What is Chiari Malformation?
Chiari Type 1 Malformation is a congenital structural defect in the base of the skull and cerebellum. The cerebellum is the part of the brain located behind the top of the brain stem, low at the back of the head. It has two small areas at the bottom of it called the cerebellar tonsils. Normally, the cerebellum and these tonsils sit entirely within the skull. But in Chiari 1 malformation, these cerebellar tonsils—and sometimes the brain stem as well—lie so low that they descend through the large opening on the base of the skull (the foramen magnum) and into the spinal canal. This is called cerebellar tonsillar ectopia.
What does it have to do with spinal CSF leak?
Sometimes, intracranial hypotension (low cerebrospinal fluid volume/pressure inside the skull) due to spinal CSF leak can be mistakenly attributed to Chiari malformation. In other words, people can be misdiagnosed as having Chiari Malformation, and even have surgery to treat it, when in fact what they really have is a spinal CSF leak.
Though often the symptoms people experience with both conditions are similar—headache, especially after coughing, sneezing, or straining; neck pain; hearing or balance problems; and more—there is a big difference in how each are treated. Thus, when patients are being evaluated for possible Chiari, it’s important for physicians to consider an underlying cause of intracranial hypotension due to spinal CSF leak so that the most appropriate treatment can be planned.
Differentiating between Chiari and spinal CSF leak
A recent study by published in the Journal of Neurosurgery Dr. Peter Kranz at Duke University Medical Center titled “Differentiation of Chiari malformation type 1 and spontaneous intracranial hypotension using objective measurements of midbrain sagging” demonstrated that there are important differences between Chiari 1 and spinal CSF leak that can be seen on brain MRI.
This retrospective study, funded by the Spinal CSF Leak Foundation, compared neuroimaging in adults with Chiari 1 and those with intracranial hypotension due to spinal CSF leak. The results showed highly significant differences between the groups. Importantly, it also showed that none of the patients with spinal CSF leak had cerebellar tonsillar ectopia without also having other findings of midbrain sagging. Ultimately, the study demonstrated the importance of looking at objective measures of midbrain sagging to help prevent misdiagnosis and unnecessary surgery.
Conclusion
Though there are similarities in some of the symptoms and imaging findings between Chiari 1 and spinal CSF leak, there are many important differences, and misdiagnosis can lead to unnecessary surgeries and prolonged suffering for spinal CSF leak patients. An underlying cause of intracranial hypotension due to spinal CSF leak should always be considered so that the most appropriate treatment can be planned.
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For more information on Chiari Malformation, visit Bobby Jones Chiari & Syringomyelia Foundation
You may also read more about Chiari and spinal CSF leak, and other common misdiagnoses, at the following links: