A concussion is a mild traumatic brain injury that results from a blow or jolt to the head or body, causing the brain to move rapidly inside the skull. This sudden movement temporarily disrupts normal brain function, leading to symptoms like headache, dizziness, or confusion. The medical understanding of this injury, which is characterized by functional disturbance rather than structural damage, has a remarkably long history. Tracing the recognition of this specific type of head trauma requires looking back thousands of years.
Ancient Recognition and Early Descriptions
The earliest documented observations of head injuries that align with modern concussion descriptions date back to ancient medical texts. Physicians in ancient Greece and Rome systematically documented the effects of trauma on the brain, particularly in military and athletic contexts. The writings of Hippocrates (circa 460–370 BCE) provide a foundational text, “On Injuries of the Head,” detailing a methodical approach to cranial trauma.
Hippocrates noted that a severe blow to the head could result in symptoms like temporary confusion, vomiting, or loss of speech, even without a visible skull fracture or open wound. He focused heavily on prognosis and clinical examination, using these transient functional symptoms as diagnostic indicators.
The primary focus during this time was distinguishing between a head injury that caused visible skull damage, and one that resulted only in temporary functional impairment. Practitioners were describing the effects of a concussion, recognizing a pattern of symptoms that resolved quickly. This early recognition was limited to symptomatic observation, lacking any true pathological definition of the injury itself.
The Formalization of “Concussion” as a Distinct Injury
The medical concept of a concussion began to separate formally from general head injury in the medieval period. The Persian physician Rhazes (Abu Bakr Muhammad ibn Zakariya al-Razi) is credited in the 10th century with providing the first clear recognition of concussion as a distinct condition. He defined it as a transient loss of function that occurred without any immediate, visible physical damage to the brain tissue.
This idea was subsequently expanded by European physicians. Lanfrancus of Milan in the 13th century used the Latin term commotio cerebri, meaning “shaking of the brain.” Lanfrancus specifically described this as a temporary loss of function caused by the brain being shaken, emphasizing the transient nature of the symptoms. By the 14th century, Guy de Chauliac further distinguished commotio cerebri from more severe injuries, noting its relatively good prognosis compared to skull fractures or contusions.
The 17th through 19th centuries saw physicians continue to refine the distinction, moving away from the idea that a concussion was caused by simple “shaking” to a more physiological understanding. In the 19th century, French surgeon Guillaume Dupuytren helped solidify the difference between unconsciousness caused by contusio cerebri (a bruised brain with small hemorrhages) and that caused by a pure commotio cerebri (concussion) where no gross structural damage was present. This process established the definition that persisted for centuries: a concussion was an injury characterized by functional symptoms but not by macroscopic structural lesions.
Evolving Understanding in the 20th and 21st Centuries
The understanding of concussion shifted significantly in the 20th century, moving from a purely functional problem to one with a recognized neurobiological basis. Research began to investigate the lasting consequences of repetitive head trauma. In 1928, physician Harrison Martland first described a progressive neurological deterioration in boxers, coining the term “punch drunk” syndrome to describe the chronic cognitive and physical symptoms.
By the mid-20th century, animal experiments and pathological studies revealed that concussion involved more than just a transient functional disruption. Researchers began to identify microscopic damage, specifically diffuse axonal injury (DAI), which involves the tearing of the brain’s long nerve fibers. This finding suggested that even mild trauma could cause subtle structural changes in the brain’s white matter.
The 21st century brought a focus on the cumulative effects of repeated mild trauma and the recognition of Chronic Traumatic Encephalopathy (CTE). This neurodegenerative disease is linked to repetitive head impacts and is characterized by the progressive accumulation of an abnormal protein called hyperphosphorylated tau within the brain. The recognition of CTE in former athletes has underscored that concussions and even subconcussive impacts can have long-term pathological consequences, radically changing the perception of the injury.