Note 9 - Segment Reporting - Summary of Operating Results by Reportable Segments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Net revenues	$ 4,305,000	$ 2,004,000	$ 7,268,000	$ 3,871,000
Cost of revenues	2,354,000	1,641,000	4,057,000	3,156,000
Gross profit	1,951,000	363,000	3,211,000	715,000
Operating expenses	2,213,000	30,868,000	4,378,000	34,477,000
Operating loss	(262,000)	(30,505,000)	(1,167,000)	(33,762,000)
Depreciation and amortization	190,000	174,000	402,000	333,000
Stock-based compensation expense	125,000	163,000	206,000	300,000
Goodwill	781,000	1,281,000	781,000	1,281,000	$ 781,000
Total assets	16,532,000	23,243,000	16,532,000	23,243,000	$ 14,611,000
Impairment charges		27,202,000		27,202,000
Clinical Development [Member]
Net revenues	44,000	46,000	56,000	108,000
Clinical Development [Member] | Operating Segments [Member]
Net revenues	44,000	46,000	55,000	108,000
Cost of revenues	57,000	49,000	100,000	120,000
Gross profit	(13,000)	(3,000)	(45,000)	(12,000)
Operating expenses	483,000	28,408,000	955,000	29,588,000
Operating loss	(496,000)	(28,411,000)	(1,000,000)	(29,600,000)
Depreciation and amortization	75,000	69,000	169,000	137,000
Stock-based compensation expense	59,000	122,000	113,000	220,000
Goodwill		500,000		500,000
Total assets	4,412,000	12,808,000	4,412,000	12,808,000
Impairment charges		27,202,000		27,202,000
Device [Member]
Net revenues	4,261,000	1,958,000	72,120,000	3,763,000
Device [Member] | Operating Segments [Member]
Net revenues	4,261,000	1,958,000	7,213,000	3,763,000
Cost of revenues	2,297,000	1,592,000	3,957,000	3,036,000
Gross profit	1,964,000	366,000	3,256,000	727,000
Operating expenses	1,730,000	2,460,000	3,423,000	4,889,000
Operating loss	234,000	(2,094,000)	(167,000)	(4,162,000)
Depreciation and amortization	115,000	105,000	233,000	196,000
Stock-based compensation expense	66,000	41,000	93,000	80,000
Goodwill	781,000	781,000	781,000	781,000
Total assets	$ 12,120,000	10,435,000	$ 12,120,000	10,435,000
Impairment charges