Selected Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Current Assets [Line Items]
Prepaid insurance	$ 351	$ 358
Other prepaid expenses	290	185
Prepaid conferences, travel and other expenses	94	295
Clinical consulting services refund receivable	46	0
Prepaid clinical research organizations	46	1,677
Total	$ 827	$ 2,515

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