Note 4 - Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Prepaid sales rebates	$ 401	$ 925
Rent receivable		108
Prepaid rent		130
Prepaid employees’ benefits	8	113
Prepaid dues and subscription	82	130
Prepaid insurance	94	57
Prepaid patents	85	79
Prepaid security deposit for lease	65
Retainer	46
Other	105	218
Total prepaid expenses and other current assets	$ 886	$ 1,760