Chiari Malformation Diagnosis

Chiari malformation type 1 (CM1) develop as the skull and brain grow throughout childhood and often cannot be diagnosed until late childhood or adolescence. CM1 vary depending on the size and shape of the cranial malformation responsible for the descending brain tissue and the intensity of the symptoms. If the condition is diagnosed early enough and treated properly, most young patients will recover fully and lead normal lives.


Diagnosing CM1 can be challenging because many of the condition’s most obvious symptoms are also symptoms of other disorders, including headaches in the back of the head that worsen with straining or when performing the Valsalva maneuver, neck pain, dizziness, difficulty swallowing, fatigue and depression. Other, sometimes subtler, symptoms can also tip physicians off to the possibility of CM1, including impairment of fine motor skills; numbness in the hands, arms or legs; blurred vision or diminished hearing; and trouble sleeping. Problems with balance and muscle weakness are also indicative of CM1 but may not always be present.

The lower rear portion of the brain is called the cerebellum, and the lowermost parts of the cerebellum are called the cerebellar tonsils. The cerebellar tonsils usually rest on top of the hole in the bottom of the skull, called the foramen magnum, where the spinal column passes into the back of the skull and through which CSF flows on its route through the central nervous system. In children with CM1, the cerebellar tonsils push through the foramen magnum and into the spinal column.


Symptoms of CM1 typically arise from blocked flow of CSF, compression of the brainstem or the formation of fluid-filled sacs, called syrinx, either in the spinal cord (where they are called syringomyelia) or in the brainstem (where they are called syringobulbia). The CM1 team may have to address one, two or all three of these problems with any single child.

No single test can determine precisely what is causing a CM1 patient’s symptoms or predict whether that child would benefit from surgery. Collaborative examination by an experienced team of Chiari specialists is the only way to zero in on the proper diagnosis and optimal course of treatment. CM1 is defined by the descent of the cerebellar tonsils into the brainstem, but the intensity of its symptoms can vary from patient to patient. Sometimes the tonsils may drop down far but the child remains asymptomatic. In other cases, the tonsils may remain largely above the foramen magnum, yet the child has multiple and intense symptoms. Before we can chart the best course forward for a CM1 patient, physicians must conduct a complete neurological exam to look for symptoms of cerebellar dysfunction, including repetitive, uncontrolled horizontal eye movements (called nystagmus), gait abnormalities, trouble swallowing and an exaggerated response to reflex stimulation. Imaging specialists also must analyze images of the brain, brainstem, spinal cord and the flow of CSF.