Note 4 - Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Prepaid sales rebates	$ 290	$ 401
Prepaid dues and subscription	49	82
Prepaid insurance	64	94
Prepaid patents	68	85
Prepaid security deposit for lease	65	65
Retainer	32	46
Other	94	113
Total prepaid expenses and other current assets	$ 662	$ 886