Monday, December 31, 2012

Best Post of July 2012: "Chasing The Dragon": A Cause of Toxic Spongiform Leukoencephalopathy

The next in our "Best of the Month" series comes from July 10, 2012:


My favorite case from the 2012 AANP Diagnostic Slide Session in Chicago last month featured an autopsy slide from the brain of a 25-year-old man with a history of polysubstance abuse found unresponsive at a New Year's Eve party. Toxicology screening was positive for methadone, lorazepam, and cocaine. The patient died after three weeks in the intensive care unit. Attendees were provided glass slides in advance of the session demonstrating the following findings:
Low Power: Marked white matter pallor

High Power: White matter virtually replaced by lipidized macrophages
Presenter Joshua Menke, MD of The Mayo Clinic (Rochester, MN) revealed that white matter damage was diffuse, including infratentorial structures. The subcortical U-fibers were relatively spared and myelin was disproportionately affected as compared to axons, as demonstrated in these photomicrographs from Dr. Menke's presentation:
LFB stain on left and neurofilament stain on right
Discussants included Drs. Tessa Hedley-Whyte, Craig Horbinski, Mark Cohen, and others. Before the diagnosis was revealed, Dr. Horbinski stated that he thought Delayed Hypoxic Leukoencephalopathy might be the best fit for this case. Dr. Cohen pointed out that Delayed Hypoxic Leukoencephalopathy tends spare the infratentorial regions, while the white matter damage is more diffusely distributed in toxic leukoencephalopathy. This case was ultimately revealed to be that of Toxic Spongiform Leukoencephalopathy.

Toxic leukoencephalopathy can be caused by a range of insults including radiation, chemotherapy, and drugs of abuse. Among the drugs of abuse that have been shown to cause toxic leukoencephalopathy are toluene, ethanol, cocaine, 3,4-methylenedioxy-methamphetamine, intravenous heroin, inhaled heroin pyrolysate, and psilocybin (Ref: Filley & Kleinschmidt-DeMasters NEJM 2001). Toxic spongiform leukoencephalopathy is a clinicopathologic entity first associated with the inhalation of pyrolysate heroin vapors, a practice which had its origins in Hong Kong in the 1950's and which came to be known colloquially as "chasing the dragon". Users typically "chase the dragon" by placing heroin on a creased piece of tin foil over a flame. As the drug sublimates, the user inhales the fumes. The pathophysiology of this form of leukoencephalopathy has not been clearly elucidated, but is thought to be related to a direct toxic effect of heroin on oligodendrocytes.

Friday, December 21, 2012

Best Post of June 2012: Neuropathologists party hard at AANP Annual Reception

The next in our "Best of the Month" series comes from June 22, 2012 and recalls fond memories of an excellent annual meeting of the American Association of Neuropathologists this past summer in Chicago:

L to R: Drs. Heather Sumner and T. David Bourne
Drs. Mark Cohen, T. David Bourne, and Mahtab Tehrani
L to R: Drs. Edward Stopa, William Taylor, and Qian Wu



Friday, December 14, 2012

What is this vagus stuff?

Henry A. Lester, PhD
Actually, it's Vagusstoff (literally translated from German as "Vagus Substance") refers to the substance released by stimulation of the vagus nerve which causes a reduction in the heart rate. Discovered in 1921 by physiologist Otto Loewi, vagusstoff was the first confirmation of chemical synaptic transmission and the first neurotransmitter ever discovered. It was later confirmed to be acetylcholine, which was first identified by Sir Henry Hallett Dale in 1914. Because of his pioneering experiments, in 1936 Loewi was awarded the Nobel Prize in Physiology or Medicine, which he shared with Dale. Thanks to Dr. Henry Lester of Cal Tech for informing me of this interesting bit of neuro-history through his free online course entitled "Drugs and The Brain". The information provided here is taken from the Wikipedia article on the topic.

Tuesday, December 4, 2012

"the NFL is a breeding ground for mental illness" -- Former Denver Bronco Nate Jackson

Today, a friend forwarded me this opinion piece about the murder-suicide of NFL linebacker Jovan Belcher. I responded that I blogged about such cases before, and I didn't intend to write yet another blog post about chronic traumatic encephalopathy. I felt as though lethal violence among football players is happening so often now, it's not even worth yet another post. But, the fact that the violence has reached this level of banality is in itself worthy of comment. Don't worry, though, the next time an NFL player commits homicide or suicide, I promise not to write about it.