Spinalcord injury (SCI) is one of the most devastating states of infirmityencountered by today’s health care. It is a catastrophic injury especially dueto the unique role of the spinal cord as a nerve centre1. It is alow incidence high cost disability requiring tremendous changes in individual’slifestyle 2.
It results in the impairment of motor and/or sensoryfunction below and at the level of injury. The extent of an individual’simpairment varies according to the level of lesion, location and severity ofinjury3. A spinal cord lesion at the cervical level often results intetraplegia, with motor, sensory and autonomic function loss in arms, trunk,legs and pelvic organs4. Approximately one-half of all individualswith spinal cord injury have tetraparesis due to cervical injury1.SCIresults in reduction in supraspinal, intraspinal and afferent sources and thesechanges further results in reduction in descending drive and this reduced rateof transmission of relevant information from motor cortex to the spinal cordlimits the performance5.Investigations have suggested a consequentreduction in size of cortical area6, 7 as well as the posteriorshift in individuals with SCI compared to non-disabled individuals. Thisposterior shift provides evidence that individuals with SCI may rely moreheavily on other, more posterior cortical areas, such as sensory cortex, whichcontributes to the corticospinal tract 8.SCIat cervical level has higher prevalence as compared to injury at thoracic andlumbar level 9.
One of the most devastating aspects of spinal cordinjury at cervical level is the impairment of arm and hand function, and thishas a great impact on the level of independence 10. Also therehabilitation program, duration of hospitalization, and degree ofself-independence depend to a large part on the impaired function of upperlimbs. Thus, the extent and severity of impaired upper limb function intetraplegia is of crucial significance for self-independence11.
Thehand is a valuable tool through which we control and manipulate our environmentand express ideas and talents. It also has an important function of providingsensory feedback to the central nervous system. The hand cannot functionwithout the brain to control it; likewise, the encapsulated brain needs thehand as a primary tool of expression. The entire upper limb is a subservient tothe hand. Any loss of function in the upper limb, regardless of the segment,ultimately translates into diminished function of its most distal joints12.Thesystem’s complexity and our dependence on the upper extremity for dailyactivities, is reflected in the relatively large proportion of the sensorimotorcortex dedicated to the control of our hands.
Normal hand function is of utmostimportance for an individual’s independence. Loss of hand function can severelyaffect the activities of daily living (ADL) one can perform. It also tends tocompromise an individual’s ability to participate in work, social and familylife13. Thesedeficits in hand functions are primarily due to a loss of descending motorpathways responsible for fine control of hand and fingers, secondary plasticorganization create further loss 14. An ability to effectively usethe hand is critical to independence and quality of life15. Injuryto cervical spinal cord adversely affects the arm and hand function to avarying degree depending on the level and severity of injury.
A completecervical SCI results in very specific deficits in movements of hand and wrist,however the amount of hand function remaining after an incomplete cervical SCIgreatly varies. Approximately 61% of individuals with cervical spinal cordinjury are functionally incomplete, and incomplete cervical SCI is the mostcommon form of SCI (34.3% of all cases of individuals with spinal cord injury) 16.Recoveryof function after SCI largely depends on preservation of some anatomicconnections and physiologic re-organization of the brain and spinal cord 8.Factors that determine the recovery in traumatic SCI include initialneurological level, initial motor strength and whether the injury isneurologically complete or incomplete 17.
Most of the recoveryoccurs within the first 6 months post injury, with the greatest rate of changeoccurring within first 3 months. Motor strength improvement continues duringthe second year at a slower pace and to a smaller degree17, 18.Impairedhand function significantly limits the ability of individuals with cervical SCIto perform manual ADL. The ability to do simple tasks reduces dependency onothers, improves potential for employment and enhances quality of life.Evidences suggest that intensive task-specific training can enhance handfunction in people with tetraplegia. It is believed that therapy provides thedamaged spinal cord with excitation from the sensorimotor cortex along withintensive sensory input from the periphery.
Neural bombardment of this kind onthe damaged spinal cord may promote neural plasticity and may provide thecritical stimulus required to elicit neurophysiologic and structuralre-organisation of the relevant pathways19.SCIdisrupts both axonal pathways and segmental spinal cord circuitry producingsevere motor, sensory and autonomic impairments at and below the level ofinjury. Significant recovery often occurs in the first year following SCI.
Theamount and extent of recovery depends on a number of factors including thelevel and extent of injury, post injury medical and surgical care and rehabilitativeinterventions. Activity-dependent plasticity plays a major role in mediatingthis recovery. Rehabilitative interventions after neural injury affect thisplasticity at several levels:- Behavioural (recovery of sensory, motor orautonomic function)- Physiological (normalization of reflexes,strengthening of motor-evoked potentials)- Structural/ neuroanatomical (axonalsprouting, dendritic sprouting, neurogenesis)- Cellular (synaptogenesis, synapticstrengthening)- Molecular (up-regulation of neurotransmittersand neurotrophic factors, alterations in gene expression).Reorganizationoccurs spontaneously following the spinal cord lesion, caudal to injury, aroundthe lesion, rostral to injury and in supra spinal structures after bothcomplete and incomplete injury20.
In incomplete SCI lesions,information may still pass through the level of the lesion on spared fibretracts, but this information maybe fragmented or distorted. Maximizing thefunction of these spared fibres is one method to improve motor function16.A second mechanism underlying recovery of function is physiologicalreorganization of the brain and spinal cord motor networks.
Although spontaneous regeneration of lesionedfibres is limited in the adult CNS, rehabilitative therapies can promoteplasticity both rostral and caudal to injury in the spinal cord by activatingthe nervous system and influencing multiple substrates20. Recoveryof function by both spontaneous and secondary to intense rehabilitativetreatments is sustained by plasticity and rewiring in the injured brain inadults. Neurons in the brain increase their firing rates when a subjectobserves movements performed by other persons. Activation of this mirror-neuronsystem, including areas of the frontal, parietal and temporal lobes, can inducecortical reorganization and contributes to functional recovery. Virtual-Realitybased Neurorehabilitation are novel and potentially useful technologies thatallow users to interact in three dimensions with a computer-generated scenario(a virtual world), engaging the mirror-neuron system21.Inthe subacute stages, intervention for the upper limb targets relearning ofmotor abilities using intensive task-specific training22. Skillslearning after SCI draws upon spared neural networks for motor, sensory,perception, planning, memory motivation, reward, language and higherlevel-cognitive functions as well as progressive practice of subtasks ineveryday activities using physical and cognitive cues with feedback aboutperformance and results to increase participation23,24.
Patientsmust have some access to voluntary movement for motor intervention to work23.Recentadvancement in the computer-game technology provides innovative ways ofencouraging patients to engage in intensive task-specific training19.Virtual reality (VR) is a computer-based, interactive, multisensory simulationenvironment that occurs in real time. It presents users with opportunities toengage that appear similar to real world objects and events. These environmentsare three dimensional and are of two types- immersive and non-immersive22,24.
Immersive VR systeminvolves the whole body in the synthetic world by means of devices such ashead-mounted display (HMD)22,24,25, or large screen projector (LSP),or cave (BNAVE) systems, where the environment is projected on a concavesurface to create a sense of immersion. They also use environments such asvideo capture systems (e.g., IREX), where the users view themselves as anavatar in the scene on a computer or television screen.
Non-immersive VR system users interact todifferent degrees with the environment displayed on a computer screen, with orwithout interface devices such as a computer mouse or haptic devices such ascyber gloves/ cyber grasps, joysticks or force sensors22,24. Non-immersivesystems engage only a single limb or sensory modality. They create less senseof “presence”25.
Thecornerstones of VR technologies are “interactivity” and “immersion”26.Interactivity is defined as theextent to which users can participate in modifying the form and content of amediated environment in real time. The three factors that contribute tointeractivity are: speed, whichrefers to the rate at which input can be assimilated into the mediatedenvironment; range, which refers tothe number of possibilities for action at any given time; and mapping, refers to the way in whichhuman actions are connected to actions within a mediated environment27.Immersion refers to that the user hasa strong “sense of presence”, whichis the illusion of going into the computer-generated world and depends on theconvergence of multisensory input (vision, auditory, and tactile) in thevirtual environment22. This environment can be either temporally orspatially distant “real” environment such as a distant space viewed through avideo camera or an animated “world” created in a video game27.Virtualreality, whether immersive or non-immersive, has the potential to createstimulating and fun environments and develop a range of skills and task-basedtechniques to sustain participant interest and motivation. This results inbetter movement outcomes for rehabilitation purposes, demonstrating a greaterrange of functional improvements, including both active and passive upper limbjoint range of motion, and a transfer of therapy gains into activities of dailyliving25.Advantages of VRRehabilitation1.
VRprovides a realistic28, non-threatening and positive learningexperience which can be tailored to the individual’s level of ability22,28.2. Itis both fun and motivating by providing feedback in the form of visual andauditory information22,28. Haptic feedback devices include glovesand joysticks that simulate the feel of forces, surfaces and textures as usersinteract with virtual objects. Feedback can either be absolute (correct/incorrect) or graded information (error score, deviation from optimum)28.3. Itallows for interactive observation of avatar movements captured on the screenand combine features of increasing rehabilitation intensity for induction ofneuroplasticity21,