Why does yawning cause a paralyzed arm to move?

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"As the hemiplepic patient begins to Yawn his paralysed arm may flex involuntarily at the elbow, the arm is drawn up in front of him and it returns to its resting position as the yawn ceases. During this movement the hand and fingers are said to be held in extension (6, 9,10). Many of our stroke patients had these movements. As they differed in pattern from previous descriptions and as many patients had false ideas about their nature and implications, I decided to investigate the phenomenon."

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"Patients and methods : Forly hemiplegic stroke patients who were attending the out-patient physiotherapy department at Nottingham General Hospital were studied."

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" Thirty-two patients had experienced automatic movements of the hemiplegic arm. In 15 of them, the movements had begun within a month of the stroke but in 4 a yaer or more had elapsed between the stroke and the onset of movements. In most of the patients. the movement started within 6 months of the stroke."
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"ln 2 patients, the movement of the arm was so violent that the hand hit their face."
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"Activities producing associated reactions : In 31 patients, the arm moved involuntarily in association with yawning. The arm movement would begin at the onset of the yawn and subsided as the yawn ended. Fifteen patients had arm movements every time they yawned. Several piatients found that the degree of arm movement was proportional to the size of the yawn. Others noted that yawn-induced arm movements were more likely to occur when they were lying in bed. In some cases, the arm fell to the side quite abruptly at the end of the yawn. One patient had to hold his paralysed arm when he yawned to prevent wrenching of the shoulder by sudden downward arm movement."
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"DISCUSSION Involuntary movements of the affected arm are common in hemiplegia. occurring in 80% of the patients studied...
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To see the whole study go here...

http://webperso.easyconnect.fr/bail...emiplegic2.html

"Although yawning has been considered to be of minor medical importance, it is clearly not without interest and merits much more detailed study."

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So what do you tell the patient who wants to know why his arm moves when he yawns?

The best answer that I've been able to come up with is

The fluctuating pressures of cerebrospinal fluid in the spinal nerve roots.

Yawning causes the cerebrospinal fluid to fluctuate.

To see more on this theory

check it out here...

http://members.shaw.ca/hilaryking/Oldbrain1.htm

I do have some questions regarding this explanation.
After cerebral infarction there should be wallerian degeneration in the 2nd and subsequently in 3rd order neurons.
So even if yawning fluctuates the CSF pressures , it should stimulate the healthy neurons and only the unparalyzed side should move (which it does even without yawning).
Studies have shown that electrical nerve stimulation has restored or improved some movement in hemiplegia/quadriplegia.
If the above explanation is true then yawning should cause involuntary arm movements even in normal individuals also because they have normal tone, unlike a UMN lesion which has increased tone.
I was also thinking in another way , assuming that this explanation is true, as to why normal people do not have limb movement while yawning. It is probably because of the intact cortical as well as basal ganglia and cerebellar circuits so net result is no extra movement.
I do have a theory regarding yawning and arm movement in these patients. They were receiving physiotherapy so they probably did not have or had little muscle and peripheral nerve degeneration. Cerebral infarction had probably destroyed the cortical areas only and probably sparing the subcortical ( thalamic and basal ganglia )and cerebellar circuits (REMEMBER: that classical hemiplegia is MCA stroke which is most common stroke. The brain stem stroke syndromes can also cause hemiplegia but are relatively less common compared to carotid circulation strokes) . Yawning is associated with relative hypercarbia which also produces relatively increased ICP (upper limit of normal) . This could in some way stimulate the spinocerebellar tracts or rubrospinal tracts producing this involuntary movement as a result of the complex interplay of subcortical and cerebellar mechanisms. Firstly the origin of these movements is not cortical because of infarction , so they are not under conscious control.
NET RESULT :
NORMAL INDIVIDUALS : Normal cortical , subcortical , cerbellar mechanisms - so yawning results in no movement
HEMIPLEGICS : NO CORTICAL Mechanism , ONLY Subcortical and Cerebellar- so yawning could cause movement on paralyzed side , but no movement on normal side (since normal side has intact cortical, subcortical and cerebellar circuits)
DRAWBACKS OF THIS EXPLANATION:
i am assuming that most of these hemiplegics are of the common MCA variant . So this explanation may not be true for brain stem stroke syndromes.
I WOULD LIKE TO KNOW THE VIEWS OF ALL INDIVIDUALS ON THIS FORUM REGARDING THIS EXPLANATION

[i]
If the above explanation is true then yawning should cause involuntary arm movements even in normal individuals...

I was also thinking in another way , assuming that this explanation is true, as to why normal people do not have limb movement while yawning. ...

I WOULD LIKE TO KNOW THE VIEWS OF ALL INDIVIDUALS ON THIS FORUM REGARDING THIS EXPLANATION [/B]

I think it does.
I thinks its an inhibitory response or a reflex such as maintaining balance while walking, its done automatically to control the arms.

I have not noticed the arms movements myself but I have noticed a movement or a quivering in the chest muscles while yawning. (involuntary yet I'm normal) I think if the arms were relaxed and not in flexion that just the movement of the chest muscles alone would move the arms.

I brought this up on a parkinson's forum as I expected renegade movements would be more noticed by people with parkinsons, one person had this to say...

"This is one of my biggest frustrations, when I yawn my arms and legs go wild with shaking but only if I am standing or sitting. Lying down in bed is safe."

and another normal this...

B. Myers
Member
Posts: 454
From: here and there
Registered: Sep 2002
posted 02-20-2004 05:16 PM
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Yes, yawning makes my hands and feet tremble, always has - I don't remember a time when it didn't, so I haven't thought of connecting the trembling with PD. I suppose it could mean that I've had mild PD for years, or maybe I just yawn so hugely and luxuriously that it makes me tremble?
That, at least, is how it feels!

J Neurol Sci. 1994 Nov:

"We observed a stroke patient with an infarct of the internal capsule interrupting the pyramidal tract who stretched his hemiplegic arm during spontaneous and apomorphine-induced yawning. The putative mechanism by which yawning can induce the paradoxical motor response of the plegic arm in the patient might be the functional efficiency of a pathway projecting directly from the stimulated basal ganglia to lower motor systems in the brainstem."

i actually just saw this yesterday when i admitted a patient. it was weird. 64 yo man admitted for a right ACA infarct with hemorrhagic conversion.

somnolent, awake, oriented x 3, able to follow commands. right gaze preference. left flaccid hemiplegia. when he yawned however, he flexed his left arm ~ 2+/5 strength. afterwards, i tried to test his strength again and it was again 0/5. full strength on the right.

That's odd. Arm should be in the MCA area... how much hemorrhage was there to cause a complete hemiplegia?

Any new perspectives?