Introduction: Chiari I malformation (CIM) is mainly characterized by a descent of cerebellar tonsils below the foramen magnum more than 5mm. Precipitating factors that may convert an asymptomatic CIM to a symptomatic one, or create a de novo syrinx in previously asymptomatic patients, are poorly understood and largely unknown. Surprisingly, so far no association of an increased body mass index (BMI) and CIM patients has been reported.

Methods: We analyzed data from 60 adult patients with Chiari I malformations, 26 of whom had syringomyelia. Factors included the patients’ clinical status (headaches and neurological signs), radiological characteristics of syringomyelia (diameter and vertical extent), BMI, and the relationship of age to BMI, syrinx diameter, and vertical extent.

Results: The mean BMI in all patients was 30.35 (± 87.65), which is Class I obesity (WHO), and was similar in both subgroups of patients (with and without syringomyelia). The vertical syrinx extension was significantly larger in overweight patients (p=0.027) in comparison to patients with normal body weight. Evidence of de novo syrinx formation was found in 2 patients who gained an average BMI 10.8 points. After repeated decompression and no change in the holocord syrinx diameter and vertical extent, a reduction of the syrinx was seen after BMI decreased 11.7 points in one individual. No correlation was found between patients’ age and BMI, patients’ age and vertical extension of the syrinx, and patients’ age and the diameter of the syrinx.

Conclusions: We have recognized a significant association between increased BMI and Chiari I malformations in adults. Gaining weight may influence a de novo creation of the syrinx in adult patients who previously had minimally symptomatic or asymptomatic Chiari I malformations, and reducing weight can improve a syrinx after unsuccessful surgical decompression. Therefore, a reduction of body weight is to be recommended for all overweight and obese patients with Chiari I malformations.

Patient Care: It will point out to physicians association of increased BMI and adult CIM, possibility of de novo syrinx creation with increasing BMI in CIM patients and syrinx improvement with decreasing weight, as well as counsell patients of importance of weight control.

Learning Objectives: By the conclusion of this session, participants should be able to: 1. Elucidate relationship between increased BMI and Chiari I malformation in adults. 2. To understand a potential of a syrinx formation in CIM patients with increasing weight and syrinx improvement with decresing weight. 3. To recognize association of increased vertical extent of syrinx with increasing BMI. 4. To stress the importance of weight control in asymptomatic or minimally symptomatic adult CIM patients.

References: References 1. Aliaga L, Hekman KE, Yassari R, Straus D, Luther G, Chen J, et al: A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery 70:656-665, 2012 2. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases. Neurosurg Focus 11:E3, 2001 3. Arnautovic KI, Al-Mefty O, Pait TG, Krisht AF, Husain M: The suboccipital cavernous sinus. J Neurosurg 86:253-262, 1997 4. Arora P, Pradhan PK, Behari S, Banerji D, Das BK, Chhabra DK, et al: Chiari I malformation related syringomyelia: radionuclide cisternography as a predictor of outcome. Acta Neurochir (Wien) 146:119-130, 2004 5. Attal N, Parker F, Tadic M, Aghakani N, Bouhassira D: Effects of surgery on the sensory deficits of syringomyelia and predictors of outcome: a long term prospective study. J Neurol Neurosurg Psychiatry 75:1025-1030, 2004 6. Badie B, Mendoza D, Batzdorf U: Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery 37:214-218, 1995 7. Ball MJ, Dayan AD: Pathogenesis of syringomyelia. Lancet 2:799-801, 1972 8. Batson OV: The function of the vertebral veins and their role in the spread of metastases. Ann Surg 112:138-149, 1940 9. Batzdorf U: Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 68:726-730, 1988 10. Bidzinski J:. Late results of the surgical treatment of syringomyelia. Acta Neurochir (Wien) 43 (Suppl):29-31, 1988 11. Bindal AK, Dunsker SB, Tew JM: Chiari I malformation: classification and management. Neurosurgery 37:1069-1074, 1995 12. Blagodatsky MD, Larionov SN, Alexandrov YA, Velm AI: Surgical treatment of Chiari I malformation with or without syringomyelia. Acta Neurochir (Wien) 141:963-968, 1999 References 1. Aliaga L, Hekman KE, Yassari R, Straus D, Luther G, Chen J, et al: A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery 70:656-665, 2012 2. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases. Neurosurg Focus 11:E3, 2001 3. Arnautovic KI, Al-Mefty O, Pait TG, Krisht AF, Husain M: The suboccipital cavernous sinus. J Neurosurg 86:253-262, 1997 4. Arora P, Pradhan PK, Behari S, Banerji D, Das BK, Chhabra DK, et al: Chiari I malformation related syringomyelia: radionuclide cisternography as a predictor of outcome. Acta Neurochir (Wien) 146:119-130, 2004 5. Attal N, Parker F, Tadic M, Aghakani N, Bouhassira D: Effects of surgery on the sensory deficits of syringomyelia and predictors of outcome: a long term prospective study. J Neurol Neurosurg Psychiatry 75:1025-1030, 2004 6. Badie B, Mendoza D, Batzdorf U: Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery 37:214-218, 1995 7. Ball MJ, Dayan AD: Pathogenesis of syringomyelia. Lancet 2:799-801, 1972 8. Batson OV: The function of the vertebral veins and their role in the spread of metastases. Ann Surg 112:138-149, 1940 9. Batzdorf U: Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 68:726-730, 1988 10. Bidzinski J:. Late results of the surgical treatment of syringomyelia. Acta Neurochir (Wien) 43 (Suppl):29-31, 1988 11. Bindal AK, Dunsker SB, Tew JM: Chiari I malformation: classification and management. Neurosurgery 37:1069-1074, 1995 12. Blagodatsky MD, Larionov SN, Alexandrov YA, Velm AI: Surgical treatment of Chiari I malformation with or without syringomyelia. Acta Neurochir (Wien) 141:963-96References 1. Aliaga L, Hekman KE, Yassari R, Straus D, Luther G, Chen J, et al: A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery 70:656-665, 2012 2. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari I malformation in patients with and without syringomyelia: a consecutive series of 66 cases. Neurosurg Focus 11:E3, 2001 3. Arnautovic KI, Al-Mefty O, Pait TG, Krisht AF, Husain M: The suboccipital cavernous sinus. J Neurosurg 86:253-262, 1997 4. Arora P, Pradhan PK, Behari S, Banerji D, Das BK, Chhabra DK, et al: Chiari I malformation related syringomyelia: radionuclide cisternography as a predictor of outcome. Acta Neurochir (Wien) 146:119-130, 2004 5. Attal N, Parker F, Tadic M, Aghakani N, Bouhassira D: Effects of surgery on the sensory deficits of syringomyelia and predictors of outcome: a long term prospective study. J Neurol Neurosurg Psychiatry 75:1025-1030, 2004 6. Badie B, Mendoza D, Batzdorf U: Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery 37:214-218, 1995 7. Ball MJ, Dayan AD: Pathogenesis of syringomyelia. Lancet 2:799-801, 1972 8. Batson OV: The function of the vertebral veins and their role in the spread of metastases. Ann Surg 112:138-149, 1940 9. Batzdorf U: Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 68:726-730, 1988 10. Bidzinski J:. Late results of the surgical treatment of syringomyelia. Acta Neurochir (Wien) 43 (Suppl):29-31, 1988 11. Bindal AK, Dunsker SB, Tew JM: Chiari I malformation: classification and management. Neurosurgery 37:1069-1074, 1995 12. Blagodatsky MD, Larionov SN, Alexandrov YA, Velm AI: Surgical treatment of Chiari I malformation with or without syringomyelia. Acta Neurochir (Wien) 141:963-968, 1999