Background Visual snow syndrome (VSS) is a neurological condition characterized by persistent flickering dots in the visual fields, palinopsia, enhanced entoptic phenomenon, photophobia, and nyctalopia. Neuroimaging evidence supports the role of the visual association cortex in visual snow syndrome. Case series: We provided clinical care to three patients with visual snow syndrome, in whom [123I]-IMP single-photon emission computed tomography (SPECT) imaging was performed. Case 1 was a 21-year-old male with a past history of migraine with aura who exhibited visual snow and entoptic phenomenon. In this patient, [123I]-IMP SPECT imaging revealed right occipital and temporal hypoperfusion with a distribution matching the ventral visual stream. [123I]-IMP SPECT imaging detected only mild bilateral frontal hypoperfusion in Case 2 and no overt abnormalities in Case 3. Conclusion Although visual snow syndrome seems to be a heterogenous condition, our observations indicate that abnormal visual processing within the ventral visual stream may play a role in the pathogenesis of this condition.

Most national highways in rural parts of Hokkaido, Japan, are two-way, two-lane roads. On these highways, passing maneuvers that involve the use of the oncoming lane are frequently observed. Such passing is observed even when road surfaces are covered with compacted snow. To optimize speed and safety, simulated passing maneuvers have been conducted to make use of the oncoming lane of a two-way, two-lane highway. No such traffic simulations, however, have taken into consideration the surface conditions of roads in winter (e.g., snow-covered, icy, with poor visibility caused by snowfall and fog). In this study, a traffic flow simulation to model passing maneuvers that involved the oncoming lane was created through the use of values measured in a passing-maneuver field survey conducted on a two-lane road in summer and winter. The field values for the number of passing maneuvers, traffic volume, and speed distribution were compared with the simulation results. The outcomes confirmed that the difference between them was small. The sensitivity analysis results revealed that the number of passing maneuvers on surfaces covered with compacted snow under conditions of poor visibility did not increase as much as they did on dry surfaces, even when the traffic volume in the original lane was higher. The passing success rate tended to decrease with higher volumes of traffic in the oncoming lane, regardless of surface conditions.

Only few studies have assessed brain shift caused by positional change. This study aimed to identify factors correlated with a large postneurosurgical positional brain shift (PBS). Sixty-seven patients who underwent neurosurgical procedures had upright computed tomography (CT) scan using settings similar to those of conventional supine CT. The presence of a clinically significant PBS, defined as a brain shift of ≥ 5 mm caused by positional change, was evaluated. The clinical and radiological findings were investigated to identify factors associated with a larger PBS. As a result, twenty-one patients had a clinically significant PBS. The univariate analysis showed that supratentorial lesion location, intra-axial lesion type, craniectomy procedure, and residual intracranial air were the predictors of PBS. Based on the multivariate analysis, craniectomy procedure (p < 0.001) and residual intracranial air volume (p = 0.004) were the predictors of PBS. In a sub-analysis of post-craniectomy patients, PBS was larger in patients with supratentorial craniectomy site and parenchymal brain injury. A large craniectomy area and long interval from craniectomy were correlated with the extent of PBS. In conclusion, patients who undergo craniectomy and those with residual intracranial air can present with a large PBS. In post-craniectomy patients, the predisposing factors of a large PBS are supratentorial craniectomy, presence of parenchymal injury, large skull defect area, and long interval from craniectomy. These findings can contribute to safe mobilization among postneurosurgical patients and the risk assessment of sinking skin flap syndrome.