Spinal of motor and/or sensory function below and at

Spinal
cord injury (SCI) is one of the most devastating states of infirmity
encountered by today’s health care. It is a catastrophic injury especially due
to the unique role of the spinal cord as a nerve centre1. It is a
low incidence high cost disability requiring tremendous changes in individual’s
lifestyle 2. It results in the impairment of motor and/or sensory
function below and at the level of injury. The extent of an individual’s
impairment varies according to the level of lesion, location and severity of
injury3. A spinal cord lesion at the cervical level often results in
tetraplegia, with motor, sensory and autonomic function loss in arms, trunk,
legs and pelvic organs4. Approximately one-half of all individuals
with spinal cord injury have tetraparesis due to cervical injury1.

SCI
results in reduction in supraspinal, intraspinal and afferent sources and these
changes further results in reduction in descending drive and this reduced rate
of transmission of relevant information from motor cortex to the spinal cord
limits the performance5.Investigations have suggested a consequent
reduction in size of cortical area6, 7 as well as the posterior
shift in individuals with SCI compared to non-disabled individuals. This
posterior shift provides evidence that individuals with SCI may rely more
heavily on other, more posterior cortical areas, such as sensory cortex, which
contributes to the corticospinal tract 8.

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SCI
at cervical level has higher prevalence as compared to injury at thoracic and
lumbar level 9. One of the most devastating aspects of spinal cord
injury at cervical level is the impairment of arm and hand function, and this
has a great impact on the level of independence 10. Also the
rehabilitation program, duration of hospitalization, and degree of
self-independence depend to a large part on the impaired function of upper
limbs. Thus, the extent and severity of impaired upper limb function in
tetraplegia is of crucial significance for self-independence11.

The
hand is a valuable tool through which we control and manipulate our environment
and express ideas and talents. It also has an important function of providing
sensory feedback to the central nervous system. The hand cannot function
without the brain to control it; likewise, the encapsulated brain needs the
hand as a primary tool of expression. The entire upper limb is a subservient to
the hand. Any loss of function in the upper limb, regardless of the segment,
ultimately translates into diminished function of its most distal joints12.

The
system’s complexity and our dependence on the upper extremity for daily
activities, is reflected in the relatively large proportion of the sensorimotor
cortex dedicated to the control of our hands. Normal hand function is of utmost
importance for an individual’s independence. Loss of hand function can severely
affect the activities of daily living (ADL) one can perform. It also tends to
compromise an individual’s ability to participate in work, social and family
life13. 

These
deficits in hand functions are primarily due to a loss of descending motor
pathways responsible for fine control of hand and fingers, secondary plastic
organization create further loss 14. An ability to effectively use
the hand is critical to independence and quality of life15. Injury
to cervical spinal cord adversely affects the arm and hand function to a
varying degree depending on the level and severity of injury. A complete
cervical SCI results in very specific deficits in movements of hand and wrist,
however the amount of hand function remaining after an incomplete cervical SCI
greatly varies. Approximately 61% of individuals with cervical spinal cord
injury are functionally incomplete, and incomplete cervical SCI is the most
common form of SCI (34.3% of all cases of individuals with spinal cord injury) 16.

Recovery
of function after SCI largely depends on preservation of some anatomic
connections and physiologic re-organization of the brain and spinal cord 8.
Factors that determine the recovery in traumatic SCI include initial
neurological level, initial motor strength and whether the injury is
neurologically complete or incomplete 17. Most of the recovery
occurs within the first 6 months post injury, with the greatest rate of change
occurring within first 3 months. Motor strength improvement continues during
the second year at a slower pace and to a smaller degree17, 18.

Impaired
hand function significantly limits the ability of individuals with cervical SCI
to perform manual ADL. The ability to do simple tasks reduces dependency on
others, improves potential for employment and enhances quality of life.
Evidences suggest that intensive task-specific training can enhance hand
function in people with tetraplegia. It is believed that therapy provides the
damaged spinal cord with excitation from the sensorimotor cortex along with
intensive sensory input from the periphery. Neural bombardment of this kind on
the damaged spinal cord may promote neural plasticity and may provide the
critical stimulus required to elicit neurophysiologic and structural
re-organisation of the relevant pathways19.

SCI
disrupts both axonal pathways and segmental spinal cord circuitry producing
severe motor, sensory and autonomic impairments at and below the level of
injury. Significant recovery often occurs in the first year following SCI. The
amount and extent of recovery depends on a number of factors including the
level and extent of injury, post injury medical and surgical care and rehabilitative
interventions. Activity-dependent plasticity plays a major role in mediating
this recovery. Rehabilitative interventions after neural injury affect this
plasticity at several levels:

–        
Behavioural (recovery of sensory, motor or
autonomic function)

–        
Physiological (normalization of reflexes,
strengthening of motor-evoked potentials)

–        
Structural/ neuroanatomical (axonal
sprouting, dendritic sprouting, neurogenesis)

–        
Cellular (synaptogenesis, synaptic
strengthening)

–        
Molecular (up-regulation of neurotransmitters
and neurotrophic factors, alterations in gene expression).

Reorganization
occurs spontaneously following the spinal cord lesion, caudal to injury, around
the lesion, rostral to injury and in supra spinal structures after both
complete and incomplete injury20. In incomplete SCI lesions,
information may still pass through the level of the lesion on spared fibre
tracts, but this information maybe fragmented or distorted. Maximizing the
function of these spared fibres is one method to improve motor function16.
A second mechanism underlying recovery of function is physiological
reorganization of the brain and spinal cord motor networks.  Although spontaneous regeneration of lesioned
fibres is limited in the adult CNS, rehabilitative therapies can promote
plasticity both rostral and caudal to injury in the spinal cord by activating
the nervous system and influencing multiple substrates20.

Recovery
of function by both spontaneous and secondary to intense rehabilitative
treatments is sustained by plasticity and rewiring in the injured brain in
adults. Neurons in the brain increase their firing rates when a subject
observes movements performed by other persons. Activation of this mirror-neuron
system, including areas of the frontal, parietal and temporal lobes, can induce
cortical reorganization and contributes to functional recovery. Virtual-Reality
based Neurorehabilitation are novel and potentially useful technologies that
allow users to interact in three dimensions with a computer-generated scenario
(a virtual world), engaging the mirror-neuron system21.

In
the subacute stages, intervention for the upper limb targets relearning of
motor abilities using intensive task-specific training22. Skills
learning after SCI draws upon spared neural networks for motor, sensory,
perception, planning, memory motivation, reward, language and higher
level-cognitive functions as well as progressive practice of subtasks in
everyday activities using physical and cognitive cues with feedback about
performance and results to increase participation23,24. Patients
must have some access to voluntary movement for motor intervention to work23.

Recent
advancement in the computer-game technology provides innovative ways of
encouraging patients to engage in intensive task-specific training19.
Virtual reality (VR) is a computer-based, interactive, multisensory simulation
environment that occurs in real time. It presents users with opportunities to
engage that appear similar to real world objects and events. These environments
are three dimensional and are of two types- immersive and non-immersive22,
24.  Immersive VR system
involves the whole body in the synthetic world by means of devices such as
head-mounted display (HMD)22,24,25, or large screen projector (LSP),
or cave (BNAVE) systems, where the environment is projected on a concave
surface to create a sense of immersion. They also use environments such as
video capture systems (e.g., IREX), where the users view themselves as an
avatar in the scene on a computer or television screen.  Non-immersive VR system users interact to
different degrees with the environment displayed on a computer screen, with or
without interface devices such as a computer mouse or haptic devices such as
cyber gloves/ cyber grasps, joysticks or force sensors22,24. Non-immersive
systems engage only a single limb or sensory modality. They create less sense
of “presence”25.

The
cornerstones of VR technologies are “interactivity” and “immersion”26.
Interactivity is defined as the
extent to which users can participate in modifying the form and content of a
mediated environment in real time. The three factors that contribute to
interactivity are: speed, which
refers to the rate at which input can be assimilated into the mediated
environment; range, which refers to
the number of possibilities for action at any given time; and mapping, refers to the way in which
human actions are connected to actions within a mediated environment27.
Immersion refers to that the user has
a strong “sense of presence”, which
is the illusion of going into the computer-generated world and depends on the
convergence of multisensory input (vision, auditory, and tactile) in the
virtual environment22. This environment can be either temporally or
spatially distant “real” environment such as a distant space viewed through a
video camera or an animated “world” created in a video game27.

Virtual
reality, whether immersive or non-immersive, has the potential to create
stimulating and fun environments and develop a range of skills and task-based
techniques to sustain participant interest and motivation. This results in
better movement outcomes for rehabilitation purposes, demonstrating a greater
range of functional improvements, including both active and passive upper limb
joint range of motion, and a transfer of therapy gains into activities of daily
living25.

Advantages of VR
Rehabilitation

1.     VR
provides a realistic28, non-threatening and positive learning
experience which can be tailored to the individual’s level of ability22,28.

2.     It
is both fun and motivating by providing feedback in the form of visual and
auditory information22,28. Haptic feedback devices include gloves
and joysticks that simulate the feel of forces, surfaces and textures as users
interact with virtual objects. Feedback can either be absolute (correct/
incorrect) or graded information (error score, deviation from optimum)28.

3.     It
allows for interactive observation of avatar movements captured on the screen
and combine features of increasing rehabilitation intensity for induction of
neuroplasticity21,