Neuromyelitis optica (Devic's disease)
Neuromyelitis optica is a severe autoimmune disease characterized by combined involvement of the visual pathways and the spinal cord. Comprehensive magnetic resonance imaging reveals a number of pathognomonic signs:
- Brain: Axial FLAIR slices demonstrate bilateral and symmetric signal hyperintensity in the hypothalamus.
- Optic nerves: Thin-slice coronal T2-weighted images show marked edema and a hyperintense signal in the left half of the optic chiasm (chiasma opticum). Similar hyperintense changes affect the intracanalicular segment of the optic nerve (nervus opticus).
- Spinal cord (T2-WI): Sagittal scans of the cervicothoracic region show a poorly defined hyperintense signal. The lesion is longitudinally extensive, completely involving the entire cervical and upper thoracic spine. The spinal cord itself is moderately thickened at this level due to marked edema. Axial scans reveal a key marker of extensive transverse myelitis — the pathological lesion occupies more than 2/3 of the cross-sectional area of the spinal cord.
- Contrast enhancement: Post-contrast sagittal T1-weighted images show focal, patchy (heterogeneous) contrast enhancement directly within the spinal cord lesion.
Systemic lupus erythematosus (SLE) and vascular pathologies
In systemic lupus erythematosus, spinal cord involvement has specific localization features and MRI patterns:
- Lesions are most frequently located in the conus medullaris (conus medullaris), although they can also be detected in other regions, such as the cervical spine.
- On T2-weighted images (in both sagittal and axial projections), the lesion occupies the majority of the cross-sectional area of the medullary cone.
- T1-weighted imaging with intravenous contrast administration demonstrates only mild contrast enhancement within the pathological lesion.
Among vascular diseases of the spinal cord, spinal dural arteriovenous fistula (SDAVF) stands out. This is the most common pathology in this group, accounting for over 80% of all spinal arteriovenous malformations. The fistula is localized in the dura mater (dura mater spinalis), typically situated in close proximity to the nerve root sleeve.
Guillain-Barré syndrome (GBS)
Guillain-Barré syndrome is an acute immune-mediated polyneuropathy. The trigger for the disease is most commonly a preceding viral infection, after which the body begins to produce antibodies that cross-react pathologically with the myelin sheath of the peripheral nervous system.
The clinical presentation includes typical areflexia and ascending paralysis — symmetric muscle weakness starting in the feet and hands, which then steadily progresses upward toward the trunk over several days. The disease may be accompanied by sensory loss or occur without it.
Prognosis of the disease:
- About 80% of patients recover completely or nearly completely within several weeks.
- 10% of patients retain persistent symptoms (a relapsing-remitting course is possible).
- In another 10% of cases, a life-threatening condition develops due to severe respiratory muscle involvement.
The basis of diagnosis includes the clinical picture, electroneuromyography, and cerebrospinal fluid analysis. MRI serves as a useful adjunct: it reveals nonspecific thickening and contrast enhancement of the nerves, which is also seen in other inflammatory disorders.
Chronic inflammatory demyelinating polyneuropathy
This condition is an immune-mediated symmetric sensorimotor disorder. It is considered the chronic equivalent of the acute form of Guillain-Barré syndrome. The main differences in CIDP are an insidious onset, a slowly progressive or relapsing course, and an extremely rare association with a preceding infection. Treatment is based on immunosuppressive or immunomodulatory drugs.
MRI diagnostics in CIDP include assessing the state of nerves and muscles:
- Nerves: The picture is nearly identical to Guillain-Barré syndrome (thickening and contrast enhancement of the nerve roots are observed).
- Acute and subacute muscle denervation: On fluid-sensitive sequences (T2-WI or STIR), affected muscles demonstrate a characteristic hyperintense signal.
- Chronic muscle denervation: Muscle atrophy and fatty infiltration develop. Visually, this manifests as a high signal on T1-weighted images and a loss of overall muscle tissue volume.
Depending on the stage of the disease, both types of muscle changes may be present simultaneously on MRI.
Briefly: answers to topical questions
What MRI patterns are characteristic of a spinal dural arteriovenous fistula?
Spinal dural arteriovenous fistula is characterized by signs of venous congestion and the presence of pathologically dilated vessels. MRI reveals the following patterns:
- Dilated veins — visualized on T2-WI as tortuous areas of signal void (flow voids) that enhance with contrast medium.
- Venous congestion — manifests as edema (poorly demarcated hyperintense signal on T2-WI with spinal cord thickening).
- Hemorrhage — signal intensity varies depending on the age of the blood (subarachnoid hemorrhage may be present).
What vascular pathologies of the spinal cord are detected by MRI?
MRI detects a wide spectrum of vascular diseases and spinal cord infarctions. The main pathologies identified include:
- Spinal dural arteriovenous fistula (Spinal Dural Arteriovenous Fistula) — the most common vascular malformation.
- Spinal arteriovenous malformation — includes perimedullary, intramedullary, and extradural types.
- Spinal cord cavernous malformation (Spinal Cord Cavernous Malformation) — a vascular malformation consisting of sinusoid-like vessels.
- Acute spinal cord ischemia (Acute Spinal Cord Ischaemia) — manifests as a hyperintense signal on T2-WI.
To memorize the picture of Devic's disease: the "Two D's and 2/3" rule — Bilateral hypothalamic involvement, Long (longitudinally extensive) myelitis, lesion occupies >2/3 of the cross-section.
Class and exam questions
How to distinguish Devic's disease from other spinal cord lesions on MRI?
In neuromyelitis optica, the lesion is longitudinally extensive (involving the entire cervical and upper thoracic regions), and on axial T2-weighted images, the lesion occupies more than 2/3 of the cross-sectional area of the spinal cord.
What muscle changes are visible on MRI in polyneuropathies?
In acute denervation, a hyperintense signal is visible on T2-WI or STIR. In the chronic stage, a high signal is noted on T1-WI due to fatty infiltration, along with marked loss of muscle volume.
Where are the lesions most frequently localized in systemic lupus erythematosus?
Lesions may be located in the conus medullaris, occupying the majority of its cross-sectional area, as well as in the cervical spinal cord.
What is the difference in the clinical onset of GBS and CIDP?
Guillain-Barré syndrome has an acute onset, most often following a viral infection, with rapid ascending paralysis. CIDP is characterized by an insidious onset, slow progression, and no association with a preceding infection.
What else to study on this topic
- The significance of cerebrospinal fluid (CSF) analysis in suspected Guillain-Barré syndrome
- Mechanisms of antibody cross-reaction with peripheral nerve myelin
- Anatomy of nerve root sleeves and precise localization of dural fistulas
- Clinical application of electroneuromyography in the differential diagnosis of polyneuropathies
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