Chiari I malformation with acute neurologic deficit after craniocervical trauma: Case report, imaging and anatomic considerations David E. Adler, MD, Josha Woodward, BS
Legacy Emanuel Hospital
In patients with Chiari I malformation, the occurrence of acute neurological deficit after craniocervical trauma is rare. This case describes a 41-year-old male who sustained a single blow to the face, fell and struck the occiput. On admission, neurologic exam revealed a profound paraparesis, upper extremity diplegia, and apnea, which required intubation. Computerized axial tomography of the head showed a small amount of contra coup left frontal traumatic subarachnoid hemorrhage. MRI of the brain and upper cervical spinal cord performed within 19 hours after admission was negative except for the presence of a Chiari I malformation. All other radiographic studies at the time of admission were normal. The constellation of severe neurologic deficits after relatively minor craniocervical trauma in patients with Chiari I malformation has been well described. However, MR imaging has not been able to clearly define the underlying pathoanatomy nor help understand the mechanism of injury. Here, we review similar cases and suggest a mechanism to explain the occurrence of severe neurologic deficit after craniocervical trauma in patients with Chiari I malformation. Introduction
Chiari I malformation (CMI) represents a spectrum of disease defined as overcrowding of the posterior fossa of varying degrees (Milhorat). 91% of the 364 patients studied by Milhorat et. al. showed at least 5 mm of tonsillar decent through the foramen magnum. The implications of compromised space at and below the level of the foramen magnum reach beyond the usual presenting signs and symptoms in a patient with CMI. There have been a handful of reported cases of CMI presenting variably as profound neurologic deficit to near sudden death in patients who sustain relatively minor head/neck trauma. It is suggested that a reduction of subarachnoid space at the level of the cervicomedullary junction in individuals with CMI predisposes tissue within the foramen magnum to injury. (to an increased susceptibility to neurologic deficit secondary to craniocervical trauma) (Couldwell, Mampalam, Tomaszek, Vlcek). Other reported cases describe minor craniocervical trauma in individuals with CMI, which caused severe neurologic deficit or even death, which is similarly confirmed by this case (Mampalam, Tomaszek, Friede, Wolf). CMI is considered rare(National Organization of Rare Diseases: Directory. New Fairfield, CT, national Organization of Rare Diseases, 1999) and its incidence is uncertain. However, an incidence of 0.77% is suggested after a review of 22,000 MRIs demonstrated cerebellar tonsillar ectopia of greater than 5 mm below the level of the foramen magnum (Aboulezz et. Al. Position of cerebellar tonsils in the normal population and in patients with Chiari malformation: A quantitative approach with MR imaging. J Comput Assist Tomogr 9:1033-1036, 1985). Presenting symptoms range from severe headache, nausea and vomiting to numbness, tingling and weakness. Symptoms may also relate to lower cranial nerve palsies, causing dysphagia or dysphonia. Neurologic signs may include spasticity, motor and sensory deficits. Neurootologic or neuroophthalmologic findings ranging from nystagmus to impaired visual acuity and papilledema (?) may also be found. It is difficult to diagnose CM because of the variable signs and symptoms that are often nonspecific. MRI usually confirms the diagnosis. A certain group of patients presented following trauma in an immediate or delayed fashion. In Milhorat’s series, 23 of the 126 patients (18%) with CMI presented after experiencing a whiplash injury or a direct blow to the head. In Levy’s 127 cases of CMI 8 (6%) were characterized as having “post traumatic syndrome” before making the diagnosis of CMI. The extent of neurological deficits does not...
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