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While he looks like a ''normal little boy'', an undiagnosed chromosome defect means the 6-year-old has delayed development. Sinclair can only say a few words, and Mr May hoped the therapy could stimulate energy points at the base of the tongue, on the underside.
He did not expect it to be a ''magic wand'', but hoped Sinclair would progress to sentences, rather than saying a few single words.
He was able to comprehend when others spoke, but it was hoped the extent of his mental development would be clearer once his language improved. Even a small improvement would make a big difference, Mr May said.
The trip is planned for August, and would cost about $15,000, including the treatment.
The pair needed to stay reasonably close to the Hong Kong International Tongue Acupuncture Research Clinic, where Sinclair would receive the procedure three times a day, for about two or three minutes each time.
It would be carried out by Prof Sun Jie Guang.
Mr May could have taken Sinclair to Sydney for the therapy, to a practitioner trained by Prof Sun, but preferred to see the man himself.
Prof Sun trained as a doctor in Western medicine, before studying traditional Chinese medicine. He developed tongue acupuncture in the 1980s, finding more than 40 acupuncture points on the tongue.
It had since been used for neurological, cardiovascular, and endocrine diseases. Mr May hoped his story might inspire other parents of children with developmental delay or conditions such as autism and cerebral palsy to try the therapy.
Sinclair's chiropractor, Dr Tat Loo, was supportive of the visit to Hong Kong.
Dr Loo said while he was not an expert in acupuncture, it worked along similar lines as chiropractic treatment in stimulating the nervous system.