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Year 2004 Paper one: Questions supplied by Megan QUESTION 47 A 58yo man is noted to have a right foot drop three days following a right total hip replacement. On examination there is weakness of right ankle dorsiflexion and toe extension (grade 4/5). Other muscle groups are normal. The knee jerks are symmetrical with an absent right ankle jerk. Sensation is reduced on the sole and dorsum of the right foot. The most likely diagnosis is: A. B. C. D. E. Femoral neuropathy Sciatic neuropathy L5 radiculopathy Tibial neuropathy Peroneal neuropathy CAUSES OF FOOT DROP - Common peroneal nerve palsy Sciatic nerve palsy L4,L5 root lesion Peripheral motor neuropathy Distal myopathy Motor neuron disease Stroke NERVES OF THE LOWER LIMB Year 2004 Paper one: Questions supplied by Megan Femoral Nerve: - Largest branch of the lumbar plexus L2, L3, L4 Forms in the abdomen and runs through the pelvis and under the inguinal ligament Runs lateral to the femoral vessels in the femoral triangle and outside the femoral sheath Breaks up into several terminal branches Supplies the anterior femoral muscles Sends articular branches to the hip and knee joints Gives several branches to the skin on the anteromedial side of the lower limb Saphenous nerve (L2, L3, L4) is a cutaneous branch of femoral nerve It descends through femoral triangle lateral to the femoral sheath Then accompanies the femoral artery in the adductor canal and passes anteriorly to supply the skin and fascia of the anterior and medial aspects of the knee, leg and foot Knee reflex (L2, L3, L4) Sciatic Nerve: - L4, L5, S1, S2, S3 Largest nerve in the body Leaves the pelvis through the greater sciatic foramen Runs deep to gluteus maximus but usually supplies no structures in gluteal region Year 2004 Paper one: Questions supplied by Megan - Supplies all the hamstring muscles (mainly via tibial division but short head of biceps via common peroneal division) Tibial and common peroneal nerves usually separate in inferior part of thigh Tibial nerve (L4, L5, S1, S2, S3) runs behind the knee in the popliteal fossa Gives branches to the knee Supplies gastrocnemius, plantaris, popliteus and soleus muscles (posterior compartment muscles) Divides into medial and lateral plantar nerves which supply the skin on the sole of the foot Uncommonly injured but can occur with lacerations or posterior dislocations of the knee Results in loss of plantarflexion and flexion of toes and loss of sensation over sole of foot In the foot, all intrinsic muscles are supplied by branches of the tibial nerve except for flexor extensor digitorum brevis which is supplies by the deep peroneal nerve Ankle reflex S1, S2 Tibial nerve gives the medial sural cutaneous nerve which usually joins the communicating branch of the peroneal nerve to form the sural nerve Sural nerve (S1, S2) supplies the lateral aspect of the ankle and foot Common peroneal nerve (L4, L5, S1, S2) runs down the medial border of the popliteal fossa Gives branches to the knee Gives off lateral sural cutaneous nerve which supplies the skin on the lateral aspect of the leg (L5, S1, S2) Also gives off the peroneal communicating branch which joins the medial sural cutaneous nerve to form the sural nerve Winds around the neck of fibula and runs down behind the peroneus longus muscle Divides into superficial and deep branches Deep peroneal nerve supplies the muscles of the anterior crural compartment, the ankle joint nd and the skin between the big and 2 toes (L4, L5) The anterior compartment muscles are mainly involved in dorsiflexion of the foot and extension of the toes Superficial peroneal nerve (L5, S1, S2) supplies the lateral crural compartment muscles These muscles (peroneal muscles) plantarflex and evert the foot Superficial peroneal nerve also supplies an area of skin over the anterior aspect of the ankle, the dorsum of the foot and most of the toes A. Injury to the femoral nerve would result in weakness of knee extension and reduced knee jerk. Would also lead to loss of sensation over anteromedial aspect of thigh and leg. B. Sciatic neuropathy would results in weakness of knee flexion and all movements of the ankle/foot. Also there would be loss of sensation of the posterior, lateral and medial areas of the leg and all of the foot (ie. all areas below the knee except for that supplied by the saphenous nerve). Note sciatic nerve is most likely to be injured with hip surgery. C. L5 radiculopathy would result in loss of sensation over the dorsum of the foot and the anterolateral portion of the leg. There may be some weakness of all the movements of the ankle as L5 is involved in the supply to all 3 compartments and also to the feet. D. Tibial neuropathy would lead to weakness of plantarflexion as it supplies the muscles of the posterior crural compartment. Also loss of flexion of the toes and loss of sensation over the sole of the foot. E. Peroneal neuropathy results in weakness of dorsiflexion and extension of the toes. Loss of sensation of the skin over dorsum of foot and toes and anterior aspect of lower leg. May also be weakness of eversion due to involvement of superficial peroneal nerve. This man has weakness of dorsiflexion and toe extension (deep peroneal nerve) but also has reduced sensation on the sole (tibial nerve) and dorsum (peroneal nerve) of the foot. Absent ankle jerk indicates Year 2004 Paper one: Questions supplied by Megan the tibial nerve or S1, S2. Only the sciatic nerve is involved in all these processes so there must be a partial lesion of this nerve. Answer: B Table 363–1. Common Mononeuropathies (from Harrisons) Nerve Origina UPPER EXTREMITY Suprascapular C5, C6 Muscles Innervated Usual Site of Lesion Clinical Features Comments Supraspinatus Weakness of lateral rotation of the humerus Winging of scapula Weakness of shoulder abduction; atrophy of shoulder Wrist drop most obvious, also finger and thumb extensors paralyzed Finger drop; wrist relatively spared No sensory deficit Infraspinatus Serratus anterior Suprascapular notch of scapula Variable Weakness of finger adduction and abduction and thumb adduction (see text); interosseous atrophy, clawhand Same as above May be acute or insidious; sensory symptoms/signs are distinctive (Figs. 22-2 and 22-3); see also text Long thoracic C5–C7 Axillary C5, C6 Deltoid, teres minor Near shoulder joint Radial C5–T1 Triceps, brachioradialis, wrist, finger, and thumb extensors Spiral groove of humerus Posterior interosseous branch C7, C8 Finger and thumb extensors Ulnar C8, T1 Ulnar flexor of the wrist, long flexors of 4th and 5th digits, and most intrinsic hand muscles Edge of supinator muscle below elbow Ulnar groove at the elbow Cubital tunnel Medial base of palm Median C6–T1 Abductor pollicis brevis; more proximal muscles include forearm pronator, long finger and thumb flexors Carpal tunnel Anterior interosseous C7–T1 Long flexors of thumb and index Anterior interosseus Intrinsic hand muscles only, interosseous atrophy Characteristic sensory symptoms and deficit and inability to make a circle with thumb and index finger Weakness of pinch; pain in No sensory deficit Sensory deficit similar to C5 dorsal root lesion (See Figs. 22-2 and 22-3) Saturday night palsy (acute compression) is frequent cause No sensory deficit Often pain over medial proximal forearm (cubital tunnel) No sensory deficit Sensory deficit as per Figs. 22-2 and 22-3 (see text); known as carpal tunnel syndrome No sensory deficit Year 2004 Paper one: Questions supplied by Megan branch LOWER EXTREMITY L2–L4 Femoral and middle fingers branch below the elbow volar forearm Proximal to inguinal ligament Knee buckling; absent knee jerk; weak anterior thigh muscles with atrophy Dysesthetic hyperpathia of lateral thigh Association with diabetes mellitus; sensory disturbance as per Fig. 22-2 Known as meralgia paresthetica Intrapelvic or at pubis Near sciatic notch Weakness of hip adduction Severe lower leg and hamstring weakness; flail foot; severe disability Pain and numbness of sole, weak toe flexors Sensory deficit on medial thigh Uncommon except from war wounds; sometimes after a misdirected injection Known as tarsal tunnel syndrome (see text) Foot drop and weakness of foot eversion Sensory deficit is similar in distribution to L5, S1 sensory roots Lateral femoral cutaneous branch Obturator L2, L3 Iliopsoas (hip flexor) and quadriceps femoris (knee extensor) None L3, L4 Thigh adductors Sciatic L4–S3 Posterior tibial L5–S2 Peroneal L4–S1 Hamstring muscles, hip abductor, and all muscles below the knee Calf muscles (proximally), toe flexors, and other intrinsic foot muscles Dorsiflexors of toes and foot, evertors of foot a Spinal segments. Inguinal ligament Tarsal tunnel, near medial malleolus At neck of fibula