This led to a research group at NIMH creating new diagnostic criteria for PANS (Pediatric Acute-onset Neuropsychiatric Syndrome), which focused entirely on the symptomatology and not on the cause (Swedo et al. 2012).
Criteria for PANS
1. Acute, dramatic onset of OCD or severely restricted food intake.
2. Concurrent presence of additional neuropsychiatric symptoms, with similarly severe and acute onset, from at least two of the following seven categories:
b. Emotional lability and/or depression
c. Irritability, aggression and/or severely oppositional behaviours
d. Behavioural (developmental) regression
e. Deterioration in school performance
f. Sensory or motor abnormalities
g. Somatic signs and symptoms, including sleep disturbances, enuresis or urinary frequency
3. Symptoms are not better explained by a known neurologic or medical disorder, such as Sydenham’s chorea, systemic lupus erythematosus, Tourette syndrome or others. Note that the diagnostic work-up of patients suspected of PANS must be comprehensive enough to rule out these and other relevant disorders. The nature of the co-occurring symptoms will dictate the necessary assessments, which may include MRI scan, lumbar puncture, electroencephalogram or other diagnostic tests.
The researchers strongly emphasised the point that other known neurological and medical conditions must first be eliminated, e.g. autoimmune encephalitis, systemic autoimmune disease, metabolic diseases, epilepsy. In order to differentiate the condition from OCD and other psychiatric conditions like anxiety disorder, depression/bipolar disorder, Tourette syndrome, trauma/stress syndrome (which might also have quite acute onset), it was established that the PANS diagnosis should be limited to cases with acute onset of symptoms from multiple domains (Chang et al. 2015, Swedo et al. 2017). Several PANS/PANDAS cohorts have recently also been described in Sweden (Hesselmark et al. 2017, Gromark et al. 2019, Johnson et al. 2019).