Pen test is done for elliciting which nerve injury -

Pen test is used to test abductor pollicis brevis * supply by median nerve * action - abduction of the thumb * pen test - the patient is asked to lay his hand flat on the table with palm facing the ceiling .A pen is held above the thumb & the patient is asked to touch the pen with tip of the thumb .It will not possible in case of median nerve injury . REF:Essential ohopedics ,Maheshwari, 5th edition ,pg.no.66