Frontoparietal-Striatal Network and Nucleus Basalis Modulation in Patients With Parkinson Disease and Gait Disturbance.

BACKGROUND AND OBJECTIVES: Neural computations underlying gait disorders in Parkinson disease (PD) are multifactorial and involve impaired expression of stereotactic locomotor patterns and compensatory recruitment of cognitive functions. This study aimed to clarify the network mechanisms of cognitive contribution to gait control and its breakdown in patients with PD. METHODS: Patients with PD were instructed to walk at a comfortable pace on a mat with pressure sensors. The characterization of cognitive-motor interplay was enhanced by using a gait with a secondary cognitive task (dual-task condition) and a gait without additional tasks (single-task condition). Participants were scanned using 3-T MRI and 123I-ioflupane SPECT. RESULTS: According to gait characteristics, cluster analysis assisted by a nonlinear dimensionality reduction technique, t-distributed stochastic neighbor embedding, categorized 56 patients with PD into 3 subpopulations. The preserved gait (PG) subgroup (n = 23) showed preserved speed and variability during gait, both with and without additional cognitive load. Compared with the PG subgroup, the mildly impaired gait (MIG) subgroup (n = 16) demonstrated deteriorated gait variability with additional cognitive load and impaired speed and gait variability without additional cognitive load. The severely impaired gait (SIG) subgroup (n = 17) revealed the slowest speed and highest gait variability. In addition, group differences were found in attention/working memory and executive function domains, with the lowest performance in the SIG subgroup than in the PG and MIG subgroups. Using resting-state functional MRI, the SIG subgroup demonstrated lower functional connectivity of the left and right frontoparietal network (FPN) with the caudate than the PG subgroup did (left FPN, d = 1.21, p < 0.001; right FPN, d = 1.05, p = 0.004). Cortical thickness in the FPN and 123I-ioflupane uptake in the striatum did not differ among the 3 subgroups. By contrast, the severity of Ch4 density loss was significantly correlated with the level of functional connectivity degradation of the FPN and caudate (left FPN-caudate, r = 0.27, p = 0.04). DISCUSSION: These findings suggest that the functional connectivity of the FPN with the caudate, as mediated by the cholinergic Ch4 projection system, underlies the compensatory recruitment of attention and executive function for damaged automaticity in gait in patients with PD.

Motor Progression and Nigrostriatal Neurodegeneration in Parkinson Disease.

OBJECTIVE: The motor severity in Parkinson disease (PD) is believed to parallel dopaminergic terminal degeneration in the striatum, although the terminal was reported to be virtually absent by 4 years postdiagnosis. Meanwhile, neuromelanin-laden dopamine neuron loss in the substantia nigra (SN) elucidated a variability at early stages and gradual loss with less variability 10 years postdiagnosis. Here, we aimed to clarify the correlation between motor impairments and striatal dopaminergic terminal degeneration and nigral neuromelanin-laden dopamine neuron loss at early to advanced stages of PD. METHODS: Ninety-three PD patients were divided into early and advanced subgroups based on motor symptom duration and whether motor fluctuation was present. Striatal dopaminergic terminal degeneration was evaluated using a presynaptic dopamine transporter tracer, 123 I-ioflupane single photon emission computed tomography (SPECT). Nigral neuromelanin-laden dopamine neuron density was assessed by neuromelanin-sensitive magnetic resonance imaging (NM-MRI). RESULTS: In patients with early stage PD (motor symptoms for ≤8 or 10 years), motor dysfunction during the drug-off state was paralleled by a decline in 123 I-ioflupane uptake in the striatum despite the absence of a correlation with reductions in NM-MRI signals in SN. Meanwhile, in patients with advanced stage PD (motor symptoms for >8 or 10 years and with fluctuation), the degree of motor deficits during the drug-off state was not correlated with 123 I-ioflupane uptake in the striatum, despite its significant negative correlation with NM-MRI signals in SN. INTERPRETATION: We propose striatal dopaminergic terminal loss measured using 123 I-ioflupane SPECT and nigral dopamine neuron loss assessed with NM-MRI as early stage and advanced stage motor impairment biomarkers, respectively. ANN NEUROL 2022;92:110-121.

Incongruous, incomplete, homonymous hemianopia due to an infarction localized to the lateral geniculate body.

A 45-year-old male was admitted with an acute-onset visual field defect. Goldmann perimetry revealed an incongruent, incomplete right homonymous hemianopia. The left eye showed a wedge-shaped, horizontal right hemianopia, whereas the right eye showed constriction of the right visual hemifield. MRI showed acute infarction localized to the left lateral geniculate body (LGB). LGB has a dual blood supply: from the anterior choroidal artery and from the lateral posterior choroidal artery (LPChA). The LPChA territory of LGB receives projection from the retinal area around the macula and horizontal meridian. Therefore, an LPChA territory infarction of LGB can cause a wedge-shaped, horizontal visual field defect. The visual field defect in our patient would be caused by an LPChA territory infarction of LGB. Our patient showed an incongruent homonymous hemianopia. LGB has six laminae, with the ipsilateral retinal fibers terminating in layers two, three, and five and the crossed fibers terminating in layers one, four, and six. The laminar structure provides the anatomical basis for the incongruous visual field defects in a case of partial lesion of LGB. Based on the present data, we believe that an ischemic lesion localized to LGB should be considered in patients presenting with incongruous, incomplete homonymous hemianopia.

Normalization of sonographical multifocal nerve enlargements in a MADSAM patient following a good clinical response to intravenous immunoglobulin.

Focal nerve enlargements at sites of conduction blocks can be visualized sonographically in patients with multifocal acquired demyelinating sensory and motor neuropathy (MADSAM). However, little is known about association between nerve morphological changes and treatment responses. Here we present a 73-year-old female MADSAM patient whose sonographical multifocal nerve enlargements normalized following a good treatment response. She was admitted to our department with progressive asymmetrical muscle weakness and sensory disturbances for 6 months. Ultrasonography revealed multifocal nerve enlargements at sites of electrophysiological demyelination. Intravenous immunoglobulin improved her symptoms and electrophysiological abnormalities. Six months later, ultrasonography revealed normalization of multifocal nerve enlargements. Contrary to our observations, one previous report described a MADSAM patient with persistent nerve enlargements at the sites of resolved conduction blocks. In this earlier patient, however, the time from onset to remission was approximately 30 months. Morphological changes of nerve enlargements in MADSAM may vary with treatment response.

Dropped head syndrome preceding the onset of dementia with Lewy bodies.

A 67-year-old woman developed dropped head. Her neck was severely flexed, with prominent cervical paraspinal muscles, although no parkinsonism was observed. Brain MRI showed no significant findings. We considered dystonia as the cause of the dropped head and administered trihexyphenidyl, an anticholinergic. After 10 years of follow-up, remarkable psychotic symptoms, including hallucinations regarding insects, appeared. Following the discontinuation of trihexyphenidyl, the psychotic symptoms decreased but still remained. (123)I-N-isopropyl-p-iodoamphetamine single-photon emission computed tomography ((123)I-IMP SPECT) revealed hypoperfusion in the bilateral occipital lobes. We diagnosed the patient with dementia with Lewy bodies (DLB). This case suggests that dropped head syndrome may precede the onset of DLB.