Enlarging and shrinking focal perivascular spaces

BACKGROUND AND PURPOSE

Perivascular spaces (PVS) are interstitial fluid-filled spaces surrounding blood vessels traversing the deep gray nuclei and white matter of the brain. These are commonly encountered on CT and MR imaging and are generally asymptomatic and of no clinical significance. However, occasional changes in the size of focal PVS, for example, when enlarging, may mimic pathologies including neoplasms and infections, hence potentially confounding radiological interpretation. Given these potential diagnostic issues, we sought to better characterize common clinical and imaging features of focal PVS demonstrating size fluctuations.

MATERIALS AND METHODS

Upon institutional approval, we retrospectively identified 4 cases demonstrating PVS with size changes at our institution. To supplement our cases, we also performed a literature review, which identified an additional 14 cases. Their clinical and imaging data were analyzed to identify characteristic features.

RESULTS

Of the 18 total cases (including the 4 institutional cases), 10 cases increased and 8 decreased in size. These focal PVS ranged from 0.4-4.5 cm in size. Whereas a decrease in size did not represent a diagnostic issue, focal increase in size of PVS led to concerning differential diagnoses in at least 30% of the radiology reports. These enlarging PVS were most found in the basal ganglia and temporal lobe, and in patients with previous brain radiation treatment.

CONCLUSION

Focal size change of PVS can occur, especially years after brain radiation treatment. Being cognizant of this benign finding is important to consider in the differential diagnosis to avoid undue patient anxiety or unnecessary medical intervention.

Assessing the Emergence and Evolution of Artificial Intelligence and Machine Learning Research in Neuroradiology

BACKGROUND AND PURPOSE

Interest in artificial intelligence (AI) and machine learning (ML) has been growing in neuroradiology, but there is limited knowledge on how this interest has manifested into research and specifically, its qualities and characteristics. This study aims to characterize the emergence and evolution of AI/ML articles within neuroradiology and provide a comprehensive overview of the trends, challenges, and future directions of the field.

MATERIALS AND METHODS

We performed a bibliometric analysis of the American Journal of Neuroradiology (AJNR): the journal was queried for original research articles published since inception (Jan. 1, 1980) to Dec. 3, 2022 that contained any of the following key terms: "machine learning", "artificial intelligence", "radiomics", "deep learning", "neural network", "generative adversarial network", "object detection", or "natural language processing". Articles were screened by two independent reviewers, and categorized into Statistical Modelling (Type 1), AI/ML Development (Type 2), both representing developmental research work but without a direct clinical integration, or End-user Application (Type 3) which is the closest surrogate of potential AI/ML integration into day-to-day practice. To better understand the limiting factors to Type 3 articles being published, we analyzed Type 2 articles as they should represent the precursor work leading to Type 3.

RESULTS

A total of 182 articles were identified with 79% being non-integration focused (Type 1 n = 53, Type 2 n = 90) and 21% (n = 39) being Type 3. The total number of articles published grew roughly five-fold in the last five years, with the non-integration focused articles mainly driving this growth. Additionally, a minority of Type 2 articles addressed bias (22%) and explainability (16%). These articles were primarily led by radiologists (63%), with most of them (60%) having additional postgraduate degrees.

CONCLUSIONS

AI/ML publications have been rapidly increasing in neuroradiology with only a minority of this growth being attributable to end-user application. Areas identified for improvement include enhancing the quality of Type 2 articles, namely external validation, and addressing both bias and explainability. These results ultimately provide authors, editors, clinicians, and policymakers important insights to promote a shift towards integrating practical AI/ML solutions in neuroradiology.

ABBREVIATIONS

AI = artificial intelligence; ML = machine learning.

Successful magnetic resonance-guided focused ultrasound treatment of tremor in patients with a skull density ratio of 0.4 or less

OBJECTIVE

The use of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of tremor-related disorders and other novel indications has been limited by guidelines advocating treatment of patients with a skull density ratio (SDR) above 0.45 ± 0.05 despite reports of successful outcomes in patients with a low SDR (LSDR). The authors' goal was to retrospectively analyze the sonication strategies, adverse effects, and clinical and imaging outcomes in patients with SDR ≤ 0.4 treated for tremor using MRgFUS.

METHODS

Clinical outcomes and adverse effects were assessed at 3 and 12 months after MRgFUS. Outcomes and lesion location, volume, and shape characteristics (elongation and eccentricity) were compared between the SDR groups.

RESULTS

A total of 102 consecutive patients were included in the analysis, of whom 39 had SDRs ≤ 0.4. No patient was excluded from treatment because of an LSDR, with the lowest being 0.22. Lesioning temperatures (> 52°C) and therapeutic ablations were achieved in all patients. There were no significant differences in clinical outcome, adverse effects, lesion location, and volume between the high SDR group and the LSDR group. SDR was significantly associated with total energy (rho = -0.459, p < 0.001), heating efficiency (rho = 0.605, p < 0.001), and peak temperature (rho = 0.222, p = 0.025).

CONCLUSIONS

The authors' results show that treatment of tremor in patients with an LSDR using MRgFUS is technically possible, leading to a safe and lasting therapeutic effect. Limiting the number of sonications and adjusting the energy and duration to achieve the required temperature early during the treatment are suitable strategies in LSDR patients.

Computational modeling of whole-brain dynamics: a review of neurosurgical applications

A major goal of modern neurosurgery is the personalization of treatment to optimize or predict individual outcomes. One strategy in this regard has been to create whole-brain models of individual patients. Whole-brain modeling is a subfield of computational neuroscience that focuses on simulations of large-scale neural activity patterns across distributed brain networks. Recent advances allow for the personalization of these models by incorporating distinct connectivity architecture obtained from noninvasive neuroimaging of individual patients. Local dynamics of each brain region are simulated with neural mass models and subsequently coupled together, considering the subject's empirical structural connectome. The parameters of the model can be optimized by comparing model-generated and empirical data. The resulting personalized whole-brain models have translational potential in neurosurgery, allowing investigators to simulate the effects of virtual therapies (such as resections or brain stimulations), assess the effect of brain pathology on network dynamics, or discern epileptic networks and predict seizure propagation in silico. The information gained from these simulations can be used as clinical decision support, guiding patient-specific treatment plans. Here the authors provide an overview of the rapidly advancing field of whole-brain modeling and review the literature on neurosurgical applications of this technology.

Blocking effect of tricyclopinate on nicotinic receptors in cultured sympathetic neurons

AIM

To investigate the mechanism of tricyclopinate, an antagonist of nicotinic receptor, on neuronal nicotinic acetylcholine receptors (nAChR).

METHODS

A tight seal whole-cell recording patch-clamp technique was performed to record nicotine-evoked currents in the cultured sympathetic neurons from neonatal rat superior cervical ganglia (SCG).

RESULTS

Tricyclopinate inhibited the nicotine-induced currents competitively and the inhibition was voltage-independent. The decay of the nicotine-induced current was accelerated significantly in the presence of tricyclopinate.

CONCLUSION

Tricyclopinate inhibits neuronal nAChR by interacting with the allosteric sites rather than the open ionic channels or acetylcholine recognition site of the receptor.

Neostigmine competitively inhibited nicotinic acetylcholine receptors in sympathetic neurons

The present experiment investigates the effect of neostigmine on nicotinic acetylcholine receptors (nAChRs) in the cultured neurons from neonatal rat superior cervical ganglia (SCG). Using whole-cell patch clamp techniques, we found that the amplitudes of the currents induced by 50 microM dimethylphenylpiperazinium (DMPP) were 21.5+/-10.7%, 52.9+/-9.2% and 86.9+/-4.9% depressed at the increased concentrations of neostigmine 100, 200 and 400 microM, respectively. The inhibition of neostigmine decreased gradually with the increased concentration of nicotine from 10 to 160 microM. Lineweaver-Burk's double-reversible plot illustrated that neostigmine blocked neuronal nAChRs in a competitive manner. Hyperpolarization of membrane potential from -40 mV to -100 mV did not significantly influence the blockade of neostigmine. Neostigmine could not accelerate the decay of the DMPP-induced currents, neither evoke any detectable currents in SCG neurons. The results indicate that neostigmine depress neuronal nAChRs in a competitive, concentration-dependent and voltage-independent manner, and can not facilitate desensitization of the receptors. The present data suggest that neostigmine blocks neuronal nAChRs by interacting with the ACh binding sites of the receptors.

Physostigmine blocked nicotinic acetylcholine receptors in rat sympathetic ganglion neurons

AIM

To study the blocking mechanism of physostigmine (Phy) on nicotinic acetylcholine receptors (NAChR) in sympathetic neurons.

METHODS

The whole-cell patch-clamp technique was used to observe the effects of Phy on NAChR in the cultured sympathetic neurons from neonatal rat superior cervical ganglia (SCG).

RESULTS

Phy 5 -20 mumol.L-1 inhibited neuronal NAChR in a concentration-dependent manner and accelerated the desensitization of NAChR. Changing the membrane potential from -50 to -90 mV did not affect the blocking effect of Phy. Phy 200 mumol.L-1 did not induce any noticeable response in SCG neurons.

CONCLUSION

Phy blocked NAChR in the sympathetic ganglion neurons by interacting with the allosteric sites out of the binding sites and the open ionic channels of the receptors. Phy did not possess excitative effect on NAChR in SCG neurons.

Kinetic properties of nicotinic receptors in cultured rat sympathetic neurons from superior cervical ganglia

AIM

To analyze the kinetic properties of the effect of nicotine on nicotinic acetylcholine receptors (nAChR) in the cultured sympathetic neurons from neonatal rat superior cervical ganglia (SCG).

METHODS

The whole-cell recording method of patch-clamp technique was used to record the currents induced by different concentrations of nicotine. The concentration-response of nicotine was fitted with Clark equation.

RESULTS

Hill coefficient (1.097) was determined by fitting the nicotine responses of neuronal nAChR with Clark equation. The theoretical values of nicotine effect, calculated with Clark equation with H = 1, were basically identical with the practically recorded currents.

CONCLUSIONS

Interaction of nicotine and nAChR in rat SCG fits a single binding site model.

[45Ca-uptake, mitochondrial protein bound Ca2+ and ultrastructural distribution of Ca2+ in some brain regions of mice during drug-induced analgesia]

After buprenorphine (Bup, 0.8 mg/kg ip) treatment 45Ca-uptake (cpm/mg fresh brain) in vivo by brain slices decreased from 589 +/- 12 and 486 +/- 12 to 522 +/- 14 and 408 +/- 10 and mitochondrial protein bound Tb3+ (Tb3+ relative fluorescent intensity) reduced from 41 +/- 5 and 32 +/- 2 to 30 +/- 3 and 22 +/- 2 in periaqueductal grey and hypothalamus, respectively. A large amount dense precipitate occurred in the myelin sheath and mitochondria in both regions. The 45Ca-uptake evoked by buprenorphine at 16 micrograms/40 microliter in vitro has the similar tendency with that in vivo. Treated by ruthenium red (20 micrograms/mouse ip or icv) before buprenorphine, the above-mentioned effects were all abolished. Similar results were obtained with morphine (Mor, 10 mg/kg ip) and verapamil (Ver, 8 micrograms/mouse icv) instead of buprenorphine and ruthenium red, respectively. These results suggest that Ca2+ transport across neuroplasmic membranes plays a mediator role in drug-induced analgesia.