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Understanding the Brachial Plexus Injury: Part 2 (Shoulder Dystocia)

Posted by Trisha Haszel Kreibich on Fri, Nov 5, 2010
By: Trisha Kreibich, MS, Medical Illustrator/Consultant, and Robert Shepherd, MS, CMI, Medical Illustrator, Executive Vice President and Operations Director, Eastern Region MediVisuals Inc

This article is a continuation of a two part article on brachial plexus injury. Part 1 covered brachial plexus injuries in adults caused by a traumatic event, such as a motor vehicle collision. Part 2 will address brachial plexus injury in infants during delivery, which is also known as Shoulder Dystocia or Erb's palsy.

To review, the brachial plexus innervates the arm and is formed by several of the cervical nerve roots and the T1 nerve root. [see illustration below]

Pediatric Brachial Plexus

During delivery, the infant's passage through the birth canal can be stopped by the impaction of its shoulder(s) against the mother's pubic bone, sacral promontory, or both. [see illustration below]

Shoulder Dystocia

Injury to the brachial plexus may sometimes occur because of unusually powerful uterine contractions or rapid fetal descent; however, brachial plexus injury may also result from improper obstetrician interaction. When excessive downward traction on the head of an infant with shoulder dystocia is applied (a violation of the standard of care), the delicate brachial plexus is stretched and injured. [shown below] The same may also occur when vacuum extraction is used in this situation.

Shoulder Dystocia and Excessive Traction

As in adult brachial plexus injuries, the earlier the injury is identified and treated, the better chances are for recovery and preventing permanent damage. However, this is also dependent on the severity of the initial injury. Sometimes, an overgrowth of nerve cells (neuroma) can form around the injured nerves. When this occurs, surgical intervention and nerve grafting may be needed. [see illustration below]

Sural Nerve Graft

There are some delivery techniques that can be used to prevent brachial plexus injury in infants with shoulder dystocia. As the illustration below demonstrates, the mother is moved to the McRoberts position, where her legs are hyperflexed to the abdomen, typically resulting in an increase of the outlet. This is often used in conjuction with an episiotomy, a cut made in the perineal body (tissue between the vagina and anus) before delivery, to enlarge the outlet and allow the obstetrician more room to perform maneuvers.

McRoberts Position

If no progress is made, moderate suprapubic pressure may be applied to free the impacted shoulder. The Wood's screw maneuver [shown below] may be used as well. This maneuver involves the obstetrician rotating the infant's anterior or posterior shoulder, and in turn the body, like a screw, freeing the impacted shoulder.

Woods Screw Maneuver 604058 03X

The following animation was developed to show how brachial plexus injuries can occur in a shoulder dystocia case, along with a few of the above mentioned accepted procedures that can be performed to help prevent this injury.

Shoulder Dystocia Animation

Reference:

Gabbe, S.G., Niebyl, J. R., & Simpson, J.L. "Obstetrics: Normal & Problem Pregnancies." 3rd ed. Philadelphia: Churchill Livingstone, 1996. 374-375, 490-494. Print.

Topics: mechanism of injury, brachial plexus, Erb's palsy, trial exhibit, medical-legal-illustration, birth trauma, medical exhibit

Understanding the Brachial Plexus Injury: Part 1

Posted by Trisha Haszel Kreibich on Thu, Oct 21, 2010

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

Injuries to the brachial plexus can often take place from trauma similar to that which causes cervical spine injuries and can also manifest similar symptoms. As shown in the illustration below, the brachial plexus is formed by several of the cervical nerve roots and the T1 nerve root.

Brachial Plexus 205299 02XA

Sometimes injury to the brachial plexus can be the direct result of excessive stretch during a traumatic event. For example, in a motor vehicle collision with a violent side impact the nerves on the contralateral side of the impact (and resulting flexion) may be stretched and/or torn. [see illustration below]

Brachial Plexus R14893 05X

Injury to the surrounding muscles can indirectly cause injury to the brachial plexus, as well. The brachial plexus runs between the anterior and middle scalene muscles, which connect the cervical spine and first rib. In a motor vehicle collision, hyperextension of the neck may excessively stretch these muscles, as demonstrated in the illustration below.

Brachial Plexus 306036 01XB

When these muscles are stretched, the resulting swelling or spasm can result in symptoms consistent with cervical nerve root injury even though the cervical nerve roots or brachial plexus themselves may not be directly injured. [see illustration below]

Brachial Plexus 205299 02XB

Thoracic outlet syndrome is another mechanism by which the brachial plexus can be injured. The illustration below shows that the axillary sheath, which contains the nerves from the brachial plexus and the axillary vein and artery, passes through the opening created between the clavicle and first rib.

Brachial Plexus 399048 04Apart2

Thoracic outlet syndrome can occur either by (1) the elevation of the first rib due to spasm of the scalenes or (2) the loss of innervation to the trapezius and/or other muscles that insert on the clavicle or scapula, causing the shoulder to droop [see illustration below]. By either mechanism, the opening between the clavicle and first rib is closed and the nerves and blood vessels that travel through the thoracic outlet become compressed.

Brachial Plexus 399048 04Apart1

As one can see in the illustration below, an injury to the brachial plexus affects the motor and sensory function of the arm. The earlier the injury is identified and treated, the better chances are for recovery and preventing permanent damage. However, this is also dependent on the severity of the initial injury. Sometimes surgical intervention is needed to address torn/ruptured nerves and excessive scarring.

Brachial Plexus R16249 01XB

This is the first of a two part article. Please check back to read Part 2, which discusses brachial plexus injury in infants during delivery (Shoulder dystocia). You can also sign up for email alerts, which announce when another article has been posted.



Topics: brachial plexus, Erb's palsy, trial exhibit, medical-legal-illustration, birth trauma, shoulder dystocia, throacic outlet syndrome, medical exhibit