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Even with a helmet, a bike crash can harm a cyclist’s brain

Man helping child put on a bicycle helmet

Bicycle helmets are an essential safety measure, significantly reducing the risk of head injuries during a bicycle crash. However, helmets are not perfect and cannot guarantee protection against brain damage in case of a bike crash. Even with the added protection of a helmet, cyclists remain vulnerable to severe head injuries.

Helmets are designed to absorb and distribute the impact forces that result from a collision. While they can effectively mitigate certain types of head injuries, they have limitations in preventing all potential brain trauma.


Rotational Forces

One of the significant challenges in helmet design is addressing rotational forces during a crash. When a cyclist’s head experiences a sudden impact, it may undergo rotational forces, causing the brain to move within the skull. This rotational motion can lead to “diffuse axonal injuries.” This injury occurs when nerve fibers in the brain become stretched and damaged.


Unfortunately, helmets alone cannot adequately address these rotational forces, leaving the brain susceptible to injuries even if the skull remains intact.

Acceleration and Deceleration

The brain’s soft, gel-like consistency makes it vulnerable to injury during sudden acceleration and deceleration. During a bicycle accident, the head often comes to an abrupt stop upon impact, while the brain continues moving within the skull. This difference in motion can cause the brain to strike the inner walls of the skull, resulting in contusions and bruising. Despite a helmet’s cushioning, it cannot entirely prevent the brain from experiencing these harmful forces.

Multi-Impact Scenarios

Many bicycle crashes involve multiple impacts — such as hitting the ground, then colliding with other objects or being struck by a vehicle. Designers create helmets to provide a single-use protection system. In other words, a helmet’s effectiveness can be significantly reduced after one bicycle accident. This is why you might have been told to get rid of your helmet after a bike accident, even if it looks fine.

When there are multiple impacts in the same collision, the helmet’s energy-absorbing capabilities might become compromised, leaving the cyclist’s brain vulnerable to injury.

Angular Impact and Helmet Coverage

The coverage area of helmets plays a crucial role in protecting the cyclist’s brain. However, they might not fully cover the temporal regions of the head, which are susceptible to angular impacts. Angular impacts occur when a collision strikes the head at an angle, leading to rotational forces that can be especially detrimental to brain tissue. Helmets might not adequately address this aspect, exposing parts of the head to potential harm.


Bicycle helmets can and do save lives, and reduce injury severity. However, the brain is both fragile and complex. Significant injuries or death can occur even if a bicyclist is wearing a helmet.

Brain injury symptoms can appear immediately after a collision or develop in the days or weeks after a crash. Brain injury symptoms can include the following:

  • Headaches
  • Cognitive difficulties involving concentration and memory
  • Speech and comprehension difficulties
  • Sensory deficits involving touch, temperature variations, posture and coordination
  • Double vision, blurred vision, impaired depth perception
  • Loss of control of the bladder and bowel
  • Emotional instability

If you experience brain injury symptoms after a bicycle accident — whether or not you were wearing a helmet at the time of the crash — you should contact an experienced bicycle accident attorney at Bay Area Bicycle Law, P.C. to discuss your case.