Syringomyelia

Treatment and prognosis of syringomyelia

Although there are no conservative methods to eliminate the syrinx, modern neurosurgery offers several options for surgical intervention. All major surgical methods show comparable efficacy: they allow achieving collapse of the spinal cord cavity and maintaining this result in 70–80% of clinical cases.

Main surgical methods include:

• Foramen magnum decompression.
• Syringo-subarachnoid, peritoneal, or pleural shunting.
• Lumboperitoneal shunting.

Interestingly, the prognosis of the disease has its paradoxes. The clinical outcome for the patient and the further spread of spinal cord cavitation, which we assess on follow-up tomograms, do not depend on whether the formed cavity remains in a collapsed state after treatment. This dictates the need for a thorough differential diagnosis with other pathologies.

Motor neuron disease (MND)

When performing neuroimaging of spinal cord pathologies, it is necessary to remember a group of progressive neurodegenerative diseases—motor neuron diseases (MND, Motor Neurone Disease). They affect the upper and lower central motor neurons.

Classification based on the level of involvement:

1. Amyotrophic lateral sclerosis (ALS): involves both upper and lower motor neurons. This is the most common form (known as Lou Gehrig's disease). It is most commonly sporadic, but in 5–10% of cases, autosomal dominant inheritance is observed.
2. Progressive muscular atrophy (PMA): isolated involvement of only lower motor neurons.
3. Primary lateral sclerosis (PLS): isolated involvement of only upper motor neurons.
4. Progressive bulbar palsy (PBP): a rare form involving bulbar muscles (secondary to degeneration of the motor nuclei of the medulla oblongata).

Clinical and MRI presentation of ALS: Patients experience mixed weakness and atrophy of the intrinsic hand muscles, combined with hyperreflexia, ataxia, and fasciculations. Over time, dysarthria, dysphagia, and respiratory failure develop, leading to a fatal outcome. MRI is most commonly used to exclude multiple sclerosis or radiculopathy. In positive cases, axial T2-weighted images may show symmetrical hyperintensity in the lateral funiculi (reflecting histological involvement of the corticospinal tracts).

Spinal muscular atrophy (SMA)

SMA (Spinal Muscular Atrophy) is a large group of genetically determined neuromuscular diseases. Unlike syringomyelia, the pathogenesis lies in the loss of lower motor neurons in the anterior horns of the spinal cord, strictly without involvement of sensory or pyramidal tracts.

All forms of SMA are inherited in an autosomal recessive manner. Genetic defects for types I–III are localized on chromosome 5q11.2–13.3.

Types of SMA (by age of onset):

• Type I: acute infantile form.
• Type II: chronic infantile (intermediate) form.
• Type III: juvenile form.
• Type IV: adult form.

The MRI presentation in SMA is nonspecific. The radiologist may detect only focal atrophy of the cervical spinal cord. Sometimes a small area of hyperintensity on T2-weighted images is visualized, which is visually similar to focal myelomalacia of another etiology (e.g., post-traumatic).

Spinocerebellar degenerations and Friedreich ataxia

Spinocerebellar ataxia (Spinocerebellar Ataxia) is a collective term for hereditary progressive diseases manifesting as impaired coordination of hands, speech, eyes, and ataxia. Classification is based on genesis and inheritance type. The most common autosomal dominant form is spinocerebellar degeneration, and the autosomal recessive form is Friedreich ataxia (Friedreich Ataxia).

In Friedreich ataxia, a mutation in the frataxin gene leads to a cascade of degenerative changes. Large primary neurons in the dorsal root ganglia and sensory fibers of the peripheral nerves are lost. The posterior and lateral funiculi of the spinal cord are affected, and the dentate nucleus of the cerebellum atrophies.

MRI semiotics of Friedreich ataxia:

• Pronounced thinning of the cervical enlargement of the spinal cord (especially affecting the anteroposterior dimension).
• Presence of intramedullary hyperintensity on T2-weighted images (symmetrically within the posterior or lateral funiculi).

Subacute combined degeneration of the spinal cord

This condition, also known as funicular myelosis (Subacute Combined Degeneration), is a progressive myelopathy associated with nutritional or secondary vitamin B12 deficiency (due to malabsorption, gastrectomy, nitrous oxide abuse, or strict vegetarianism). Pathogenetically, the lateral and posterior funiculi are affected.

Key MRI features:

• Linear hyperintensity in the dorsal regions on sagittal T2-weighted images.
• Axial slices reveal bilateral dorsal lesions—the classical "inverted V sign".
• Typical localization of changes is at the C2–C5 segment levels.
• Spinal cord edema is usually absent, but contrast enhancement may occur.
• Changes may completely or partially regress with treatment (however, clinical improvement is often only partial).

Important to remember: in some cases, the MRI presentation in funicular myelosis may remain completely normal.

Class and exam questions

What else to study on this topic

• Surgical shunting techniques for the spinal cord
• Genetics of autosomal recessive ataxias
• The role of the frataxin gene in neurodegeneration
• Differential diagnosis of focal myelomalacia

Other topics in the "Spine" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.