INTRODUCTION: Myasthenia Gravis (MG) is an autoimmune neuromuscular junction disorder. Although not a rare condition, it only has an annual incidence of 10 per million in the United States. MG has been noted to have female predominance, in the second and third decades, while in males the highest incidence occurs in the seventh decade. MG most commonly arises with an indolent onset of symptoms such as ocular, bulbar and limb muscles weakness. Myasthenic Crisis (MC) is a condition that is characterized by severe weakness secondary to MG necessitating intubation for ventilatory support or airway protection. Approximately 20% of patients with MG experience MC which typically occurs within the first year or two after diagnosis. MC is more common in patients with oropharyngeal weakness and thymoma; furthermore, it is exacerbated by a multitude of clinical conditions and routinely used medications. We report an unusual occurrence of MG presenting for the first time as Myasthenic Crisis in the post partum period.
CASE PRESENTATION: Our patient is a 21-year-old African American Female G3P2103 who was successfully extubated in the operating room following emergent Caesarian section (for cord prolapse) under general endotracheal anesthesia and succinylcholine. Two hours post-operatively while in the recovery room the patient was noted to have a blood pressure of 180/120 with tonic-clonic shaking movements. She was reintubated for airway protection after receiving boluses of succinylcholine and magnesium sulfate. She was subsequently placed on mechanical ventilation and started on a magnesium drip for eclampsia and empiric broad spectrum antibiotics including gentamicin. Soon after, all sedation was stopped and the magnesium drip was discontinued. Five hours following reintubation, the patient was awake, alert and following commands while continuing to require ventilator support. Her vital signs remained stable. Neurological exam was performed and was remarkable for bilateral ophthalmoplegia. The pupils were bilaterally equal and reactive to light but she was unable to track objects. The oculocephalic (Doll's eyes) reflex was also absent. Surprisingly, she was able to visually track objects by lifting and turning her head. Her deep tendon reflexes were brisk and symmetrical with normal motor strength and an intact sensory system. A Computed Tomography (CT) scan of the head was normal. Our findings suggested bilateral ocular myopathy in the setting of acute respiratory failure. Our differential diagnoses included; Myasthenia Gravis, Botulism, Tick paralysis, Lambert Eaton Syndrome, Organophosphate poisoning and Guillain-Barre Syndrome. Electromyography with repetitive nerve stimulation revealed decremental motor response consistent with Myasthenia Gravis. This was later confirmed by positive serum acetylcholine receptor antibodies. Our patient was started on plasmapheresis. Her weaning parameters started improving after the second plasma exchange and she was successfully extubated after the third session. A routine CT of the chest demonstrated an age related excess of thymus tissue.
DISCUSSIONS: Currently with the advent of therapy the incidence of MC has diminished. This, however, does not pertain to those Myasthenia patients who initially present in crisis, as seen in our case. MC not only requires timely recognition but also the identification of precipitating factors. Such factors noted in our patient included the stresses of pregnancy and surgery, the use of medications such as a neuromuscular junction blocker (succinylcholine), magnesium sulfate and an aminoglycoside (Gentamicin). The current treatment modalities for MC include plasmapheresis and IV immunoglobulin, while trials with steroids are reserved for non-responders. Anticholinesterase drugs and immunomodulators are the cornerstone for chronic and maintenance therapy.
CONCLUSION: Neuromuscular causes should be considered in all young patients presenting with acute respiratory failure, with a special consideration for MC in those within the specific sex, age group, and precipitating factors.
DISCLOSURE: Peggy Rahal, None.