What Differences Exist in the Appropriate Treatment of Congenital Versus Acquired Adult Chiari Type I Malformation?

Abstract

Chiari type I malformation is found in 1 out of 20 magnetic resonance imaging (MRI) studies. Isolated tonsillar herniation is of limited utility and should be considered within the clinical context because these patients can be asymptomatic. Cine MRI showing compression of the cerebrospinal fluid (CSF) spaces in the foramen magnum area is a crucial technique for making treatment decisions. Congenital malformation is thought to be due to a volumetric small posterior fossa. The most common symptom in these patients is cough headache. Posterior fossa reconstruction is mandatory in patients with progressive symptoms/signs, hydrocephalus, or syringomyelia, but not in patients who are asymptomatic or those with stable and tolerable symptoms. Acquired tonsillar descent can be secondary to a variety of disorders conditioning disproportion between the volume of the cranial cavity and that of the intracranial contents, or to CSF hypovolemia, which is the most common cause for acquired herniation. CSF hypovolemia can be spontaneous or secondary to CSF removal. Treatment of acquired tonsillar herniation depends on the responsible etiology.

Unexpected Progression of Tonsillar Herniation in Two Pediatric Cases with Chiari Malformation Type I and Review of the Literature

“…In our second patient, de novo tonsillar herniation was surprisingly observed, which should be called “acquired CM-1.” Acquired tonsillar herniation result from disproportion between the volume of cranial cavity (mainly posterior fossa) and intracranial contents (growing of a mass or fluid) causing intracranial hypertension, or secondary to CSF hypovolemia [22-24]. The most common cause consented for acquired CM-1 is CSF hypovolemia, generally secondary to the removal of CSF by lumbar puncture or spontaneous leaks [25].…”

Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation Type I

“…14,21 Dynamic imaging studies therefore provide additional utility in assessing the degree of impairment. Some authors describe using ultrasonography with color Doppler imaging in addition to MRI in order to demonstrate anatomical compression as well as impaction of CSF flow.…”

“…15 In CM-I, symptoms can recur even with adequate surgical intervention of any kind, 15,17 and therefore the surgeon must ensure sufficient execution of surgical technique to minimize potential treatment failure. Given that a significant portion of the underlying pathology may be secondary to CSF flow obstruction, 21 cine flow MRI provides an important tool to assess CSF flow. With this, we show that phase-contrast cine flow MRI can contribute to the preoperative evaluation as well as corroborate whether a satisfactory decompression has occurred.…”

“…21 Cine flow imaging may have the greatest utility in an asymptomatic or minimally symptomatic patient with an incidental finding of tonsillar herniation, when surgical treatment based only on abnormal anatomy has uncertain benefit. 21 While traditional MRI is unable to capture Valsalva-related changes in CSF flow, cine flow can measure the more dynamic fluctuations relevant to patients with CSF obstruction.…”

“…21 Cine flow imaging may have the greatest utility in an asymptomatic or minimally symptomatic patient with an incidental finding of tonsillar herniation, when surgical treatment based only on abnormal anatomy has uncertain benefit. 21 While traditional MRI is unable to capture Valsalva-related changes in CSF flow, cine flow can measure the more dynamic fluctuations relevant to patients with CSF obstruction. 4 Although we were only able to obtain preoperative cine flow images for 8 (44.4%) of 18 patients in this study, multiple studies have demonstrated that cine flow MRI has additional value for evaluating which patients are most likely to benefit from surgical intervention.…”