Dorsal scapular and long thoracic nerves during ultrasound-guided interscalene brachial plexus block

A standardized ultrasound approach in neuralgic amyotrophy

Neuralgic amyotrophy (NA), also referred to as idiopathic brachial plexitis and Parsonage-Turner syndrome, is a peripheral nerve disorder characterized by acute severe shoulder pain followed by progressive upper limb weakness and muscle atrophy. While NA is incompletely understood and often difficult to diagnose, early recognition may prevent unnecessary tests and interventions and, in some situations, allow for prompt treatment, which can potentially minimize adverse long-term sequalae. High-resolution ultrasound (HRUS) has become a valuable tool in the diagnosis and evaluation of NA. Pathologic HRUS findings can be grouped into four categories: nerve swelling, swelling with incomplete constriction, swelling with complete constriction, and fascicular entwinement, which may represent a continuum of pathologic processes. Certain ultrasound findings may help predict the likelihood of spontaneous recovery with conservative management versus the need for surgical intervention. We recommend relying heavily on history and physical examination to determine which nerves are clinically affected and should therefore be assessed by HRUS. The nerves most frequently affected by NA are the suprascapular, long thoracic, median and anterior interosseous nerve (AIN) branch, radial and posterior interosseous nerve (PIN) branch, axillary, spinal accessory, and musculocutaneous. When distal upper limb nerves are affected (AIN, PIN, superficial radial nerve), the lesion is almost always located in their respective fascicles within the parent nerve, proximal to its branching point. The purpose of this review is to describe a reproducible, standardized, ultrasonographic approach for evaluating suspected NA, and to share reliable techniques and clinical considerations when imaging commonly affected nerves.

Risk assessment of dorsal scapular nerve injury in the medial scapular area associated with upper extremity position: An ultrasonographic study

INTRODUCTION/AIMS

Injuries to the dorsal scapular nerve (DSN) in the interscapular region are relatively uncommon. Physicians may therefore underestimate the risk of damage to the DSN during procedures. The aim of this study was to identify the topographic position of the DSN in the interscapular region and to identify injection positions for the upper extremities that minimize the risk of damage to the DSN during procedures.

METHODS

The positional relationships between the DSN and scapula were quantified by ultrasonography in 46 healthy volunteers. The distances between the medial scapular line and DSN and the DSN depths from the surface in Zones 1 (the superior angle), 2 (the scapular spine), and 3 (between the scapular spine and inferior angle) were measured in the anatomical and contralateral shoulder touch positions (positions 1 and 2, respectively).

RESULTS

The DSN was located further away from the medial border of the scapula and closer to the skin in position 2 than in position 1. The horizontal distance of the DSN in Zone 2 differed significantly between the two positions (0.85 ± 0.38 vs 1.23 ± 0.38, P < .001). The results suggest a safe area as just medial to the medial scapular border in Zone 2 in position 2. The safety margin should be considered at least 1.5 cm medial to the medial border of the scapula in Zone 3 in position 1.

DISCUSSION

Performing invasive procedures in the interscapular region, appropriate individualized positioning may reduce the risk of DSN injury.