Diagnostic validity of electroencephalography in equine intracranial disorders.

This research article explores the reliability of electroencephalography (EEG) as a tool for diagnosing brain diseases in horses. The researchers found that EEG is a sensitive tool for such diagnoses, with abnormal results generally correlating with physical abnormalities found through subsequent necropsies.

Research Design and Participants

In this study, the diagnostic accuracy of EEG was tested in 20 horses that were investigated for symptoms such as seizures, abnormal behavior, or collapse from 1984 to 1997. These horses underwent clinical, clinicopathologic, and histopathologic exams, the results of which were compared with EEG findings. Another 10 horses, all of which presented with issues not related to brain diseases, were also used for validation purposes.

Recording and Analysis of EEGs

• The EEGs were recorded using two types of montage including bipolar left-to-right, back-to-front montage and a bipolar circular montage.
• Four of the horses were sedated while the remaining 16 were anesthetized during the EEG recording process.
• The recorded EEGs were subsequently analyzed visually and through semiquantitative masked analysis.

Findings

• Out of the 20 clinically affected horses, 7 showed normal EEG patterns while the remaining 13 exhibited abnormal EEG patterns. Abnormal patterns consisted of high-voltage slow waves or sudden onset (paroxysmal) activity either with or without generalized activity.
• The subsequent post-mortem examinations revealed a range of pathologies including meningoencephalitis, neuronal necrosis, congenital anomalies, cerebral edema, and abscess.
• All horses with these conditions showed abnormal EEG patterns, showing a strong sensitivity of EEG for detecting brain diseases in horses.
• However, in terms of localization, the area of the brain in which the EEG abnormalities and histopathologic abnormalities were detected did not correlate in 15% (3/20) of the cases.
• In 10 horses, the cause of neurologic signs could not be explained through post-mortem examinations. Of these, 7 had normal EEG patterns, translating to a specificity of 70%.

Conclusion

The study concludes that EEG is a sensitive diagnostic tool for detecting intracranial disorders in horses. However, there may not always be a direct correlation between the location of EEG abnormalities and histopathologic abnormalities.