Zyp Czyk's List: Chiari

• Chiari (pronounced key-AR-ee) malformation is a condition in which the lower part of the brain, called the cerebellum, herniates through the skull and down into the spinal canal (Fig. 1 and 2). The herniated tissue compresses the brainstem and blocks the normal flow of cerebrospinal fluid (CSF). The blockage can then cause a buildup of fluid in the spinal cord (syringomyelia) or in the brain (hydrocephalus). Chiari is often misdiagnosed because of the wide variety of bony and soft tissue abnormalities that compress the cervical spinal cord, brainstem, or cranial nerves, resulting in a wide array of possible symptoms. Symptoms include headache, neck pain, dizziness, arm numbness or weakness, sleep problems, fatigue, etc. Headache in the back of the head that worsens with coughing, sneezing, or straining is a hallmark symptom.
• However, symptoms typically progress and worsen over time.
• Chiari type I, the most common, affects both children and adults (Fig. 2). Because the back of the skull is too small or deformed, a crowding of the brainstem, cerebellum, and tonsils occurs. As the tonsils push out of the skull opening (foramen magnum), they press onto the spinal cord and block CSF flow. Chiari I sometimes is found with a fluid-filled cyst (syrinx) in the spinal cord. Symptoms, which may not appear until late childhood or adulthood, include severe headache, neck pain, imbalance, dizziness, swallowing problems, numbness in the hands, depression, fatigue, and sleep problems.

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• The skull is formed from eight bones that fuse together along suture lines. Of interest in Chiari are the occipital bone (where the skull and spinal column connect) and the top two spinal bones (C1 and C2 vertebrae). In the middle of the occipital bone lies the foramen magnum, an opening where the spinal cord connects to the brainstem.

   

  Inside the skull are three areas: anterior fossa, middle fossa, and posterior fossa. The posterior fossa contains the brainstem, cerebellum, and cranial nerves IV-XII (Fig. 3A).   

• A variety of bone abnormalities can occur in patients affected by Chiari:

   

   

  • The posterior fossa may be smaller than normal. If too small, the effects can be crowding of the brainstem and cerebellum, as well as herniation of the tonsils through the foramen magnum (Fig. 3B).

   

  • Sometimes the occipital bone is misshaped or thickened.

   

  • Basilar invagination is a condition where the top of C2 (odontoid) pushes upward into the foramen magnum. This defect can narrow the foramen magnum and crowd the brainstem and cerebellum causing Chiari-like symptoms.

   

  • Scoliosis is a bone deformity that causes curvature of the spine. There is a high rate of scoliosis associated with Chiari and syringomyelia, especially in children.

   

  • Ehlers-Danlos syndrome (EDS) is a connective tissue disorder that may increase the incidence and severity of Chiari. EDS causes joint hypermobility and loose/unstable joints. In an area called the craniocervical junction, strong ligaments attach the C1 and C2 vertebrae to the skull, allowing movement of the head. For someone with both Chiari and EDS, extra testing and precautions are taken to ensure the connection between the spine and skull is intact. Spinal fusion surgery may be needed to support the neck and skull.

• Cerebellum herniation
   

   

  The cerebellum is the lower part of the brain located in the posterior fossa. On the underside of the cerebellum are two tonsils (Fig. 4). The cerebellum primarily coordinates body movement. It maintains muscle tone and balance. The cerebellum is also involved in cognitive functions (e.g., attention, language), memory, and learning. Signs of cerebellum problems include loss of coordination, unstable walking (gait), trouble with speech, and difficulty with eye movement and swallowing.

   

• In Chiari, the cerebellar tonsils are stretched as they push through the foramen magnum into the spinal canal (Fig. 5). This results in compression of the brainstem and spinal cord. The extent and progression of this tonsillar herniation can be seen on MRI. 

• Acting as a relay center, the brainstem connects the cerebrum and cerebellum to the spinal cord. The brainstem performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, and coughing. Ten of the 12 cranial nerves originate in the brainstem.

   

• Cerebrospinal fluid blockage
   

   

  Cerebrospinal fluid (CSF) is a clear, watery-like liquid that flows within and around the brain and spinal cord. CSF helps keep the brain buoyant and cushions it from injury. This fluid is produced inside the ventricles by the choroid plexus and is constantly being absorbed and replenished.

   

  The CSF flows through the ventricles and out into the space between the brain and skull (subarachnoid space) and down into the spinal canal (Fig. 6). A large amount of CSF lies at the back of the cerebellum in an area called the cisterna magna. CSF drains from the fourth ventricle into the cisterna magna. From there it then circulates down into the spinal canal and around the spinal cord. CSF also flows from the fourth ventricle down the central canal inside the spinal cord.

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• often leading to misdiagnosis and delay in treatment. At times, Chiari I is mistaken for fibromyalgia, chronic fatigue syndrome, migraine, multiple sclerosis, mental disorder, depression, sinus disease, trigeminal neuralgia, or other neurologic disorders.

• Because the brainstem is responsible for most body functions, Chiari causes all kinds of strange symptoms. People may experience symptoms that range from headache to irritable bowel. The five most common symptoms are:

   

   

  1. posterior headache on exertion with neck pain (70%)
    2. hoarseness or swallowing problems
    3. sleep apnea
    4. weakness or numbness in an extremity
    5. balance problems

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  Chiari symptoms are caused by disruption of CSF flow and compression of the brainstem
    and spinal cord.

   
• Some patients have had Chiari triggered by a spinal tap or epidural anesthesia.

• Headache

   

   

   

  • Pressure-like headaches that start at the back of the skull and may radiate behind the eyes.
    • Headaches that worsen with physical strain, coughing, sneezing, or bending forward (Chiari headaches are often mistaken for migraines)

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• In patients with severe symptoms or with a syrinx, surgery is advisable. The goals of surgery are to stop or control the progression of symptoms caused by herniation of the cerebellar tonsils, and relieve compression of the brainstem.

   

  In patients with a syrinx, the goal of surgery is to prevent or control progression. Symptoms related to the obstruction of CSF should decrease as flow normalizes.

• • Posterior fossa decompression is a surgical procedure that removes bone at the back of the skull and spine to widen the space for the tonsils and brainstem (Fig. 13). The surgeon opens the dura overlying the tonsils and sews a patch to expand the CSF space, similar to letting out the waistband on a pair of pants.

   
• the amount of bone removal needed to effectively restore normal CSF flow depends on the individual patient’s anatomy and size of Chiari.
• • Spinal fusion may be performed in addition to posterior fossa decompression surgery in certain patients with spine instability
• • Shunting is used to reroute CSF. The shunt includes a flexible tube with a 1-way valve that directs the fluid out in the desired direction.

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• If you have more questions, please contact the Mayfield Chiari Center at 800-325-7787 or 513-221-1100. More information is on the web at:

   

  American Syringomyelia Alliance Project

   

  Conquer Chiari

   

  Chiari & Syringomyelia Foundation

   

  Chiari Connection International

   

  World Arnold Chiari Malformation Association

   

  Ehler-Danlos National Foundation

   

  Spina Bifida Association