Note 12 - Stockholders' Equity - Price Ranges of Outstanding and Exercisable Options (Details)	12 Months Ended
	Sep. 30, 2020 $ / shares shares
Outstanding Options Number of Options (in shares) | shares	613,201
Outstanding Options Weighted Average Remaining Contractual Life (Year)	9 years 36 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 4.76
Exercisable Options Number of Options Exercisable (in shares) | shares	5,865
Exercisable Options Weighted Average Exercise Price (in dollars per share)	$ 310.63
Exercise Price Range 1 [Member]
Outstanding Options, Exercise Price Lower Range (in dollars per share)	1.40
Outstanding Options Exercise Price Upper Range (in dollars per share)	$ 1.61	[1]
Outstanding Options Number of Options (in shares) | shares	606,533
Outstanding Options Weighted Average Remaining Contractual Life (Year)	8 years 350 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 1.82
Exercisable Options Number of Options Exercisable (in shares) | shares
Exercisable Options Weighted Average Exercise Price (in dollars per share)
Exercise Price Range 2 [Member]
Outstanding Options, Exercise Price Lower Range (in dollars per share)	115
Outstanding Options Exercise Price Upper Range (in dollars per share)	$ 600
Outstanding Options Number of Options (in shares) | shares	6,017
Outstanding Options Weighted Average Remaining Contractual Life (Year)	2 years 167 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 90.29
Exercisable Options Number of Options Exercisable (in shares) | shares	5,214
Exercisable Options Weighted Average Exercise Price (in dollars per share)	$ 66.97
Exercise Price Range 3 [Member]
Outstanding Options, Exercise Price Lower Range (in dollars per share)	601
Outstanding Options Exercise Price Upper Range (in dollars per share)	$ 900
Outstanding Options Number of Options (in shares) | shares	283
Outstanding Options Weighted Average Remaining Contractual Life (Year)	3 years 87 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 707.14
Exercisable Options Number of Options Exercisable (in shares) | shares	283
Exercisable Options Weighted Average Exercise Price (in dollars per share)	$ 192.92
Exercise Price Range 4 [Member]
Outstanding Options, Exercise Price Lower Range (in dollars per share)	901
Outstanding Options Exercise Price Upper Range (in dollars per share)	$ 1,400
Outstanding Options Number of Options (in shares) | shares	80
Outstanding Options Weighted Average Remaining Contractual Life (Year)	2 years 142 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 1,356.25
Exercisable Options Number of Options Exercisable (in shares) | shares	80
Exercisable Options Weighted Average Exercise Price (in dollars per share)	$ 203.44
Exercise Price Range 5 [Member]
Outstanding Options, Exercise Price Lower Range (in dollars per share)	1,401
Outstanding Options Exercise Price Upper Range (in dollars per share)	$ 1,975
Outstanding Options Number of Options (in shares) | shares	288
Outstanding Options Weighted Average Remaining Contractual Life (Year)	2 years 40 days
Outstanding Options Weighted Average Exercise Price (in dollars per share)	$ 1,648.71
Exercisable Options Number of Options Exercisable (in shares) | shares	288
Exercisable Options Weighted Average Exercise Price (in dollars per share)	$ 398.44

[1] There are no outstanding or exercisable options with exercise prices between $1.62 and $115.