Prognosis in substance abuse-related acute toxic leukoencephalopathy: A scoping review

Decrease in injection and rise in smoking and snorting of heroin and synthetic opioids, 2000-2021

BACKGROUND

Injecting, smoking, and snorting heroin/synthetic opioids is each associated with unique health risks. It is unclear how route of administration (ROA) preferences have shifted during the opioid epidemic.

METHODS

Using 2000-2021 admissions data from SAMHSA TEDS-A, we analyzed trends in heroin/synthetic opioid ROA preferences and factors associated with these preferences.

RESULTS

7,881,318 heroin/synthetic opioid admissions reported injection, smoking, or snorting preference. Nationally, injection peaked in 2014 (69.9 %) and nadired in 2021(52.2 %), snorting nadired in 2014 (24.9 %) and peaked in 2021 (36.4 %), and smoking rose steadily from 2.5 % in 2005 to a peak of 11.4 % in 2021. From 2000-2021, the number of states with ≥10 % smoking rates grew from 2 to 27 (highest: 57.0 % in Arizona in 2021). In 2021, increased adjusted prevalence ratios (APR) of non-injection versus injection use were associated with older age at first opioid use (APR 1.52 [95 % CI: 1.51, 1.54] for those 30+ relative to ≤20), and all race/ethnicities relative to non-Latino White individuals (highest: Black individuals, APR 1.77 [1.75, 1.78]). Geography strongly predicted smoking versus snorting (Mountain APR 6.91 [6.64, 7.19], Pacific APR 6.61 [6.35, 6.88], reference: New England).

CONCLUSIONS

ROA preferences of heroin/synthetic opioids have changed substantially since 2000, with: 1) recent decreases in injection nationally; 2) increased smoking, particularly in the western US; and, 3) recent increased snorting in the eastern US. Smoking is now prevalent and growing. Public health implications include an increasing number of smoking-related fatal overdoses and the probable reduction of injection-specific morbidity and increase in smoking-specific morbidity.

Clinical and neuroradiographic features of fentanyl inhalation-induced leukoencephalopathy

A man in his late 40s with no known past medical history was unresponsive for an unknown period of time. Crushed pills and white residue were found on a nearby table. On presentation he was obtunded and unresponsive to verbal commands but withdrawing to painful stimuli. The initial urine drug screen was negative, but a urine fentanyl screen was subsequently positive with a level of 137.3 ng/mL. MRI of the brain showed reduced diffusivity and fluid attenuated inversion recovery (FLAIR) hyperintensity symmetrically in the bilateral supratentorial white matter, cerebellum and globus pallidus. Alternative diagnoses such as infection were considered, but ultimately the history and workup led to a diagnosis of fentanyl-induced leukoencephalopathy. Three days after admission the patient became able to track, respond to voice and follow basic one-step commands. The patient does not recall the mechanism of inhalation. While there are case reports of heroin-induced leukoencephalopathy following inhaled heroin use and many routes of fentanyl, this is the first reported case of a similar phenomenon due to fentanyl inhalation.

Molecular Mechanisms Underlying Neuroinflammation Elicited by Occupational Injuries and Toxicants

Occupational injuries and toxicant exposures lead to the development of neuroinflammation by activating distinct mechanistic signaling cascades that ultimately culminate in the disruption of neuronal function leading to neurological and neurodegenerative disorders. The entry of toxicants into the brain causes the subsequent activation of glial cells, a response known as 'reactive gliosis'. Reactive glial cells secrete a wide variety of signaling molecules in response to neuronal perturbations and thus play a crucial role in the progression and regulation of central nervous system (CNS) injury. In parallel, the roles of protein phosphorylation and cell signaling in eliciting neuroinflammation are evolving. However, there is limited understanding of the molecular underpinnings associated with toxicant- or occupational injury-mediated neuroinflammation, gliosis, and neurological outcomes. The activation of signaling molecules has biological significance, including the promotion or inhibition of disease mechanisms. Nevertheless, the regulatory mechanisms of synergism or antagonism among intracellular signaling pathways remain elusive. This review highlights the research focusing on the direct interaction between the immune system and the toxicant- or occupational injury-induced gliosis. Specifically, the role of occupational injuries, e.g., trips, slips, and falls resulting in traumatic brain injury, and occupational toxicants, e.g., volatile organic compounds, metals, and nanoparticles/nanomaterials in the development of neuroinflammation and neurological or neurodegenerative diseases are highlighted. Further, this review recapitulates the recent advancement related to the characterization of the molecular mechanisms comprising protein phosphorylation and cell signaling, culminating in neuroinflammation.

White matter dementia then… and now

White matter dementia (WMD) is a concept introduced in 1988 to highlight the importance of white matter pathology in producing cognitive dysfunction and dementia. Whereas gray matter, particularly the cerebral cortex, has been primarily investigated in the dementias, subcortical pathology has long been correlated with cognitive loss, and a corticocentric perspective cannot account for the full range of neurobehavioral disorders. Within the subcortical regions, white matter is prominent, accounting for about half the volume of the adult brain, and many white matter diseases, injuries, and intoxications can produce cognitive dysfunction so severe as to justify the term dementia. Recognition of this novel syndrome relied heavily on the introduction of magnetic resonance imaging (MRI) that permitted in vivo visualization of white matter lesions. Neuropsychological studies clarified the clinical presentation of WMD by identifying a profile dominated by cognitive slowing and executive dysfunction, and a precursor syndrome of mild cognitive dysfunction was proposed to identify early cognitive impairment that may later evolve to WMD. As knowledge advanced, the role of white matter in structural connectivity within distributed neural networks was elucidated. In addition, highlighting the frequent commingling of gray and white matter involvement, white matter pathology was associated with neurodegenerative diseases such as Alzheimer's disease and chronic traumatic encephalopathy, with potentially transformative clinical implications. In particular, preventive measures and treatments exploiting white matter restoration and plasticity are gaining much attention. Today, WMD has matured into a concept that not only integrates knowledge from across the spectrum of clinical neuroscience, but also informs new investigations into many perplexing disorders and enables a more complete understanding of brain-behavior relationships.