Abstracts

Rationale: The study investigated the diagnostic utility and yield of a routine electroencephalogram (EEG) study to help clarify the clinical presentation in patients admitted to the psychiatry inpatient service of our hospital. Methods: All routine adult EEG from the inpatient psychiatric service over a 3-year period (7/2009-7/2012) were reviewed for the presence of epileptiform abnormalities (sharp waves or spike wave discharges), diffuse or focal slowing and other non-diagnostic abnormalities such as diffuse excess of fast activity. Medical records of patients who underwent EEG studies were reviewed to determine if the EEG changed the management plan. Neuroimaging studies if available were correlated to the EEG findings. Results: A total of 98 patients yielded 104 routine EEGs. The reported diagnoses were as follows: 21 EEG requisition diagnoses with depression, 21 with bipolar disorder, 31 with psychosis NOS, 9 with schizophrenia, 6 with schizoaffective disorder, 1 with generalized anxiety disorder, 3 with schizophreniform disorder, 3 with dementia NOS, 8 with mood disorder NOS and 1 with alcohol/cannabis-induced pychosis. There were 67 (64%) normal routine EEGs and 37 (36%) abnormal routine EEGs (12 in patients < 40 and 25 in patient >40 years of age). Among those 37 abnormal studies, 29 had diffuse dysfunction and 8 had focal dysfunction. Only 3 studies with abnormal EEGs had epileptiform abnormalities. Depression (8 studies with diffuse dysfunction, 0 with focal dysfunction, 13 normal) ; bipolar disorder (4 studies with diffuse dysfunction, 2 with focal dysfunction, 15 normal); psychosis NOS (8 studies with diffuse dysfunction, 4 with focal dysfunction, 19 normal); schizophrenia (2 studies with diffuse dysfunction, 0 focal dysfunction, 7 normal); schizoaffective disorder (1 study with diffuse dysfunction, 0 focal dysfunction, 5 normal); generalized anxiety disorder (0 pwith diffuse dysfunction, 0 focal dysfunction, 1 normal); schizophreniform disorder (2 studies with diffuse dysfunction, 0 focal dysfunction, 1 normal); dementia NOS (1 study with diffuse dysfunction, 1 focal dysfunction, 1 normal); mood disorder NOS (4 studies with diffuse dysfunction, 0 focal dysfunction, 4 normal); alcohol/cannabis induced psychosis (0 with diffuse dysfunction, 0 focal dysfunction, 1 normal). Three patients who had focal EEG abnormalities had a corresponding focal imaging abnormality. Conclusions: Routine EEG studies are mostly normal in patients admitted to the in-patient psychiatry service in whom a seizure disorder is listed as the requisition diagnosis. The routine use of EEG in psychiatric patients to make or refute a diagnosis of epilepsy should be discouraged.