What is the most appropriate initial imaging study for an elderly female patient with a Montreal Cognitive Assessment (MOCA) score of 26/30 and intermittent confusion?

Imaging for Elderly Female with MoCA 26/30 and Intermittent Confusion

CT head without IV contrast is the most appropriate initial imaging study for this patient, given the intermittent confusion suggesting possible delirium superimposed on mild cognitive impairment. 1

Clinical Context and Diagnostic Approach

This patient presents with two distinct clinical features requiring different imaging considerations:

Intermittent Confusion (Delirium Component)

The intermittent nature of confusion suggests delirium or altered mental status rather than pure cognitive impairment, making CT head without contrast the first-line imaging choice. 1

• CT head without contrast is the initial test of choice for acute or fluctuating mental status changes, as it can be performed safely and rapidly to detect acute intracranial pathology 1
• Yield of acute contributory findings on CT ranges from 2% to 45% in patients with altered mental status 1
• Risk factors that increase likelihood of positive findings include older age, history of falls, anticoagulant use, and impaired consciousness 1
• The reported detection of treatment-altering findings is low in elderly patients with new onset delirium unless risk factors are present (focal neurologic deficit, recent falls, anticoagulation therapy, signs of elevated intracranial pressure) 1

MoCA Score of 26/30 (Mild Cognitive Impairment)

The MoCA score of 26/30 sits at the threshold for possible cognitive impairment:

• A MoCA score of 26 or above is typically used to indicate normal cognition, with scores below 26 suggesting possible impairment 1
• However, the MoCA has high sensitivity (94-95%) but low specificity (37-73%) at the 26 cutoff, meaning many false positives occur 2
• In an old age psychiatry setting, MoCA ≥26 has 95% sensitivity for confirming normal cognition but only 33% positive predictive value for diagnosing MCI 2
• The optimal cutoff for detecting MCI is actually 24/25 (sensitivity 80.48%, specificity 81.19%) rather than 26 3

Imaging Algorithm

Immediate Priority: Address Intermittent Confusion

1. Obtain CT head without IV contrast first to exclude acute pathology causing delirium 1
   • This detects subdural hematomas, acute hemorrhage, large masses, and hydrocephalus 1
   • Can be performed rapidly in all patients 1

Secondary Evaluation: Assess Cognitive Impairment

1. If CT is negative and confusion resolves, proceed with MRI brain without IV contrast for comprehensive dementia evaluation 1, 4

   • MRI is superior to CT for detecting hippocampal atrophy, vascular lesions, and microhemorrhages 4
   • MRI can identify atrophy patterns suggesting specific neurodegenerative diagnoses 4
   • MRI excludes potentially reversible causes including tumors, inflammatory conditions, and normal-pressure hydrocephalus 4

2. If confusion persists despite clinical management, MRI brain without and with IV contrast becomes appropriate 1

   • Contrast is indicated if intracranial infection, tumor, or inflammatory pathologies are suspected 1

Important Clinical Caveats

The low diagnostic yield of neuroimaging must be weighed against the risk of missing preventable morbidity, particularly in elderly patients who may lack obvious clinical signs predicting focal pathology. 1

• The distinction between delirium and dementia is critical: delirium is acute/fluctuating while dementia is chronic/progressive 1
• Many elderly patients have mixed pathology, with both neurodegenerative changes and acute superimposed processes 4
• A negative CT does not exclude cognitive impairment; MRI remains necessary for comprehensive dementia evaluation if cognitive concerns persist 4

MRI is strongly preferred over CT when evaluating for dementia specifically, but CT is appropriate for initial assessment of acute confusion. 1, 4

When to Skip Imaging

Neuroimaging may be deferred if:

• The etiology of confusion is clearly identified (medication-related, infection, metabolic derangement) 1
• There is low clinical suspicion for intracranial pathology 1
• The patient shows rapid symptomatic improvement with treatment of the underlying cause 1

However, given this patient's age and cognitive score at the threshold of impairment, imaging is warranted even if an alternative explanation for confusion is identified. 1