“Baroreceptors are a type of mechanoreceptor allowing for the relay of information about blood pressure within the autonomic nervous system. Information is passed in rapid sequence to maintain blood pressure within a preset, normalized range. Arterial baroreceptors include those located within the carotid sinuses in the neck. Arterial baroreceptors function to inform the autonomic nervous system to changes in blood pressure within the arterial system. Rapid decreases in blood pressure, such as in times of orthostatic hypertension result in decreased stretching of the artery wall which ultimately results in the baroreceptors causing an increase in blood pressure. The opposite is found to be true of increased blood pressure.”
It also seems that well-functioning baroreceptors have a role in dampening pain and stress responses:
“When the baroreceptors located in the carotid body are stimulated by the cardiac cycle, in particular during the systolic phase [when the heart is contracting], the nociceptive stimulus [relating to the sensation or perception of pain] is attenuated by the activation of baroreceptors. The baroreceptors’ activity also affects muscle tone, as it decreases the activity of the sympathetic nervous system, reducing the contractile state.”
Since pain and abnormal muscle rigidity are common features in PD, one wonders if baroreceptor dysfunction may be playing a role. Conversely, when there is issues with rigidity and stiffness in the muscles and fascia of this area on the neck itself, as is often the case with PD, could the resulting compressions/restrictions cause the baroreceptors to malfunction? This seems like a reasonable conclusion when we learn that the baroreceptors and their feedback to the nervous system is indeed sensitive to imposed pressures and forces. Actually, there is a very interesting connection here with the affects of weather on the symptoms of PD. Some time ago, I looked into the the science behind how weather, and air pressure in particular, really does have profound effects on symptoms of chronic conditions, as many of us with such issues will anecdotally already know. However, a scientific journal article goes further and finds relatively small oscillations or fluctuations in air pressure can have an impact too, through the baroreceptors mainly in the neck:
“Our basic idea is that the baroreceptors of the blood pressure control system are not indifferent to changes in external air pressure. The ambient air presses immediately two carotid sinuses located symmetrically just underneath the skin of the neck… variations in the external air pressure sway the reference point of the baroreceptors, thereby feeding a false signal into the baroreflex loop… changes in peripheral resistance and corresponding changes in arterial pressure and cardiac output [and nervous system states] under exposure to [air pressure oscillations] may result…”
Furthermore, there are known medical issues with pressure on the carotid sinus:
“…carotid sinus syndrome … in which the carotid sinus is particularly sensitive to external pressure. Increased pressure on the carotid sinus, such as from a particularly tight collar or sustained turn of the head, results in significant hypotension and possibly syncope [fainting, passing out]. Carotid sinus sensitivity can result in syncope with stimulation of the carotid sinus externally, such as with shaving.”
“Stimulation of the carotid sinus via a slap or a strike, to induce (usually temporary, but sometimes lethal) loss of consciousness is a theatrical self-defense technique, and is often taught in martial arts such as karate.”
For me, this leaves open questions about the impacts of tight muscles and fascia in the area of the neck containing the baroreceptors in the neurology and physiology of PD.
There are also important chemical sensors (chemoreceptors) in the neck which are part of autonomic breathing function, in a structure called the “carotid body”, a small cluster of chemoreceptor cells located in the bifurcation (fork) of the common carotid artery, which detects changes of the partial pressure of arterial oxygen, and also of carbon dioxide. The carotid bodies can influence breathing by releasing a variety of neurotransmitters, including acetylcholine and dopamine.
At this point, I hope this is enough to pique the interest of many people with PD in the potential role of these chemical sensors in the neck. given that dopamine is the very neurotransmitter we are short of, and also because most of us have very poor breathing habits – fast and shallow chest breathing through the mouth. In fact, I found so much pertinent information about the carotid bodies that there is enough material for a follow up article dedicated to this, which I will publish in due course. For now the relevant question is again how do constrictions, fascial adhesions, hypertonic muscles, etc. in the neck, impact the carotid bodies, and hence affect breathing?
It would seem to me that there are a number of very vicious circles and negative feedback loops between neck stiffness/rigidity/pain and neck immobilization and posture in PD, which not only impact on each other, but also have neurological and physiological implications much more broadly, including on nervous system, blood pressure and breathing. The principal strategy for progressive symptom reduction would therefore be to increase and maintain mobilization of the neck and to improve posture as much as possible, through daily exercises and therapies, and to address any old injuries elsewhere on the body which may be impacting on posture and hence neck strain.
Dr Farias provides a suite of daily exercises which help to reduce these type of neck problems over time, especially designed for, and tailored to the different types of, cervical dystonia. Many people around the world report that doing his exercise classes daily reduces the symptoms and pain of their neck dystonia, and can eventually even lead to a full recovery. This works through a process of neuroplasticity, which re-wires the connections between the muscles and the brain through movement therapy.
Although at first one might feel that the neck has become so stiff, it can’t move it all, even starting with micromovements or just thinking about moving the head, can be enough to gradually increase range of movement. A useful “trick” I found is to imagine drawing a figure of eight with the chin. I tried this and found it was much easier to move my head when thinking about it this way. Even when my neck is very rigid and stiff during an “off” period, I find although my chin barely moves, it does make micromovements and I can feel the muscles of my neck/shoulder at least twitch (engage/disengage), so this helps to get mobilization started. I’ve found many variations on this theme which can help: imagine drawing the figure of eight with the nose instead, and then with the forehead/third eye point – that one makes me a bit dizzy which means my vestibular system is being engaged, which is a good thing usually. Or try drawing different shapes such as circles with chin, nose or third eye point. More random motions can be achieved by trying to sign your name with your chin, say.
As well as the muscles per se, it is likely that the fascia health of the neck will also need attention. I have personally been using a modality called Block Therapy which uses a specially designed block of wood to apply pressure to various parts of the body for fascial decompression. I have been blocking my sternum, clavice, pectoral, shoulder and neck regions, for a total of fifteen minutes daily since about Christmas 2019. I have seen profound changes in this time, as shown in the month-by-month photo record below.
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