Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Current Assets [Line Items]
Prepaid consulting, subscriptions and other expenses	$ 265	$ 290
Prepaid insurances	237	351
Prepaid conferences and travel	104	94
Clinical consulting services refund receivable	0	46
Prepaid clinical research organizations	0	46
Total	$ 606	$ 827

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