Critical Care Medicine-Neurologic Disorders>>>>>Neuromuscular Disorders
Question 2#

A 14-year-old woman with medically intractable epilepsy presents to ED in status epilepticus. Three weeks prior, she had a “virallike illness” and had never fully returned to normal. She was having increased seizure frequency during that time. While in the ED, she was intubated for airway protection. Her workup reveals pyelonephritis, and she is treated with an appropriate course of antibiotics with improvement in her vitals and laboratory results. She had limited improvement in her mental status initially, and long-term electroencephalogram (EEG) monitoring revealed subclinical status epilepticus. Following 24 hours of burst suppression with propofol and midazolam, she had improvement in her EEG. Over the course of the next 72 hours, she had improvement in her mental status but was unable to be weaned from the ventilator because of poor tidal volumes during spontaneous breathing trials. On examination, she has marked proximal weakness in all four extremities. Electodiagnostic testing is completed, which demonstrates prolonged compound muscle action potential (CMAP) on nerve conduction studies and positive sharp waves and decreased recruitment on electromyography.

What is the MOST likely cause of her weakness?

a. Critical illness neuropathy
b. Critical illness myopathy
c. Acute demyelinating encephalomyelitis (ADEM)
d. Guillain-Barré syndrome (GBS)
e. Inflammatory myopathy (eg polymyositis)

Correct Answer is B

Comment:

Correct Answer: B

The patient has quadriparesis including respiratory weakness with electrodiagnostic testing consistent with a myopathic disease process. Given her recent intubation, sedation, sepsis, and limited mobility due to burst suppression, these point to critical illness myopathy as the underlying disease process. Risk factors for critical illness myopathy include sepsis, high-dose glucocorticoids, prolonged neuromuscular blockade, hyperglycemia, immobility, vasopressor use, renal replacement therapy, and trauma. In critical illness neuropathy, the common findings are decreased amplitude of both sensory and motor nerve responses with normal spontaneous activity on EMG. Although not required to make the diagnosis, muscle biopsy in critical illness myopathy will typically demonstrate loss of myosin. There are no specific treatments for critical illness myopathy although strict glucose control can decrease the risk and early mobility may improve function. Although the patient had a “virallike illness” before her presentation, the nerve conduction findings are not consistent with a demyelinating disease process such as GBS. Although ADEM can present with quadriparesis due to high cervical cord involvement, the nerve conduction findings are not consistent with this diagnosis. Although an inflammatory myopathy is unlikely the cause, given her other ongoing critical illness.

References:

  1. Latronico N, Bolton CF. “Critical illness polyneuropathy and myopathy: a major cause of muscle weakness and paralysis.” Lancet Neurol. 2011;10:931-941.
  2. Bolton CF, Gilbert JJ, Hahn AF, Sibbald WJ. “Polyneuropathy in critically ill patients.” J Neurol Neurosurg Psychiatry. 1984;47:1223-1231.