From the Guidelines
The differential diagnosis and admission workup for altered mental status (AMS) and dementia should prioritize identifying potentially life-threatening causes in AMS, while focusing on characterizing the type of dementia and identifying reversible causes of cognitive decline in dementia, as evidenced by the most recent guidelines 1. The workup for AMS, which represents an acute change in cognition, should include a comprehensive emergency evaluation with:
- Vital signs
- Glucose check
- Complete blood count
- Comprehensive metabolic panel
- Urinalysis
- Toxicology screen
- Blood cultures if febrile
- Arterial blood gas
- Chest X-ray
- Head CT without contrast
- Possibly lumbar puncture Medications like naloxone for suspected opioid overdose or thiamine before glucose for suspected Wernicke's encephalopathy may be indicated, as supported by the American College of Radiology guidelines 1. In contrast, the workup for dementia, which involves gradual cognitive decline, is less urgent and includes:
- Cognitive assessment tools (MMSE or MoCA)
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests
- Vitamin B12 level
- Folate level
- Syphilis testing
- HIV testing in high-risk patients
- Brain imaging (preferably MRI) The key distinction is that AMS requires rapid identification of potentially life-threatening causes like infection, stroke, or toxicity, while dementia evaluation focuses on identifying reversible causes of cognitive decline and characterizing the type of dementia, as highlighted in the Journal of the American College of Radiology 1 and supported by previous studies 1. It is essential to note that delirium, a common cause of AMS, is a medical emergency that requires early detection and accurate diagnosis, as mortality in patients may be twice as high if the diagnosis of delirium is missed 1. In terms of neuroimaging, the primary role in the workup of patients with probable or possible dementia is to exclude other significant intracranial abnormalities, and advanced methods like volumetric MRI, amyloid PET, and FDG-PET are not routinely used in community or general practices for the diagnosis or differentiation of forms of dementia 1.
From the Research
Differential Diagnosis of Altered Mental Status (AMS) versus Dementia
The differential diagnosis for AMS is broad and includes various causes such as:
- Primary neurologic insults
- Systemic illnesses resulting in end-organ dysfunction of the brain
- Pharmacological and toxicological factors
- Systemic and organic causes
- Infectious causes
- Endocrine/metabolic disorders
- Psychiatric causes
- Traumatic causes
- Gynecologic and obstetric causes 2, 3
Admission Workup for Altered Mental Status (AMS)
The admission workup for AMS should include:
- A primary survey followed by a secondary survey with special attention to immediate life-threatening reversible causes
- A systems-based approach to search for any other life-threatening or reversible causes
- A comprehensive emergency department evaluation including a detailed history and physical exam
- Laboratory and radiographic testing to identify the underlying cause of AMS 2, 3
- Assessment for delirium, which is a more defined mental status change caused by another medical condition, and has a high morbidity and mortality if missed 4
Approach to Altered Mental Status in the Intensive Care Unit (ICU)
In the ICU, AMS should be evaluated for specific, treatable diseases affecting the central nervous system, rather than being diagnosed merely with syndromic labels such as toxic-metabolic encephalopathy (TME) and delirium 5
- A structured approach should be used to increase the probability of identifying specific causal etiologies of AMS in the critically ill
- Bedside assessment and common neurodiagnostic procedures, including specialized bedside modalities, should be used to evaluate patients with AMS in the ICU 5
Clinical Decision Rule for Predicting Outcomes of Emergency Department Patients with Altered Mental Status
A clinical decision rule can be used to predict admission risk among emergency department patients with AMS, based on variables such as:
- Vital sign abnormalities
- Select lab studies
- Psychiatric/intoxicant history
- This decision rule can sort patients into low, moderate, or high risk of admission and is predictive of 1-year mortality 6