The diagram schematically shows the relationships between some of the senses involved in post-concussion symptoms.
The diagram explains why symptoms such as headaches, light sensitivity, sound sensitivity or balance can be sourced in many different places.
Each one of the symptoms can be caused or located at the sense organ in the diagram be it the head/brain, brainstem, eyes, hearing, neck or balance centre.
The arrows show reflex pathways or communication lines between the centres. You can see the connections between the sense organs.
The interconnection between the senses in the diagram shows how there can be a different system causing the symptoms in what would logically be the equivalent sensory organ, such as the eyes. In concussion, it is not that often that the sense organ is the primary cause for the symptoms.
Some vision difficulties, for example, can be sourced in part or all at seemingly unrelated sensory system locations and yes, the neck/brainstem is a player in vision.
Light sensitivity, for example, can be the result of various kinds of visual processing or communication difficulties in the brain because of damage to neural pathways from the concussion. The literature suggest that the organ of the eye contributes only 20% of all we see.
For example, visual object location is a composite of information from the organ of the eye and integration of visual processing in the brain. It includes integrating visual information with the auditory equivalent of object location in the hearing centre in the brain and the organ for hearing. The combined visual and hearing information is compared with information about head /body position and movement including the direction of air across the face or ear. All the information is cross matched with data in the emotional centre in the brain and in the area of the brain for working memory. This example is a simplification of the multiplicity of components that combine to give us sight. The same complexity of interconnection exists for hearing, balance, smell and so on.
Clinical tests can show that vision is affected by the neck / brain stem and that the neck/ brain stem is a location for headaches and poor balance.
Clinical tests can show the cranial bones affect vision, neck pain, less often hearing, and it is often a source for headaches.
Clinical tests show that the cervical spine and hearing affect balance and vertigo as distinct from the balance or vestibular centre.
If the vestibular organ is the same as the eye, that is, it contributes 20% of balance control, then the source of balance dysfunction is more likely to be found in the multitude of communication pathways between the senses in the brain than in the organ for balance.
A neuro radiologist colleague has said many times to this therapist that no concussion is the same and because of this there is a separate protocol for concussion evaluations combining PET scan with 3T MRI imaging. This combination of brain imaging can clearly show damaged brain cells and areas of the brain not working. The physiological findings using this imaging protocol shows traumatic brain injuries have no pattern for injury location or laterality. It can affect the white matter or grey matter and be widespread and diffuse nature.
The diffuse nature of the injury and multiple locations explains why neurological evaluations using cranial nerve tests fail to find anything wrong. The wrong interpretation is that that there is nothing wrong. A better interpretation is that the tests could not find a location for the concussion client’s symptoms. A similar conclusion can be drawn for TBI with routine MRI imaging on older MRI machines.
Finally, neuropsychological evaluations are routine in the concussion world and highly valued. They are based on normative data. Bright clever individuals are routinely told that their brains are working fine and yet they continue to report that they have memory difficulties, slowed cognition, loss of cognitive flexibility and in some total loss of visual memory or visualisation ability. One reason for the difference between the expert findings and the client is that the expert does not have a pre-accident base-line for the client. The protocol cannot quantify the loss for the individual. So-called normal individuals are told everything is ok. The loss the individual has sustained goes undetected.
The brain is complex. Concussion injuries are complex which means assessments and treatments need to reflect that complexity and interconnectivity. It also means that some test protocols can’t explain why some symptoms persist.
A seasoned vestibular & neuro physiotherapist with close to 40 yrs clinical experience with a special focus on concussion, head, neck and upper spine pain.