|

|
| Neuroplasticity and Visual Field Loss |
| |
The brain's ability to constantly process new images and the organisation of knowlege and of emotional, sensitive, sensory and motor function (also called neuroplasticity) is well know to every person. Healthy people experience this in their daily life of automatic learning, those that are ill experience it during rehabilitation following an injury to the brain. Undeniable progress in the allocation of certain anatomical brain regions concerning the transcribed performance of the human brain (for example the allocation of the left frontal lobe controls expressive language or the occiput controls vision) sometimes mask the large anatomical variable and the redundant biological predisposition of human brain functions. Many brain functions, especially significant functions are located doubly (on both sides of the brain), stretch anatomically with frequent use or are "moveable" in bordering regions of the brain. It is therefore fully understandable that lost brain functions, despite a complete destruction of the functions of damaged nerve cells, can be reclaimed. For brain functions such as speech or motor function this is well know and established the basis for rehabilitation using speech therapy and physiotherapy.
For damage along the human visual pathway this principle has been observed or utilised less. This is all the more surprising because vision impairment has such a considerable impact on the independence of everyday life. Patients with visual impairments on the basis of brain damage are often no longer in a position to confidently drive a car, they can no longer read nor comprehend with the necessary speed, (although their intellectual apprehension remains unaffected), work at a computer monitor nor be able to move around freely in their habitual environment (for example crossing the road with safety and confidence or managing to move around in closed rooms).
Similar to the safe and standardised therapy models of physiotherapy and speech therapy the current tests conducted on patients with visual impairments caused by brain damage show that a
consistent treatment in the form of a computerised vision therapy can lead to considerable improvements. The patients benefit in doing so from a broadening of their limited visual field as well as from an increase in their reaction in the damaged visual field areas. Both phenomenon suitably lead to a significant improvement in their daily lives and a higher degree of independence. Current clinical studies concentrate primarily on these computerised vision therapies to improve their everyday life.
The curative process in the sense of clinically seen (and experienced by patients) improvements of nerve failure following damage to the central nervous system can be discussed and understood primarily in the neuroanatomically functional categories of (1) recovery of the functional integrity of initially damaged nerve structures and (2) neuroplasticity (the taking over of lost nerve function by other/not damaged cerebral nerve tissue).
A recuperation of directly damaged neuronal structures, which will lead to a functional recovery is - at least according to the currently propagated model up for discussion - noticeable within a few days, in other words within the timeframe of a hospital stay. (This neurobiological train of thought is based on the possibility of incomplete damage to nerve structures which would lead to an impairment of neuronal functions but not to irreversible damages of the nerve tissue itself, for a layman best illustrated with the metaphor "a car without petrol").
The second category mentioned above ("neuroplasticity") implies that through an intracerebral reorganisation following irreversible damage to nerve structures ("total write-off") lost functions can still be at least partially recovered. An intracerebral reoganisation can be achieved in the form of neighbouring neurons taking over in the ipsilateral half of the brain as well as through activation of corresponding contralateral brain regions. Irrespective of the the fact that the extent as well as the intra and inter-individual variance of such a curative process are insufficiently described, the effects are well documented. Equally well documented is the dependence of clinically relevant degrees of the so-called curative process upon external stimuli, namely all therapy measures for rehabilitation of the affected function impairments. For a layperson this can be explained as the process of learning. People of all ages can basically learn a variety of concrete motor, abstract or other achievements at least in part, in other words using the neuronal plasticity of the brain to learn and be able to reproduce new functions. At the same time practicing with professional caretakers (tennis teacher/physiotherapist, driving instructor/occupational therapist, voice teacher/speech therapist) more frequently and regularly will lead to better results than autodidactic practicing and rare/irregular training.
Duration of Defect Regeneration/Recovery
Paralysis of the musculature in extremeties caused by strokes (or cerebral bleeding) and other singular cerebral injuries (for example traumatic brain injury) reverse either (1) quickly, within minutes or hours, (2) short-term, within days or a few weeks, or (3) within a framework of several months. This pattern principly applies to all cerebral impairments (even impairments of speech or other cerebral functions such as vision). The recovery duration is therefore not linear but shows corresponding peaks on a time scale. In the (1) mentioned recovery pattern probably presents the above-mentioned first category of recovery of non-irreversibly damaged nerve cells, while the remaining recovery patterns would be more readily understood in the context of neuroplasticity. Early and short-term recovery are as a rule more complete and result in minor disabilities rather than long-term recovery (several months) For patients that still suffer paralysing disabilities (or other cerebral disfunctions such as speech or vision problems) several weeks following an incidence the complete recovery of all functions is significantly less probable. All curative processes (clinically noticeable improvements) have in common that beyond the early phase of approximately 4 weeks they are clearly fewer than is the case in the early recovery phases. Beyond a time limit of about 6 months all improvements undertaken are as a rule less noticeable, although patients and relatives nonetheless experience these as valueable and helpful.
Special Recommendations for the Treatment of Damages to the Central Nervous System (for example: stroke)
The abovementioned reasons make it plausible that for all damages (paralysis, coordination disturbances, speech and other neuropsychological impairments, impairments of the visual system and many more) which have a debilitating effect
VRT should be applied and started soon. |
| |
 |
|
