Clinical and neuroimaging features of central canal cavities of the spinal cord: results of our own observations

Despite the development of diagnostic criteria for spinal cord cavities – syringomyelia and hydromyelia – there remains a degree of uncertainty in this area and a certain ‘grey area’ of intermediate cases. Among these is the enlargement of the central canal of the spinal cord, a condition with insufficiently defined clinical significance, which complicates the prediction of the course of the disease and the choice of management strategies for patients.

Objective: to identify the range of clinical and radiological presentations of central canal cavities of the spinal cord and the characteristics of their progression, and to develop prognostic criteria.

Material and methods. The study included 104 patients with central canal cavities measuring ≤4 mm in diameter, as determined by magnetic resonance imaging (MRI). Depending on the presence of occlusion factors at the craniovertebral junction (CVJ), two groups were formed: without occlusion (n=73) and with cerebellar tonsillar ectopia (n=31). A two-stage clinical-neurological and MRI-based morphometric examination was conducted. The duration of follow-up ranged from 2 to 10 years.

Results. In both groups, the cavities exhibited similar characteristics: a central location, a symmetrical shape, a diameter of ≤4 mm, and stability over time. The clinical picture in both groups was dominated by non-specific pain phenomena and non-progressive scoliotic deformity, requiring interpretation in terms of the myelopathic manifestations of cavitation. At the same time, a significant proportion of the cavities were detected incidentally during MRI scans performed for other indications, and the search for correlations between clinical and MRI characteristics did not reveal any significant associations. In patients without CVJ occlusion factors, the cavities were predominantly located in the thoracic region (65.5%), were characterised by greater length (median 59.9 [33.4; 111] mm) and, in a number of cases, demonstrated a statistically significant reduction in cavity length (17.4%; p=0.005). In patients with ectopic cerebellar tonsils, the cavities were more frequently located in the cervical segment (71%; p=0.008), had a shorter length (median 38.55 [17.0; 68.5] mm; p=0.009) and did not show significant regression.

Conclusion. Distinguishing between central-channel cavities based on the presence or absence of changes at the CVJ level is of fundamental importance for prognosis: the hydromyelia variant is characterised by a favourable course, whereas the syringohydromyelia variant has an uncertain prognosis and requires close, ongoing monitoring.

1. Leclerc A, Matveeff L, Emery E. Syringomyelia and hydromyelia: Current understanding and neurosurgical management. Rev Neurol (Paris). 2021;177(5):498-507. doi: 10.1016/j.neurol.2020.07.004

2. Holly LT, Batzdorf U. Slitlike syrinx cavities: a persistent central canal. J Neurosurg. 2002;97(2 Suppl):161-5. doi: 10.3171/spi.2002.97.2.0161

3. Jinkins JR, Sener RN. Idiopathic localized hydromyelia: dilatation of the central canal of the spinal cord of probable congenital origin. J Comput Assist Tomogr. 1999;23(3):351-3. doi: 10.1097/00004728-199905000-00004

4. Kyriacou S, Man Y, Plumb K, et al. Is a persistent central canal a risk factor for neurological injury in patients undergoing surgical correction of scoliosis? Scoliosis Spinal Disord. 2017;12:25. doi: 10.1186/s13013-017-0133-z

5. Milhorat TH, Johnson RW, Milhorat RH, et al. Clinicopathological correlations in syringomyelia using axial magnetic resonance imaging. Neurosurgery. 1995 Aug;37(2):206-13. doi: 10.1227/00006123-199508000-00003

6. Faillot M, Morar S, Delphine S, et al. Prospective Follow-up of Intramedullary Slitlike Cavities: A Consecutive Series of 48 Patients. Front Neurol. 2020;11:495. doi: 10.3389/fneur.2020.00495

7. Ciaramitaro P, Massimi L, Bertuccio A, et al. Diagnosis and treatment of Chiari malformation and syringomyelia in adults: international consensus document. On behalf of the International Experts Jury of the Chiari Syringomyelia. In: Consensus Conference. Milan; 2019. Vol. 43 (2). P. 1327-42. doi: 10.1007/s10072-021-05347-3

8. Klekamp J. How Should Syringomyelia be Defined and Diagnosed? World Neurosurg. 2018;111:e729-e745. doi: 10.1016/j.wneu.2017.12.156

9. Roser F, Ebner FH, Sixt C, et al. Defining the line between hydromyelia and syringomyelia. A differentiation is possible based on electrophysiological and magnetic resonance imaging studies. Acta Neurochir (Wien). 2010;152(2):213- 9. doi: 10.1007/s00701-009-0427-x

10. Mendelevich EG, Mikhailov MK, Bogdanov EI. Syringomyelia and Khiari malformation: monograph. Kazan: Medicine; 2002. 236 p. (In Russ).

11. Bogdanov EI. Clinical significance of subthreshold cerebellar tonsil ectopia into foramen magnum and Chiari malformation type 0. Burdenko's Journal of Neurosurgery. 2022;86(3):92-8 (In Russ.). doi: 10.17116/neiro20228603192

12. Mendelevich EG, Nurullina ChS. Hydromyelia: clinical and MR-tomographic features. Neurological Bulletin. 2017;49(3):106-7 (In Russ). doi: 10.17816/nb14101