Flushing Ears with Cold Water Can Treat Somatoparaphrenia

Somatoparaphrenia is a condition whereby a person denies that a limb or an entire side of the body belongs to them, even if provided with irrefutable proof. This condition usually is accompanied by left-sided paralysis and anosognosia (denial or lack of awareness) of the paralysis often due to a parietal stroke.

What is interesting is that flushing the left ear with cold water (caloric vestibular stimulation) can temporarily treat/resolve somatoparaphrenia. Specifically, the protocol is flushing into the left ear canal 60cc of cold water (20 degrees Celsius) for one minute. During the stimulation, the patient is laid down and head tilted forward 30 degrees. If properly done, clear horizontal nystagmus with leftward slow phase can be seen for about 3 minutes.

Normally, flushing the ear in this manner is routinely performed as part of balance testing (ENG) to determine whether a person's dizziness is due to an inner ear problem or not.

In any case, how does vestibular stimulation help with somatoparaphrenia? I don't quite understand it myself, but according to one reference:

"vestibular input takes part in building up and updating the representation of egocentric space." [link]

Whatever that means...

References:
Can vestibular caloric stimulation be used to treat apotemnophilia? Med Hypotheses. 2007;69(2):250-2. Epub 2007 Feb 9.

Partial Remission of Hemiplegia and Somatoparaphrenia Through Vestibular Stimulation in a Case of Unilateral Neglect. Cortex Volume 28, Issue 2, June 1992, Pages 203–208