What is syringomyelia?

Syringomyelia (also known as hydromyelia and hydrosyringomyelia) is a progressive condition where a cyst called a syrinx (made of a cavity full of cerebrospinal fluid (CSF) and lined with glial cells) forms in the spinal cord. A syrinx is most often found within the C2-T9 levels of the vertebrae [5]. Mine was largest from T7-T9 and extended through my cervical and into my lumbar spine.

Figure 1. My first spine MRI, which indicated a syrinx most prominent at 8 mm wide at the T7-T9 level (the white in the region overlaid with light purple- a regular MRI would show only black here). 

My MRI also showed mild prominence of the central canal beginning at C4-C5 that continued past the syrinx into the conus medullaris. 

Figure 2A. Sagittal (side) view of how a syrinx may look in the spinal cord

Figure 2B. Coronal view (cross-section) of how a syrinx may look in the spinal cord

What does cerebrospinal fluid have to do with Chiari I and syringomyelia?

Before discussing how syringomyelia is so closely related to Chiari I, I first want to explain cerebrospinal fluid flow so we know what role it plays in the entire process. Cerebrospinal fluid is formed in fluid-filled spaces (called the choroid plexus) of cavities in our brain called ventricles. CSF flows from the brain's lateral ventricles to the third ventricle, then the fourth ventricle, and ultimately into the subarachnoid space around the brain and spinal cord to remove waste products, deliver nutrients, and protect the brain and spinal cord by acting as a liquid cushion [2].

  Figure 3. CSF flow through the brain

Figure 4. Cerebrospinal fluid flow from the brain to the spinal cord. The four regions of the spinal cord are also included: cervical (green), thoracic (light blue), lumbar (purple), and sacral (pink)

There is still some debate about exactly how syringomyelia occurs in the context of Chiari I, with the current explanation being that due to the blockage of CSF flow at the foramen magnum, there is a pressure buildup first in the network of veins of the spine, which ultimately leads to cerebrospinal fluid accumulation in the spinal cord [7]. Another thing I wanted to note is that in the context of CM-I patients, syringomyelia, as well as Chiari I itself, should not significantly impact life expectancy [9]. There is a study of the life expectancy of patients with syringomyelia who also had severe comorbidities [1] that was causing some people online to worry that these life expectancy rates were the case for most syringomyelia patients, which is not true, so I wanted to clear that up here.

Syringomyelia is estimated to affect less than 50,000 people in the United States [3]. Which, for me, is crazy to think about. However, some studies have shown that the prevalence may be higher, potentially up to 35% of Chiari I patients [10]. Also, I obviously have it, so if you do too, you're not alone. 

How does a syrinx present?

Syringomyelia may not present with any symptoms and be found incidentally with an MRI. However, in many cases, patients are symptomatic and the presentation can depend on the vertebral level of the syrinx due to the nerves that extend from that part of the spinal cord and innervate certain regions of the body (depending on the dermatome or myotome affected as described in Figure 5). Some symptoms can include [6, 9, 10]:

• Headaches
• Loss of balance, lack of coordinated movements
• Chronic pain and/or sensory loss (numbness, tingling, itchiness, lack of pain/temperature sensation)
• Often presents in a cape-like distribution (if the cervical spine is affected)
• Diminished upper extremity reflexes, progressive upper extremity weakness- often first in the hands, then spreading to arms and shoulders (indicative of lower motor neuron damage)
• Spasticity or exaggerated reflexes in lower limbs (indicative of upper motor neuron damage)
• Loss of bladder and bowel control (if the sacral spine is affected)
  
  

Figure 5. Diagram of the body's dermatomes. Each level indicates the spinal nerve that supplies sensation to that area of the body. 

For example, a syrinx affecting the cervical spine (abbreviated "C") can lead to cape-like tingling, numbness, and/or burning pain. The diagram for the body's myotomes (spinal nerves that control the muscles of each level of the body) is similar but slightly different, so for simplicity, I have just included the dermatomal map here.

Treatment Options

The goal of treating syringomyelia is to slow the progression of the syrinx, decrease the pressure of the cyst, and improve CSF flow, though it can be difficult to predict precisely how much the symptoms of a syrinx will improve with treatment [11]. 

For patients with Chiari I, decompression surgery is most often recommended, with an even better prognosis if duraplasty is performed in addition to bony decompression. In patients with syringomyelia without Chiari I, options include shunt placement, drainage of the cyst, and destruction of any subarachnoid adhesions [4, 8].

Glossary

Bony decompression: surgical procedure where part of the back and bottom region of the skull and the back of the first vertebrae are removed to relieve pressure from the brain and spinal cord 

Cerebrospinal fluid (CSF): clear, protective, nutrient-rich fluid that flows around the brain and spinal cord

Comorbidities: the simultaneous presence of two or more medical conditions in a patient

Conus medullaris: the lower end of the spinal cord that tapers around the lumbar vertebrae

Dermatomes: areas of the skin that are innervated by a singular spinal nerve root- controls sensation 

    (Ex. the 6th cervical spinal nerve (C6) innervates the thumb, so if C6 is damaged, it can present with numbness, tingling, or burning pain in the thumb)

Duraplasty: surgical procedure where the dura (the protective covering of the spinal cord) is repaired or expanded

Glial cells: the most abundant cells in the nervous system, there are many types of glial cells and their main function is to support neurons 

Incidental finding: an extra discovery made during medical imaging not related to the original reason for the test

Mild prominence of the central canal: slightly expanded central spinal canal filled with CSF which can be caused by things like a syrinx

Myotomes: groups of muscles innervated by the same spinal nerve root- concerns movement/muscle control

    (Ex. the 6th cervical spinal nerve (C6) innervates wrist extension and elbow flexion, so if C6 is damaged, it can present with weak wrist extension and/or elbow flexion)

Prognosis: predicted estimate of how a disease or injury will affect the patient

Subarachnoid adhesions: scar tissue that forms as a result of inflammation in the subarachnoid space (like from a syrinx), which can impair CSF flow    

Subarachnoid space: the area of the brain and spinal cord where CSF flows, located between the arachnoid membrane and pia mater 

References

1. Chen CM, Huang WC, Yang YH, Huang SS, Lu KY. Factors affecting long-term mortality rate after diagnosis of syringomyelia in disabled spinal cord injury patients: a population-based study. Spinal Cord. 2020 Apr;58(4):402-410. doi: 10.1038/s41393-019-0363-4. Epub 2019 Oct 10. PMID: 31602006.
   
   
2. Czarniak N, Kamińska J, Matowicka-Karna J, Koper-Lenkiewicz OM. Cerebrospinal Fluid-Basic Concepts Review. Biomedicines. 2023 May 17;11(5):1461. doi: 10.3390/biomedicines11051461. PMID: 37239132; PMCID: PMC10216641.
   
   
3. Genetic and Rare Diseases Information Center. Syringomyelia: About the Disease [Internet]. U.S. Department of Health and Human Services; 2024 [cited 2024 Dec 2]. Available from: https://rarediseases.info.nih.gov/diseases/7725/syringomyelia
    
4. Holly LT, Johnson JP, Masciopinto JE, Batzdorf U. Treatment of posttraumatic syringomyelia with extradural decompressive surgery. Neurosurg Focus. 2000 Mar 15;8(3):E8. doi: 10.3171/foc.2000.8.3.8. PMID: 16676931.
   
   
5. Milhorat TH. Classification of syringomyelia. Neurosurg Focus. 2000 Mar 15;8(3):E1. doi: 10.3171/foc.2000.8.3.1. PMID: 16676921.
   
   
6. Saini L, Gunasekaran PK, Tiwari S, Krishna D, Laxmi V, Jindal P, Kumar P. Paroxysmal Neuropathic Pruritus in Patients With Chiari Malformation Type I: A Rare Phenotype. Pediatr Neurol. 2023 Mar;140:65-67. doi: 10.1016/j.pediatrneurol.2022.12.013. Epub 2022 Dec 27. PMID: 36652778.
   
   
7. Schijman E. History, anatomic forms, and pathogenesis of Chiari I malformations. Childs Nerv Syst. 2004 May;20(5):323-8. doi: 10.1007/s00381-003-0878-y. Epub 2004 Feb 5. PMID: 14762679.
   
   
8. Sgouros S, Williams B. Management and outcome of posttraumatic syringomyelia. J Neurosurg. 1996 Aug;85(2):197-205. doi: 10.3171/jns.1996.85.2.0197. PMID: 8755746.
   
   
9. Shenoy VS, Munakomi S, Sampath R. Syringomyelia. 2024 Mar 14. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 30725795.
   
   
10. Urbizu A, Toma C, Poca MA, Sahuquillo J, Cuenca-León E, Cormand B, Macaya A. Chiari malformation type I: a case-control association study of 58 developmental genes. PLoS One. 2013;8(2):e57241. doi: 10.1371/journal.pone.0057241. Epub 2013 Feb 21. PMID: 23437350; PMCID: PMC3578784.
    
    
11. Wetjen NM, Heiss JD, Oldfield EH. Time course of syringomyelia resolution following decompression of Chiari malformation Type I. J Neurosurg Pediatr. 2008 Feb;1(2):118-23. doi: 10.3171/PED/2008/1/2/118. PMID: 18352779; PMCID: PMC4294217.