A 22-year-old primigravida at 34 weeks gestation is brought to the emergency department by ambulance due to sudden loss of consciousness followed by generalized shaking. The paramedics initiated an intravenous magnesium sulfate bolus, which was infusing rapidly when the patient arrived at the hospital. She says she is very tired and has blurry vision and a headache. The patient also has muscle pain and sore joints and is unable to move her right arm. Blood pressure is 145/98 mm Hg, pulse is 112/min, and respirations are 16/min. She holds the right arm adducted and internally rotated. Examination shows loss of external rotation of the right arm but no sensory deficits. Deep tendon reflexes are 2+ bilaterally, and handgrip and wrist strength are preserved on both sides. Urinalysis shows 3+ protein. Which of the following is the most likely cause of this patient's right arm findings?

Question

A 22-year-old primigravida at 34 weeks gestation is brought to the emergency department by ambulance due to sudden loss of consciousness followed by generalized shaking.  The paramedics initiated an intravenous magnesium sulfate bolus, which was infusing rapidly when the patient arrived at the hospital.  She says she is very tired and has blurry vision and a headache.  The patient also has muscle pain and sore joints and is unable to move her right arm.  Blood pressure is 145/98 mm Hg, pulse is 112/min, and respirations are 16/min.  She holds the right arm adducted and internally rotated.  Examination shows loss of external rotation of the right arm but no sensory deficits.  Deep tendon reflexes are 2+ bilaterally, and handgrip and wrist strength are preserved on both sides.  Urinalysis shows 3+ protein.  Which of the following is the most likely cause of this patient's right arm findings?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d1b8_5cce_bc81_f358f13bdd93_MD0003_00 This pregnant patient experienced loss of consciousness with generalized shaking (likely representing a tonic-clonic seizure) and has hypertension and proteinuria, findings consistent with eclampsia. Violent muscle contractions, as seen in a seizure or electrocution injury, are a common cause of posterior shoulder dislocation. In a posterior dislocation, the arm is typically held in adduction and internal rotation, with impaired external rotation, visible flattening of the anterior aspect of the shoulder, and prominence of the coracoid process. Radiographic findings may include the following: Radiographic findings Loss of the normal overlap between the humeral head and the glenoid Internal rotation of the humeral head, which causes a circular appearance (light bulb sign) on anterior views Widened joint space >6 mm (rim sign) or 2 parallel cortical bone lines on the medial aspect of the humeral head (trough line sign) Potential complications include fractures of the proximal humerus, labral injuries, and tears to the rotator cuff system. Most posterior dislocations are managed with closed reduction. (Choice A) Anterior dislocation is the most common form of shoulder dislocation and is usually caused by a direct blow or fall on an outstretched arm. In anterior dislocations, the patient holds the arm slightly abducted and externally rotated. (Choice B) Common adverse effects of magnesium sulfate include headache, nausea, fatigue, and diaphoresis. Signs of magnesium toxicity include somnolence, loss of deep tendon reflexes, and respiratory depression, but not focal weakness. This patient's reflexes are normal. (Choice D) Todd paralysis refers to transient unilateral weakness following a tonic-clonic seizure that usually resolves spontaneously. Adduction and internal rotation of the arm are not seen. (Choice E) Radial nerve compression from trauma can occasionally be seen in shoulder dislocations but most commonly occurs in the forearm. It often results in weakness of wrist extension and decreased handgrip, which are not seen in this patient. Educational objective: Violent muscle contractions (eg, seizure, electrocution injury) can cause posterior shoulder dislocation. On examination, the arm is held in adduction and internal rotation, with flattening of the anterior aspect of the shoulder. X-ray shows loss of the normal relation between the humeral head and glenoid and internal rotation of the humeral head. Most posterior dislocations are managed with closed reduction. References: Neglected bilateral posterior shoulder fracture dislocation in an uncontrolled seizure patient. (http://www.ncbi.nlm.nih.gov/pubmed/26430452)

A 22-Year-Old Primigravida at 34 Weeks Gestation Is Brought to the Emergency