts. In this era antipsychotic drugs did not exist and, consequently, these early clinical observations cannot simply be considered a side effect of antipsychotic treatment. Today, deficits of fine motor performance, also referred to as neurological soft signs (NSS), are still observed in a substantial proportion of schizophrenic subjects, but their nature is still not completely understood and their semiology is not easily distinguishable from side effects of antipsychotic treatment.
Precise control of grasping when manipulating objects depends on intact function of the cerebellum. Given its stereotyped cytoarchitecture, the widespread connections with cortical and subcortical sensorimotor structures and the neural activity of cerebellar Purkinje cells during sensorimotor tasks, the cerebellum is considered to play a major role in the establishment and maintenance of sensorimotor representations related to grasping. Such representations are necessary to predict the consequences of movements. This chapter summarizes anatomical and theoretical aspects, electrophysiological and behavioral data characterizing the cerebellum, a key player in the processing of healthy grasping and in its dysfunction.
The anatomy of the cerebellum and its relation to the control of grasping
The cerebellum has attracted the attention of theorists and modelers for many years. The attraction is that the regular cytoarchitecture of the cerebellar cortex, with only one output cell and four main classes of interneurons, and the functional cerebellar circuitry have been very well documented (Wolpert et al., 1998). The circuitry of the cerebellum is unique by its stereotyped geometric arrangement and its modular organization, highly reminiscent of a machinery designed to process neuronal information in a unique manner (Ito, 2006). The cerebellum appears highly foliated, and this foliation is the reason for subdivision into smaller units (Larouche & Hawkes, 2006). From a structural standpoint, the cerebellum is made of pairs of nuclei embedded in white matter and surrounded by a mantle of cortex (Colin et al., 2002).
The numerous skeletal and muscular degrees of freedom of the hand provide the human with an enormous dexterity that has not yet been achieved by any other species on earth. The human hand can take on a huge variety of shapes and functions, providing its owner with a powerful hammer at one time or a delicate pair of forceps at another. The universal utility of the hand is even more enhanced by the ability to amplify the function of the hand by using tools. True opposition between the thumb and index finger is only observed in humans, the great apes and Old World monkeys. The human thumb is much longer, relative to the index finger, than the thumb of other primates and this allows humans to grasp and manipulate objects between the tips of the thumb and index finger. Humans have more individuated muscles and tendons with which to control the digits and have evolved extensive cortical systems for controlling the hand. In addition to its manipulative function the hand is a highly sensitive perceptive organ, orchestrated by myriads of tactile and somatosensory receptors, which enables humans to perceive the world within their reach. Taken together all these phylogenetic developments have provided humans with the ability to interact with each other, make love and war, and also to shape the world.
Stroke is the leading cause of disability in the adult worldwide. The most common neurological impairment following stroke is weakness or loss of sensibility of the extremities contralateral to the side of the brain lesion. Only about 40% of affected individuals regain full recovery; the remaining 60% have persistent neurological deficits that impact on their social functioning in private and community life. By now, much of our clinical and scientific interest is focused on stroke prevention and acute stroke therapy. In contrast, there is less effort in developing novel strategies for hand motor rehabilitation after stroke. This is surprising since about two-thirds of stroke survivors are left with permanent sensory or motor impairment. This chapter discusses the intrinsic capacity of the cortical motor system for reorganization and gives an overview of established and novel concepts for sensorimotor rehabilitation of the hand after stroke.
Stroke is the leading cause of disability in the adult worldwide (Kolominsky-Rabas et al., 2001). The annual incidence of stroke is 100–300 per 100,000 (Broderick et al., 1998). The most common impairment following stroke is weakness of the limbs contralateral to the side of the brain lesion (Kelly-Hayes et al., 1998). Only about 40% of stroke survivors recover completely (Hankey et al., 2002) and among the remaining 60% permanent sensory and/or motor disability of the hand constitutes a major problem (Stein, 1998).
The clinical spectrum of idiopathic normal pressure hydrocephalus (INPH) comprises gait impairment, cognitive decline and urinary incontinence, all associated with ventricular enlargement and normal cerebrospinal fluid (CSF) pressure on random spinal taps. There is significant variation in the clinical presentation and progression of the disorder and correct diagnosis frequently represents a challenge to the clinical neurologist. Several reports have suggested that the motor disability to be found in INPH may also involve the upper limbs and recent reports provide direct kinetic evidence for this suggestion. Grip-force analysis may also allow an objective evaluation of the beneficial effects of therapeutic strategies in this entity. This chapter reviews the pertinent literature upon the kinetic assessment of upper limb motor disability in the diagnosis and therapy of INPH.
The symptom complex of INPH
Idiopathic normal pressure hydrocephalus (INPH), first described by Hakim & Adams (1965) and Adams et al. (1965), is characterized by the clinical triad of gait disorder, dementia and urinary incontinence, all in the presence of ventriculomegaly and normal cerebrospinal fluid (CSF) pressure on random lumbar puncture. The cause of INPH is not known. When the clinical syndrome occurs as a result of other diseases, such as hemorrhage, traumatic brain injury, cerebral infarction or meningitis, it is referred to as secondary normal pressure hydrocephalus (Gallia et al., 2006). The incidence of INPH has been reported to be about two cases per 100,000 individuals (Vanneste et al., 1992; Krauss & Halve, 2004).
The human hand can take on a huge variety of shapes and functions, providing its owner with a powerful hammer at one time or a delicate pair of forceps at another. The universal utility of the hand is even more enhanced by the ability to amplify the function of the hand by using tools. To understand and appreciate how the human brain controls movements of the hand, it is important to investigate both the healthy motor behaviour and dysfunction during everyday manipulative tasks. This book provides a contemporary summary of the physiology and pathophysiology of the manipulative and exploratory functions of the human hand. With contributions from scientists and clinical researchers of biomechanics, kinesiology, neurophysiology, psychology, physical medicine and rehabilitation, it covers the development of healthy human grasping over the lifespan, the wide spectrum of disability in the pathological state and links basic motor research with modern brain sciences.