MRI findings in spinal tuberculosis
When analyzing sagittal T2-weighted images (T2-WI) in patients with spinal tuberculosis, multiple intramedullary lesions (intramedullary lesions) are visualized. Their signal intensity may vary, but an extensive area of hyperintense signal forms around them, corresponding to pronounced spinal cord edema (spinal cord oedema).
The most specific diagnostic sign is the structure of the lesion itself. A characteristic tuberculous granuloma (tuberculous granuloma) on T2-WI demonstrates central hypointensity. Such a picture, for example at the thoracic vertebrae level (T5-T6), is a typical marker of a specific process.
Complications and the role of contrast enhancement
The pathological process can lead to the formation of extensive collections. On T2-WI, they produce an intermediate-intensity signal. Such collections are often located dorsally (posteriorly) to the spinal cord and can extend over a considerable distance — from the lower cervical region all the way down to the dural sac.
Consequences of an intradural collection (intradural collection):
- Effacement of the intrathecal space where cerebrospinal fluid (CSF, CSF) circulates.
- Pronounced anterior compression of the spinal cord.
- Confirmation of the process localization on axial T2 scans.
When using post-contrast images, the picture is complemented. The intradural collection and intrathecal spaces actively enhance with contrast, indicating its leakage into the CSF. Pronounced leptomeningeal enhancement (leptomeningeal enhancement) is also recorded, especially along the ventral surface. Small intramedullary tuberculomas (tuberculomata) are also capable of actively accumulating the contrast agent.
Related pathologies: Lipomyelomeningodysplasias
Within the study of spinal pathologies, lipomyelomeningodysplasias (lipomyelomeningodysplasias) are also distinguished. This is a wide spectrum of developmental anomalies ranging from a low-lying conus medullaris (conus medullaris) with virtually no lipoma to giant lipomatous masses involving all spinal structures and subcutaneous tissue.
In adults, this pathology is often disguised as "occult spinal dysraphism" (occult spinal dysraphism), manifesting only as back pain and mild neurological symptoms. Unlike myeloceles (myeloceles), Chiari malformation (Chiari malformation) accompanies this anomaly in only 6% of cases.
Diagnostic and surgical features:
- Imaging: MRI is the optimal method, while ultrasound is recommended in children.
- Anatomy: In 80% of cases, the spinal cord terminates abnormally low — at the L3 level or below. It may be tethered (tethered) to the dorsal surface of the dura mater (dura), merging with adipose tissue.
- Surgical nuance: The filum terminale (filum terminale) appears thickened, but it contains a large volume of functional neural tissue (nerve roots). It is strictly forbidden to transect it during surgery.
Diastematomyelia
Another important anomaly is diastematomyelia (diastematomyelia) — the pathological splitting of the spinal cord into two unequal hemicords (hemicords).
Each of the formed hemicords has an absolutely autonomous anatomy:
- Its own central canal (central canal).
- Its own anterior spinal artery (anterior spinal artery).
- Gives rise exclusively to ipsilateral (same-side) spinal nerve roots.
This anomaly can affect any level of the spinal column, down to the filum terminale.
Briefly: answers to topical questions
How does lipomyelomeningodysplasia differ from myelocele in the context of the frequency of concomitant Chiari malformation?
In lipomyelomeningodysplasia, concomitant Chiari malformation (Chiari malformation) is significantly less common than in myelocele. This pathology represents an occult spinal dysraphism, ranging from low positioning of the conus medullaris to massive lipomatous formations.
| Abnormal | Frequency of concomitant Chiari malformation |
|---|---|
| Lipomyelomeningodysplasia | Present in only 6% of cases |
| Myelocele (myeloceles) | Occurs significantly more frequently |
What classic radiological signs are characteristic of tuberculous spondylitis in the early stages?
In the earliest (acute) stages of tuberculous spondylitis, the radiograph may remain within normal limits. As it progresses to the subacute phase, the following classic radiological signs appear:
- Areas of lucency (bone lucency) — detected directly in the bone tissue of the affected vertebral bodies.
- Changes in the endplates (endplates) — their destruction leads to a decrease in intervertebral disc height (however, tuberculosis is characterized by late preservation of the disc).
- Cold abscess (cold abscess) — visualized as paraspinous soft tissue thickening (widening of the shadow) on anteroposterior views.
By what pathways do Mycobacterium tuberculosis spread and penetrate into the vertebral bodies?
Mycobacteria tuberculosis penetrate into bone tissue predominantly hematogenously from the primary infection site. The spread of the pathogen and involvement of vertebral bodies occurs in the following sequence:
- Primary focus — the infection is carried by the bloodstream from the lungs, lymph nodes, or urogenital tract.
- Bone fixation — mycobacteria settle in the bone marrow (usually in the anterior parts of the vertebral bodies), where primary osteitis forms.
- Subligamentous spread — the process spreads beneath the longitudinal ligament (longitudinal ligament), involving adjacent vertebrae.
- Hematogenous seeding — isolated "skip lesions" (skip lesions) can form at distant levels.
What types of tissue can the pathological septum dividing the spinal cord in diastematomyelia consist of?
In diastematomyelia, the pathological septum dividing the spinal cord into two halves can consist of several types of supportive tissue. Depending on the type of malformation, the spur (spur) can be:
- Bone tissue — inside such a septum, an MRI signal from bone marrow may be detected.
- Cartilaginous tissue — forms an isolated cartilaginous spur.
- Osteocartilaginous tissue (osteocartilaginous spur) — a mixed variant of septum structure.
This structure usually originates from an abnormal vertebral arch and is located extradurally on the midline.
To remember the granuloma sign on T2: "A dark center in a bright sea" (hypointense center of the granuloma against the background of hyperintense spinal cord edema).
Class and exam questions
What does a tuberculoma look like on T2-WI?
On T2-weighted images, a tuberculous granuloma typically demonstrates central hypointensity (dark signal), which is often surrounded by a zone of hyperintense edema.
Do intramedullary tuberculomas enhance with contrast?
Yes, small intramedullary tuberculomas actively take up the contrast agent. Contrast is also accumulated by the leptomeninges and intradural collections.
What is the main surgical danger in lypomyelomeningodysplasia?
The visually thickened filum terminale in this pathology contains many functional nerve roots, so it must not be transected surgically to avoid causing neurological deficit.
What is diastematomyelia?
This is the splitting of the spinal cord into two hemicords, each of which has its own central canal and spinal artery, but gives rise only to roots on its own side.
What else to study on this topic
- Mechanisms of formation of intradural collections in tuberculosis.
- Differential diagnosis of hypointense lesions on T2-WI.
- Leptomeningeal enhancement patterns.
- Association of lypomyelomeningodysplasia with tethered cord syndrome.
- Embryological basis of diastematomyelia development.
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