Evidence for a diagnostic distinction between functional seizures and functional motor symptoms from the TriNetX...

There is evidence that the two most common subtypes of functional neurological disorder, functional seizures (FSs) and functional motor symptoms (FMDs), have differences between them beyond symptom type, creating debate as to whether they may best be considered distinct disorders. However, most research has studied FS or FMD separately, and the few studies that have directly compared them have been relatively small. We used the large TriNetX electronic health database to see whether the differences previously identified would be confirmed in a larger sample of both subtypes.

All cases of FMD without FS were compared with cases of FS without FMD, extracted from the TriNetX electronic health records database. Previously identified between-group differences in demographics, comorbidity, and antecedents were compared between groups.

Over 120,000 cases of FMD and FS were extracted. They confirmed that people with FS were significantly younger and had a younger onset than those with FMD, were more likely to be Black and less likely to be Asian, and had higher rates of all comorbid mental health diagnoses, other than somatoform diagnoses, which were more common in FMD. The onset of FS was more commonly preceded by psychological injury, as measured by preceding depression or stress reactions.

The differences between FMD and FS previously identified in small studies were confirmed in this much larger dataset. They provide indirect support for differences in etiology and mechanism, which may in turn support a nosological distinction between FMD and FS.