If You Hit Your Head, Watch Out For These Symptoms... Even Days Later

When I tripped over my daughter’s bathroom stool and hit my head on the bathtub, I thought it was harmless. I didn’t lose consciousness or even have a bump on my head.

It wasn’t until hours later that I started feeling fatigued and a bit off. A few days later, I thought I felt back to normal until I tried to work on my laptop — and the world started spinning. A pounding headache and intense brain fog followed, and then I knew I was dealing with a concussion.

“Many people who experience a concussion don’t actually feel any of the symptoms until hours later,” explained Dr. Daniel Daneshvar, the chief of Spaulding’s brain injury rehabilitation program and co-director of the Sports Concussion Clinic at Mass General Brigham in Massachusetts. 

Additionally, symptoms can “intensify or evolve over the first several days,” added Dr. Kevin Bickart, an assistant professor in neurology at the David Geffen School of Medicine at the University of California, Los Angeles.

Because of this, the criteria for diagnosing a concussion now include symptoms that appear within a 72-hour window, according to the 2023 American Congress of Rehabilitation Medicine.

While many know to pay attention to symptoms right after a head injury, it’s often overlooked to watch for those that may appear hours, days or even weeks later. And because head injuries are common and can be debilitating, it’s important to know what to look for and when you need to seek help.

We talked to neurologists and concussion experts about these unexpected delayed symptoms, why they may not appear right away and what it means if you’re experiencing them. 

First of all, what is a concussion exactly?

A concussion is a brain injury that’s “caused when the cells in the brain, the neurones, stretch or get otherwise damaged,” explained Daneshvar. “What happens then is the cells that are normally well-regulated in sending messages …  [to] one another start sending messages erratically and in an uncontrolled fashion.”

These brain cells start using way more energy than they receive, and this “energy crisis” causes symptoms to appear, he said.

Concussion symptoms can really vary because this is “happening in the brain that controls everything from balance [and] headache[s] [to] vision, mood [and] memory,” added Dr. Shae Datta, a neurologist and co-director of the NYU Langone Concussion Center. 

These changes in the brain are microscopic and often don’t appear in imaging like a CT or MRI scan, she said. Imaging only detects larger structural issues, like a brain bleed, significant swelling or skull fracture. So identifying symptoms is a key part of diagnosing a concussion.

What signs or symptoms should you watch for after you hit your head, even hours or days later?

One of the first signs people often look for after hitting their heads are bumps, bruises or other marks of injury. But this doesn’t necessarily mean you have a concussion.

“There isn’t a great connection between what you see on the outside of the skull and what’s going on inside,” Daneshvar noted. 

While every individual is different, usually in the first 24 hours after a concussion you may experience more physical symptoms, like dizziness, headaches, nausea and sensitivity to light and noise, Bickart said. About three to seven days later, cognitive and emotional symptoms may pop up, such as anxiety, irritability, trouble focusing, memory issues and brain fog. 

“This ‘second wave’ often catches patients off guard because they thought they were recovering,” he explained.

That said, every brain injury is unique, so any of these symptoms could appear immediately or later on, Datta added.

For example, “it doesn’t always happen that no irritability occurs immediately,” Bickart said. “Some people after a concussion can become completely emotionally dysregulated in the moment … crying hysterically … It’s not the most common thing that occurs, but it can.”

Symptoms can also transform over time. For instance, the pain of headaches (the most common concussion symptom) may feel different days or weeks later. Initially, it might feel like “pressure and pounding” all over the head and then eventually be “more intermittent … and only on one side,” he explained.

Disruptions in your sleep-wake cycles may change from feeling like you need to sleep more to actually having insomnia later on, Bickart said. 

Vision issues could also evolve and include blurred or double vision or difficulties with focusing the eyes and tracking objects, according to the American Academy of Ophthalmology.

Why can symptoms appear delayed? 

“Immediately after a hit, the brain dumps adrenaline and burns [energy] rapidly … which can mask symptoms,” Bickart said. “It is only hours or days later, when the brain’s energy fuel … is depleted” that symptoms may become more apparent.

Especially if the injury happens in a sports environment, it may not be “until the adrenaline wears off that you start to notice, ‘Hey, I’m feeling kind of tired actually’ or ’I’m having trouble concentrating,” Daneshvar explained.

Additionally, damage from the injury can lead to inflammation in the brain and affect different cells, he said.

Inflammation “often doesn’t peak until three to seven days post-injury,” Bickart said. This is what can “drive that ‘second wave’ of brain fog and fatigue.”

Lastly, as an individual returns to work, school or other everyday demands after resting, they may observe new symptoms “because they [haven’t] exposed … or pushed themselves” in this way yet.

What should you do if you experience delayed symptoms? 

“Just because the symptoms are delayed, it doesn’t [necessarily] mean something catastrophic is going on,” Daneshvar said. “The important thing to note is … if symptoms are worsening rather than improving … or if … [there are] red flag symptoms.”

Red flags that you should go to the emergency room include a worsening headache, increased confusion, repeated vomiting, losing consciousness for more than 30 seconds, blood or fluid coming from the ears or nose, changes in your vision, constant ringing in the ears, weakness, seizures, difficulty speaking and large head bumps and bruises, according to Mayo Clinic. 

If you experience delayed symptoms (after 48 hours) that don’t require emergency care, reach out to your primary care doctor and they can help you decide if a referral to a neurologist or imaging is necessary, advised Dr. Dharti Dua, a neurologist at The Ohio State University Wexner Medical Center.

You also want to get adequate rest and be careful not to get another concussion soon after because this makes you “more prone to a delayed recovery,” she said.

“If symptoms appear days later, stop the activity that triggered them, but do not retreat to a dark room for days,” Bickart said. “We now know that strict rest beyond 48 hours actually prolongs symptoms.”

For symptoms that last beyond two weeks, active treatments are recommended, he added. For example, vestibular rehabilitation therapy treats dizziness and balance issues, and cognitive therapy teaches strategies for managing brain fog.

Datta advises looking for concussion centres because they specialise in brain injuries and offer a multidisciplinary team.

“It takes more than one kind of doctor to diagnose and manage you,” she explained. 

These centres often include concussion experts from neurologists to physical therapists to neuro-ophthalmologists.

“The hopeful sentiment is that a concussion is very treatable. Most people recover pretty quickly, within a week or two,” Bickart said. For those who may have delayed or longer lasting symptoms, “there are tons of treatments out there … [and] you can still get the right help and recover.”