All of the following signs a can be seen in coicospinal tract injury except:

Ans. d. Clasp-knife spasticityWhen the muscles are hypeonic, as in a UMN lesion, the sequence of moderate stretch --n muscle contraction, strong stretch --n muscle relaxation is seen.Passive flexion of the elbow meets immediate resistance as a result of the stretch reflex in the triceps muscle.Fuher stretch activates the inverse stretch reflex. The resistance to flexion suddenly collapses, and the arm flexes.Continued passive flexion stretches the muscle again, and the sequence is repeated.This sequence of resistance followed by a 'give' when a limb is moved passively is known as the clasp-knife effect because of its resemblance to the closing of a pocket knife.It is also known as lengthening reaction because it is the response of a spastic muscle to lengthening Upper Motor Neuron LesionsLower Neuron LesionsPowerDecreaseddegWeakness (Muscle groups or Limbs being af-fected and not individual musclesQ) Very much decreasedWeakness (severe) due to paralysis of individual musclesQ Tone Hypeonia (Clasp knife spasticityQ) Flaccidity (Hypotoniadeg) Wasting/Atrophy Minimaldeg, if present and due to disuse atrophy Marked (cardinal feature') Reflexes Superficial reflexes LostQ Lost!Q Deep reflexes Brisk/ExaggeratedQ ExaggeratedQ Clonus May be + ntQ AbsentQ Plantar ExtensorQ Flexor or no responseQ Fasciculations AbsentQ PresentQ Reaction of degenera tion in muscles AbsentQ PresentQ