Clinical diagnosis
Case 149
【Progress】
Regrettably, we do not have enough staff to supply spinal surgery. Then, he was introduced to university hospital.
【Discussion】
Cerebrospinal fluid (CSF) is produced by choroid plexus in bilateral lateral ventricles, third ventricle and fourth ventricle. CSF outflows from lateral ventricle to third ventricle via Monro foramen (interventricular foramen) and from third ventricle, it outflows to forth ventricle via aqueduct. Further from fourth ventricle it outflows to subarachnoid space of foramen magnum via Luschka and Magendie foramen. Very small amount of CSF descends to central canal in the spinal cord. After CSF flows around in the whole subarachnoid space, CSF in the skull inflows to venous sinusoids via arachnoid granulation, and CSF in the spine inflows to the venous plexus surrounding the spinal cord. CSF in the central canal might pass directly into myelin and finally mixes with lymph fluid (1).
Central canal forms long elliptical in shape throughout most of the spinal cord. The distal end of the central canal is dilated like outpouchings and then, closed in human (2, 3). In the axial cutting surface, central canal situates in the almost midpoint of H shaped white matter of neural tract. The sensory nerve tract (lateral spinothalamic tract) related to pain or temperature lies most near the central canal (4). Then, the larger of central tract causes compression more to this sensory tract. In our case, his symptom began from the loss of temperature and pain sensations.
Further, the recent studies revealed CSF flow in the arachnoid space of brain and spinal cord comes from perivascular space based on the arterial pulsations (5, 6). Cisterna magna is believed to the pressure absorber from the arterial pulsations coming from ventricles (5). As a matter of course, arterial pressure affects the CSF flow in the central canal. When cerebellar tonsil descends to the cisterna magna and block the cisterna magna in case of Chiari I type, arterial pulsations affect directly the central canal, inducing the gradual dilatation of the central canal and eventually leading to the formation of syringomyelia (5). Similarly, when arachnoiditis causes adhesion inducing occlusion or stenosis of spinal arachnoid space, arterial pulsations directly more to the central canal, leading to the formation of syringomyelia (6).
Chiari malformation is believed to be caused by small posterior cranial fossa which occupies cerebellum and brain stem (1). This situation induces that part of the cerebellum is pushed downward through foramen magnum. Chiari malformation is categorized into two types; Type I, downward displacement of cerebellar tonsil : Type II downward displacement of cerebellar tonsil and brain stem associated with (myelo-)meningocele (1). In our case, neck MRI showed the downward displacement of cerebellar tonsil without myelomeningocele, indicative of Chiari Type I syringomyelia.
【Summary】
We present a sixteen year-old boy suffering from sensory lowering of left upper extremity and neck. Neck MRI showed the descending displacement of cerebellar tonsil and marked dilatation of the central duct, compatible diagnosis of spinal syringomyelia with Chiari I type malformation. It is borne in mind that central canal in the spinal cord is a closed syringe-like duct. CSF produced by choroid plexus outflows to subarachnoid space of foramen magnum via Luschka and Magendie foramen with assistance of arterial pulsations. When cerebellar tonsil displaces downward, it blocks the outflow of CSF into spinal arachnoid space, inducing the arterial pulsations gradually dilatating the central duct, eventually leading to spinal syringomyelia. Similarly, arachnoiditis which causes adhesion and occlusion of spinal arachnoid space induces the formation of syringomyelia. Chiari malformation is categorized into two types; Type I, downward displacement of cerebellar tonsil: Type II downward displacement of cerebellar tonsil and brain stem associated with myelomeningocele.
【References】
1.Saker E, et al. The Human Central Canal of the Spinal Cord: A Comprehensive Review of its Anatomy, Embryology, Molecular Development, Variants, and Pathology. Cureus. 2016 Dec; 8(12): e927.
2.Pearson AA , et al. Observations on the caudal end of the spinal cord. Am J Anat. 1971;131:463–469.
3.Storer KP, et al. The central canal of the human spinal cord: a computerised 3-D study, NR. J Anat. 1998;192:565–572.
4.Crosby EC, et al. Anatomy of the Nervous System. MacMillan. New York, NY: MacMillan Company; 1962. Basic and Clinical Anatomy of the Nervous System.
5.Bilston, L E, et al. Arterial pulsation-driven cerebrospinal fluid flow in the perivascular space: a computational model. Comput. Methods Biomech. Biomed. Engin 2003; 6, 235–241.
6.Rennels, ML, et al. Evidence for a paravascular fluid circulation in the mammalian central nervous system, provided by the rapid distribution of tracer protein throughout the brain from the subarachnoid space. Brain Research 1985; 326: 47–63.
7.Chang HS, et al. Hypothesis on the pathophysiology of syringomyelia based on simulation of cerebrospinal fluid dynamics. J Neurol Neurosurg Psychiatry. 2003;74:344–347.
8.Chang HS, et al. Theoretical analysis of the pathophysiology of syringomyelia associated with adhesive arachnoiditis. J Neurol Neurosurg Psychiatry 2004;75:754–757.
2019.6.19