Diagnostic validity of electroencephalography in equine intracranial disorders

Electroencephalography (EEG) is a valuable diagnostic test to identify func tional disturbances in brain activity. The purpose of this study was to ass ess the validity of EEG as a diagnostic indicator of intracranial diseases in horses. The validity of EEG was estimated by comparing clinical, clinico pathologic, and histopathologic findings to EEG findings in 20 horses exami ned for seizures, collapse, or abnormal behavior between 1984 and 1997. A b ipolar left-to-right, back-to-front montage and a bipolar circular montage were recorded from sedated (4) and anesthetized (16) horses. Visual and sem iquantitative masked analysis of EEG recording Ist was validated on 10 hors es presented for problems other than intracranial diseases. EEG pattern was normal in 7 of the 20 clinically affected horses. Abnormal EEG patterns in cluded high-voltage slow waves and discrete paroxysmal activity with or wit hout generalized activity in 13 horses. Histopathologic diagnoses in 10 hor ses included meningoencephalitis, neuronal necrosis, congenital anomalies, cerebral edema, and abscess. All of these horses had abnormal EEG patterns (sensitivity, 100%) with a positive neuroanatomic correlation in 7 animals. Localization of histopathologic and EEG abnormalities did not correlate in 15% of the horses (3/20). The cause of neurologic signs could not be expla ined at postmortem examination in 10 animals and, the EEG pattern was norma l in 7 of these horses (specificity, 70%). In conclusion, equine EEG was a sensitive tool in the diagnosis of intracranial disorders.