Different cortical excitability profiles in hereditary brain iron and copper accumulation
Background and aim
Neurodegeneration with brain iron accumulation (NBIA) and Wilson’s disease (WD) is considered the prototype of neurodegenerative disorders characterised by the overloading of iron and copper in the central nervous system. Growing evidence has unveiled the involvement of these metals in brain cortical neurotransmission. Aim of this study was to assess cortical excitability profile due to copper and iron overload.
Three patients affected by NBIA, namely two patients with a recessive hereditary parkinsonism (PARK9) and one patient with aceruloplasminemia and 7 patients with neurological WD underwent transcranial magnetic stimulation (TMS) protocols to assess cortical excitability. Specifically, we evaluated the motor thresholds that reflect membrane excitability related to the voltage-gated sodium channels in the neurons of the motor system and the ease of activation of motor cortex via glutamatergic networks, and ad hoc TMS protocols to probe inhibitory-GABAergic (short interval intracortical inhibition, SICI; short-latency afferent inhibition, SAI; cortical silent period, CSP) and excitatory intracortical circuitry (intracortical facilitation, ICF).
Patients with NBIA exhibited an abnormal prolongation of CSP respect to HC and WD patients. On the contrary, neurological WD displayed higher motor thresholds and reduced CSP and SICI.
Hereditary conditions due to overload of copper and iron exhibited peculiar cortical excitability profiles that can help during differential diagnosis between these conditions. Moreover, such results can give us more clues about the role of metals in acquired neurodegenerative disorders, such as Parkinson disease, Alzheimer disease, and multiple sclerosis.
KeywordsNeurodegeneration Metals Wilson’s disease NBIA TMS GABA
Transcranial magnetic stimulation
Short-latency afferent inhibition
Short interval intracortical inhibition
Resting motor threshold
Active motor threshold
Cortical silent period
Magnetic resonance imaging
Positron emission tomography
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The protocol was approved by the local ethics committee, and the research was conducted in accordance with the 1964 Declaration of Helsinki.
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