MRI findings in classical multiple sclerosis
Diagnosis of spinal cord lesions is based on the evaluation of various magnetic resonance imaging sequences. Typical changes include the appearance of areas of demyelination.
- Sagittal projection (T2-WI): Multiple hyperintense lesions are clearly visualized on T2-weighted images (T2-weighted image). Most often, they have ill-defined margins (ill-defined hyperintense lesions). Such changes are frequently detected in the cervical spinal cord.
- Axial projection (T2-WI): Allows for the precise localization of the pathological process. Classic demyelinating plaques (demyelinating plaques) are characterized by a peripheral dorsal location within the spinal cord structure.
- Contrast evaluation: The administration of a contrast agent helps assess the activity of the process. On post-contrast T1-weighted images, demyelinating lesions (e.g., at the C3-C4 levels) often demonstrate incomplete contrast enhancement (incomplete enhancement).
Acute optic neuritis
Optic nerve involvement (Acute Optic Neuritis) is a frequent companion of demyelinating diseases. The MRI appearance depends on the age of the process.
- Acute phase: Non-specific thickening of the optic nerve sheath is observed. The nerves themselves produce a hyperintense signal on T2-WI. Pronounced swelling (swelling) and active contrast enhancement (enhancement) are also present.
- Follow-up: As acute inflammation subsides, optic nerve atrophy develops. At the same time, residual signal hyperintensity may persist for a long time.
Spinal cord involvement in neuromyelitis optica (NMO)
Neuromyelitis optica (Neuromyelitis Optica, NMO) requires strict differential diagnosis with multiple sclerosis. The main lesion pattern here is longitudinally extensive transverse myelitis (Longitudinally Extensive Transverse Myelitis, LETM).
Key MRI features of NMO:
- Presence of an intramedullary high-intensity signal on T2-WI that extends over more than three vertebral segments (the main difference from typical short plaques in MS).
- In 90% of cases, lesions actively enhance with contrast.
Specific patterns:
- «Shaggy ring enhancement» pattern (‘shaggy ring enhancement’): detected in 30% of patients in the cervical region, representing irregular ring-like enhancement.
- «Bright spotty lesions» (‘bright spotty lesions’): an extremely important differential diagnostic criterion on axial T2-WI, allowing NMO to be distinguished from multiple sclerosis.
During follow-up MRI in patients with NMO, central cavities (central cavities) may form, tissue defects can occur, and spinal cord atrophy may develop.
Brain changes in NMO
Brain involvement is detected in 40–60% of patients with neuromyelitis optica. The changes are specific in nature, directly related to the pathogenesis of the disease.
Typical lesion localization:
- Non-specific supratentorial white matter (White Matter, WM) lesions in the hemispheres.
- Diencephalic lesions located around the third ventricle and the cerebral aqueduct (cerebral aqueduct).
- Lesions in the dorsal brainstem directly adjacent to the fourth ventricle (the most significant zone being the area postrema, area postrema).
- Periventricular lesions around the lateral ventricles.
- Unilateral or bilateral involvement of the corticospinal tracts.
Pathogenetic connection: The strict localization of periventricular changes (around the 3rd and 4th ventricles, in the periaqueductal region) is not accidental. On MRI, these high-signal zones precisely correspond to brain areas where the highest concentration of aquaporin protein (aquaporin), which is the main target of autoantibodies in NMO, is physiologically present.
To distinguish NMO from MS on an axial T2-WI slice, look for «bright spotty lesions». If the lesion is longer than 3 spinal segments, it is LETM, which is typical for neuromyelitis optica.
Class and exam questions
Where are multiple sclerosis plaques most commonly located on axial MRI slices?
Classical multiple sclerosis is characterized by a peripheral dorsal localization of demyelinating plaques.
What happens to the optic nerve after acute neuritis?
Over time, optic nerve atrophy develops, but residual hyperintensity on MRI persists.
What is the main MRI criterion for spinal cord involvement in neuromyelitis optica?
This is longitudinally extensive transverse myelitis (LETM), in which the intramedullary hyperintense signal on T2-WI spans more than three vertebral segments.
Why are brain lesions in NMO located around the ventricles?
Periventricular zones (around the 3rd and 4th ventricles, as well as the cerebral aqueduct) contain the highest concentration of aquaporin, which is targeted in this disease.
What else to study on this topic
- Detailed analysis of the «shaggy ring enhancement» pattern
- Formation of central cavities in NMO
- Features of corticospinal tract involvement in neuromyelitis optica
- Area postrema: clinical and radiological significance
- Incomplete contrast enhancement on T1-WI: mechanisms of formation
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