The neurophysiology of concussion

Area of Science:

• Neuroscience
• Traumatic Brain Injury Research
• Neurophysiology

Background:

• Cerebral concussion is the most frequent yet least understood form of traumatic brain injury (TBI).
• Characterized by head acceleration/deceleration, it causes brief consciousness impairment, reflex paralysis, and memory loss.
• Neurophysiological recordings, including electroencephalograms (EEG) and sensory evoked potentials (EPs), are crucial for studying acute concussion pathophysiology.

Purpose of the Study:

• Critically review neurophysiological studies on concussion over the past 50 years.
• Assess prominent concussion theories, including vascular, reticular, centripetal, pontine cholinergic, and convulsive hypotheses.
• Determine the most viable explanation for concussion based on neurophysiological data.

Main Methods:

• Review of experimental animal studies recording EEG and EPs following head trauma.
• Critical evaluation of methodological limitations in existing research (e.g., anesthesia, multiple impacts, recording delays).
• Synthesis and assessment of evidence supporting five major concussion theories.

Main Results:

• Immediate post-concussive EEG exhibits excitatory or epileptiform activity.
• Cortical EP waveforms are completely lost during the acute post-concussive period.
• Neurophysiological data (EEG and EPs) following concussion closely resemble those of generalized seizure activity (GSA).

Conclusions:

• The convulsive theory provides the most viable explanation for concussion, positing shared pathobiological processes with generalized epileptic seizures.
• Concussion involves mechanically induced cortical deafferentation due to neuronal depolarization and synchronized discharge, not brainstem reticular activating system disruption.
• The convulsive theory adequately explains concussion symptoms, amnesia, autonomic disturbances, and post-concussion syndrome, offering insights into related TBI issues.