Note 6 - Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued compensation and benefits	$ 726	$ 967
Accrued rent payable	191	205
Accrued clinical trials services	15	75
Accrued inventory supplies	159	391
Accrued other	808	883
Total accrued expenses	$ 1,899	$ 2,521