The semiological analysis of myelopathies in MRI relies on identifying ten key elements that guide the diagnosis (Fig1):

1. Spinal Cord Signal on T2: The presence of a hyperintense signal in the spinal cord is a sign of intrinsic damage, often the first indication of an underlying pathology.
2. Atrophy or Hypertrophy of the Spinal Cord: Atrophy typically indicates a chronic or degenerative lesion, while hypertrophy may suggest a tumor or inflammatory infiltration.
3. Distribution of the Lesion: The focal (unifocal) or diffuse (multifocal or extended) spread of lesions helps differentiate the causes.
4. Semiology in Axial Cut: Abnormalities in cross-sectional images, such as central or peripheral involvement, direct attention to specific etiologies.
5. Extent of Lesion in Length: Lesions affecting more than two vertebral segments suggest inflammatory or vascular causes, while shorter lesions are often mechanical.
6. Spinal Cord Enhancement: Focal or diffuse enhancement post-contrast can indicate inflammation, ischemia, or a tumor.
7. Perimedullary Enhancement: Seen in certain vascular malformations or infectious processes.
8. Abnormal Intraspinal Elements: The presence of cysts, tumors, or mechanical compressions is crucial.
9. Conus Medullaris Involvement: Localized hyperintensities in this area suggest specific causes like myelitis or myxopapillary tumors.
10. Degenerative Lesions Adjacent: These help identify a mechanical origin due to compression.

This semiological approach, rigorously applied, is a valuable tool for distinguishing myelopathies and refining diagnostic hypotheses.

1. Cervical Spondylotic Myelopathies (Fig2)

Cervical spondylotic myelopathies result from chronic mechanical compression of the spinal cord, often due to degenerative changes in the cervical spine such as facet joint osteoarthritis, herniated discs, or ligament hypertrophy. They are a common cause of myelopathy in elderly patients.

Specific MRI Characteristics

1.  Hyperintensity in T2: Spinal cord shows a hyperintense signal in T2 sequence at the site of maximum compression, indicating edema or myelomalacia, depending on compression duration.
2.  Extrinsic Compression in T1 and T2: MRI shows reduced subarachnoid space due to disc protrusion or ligament hypertrophy, causing significant canal narrowing, visible in sagittal and axial cuts.
3. Associated Degenerative Changes: Includes anterior osteophytes, disc dehydration in T2, and sometimes foraminal stenosis visible in axial sequences.
4. No Contrast Enhancement: Unlike inflammatory or tumor lesions, cervical spondylotic myelopathies do not enhance after gadolinium injection, except in complications like inflammation.

2. Vascular Myelopathies (Fig3)

Vascular myelopathies result from altered spinal cord perfusion, typically due to acute or chronic ischemia. They may be associated with arteriovenous malformations (AVMs), arterial or venous thrombosis, or repeated microtrauma causing vascular compression.

Specific MRI Characteristics

1. Localized Hyperintensity on T2: Lesions are often seen in the anterior or lateral columns, indicating ischemia in areas supplied by the anterior spinal artery.
2. Extensive Longitudinal Involvement (>2 Vertebral Segments): The lesions often extend over several levels, typical of ischemic myelopathies.
3. Diffusion Restriction in DWI Sequence: Hyperintensity with restricted ADC is a key sign of acute ischemia.
4. Perimedullary Vascular Anomalies: AVMs are visible as "flow voids" (areas without signal in T2), typical of dural fistulas.
5. Absence of Specific Contrast Enhancement: Unlike inflammatory myelitis, vascular myelopathies generally do not show diffuse contrast enhancement unless complications arise.

3. Inflammatory Myelopathies

Inflammatory myelopathies include autoimmune conditions such as multiple sclerosis (MS), neuromyelitis optica (NMO), or post-infectious myelitis. These are characterized by inflammatory hyperintensities in the spinal cord, often associated with brain lesions in systemic pathologies.

Specific MRI Characteristics

1. Well-Defined Hyperintensity on T2: Lesions are often unifocal on T2, typically affecting the cervical or upper thoracic spinal cord.
2. Extent of Lesion:Typically spans less than two cervical vertebrae (<2 CV), with unilateral or asymmetrical involvement.
3. Asymmetric or Hemicord Involvement: Most often observed in multiple sclerosis.

4. Contrast Enhancement:Active lesions often demonstrate nodular or annular enhancement following gadolinium administration.

Associated Brain Lesions:In conditions like MS, typical periventricular lesions may also be present on brain MRI

4. Tumor-Induced Myelopathies (Fig5/6/7)

Tumor-induced myelopathies arise from intramedullary (ependymoma, astrocytoma) or extramedullary (meningioma, metastasis) tumors. They manifest as compression, infiltration, or progressive degeneration of the spinal cord.

Specific MRI Characteristics

1. Spinal Cord Hypertrophy: Intramedullary tumors cause focal or diffuse enlargement of the spinal cord, visible in both axial and sagittal cuts.
2. T2 Hyperintensity with Enhancement: Tumors typically show intense, well-defined enhancement after gadolinium injection, sometimes associated with cysts or intramedullary hemorrhage.
3. Lesion Extension over Multiple Segments: Tumor lesions often extend across multiple levels, with a mass effect visible on surrounding tissues.
4. Differentiation by Tumor Type:

• Ependymoma: Centrally located in the spinal cord with homogeneous enhancement and frequent cysts.
• Astrocytoma: More infiltrative, often eccentric, with heterogeneous enhancement.

5. Infectious Myelopathies (fig8)

Infectious myelopathies are caused by bacterial, viral, fungal, or parasitic pathogens. These conditions may result from direct spinal cord infection or paraneoplastic inflammation. Tuberculosis, Lyme disease, and Mycoplasma infections are common examples.

Specific MRI Characteristics

1. Diffuse, Nonspecific T2 Hyperintensity: Infectious lesions often cause extensive T2 hyperintensity, associated with spinal cord enlargement.
2. Meningeal or Perimedullary Enhancement: Bacterial infections, like tuberculosis, often show focal or diffuse meningeal enhancement, indicating inflammation or epidural abscess.
3. Adjacent Anomalies: Osteo-articular infections (e.g., spondylodiscitis) can be associated with adjacent vertebral lesions, visible as T1 hypointensity and T2 hyperintensity.
4. Cysts or Abscesses: Fungal or parasitic infections may produce cystic masses with peripheral enhancement after gadolinium injection.

6. Degenerative Myelopathies (Fig9)

Degenerative myelopathies result from chronic processes that lead to progressive degeneration of the spinal cord. These include advanced cervical spondylosis and chronic metabolic conditions like vitamin B12 deficiency.

Specific MRI Characteristics

1. Subtle T2 Hyperintensity in Posterior Columns: Typical of metabolic myelopathies, such as vitamin B12 deficiency, where demyelination primarily affects the posterior columns.
2. Diffuse Spinal Cord Atrophy: Seen in chronic, degenerative myelopathies, indicating irreversible damage.
3. Absence of Contrast Enhancement: Unlike inflammatory or infectious lesions, degenerative myelopathies do not exhibit post-contrast enhancement.

7. Traumatic Myelopathies

Traumatic myelopathies occur following acute spinal cord injury due to direct trauma or vertebral instability. These include spinal cord contusions and secondary ischemic lesions.

Specific MRI Characteristics

1. Localized T2 Hyperintensity: focal T2 hyperintensities at the site of impact, often with associated perimedullary edema.
2. Chronic T1 Hypointensity: Older lesions show cavitation with T1 hypointensity corresponding to myelomalacia.
3. Associated Complications: Vertebral fractures or epidural hematomas are frequently visible, causing extrinsic compression.

8. Acute Spinal Cord Ischemia Syndrome (Fig10/11/12)

Spinal cord ischemia, also known as spinal cord infarction, is a rare condition characterized by the sudden disruption of blood supply to the spinal cord, leading to significant neurological deficits and often a poor prognosis.

Imaging Features

1. Central T2 Hyperintensity: MRI T2 sequences show a central hyperintensity spanning multiple vertebral segments, often thoracic, indicating ischemic damage.
2. T1 Isointensity or Hypointensity: T1-weighted images may show an isointense or slightly hypointense signal corresponding to the affected region.
3. Diffusion Restriction
4. Absence of Post-Contrast Enhancement

Note:

• Early MRI may appear normal in the initial stages of spinal cord ischemia. Repeat imaging in the acute phase is often necessary for diagnosis.
• Over time, spinal cord atrophy develops as a chronic sequela, further confirming the ischemic nature of the injury.