Here is a website that explains it very well:
http://vetsurgerycentral.com/pss.htm
Clinical signs
* Abnormal behavior after eating
* Pacing and aimless wandering
* Pressing the head against the wall
* Episodes of apparent blindness
* Seizures
* Poor weight gain
* Stunted growth
* Excessive sleeping and lethargy
* Straining to urinate due to bladder stone formation
* Patient with a shunt may have many clinical signs and some have only a single clinical sign
* Some dogs do not show signs until they are older
I am glad your baby got a clean bill of health.