SARS-CoV-2 vaccine-related neurological complications.

OBJECTIVE: To describe three cases with neurological symptoms after SARS-CoV-2 vaccination. METHODS: A case series followed by a review of the literature, describing hypotheses on how neurological symptoms might develop after vaccination. RESULTS: The different temporal relationship between the onset or worsening of different neurological symptoms suggests different pathophysiological mechanisms. Progression of post-infectious myoclonus, caused by a previous SARS-CoV-2-infection, shortly after vaccination suggests a renewed auto-immune mediated crossreaction of antibodies to both viral epitopes and central nervous system components. Thunderclap headache after vaccination suggests a similar pathophysiological mechanism to the headache and other flu-like symptoms described after vaccination against other viruses. This might be ascribed to the activation of immunoinflammatory mediators or accompanying fever. Although headache accompanied by encephalopathy and focal neurological deficit might occur as part of a cytokine release syndrome, this is clinically less likely. CONCLUSIONS: A variety of symptoms, including thunderclap headache, focal deficits and movement disorders, can occur after SARS-CoV-2 vaccination, and an activation or reactivation of the immune system is suggested as most likely cause. However, one should be careful about claiming a direct correlation. It remains important to exclude other causes, such as structural lesions, infections or subarachnoid hemorrhage, and future research is required to understand possible pathophysiological mechanisms and associations with the SARS-CoV-2 vaccine.

Attenuated neural response to gamble outcomes in drug-naive patients with Parkinson's disease.

Parkinson's disease results from the degeneration of dopaminergic neurons in the substantia nigra, manifesting as a spectrum of motor, cognitive and affective deficits. Parkinson's disease also affects reward processing, but disease-related deficits in reinforcement learning are thought to emerge at a slower pace than motor symptoms as the degeneration progresses from dorsal to ventral striatum. Dysfunctions in reward processing are difficult to study in Parkinson's disease as most patients have been treated with dopaminergic drugs, which sensitize reward responses in the ventral striatum, commonly resulting in impulse control disorders. To circumvent this treatment confound, we assayed the neural basis of reward processing in a group of newly diagnosed patients with Parkinson's disease that had never been treated with dopaminergic drugs. Thirteen drug-naive patients with Parkinson's disease and 12 healthy age-matched control subjects underwent whole-brain functional magnetic resonance imaging while they performed a simple two-choice gambling task resulting in stochastic and parametrically variable monetary gains and losses. In patients with Parkinson's disease, the neural response to reward outcome (as reflected by the blood oxygen level-dependent signal) was attenuated in a large group of mesolimbic and mesocortical regions, comprising the ventral putamen, ventral tegmental area, thalamus and hippocampus. Although these regions showed a linear response to reward outcome in healthy individuals, this response was either markedly reduced or undetectable in drug-naive patients with Parkinson's disease. The results show that the core regions of the meso-cortico-limbic dopaminergic system, including the ventral tegmental area, ventral striatum, and medial orbitofrontal cortex, are already significantly compromised in the early stages of the disease and that these deficits cannot be attributed to the contaminating effect of dopaminergic treatment.

Depression and quality of life in monogenic compared to idiopathic, early-onset Parkinson's disease.

Quality of life (QoL) is decreased in PD and is linked with depression and anxiety. However, little is known about QoL in monogenic PD. Subjects with mutations in PD genes were recruited from ongoing family and genetic studies (manifesting carriers, n = 23; nonmanifesting carriers, n = 19). For comparison purposes, we included patients with idiopathic PD (IPD; n = 128; early onset, n = 38; late onset, n = 90), healthy controls (n = 127), and data on depressive symptoms of 144 patients with major depression (treated controls). Depression affected 31% of early-onset PD cases, 21% of late-onset cases, and 44% of manifesting carriers of mutations in PD genes, but was rare in the nonmanifesting carriers (7%) and healthy controls (5%). Subjects with Parkinson-associated depression reported fewer feelings of guilt or self-doubt than treated controls, but the occurrence of suicidal ideation was associated with severity of depression only. Social phobia (P = 0.018) and agoraphobia (P = 0.059) were more common in manifesting carriers than in any other group. QoL was decreased in the Parkinson groups, particularly in the early-onset cases (P < 0.001), and QoL correlated with depression in all analyses. In our study, monogenic and IPD cases were comparable in QoL and depression characteristics. The QoL and, possibly, overall prognosis of all PD patients can be improved by appropriate attention and treatment for depression, sleep impairments, and anxiety, even if the treatment of the motor problems cannot be further optimized.

Impaired sense of smell and color discrimination in monogenic and idiopathic Parkinson's disease.

Olfaction is typically impaired in idiopathic Parkinson's disease (IPD), but its role is uncertain in monogenic PD. Diminished color discrimination has been suggested as another early sign of dopaminergic dysfunction but not been systematically studied. Furthermore, it is unknown whether both deficits are linked. We examined 100 patients with IPD, 27 manifesting mutation carriers (MC), 20 nonmanifesting mutation carriers (NMC), and 110 controls. Participants underwent a standardized neurological examination, the University of Pennsylvania Smell Identification Test (UPSIT), the Farnsworth-Munsell (FM) color discrimination test, and mutation testing in known PD genes. The monogenic group consisted of 15 Parkin (6MC/9NMC), 17 PINK1 (10MC/7NMC), 8 LRRK2 (4MC/4NMC), 3 SNCA (MC), and 4 ATP13A2 (MC) carriers. Olfaction was most impaired in IPD (UPSIT percentiles 10.1 ± 13.5) compared with all other groups (MC 13.8 ± 11.9, NMC 19.6 ± 13.0, controls 33.8 ± 22.4). Within MC, carriers of two mutations in Parkin and PINK1 showed higher UPSIT percentiles than LRRK2 and SNCA carriers. Color discrimination was reduced in IPD (FM total error score 134.8 ± 92.7). In MC (122.4 ± 142.4), the reduction was most pronounced in LRRK2, NMC (80.0 ± 38.8) were comparable with controls (97.2 ± 61.1). UPSIT and FM scores were correlated in the control (r = -0.305; P = 0.002) and the IPD group (r = -0.303; P = 0.006) but not among mutation carriers. First, we confirmed olfaction and color discrimination to be impaired in IPD and suggest olfaction to be a premotor sign. Second, olfaction differed between carriers with one and two mutations in Parkin/PINK1-associated PD. Third, olfaction and color discrimination impairment do not necessarily evolve in parallel.

Dopamine agonist treatment increases sensitivity to gamble outcomes in the hippocampus in de novo Parkinson's disease.

BACKGROUND: Parkinson's disease is associated with severe nigro-striatal dopamine depletion, leading to motor dysfunction and altered reward processing. We previously showed that drug-naïve patients with Parkinson's disease had a consistent attenuation of reward signalling in the mesolimbic and mesocortical system. Here, we address the neurobiological effects of dopaminergic therapy on reward sensitivity in the mesolimbic circuitry, and how this may contribute to neuropsychiatric symptoms. OBJECTIVES: We tested the hypothesis that (1) dopaminergic treatment would restore the attenuated, mesolimbic and mesocortical responses to reward; and (2) restoration of reward responsivity by dopaminergic treatment would predict motor performance and the emergence of impulse control symptoms. METHODS: In 11 drug-naïve Parkinson patients, we prospectively assessed treatment-induced changes in reward processing before, and eight weeks after initiation of monotherapy with dopamine agonists. They were compared to 10 non-medicated healthy controls who were also measured longitudinally. We used whole-brain functional magnetic resonance imaging at 3 Tesla to assess the reward responsivity of the brain to monetary gains and losses, while participants performed a simple consequential gambling task. RESULTS: In patients, dopaminergic treatment improved clinical motor symptoms without significantly changing task performance. Dopamine agonist therapy induced a stronger reward responsivity in the right hippocampus with higher doses being less effective. None of the patients developed impulse control disorders in the follow-up period of four years. CONCLUSIONS: Short-term treatment with first-ever dopaminergic medication partially restores deficient reward-related processing in the hippocampus in de novo Parkinson's disease.

Mapping preclinical compensation in Parkinson's disease: an imaging genomics approach.

Mutations in the Parkin (PARK2) and PINK1 gene (PARK 6) can cause recessively inherited Parkinson's disease (PD). The presence of a single Parkin or PINK1 mutation is associated with a dopaminergic nigrostriatal dysfunction and conveys an increased risk to develop PD throughout lifetime. Therefore neuroimaging of non-manifesting individuals with a mutant Parkin or PINK1 allele opens up a window for the investigation of preclinical and very early phases of PD in vivo. Here we review how functional magnetic resonance imaging (fMRI) can be used to identify compensatory mechanisms that help to prevent development of overt disease. In two separate experiments, Parkin mutation carriers displayed stronger activation of rostral supplementary motor area (SMA) and right dorsal premotor cortex (PMd) during a simple motor sequence task and anterior cingulate motor area and left rostral PMd during internal movement selection as opposed to externally cued movements. The additional recruitment of the rostral SMA and right rostral PMd during the finger sequence task was also observed in a separate group of nonmanifesting mutation carriers with a single heterozygous PINK1 mutation. Because mutation carriers were not impaired at performing the task, the additional recruitment of motor cortical areas indicates a compensatory mechanism that effectively counteracts the nigrostriatal dysfunction. These first results warrant further studies that use these imaging genomics approach to tap into preclinical compensation of PD. Extensions of this line of research involve fMRI paradigms probing nonmotor brain functions. Additionally, the same fMRI paradigms should be applied to nonmanifesting mutation carriers in genes linked to autosomal dominant PD. This will help to determine how "generically" the human brain compensates for a preclinical dopaminergic dysfunction.

Nonmotor symptoms in genetic Parkinson disease.

OBJECTIVES: To review current knowledge on nonmotor symptoms (NMS), particularly psychiatric features, in genetic Parkinson disease (PD) and to provide original data for genetic and idiopathic PD. DATA SOURCES: A MEDLINE search using Parkinson and known PD genes focused on the presence of depression, anxiety, hallucinations, and dementia was performed. Original data from 82 outpatients with idiopathic (n = 55) and genetic (n = 27) PD were obtained. STUDY SELECTION: All studies including information on NMS and patients with genetic PD. DATA EXTRACTION: Study methods and clinical and genetic information were summarized. DATA SYNTHESIS: The literature search yielded 1855 citations; 305 included genetic information on PD patients, of which 119 also contained information on any type of NMS (990 cases). Availability of information varied by gene and type of NMS; studies differed by recruitment and examination method. Literature search and original data showed high frequencies of the following NMS: depression, 8% to 37% (literature) and 33% to 40% (our data); anxiety, 7% to 37% (literature) and 10% to 22% (our data); hallucinations, 3% to 23% (literature) and 23% to 29% (our data); and dementia, 5% to 26% (literature), absent in our own data. CONCLUSIONS: Data on NMS in genetic PD are limited. Specific data needs include a systematic approach to NMS assessment reporting permitting comparability of studies. Overall, the frequency of NMS in genetic PD does not appear to be higher and may even be lower than in idiopathic PD. Nonmotor symptoms have a high impact on the patients' quality of life and caregiver burden and should be considered important and often treatable concomitant features of genetic PD.

Recessively inherited parkinsonism: effect of ATP13A2 mutations on the clinical and neuroimaging phenotype.

OBJECTIVE: To determine clinical features and to identify changes in brain structure and function in compound heterozygous and heterozygous ATP13A2 mutation carriers. DESIGN: Prospective multimodal clinical and neuroimaging study. SETTING: University of Lübeck, Lübeck, Germany. PARTICIPANTS: Eight family members of a large Chilean pedigree with Kufor-Rakeb syndrome (KRS). INTERVENTIONS: Clinical characterization, dopamine transporter (DAT) imaging, voxel-based morphometry (VBM), and transcranial sonography (TCS). MAIN OUTCOME MEASURES: Frequency of parkinsonian signs, brain structure, and functional alterations. RESULTS: The only available patient with compound heterozygous KRS showed a markedly reduced striatal DAT density bilaterally. Magnetic resonance imaging revealed severe global brain atrophy as well as iron deposition in the basal ganglia. The heterozygous mother had definite parkinsonism with reduced DAT density in both putamina. While all asymptomatic heterozygous siblings displayed subtle extrapyramidal signs, DAT imaging revealed striatal tracer uptake within physiological levels. Voxel-based morphometry revealed an increase in gray matter volume in the right putamen and a decrease in the cerebellum of the heterozygous carriers. In all mutation carriers, the substantia nigra had a normal appearance on TCS. CONCLUSIONS: Single ATP13A2 heterozygous mutations may be associated with clinical signs of parkinsonism and contribute to structural and functional brain changes. Lack of hyperechogenicity in the substantia nigra may be a distinctive feature of this form of genetic parkinsonism. This, along with the finding of iron in the basal ganglia in our patient with KRS, implies a different underlying pathophysiology compared with other monogenic forms of parkinsonism and idiopathic PD and may place KRS among the syndromes of neurodegeneration with brain iron accumulation (NBIA).