Note 12 - Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
	2019			2018			2019			2018
Net loss	$	(5,260	)	$	(6,548	)	$	(12,236	)	$	(13,105	)
Series B and C preferred dividend		—			—			—			(339	)
Net loss attributable to common stockholders – diluted calculation	$	(5,260	)	$	(6,548	)	$	(12,236	)	$	(13,444	)
Shares used to compute net loss per share – basic and diluted		16,249,032			7,141,189			12,748,665			6,038,001
Net loss per share – basic and diluted	$	(0.32	)	$	(0.92	)	$	(0.96	)	$	(2.23	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Options to purchase common stock		1,965,910		978,495		1,466,495		802,885
Warrants to purchase common stock		13,064,514		10,914		8,340,589		9,195
Warrant to purchase convertible preferred stock		—		—		—		1,191
Series B and C convertible preferred stock outstanding, including cumulative dividends		—		—		—		285,797
Series A convertible preferred stock outstanding		—		—		—		16,391
Convertible promissory notes, related party (as converted)		—		—		—		247,557
Total potentially dilutive securities excluded from denominator of the diluted earnings per share computation		15,030,424		989,409		9,807,084		1,363,016