Tests
1st tests to order
clinical diagnosis
Test
Investigations are not usually necessary for diagnosis. After ruling out pseudoparalysis from another cause, confirm the diagnosis with history and physical exam, focusing on the neurologic exam.
Result
features include decreased movement of affected arm and abnormal posture ("waiter tip" position)
Tests to consider
ultrasound scan of the shoulder
Test
May be helpful when neonatal shoulder dislocation (rare), diaphragmatic paralysis, or glenohumeral joint subluxation is suspected.[52][61][62][63]
Advantages include that there is no need for sedation and it is relatively inexpensive. Disadvantages include that it is operator dependent and cannot fully evaluate glenoid morphology.
Result
neonates: may detect dislocation (rare) or diaphragmatic paralysis; older infants: may detect shoulder subluxation
MRI/MRI myelogram
Test
Best study to identify shoulder joint morphology as much of the infant's glenohumeral joint is cartilaginous at this age.
May be performed if there is evidence of shoulder subluxation, or for surgical planning.
The Waters classification system may be used to assess severity of glenoid deformity.[64][65] Humeral head deformity and humeral retroversion can also be assessed.[66][67]
MRI myelography of the cervical spine cannot accurately diagnose an injury but can identify pseudomeningoceles or rootlet avulsions associated with some nerve root avulsions.[69][70][71] Imaging had a 70% sensitivity and 66% specificity for identification of nerve avulsions in one study.[59]
MRI and CT myelogram have comparable sensitivity and specificity. MRI may be preferred in younger children because it is noninvasive and does not require exposure to ionizing radiation or iodinated contrast.[22] Both require the patient to be sedated.
Result
visualization of shoulder morphology; may demonstrate shoulder dislocation (rare) or subluxation; presence of pseudomeningoceles indicates avulsion injury of the affected spinal roots
CT/CT myelogram
Test
May be performed if there is evidence of shoulder subluxation in a skeletally mature child, or for surgical planning.
Allows accurate evaluation of shoulder congruity and glenoid morphology in older children who have ossified glenohumeral joints.[68]
CT myelography of the cervical spine cannot accurately diagnose an injury but can identify pseudomeningoceles or rootlet avulsions associated with some nerve root avulsions.[69][70][71] Imaging had a 70% sensitivity and 66% specificity for identification of nerve avulsions in one study.[59]
MRI and CT myelogram have comparable sensitivity and specificity. MRI may be preferred in younger children because it is noninvasive and does not require exposure to ionizing radiation or iodinated contrast.[22] Both require the patient to be sedated.
Result
visualization of shoulder morphology; may demonstrate shoulder (rare) or subluxation; presence of pseudomeningoceles indicates avulsion injury of the affected spinal roots
EMG/nerve conduction studies
Test
May be helpful to confirm the extent and location of injury and sometimes obtained for surgical planning. Not always diagnostic because it is not possible to test voluntary activity in infants and newborns.[72] However, pediatric reference values are available to aid diagnosis.[60][73][74][75]
In one study, EMG was less sensitive than imaging for detecting nerve root avulsions, but more specific - particularly for the lower nerve roots.[59]
EMG/nerve conduction studies may provide overly optimistic results in infants and fail to reliably predict recovery.
Result
presence of fibrillation potentials indicates denervation; consult published pediatric reference values
Emerging tests
three-dimensional proton-density MRI to assess the brachial plexus
volumetric MRI and EMG assessment of rotator cuff muscles
Test
Has been evaluated in case series comparing the findings to global external rotation of the patient’s arm. Useful for recommending appropriate interventions to improve shoulder function.[78]
Result
findings correlate with clinical external rotation at the shoulder
ultrasound evaluation of the brachial plexus
Test
Has been used to define postganglionic injuries with neuroma formation, as well as to assess the shoulder for laxity in preoperative patients.[81] Findings correlate with MRI, but the lower plexus is difficult to image with ultrasound.[82]
Result
findings correlate with muscular atrophy around the shoulder girdle
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