Polyneuropathy

Guillain-Barré syndrome (acute form)

An acute immune-mediated polyneuropathy that in most cases manifests after a recent viral infection. The pathogenesis is based on the production of autoantibodies attacking the myelin sheath of peripheral nervous system structures due to cross-reactivity.

Clinically, the disease presents with typical areflexia and ascending paralysis. Symmetrical muscle weakness starts in the distal extremities (hands and feet) and over several days steadily spreads upward, involving the trunk. The process may be accompanied by sensory loss, although this symptom is not always present.

The prognosis of the disease is variable:

• ~80% of cases: complete or nearly complete recovery within several weeks.
• ~10% of cases: persistent neurological deficit (remitting or relapsing course is possible).
• ~10% of cases: life-threatening conditions due to involvement of the respiratory muscles.

The baseline diagnosis is established based on the clinical picture. Electroneuromyography and cerebrospinal fluid analysis are used for confirmation.

Chronic inflammatory demyelinating polyneuropathy (CIDP)

CIDP (Chronic Inflammatory Demyelinating Polyneuropathy, CIDP) is a chronic equivalent of the acute form of Guillain-Barré syndrome. This symmetrical sensorimotor disorder is immune-mediated and characterized by a progressive or relapsing course.

Key differences from the acute form:

• Insidious (insidious) onset.
• Slowly progressive course.
• History of preceding infection is extremely rare.

The main treatment vector for CIDP is aimed at suppressing the pathological immune response using immunosuppressive or immunomodulatory therapy.

MRI semiotics of polyneuropathies and muscle denervation

Magnetic resonance imaging serves as an important adjunct in diagnostics. In Guillain-Barré syndrome and CIDP, thickening of the nerve roots and intense contrast enhancement are visualized. In CIDP, the nerves are significantly thickened, showing a hyperintense signal on fat-suppressed (FS) T2-weighted images. On post-contrast T1-weighted images, diffuse enhancement of both intradural and extradural nerve portions is noted.

Special attention is paid to concomitant muscle changes (e.g., in the psoas [psoas] and pelvic muscles), which reflect the stage of denervation:

1. Acute and subacute denervation: manifests as asymmetry, hyperintense signal on fluid-sensitive sequences (T2-WI or STIR), and contrast enhancement indicating edema.
2. Chronic denervation: characterized by loss of muscle volume (atrophy) and fatty infiltration. On MRI, this appears as high signal on T1-WI.

Note: Depending on the duration of the disease, a single patient may simultaneously exhibit both types of muscle changes.

Differential diagnosis: vascular and systemic lesions

When evaluating the MRI picture of the spinal cord and roots, it is important to rule out other pathologies capable of causing a similar neurological deficit.

• Systemic lupus erythematosus: can affect the medullary conus (conus medullaris) or cervical region. On T2-WI, the lesion occupies a large part of the spinal cord cross-section, while on contrast-enhanced T1-WI it shows only weak contrast enhancement.
• Spinal dural arteriovenous fistulas (SDAVF): account for over 80% of all spinal vascular malformations. They are localized in the dura mater, often near the root sleeve. They cause symptoms due to venous congestion. MRI shows tortuous dilated perimedullary veins. For precise non-invasive shunt localization, 4D dynamic MR angiography (e.g., TWIST) is used, and for confirmation — digital subtraction angiography (DSA) with a slow acquisition rate. Treatment consists of embolization (aiming for complete occlusion of the shunting zone) or early surgical intervention.
• Spinal arteriovenous malformations (SAVMs): unlike fistulas, are supplied by spinal arteries and are prone to hemorrhage. They can be glomerular (tangle-like — nidus) and fistulous (direct shunts). Large clusters can additionally cause compressive myelopathy.

Class and exam questions

What else to study on this topic

• The role of electroneuromyography and cerebrospinal fluid analysis in confirming polyneuropathies
• Mechanisms of cross-reactive immune response of autoantibodies with myelin
• Technique of 4D dynamic MR angiography (TWIST) in vascular malformations
• Criteria for a negative digital subtraction angiography result when searching for fistulas
• Features and risks of embolization of spinal dural arteriovenous fistulas

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.