Critical illness polyneuropathy
Critical illness polyneuropathy | |
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Specialty | Neurology |
Critical illness polyneuropathy (CIP) and critical illness myopathy (CIM) are overlapping
CIP was first described by
Combined CIP and CIM was first described by Nicola Latronico in a series of 24 patients.[7]
Signs and symptoms
People with CIP/CIM have diffuse, symmetric, flaccid muscle weakness. CIP/CIM typically develops in the setting of a critical illness and immobilization, so patients with CIP/CIM are often receiving treatment in the intensive care unit (ICU).[citation needed]
Weakness (motor deficits) occurs in generalized fashion, rather than beginning in one region of the body and spreading. Limb and respiratory (diaphragm) muscles are especially affected.
Respiratory difficulties can be caused by atrophy of the muscles between the ribs (intercostals), atrophy of the
Cause
The causes of CIP and CIM are unknown, though they are thought to be a possible neurological manifestation of systemic inflammatory response syndrome.[3][10]
Pathology
Nerve biopsy would show axonal neuropathy,
Unlike
Diagnosis
CIP and CIM are a major cause of ICU-acquired weakness (ICUAW). Current guidelines recommend a clinical diagnosis of ICUAW, made by manually testing the muscle strength with the use of the Medical Research Council (MRC) sum score or handgrip dynamometry.[12]
CIP/CIM is often not identified until a patient is unable to be successfully weaned from a mechanical ventilator. Early detection of the condition is difficult, because these patients are often sedated and intubated, and thus unable to cooperate with a thorough neuromuscular physical examination.[11] The use of conventional nerve conduction studies is time-consuming and requires specialized personnel; however, simplified electrophysiologic tests can be used as screening tools in the critically ill to confirm or exclude CIP/CIM.[13][14] The peroneal nerve test is a validated, high-sensitivity, minimally invasive, non-volitional and quick diagnostic test which can accurately exclude CIP/CIM if the result is normal.[13] Moreover, patients with disuse atrophy and muscle deconditioning have normal electrophysiological tests even if muscle strength is severely reduced[14] Hence, these tests are important to define the cause of muscle weakness and can be helpful to refine the prognosis.[15]
Laboratory values
The serum
Screening
Initial screening for CIP/CIM may be performed using an objective scoring system for muscle strength. The Medical Research Council (MRC) score is one such tool, and sometimes used to help identify CIP/CIM patients in research studies. The MRC score involves assessing strength in 3 muscle groups in the right and left sides of both the upper and lower extremities. Each muscle tested is given a score of 0–5, giving a total possible score of 60. An MRC score less than 48 is suggestive of CIP/CIM. However, the tool requires that patients be awake and cooperative, which is often not the case. Also, the screening tool is
Once weakness is detected, the evaluation of muscle strength should be repeated several times. If the weakness persists, then a muscle biopsy, a nerve conduction study (electrophysiological studies), or both should be performed.[11]
Prognosis
CIP/CIM can lead to difficulty weaning a person from a
Critically ill people that are in a
Epidemiology
While the exact incidence is unknown, estimates range from 33 - 57 percent of patients staying in the ICU for longer than 7 days.[9] More exact data is difficult to obtain, since variation exists in defining the condition.
The three main risk factors for CIP and CIM are
Certain medications are associated with CIP/CIM, such as
History
CIP was first described in 1984 by
Terminology
A number of terms are used to describe critical illness polyneuropathy, partially because there is often neuropathy and myopathy in the same person, and nerve and muscle degeneration are difficult to distinguish from each other in this condition. Terms used for the condition include: critical illness polyneuromyopathy, critical illness neuromyopathy, and critical illness myopathy and neuropathy (CRIMYNE).[17][18][13] Bolton's neuropathy is an older term, which is no longer used.