Note 8 - Segment Reporting - Summary of Operating Results by Reportable Segments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017
Net revenues	$ 2,004,000	$ 3,501,000	$ 3,871,000	$ 6,753,000
Cost of revenues	1,641,000	1,973,000	3,156,000	3,848,000
Gross profit	363,000	1,528,000	715,000	2,905,000
Operating expenses	30,868,000	3,260,000	34,477,000	6,800,000
Operating loss	(30,505,000)	(1,732,000)	(33,762,000)	(3,895,000)
Depreciation and amortization	174,000	172,000	333,000	357,000
Impairment of intangible asset	27,202,000	310,000	27,202,000	310,000
Stock-based compensation expense	163,000	181,000	300,000	428,000
Operating loss	(30,505,000)	(1,732,000)	(33,762,000)	(3,895,000)
Goodwill	1,281,000		1,281,000		$ 13,976,000	$ 13,976,000
Total assets	23,243,000		23,243,000			$ 51,111,000
Clinical Development [Member]
Net revenues	46,000		108,000
Clinical Development [Member] | Operating Segments [Member]
Net revenues	46,000	113,000	108,000	266,000
Cost of revenues	49,000	111,000	120,000	235,000
Gross profit	(3,000)	2,000	(12,000)	31,000
Operating expenses	28,408,000	1,899,000	29,588,000	3,880,000
Operating loss	(28,411,000)	(1,897,000)	(29,600,000)	(3,849,000)
Depreciation and amortization	69,000	110,000	137,000	226,000
Impairment of intangible asset	27,202,000		27,202,000
Stock-based compensation expense	122,000	100,000	220,000	251,000
Operating loss	(28,411,000)	(1,897,000)	(29,600,000)	(3,849,000)
Goodwill	500,000		500,000
Total assets	12,808,000		12,808,000
Device [Member]
Net revenues	1,958,000		3,763,000
Device [Member] | Operating Segments [Member]
Net revenues	1,958,000	3,388,000	3,763,000	6,487,000
Cost of revenues	1,592,000	1,862,000	3,036,000	3,613,000
Gross profit	366,000	1,526,000	727,000	2,874,000
Operating expenses	2,460,000	1,361,000	4,889,000	2,920,000
Operating loss	(2,094,000)	165,000	(4,162,000)	(46,000)
Depreciation and amortization	105,000	62,000	196,000	131,000
Impairment of intangible asset
Stock-based compensation expense	41,000	81,000	80,000	177,000
Operating loss	(2,094,000)	$ 165,000	(4,162,000)	$ (46,000)
Goodwill	781,000		781,000
Total assets	$ 10,435,000		$ 10,435,000