EMG artifact in brain death electroencephalogram, is it a cry of "medullary death"?

ABSTRACT

The Uniform Determination of Death Act (UDDA) defines death as irreversible cessation of the functions of the entire brain including the brainstem. Many individuals meeting the clinical criteria of brain death can be documented to have some residual sub-cortical and brainstem function on careful testing. Determination of brain death still remains a persistently unresolved issue in health law and bioethics. The determination of brain death is clinical and involves testing for the integrity of brainstem functions. Documentation of irreversible cessation of brainstem functions when the cause of coma is established is usually sufficient to make a diagnosis of brain death. Confirmatory tests like four-vessel angiogram and electroencephalogram (EEG) are required in cases where the clinical testing is inconclusive or unreliable. EEG criteria for electrocerebral silence (ECS) is absence of any detectable cortical activity above 2 microV in a study performed as per the guidelines developed by the American Electroencephalographic Society. EEG studies carried out for ECS are at times contaminated by electromyographic (EMG) artifacts reflecting scalp motor unit activity. A secure EEG diagnosis of ECS cannot be made in such cases. What exactly is the relevance of scalp EMG activity in these clinically brain dead patients? What is the mechanism of generation of this spontaneous scalp EMG activity and how can the diagnosis of brain death be secured in these patients? These issues are explored in this article by highlighting a case.