1337 - Can’t Stop Won’t Stop – Post-hypoxic Myoclonus in a Patient with Myasthenia Gravis

Friday, February 23, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

ZS

Zachary JC Shumaker, MD

Resident
Carolinas Rehabilitation/Atrium Health
Charlotte, North Carolina, United States
MC

Margaret Clinard, BS

Medical Student
Edward Via College of Osteopathic Medicine
Blacksburg, Virginia, United States

Co-Author(s)

TT

Tobias J. Tsai, MD

Medical Director, Pediatric Rehabilitation
Carolinas Rehabilitation/Atrium Health Levine Children's Hospital
Charlotte, North Carolina, United States
LS

Laurel Socha, MSN

Nurse Practitioner
Levince Children's Hospital
Charlotte, North Carolina, United States

Case Diagnosis:
Post-hypoxic action myoclonus due to hypoxic brain injury in a patient with myasthenia gravis (MG).

Case Description:
An 11-year-old girl with a six-month history of bulbar weakness experienced hypoxic cardiac arrest and was subsequently diagnosed with myasthenia gravis. She was treated with intravenous immune globulin, steroids, pyridostigmine, and azathioprine. On day two of hospitalization, she developed a generalized action myoclonus. Magnetic resonance imaging revealed abnormal hyperintense T2 signal in the bilateral caudate and putamen. Electroencephalography was negative for seizure. Inpatient rehabilitation was recommended for dysphagia and impaired mobility. Gastrostomy tube was placed. Difficulty maintaining a state of rest exacerbated myasthenic fatigue; antiepileptics for myoclonus and power mobility for energy conservation allowed functional progress.

Discussions:
Post-hypoxic myoclonus (also known as Lance-Adams syndrome) and MG are both rare conditions, and to date have not been reported in the same patient. While symptoms of MG may improve with rest, the combination of myoclonus and MG led our patient to fatigue easily, limiting initial therapy performance. She trialed multiple antiepileptics for management of myoclonus. Levetiracetam was ineffective. She tolerated low-dose clonazepam with some benefit, and showed the most improvement with gabapentin. High doses were avoided to avoid exacerbating weakness in the context of MG. Power mobility using a head array successfully allowed energy conservation, increasing her mobility.

Conclusions: This is the first report of MG and post-hypoxic myoclonus in the same patient. When those diagnoses co-exist, careful use of antiepileptics, combined with access to power mobility, can optimize energy conservation and function.