Should I get an MRI after hitting my head?

Quick Answers

An MRI (magnetic resonance imaging) scan may be recommended after hitting your head to check for brain injury. Some reasons to get an MRI after head trauma include:

• You lost consciousness, even if just for a few seconds
• You are experiencing symptoms like headache, confusion, nausea, or changes in vision/hearing
• You have a history of concussions
• The head injury caused a dent or swelling in the skull
• You are on blood thinners or have a bleeding disorder

An MRI provides detailed images of the brain and can detect small amounts of bleeding or damage that a CT scan may miss. Most minor head bumps do not require imaging. Talk to your doctor about whether an MRI is necessary based on the severity of injury and your symptoms.

When to Get an MRI After Hitting Your Head

Hitting your head is quite common, and in most cases does not lead to serious injury. However, some head impacts can result in concussions or more dangerous forms of brain trauma. How do you know if your head injury warrants getting an MRI scan?

Here are some general guidelines on when an MRI is recommended after bumping your head:

• You lost consciousness, even briefly – Losing consciousness after a head injury, even for a few seconds or minutes, is a red flag for concussion or more severe brain injury. An MRI can look for bleeding, swelling, or damage to the brain.
• You’re experiencing concussion symptoms – If you have headache, nausea, dizziness, confusion, balance issues, ringing in the ears, or other possible concussion symptoms, an MRI can help diagnose the extent of injury.
• You suffered a moderate to severe head impact – The force of the blow matters. An MRI is more likely needed for direct hits to the head at high speed, versus just casually bumping your head on something.
• You have a history of concussions – Those with multiple past concussions are at higher risk of serious outcomes with another head injury. An MRI is often done given the concern for cumulative brain damage.
• The injury caused skull damage or swelling – If the head trauma resulted in a depressed area or raised swelling on the scalp, this indicates the impact was hard enough to potentially deform the skull and injure the brain. An MRI can investigate.
• You take blood thinners – Patients on blood thinners like warfarin are at higher bleeding risk after head injury. An MRI screens for bleeding complications.
• You have a bleeding disorder – Conditions like hemophilia put you at risk of continued bleeding in the brain after head trauma. MRI can detect blood accumulations.

Of course, these are just general guidelines and your doctor will make the final decision about ordering an MRI based on the unique circumstances of your injury. Don’t hesitate to ask your healthcare provider whether an MRI is recommended after any significant head trauma.

Are MRIs Necessary for Minor Head Bumps?

What if you just lightly bumped your head against a cabinet door or got hit in the head by a soccer ball? For minor head impacts, an MRI is usually unnecessary unless symptoms develop.

Getting an MRI after every single minor head bump would not be practical or supported by evidence. CT scans and MRIs have risks of their own, including radiation exposure from CT scans and contrast dye allergies from MRIs.

Doctors do not recommend imaging tests for head injuries that:

• Did not involve a direct blow to the head
• Did not cause you to lose consciousness
• Are not producing any symptoms of concussion
• Did not result in bleeding, clear fluid from the ears/nose, black eyes, swelling, or obvious skull damage
• Were at low speed (like casually bumping your head)

Of course, use judgment after any head injury. Seek emergency care if you experience:

• Prolonged loss of consciousness
• Vomiting or worsening headache
• Confusion, difficulty speaking or walking
• Bleeding from ears or clear fluid leaking from ears/nose
• Weakness or sensory changes
• Seizures

When in doubt, it’s best to get evaluated after a head injury. But an MRI is usually overkill for minor head bumps without symptoms.

MRI vs. CT Scan After Head Injury

When someone does require brain imaging after head trauma, doctors often debate using a CT scan vs. MRI. Which test is better at detecting traumatic brain injury?

MRIs have some advantages over CT scans:

• Better soft tissue contrast – MRI provides clearer images of brain tissue abnormalities, while CT is better for visualizing skull fractures.
• Can detect smaller bleeds – MRIs pick up evidence of small hemorrhages and micro-bleeds that a CT could miss.
• Avoid radiation – CT scans expose you to ionizing radiation, while MRI uses magnetic fields and radio waves.

However, CT scans have benefits including:

• Faster scan time – CT scans take just seconds versus an MRI which may take 30 minutes or more.
• Wider availability – Many smaller hospitals offer CT scanning but not MRI.
• Lower cost – CT scans are usually less expensive than MRIs.
• Calibrates blood flow – CT angiography looks at blood vessel flow to assess vascular injuries after head trauma.

In some cases, patients may get both a CT and an MRI to maximize detection of any brain injury. However, doctors won’t order unnecessary scans that don’t align with evidence-based guidelines.

Preparing for a Head MRI

Once your doctor determines an MRI is needed after head trauma, how should you prepare for the test? Here are some tips:

• Inform your doctor about implanted devices. MRIs can interact with medical implants like pacemakers, insulin pumps, or aneurysm clips.
• Follow MRI safety precautions. Remove metal jewelry or clothing containing metal snaps/zippers which can be attracted by the magnet.
• Expect to change into a hospital gown. Metal objects including belts and underwire bras must be removed.
• Combat anxiety or claustrophobia. MRIs involve lying still inside a tube which can be stressful. Ask for antianxiety medication if needed.
• Arrange transportation home. You cannot drive yourself after the scan if given sedation medication.
• Follow your facility’s specific instructions. For example, avoid eating for a period before the scan if needed for anesthesia.

Talk to your medical team if you have any concerns about managing pain, lying still, anxiety, or accessibility issues during your upcoming head MRI. They can provide assistance and adjustments to make the process smooth.

What Are Doctors Looking for With a Head MRI?

When reading your MRI results after head injury, radiologists will carefully assess for various types of brain abnormalities, including:

• Skull fractures – Fractures appear as bright white lines on the MRI. They occur most often in the bones around the sinuses and base of the skull.
• Hemorrhage or hematomas – Bleeding in the brain shows up as darker areas. Different types include epidural, subdural, intracerebral, and subarachnoid hemorrhages depending on the location.
• Contusions – Bruises to the brain tissue are darker on MRI. Contusions often develop right under the area of impact.
• Shearing injuries – Diffuse axonal injury from forceful movement of brain tissue appears as white matter lesions on MRI.
• Edema – Brain swelling shows up as lighter areas of fluid accumulation.
• Concussion – Doctors look for subtle inflammation, micobleeds, and neural connectivity changes indicating concussion.

Multiple views of the brain including axial, coronal, and sagittal planes are obtained. Radiologists also examine the brain stem, ventricles, orbits, sinuses, and soft tissues around the skull.

Let your doctor know if you have a history of prior head injuries, bleeding disorders, or other medical conditions as these provide important context when interpreting head MRI results.

What If the MRI Is Normal?

It’s reassuring but not completely surprising if your MRI comes back normal after a head injury. Here’s why a normal scan does not completely rule out concussion or other brain trauma:

• Injury detection limits – Even MRI cannot detect the most microscopic neural damage from concussions.
• Timing issues – Bleeding, swelling, and other abnormalities can take hours or days to become visible on MRI.
• Clinical correlation needed – Symptoms must be factored with imaging. The scan alone doesn’t diagnose concussion if symptoms are present.

So a normal MRI should not be interpreted as proof there is no injury whatsoever. Your doctor will still consider your symptoms, cognitive testing results, and clinical exam along with imaging.

You should follow recommended treatment and return precautions even if MRI is clear after a head injury with suspicion for concussion. Don’t hesitate to ask questions if you are uncertain about the implications of normal MRI findings.

Conclusion

MRI can provide valuable insights into the effects of head trauma on the brain. Imaging is often appropriately ordered after moderate to severe impacts resulting in loss of consciousness, obvious injury to the skull, protracted symptoms, or risk factors like blood thinners.

However, most minor head bumps do not warrant the time and expense of MRI scanning when no issues develop. Always discuss your unique case with a healthcare provider to determine if neuroimaging is recommended after an injury to ensure the best outcome.