А.Т. FAIZUTDINOVA^1, 2, E.I. BOGDANOV^1, 2

 ¹Republic Clinical Hospital of the MH of RT, Kazan

²Kazan State Medical University, Kazan

 Contact details:

Faizutdinova A.T. — PhD (medicine), Associate Professor of the Department of Neurology and Rehabilitation, neurologist of Clinical Expert Department

Address: 138 Orenburgskiy trakt, Kazan, Russian Federation, 420064, tel.: +7-903-306-44-38, e-mail: aisluzab@mail.ru

Chiari malformation type 1 (СМ1) without a small posterior cranial fossa is a poorly studied variant of the «spectrum of classical primary СМ1», requiring careful differentiation with secondary forms of cerebellar ectopia. An MRI morphometric study was carried out in 59 patients with clinical symptoms of СМ1 (29 with syringomyelia) with ectopia of the cerebellar tonsils of 3 mm or more, a tight cisterna magna, the length of Clivus and Supraocciput of 40 mm or more. The comparison group consisted of 60 patients with classical СМ1 (30 with syringomyelia), and the control group consisted of 30 healthy subjects. As a result of the study, the features of bone phenotype of the pathology in question were revealed, and their pathogenetic role was discussed. The main features of the bone phenotype of clinically symptomatic CM1 without short bones and without signs of secondary cerebellar ectopia, along with the large size of the clivus, supraocciput and the volume of the posterior cranial fossa, are a decrease in the extra-bone part of the posterior cranial fossa, a sharpening of the angle of the bottom, or «funnel» of the posterior cranial fossa, narrowing of the anterior cerebrospinal spaces of the foramen magnum and a decrease in the anteroposterior diameter of the spinal canal at C2 and C6 levels.

Key words: Chiari malformation, small posterior cranial fossa, syringomyelia, ectopia of the cerebellar tonsils.

REFERENCES

1. Fayzutdinova A.T., Bogdanov E.I. Clinical and radiological rationale for the allocation of subtypes of primary Chiari malformation type 1. Zhurnal nevrologii i psikhiatrii im. S.S. Korsakova, 2020, no. 120 (8), pp. 64–69 (in Russ.). DOI: 10.17116/jnevro202012008164
2. Bogdanov E.I. Dislocations of the cerebellar tonsils into the foramen magnum and the spectrum of Chiari malformations type 1. Zhurnal nevrologii i psikhiatrii im. S.S. Korsakova, 2022, no. 122 (4), pp. 7–15 (in Russ.). DOI: 10.17116/jnevro20221220417
3. Milhorat T.H., Nishikawa M., Kula R.W., Dlugacz Y.D. Mechanisms of cerebellar tonsil herniation in patients with Chiari malformations as guide to clinical management. Acta Neurochir, 2010, vol. 152, pp. 1117–1127. DOI: 10.1007/s00701-010-0636-3
4. Bogdanov E.I., Faizutdinova A.T., Heiss J.D. Posterior cranial fossa and cervical spine morphometric abnormalities in symptomatic Chiari type 0 and Chiari type 1 malformation patients with and without syringomyelia. Acta Neurochir, 2021, vol. 163, pp. 3051–3064. DOI: 10.1007/s00701-021-04941-w