Altered mental status

The encephalopathic and intracranial disease processes causing acute alteration in mental status is discussed in the second of two columns on the topic.


Last month's column dealt with the psychiatric conditions causing altered mental status, as well as the significance of altered levels of consciousness and application of the Glasgow Coma Scale (GCS). This month, we will address the encephalopathic and intracranial disease processes causing acute alteration in mental status, as well as the importance of documentation that accurately reflects severity and enables correct coding.

Photo by Thinkstock
Photo by Thinkstock

The most common cause of acutely altered mental status among patients requiring admission to the hospital is almost certainly acute metabolic or toxic encephalopathy. In contrast to chronic, irreversible, structural encephalopathies, like heavy metal toxicity or anoxic brain damage, an acute encephalopathy is defined by generalized brain dysfunction due to underlying systemic factors, causing acute mental status alteration that returns to baseline when corrected.

Metabolic encephalopathy is caused by systemic metabolic disorders such as fever, dehydration, electrolyte imbalance, hypoxemia, infection, or organ dysfunction. The code for toxic encephalopathy is intended to capture the effects of nonmedicinal drugs and toxins, but many clinicians use the term to describe metabolic encephalopathy when the patient appears to be “toxic.” Toxic-metabolic encephalopathy describes a patient with both metabolic and toxic causes of encephalopathy. The general term “encephalopathy” can also be used without further specification for these patients because the severity and reimbursement impact is the same.

Other specific types of encephalopathy include hepatic, alcoholic, and hypertensive. For correct coding, when hepatic encephalopathy is diagnosed, it is important to state whether coma is present. With alcoholic encephalopathy, delirium tremens should be documented if present. If a patient has hypertensive encephalopathy, don't forget that this represents a hypertensive emergency as well.

Encephalopathy can be either hypoactive with an altered level of consciousness or hyperactive. For the former, always calculate a GCS and consider whether coma might be an appropriate diagnosis. Hyperactive encephalopathy may become severe enough to cause delirium but, as noted in last month's column, delirium is not a disease process but rather an acute clinical syndrome with an underlying cause. Manifestations include confusion, disorientation, agitation, inattention, disorganized behavior, and sometimes hallucinations.

An acute alteration in mental status due to intracranial disease processes is usually characterized by an alteration in level of consciousness, such as lethargy, obtundation, or coma. That differs from true encephalopathy, which should be reserved for mental status alteration resulting from systemic factors. The GCS should be calculated whenever there is an altered level of consciousness and, if severe, consideration should be given to the diagnosis of coma that has a major impact on severity of illness classification for quality metrics and compensation.

Intracranial disease processes can be classified as more or less focal or primarily generalized in nature. Focal lesions include stroke, hemorrhage/hematoma, neoplasm, abscess, and trauma with or without brain compression. Generalized intracranial processes are such things as cerebral edema, infections like meningitis, encephalitis, or diffuse traumatic injury (often with cerebral edema and/or focal lesions).

Brain compression is a very important diagnostic consideration that has a major impact on severity of illness. It is defined as displacement of brain by extrinsic or intrinsic pressure due to a focal lesion or cerebral edema. Radiographic findings may include mass effect, midline shift, brain herniation (across fixed intracranial structures), effacement of ventricles and/or sulci, localized edema, or a “space-occupying lesion.” Whenever these are identified, the clinician must specifically document that brain compression is present for correct coding.

Brain herniation is usually due to brain compression and is itself another important diagnosis that should also be documented whenever it occurs. Common sites of herniation include transtentorial (central and uncal), subfalcine (cingulate) under the falx cerebri, tonsillar, and through the foramen magnum.

In summary, altered mental status is not a diagnosis but rather a group of variable, nonspecific neurologic symptoms with psychiatric, encephalopathic, and intracranial pathologic causes that should always be precisely documented and coded. It is essential for clinicians to identify and document encephalopathy, coma, cerebral edema, brain compression, and herniation. A clear understanding of the clinical syndromes of delirium and altered consciousness are necessary for diagnostic classification, documentation, and coding purposes. The GCS should be clearly documented in the medical record.