TABLE 3.
Consensus revision of individual cases with a clinico‐radiological paradox for the INO‐MLF
| Potential factors | Likelihood for contribution | |
|---|---|---|
| INO−MLF+ | INO+MLF− | |
| Technical and MRI‐related factors | ||
| 1. Lesion below MRI resolution | − | + |
| 2. MRI artefacts | + | + |
| 3. Age of lesion (acute more visible than chronic) | − | + |
| 4. Pure demyelination | − | + |
| 5. Pure axonal degeneration | − | + |
| 6. T1 black hole | − | + |
| 7. Astrogliosis | − | + |
| 8. Pre‐symptomatic lesion | + | − |
| 9. Remyelinated lesion | + | − |
| 10. Suboptimal image quality or image sequences | + | + |
| Anatomical | ||
| 1. Anatomical variation of MLF pathway | + | + |
| 2. Lesion closely adjacent to, but not interfering with, MLF | + | − |
| 3. Remote effect of adjacent lesions (e.g., by oedema, cytotoxic causes, conduction block) | − | + |
| 4. Aberrant blood vessel | − | + |
| 5. Altered conduction due to vestibular input to the MLF a | − | + |
| 6. Diffuse MS pathology | − | + |
| Other pathology | ||
| 1. Specific MLF autoimmunity (e.g., antibodies) | − | + |
| 2. Thin peri‐MLF lesion (analogous to perineuritis) | − | + |
| 3. Peri‐CSF space leukoaraiosis (perfusion disturbances) | − | + |
| 4. Other pathology (e.g., small cavernoma, pulse waves from blood vessels, vascular loops) | − | + |
| 5. Other causes for conduction block in MLF | − | + |
| Other | ||
| 1. Borderline INO cases, physiological variation in movement of adducting to abducting eye | + | − |
The list compiled summarizes factors which are speculated as potentially interesting for investigating one or both sides of the paradox (indicated by a + sign).
Abbreviations: CSF, cerebrospinal fluid; INO, internuclear ophthalmoplegia; INO+MLF−, internuclear ophthalmoplegia detected, no MLF lesion on MRI; INO−MLF+, no internuclear ophthalmoplegia detected, MLF lesion on MRI; MLF, medial longitudinal fasciculus; MRI, magnetic resonance imaging; MS, multiple sclerosis.
Efferent fibres of the vestibular system reach the nuclei of the three cranial nerves involved in eye movements via the MLF to enable visual fixation with auto locomotion. Disrupted vestibular input (e.g., due to a lesion in this pathway) might therefore influence conduction through the MLF.