Note 3 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Embedded derivative liability	$ 4,000
Fair Value, Recurring [Member]
Cash equivalents		$ 103,000
Restricted cash held as a certificate of deposit	324,000	324,000
Deposit held as a certificate of deposit	151,000	151,000
Total assets	475,000	578,000
Warrant liability	3,902,000	178,000
Embedded derivative liability	4,000
Total liabilities	3,906,000	178,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents		103,000
Restricted cash held as a certificate of deposit	324,000	324,000
Deposit held as a certificate of deposit	151,000	151,000
Total assets	475,000	578,000
Warrant liability
Embedded derivative liability
Total liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents
Restricted cash held as a certificate of deposit
Deposit held as a certificate of deposit
Total assets
Warrant liability
Embedded derivative liability
Total liabilities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents
Restricted cash held as a certificate of deposit
Deposit held as a certificate of deposit
Total assets
Warrant liability	3,902,000	178,000
Embedded derivative liability	4,000
Total liabilities	$ 3,906,000	$ 178,000