Clinical Correlates of Frontal Intermittent Rhythmic Delta Activity Without Structural Brain Lesion

Frontal intermittent rhythmic delta activity (FIRDA), rhythmic slow wave pattern lasting several seconds over the anterior leads of electroencephalography (EEG), has been reported in a wide variety of clinical conditions. We investigated the clinical significance of FIRDA without structural brain lesions. We reviewed 7689 EEGs between October 2017 and September 2019 at a university hospital. Patients (age >18 years) who were confirmed to have "nonsignificant neuroimaging" were examined. Clinical data were retrospectively collected, and the estimated cause was carefully decided. We found 83 FIRDA among 7689 EEGs (1.08%). After patients with any structural lesion identified on neuroimaging were excluded, 37 FIRDAs were reviewed. There were 20 (51.35%) patients of metabolic encephalopathy. Six patients showed FIRDA due to neurodegenerative disease (16.21%). In addition, we found 6 (16.21%) of neurodegenerative disease and 5 (13.51%) of hypoxic encephalopathy (cardiac arrest). Four (16.21%) patients were related to systemic infection (10.81%), whereas 2 were related to encephalitis (5.40%). We demonstrated several potential etiologies, including metabolic encephalopathy, neurodegenerative disease, hypoxic encephalopathy, and infections, which should be considered in the case of FIRDA without structural brain lesions.

Frontal Intermittent Rhythmic Delta Activity (FIRDA) in the Neurological Intensive Care: Prevalence, Determinants, and Clinical Significance

INTRODUCTION

Frontal intermittent rhythmic delta activity (FIRDA), a transient rhythmic slow wave pattern over the anterior EEG leads, has been reported in a wide variety of cerebral lesions and different metabolic disturbances. Few authors have analyzed the frequency and clinical significance of FIRDA in the critical care setting. We aimed to better understand these issues in our intensive care cohort and if possible, try to delineate its underlying mechanisms.

METHODS

Video-EEG reports of consecutive adult patients in the neurological intensive care unit (NICU) since 2009 were retrospectively reviewed to identify cases with FIRDA. Demographic, clinical, and laboratory data were obtained from EEG reports and patient charts. Age- and sex-matched patients with acute stroke, hospitalized in NICU and no FIRDA on video-EEG monitoring served as the control group.

RESULTS

Among 162 patients who underwent video-EEG monitoring, FIRDA was documented in 17%. Female prevalence was 50% and age ranged from 23 to 82 years. Twenty-three (82%) of patients with FIRDA had a diagnosis of stroke. Comparison of demographic characteristics, EEG findings, metabolic disturbances and prognoses revealed no differences between stroke cases with and without FIRDA, except for higher frequency of acute and chronic isolated posterior circulation infarcts in patients with FIRDA.

CONCLUSION

FIRDA is more commonly encountered in the neurocritical care setting as compared with outpatient EEG clinics. Our findings in stroke patients indicate that involved vascular territories may be related to the generation of FIRDA.

Creutzfeldt-Jakob-Like Syndrome due to Hypercalcemic Encephalopathy

Hypercalcemia can cause a subacute syndrome of progressive dementia and marked changes in the electroencephalogram (EEG). We report a case of iatrogenic hypercalcemia with a close correlation between the clinical course and the EEG changes. A 73-year-old woman presented with a subacute syndrome of progressive dementia and bursts of 1.5 to 2 Hz intermittent rhythmic delta activity superimposed on a low-voltage background activity in the EEG. Clinical and EEG abnormalities rapidly resolved after normalization of serum calcium levels. As part of the diagnostic workup of a subacute progressive dementia, a serum calcium level and an EEG should be obtained to detect a Creutzfeldt-Jakob like syndrome in hypercalcemia. Unlike in Creutzfeldt-Jakob disease, and Creutzfeldt-Jakob-like syndrome induced by lithium intoxication, there are rarely myoclonic jerks and periodic discharges in hypercalcemic encephalopathy.