9.4 T MR microscopy of the substantia nigra with pathological validation in controls and disease

Abstract

BackgroundThe anatomy of the substantia nigra on conventional MRI is controversial. Even using histological techniques it is difficult to delineate with certainty from surrounding structures. We sought to define the anatomy of the SN using high field spin-echo MRI of pathological material in which we could study the anatomy in detail to corroborate our MRI findings in controls and Parkinson's disease and progressive supranuclear palsy.Methods23 brains were selected from the Queen Square Brain Bank (10 controls, 8 progressive supranuclear palsy, 5 Parkinson's disease) and imaged using high field 9.4 Tesla spin-echo MRI. Subsequently brains were cut and stained with Luxol fast blue, Perls stain, and immunohistochemistry for substance P and calbindin. Once the anatomy was defined on histology the dimensions and volume of the substantia nigra were determined on high field magnetic resonance images.ResultsThe anterior border of the substantia nigra was defined by the crus cerebri. In the medial half it was less distinct due to the deposition of iron and the interdigitation of white matter and the substantia nigra. The posterior border was flanked by white matter bridging the red nucleus and substantia nigra and seen as hypointense on spin-echo magnetic resonance images. Within the substantia nigra high signal structures corresponded to confirmed nigrosomes. These were still evident in Parkinson's disease but not in progressive supranuclear palsy. The volume and dimensions of the substantia nigra were similar in Parkinson's disease and controls, but reduced in progressive supranuclear palsy.ConclusionsWe present a histologically validated anatomical description of the substantia nigra on high field spin-echo high resolution magnetic resonance images and were able to delineate all five nigrosomes. In accordance with the pathological literature we did not observe changes in the nigrosome structure as manifest by volume or signal characteristics within the substantia nigra in Parkinson's disease whereas in progressive supranuclear palsy there was microarchitectural destruction.

Differential involvement of nigral subregions in idiopathic parkinson's disease

“…By taking advantage of a high contrast‐to‐noise ratio (CNR) of SMWI along with a high spatial resolution (0.5 × 0.5 × 1.0 mm 3 ), we were able to identify both the nigrosome 1 and the putative nigrosome 4 regions at 3 T MRI. These regions are similar in terms of their shapes and locations to those in the previous histological study [Damier et al, ] and the study at ultra‐high‐field MRI [Massey et al, ].…”

“…Based on the recent study by Massey et al [], we defined the nigrosome 1 region as the central hyperintensity between two hypointense regions in the dorsal SN, which was assessed from the level of the anterior border of the red nucleus to the posterior end of the SN (Fig. A,B,D).…”

“…A,B,D). As only a small part of the putative nigrosome 1 region exists at the level of lower 1/3 of the red nucleus [Massey et al, ], and it is less conspicuously identified than the rest of the putative nigrosome 1 region below the red nucleus (Fig. D), the latter region was only assessed for nigrosome 1 (hereafter, the putative nigrosome 1 region below the level of the red nucleus was designated as nigrosome 1).…”

“…Recently, a new method, susceptibility map‐weighted imaging (SMWI), has been demonstrated to provide high‐quality images of the SN with nigral hyperintensity in vivo at 3 T [Nam et al, ]. A recent study by taking advantage of high‐resolution and high‐field (9.4 T) ex vivo SWI images successfully identified all five nigrosome subregions [Massey et al, ]. With this information on the locations of each nigrosome subregion and by utilizing SMWI, we hypothesized that we may identify nigrosome 1, 3, and 4 separately in in vivo, thereby validating the histological outcomes of the previous study [Damier et al, ] using a large number of in‐vivo data, and we may also be able to test if there is any differential involvement of nigrosome subregions according to disease status.…”

Microvessels may Confound the “Swallow Tail Sign” in Normal Aged Midbrains: A Postmortem 7 T SW‐MRI Study

“…Therefore, transverse MR relaxometry may be an additional tool for the separate evaluation of neuromelanin and iron distributions with the progression of PD . Massey et al have recently used 9.4 T MR microscopy with spin echo technique to define SN anatomy . In accordance with the pathological literature, SN dimensions have been found by these authors to be similar in PD specimen and controls, but reduced in progressive supranuclear palsy …”