Catatonia, a syndrome of motor, emotional and behavioral abnormalities frequently characterized by muscular rigidity and a trance-like mental stupor and at times manifesting with great excitement or agitation, can occur during a critical illness and appear similar to delirium. But the management strategies are vastly different.

A Vanderbilt University Medical Center (VUMC) study is the largest to look at the novel relationship between catatonia and delirium in critical illness and determine if catatonia can be reliably diagnosed in the setting of delirium.

This is important because managing each is different, said Jo Ellen Wilson, the lead author of the study, "The Delirium and Catatonia (DeCat) Prospective Cohort Investigation," recently published in Critical Care Medicine.

Benzodiazepines are the first-line treatment for catatonia, but antipsychotic drugs are avoided because they can worsen the condition, and if left untreated could result in death. However, antipsychotics are often used to manage delirium, so differentiating the two is critical, she said.

Because of the similarities, one can be misdiagnosed as the other, Wilson said. In the classical presentation of catatonia, people stare or are trance-like. There's also a hyperactive form where patients have abnormally frequent or bizarre movements and mannerisms and can become agitated. It can be brief or can go on for days or longer. 

"It can be tricky to distinguish one from the other. But there's a lot on the line with getting the accurate diagnosis," Wilson said. Although delirium is routinely screened for in all intensive care unit (ICU) patients, catatonia is not routinely screened for in the ICU.

"Our understanding of catatonia in the ICU is being hampered by a diagnostic dilemma," Wilson said. "The last three editions of the Diagnostic Statistical Manual (DSM), including the current edition, DSM-5, say that a diagnosis of catatonia due to another medical condition can't be made exclusively in the presence of delirium."

Wilson's blinded study looked at 136 critically ill patients at VUMC and independently evaluated them for the presence of delirium and catatonia. The patients were assessed using the Confusion Assessment Method for the ICU and the Bush Francis Catatonia Rating Scale. Of 136 patients, 58 (43%) had the only delirium, four (3%) had the only catatonia, 42 (31%) had both, and 32 (24%) had neither.

Additionally, Wilson's study showed that by using a revised cut-off of greater than or equal to four (items present), on the Bush Francis instrument, you could reliably diagnose catatonia with 91% sensitivity and specificity in the setting of delirium.

Wilson said the DSM is considered to be a "living document," and therefore new and compelling evidence should spur thoughtful considerations of changes in the diagnostic criteria of catatonia. Since her results found that approximately one out of three patients had co-occurring delirium and catatonia, and showed that catatonia could be reliably diagnosed in the setting of delirium using revised cut-off points on the most widely used rating scale, this suggests a reconsideration of the DSM-5 criteria for "Catatonia Due to Another Medical Condition."

"Going forward, the ICU practitioner should consider co-occurrence of catatonia in patients with persistent delirium, especially if several catatonia signs are present or if their clinical status worsens on antipsychotics," Wilson said.