ANATOMY AND PHYSIOLOGY
The cerebellum (Latin for “little brain”) is smaller than the cerebrum. It has the appearance of a separate structure attached to the bottom of the cerebral hemispheres. The cerebellar tonsils are rounded lobules on the underside of the cerebellum, attached to the posterior lobe of the cerebellum. They are seen at the base of the skull. The primary role of the cerebellum is that of motor control – controlling coordination, balance, and muscle movement.
The cerebellar tonsils can elongate due to pressure and slip or be pushed through the foramen magnum – the hole in the bottom of the skull. This tonsillar herniation is referred to as a Chiari I malformation, named after German pathologist, Hans Chiari, who first described the abnormality of the brain at the junction of the skull with the spine. Put bluntly, it’s a condition in which brain tissue extends into the spinal canal.
PRESENTATION AND SYMPTOMS
Chiari I malformations are commonly congenital and for the most part, asymptomatic. They are typically discovered through routine MRIs of the brain or cervical spine. As a rule, radiologists will report on the placement of the cerebellar tonsils in all cervical and brain MRI reports. The Chiari I malformation is characterized by a downward displacement of the cerebellar tonsils more than 4 millimeters, beneath the foramen magnum into the cervical spinal canal. The displacement may block the normal pulsations of CSF between the spinal canal and the intracranial space.
There are a host of symptoms associated with this condition, the most common being:
Severe headaches Numbness in arms, legs, or face
Neck pain/stiffness Dizziness
Muscle weakness Vision problems
Unsteady gait Clumsiness
Poor hand coordination Muscle spasticity
ETIOLOGY AND TREATMENT
Unfortunately, treatment options for Chiari Malformation-related symptoms are very few. Decompression surgery is used in a very small number of cases involving extremely severe pain or neurological problems. Most treatment is directed at management of the symptoms.
While typically congenital, Chiari I malformation symptoms can also be induced due to head trauma. Studies have shown that trauma to the head or neck, such as whiplash, can cause pre-existing Chiari I malformation to turn symptomatic.
WHIPLASH
A study titled “Chiari and Whiplash Injury”, one of the few to look at the connection between whiplash and brain injury, was published in the journal Brain Injury in 2010 by Ezriel Kornel, MD, Michael Freeman, Ph.D., and others. In this study, 1200 cervical MRIs of patients with neck pain were reviewed. Half of the patients had a history of trauma, and the other half did not. Of the patients who had a history of whiplash, 23% showed findings of Chiari I malformation. It was concluded that an undetected Chiari I malformation can be “awakened” as a result of trauma during a motor vehicle crash, triggering symptoms relating to Chiari I malformations.
While these studies determined that head or neck trauma is capable of “triggering” symptoms of Chiari I malformations, could motor vehicle crash trauma actually be the sole cause of a Chiari I malformation? The answer is – definitely possible. The theory is that those suffering from a Chiari I malformation have an underdeveloped cranial cavity making the individual predisposed to an exacerbation or aggravation of this pre-existing condition. Trauma can force the cerebellum deeper into the foramen magnum. As a result, an asymptomatic Chiari I malformation can suddenly become symptomatic as a result of the accident. There is also clinical evidence showing that dural leaks causing reduced CSF levels are in fact associated with whiplash trauma. Accordingly, it is quite possible that whiplash trauma could cause a dural leak that results in Chiari I malformation.
I’ve had experience treating patients with Chiari I malformation, symptomatic and asymptomatic. One patient, a male in his 50s, was involved in a significant rear end collision resulting in whiplash or CAD (cervical acceleration deceleration injury). Recall that the criteria for Chiari I malformation is a downward herniation of one or both cerebellar tonsils of more than 4 millimeters. My patient had a downward displacement of 7 millimeters. In addition to neck pain, he suffered severe headaches and disabling bouts of dizziness that prevented him from working his manual job. He was referred to a neurologist who treated him with medication and vestibular training but unfortunately, the patient did not improve.
A CASE?
Getting back to our original question, does Chiari I malformation pierce the verbal threshold? Given the evidence, I believe it does. I fully understand and appreciate that moving forward with a case such as this requires a sophisticated medicolegal answer and approach. Can your client recover for exacerbation or aggravation of a pre-existing condition? Is there a history of the patient being asymptomatic as it relates to the Chiari I malformation? Can we show the head/neck trauma caused or worsened Chiari I malformation, or did it “awaken” the symptoms of such? Can we line up the opinion of the radiologist and neurosurgeon? All good questions but given the pain and disability these individuals face through no fault of their own, they certainly deserve an honest investigation into the viability of such a case.
