Nigrosomes

Dr Amir Rezaee and Dr Andrew Dixon et al.

Nigrosomes are small clusters of dopaminergic cells within the substantia nigra that exhibit calbindin D28K negativity on immunohistochemistry. Five nigrosomes measuring up to a few millimetres in size have been described with the largest labelled as nigrosome-1 1.

Nigrasome-1

Nigrosome-1 within the posterior third of the substantia nigra is able to be visualised on high resolution T2*/SWI weighted MRI. This nigrosome returns high signal on axial SWI in a linear or comma shape. It is surrounded anteriorly, laterally and medially by low SWI signal intensity which resembles the distinctive split tail of a swallow and hence is referred to as the swallow tail appearance

Nigrasome-1 contains the largest proportion of neurons affected in Parkinson's disease, a condition that causes the high SWI signal within nigrosome-1 to be absent. Absence of the normal swallow tail appearance of nigrosome-1 is reported to be a reliable sign of Parkinson's disease 1. There are two main possible mechanisms for this, increased iron content or decreased neuromelanin content with decreased iron storage capacity leading to more free iron with paramagnetic properties 2.

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Article Information

rID: 31108
Section: Anatomy
Synonyms or Alternate Spellings:

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