Note 14 - Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

January 1,	Number of shares
2012		2,502
2013		2,871
2014		4,128
2015		5,463
2016		7,257
2017		12,623
2018		106,076
Total additional shares		140,920

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year ended December 31,
	201 8			201 7
Risk free interest rate	2.47%	-	2.71%	1.86%	-	2.04%
Expected term (in years)	5.24	-	5.57	5.32	-	6.36
Dividend yield		-%			-%
Expected volatility	108.81%	-	126.43%	112.86%	-	114.19

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Underlying Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life Remaining in Years		Aggregate Intrinsic Value
Outstanding as of January 1, 2018		172,510		$	49.27			$
Granted		611,668			2.39
Forfeited		(795	)		562.55
Outstanding as of December 31, 2018		783,383			12.14		9.17	$
Exercisable as of December 31, 2018		317,042			24.39		8.97	$
Vested and expected to vest		783,383			12.14		9.17	$

Liability Options [Member]

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Year Ended December 31, 2018
General and administrative	$	869,515
Research and development		540,510
Total stock compensation expense	$	1,410,025

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31 , 2018
Risk free interest rate	2.51	-	2.94%
Expected term (in years)	4.5	-	5.0
Stock price	$1.02	-	$2.38
Dividend yield		%
Expected volatility	122.0	-	125.0%

Employee Stock Option [Member]

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Year Ended December 31,
	201 8		201 7
General and administrative	$	809,110	$	621,668
Research and development		244,386		164,882
Total stock compensation expense	$	1,053,496	$	786,550