I had to look up this disorder, and found this symptom list: Symptoms of FHS:

Dilated pupils
Twitching of the tail
Appearing to be annoyed with the tail
Biting at the tip of the tail, sometimes to the point of mutilation
Behavior may change from loving, to scared and depressed
Sensitive to touch around the tail
Staring into space
Persistent, loud meowing
Dashing off madly and aimlessly around the house or yard
Rippling skin on the back just above the tail

More info: http://www.purelypets.com/articles/f...eresthesia.htm