**7. Investigations**

#### **7.1. Neurophysiologic investigations**

#### *7.1.1. Electromyography*

The role of electromyography (EMG) in BPBP is doubtful as it frequently gives optimistic results in a severe nonresolving clinical picture. One explanation for this is the reflex-activated contraction of muscles in young children. Another explanation for this discrepancy is 'Luxury Innervation' of muscles. Until the age of 3 months, children may have polyneuronal innervation, which may give positive EMG findings in the absence of adequate nerve regeneration [7, 8, 20, 21].

#### *7.1.2. Nerve action potentials*

Although the isolated use of EMG has limitations in BPBP, according to few investigators, combining it with nerve action potentials (NAPs) may help in determining the nature and level of lesion. In selected cases, the authors have reported their ability to even differentiate axonotmesis from neurotmesis [9, 10, 14, 22].

#### **7.2. Radiologic imaging**

#### *7.2.1. X-ray*

Imaging of shoulder and upper limb can be used to diagnose the birth trauma. Chest X-ray can also give evidence of hemi diaphragm paralysis associated with C4 or phrenic nerve palsy. The diaphragm routinely lies relatively higher by two ribs level on the right side owing to liver, but in hemidiaphragm paralysis, it lies at the level of the fifth or the sixth rib.

#### *7.2.2. Ultrasonography*

Dynamic ultrasonography (USG) can help in the diagnosis of hemi diaphragm paralysis. Vathana et al. found good interobserver and intraobserver reliability in diagnosing glenohumeral deformity by ultrasound [11, 23]. Donohue et al. found measurements of glenohumeral deformity by USG reliable, but there was poor agreement between USG and magnetic resonance imaging (MRI) for diagnosing it. They questioned the use of USG as a standalone investigation for this purpose [12, 24].

#### *7.2.3. Computed tomography scan and magnetic resonance imaging*

Computed **t**omography (CT) myelography was considered better modality than MRI to diagnose root avulsions before a decade. Root avulsions were diagnosed based on contrast-filled meningoceles and by following the course of anterior and posterior roots from spinal cord to the respective exit foramen. But it has the disadvantage of radiation, the need of intrathecal contrast injection and the inability to reliably diagnose extra-foraminal injuries. These issues have made MRI the modality of choice for imaging brachial plexus [13, 25].

Different MRI sequences can give excellent imaging of intra-spinal as well as extra-spinal imaging of plexus. MRI can also give a clue about nerve edema, scarring and neuroma formation [14, 26].

Waters et al. reported an MRI axial image-based classification of glenohumeral deformity. It reliably measured the amount of glenoid retroversion and the percentage of humeral head anterior to mid-scapular line [15, 27]. Correlation was found between clinical parameters and MRI findings [16, 28]. The decision about surgical intervention is made on the defined congruency of glenohumeral joint on axial MRI imaging recently.

Van der Sluijis et al. found humeral head retroversion in children with BPBP after performing simultaneous axial imaging of shoulder and distal humerus [16, 28]. However, Pearl et al. recently reported that the retroversion of humeral head on the affected side is usually less compared to the normal side and discussed its merits in surgical planning [17, 29].
