Note 2 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2019

Notes Tables

Schedule of Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Table Text Block]

(in thousands)	March 31,		December 31,
	2019		2018
Cash and cash equivalents	$	2,932	$	3,183
Restricted cash included in Other assets		475		475
Total cash, cash equivalents, and restricted cash in the statement of cash flows	$	3,407	$	3,658

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	Three Months Ended March 31,
Major distribution or collaboration partner	2019			2018
Distributer A		26	%		21	%
Distributer B		14	%		27	%
Distributer C		17	%		25	%

	March 31,			December 31,
Major distribution or collaboration partner	2019			2018
Distributer A		41	%		32	%
Distributer B		33	%		23	%
Distributer C		13	%		31	%

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

(in thousands except per share)	Three Months Ended March 31,
Numerator	2019			2018
Net loss	$	(4,189	)	$	(2,150	)
Less gain on changes in fair value of warrant liability		—			(214	)
Net loss, diluted	$	(4,189	)	$	(2,364	)
Denominator
Weighted average shares outstanding, basic		17,093			16,406
Net loss per share, basic	$	(0.25	)	$	(0.13	)
Weighted average shares outstanding, basic		17,093			16,406
Effect of dilutive warrants		—			264
Weighted average shares outstanding, diluted		17,093			16,670
Net loss per share, diluted	$	(0.25	)	$	(0.14	)

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

	As of March 31,
(in thousands)	2019		2018
Period end stock options to purchase common stock		2,389		2,433
Period end common stock warrants		544		—
		2,933		2,433

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

Prepaid expenses and other current assets (a)	$	(49	)
Operating lease right-of-use assets		2,239
Other assets (b)		(2	)
Other accrued liabilities (c)		(101	)
Operating lease liability		1,063
Deferred rent		(184	)
Operating lease liability - non-current		1,410