Can overactive thyroid be a misdiagnosis of meningitis?

Not likely: The findings are very different, and the pace of the disorders are also different. Meningitis is acute, associated with fever, neck stiffness, headache, perhaps delirium or coma, and is associated with an infection with abnormal spinal fluid. Thyroid disorders are more gradual, and, in absence of an unusually active thyroiditis, fairly easy for your doc to deal with.