Neurofilament light chain (NFL) levels, which can be evaluated in cerebrospinal fluid and peripheral blood, are increased in several diseases characterized by acute or chronic neuronal damage, such as TBI [10], HIBI after cardiac arrest [11], subarachnoid hemorrhage [12], stroke [13], amyotrophic lateral sclerosis [14], Alzheimer’s disease [15], and in patients with Parkinson’s disease and cognitive impairment [16]. The gene discussed is NEFL; the disease is Parkinson disease.