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Unreactive EEG: pattern in locked-in syndrome.
1Department of Medicine, Palmetto General Hospital, Florida.
Clinical EEG (Electroencephalography)
|January 1, 1990
Summary
Locked-in syndrome (LIS) is a rare condition resulting from brainstem strokes. Unreactive alpha rhythms on EEG, typically indicating a vegetative state, were observed in conscious LIS patients, challenging diagnostic assumptions.
Area of Science:
- Neuroscience
- Neurology
- Clinical Electrophysiology
Background:
- Locked-in syndrome (LIS) is characterized by complete paralysis with preserved consciousness, typically caused by brainstem lesions.
- Diagnosing consciousness in LIS patients is challenging, often relying on limited motor responses.
- Electroencephalography (EEG) patterns, such as unreactive alpha rhythms, are traditionally associated with vegetative states and lack of consciousness.
Observation:
- Three patients with acute brainstem strokes presenting with LIS were studied.
- Repeated EEG recordings in these conscious LIS patients revealed an "alpha coma" pattern.
- This pattern included an unreactive alpha rhythm despite multimodal stimuli.
Findings:
- The presence of an unreactive alpha rhythm on EEG does not necessarily indicate a vegetative state or absence of consciousness in LIS.
- This EEG pattern can be misleading in patients with brainstem lesions and preserved awareness.
- The study challenges the conventional interpretation of unreactive alpha rhythms in unresponsive patients.
Implications:
- Accurate diagnosis of LIS is crucial to avoid abandoning communication efforts with affected individuals.
- Relying solely on EEG unreactive alpha rhythms can lead to misdiagnosis and neglect of conscious patients.
- This research highlights the need for revised diagnostic criteria for consciousness in LIS, emphasizing that alpha reactivity is not a definitive marker of consciousness.