Neurodegeneration of the Substantia Nigra after Ipsilateral Infarct: MRI R2* Mapping and Relationship to Clinical Outcome

Abstract

O utcomes after stroke may include motor, cognitive, and/ or emotional impairment (1,2). Some of these longterm sequelae are the result of the brain tissue injured by infarction. However, long-term clinical outcome may also be impacted by delayed neurodegeneration of remote but functionally or anatomically connected areas that become disconnected as a result of primary ischemic injury (3). The substantia nigra (SN) is one brain region suspected to be affected after infarction, in view of its large array of connections with the supratentorial brain. The striatum is connected to this structure through the nigrostriatal pathway (4,5), as are other parts of motor, limbic, and cognitive circuits (6). Overall, the SN is involved in motor control (7), regulation of emotions (8), cognition, and motivation through reward circuit (9). Whether secondary involvement of SN worsens overall clinical outcome after a supratentorial stroke has not previously been studied. Better techniques are required to understand the impact of supratentorial injury on the SN after stroke. At MRI, T2 hyperintensity (10) and/or reduction of apparent diffusion

A Preliminary Study of Alterations in Iron Disposal and Neural Activity in Ischemic Stroke

“…Our result was consistent with reported findings in previous studies [14,18,29,[54][55][56][57], where an increase in iron deposition level in basal ganglia and thalamus were confirmed poststroke. However, only Gattringer et al [58] did not observe a relationship between the damage severity and the increased iron deposition in DGM regions.…”

“…We observed partial improvements in the contralesional brain hemisphere, maybe due to an active reorganization [ 50 , 59 , 60 ]. There are also studies showing that motor performance is related to the amount of iron in the basal ganglia [ 56 ]. In our study, in all three patients, iron deposition level was decreased after rehabilitation accompanied with increasing the motor activation in fMRI, with a negative correlation.…”

Iron deposition in the precuneus is correlated with mild cognitive impairment in patients with cerebral microbleeds: A quantitative susceptibility mapping study

“…As far as is currently known, CMBs are similar to lacunar infarcts and WMH in that they can affect the cortex by decreasing the amount and intensity of connections in the structure network (Liu et al, 2020 ). According to the remote effect of cerebral infarction, we want to propose a hypothesis (Linck et al, 2019 ). Local microhemorrhage induces red cell lysis and releases hemoglobin.…”

Iron Deposition in Gray Matter Nuclei of Patients With Intracranial Artery Stenosis: A Quantitative Susceptibility Mapping Study

“…When degeneration of nerve fibers occurs in any of the above parts or nerve conduction function is damaged by insufficient blood supply, iron cannot be excreted normally and excessive iron can deposit accordingly ( 41 ). Linck et al ( 42 ) utilized R2 * mapping to explore iron alterations of SN in patients with supratentorial ischemic stroke, and found that SN ipsilateral to the lesion presented greater iron content 1 year after stroke. Indeed, our results of both ACAS and PCAS patients could indirectly demonstrate the existence of known fibrous pathways between SN and basal ganglia.…”