Rationale: A substantial overlap exists between catatonic phenomena and features of neuroleptic malignant syndrome.
Objectives: The objective of this study is to examine whether catatonia can be distinguished from neuroleptic malignant syndrome and to identify symptoms that may have discriminatory power.
Methods: We conducted a literature search to identify relevant studies up to and including the year 2012. A total of 386 studies containing 490 case reports were included. To evaluate the discriminant value of each feature, we performed binominal regression analyses with the diagnosis as the dependent variable. First, all features were entered into the model as independent variables. In a second step, a stepwise backwards analysis was conducted to eliminate criteria with low discriminant value.
Results: The most common symptoms in patients with neuroleptic malignant syndrome were fever (87.7 %), rigor (85.9 %), laboratory evidence of muscle injury (70.5 %), and tachycardia (62.1 %) and in patients with catatonia were mutism (78.0 %), rigor (73.0 %), stupor (54.0 %), and agitation (49.0 %). Eleven variables with statistically significant discriminatory power remained after statistical analysis: diaphoresis (odds ratio (OR) 10.011), rigor (OR 9.550), fever (OR 7.317), tremor (OR 4.064), laboratory evidence of muscle injury (OR 3.542), leukocytosis (OR 3.081), negativism (OR 0.262), posturing (OR 0.241), waxy flexibility (OR 0.223), stupor (OR 0.158), and stereotypy (OR 0.122).
Conclusions: Catatonia and neuroleptic malignant syndrome can be distinguished, at least on a descriptive level. There is a strong syndromal overlap. Our findings might be influenced by the fact that they are based on case reports, which reflect the respective authors' clinical opinion of the patient's condition.