Those with hypoactive delirium present with similarly to retarded catatonia, withdrawn and quiet. However, catatonia also includes other distinguishing features including posturing and rigidity as well as a positive response to benzodiazepines. Patients with locked-in syndrome present with immobility and mutism; however, unlike patients with catatonia who are unmotivated to communicate, patients with locked-in syndrome try to communicate with eye movements and blinking. Furthermore, locked-in syndrome is caused by damage to the brainstem. Stiff-person syndrome and catatonia are similar in that they may both present with rigidity, autonomic instability and a positive response to benzodiazepines. However, stiff-person syndrome may be associated with anti-glutamic acid decarboxylase (anti-GAD) antibodies and other catatonic signs such as mutism and posturing are not part of the syndrome. Untreated late-stage Parkinsons disease may present similarly to retarded catatonia with symptoms of immobility, rigidity, and difficulty speaking. Further complicating the diagnosis is the fact that many patients with Parkinsons disease will have major depressive disorder, which may be the underlying cause of catatonia. Parkinsons disease can be distinguished from catatonia by a positive response to levodopa. Catatonia on the other hand will show a positive response to benzodiazepines. Extrapyramidal side effects of antipsychotic medication, especially dystonia and akathisia, can be difficult to distinguish from catatonic symptoms, or may confound them in the psychiatric setting. Extrapyramidal motor disorders usually do not involve social symptoms like negativism, while individuals with catatonic excitement typically do not have the physically painful compulsion to move that is seen in akathisia.
Metabolic screens, inflammatory markers, or autoantibodies may reveal reversible medical causes of catatonia.Vital signs should be frequently monitored as catatonia can progress to malignant catatonia which is life-threatening. Malignant catatonia is characterized by fever, hypertension, tachycardia, and tachypnea. Rating scale
Various rating scales for catatonia have been developed, however, their utility for clinical care has not been well established. The most commonly used scale is the Bush-Francis Catatonia Rating Scale (BFCRS) (external link is provided below). The scale is composed of 23 items with the first 14 items being used as the screening tool. If 2 of the 14 are positive, this prompts for further evaluation and completion of the remaining 9 items. A diagnosis can be supported by the lorazepam challenge or the zolpidem challenge. While proven useful in the past, barbiturates are no longer commonly used in psychiatry; thus the option of either benzodiazepines or ECT. Differential diagnosis
The differential diagnosis of catatonia is extensive as signs and symptoms of catatonia may overlap significantly with those of other conditions. Therefore, a careful and detailed history, medication review, and physical exam are key to diagnosing catatonia and differentiating it from other conditions. Furthermore, some of these conditions can themselves lead to catatonia. The differential diagnosis is as follows:

Neuroleptic malignant syndrome (NMS) and catatonia are both life-threatening conditions that share many of the same characteristics including fever, autonomic instability, rigidity, and delirium. Lab values of low serum iron, elevated creatine kinase, and white blood cell count are also shared by the two disorders further complicating the diagnosis.