Clearing up confusion

Medical illness
An organic basis must rank high in the dif­ferential diagnosis if medications are not the culprit. There are myriad medical disorders that can lead to confusion (Table 4).⁸ In an outpatient psychiatric setting, labo­ratory and radiology testing might not be readily available. It then becomes impor­tant to collaborate with a patient’s medical team if any of the following are met:
•there is high suspicion of a medical cause
•there could be delays in performing a medical workup
•a physical examination is needed.

Laboratory work-up should include:
•comprehensive metabolic panel (CMP) to assess for electrolyte derangements and liver or kidney disease
•urinalysis if there are signs of urinary tract infection (low threshold for test­ing in patients age >65 even if they are asymptomatic)
•urine drug screen or serum alcohol level if substance use is suspected
•complete blood count (CBC) if there are reports of infection (white blood cell count) or blood loss/bruising to ensure that anemia or thrombocytopenia is not playing a role
•thyroid-stimulating hormone (TSH) because thyroid disorders can cause neuro­psychiatric as well as somatic symptoms.⁹

Other laboratory testing could be valu­able depending on the clinical scenario. These include tests such as:
•drug level monitoring (lithium, val­proic acid, etc.) to assess for toxicity
•HIV and rapid plasma reagin for sus­pected sexually transmitted infections
•vitamin levels in patients with poor nutrition or post bariatric surgery
•erythrocyte sedimentation rate or C-reactive protein, or both, if there are signs of inflammation
•bacterial culture if blood or tissue infec­tion is a concern.

Esoteric tests include ceruloplasmin (Wilson’s disease), heavy metals screen, and even tests such as anti-gliadin anti­bodies because the prevalence of gluten sensitivity and celiac disease appear to be on the rise and have been associated with neuropsychiatric problems including encephalopathy.¹⁰

Brain imaging is an important consider­ation when a medical differential diagnosis for confusion is formulated. Unfortunately, there is little evidence-based guidance as to when brain imaging should be performed, often leading to overuse of tests such as CT, especially in emergency settings when con­fusion is noted. From a clinical standpoint, a head CT scan often is best ordered for patients who demonstrate an acute change in mental status, are age >70, are receiving anticoagulation, or have sustained trauma to the head. The key concern would be intracranial hemorrhage. However, some data suggest that the best use of head CT is for patients who have an impaired level of consciousness or a new focal neurologic deficit.¹¹

Apart from more acute changes, a brain MRI study is more helpful than a head CT when evaluating the brain parenchyma for more sub-acute diagnoses such as multiple sclerosis or a brain tumor. T2-weighted hyperintensities seen on an MRI are thought to predict an increased risk of stroke, dementia, and death.

Their discov­ery should prompt a detailed evaluation for risk factors of stroke and dementia/NCD.¹²

In Ms. T’s case, she was taking lithium, so it was logical to obtain a trough lith­ium level 12 hours after the last dose and to check kidney function (serum creati­nine to estimate the glomerular filtration rate), which were in the therapeutic/nor­mal range. Her serum lithium level was 0.7 mEq/L. Brain imaging was not ordered, but several other labs (CMP, CBC, hemoglo­bin A1c [HgbA1c], and TSH) were drawn. These labs were notable for HgbA1c of 5.1% (normal <5.7%) and TSH of 0.5 mIU/L (normal level, 1.5 mIU/L), which is low for someone taking thyroid replacement.

I requested that Ms. T stop Armour Thyroid to address the suppressed TSH. I also requested that she stop metfor­min because, although hypoglycemia from metformin monotherapy is uncom­mon, it can happen in older patients. Hypoglycemia associated with metformin also can occur in situations when caloric intake is deficient or when metformin is used in combination with other drugs such as sulfonylureas (ie, glipizide), beta-adrenergic blocking drugs, angiotensin-converting enzyme inhibitors, or even nonsteroidal anti-inflammatory drugs.¹³

Identifying overlapping psychiatric (or psychological) illness
Symptoms of depression, anxiety, psycho­sis, and even dissociation can present as con­fusion. The term pseudodementia describes patients who exhibit cognitive symptoms consistent with NCD but could improve once the underlying mood, thought, anxi­ety, or personality disorder is treated.

For example, a patient with depression typically exhibits neurovegetative symp­toms—such as poor sleep or appetite— amotivation, and low energy. All of these can lead to abrupt-onset cognitive changes, which are a hallmark of pseudodementia rather than the more insidious pattern of mild NCD. In cases of pseudodementia, neurocognitive testing will show impair­ment that often rapidly improves after the primary psychiatric (or psychological) issue is rectified. Making a diagnosis of pseu­dodementia at the initial presentation is difficult because neurocognitive tests such as the MMSE often fail to separate depres­sion from true cognitive changes.¹⁴ Such a diagnosis typically requires hindsight. Yet, one must also keep in mind that pseudode­mentia may be part of a NCD prodrome.¹⁵