CONVERSION TO SYMPTOMATIC CHIARI I MALFORMATION AFTER MINOR HEAD OR NECK TRAUMA
Wan, Michael J. B.Sc.; Nomura, Hiroshi M.D., Ph.D.; Tator, Charles H. M.D., Ph.D.
Toronto Western Research Institute, Toronto Western Hospital, Toronto, Canada (Wan) (Nomura)
Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto Western Hospital, Toronto, Canada (Tator)
Reprint requests: Charles H. Tator, M.D., Ph.D., Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto Western Hospital, Room 4W-433, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada. Email: email@example.com
Received, December 11, 2007.
Accepted, June 4, 2008.
OBJECTIVE: The Chiari I malformation is a rare disorder characterized by downward herniation of the brainstem and cerebellar tonsils through the foramen magnum. Many individuals with the Chiari I malformation do not become symptomatic until adulthood, and the factors that contribute to the onset of symptoms have not been well characterized. The purpose of this systematic chart review was to determine the incidence and validity of minor head or neck trauma as precipitating factors for the onset of symptomatic Chiari I malformation.
METHODS: The charts of all patients seen by the senior author (CHT) between January 1985 and July 2006 were reviewed to identify patients who had presented with symptomatic Chiari I malformation after minor head or neck trauma. Specific inclusion criteria were used to determine whether the onset of symptoms could be reliably attributed to the minor trauma.
RESULTS: Of the 85 patients with symptomatic Chiari I malformation seen by the senior author during this time, 11 (12.9%) had a history of minor head or neck trauma preceding the onset of symptoms. Of these, there were 3 patients (3.5%) in whom the onset of symptoms could be attributed to the trauma based on strict inclusion criteria.
CONCLUSION: Minor head or neck trauma can precipitate the onset of symptoms in a small number of previously asymptomatic patients with Chiari I malformation. Health care professionals must be aware that neurological symptoms that persist or worsen after minor head or neck trauma could indicate an underlying Chiari I malformation.
ABBREVIATION: MRI, magnetic resonance imaging
Chiari malformations constitute a spectrum of disorders of the central nervous system and its bony covering was initially described and categorized by Dr. Hans Chiari, a pathologist at the German University of Prague, in 1891 (6). Chiari malformations are divided into 4 types with differing clinical and pathological features. The Chiari I malformation is the most common dysplasia of the brainstem and cerebellum and is characterized by herniation of the brainstem and cerebellar tonsils through the foramen magnum into the cervical spinal canal. The degree of herniation is variable and can range from a few millimeters to a few centimeters. Commonly associated findings include hydrocephalus, syringomyelia, and a small posterior cranial fossa (24). The exact cause of the Chiari I malformation is unknown, although there is some evidence for a defect of the paraxial mesoderm resulting in a small, shallow posterior cranial fossa and brainstem and cerebellar herniation through the foramen magnum (16,20). The most common symptom of the Chiari I malformation is recurrent suboccipital headache, often aggravated by physical activity, Valsalva maneuvers, coughing, and rapid changes in position (17). Other frequent symptoms include ocular disturbances, dizziness, disequilibrium, dysphagia, and poor coordination. However, there are many vague and nonspecific symptoms associated with the disorder, and the presentation is often variable and ambiguous, leading to a high rate of misdiagnosis (18).
Despite the fact that the Chiari I malformation is generally a congenital defect, patients often remain asymptomatic well into adulthood, and the factors contributing to the onset of symptoms have not been well characterized. However, there have been several case reports citing trauma to the head or neck as a precipitating factor for the onset of symptoms in adults (1,5,19). In this article, we report the results of the first systematic chart review designed to determine the incidence and validity of minor head or neck trauma as a cause for the onset of symptoms in previously asymptomatic Chiari I malformation. Also, we provide a literature review on the topic of minor trauma causing conversion of asymptomatic Chiari I malformation.
PATIENTS AND METHODS
The Research Ethics Board of the University Health Network, of which the Toronto Western Hospital is a component, approved the current study. The charts of all patients seen by the senior author (CHT) between January 1985 and July 2006 were reviewed. Patients with symptomatic Chiari I malformation were identified, and their charts were carefully assessed for any episodes of minor head or neck trauma before the onset of symptoms. For the purposes of this study, trauma was defined as “minor” if the initial posttraumatic clinical examination and diagnostic imaging did not reveal a fracture or neurological injury sufficient to account for progressive neurological deficits. Table 1 lists the specific inclusion criteria applied to detect patients who developed symptomatic Chiari I malformation secondary to minor head or neck trauma. The patient had to be completely asymptomatic from the Chiari I malformation or syringomyelia (if present) before the trauma. The trauma had to be severe enough to cause significant symptoms, such as those associated with a concussion or whiplash injury, to exclude trivial trauma. The initial symptoms had to progress to neurological signs and symptoms attributable to the Chiari I malformation within 6 months, and the posttraumatic symptoms had to be more than would be expected from a postconcussion syndrome or whiplash injury alone. Patients were excluded if there was another structural disorder or disease, such as a neoplasm, or a previous neurosurgical intervention to account for the symptoms. Finally, patients were excluded if their symptoms of Chiari malformation were not severe enough to warrant surgical treatment or if they did not improve or stabilize postoperatively.
To review the available literature on the role of minor trauma in the onset of symptomatic Chiari I malformation, a systematic search of PubMed and Ovid MEDLINE was performed. We used the following search terms: ”Arnold-Chiari malformation” or “Chiari malformation” and “injuries” or “trauma.” The abstracts of all search results were reviewed, and the full texts of relevant articles were obtained. The references of all relevant articles were then reviewed for any additional sources.
Eighty-five patients with symptomatic Chiari I malformation were seen by the senior author during the study period, including 59 (69.4%) female patients and 26 (30.6%) male patients (Table 2). Fifty-four (63.5%) had associated syringomyelia. Eleven (12.9%) patients had a history of minor head or neck trauma before the onset of symptoms, but 8 of the 11 were excluded because they did not meet 1 or more of the inclusion criteria, for the reasons listed in Table 3. Of the excluded patients, only 1 had reported pretraumatic neurological symptoms (recurrent occipital headaches), which may have been related to the patient's underlying Chiari I malformation. Two of the patients had other conditions (Klippel-Feil anomaly and major basilar invagination with severe bony abnormality), which could have accounted for the neurological symptoms that developed posttraumatically. Four patients were excluded because they did not develop significant symptoms immediately after the trauma, and 2 patients did not develop clinically significant neurological deterioration within 6 months. Finally, 3 patients continued to deteriorate after surgical treatment by posterior fossa decompression, indicating some uncertainty that the Chiari I malformation was the most important factor in causing the patients' symptoms.
With strict application of the inclusion criteria, 3 (3.5%) of the 85 patients had onset of symptoms that could be reliably attributed to the minor head or neck trauma, and met all other inclusion criteria, including cessation or improvement of symptoms postoperatively (Table 4). The clinical characteristics of these 3 patients are described below.
A previously healthy 42-year-old woman struck the back of her head violently against a solid object. She immediately felt severe suboccipital pain and, although not rendered unconscious, felt uncoordinated and had to sit down to reorient herself. After the injury, she began experiencing severe headaches every few days. Six weeks after the initial injury, she noted the onset of neck pain, numbness in her arms and shoulders, and weakness in her arms and legs. Over the next 3 years, her neurological symptoms remained severe. Thirty-six months after the initial injury, a magnetic resonance imaging (MRI) scan revealed a Chiari I malformation and extensive syringomyelia (Fig. 1). Because of her persistent symptoms, she was referred for neurosurgical consultation 41 months after the injury. On physical examination, there was a slight amount of weakness in her interosseous muscles and hamstrings bilaterally. The reflexes in her upper limb were diminished, and there was loss of vibration and position sense in her right leg. She initially chose conservative treatment, but her symptoms worsened progressively during the next year. She reported increasing bilateral shoulder pain, numbness below the waist, facial burning, right hand dysfunction, and unsteadiness of gait. On physical examination, she had bilateral lateral gaze-evoked nystagmus, subtle right pronator drift, and subtle right hand intrinsic muscle dysfunction. Her right toe was upgoing and her gait was slightly spastic. A posterior fossa decompression was performed 65 months after the trauma. There were no complications, and the postoperative recovery was uneventful. Five months after surgery, an MRI scan showed excellent bony decompression and a significant reduction in the size of the syrinx, although a postoperative pseudomeningocele had formed. The patient reported that all preoperative symptoms had improved substantially except for mild right arm numbness and occasional unsteadiness. She never developed any symptoms from the pseudomeningocele, and because it has remained stable for several years, it has not been treated.
A 17-year-old girl was in the driver's seat of a stationary car struck in the rear by another vehicle. She immediately felt severe neck and lower back pain and was diagnosed with a minor whiplash injury. Over the following 6 months, her neck pain persisted and she began experiencing nausea and severe headaches with a feeling of “blacking out.” An MRI scan obtained 8 months after the injury showed Chiari malformation with herniation of the brainstem to the level of the posterior arch of C1, and no syringomyelia (Fig. 2A). Because of progressive symptoms, she was referred for neurosurgical consultation 18 months after the injury. She reported that she was continuing to have severe headaches with nausea and intermittent episodes of dizziness with a vertiginous component. Her symptoms were aggravated by physical activity and changes of position. Surgery was recommended, and a posterior fossa decompression was performed 21 months after the injury. The operation was completed without complication and her recovery was unremarkable. One month after the operation, the patient felt that there had been a marked improvement in her headaches, dizziness, and other preoperative symptoms. An MRI scan obtained 6 months after surgery showed excellent decompression, with adequate cerebrospinal fluid around the brainstem (Fig. 2B). Thirty-seven months after surgery, she reported that, except for minor dizziness when standing up quickly, virtually all preoperative symptoms had resolved.
A 42-year-old woman was driving at approximately 80 kph when she struck the broad side of a car that suddenly entered the roadway in front of her. She immediately developed pain in her head, neck, and lower back, with brief periods of retro- and anterograde amnesia. Within 2 months of the trauma, she began experiencing vertigo with neck movement. She also noticed numbness in her right hand, a burning feeling over her posterior thoracic region, and cramping discomfort in her left leg. Thirteen months after the injury, an MRI scan revealed a Chiari I malformation with the cerebellar tonsils herniated 7 mm below the foramen magnum and significant compression of the medulla (Fig. 3A). The MRI scan also revealed a 3-mm-wide syrinx extending from the cervical to the thoracic spinal cord. Her symptoms became progressively worse and she was referred for neurosurgical consultation 22 months after the trauma. She reported that she was now experiencing severe daily headaches that were initiated or intensified by coughing or straining and radiated into her neck. On physical examination, neck motion was limited to approximately 50% of normal and precipitated vertigo. There was imbalance on heel-to-toe walking, and there were subtle changes in sensation for pinprick in her arms and thoracic region. Surgical treatment was recommended and a posterior fossa decompression was performed 27 months after the trauma. Postoperative recovery was uneventful and an MRI scan obtained 6 months after surgery showed excellent bony decompression with adequate cerebrospinal fluid around the brainstem (Fig. 3B). Clinically, the patient's major symptoms resolved and she reported only mild persistent head and neck pain and intermittent paraspinal muscle spasm.
Adults with Chiari I malformation are often asymptomatic and can remain so for many years (11,15). Indeed, it has been estimated that approximately 30% of individuals with cerebellar tonsils herniated 5 to 10 mm below the foramen magnum are asymptomatic (10). Unfortunately, little is known about how previously asymptomatic Chiari I malformations become symptomatic. We are aware of only 1 report that documented the types of events that precipitate the onset of symptoms in asymptomatic Chiari I malformation patients (17). In this study, Milhorat et al. (17) reviewed 364 cases of symptomatic Chiari I malformation and found that the most common precipitating factor was trauma, which was cited by 24.5% of the patients (89 of 364). This differs markedly from the proportion of patients with antecedent trauma in the present series, 12.9% (11 of 85 patients), and even more from the 3.5% of patients (3 of 85) who met our stringent criteria. The difference likely reflects the fact that Milhorat et al. (17) made no distinction between major and minor trauma and did not use specific criteria to establish the strength of the relationship between the traumatic episode and the onset of symptoms. We chose strict inclusion criteria to ensure that the episodes of minor trauma could be reliably attributed to the onset of symptomatic Chiari I malformation, although this likely underestimated the proportion of cases triggered by minor trauma.
The 3 cases presented in this report provide systematic evidence that minor head or neck trauma can trigger the onset of symptoms of a preexisting Chiari I malformation. Although pretraumatic MRI scans were not available, we believe it is highly unlikely that the minor head or neck trauma caused the de novo development of Chiari I malformation. Most cases of acquired Chiari I malformation occur secondarily to defined lesions (e.g., space-occupying) or interventions such as cerebrospinal fluid shunts (3,21,22), and we were unable to find any reports of an acquired Chiari I malformation developing in an adult secondary to minor trauma. Therefore, we believe that our cases were not examples of acquired Chiari I malformation resulting from minor trauma.
In children, there have been 6 reported cases of minor neck trauma and 1 case of minor head trauma causing previously asymptomatic patients with Chiari I malformation to become symptomatic (4,14,23,27). In adults, there has been 1 reported case of minor neck trauma and 2 cases of minor head injury precipitating the onset of symptoms (1,5,19). There have also been several reports of sudden death after minor head trauma in individuals with Chiari I malformation (13,26,28). We believe the present study is the first systematic study to analyze the role of minor trauma as a potential trigger of symptoms in adults with Chiari I malformation. We also report the first cases of minor trauma (Patients 1 and 3) triggering the onset of symptoms in patients with combined Chiari I malformation and syringomyelia.
There are several mechanisms that could account for the onset of symptoms of a Chiari I malformation after minor head and neck trauma. Minor neck trauma can cause direct spinal cord compression, contusion, traction, or ischemic injury, which could potentially damage cerebellar tonsils that have herniated into the upper cervical spinal canal (4,5,23,27). With minor head trauma, there may be a transient increase in intracranial pressure, which would exert downward pressure on the brain and potentially worsen the herniation through the foramen magnum and precipitate the onset of symptoms (1,7,19).
With the increasing use of MRI, a rising number of asymptomatic Chiari I malformations are being identified incidentally, and there is currently no consensus about how to manage and advise such patients (12,25). Although there is not enough evidence to definitively suggest prophylactic surgery or avoidance of contact sports, we believe that patients with asymptomatic Chiari I malformation should be advised that head and neck trauma could potentially trigger the onset of symptoms, and they should be educated about the nature of the symptoms to facilitate early medical intervention. Our study is also relevant for those monitoring the recovery of patients after episodes of minor head or neck trauma. Proper follow-up of these patients is essential because persistent or progressive neurological symptoms could indicate an underlying Chiari I malformation (9), and failure to make an early diagnosis may lead to irreversible neurological deterioration (2,8).
The authors have no personal financial or institutional interest in any of the drugs, materials or devices described in this article.
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Wan et al. have provided compelling evidence to support the notion that trauma can precipitate symptomatic Chiari I malformation. Although the evidence provided is, indeed, compelling, it is not confirmatory. The inclusion and exclusion criteria, as well as the subjective nature of the assessment process, cloud the issues at hand. To attribute the onset of symptoms to trauma in patients with symptomatic Chiari I malformation, one must eliminate secondary gain issues and obligatorily use objective assessment criteria in the decision-making process. Wan et al. have produced seminal work on the subject. Nevertheless, I must also emphasize the “slippery slope” nature of the implications associated with their findings. I remain skeptical.
Edward C. Benzel
Wan et al. reviewed 85 patients who were treated by the senior author over a 21-year span in the magnetic resonance imaging era. Eleven of the patients had a history of neck trauma or minor head trauma preceding the onset of symptoms. On the other hand, only 3 of these patients had onset of symptoms that could be attributed to the trauma. Wan et al. have been very strict in their inclusion criteria. The incidence had been reported previously as per their references. The results presented here should be kept in mind by those who treat a significant number of patients with Chiari I malformation who do not fulfill the criteria for surgical intervention but need to be apprised of the possibility of trauma bringing on their symptoms. Should children with a Chiari I malformation be kept away from taking part in sports?
Arnold H. Menezes
Iowa City, Iowa
Wan et al. have performed a thoughtful retrospective analysis of patients treated by the senior author for symptomatic Chiari I malformation, in whom symptoms commenced after minor head or neck trauma and resolved or stabilized after surgical decompression. It has been established previously that asymptomatic Chiari I malformation may be unmasked by trauma, but this study gives a much clearer estimate of the frequency of this occurrence. As most experienced neurosurgeons have witnessed presentation of symptomatic Chiari I malformation after trauma, the natural question this situation poses is what is the risk of trauma to the patient with an incidental or mildly symptomatic Chiari I malformation? Given our experience with reported serious neurological injury after trauma in such patients (1), I personally counsel the patient and recommend avoiding contact sports. Wan et al. have advanced our knowledge of the incidence of trauma causing presentation of Chiari I malformation.
William T. Couldwell
Salt Lake City, Utah
1. Couldwell WT, Zhang W, Allen R, Arce D, Stillerman CB: Cerebellar contusion associated with type I Chiari malformation following supratentorial head trauma: Case report. Neurol Res 20:93–96, 1998.
In this article, Wan et al. have systematically studied the relationship between minor head trauma and onset of Chiari I malformation symptoms. As with many observations in neurosurgery, pearls are passed down as surgical lore, but are rarely published. Wan et al. then went one step further and analyzed the pearl/premise that previously asymptomatic patients with a Chiari I malformation could experience clinical deterioration, triggered by minor head trauma. Their conclusion is reasonable, recognizable, and well supported as a causal relationship based on their carefully collected data. So, what is the significance of this observation? Both patients and physicians can now be advised that minor head injury is known to precipitate symptoms of Chiari I malformation, and this article is the best reference for that knowledge.
Richard G. Ellenbogen
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