Owners of Addison dogs often wonder what is going on when a dog shakes its head vigorously. The dog cannot speak, but a human can - so this article is to give an impression of what the dog feels like.

Addison`s disease causes death by shock. Amongst the many symptoms is a dazed, "other-worldly" experience - particularly when the electrolytes - Sodium (Na) and Potassium (K) - are low. One finds ones consciousness drifting.

One urge, therefore, is to wake oneself up.

A second factor is the loss of any balancing awareness. It is a theory of mine - as yet unproven - that as the blood thickens due to water-loss (which goes hand-in-hand with the Na loss), so does the fluid in the semi-circular canals of the inner ear.

This loss of balance is unpublished elsewhere, although Greenhow spoke often of vertigo - which perhaps started as a translation from the French ("vertige"). This is not quite the same in modern medical English, where vertigo means that the room spins when you turn your head. The better translation would be DIZZINESS.

Case 147 in the Greenhow survey seems to me to be the "tingle-tongue" dizziness of simple low blood-pressure. Other cases suggest the loss of the balancing mechanism. See Greenhow pp. 3, 11, 12, 26, 33, 35, 43, also cases 103, 129, 135, 141, 155, 163.

There is therefore an urge to clear the blockage in the balancing mechanism - to get rid of a sense of "drifting".

An example of the loss of the balancing-mechanism was in 1979 in Saarbrücken, when the fairground came to town. There was Globorama, where images are projected onto the inside of a hollow sphere. There were no seats. When the performance began, Charles found himself sprawled on the floor. Shadowy figures in the audience were turning, and looking down upon him. WHAT A PLONKER! Yet, every time he stood up and looked at the screen he fell over. Charles had discovered that by adapting to the disease, he was staying erect by EYESIGHT. When the visual clues disagreed with reality, he fell over.

Humans are particularly dependent upon balance, with their erect posture. Dogs - on four legs - are less dependent. So human observations of this kind are a sensitive and pertinent demonstration of the mechanisms at work.

In summary, the sensation is one of drowsiness and drifting - without any urge to sleep. One shakes ones head to try to bring oneself back to reality.

It is a sign that the electrolytes are low - but without additional data should not be the cause of panic. An Addison sufferer may be reasonably comfortable, and free of pain, whilst still shaking the head. The symptom should be taken as a clue that the Florinef needs to be slightly increased - but blood-pressure and other tests must confirm this.

A final word. Charles Wehner had no idea that dogs did this. When visiting a restaurant, Charles did this occasionally in the presence of a waiter. The waiter took it to be a "mannerism", and started imitating the head-shaking as a "standing joke". It was only upon reading the k9 newsgroup entries that Charles realised the explanation might be of use to dog-owners.