Printer-Friendly Version

Forward to a Colleague

Permission for Use

Cervical Conundrum

Pathophysiology

Chiari malformation is an uncommon, complex congenital neuroskeletal deformity. The malformation is characterized by caudal descent of the cerebellar tonsils. If the malformation has been present for an extended period of time, the cerebellar tonsils may appear atrophic, and adherent to the dura. The posterior fossa of persons with Chiari malformation is significantly smaller than normal, thus resulting in significant crowding of the posterior fossa structures. The exact pathogenesis of the disorder is unclear. It has been postulated that during embryologic development of the hindbrain and spinal cord, the malformation occurs. An abnormally small posterior fossa forces the tentorium inferiorly, resulting in caudal displacement of the cerebellum. Persons with Chiari I malformation often have no symptoms until the third or fourth decade of life.

Presenting Symptoms

The presenting symptoms can be vague and variable. Subjective symptoms may be insidious, and slowly progressive, leading to misdiagnoses such as multiple sclerosis, amyotrophic lateral sclerosis, myasthenia gravis, or psychiatric disorder. Often, the symptoms are present for months to several years prior to diagnosis. Most symptoms are related to compression of the lower cranial nerves, or brainstem structures. The following are the most common clinical presenting symptoms:

Headache: The headache which is associated with Chiari I malformation generally arises from the upper cervical region, or the suboccipital area. Pain radiates throughout the posterior-occipital region, into the frontal and periorbital areas. Often, the headache is precipitated by cough, sneeze or valsalva maneuvers. Duration of the headache can last from minutes to hours. The headache may be associated with nausea, but infrequently vomiting.

Dysphagia: One of the signs of compression of the cerebellum or lower cranial nerve is dysphagia. Patients may report difficulty swallowing either liquids or solid foods, or a feeling of "catching" in the throat when attempting to swallow. The progression of this symptom may be rapid, suggesting the possibility of aspiration if undetected.

Pain: Patients may complain of neck or upper extremity pain. Often, the pain is worse with exertion, or lifting. Pain can be described as dull and aching, or shooting and stabbing. Unilateral pain is more commonly reported than bilateral pain. Along with the pain, some patients experience weakness of the hands or arms.

Hoarseness: Changes in voice character and timbre are a common complaint. Hoarseness is often noted first by the patient's significant others. Some patients will report inability to modulate the voice for singing or speaking loudly. Slurred speech has been reported; however, this is a less common complaint.

Numbness: Dysesthesia and/or proprioceptive disturbances can also accompany the pain, usually in the same dermatomal distribution. Again, the numbness is generally unilateral, and begins distally. Numbness can progress over months to years to involve the lower extremities and trunk.

Visual disturbance: Patients may complain of various visual disturbances, from blurred vision to diplopia. Nystagmus, or downbeat nystagmus is a common finding, often described by the patient as "bobbing" of the eyes when looking downward or on lateral gaze. Scintillating scotoma may also be reported by the patient, with associated difficulty in driving or reading.

Ataxia: Gait disturbance can be described as unsteadiness, or listing to one side. Patients may report falling, or bumping into walls or doors when ambulating. Infrequently, patients may present with spasticity of the lower extremities, which results in gait disturbance.

Syncope: Syncopal episodes are reported in the literature; however, this is a less common manifestation of the disorder. The episodes are paroxysmal and brief, lasting from 30 seconds to 2 minutes, associated with alteration in consciousness, and prompt, complete recovery. Drop attacks have been also been reported in the literature; however, less commonly in the adult population. There is no post-ictal phase reported, as well as absence of incontinence or tongue-biting. Patients may also complain of transient vertigo, without loss of consciousness.

Syringomyelia

A syringomyelia (or syrinx) is a longitudinal cystic cavitation within the spinal cord containing cerebrospinal fluid. A syrinx may be associated with certain conditions such as spinal cord trauma, neoplasm, or Chiari malformation. The exact etiology of the syrinx is not clear, however, several theories suggest that the mechanism is due to abnormal flow of CSF around the Chiari malformation. As the cerebellar tonsils descend, the normal CSF pathway is blocked. This abnormal dynamic results in a flow void, often necessitating the formation of an abnormal, distended pathway. One theory suggests that the pulsations, along with the abnormal pathway of CSF flow drive the fluid through the center of the spinal cord. This "water-hammer" theory suggests that the force of flow creates the cavitation within the spinal cord.

Another theory suggests that the origin of the syrinx arises from an abnormal alteration in CSF flow at the craniospinal junction. Overcrowding of the craniocervical junction due to herniated cerebral tissue results in blockage of normal flow dynamics. During coughing or other valsalva maneuvers, spinal fluid is quickly pushed upward through the foramen magnum, but because of the partial block, does not come back down easily. The negative pressure inside the cord during relaxation then pulls fluid into the cord.