Tinel sign is seen in -

Ans. is 'b' i.e., Nerve regenerationPathological changes after nerve injuryo After nerve injury, nerve first degenerates and then tries to regenerate.Nerve degenerationo The part of the neurone distal to the point of injury undergoes secondary or Wallerian degeneration-, the proximal part undergoes primary or retrograde degeneration upto a single node.Nerve regenerationo As regeneration begins, the axonal stump from the proximal segment begins to growr distally. If the endoneural tube with its contained Schwrann cells is intact, the axonal sprout may readily pass along its primary course and reinnerv ate the end-organ. The rate of recovery of axon is 1 mm per day. The muscles nearest to the site of injury recovers first, followed by others as the nerve reinnervates muscles from proximal to distal, the so-called motor march.o When the skin over the nerve is percussed gently from distal to proximal, the patient gets a tingling sensation if the nerve is recovering. This is called Tinel's sign and is a sign of recovery.