What is Post-Concussive Photophobia?
Post-Concussive Photophobia
Photophobia is discomfort or pain caused by light. It is a common neurological and vision symptom. The most common cause of photophobia is migraine, but other headache disorders and problems in the brain’s visual pathways can also cause it. Photophobia can be hard to treat, and the pain it causes can be debilitating.
Photophobia is also a common symptom of post-concussion syndrome, and it’s one we see often in our practice (1).
Light sensitivity can sometimes signal a medical emergency. Get emergency care right away for light sensitivity with fever, a stiff neck or a severe headache, or with eye pain, redness or sudden vision changes. After a head injury, get emergency care for a headache that keeps getting worse, repeated vomiting, confusion, slurred speech, weakness or a seizure.
How Common Is Post-Concussive Photophobia?
An estimated 1.8 to 3.8 million concussions happen each year in the U.S., and the true number is likely higher because many go unreported. About 39 million people in the U.S. live with migraine (2). Photophobia isn’t usually tracked on its own, but these numbers suggest it is very common.
In post-concussion syndrome, women tend to be more sensitive to sensory input of many kinds, including light (3). Photophobia is also very common in people who have both post-concussion syndrome and post-traumatic stress disorder (4).
What Causes Post-Concussive Photophobia?
Photophobia is often caused by problems in the front of the eye, such as dry eyes or inflammation inside the eye (iritis or uveitis). These are usually treated by an eye care provider with eye drops or medications, so it’s important to have an eye exam if you develop light sensitivity.
In other cases, photophobia involves the nervous system pathways that control the size of your pupils (5). The pupil is the black center of the eye. It gets bigger (dilates) or smaller (constricts) depending on how much light is around you, so you can see well in both bright and dim settings.
Pupil size is controlled by the autonomic nervous system, which runs the body’s automatic functions, such as heart rate, blood pressure, breathing and digestion. It has two branches: the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system helps you respond quickly to threats. It drives the “fight or flight” response, raising your heart rate and breathing rate, slowing digestion and widening your pupils to take in more of your surroundings. It can switch on during real danger, a stressful day at work or while you’re stuck in traffic on the way to the airport.
The parasympathetic nervous system handles everyday functions during calm moments. It’s often called the “rest and digest” system. It keeps your heart rate and breathing steady, keeps your pupils appropriately small and supports digestion.
The balance between these two systems is often disrupted by concussions and other brain injuries. The brainstem areas that control them are vulnerable to the twisting and shearing forces of a concussion. Too much sympathetic activity and too little parasympathetic activity may contribute to photophobia (5).
What Are the Symptoms of Post-Concussive Photophobia?
The main symptom of post-concussive photophobia is sensitivity to light, which ranges from mild to severe. Bright light may bring on nausea and vomiting, or trigger headaches or migraines. Many people also feel tired and foggy, and some notice sweating or a pounding heartbeat. Photophobia often comes with phonophobia, or sensitivity to sound.
What Happens in the Brain With Photophobia?
The pathway that widens your pupils is a three-neuron chain driven by the sympathetic nervous system. It starts in the hypothalamus, a deep brain area closely tied to emotions, which may be one reason stress and strong emotions can make light sensitivity worse. The first neuron travels down through the brainstem to the upper part of the spinal cord, between the C8 and T2 levels, to a group of nerve cells called the ciliospinal center of Budge. The second neuron leaves the spinal cord, travels up through the chest past the top of the lung, and reaches the superior cervical ganglion, high in the neck near the angle of the jaw. The third neuron travels along the blood vessels of the neck into the skull and eye socket, where it reaches the dilator pupillae muscle that widens the pupil (6).
As you can see, a simple change in pupil size depends on a complicated pathway. Injuries to the brain or the neck can disrupt it at many points.
One of the most common features of migraine is multisensory dysfunction, meaning increased sensitivity to sights, sounds and smells. These can become so intense that they’re painful, a problem called sensory allodynia. These changes have been traced to abnormal processing in several areas of the cortex, including the visual cortex, but recent research suggests they may also start lower in the visual pathways, including in the brainstem (7).
One of these lower areas is the trigeminovascular system. Migraine is linked to a brainstem-level inability to suppress glare and light-induced pain, and the trigeminal nerve, which carries pain signals from the blood vessels around the brain, appears to be involved. The trigeminal system also drives reflexes that widen blood vessels that are already sensitive to pain, which can add to the pain (8).
Photophobia is less common in other types of headache but has been reported in tension-type headache, headaches after a brain injury, and on one side in cervicogenic and cluster headaches. All of these involve the trigeminal system (9).
Photophobia also involves special light-sensing cells in the retina, called intrinsically photosensitive retinal ganglion cells (ipRGCs). Activation of these cells has been linked to photophobia during migraine (10).
Animal studies have shown that shining light into the eye strongly increases the activity of pain-sensing nerve cells in the thalamus that also receive signals from the coverings of the brain. These cells receive input from ipRGCs and send signals to areas of the cortex that handle touch, pain and vision. This may help explain how light can make headache pain worse during a migraine (11).
There is also solid evidence that the pupil’s light reflex, which is controlled by autonomic circuits in the midbrain, works differently in people with migraine (12). One study measured the pupillary light reflex and light sensitivity in people with migraine and in healthy people. People with migraine who had an abnormal pupil reflex were more sensitive to light between headaches, and the abnormality was linked to migraine severity. The researchers concluded that the abnormal reflex comes from the brain and reflects the autonomic nervous system adapting poorly to chronic light sensitivity (13).
The Inner Ear, Blood Pressure and Light Sensitivity
Many other systems that can be injured in a concussion feed into the sympathetic nervous system, and an important one is the vestibular system of the inner ear (14). When you go from lying down to standing, gravity pulls blood toward your feet. Your body senses this through pressure sensors in the arteries of the neck and chest and through your inner ear, which tells your brain where your head is relative to gravity. Through a reflex called the vestibulosympathetic reflex, the inner ear signals blood pressure centers in the brainstem very quickly, before blood pressure has a chance to fall, so enough blood keeps reaching your brain when you change position (15).
To keep blood flowing to the brain, the body activates the sympathetic nervous system, which tightens blood vessels and speeds up the heart. The vestibular system can be injured in a concussion, which may disrupt these reflexes. This is one way post-concussive dysautonomia can develop.
In some types of dysautonomia, the heart rate rises much more than normal. A very fast heart rate may give the heart less time to fill between beats, which can reduce blood flow to the brain even more. Some people feel dizzy or faint and may be injured in falls. Others have constant headaches, migraines, brain fog, light and sound sensitivity or lightheadedness. Research also suggests that ongoing strain on the sympathetic nervous system may affect organs such as the heart and kidneys over time (16).
When the brain doesn’t get enough blood flow, many symptoms can appear. Your brain uses a great deal of energy, and when its supply is disrupted, many brain functions can be affected. Simple thinking tasks can feel like huge challenges, and simple physical tasks can be exhausting. Managing emotions can become very difficult. Nearly everything your brain does depends on steady blood flow, so when that system struggles, almost everything can feel like a struggle (17).
How Is Photophobia Usually Treated?
There is no established cure for post-concussive photophobia. Many people get relief by wearing sunglasses or hats to block light. Some use glasses with special tinted lenses that filter out the wavelengths of light that bother them most (18).
How the NeuroRescue Program Can Help
Our care is designed to work alongside your physician, eye care provider and other providers, never in place of them. Please don’t change or stop any medication without talking with your prescriber.
One of the brain’s most important jobs is figuring out where you are in the world. It uses your inner ear to sense where your head is in relation to gravity and how it’s moving, your muscles and joints to sense where your body is and what it’s doing, and your eyes to sense where you are in relation to everything around you. Your brain combines all of this into a picture of where you are, so you can respond to the world around you.
Your brain organizes this information as a set of maps: a vestibular map from your inner ear, a body map from your muscles and joints, a visual map from your eyes, and others. These maps need to agree with each other about where you are.
After a concussion, these maps may not match. Your eyes, inner ear and body may be sending different messages about where your head is in relation to gravity. When you go from lying down to sitting or standing, mismatched signals may make it harder for your brain to adjust blood flow to your head (19). One theory is that this ongoing mismatch keeps the brain’s stress pathways more active, which may contribute to wider pupils and light sensitivity. Eye movement exercises can activate brain and brainstem areas involved in autonomic control (20).
Our approach is to carefully evaluate and work on the pathways affected by your concussion, with the goal of reducing your sensitivity to light.
Depending on your needs and test results, your program may include eye exercises to improve gaze stability (21) and the accuracy of your eye movements (22); exercises for reflexes involving your inner ear, neck or both (23); balance training under specific conditions and vision training that combines several types of input at once (24); electrical stimulation (25); and exercises in a virtual reality environment (26). Transcranial magnetic stimulation (TMS) has been studied for symptoms after brain injury (27). At our clinic, TMS is provided by our psychiatric mental health nurse practitioner, who will evaluate whether it may be appropriate for you.
Studies of approaches that combine several of these therapies after brain injury have reported improvements in symptoms, in some cases lasting over time (28, 29, 30). No two concussions are alike, and the therapies we recommend are always chosen based on your history, testing and exam findings.
How the NeuroRescue Program Works
Your NeuroRescue Program begins with your Discovery Day. We start with a detailed history of your condition and your life on a timeline. This helps us understand the factors that may have contributed to where you are now, and identify related conditions that may be making it harder to move forward.
We measure how your visual, vestibular and balance systems are working through computerized analysis of your eye movements, inner ear reflexes and balance under different conditions. Our testing includes videonystagmography and saccadometry to measure several types of eye movements, the video head impulse test to measure how each semicircular canal is working, and CAPS computerized posturography to assess your balance under different sensory conditions. We also use NeuroSensoryMotor Integration testing to evaluate hand-eye coordination and cognition, and Virtualis testing to assess dynamic eye tracking and your perception of vertical in a virtual reality environment.
We combine this with a thorough physical and neurological exam of your sensory, motor, autonomic and cognitive systems, including a passive tilt table test to check for dysautonomia. We also review any relevant lab work, imaging and prior testing, and integrate it with our findings.
Together, this helps us understand which parts of your nervous system are working well, which are struggling, and how quickly they tire. We use that information to design your personal NeuroRescue Program, aimed at improving function in the systems that need support and helping them work together. Our testing also helps us decide when to push and when to let you rest.
Our goal is to help you step outside, look at a screen or walk into a brightly lit store without bracing for the pain.
Your Next Step
Living with light sensitivity after a concussion can shrink your world, keeping you indoors, behind sunglasses and away from the things you enjoy. You don’t have to keep living in the dark. To find out if the NeuroRescue Program is right for you, contact one of our patient care coordinators to schedule your Discovery Day.
It’s never too late to take the next step.
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