CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Apr. 30, 2016	$ 238	$ 9	$ (1,252)	$ 63,947	$ (62,466)
Balance (in shares) at Apr. 30, 2016		8,704,846	269,685
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and modification expense	2,662			2,662
Issuance of common stock for services	44			44
Issuance of common stock (in shares)		18,564
Issuance of common stock on exercise of stock options	4,340	$ 2		4,338
Sale of common stock, net of issuance costs of $742 (in shares)		2,258,749
Net loss	(6,884)				(6,884)
Balance at Apr. 30, 2017	400	$ 11	$ (1,252)	70,991	(69,350)
Balance (in shares) at Apr. 30, 2017		10,982,159	269,685
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and modification expense	1,004			1,004
Issuance of common stock for services	37			37
Issuance of common stock (in shares)		8,569
Issuance of common stock on exercise of stock options	38	$ 0	$ 0	38	0
Sale of common stock, net of issuance costs of $742 (in shares)		12,500	0
Net loss	(1,476)				(1,476)
Balance at Apr. 30, 2018	$ 3	$ 11	$ (1,252)	$ 72,070	$ (70,826)
Balance (in shares) at Apr. 30, 2018		11,003,228	269,685