Note 13 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ended
	December 31,
	2019			2018
Income tax provision (benefit) at statutory rate		(21	)%		(21	)%
State income taxes, net of federal benefit		(4	)%		(4	)%
Change in valuation allowance		(39	)%		23	%
Debt restructuring		6	%		0	%
Limitation on net operating loss and credit carryovers		56	%		0	%
Other		2	%		2	%
Effective tax rate		0	%		0	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	16,688		$	31,759
Capitalized start up costs		3,225			3,555
Research and development credits		527			951
Accruals and reserves		532			1,272
Fixed assets and depreciation		128			69
Total deferred tax assets		21,100			37,606
Deferred tax liabilities:
Valuation allowance		(21,100	)		(37,606	)
Net deferred tax assets	$	-		$	-

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	Year Ended
	December 31,
	2019			2018
Balance at the beginning of the year	$	450		$	397
Additions (deletions) based upon tax positions related to the current year		(227	)		53
Balance at the end of the year	$	223		$	450