Reflexes and Its Assessment (Deep and Superficial Reflexes)

 INTRODUCTION:- Reflexes are the involuntary and instantaneous movement in response of a stimulus. It is an automatic response to a stimulus that does not need conscious thought on an impulse as it occurs through a reflex arc. 

REFLEX ARC:- It contains only two neurons, a sensory and a motor neuron. Sensory neuron receive the stimulus from the receptor and transport it to spinal cord. From here, information is carried to the muscle by efferent or motor neuron to get the response.

TYPES OF REFLEXES:- 

SUPERFICIAL REFLEXES:- Planter reflex, Abdominal reflexes, Cremasteric reflex, Corneal reflex

DEEP REFLEXES:- Jaw jerk, Biceps jerk, Brachioradialis jerk, Triceps jerk, Knee jerk, Ankle jerk

REFLEX TESTING:- 

SUPERFICIAL REFLEXES-

    👉 Abdominal reflex:- Technique- Abdominal wall is lightly stroke from without inwards stimulating each of the quadrants of abdomen.                                                                              Response- The muscle in quadrant stimulated and the umbilicus moves in that direction. 

 👉 Planter reflex:- Technique- The patient is positioned such that the knee is fixed and thigh is slightly externally rotated. Examiner fixes the ankle joint by rotating it and then outer aspect of sole is shocked with a blunt point (key). The stroke is directed forwards and then it curves inwards along the MTP joints from the little to big toe.                                                                                            Response- Normally the great toe will flex at the MTP joint accompanied by flexion of other toes.

👉 Corneal reflex:- Technique- The corneal edge is touched by the whisk of cotton with the patient looking in opposite direction.

Response- Brisk closure of the eye

DEEP REFLEXES-

👉 Jaw jerk:- Technique  The patient is asked to keep his mouth partly open with his mandible hanging loosely. Finger is placed over the chin and tap the hammer on the finger.

Response- slight of elevation of the mandible.

👉 Biceps jerk:- Technique- The upper limb is partially flexes at the elbow. Press the forefinger gently on the biceps tendon in the cubital fossa and then strike the finger with knee hammer.

Response- Flexion of elbow and visible contraction of biceps tendon.

👉 Supination jerk:- Technique- The upper limb is partially flexed at elbow in mid-prone position. Strike the lower end of radius about 5cm above the wrist,

Response- Contraction of brachioradialis and flexion of elbow.

👉 Knee jerk:- The knees are partially flexed and rested on the examiners forearm. The quadricep tendon is the striked with a  knee hammer.

👉 Ankle jerk:- Technique- The patients leg is extremely rotated and flexed at the knee. The patients forefoot is gently dorsiflexed. The Achilles tendon is striked with a knee hammer.

Response- Planter flexion of foot and visible contraction of gastroecnemius muscles.