Primer on Critical Illness Myopathy for General Readers

Neurology in Critical Care

Despite the fact that Critical Care and Neurology are separately relatively “glamorous” medical disciplines, neurological diseases in the critical illness setting receive relatively little attention. However, if one is in the business of intervening to make major improvements to patients’ outcomes (which we should be), then perhaps Neurologists as a group should focus a little more on this clinical setting.

There are two ways in which neurological diseases impact on critical care, typified by a patient management setting such as an intensive treatment unit (ITU) or high dependency unit.

• First, a number of neurological diseases constitute the primary reason why patients need critical care. Examples vary from stroke, the most common cause of disability in developed countries, to Guillain Barre syndrome, myasthenia gravis, inflammatory encephalopathies and rare metabolic diseases. Some of these conditions have the potential to remit spontaneously or with treatment and so if the patient can be “tided” over a critically ill period successfully, the eventual prognosis may be excellent. Optimal management of such patients may therefore make a huge difference to patient outcome.
• Second, even when the primary condition is not neurological, the critically ill patient may suffer a number of secondary neurological complications which may then become a major factor limiting outcome. These include delirium and hallucinations, nerve pressure palsies, critical illness neuropathy and critical illness myopathy; the last of these is the focus of this post.

Critical Illness Myopathy

A myopathy simply refers to any disease of the muscles, while a neuropathy refers to diseases of the nerves whose function is to transmit movement signals to the muscles or sensory signals back to the brain. For reasons that are not entirely clear, but which we will speculate upon, the muscles (more commonly) and the nerves are susceptible to damage in any patient undergoing intensive care; a myopathy occurs in 25-50% of cases where there is sepsis, multi-organ failure or a stay longer than seven days. At worst this may result in lasting disability, but at best may still significantly delay weaning off the ventilator and return to mobility. This has cost implications as well as implications regarding the extra suffering experienced by such patients.

The reasons why I wanted to conduct a journal review on this topic, for which this is the accompanying primer, are:

• I had incorrectly assumed that critical illness myopathy was very rare until I had cause to research it in relation to one of my patients and I wonder if some colleagues might be under a similar misapprehension.
• I wanted to explore any treatment options for this common and important condition.
• I wanted to see if there were risk factors that would predict likely development of critical illness myopathy before patients get it and to diagnose them accurately when they do get it.
• In reference to the latter, I was particularly concerned with difficulty in diagnosis when, as may hardly be unexpected if one is a Neurologist, the primary condition rendering the patient requiring intensive care is also neurological. How may we determine, for example, if a patient’s failure to wean from ventilation or to develop return in muscle strength is due to their Guillain Barre syndrome, or a secondary critical illness neuromyopathy?

More Background Information

There is a website providing information and support for patients and relatives with problems related to critical care called ICU Steps.