Wrist drop is seen in damage to which nerve?

ANSWER: (A) Radial nerveREF: Gray's anatomy 39th edition page 858See APPENDIX-7 below for "BRACHIAL PLEXUS LESIONS"Lesions of the radial nerve in the upper arm:Lesions of the radial nerve at its origin from the posterior cord in the axilla may be caused by pressure from a long crutch (crutch palsy). Triceps is only involved when lesions occur at this level and is usually spared in the more common lesions of the radial nerve in the arm as it lies alongside the spiral groove, where the nerve is commonly affected by fractures of the humerus. Compression of the nerve against the humerus occurs if the arm is rested on a sharp edge such as the back of a chair ('Saturday night palsy*). Both these injuries cause weakness of brachioradialis with wasting and loss of the reflex. There is both wrist and finger drop due to weakness of wrist and finger extensors, as well as weakness of extensor pollicis longus and abductor pollicis longus. There may be sensory impairment or paraesthesiae in the distribution of the superficial radial nerve. However, nerve overlap means that only a small area of anaesthesia usually occurs on the dorsum of the hand between the first and second metacarpal bones. APPENDIX - 7Brachial Plexus Lesions-chart 1Nerve (Segment)Motor Deficit(s)Sensory DeficitsLong Thoracic (C 5, 6, 7)Winged Scapula- Serratus AnteriorNoneSuprascapular (C 5, 6 )Hard to start shoulder abduction - SupraspinatusNoneAxillary (C 5, 6 )Difficult abducting arm to horizontal - DeltoidLateral side of arm below point of shoulder Loss of shoulder roundness - DeltoidMusculocutaneous C 5, 6, (7)Very weak flexion of elbow joint- Biceps & BrachialisLateral forearm Weak supination of radioulnar joint -Biceps Radial (C 5 - Tl)Drop Wrist - Extensor carpi radialis iongus & brevis, Ext. carpi ulnarisPosterior lateral &arm; dorsum of hand Difficulty making a fist - synergy between wrist 1 extensors and finger flexors Median (EUR 5 - Tl) at ElbowPronation of radioulnar joints-Pronator teres & quadratusRadial portion of palm; palmar surface 8i tips of radial 3% Weak wrist flexion - FI. carpi radialisdigits Weakened opposition of thumb - thenar muscles "Ape Hand"- thumb hyper extended and adducted - thenar muscles "Papal Hand" Loss of flexion of I.P. joints of thumb & fingers 1 & 2 - Fl. pollices Iongus ; FL digit, superficialis, FL digit profundus Median (C 5 - Tl) at WristWeakened opposition of thumb - thenar musclesPalmar surface & tips of radial "Ape Hand"- thumb hyper extended and adducted - thenar muscles3% digitsUlnar (C 8, Tl) at Elbow"Clawing" of fingers 3 & 4- M.P. joints hyper extended: P.I.P. Flexed - Interossei& LumbricalsUlnar and dorsal aspect of palm and of ulnar VA digits Loss of abduction & adduction of M.P joints of fingers -Interossei Thumb - abducted and extended - adductor pollices Loss of flexion of D.I.P. joints of fingers 4 8t 5 - Fl. digit profund. Ulnar (C 8, Tl) at Wrist"Clawing" of fingers 3 & 4- M.P. joints hyper extended; P.I.P. Flexed - Interossei & LumbricalsUlnar and dorsal aspect of palm and of ulnar 1 xk digitsLoss of abduction & adduction of M.P joints of fingers - InterosseiThumb - abducted and extended - adductor pollicesUpper and Lower Root Lesions-chart 2LesionMotor DeficitsSensory DeficitsNervesErb s Palsy(C5,6)Loss of abduction, flexion and rotation at shoulder; Weak shoulder extension - deltoid, rotator cuffPosterior and lateral aspect of arm - axillary n.Axillary, Suprascapular, Upper and Lower subscapular Very weak elbow flexion and supination of radioulnar joint - biceps brachii & brachiaiisRadial side of Forearm- musculocutaneous n. Thumb and 1st finger - superficial hr. of radial; digital brs. - Median n.Musculocutaneous: Radial N. brs. to supinator & brachioradialis muscles Susceptible to shoulder dislocation - loss of rotator cuff muscles Suprascapular, Upper and Lower subscapular "Waiters Tip" position Klumke's Palsy (C8, Tl)Loss of opposition of thumb -Tnenar musclesUlnar side of forearm, hand & ulnar 1 Vi & digits - ulnar and medial antebrachial cutaneousThenar branch of Median nerve Loss of adduction of thumb - Adductor pollices Ulnar nerve Loss of following finger movements: abduction and adduction of M.P. joints; flexion at M.P. & extension of LP. joints. Lumbricals & interossei Deep branch of Ulnar & Median Very weak flexion of P.I.P. & D.I.P. joints FI Digit. Super. & Profund. Ulnar and Median