PEDIATRICS Vol. 107 No. 1 January 2001, pp. 182-184

EXPERIENCE AND REASON:
Complete Spontaneous Resolution of Childhood Chiari I Malformation and Associated Syringomyelia

	ABSTRACT

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The diagnosis of Chiari I malformation and associated syringomyelia is often made in childhood. Since the advent of magnetic resonance imaging, these abnormalities are increasingly detected incidentally. Despite incomplete understanding of the natural history of asymptomatic Chiari I malformations, the current recommendation is to consider prophylactic surgical intervention in those with an associated syringomyelia. This case report presents a complete spontaneous resolution of a Chiari I malformation and syringomyelia in a child. It illustrates the possibility that asymptomatic children with Chiari I malformations and syringomyelia may be followed conservatively.

Chiari I malformation is the congenital downward displacement of the cerebellar tonsils into the cervical canal. It is often associated with syringomyelia, which is a cavitary dilation of the spinal cord. The diagnosis is often made in childhood and symptomatic children respond favorably to surgical treatment. Magnetic resonance imaging (MRI) has facilitated the diagnosis and an increasing number of incidental Chiari I malformations are seen.¹ The natural history of an asymptomatic Chiari I malformation in children is not known. Nevertheless, it is generally accepted that the presence of a syringomyelia with Chiari I malformation warrants consideration of a surgical decompression, even in an asymptomatic child.² We present a child whose incidental Chiari I malformation and associated cervical syringomyelia spontaneously and completely resolved over a 7-year interval. This case illustrates a variable natural history of Chiari I malformations with syringomyelia and the option of conservative management in asymptomatic children.

	CASE REPORT

A 7-year-old boy was evaluated for a 1-month history of headaches, which occurred daily after exercise, or awoke the patient in the morning. These headaches were bitemporal in nature and described as throbbing. The most severe episodes were associated with nausea and occasionally vomiting. There was no association between the headaches and Valsalva maneuvers. His neurologic examination was nonfocal. There was a strong family history of migraine headaches and the child was diagnosed with common migraine headaches. As part of the initial evaluation for his headaches, the patient underwent a MRI of the head. This MRI showed a Chiari I malformation and an associated cervical syringomyelia (Fig 1A). The brain was otherwise normal. He was seen in neurosurgical consultation and underwent a repeat brain and cervical spine MRI with contrast to rule out enhancement. The repeat MRI confirmed the presence of Chiari I malformation with associated syringomyelia. There was no enhancement. This was felt to be an incidental finding and the patient was treated for migraine headaches and monitored.

View larger version (111K): [in this window] [in a new window]   Fig. 1.   Sagittal T1-weighted MRI with contrast demonstrating a Chiari I malformation with 13 mm of tonsillar herniation below the foramen magnum (large arrow). There is an associated cervical syringomyelia without enhancement (small arrow, A). Follow-up image reveals resolution of the Chiari I malformation with the tonsils <2 mm below the foramen magnum (arrow) and complete disappearance of the cervical syringomyelia (B). Dotted lines represent the foramen magnum.

The patient's headaches initially improved with dietary modification alone, in particular the removal of chocolate. At age 13, the severity and duration of the infrequent headaches increased despite the institution of medication. The patient had grown from 122 cm at age 7 to 156 cm at age 13, and he had become sexually mature. A repeat MRI was performed to evaluate the Chiari I malformation. It was read as normal by the neuroradiologist: the Chiari I malformation completely resolved and the associated syringomyelia disappeared (Fig 1B). At the time this article was submitted, he was 16 years old and he continues to have recurrent severe migraine headaches every 2 to 3 months. He is being treated with Inderal prophylaxis and acute interventions. The neurologic examination remained nonfocal and the physical examination unremarkable.

	DISCUSSION

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In 1891, Chiari described 4 congenital anomalies of the lower brainstem and inferior cerebellum.³ The type I malformation consists of downward herniation of the cerebellar tonsils through the foramen magnum. Herniation of the tonsils >5 mm below the foramen magnum on MRI is considered diagnostic.⁴ A Chiari I malformation may also be occasionally acquired from increased intracranial pressure in conditions such as head injury, hydrocephalus, or craniosynostosis. Syringomyelia has been noted to accompany 50% to 70% of patients with Chiari I malformations.¹ Obstruction of cerebrospinal (CSF) flow at the craniocervical junction from the tonsillar herniation has been shown to create perivascular movement of CSF from the spinal subarachnoid space into the spinal cord with each Valsalva maneuver and systole to form the syringomyelia.⁵

The Chiari I malformation and resulting syringomyelia can cause a host of neurologic manifestations. The most common presenting symptom from a Chiari I malformation is pain, which can be a headache or nonradicular pain in the shoulder, back, and limbs. The headache differs from migraine and other forms of headaches in that it is usually suboccipital and upper cervical in location and is exacerbated by Valsalva maneuvers. Impaction of the tonsils against the cervicomedullary structures can cause brainstem dysfunction, sensory disturbance, and motor loss. The syringomyelia is associated with the development of a painful, rapidly progressive, or left-curving scoliosis. The cavitation within the central gray matter can produce a segmental or suspended sensory loss of pain and temperature by interrupting crossing fibers of the spinothalamic tract while preserving touch and the deep sensibility whose fibers ascend ipsilaterally in the dorsal column before entering the gray matter. Further compression by the Syrinx can affect the long tracts in the white matter and lead to spastic quadriparesis. Presentation during childhood is increasingly recognized.^5-7 A detailed neurologic evaluation is essential, as the impairments may be subtle and the onset insidious. Symptomatic patients can be successfully treated by a variety of surgical decompression techniques to restore CSF dynamics across the craniocervical junction.^6-8 Failing a decompression, a persistent syrinx can also be directly addressed by shunting.^9,10

The ability of MRI to visualize the craniocervical junction and spinal cord has facilitated the diagnosis of Chiari I malformations and associated syringomyelia. As a result, Chiari I malformations with or without syringomyelia are now increasingly encountered as incidental findings.¹ Although there is a pattern of progressive neurologic impairment in most symptomatic patients,¹¹ the natural history of asymptomatic patients with a Chiari I malformation and syringomyelia is not well-defined. Cases of acute neurologic deterioration, syncope, cardiac arrest, and even sudden death have been reported as the presenting event in patients with medullary compression and large syringomyelia from a previously undetected Chiari I malformation.^12-15,16 However, most of these cases were symptomatic well before their catastrophic presentations. Only Minorat¹¹ has reported 1 case of a 4-year-old child without a history of weakness, scoliosis, or paroxysmal complaints who presented with cardiopulmonary arrest and was found to have a Chiari I malformation and large holocord syringomyelia on MRI. There was no autopsy. Sudden death after minor trauma have also been reported in adults and children with Chiari I malformations; but as reviewed by James, ¹⁷ all cases were previously symptomatic Chiari I malformations or involved additional confounding factors such as alcohol use or congenital cervical abnormalities. So, collectively, these case reports do not necessarily provide a compelling rationale to treat asymptomatic Chiari I malformations. But once an associated syringomyelia has developed with a Chiari I malformation, obstructed CSF dynamics at the foramen magnum from the tonsillar herniation would theoretically lead to progression of the syrinx and eventual symptoms. And once neurologic deficits develop from a syringomyelia, they do not typically reverse completely with surgery.¹⁸ Consequently, the small risk of prophylactic surgery including stroke, CSF leakage, infection, and delayed craniocervical instability is felt to be justifiable. The degree of apparent brainstem compression at the foramen magnum and size of the syringomyelia are also considered when evaluating an otherwise asymptomatic patient. Presently, very few patients with a significant syringomyelia associated with Chiari I malformation are left untreated.¹⁹

On the other hand, cases of spontaneous radiographic improvement of childhood Chiari malformations and syringomyelia have been recently reported. In symptomatic children, 3 cases of spontaneous resolution of Chiari I malformation and improvement of syringomyelia on follow-up MRI have been reported.^20-22 The neurologic deficits were improved in 1 case and unchanged in the other 2 cases. In asymptomatic children, the spontaneous resolution of an incidental Chiari I malformation alone without an associated syringomyelia has been reported by Castillo²³; and Avellino²⁴ described the spontaneous resolution of an incidental Chiari I malformation with marked reduction in size, but not total disappearance, of an associated cervical syringomyelia from age 6 to 10. The patient presented here has migraine headaches but otherwise has had no signs or symptoms referable to the Chiari I malformation or syringomyelia. Consequently, this patient represents a complete spontaneous resolution of an incidentally discovered, asymptomatic childhood Chiari I malformation and associated syringomyelia. The Chiari I malformation normalized and the syringomyelia totally disappeared over 6 years on follow-up MRI. Although the tonsillar herniation was significant, the cervical syrinx in our patient is relatively small at 30 mm × 12 mm as compared with the holocord syringomyelia in the 4-year-old patient with cardiopulmonary arrest reported by Martinot.

The cerebellar tonsils normally ascend with age.²⁵ Therefore, in the pediatric population, Chiari I malformations can conceivably resolve from axial growth.²³ Our patient grew 34 cm from the age of 7 to 13. The relative skeletal growth across the craniocervical junction, along with some enlargement of the posterior fossa, may have pulled the tonsils out of the foramen magnum. Once the tonsillar are pulled up sufficiently to restore normal CSF dynamics across the craniocervical junction, the result can be a complete resolution of the syringomyelia. In the absence of any intracranial pathology, the prognosis of a completely resolved asymptomatic Chiari I malformation and syringomyelia should be excellent. However, recurrence of a spontaneously resolved symptomatic Chiari I malformation and fluctuation in the size of the syringomyelia was seen one of the reported cases.²² Rupture of the syringomyelia into the subarachnoid space has also been proposed to account for the spontaneous decompression of a large holocord syrinx in an adult.²⁶ The Chiari I malformation and neurologic deficits in that patient remained. Given the relatively small size of the syringomyelia in our patient, the lack of neurologic deficits, and concurrent resolution of the Chiari I malformation, spontaneous decompression through a tear in the spinal cord seems less likely.

At present, a prophylactic decompression is generally considered for an asymptomatic child with Chiari I malformation in the presence of an associated syringomyelia. Our case adds to the small body of emerging evidence which demonstrates that the natural history of asymptomatic Chiari I malformations and associated syringomyelia is not universal progression. Conservative management with serial imaging and close neurologic monitoring may be considered in asymptomatic childhood Chiari I malformations with associated small to moderately sized syringomyelia.

Peter P. Sun, MD
Division of Neurosurgery
Children's Hospital, Oakland
Oakland, CA 94609

James Harrop, MD
Division of Neurosurgery
Thomas Jefferson University
Philadelphia, PA 19107

Leslie N. Sutton, MD
Donald Younkin, MD^§
Divisions of  Neurosurgery and ^§ Neurology
Children's Hospital of Philadelphia
Philadelphia, PA 19104

	FOOTNOTES

Received for publication Apr 20, 2000; accepted Aug 1, 2000.

Reprint requests to (P.P.S.) Division of Neurosurgery, Children's Hospital Oakland, 744 Fifty Second St, Oakland, CA 94609. E-mail: psun{at}mail.cho.org

	ABBREVIATIONS

MRI, magnetic resonance imaging; CSF, cerebrospinal fluid.

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