Brachial+Plexus.pdf

Brachial Plexus DPM Program 1. Describe the brachial plexus, including roots, trunks, divisions, cords, and branches. 4.0 2. Describe the functional deficits resulting from the most common brachial plexus injuries. 4.0 3. Diagnose probable lesion sites of the brachial plexus from motor and sensory d...

Brachial Plexus DPM Program 1. Describe the brachial plexus, including roots, trunks, divisions, cords, and branches. 4.0 2. Describe the functional deficits resulting from the most common brachial plexus injuries. 4.0 3. Diagnose probable lesion sites of the brachial plexus from motor and sensory deficits. 4.0 4. Describe the anatomical basis for wrist drop. 3.0 1 Axillary Inlet and Outlet Walls The axillary inlet and outlet and walls of the axilla can be established using skin folds and palpable bony landmarks: 1.The anterior margin of the axillary inlet is the clavicle, which can be palpated along its entire length. The lateral limit of the axillary inlet is approximated by the tip of the coracoid process, which is palpable immediately below the lateral third of the clavicle and deep to the medial margin of the deltoid muscle. 2.The inferior margin of the anterior axillary wall is the anterior axillary skin fold, which overlies the lower margin of the pectoralis major muscle. 3.The inferior margin of the posterior axillary wall is the posterior axillary skin fold, which overlies the margins of the teres major muscle laterally and latissimus dorsi muscle medially. 4.The medial wall of the axilla is the upper part of the serratus anterior muscle overlying the thoracic wall. The long thoracic nerve passes vertically out of the axilla and down the lateral surface of the serratus anterior muscle in a position just anterior to the posterior axillary skin fold. 5.The lateral boundary of the axilla is the humerus. 6.The floor of the axilla is the dome of skin between the posterior and anterior axillary skin folds. 2 3 Brachial Plexus The brachial plexus is a network of nerves supplying the upper limb. It begins in the neck and continues into the axilla by passing through the cervicoaxillary canal). -The brachial plexus has five roots formed from the VENTRAL RAMI of C5 - T1 The five roots unite to form three trunks -Superior trunk - union of C5 and C6 -Middle trunk - continuation of C7 -Inferior trunk - union of C8 and T1 - As the trunks pass through the cervicoaxillary canal they each separate into ventral and dorsal divisions - The dorsal divisions unite, posterior to the axillary artery, to form the posterior cord. Branches of the posterior cord are responsible for innervating all muscles on the posterior and lateral sides of the upper limb. The terminal branches of the posterior cord are the axillary nerve and radial nerve. - The ventral divisions recombine to form the lateral cord (C5 - C7) and medial cord (C8- T1) (named for their relationship to the 2nd part of the axillary artery). The three major ventral division nerves of the brachial plexus are the median nerve, the ulnar nerve and the musculocutaneous nerve. 4 5 6 The Brachial Plexus & Axillary Artery InSitu 7 8 Brachial Plexus Injuries Injuries to the plexus and its branches may occur at any number of sites. The resulting symptoms and signs will give you an idea as to where the injury has actually occurred. Remember that sensory loss and muscle weakness will only occur at sites distal to the site of injury. UPPER PLEXUS INJURY (Upper Trunk Palsy, Erb’s Palsy, or Erb-Duchenne Palsy) -caused by sudden forced separation of the head from the shoulder resulting in tearing of the upper trunk proximal to the suprascapular nerve. -Individual would lose C5 or C6. This leads to a loss of the: -Suprascapular and Axillary nerves. The following muscles would be affected: Infraspinatus and Teres minor (both lateral rotators of the arm) Supraspinatus and Deltoid (both are abductors of the arm) -C5 and C6 also contribute to the flexors of the arm and forearm and supinators (would be weakened) RESULT: -arm rotated medially and pronated forearm -Leaving the hand assuming a characteristic “Waiter’s tip” -There will also be sensory loss over the lateral side of the upper limb 9 10 Brachial Plexus Injuries Continued LOWER PLEXUS INJURY (Lower Trunk Palsy, Klumpke’s Paralysis, or Klumpke-Déjérine Paralysis) -Occurs less frequently than upper plexus injuries. Caused by an upward traction on the shoulder as might occur when someone falls from a high place and grabs a structure to break the fall -Damage would be to the whole lower trunk or the 1st thoracic nerve -Similar to an ulnar nerve injury which paralyzes most of the intrinsic muscles of the hand except those of the thenar eminence and the 1st two lumbricals RESULT: -hand assumes a characteristic posture referred to as “Claw Hand” -there will also be sensory loss over the medial side of the upper limb POSTERIOR CORD INJURY -can result from improper use, or incorrectly fitted crutches (sometimes referred to as “crutch palsy”) -can also be result of inferior dislocation of the head of the humerus -result in damage to the posterior cord, but usually just the radial nerve is involved RESULT: -clinical manifestation is “wrist drop” which results from the loss of the extensors of the wrist -May also result from falling asleep (or passing out from the imbibition of too much ethanol) with one‘s arm draped over the back of a chair such that weight is applied to the axillary region. Thus, the latter may be referred to as “Saturday night palsy 11 12