The `Mean Girls` actress is said to be "fuming" after medical assessments at the UCLA Medical Center - where she is currently undergoing a 90-day stint as part of her sentence for breaching probation - found she may have been misdiagnosed with attention deficit disorder (ADD) and is not suffering from bipolar disorder or addicted to drugs as was previously claimed.

Instead, medics believe it is possible her prescription for Adderall, which treats ADD, led to her erratic behaviour, meaning the 24-year-old star feels her sentence was unfair.

A source said: "Lindsay is fuming - she is really upset that the courts put her through all this."

Although the insider says Lindsay`s representatives are "exploring their options", it is not expected she will be able to gain legal action against the perceived damage to her public image.

Criminal Defence Attorney Steve Cron explained to Fox 411`s Pop Tarts: "No judge or prosecutor could be sued under these circumstances, they have absolute immunity. Judge Revel formulated her opinion of Lindsay based on the information she had at the time from another programme.

"The judge could still be dissatisfied with the report from UCLA and seek independent opinions or insist Lindsay be enrolled in other programmes."

Gossip website TMZ has claimed that doctors at Lindsay`s treatment facility believe Judge Martha Revel - who ordered the actress to spend 90 days in jail and 90 days in rehab for violating the terms of probation set for a 2007 driving under the influence conviction - "overreacted" when she set the `Georgia Rule` star`s sentence.

Earlier this month, the judge voluntarily stepped down from the case and was replaced by Judge Elden Fox.

Lindsay spent just 13 days in jail and is expected not to complete the full stint in rehab.
sections: Celebrities