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Muscle innervated by the ulnar nerve; 3 months
4%
89/2092
Muscle innervated by the anterior interosseous nerve; 4 months
3%
56/2092
Muscle innervated by the musculocutaneous nerve; 1 year
8%
159/2092
Muscle innervated by the axillary nerve; 1 year
5%
109/2092
Muscle innervated by the musculocutaneous nerve; 3 months
79%
1662/2092
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The most common brachial plexopathy involves the C5-6 nerve roots (Erb's Palsy), and recovery of antigravitational elbow flexion indicating biceps (musculocutaneous n.) by 3-6 months indicates a good prognosis for a full recovery. Erb's Palsy is a common injury due to birth-related trauma. The mechanism is traction on the upper brachial plexus at levels C5-C6, causing disruption of the post-ganglionic plexus fibers. These patients present with paralysis of the shoulder abductors and external rotators, and elbow flexors. Involvement of the wrist extensors suggests an extended Erb's palsy with C7 involvement. The common position of the extremity is in an adducted, internally rotated, elbow extended and forearm pronated position. Risk factors for brachial plexus injury include macrosomia, multiparous pregnancies, previous pregnancies with plexus injuries, and breech or difficult deliveries. Recovery is inversely correlated with concomitant neural injuries like Klumpke's palsy (C8-T1) and preganglionic nerve involvement. Initial treatment of Erb's palsy is to observe for return of biceps flexion for at least 3 months. If active biceps flexion returns within this time frame, full neurologic recovery is expected. If active biceps flexion fails to return then further intervention is warranted. Reconstruction of extraforaminal (post-ganglionic) ruptures is performed between 3 and 9 months of age, depending on the center. El-Sayed performed a retrospective review of 829 infants with brachial plexopathies. Of these, Erb's palsy was most commonly diagnosed at 42.8% of the cases while an extended Erb's (involving C7) was diagnosed in 28.8% of the cases. In their case series, they defined an intermediate palsy where C7 was the most dominantly affected nerve level of which all showed excellent recovery at 6-12 months. Waters detailed the management and treatment options for obstetric brachial plexus palsies. Their approach is to observe these individuals, using biceps function as an indicator of recovery, as 90% of classic Erb's palsy will resolve. If there is a delayed recovery, investigation with advanced imaging and EMG is appropriate. For those with persistent palsies past 3-6 months or those with evidence of nerve root avulsions, they recommended microsurgical reconstruction. Illustration A depicts the classic position of the arm in an extended Erb's palsy (involving C7) as the wrist is held in a flexed posture. Incorrect answers: Answer 1: The ulnar nerve (C8-T1) is affected in pan-plexus injuries or isolated lower plexus injuries, which are less common Answer 2: The anterior interosseous nerve (C5-T1) innervates FPL, PQ and the radial FDP muscles, which have not been shown to be prognostic for recovery in Erb's Palsy Answer 3: The timeframe of 3-6 months is the typical observation period in postganglionic injuries for spontaneous recovery of elbow flexion before microsurgical intervention is warranted Answer 4: The axillary nerve (C5-6) innervates the deltoid and teres minor. These muscles are affected in Erb's Palsy, but spontaneous recovery at 1 year has not been shown to have as strong of prognostic value as elbow flexion at 3-6 months.
2.6
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