Bacterial infections and tuberculosis
Bacterial abscesses directly involving the spinal cord are quite rare, being significantly less frequent than epidural abscesses. They typically occur against the background of other severe conditions. For example, abscesses caused by Staphylococcus aureus are frequently combined with meningitis and epidural inflammation. Risk factors include intravenous drug use and the presence of an intracardiac shunt with a right-to-left shunt.
On MRI, a bacterial intramedullary abscess appears as a lesion with a hyperintense center, surrounded by ring-like or peripheral enhancement and a zone of pronounced edema.
Tuberculous involvement can present in several forms:
- Tuberculous abscess: a rare phenomenon characterized by low signal on T1, high signal on T2, and a peripherally enhancing capsule.
- Tuberculous myelitis: manifests as hyperintensity on T2-weighted images; contrast enhancement may be present or absent.
- Intramedullary tuberculoma: most commonly localized in the thoracic spine. The MRI appearance includes hypointense ring-like enhancement, sometimes with a hypointense center on T2.
Viral and fungal myelitis
Viral lesions of the spinal cord are frequently associated with immunosuppression. Cytomegalovirus infection (CMV) is typical for organ transplant recipients. Varicella-zoster virus (VZV) is capable of causing myelitis in both immunocompetent and immunocompromised individuals. The MRI appearance in viral myelitis is generally nonspecific and demonstrates areas of increased signal within the spinal cord on T2-weighted scans.
Fungal infections of the spinal cord are caused predominantly by pathogens of the genera Aspergillus and Candida and also primarily affect immunocompromised patients.
Parasitic lesions
Parasitic myelitis is a rare phenomenon, most commonly represented by toxoplasmosis and cysticercosis.
Toxoplasmosis is almost always accompanied by concomitant involvement of brain structures. MRI reveals contrast-enhancing intramedullary lesions combined with extensive edema. This diagnosis should be suspected in AIDS patients who develop myelopathy and present with contrast-enhancing lesions in the CNS.
MRI semiotics of intramedullary cysticercosis depend on the stage of the disease:
- Early vesicular stage: a cyst with well-defined margins, showing high signal on T2. On T1, the cyst itself is hypointense, but a hyperintense scolex is visualized.
- Late (colloidal) stage: the cyst capsule thickens, acquiring high signal on T1 and low signal on T2. During cyst degeneration, peripheral contrast enhancement appears.
Briefly: answers to topical questions
What clinical neurological symptoms are characteristic of spinal cord toxoplasmosis?
For spinal cord toxoplasmosis, sources cite a clinical sign — developing myelopathy, especially in patients with AIDS (AIDS). Parasitic myelitis is rare; toxoplasmosis is almost always accompanied by brain involvement. Toxoplasmosis should be suspected in AIDS patients presenting with developing myelopathy and contrast-enhancing lesions in the brain and/or spinal cord. MRI findings in spinal cord involvement: contrast-enhancing intramedullary lesions with extensive spinal cord edema.
Class and exam questions
Spinal cord toxoplasmosis should be suspected in patients diagnosed with AIDS who exhibit signs of myelopathy and contrast-enhancing lesions in the brain and/or spinal cord.
Spinal cord toxoplasmosis should be suspected in patients diagnosed with AIDS who exhibit signs of myelopathy and contrast-enhancing lesions in the brain and/or spinal cord.
What does intramedullary cysticercosis look like in the early stage on MRI?
In the early vesicular stage, MRI reveals a well-delineated cyst that is hyperintense on T2. On T1-weighted images, the cyst is hypointense, while the scolex appears hyperintense.
Which viruses most frequently cause myelitis in immunocompromised individuals?
Viral myelitis in immunocompromised individuals is most frequently caused by cytomegalovirus and varicella-zoster virus.
What else to study on this topic
- Vascular malformations of the spinal cord
- Cavernous malformation of the spinal cord
- Acute spinal cord ischemia
- Immune-mediated and inflammatory spinal cord diseases
- Congenital malformations and cystic lesions of the spinal cord
- Intramedullary lipoma
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