Note 4 - Stockholders' Equity (Deficit), Stock Options and Warrants - Summary of Status of Options and Warrants Outstanding (Details)	12 Months Ended
	Dec. 31, 2018 shares
Shares, options (in shares)	3,669,277
Shares, warrants (in shares)	3,626,643
Warrant One [Member]
Shares, warrants (in shares)	221,292
Weighted average remaining life, warrants (Year)	4 years 335 days
Warrant Two [Member]
Shares, warrants (in shares)	1,063,935
Weighted average remaining life, warrants (Year)	3 years 277 days
Warrant Three [Member]
Shares, warrants (in shares)	697,946
Weighted average remaining life, warrants (Year)	3 years 310 days
Warrant Four [Member]
Shares, warrants (in shares)	1,071,776
Weighted average remaining life, warrants (Year)	4 years 273 days
Warrant Five [Member]
Shares, warrants (in shares)	86,086
Weighted average remaining life, warrants (Year)	4 years 273 days
Warrant Six [Member]
Shares, warrants (in shares)	385,000
Weighted average remaining life, warrants (Year)	3 years 21 days
Warrant Seven [Member]
Shares, warrants (in shares)	94,084
Weighted average remaining life, warrants (Year)	1 year 244 days
Warrant Eight [Member]
Shares, warrants (in shares)	2,529
Weighted average remaining life, warrants (Year)	215 days
Warrant Nine [Member]
Shares, warrants (in shares)	2,850
Weighted average remaining life, warrants (Year)	222 days
Warrant Ten [Member]
Shares, warrants (in shares)	222
Weighted average remaining life, warrants (Year)	310 days
Warrant Eleven [Member]
Shares, warrants (in shares)	59
Weighted average remaining life, warrants (Year)	43 days
Warrant Twelve [Member]
Shares, warrants (in shares)	862
Weighted average remaining life, warrants (Year)	32 days
Warrant Thirteen [Member]
Shares, warrants (in shares)	3,626,643
Weighted average remaining life, warrants (Year)
Stock Options One [Member]
Shares, options (in shares)	201,908
Weighted average remaining life, options (Year)	10 years
Stock Options Two [Member]
Shares, options (in shares)	60,000
Weighted average remaining life, options (Year)	9 years 332 days
Stock Options Three [Member]
Shares, options (in shares)	10,000
Weighted average remaining life, options (Year)	9 years 109 days
Stock Options Four [Member]
Shares, options (in shares)	3,000
Weighted average remaining life, options (Year)	9 years 138 days
Stock Options Five [Member]
Shares, options (in shares)	191,753
Weighted average remaining life, options (Year)	9 years 7 days
Stock Options Six [Member]
Shares, options (in shares)	149,110
Weighted average remaining life, options (Year)	9 years 43 days
Stock Options Seven [Member]
Shares, options (in shares)	23,585
Weighted average remaining life, options (Year)	9 years 277 days
Stock Options Eight [Member]
Shares, options (in shares)	86,958
Weighted average remaining life, options (Year)	9 years 167 days
Stock Options Nine [Member]
Shares, options (in shares)	195,931
Weighted average remaining life, options (Year)	9 years 200 days
Stock Options Ten [Member]
Shares, options (in shares)	21,740
Weighted average remaining life, options (Year)	9 years 215 days
Stock Options Eleven [Member]
Shares, options (in shares)	66,451
Weighted average remaining life, options (Year)	9 years 215 days
Stock Options Twelve [Member]
Shares, options (in shares)	30,000
Weighted average remaining life, options (Year)	9 years 222 days
Stock Options Thirteen [Member]
Shares, options (in shares)	41,668
Weighted average remaining life, options (Year)	9 years 215 days
Stock Options Fourteen [Member]
Shares, options (in shares)	30,000
Weighted average remaining life, options (Year)	9 years 222 days
Stock Options Fifteen [Member]
Shares, options (in shares)	111,112
Weighted average remaining life, options (Year)	9 years 73 days
Stock Options Sixteen [Member]
Shares, options (in shares)	17,200
Weighted average remaining life, options (Year)	8 years 273 days
Stock Options Seventeen [Member]
Shares, options (in shares)	2,305,790
Weighted average remaining life, options (Year)	8 years 175 days
Stock Options Eighteen [Member]
Shares, options (in shares)	14,286
Weighted average remaining life, options (Year)	8 years 91 days
Stock Options Nineteen [Member]
Shares, options (in shares)	293
Weighted average remaining life, options (Year)	7 years 237 days
Stock Options Twenty [Member]
Shares, options (in shares)	20,640
Weighted average remaining life, options (Year)	7 years 233 days
Stock Options Twenty One [Member]
Shares, options (in shares)	57,145
Weighted average remaining life, options (Year)	8 years 3 days
Stock Options Twenty Two [Member]
Shares, options (in shares)	4,000
Weighted average remaining life, options (Year)	7 years 182 days
Stock Options Twenty Three [Member]
Shares, options (in shares)	3,636
Weighted average remaining life, options (Year)	7 years 273 days
Stock Options Twenty Four [Member]
Shares, options (in shares)	7,147
Weighted average remaining life, options (Year)	7 years 262 days
Stock Options Twenty Five [Member]
Shares, options (in shares)	3,529
Weighted average remaining life, options (Year)	7 years 91 days
Stock Options Twenty Six [Member]
Shares, options (in shares)	3,902
Weighted average remaining life, options (Year)	7 years 251 days
Stock Options Twenty Seven [Member]
Shares, options (in shares)	190
Weighted average remaining life, options (Year)	6 years 295 days
Stock Options Twenty Eight [Member]
Shares, options (in shares)	1,157
Weighted average remaining life, options (Year)	7 years 3 days
Stock Options Twenty Nine [Member]
Shares, options (in shares)	2,323
Weighted average remaining life, options (Year)	6 years 182 days
Stock Options Thirty [Member]
Shares, options (in shares)	187
Weighted average remaining life, options (Year)	6 years 273 days
Stock Options Thirty-One [Member]
Shares, options (in shares)	232
Weighted average remaining life, options (Year)	6 years 91 days
Stock Options Thirty-Two [Member]
Shares, options (in shares)	81
Weighted average remaining life, options (Year)	3 years 251 days
Stock Options Thirty-Three [Member]
Shares, options (in shares)	928
Weighted average remaining life, options (Year)	4 years 76 days
Stock Options Thirty-Four [Member]
Shares, options (in shares)	1,760
Weighted average remaining life, options (Year)	3 years 229 days
Stock Options Thirty-Five [Member]
Shares, options (in shares)	123
Weighted average remaining life, options (Year)	6 years 3 days
Stock Options Thirty-Six [Member]
Shares, options (in shares)	121
Weighted average remaining life, options (Year)	5 years 273 days
Stock Options Thirty-Seven [Member]
Shares, options (in shares)	121
Weighted average remaining life, options (Year)	4 years 197 days
Stock Options Thirty-Eight [Member]
Shares, options (in shares)	130
Weighted average remaining life, options (Year)	4 years 197 days
Stock Options Thirty-Nine [Member]
Shares, options (in shares)	529
Weighted average remaining life, options (Year)	4 years 14 days
Stock Options Forty [Member]
Shares, options (in shares)	3
Weighted average remaining life, options (Year)	4 years 127 days
Stock Options Forty-One [Member]
Shares, options (in shares)	72
Weighted average remaining life, options (Year)	5 years 91 days
Stock Options Forty-Two [Member]
Shares, options (in shares)	306
Weighted average remaining life, options (Year)	5 years 69 days
Stock Options Forty-Three [Member]
Shares, options (in shares)	188
Weighted average remaining life, options (Year)	5 years
Stock Options Forty-Four [Member]
Shares, options (in shares)	42
Weighted average remaining life, options (Year)	4 years 273 days
Stock Options Forty-Five [Member]
Shares, options (in shares)	3,669,277
Weighted average remaining life, options (Year)