All elevated creatine kinase is not neuroleptic malignant syndrome

Creatine kinase (CK) is an enzyme that is found widely in muscle tissues. Raised levels would occur when there is muscle damage. Raised levels are used as one of the diagnostic criteria for Neuroleptic Malignant Syndrome (NMS). This study looks at CK levels in 30 psychotic inpatients without NMS and compares them with 10 patients with NMS. It was found that 67% of the patients without NMS had raised CK levels, 20% of whom had levels in excess of 1000 IU/L. The rest had a two to five-fold increase over normal limits. Raised levels were associated with the use of intramuscular injections and physical restraints, situations which are well known to result in muscle injury. All the NMS patients had raised CK levels but 40% had levels below 1000 IU/L. Our findings support the idea that CK levels, though helpful, should be interpreted with care as raised levels are nonspecific.