Note 10 - Stockholders' Equity (Deficit) - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Granted, shares (in shares)	581,614	582,353
Nonvested, shares (in shares)	706,980	799,376	835,297
The 2011 and 2017 Plans [Member]
Balance, shares (in shares)	4,212,481	4,595,247
Balance, weighted average exercise price (in dollars per share)	$ 59.59	$ 62.43
Outstanding, weighted average remaining contractual term (Year)	5 years 2 months 12 days	5 years 1 month 6 days	4 years 6 months
Granted, shares (in shares)	581,614	582,353
Granted, weighted average exercise price (in dollars per share)	$ 4.39	$ 2.43
Granted, weighted average remaining contractual term (Year)	9 years 1 month 6 days	9 years 2 months 12 days
(Expired), shares (in shares)	(375,414)	(965,119)
(Expired), weighted average exercise price (in dollars per share)	$ 66.89	$ 38.63
Outstanding, aggregate intrinsic value	$ 1,105	$ 1,046
Balance, shares (in shares)	4,418,681	4,212,481	4,595,247
Balance, weighted average exercise price (in dollars per share)	$ 51.7	$ 59.59	$ 62.43
Nonvested, shares (in shares)	706,980
Nonvested, weighted average exercise price (in dollars per share)	$ 4.83
Nonvested, weighted average remaining contractual term (Year)	8 years 8 months 12 days
Nonvested, aggregate intrinsic value	$ 315
Exercisable, shares (in shares)	3,711,701
Exercisable, weighted average exercise price (in dollars per share)	$ 60.63
Exercisable, weighted average remaining contractual term (Year)	4 years 6 months
Exercisable, aggregate intrinsic value	$ 790