Working Diagnosis:
Atypical concussion in the setting of Chiari Malformation Type 1

Treatment:
Patient was referred to Neurosurgery where she was offered surgical decompression to decrease risk of neurologic injury in the setting of a contact sport. Patient declined as her symptoms had resolved. She was cleared for conditioning with a follow-up appointment with Neurosurgery at 6 months from the injury.

Outcome:
The follow-up appointment with Neurosurgery for unrestricted return to sport prompted MRI of the brain and Magnetic Resonance Arteriogram (MRA) of the cervical spine and brain to assess for associated conditions prior to return to contact. Imaging displayed recession of cerebellar tonsils to 3mm and no signs of vascular or other central cord abnormalities. Patient was subsequently cleared for return to contact.

Author's Comments:
Concussion awareness has risen dramatically in recent years with return to play (RTP) protocols becoming standard in all athletics. However, further evaluation and RTP decisions become much more difficult with repeated, prolonged, or atypical concussions. When these cases arise, further work-up may include imaging such as an MRI. Increasing MRI use has led to the identification of structural abnormalities that may or may not be of clinical significance. Chiari 1 Malformation (CM1) is one such abnormality that can have variable presentations and is often seen incidentally on imaging. Chiari Malformation is an abnormal appearing cerebellar tonsil that is depressed >5mm beyond the foramen magnum (however, using a 3mm cutoff may capture mild cases). Presentations range from mild headaches to severe cerebellar symptoms and neck pain. Symptoms can be exacerbated by traumatic events but usually do not arise until later adolescence or early adulthood (as compared to the CM2 subtype). It is also important to consider that most RTP guidelines are either vague (history of concussion with structural neural abnormality should be a contraindication) in this contraindication or do not address mild forms of CM1 specifically.

While RTP decisions remain unclear, several studies have shown that severe CNS injuries are rare in the CM1 population, and therefore, athletes should be able to participate in contact sports. Studies have also identified that those with prolonged or atypical concussions have a higher prevalence of CM1 than the general population. However, these studies either have low sample sizes, do not account for all contact sports (rugby or hockey), and fail to address whether the prevalence is tied to increased use of MRI that identifies incidental CM1 in persistent concussion symptoms. The lack of clarity reinforces the need for further research and recommendations for RTP. Meanwhile, the sports physician should work closely with specialists while including the athlete in the discussion to maintain an individualized approach that weighs the risk and benefits of that athlete's situation. Finally, it should be noted that RTP in contact sports is contraindicated in cases of CM1 that have a syrinx, syringomyelia, or myelomeningocele.

Editor's Comments:
As discussed by the author, Chiari Malformations can present with their own set of symptoms, but the structural abnormality is typically an incidental finding on neuroimaging when atypical or prolonged concussion symptoms occur.

References:
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Strahle, J., Muraszko, K. M., Kapurch, J., Bapuraj, J. R., Garton, H. J. L., & Maher, C. O. (2011). Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging, Journal of Neurosurgery: Pediatrics PED, 8(2), 205-213.
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Linsenmeyer, Mark MD; Combs, Josefine PsyD; Kegel, Nathan E. PhD; Franzese, Kevin DO Chiari Malformation in the Concussion Clinic: Diagnosis and Management of Confounding and Overlapping Symptoms, American Journal of Physical Medicine & Rehabilitation: November 2020 - Volume 99 - Issue 11 - p 1074-1077
doi: 10.1097/PHM.0000000000001405

McVige JW, Leonardo J. Neuroimaging and the clinical manifestations of Chiari Malformation Type I (CMI). Curr Pain Headache Rep. 2015 Jun;19(6):18. doi: 10.1007/s11916-015-0491-2. PMID: 26017710.

Guinto, Gerardo MD; Abdo, Miguel MD; Aréchiga, Norma MD; Zepeda, Erick MD Different Types of Syringomyelia and Their Management, Contemporary Neurosurgery: October 15, 2009 - Volume 31 - Issue 20 - p 1-7
doi: 10.1097/01.CNE.0000361504.25020.73

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