Histological and magnetic resonance analysis of sciatic nerves in the tellurium model of neuropathy

Abstract

Ingestion of tellurium (Te), a toxic element, produces paralysis of the hind limbs in weanling rats that is due to temporary, segmental demyelination of the sciatic nerves bilaterally. Weanling rats were fed a 1.1% elemental Te diet and sacrificed at various time points for histological and magnetic resonance (MR) analysis of the sciatic nerves. No controls exhibited impairments of the hind limbs, whereas Te-treated animals became progressively impaired with increased Te exposure. Toluidine blue-stained nerve sections of Te-treated animals showed widened endoneurial spaces, disrupted myelin sheaths, swollen Schwann cells, and a few instances of axonal degeneration. Te decreased healthy myelin by 68% and increased percent extracellular matrix by 45% on day 7. MR experiments showed a decrease in the area of the short T2 component, an increase in average T1, and an increase in the position of the intermediate T2 component in Te-treated nerves. The correlation coefficient for healthy myelin and average T1 was 0.88 and that for healthy myelin and the area underneath the short T2 component was 0.77. The area of the short T2 component has been postulated as the best measure of the process of demyelination.

Multicenter measurements of myelin water fraction and geometric mean T2: Intra‐ and intersite reproducibility

“…Measures associated with the IE water pool can also offer further insight into pathology. One group found that both inflammation and tellurium‐induced demyelination in rat sciatic nerve caused the IE peak to shift to higher T 2 s . Barnes et al demonstrated, using a two‐point method for T 2 calculation, that the presence of edema in cat brain can lead to a lengthening in T 2 , likely due to an increase in IE T 2 .…”

Myelin water imaging to detect demyelination and remyelination and its validation in pathology

“…In addition to the above mentioned human validation studies, a number of animal studies have also demonstrated a strong correlation between myelin water and various myelin histological stains in both peripheral nervous system and CNS animal models .…”

T1, T2 relaxation and magnetization transfer in tissue at 3T

“…Moreover, T 1 , T 2 , and MT provide quantitative assessment of tissue pathology. In particular, they offer additional information about the processes of demyelination and axonal loss (1)(2)(3)(4), inflammation (5), infarction (6), white matter edema (7), tumor malignancy (8), and ischemia (9). Both tissue relaxation and MT parameter estimates are important in designing MRI pulse sequences that aim to accentuate contrast between normal and pathologic tissue.…”