Melbourne Victory captain Carl Valeri has been diagnosed with an inflammatory condition affecting part of his brain but is responding well to initial treatment, the club said Tuesday.

The veteran 31-year-old, who has been capped 52 times by Australia, has not played since November 28 when he complained of balance issues.

"Carl developed a medical condition two weeks ago that affects his balance and coordination," club doctor Krishant Naidu said in a statement, adding that he had a viral upper respiratory tract infection in the week leading up to this.

"He has had specialist reviews with an ear, nose and throat surgeon and a neurologist with extensive investigations. To date, these have revealed an inflammatory condition affecting part of his brain."

The full results of further tests, which will determine the exact nature of the illness, are not expected for another fortnight.

The A-League star, a defensive midfielder, joined Victory in 2014 after an extensive stint in Italy, most recently with Serie B side Ternana.