ABBREVIATIONS ABBREVIATIONS CSF cerebrospinal fluid HA headaches ICP intracranial pressure LP lumbar puncture MRI magnetic resonance imaging VPS ventriculoperitoneal shunt Chiari I malformation is a congenital malformation marked by caudal displacement of the cerebellar tonsils through the foramen magnum. It is an entity for which evaluation by Neurosurgery is common. Chiari I malformation most commonly presents with symptoms of headache similar in nature to those of idiopathic intracranial hypertension (IIH). The treatments for symptomatic Chiari I malformation are traditionally different than those for IIH although some have advocated for suboccipital decompression in Chiari I patients presenting with papilledema.1 The hallmarks of IIH are headaches (HA), visual loss, and papilledema. IIH patients usually undergo lumbar puncture (LP) followed by treatment with antidiuretics such as acetazolamide. The presence of papilledema has traditionally been thought to herald elevated intracranial pressure (ICP); however, its relevance in patients with Chiari I malformation as such an indicator has been sparsely investigated. Our group sought to investigate the incidence and degree of papilledema in a series of patients with known Chiari I malformation. An Institutional Review Board (IRB)-approved chart review of patients presenting with a primary diagnosis Chiari I malformation to the Neurosurgery Clinic was undertaken. No patient consent was required due to the nature of this study. We included a cohort that had undergone either dilated or undilated fundoscopic imaging with photo interpretation independently carried out by 2 Neuro-ophthalmologists. The degree of papilledema was characterized by the Modified Frisén Scale with significant papilledema defined as a grade of ≥3. These findings were then correlated with known surgical history and history of ICP monitoring. Overall, 106 patients with Chiari I malformation were identified. Of those, 36 patients underwent fundoscopic imaging out of which, 16 had formal ophthalmology evaluation by Neuro-ophthalmology. The mean age within this cohort was 15 (2-56-yr-old) with 47% of patients had undergone surgical decompression and one patient had undergone placement of ventriculoperitoneal shunt (VPS) for elevated ICP. In all, 6 patients were found to have grade 1 papilledema, 1 of whom had undergone previous decompressive surgical intervention. Only 2 patients were found to have grade 4 papilledema. The first patient was a 28-yr-old female with uniquely acquired pseudotumor cerebri and subsequent Chiari I malformation, thought to be secondary to oral minocycline administration for treatment of acne. ICP monitoring was used to confirm intracranial hypertension that was shown to resolve, along with her papilledema, with minocycline cessation. The second patient was a 23-yr-old female shown to have normal ICPs upon initial monitoring and a lack of improvement in her papilledema following suboccipital craniectomy and Chiari decompression. Such persistence led to repeat investigation with findings of elevated ICP. Subsequent placement of a VPS was followed by improvement in her fundoscopic exam and visual symptoms. Tonsillar ectopia on magnetic resonance imaging (MRI) is a common finding and often incidental Chiari I malformation.2 Most common symptom in Chiari I malformation is occipital tussive HA. Funduscopic examination should be performed in all patients with HA to rule out papilledema. Papilledema is graded on Modified Frisén Scale with significant papilledema defined as a grade of ≥3. Significant papilledema in Chiari I malformation is rare but are reported.3-5 HA, visual loss, papilledema, and elevated ICP based on LP (>25 cm H2O) are hallmarks of IIH or pseudotumor cerebri. Acquired or idiopathic intracranial hypertension can be associated with tonsillar ectopia and should be considered acquired Chiari malformation.2 It may be difficult to differentiate between Chiari I malformation with papilledema and IIH due to similarities in patient presentations. Vaphiades et al1 have advocated dynamic MRI cerebrospinal fluid (CSF) flow study to differentiate the 2. “If CSF flow at the level of the foramen magnum is abnormal, the Chiari I malformation is likely culprit for the papilledema.” Lumbar punctures in the setting of significant tonsillar ectopia or herniation can be harmful and dangerous.5 In our series, 1 patient became apneic following LP that necessitated emergent suboccipital craniectomy. Choudhari et al5 reported a case of papilledema as the sole presenting feature of Chiari I malformation. Their patient also worsened after LP that required urgent foramen magnum decompression. For the most part, IIH patients with mild tonsillar ectopia can safely undergo LP. Another option is ICP monitoring. However, in our experience, ICP monitoring tends to give lower pressure than LP. Some have advocated Chiari decompression in patients presenting with papilledema.1,4-5 In fact, Zhang et al4 stated that “Surgical decompression of the posterior fossa is the only treatment shown to be consistently effective in Chiari I patients with papilloedema.” On the other hand, Vaphiades et al3 reported resolution of Chiari malformation following a short course of acetazolamide therapy. Significant papilledema is uncommon in Chiari I malformation, though in our experience the presence of papilledema may be suggestive of pseudotumor cerebri or IIH in a select subset of these patients. To be sure, indications for surgical intervention in patients with IIH and Chiari I malformation remains controversial although most would agree with CSF diversion for IIH and suboccipital craniectomy for symptomatic Chiari I malformation. The presence/absence of papilledema remains, at this time, a poor independent indication for surgical intervention over mere observation. Dynamic MRI CSF flow study and ICP monitoring may be useful in certain cases. In our experience, the majority of patients who underwent decompression did so for objective neurological deficits without bearing on fundoscopic findings. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Vaphiades MS, Eggenberger ER, Miller NR, Frohman L, Krisht A. Resolution of papilledema after neurosurgical decompression for primary Chiari I malformation. Am J Ophthalmol . 2002; 133( 5): 673- 678. Google Scholar CrossRef Search ADS PubMed 2. Istek S. Chiari type 1 malformation in a pseudotumour cerebri patient: is it an acquired or congenital Chiari malformation? BMJ Case Rep . 2014; 2014, pii:bcr2013201845. doi: 10.1136/bcr-2013-201845. 3. Vaphiades MS, Braswell R. Resolution of Chiari I malformation following acetazolamide therapy. Semin Ophthalmol . 2007; 22( 1): 9- 11. Google Scholar CrossRef Search ADS PubMed 4. Zhang JC, Bakir B, Lee A, Yalamanchili SS. Papilloedema due to Chiari I malformation. BMJ Case Rep . 2011; 2011, pii:brc0820114721. doi: 10.1136/brc.08.2011.4721. 5. Choudhari KA, Cooke C, Tan MH, Gray WJ. Papilloedema as the sole presenting feature of Chiari I malformation. Br J Neurosurg . 2002; 16( 4): 398- 400. Google Scholar CrossRef Search ADS PubMed Copyright © 2017 by the Congress of Neurological Surgeons
Neurosurgery – Oxford University Press
Published: Mar 1, 2018
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