Tuesday, October 30, 2007

Sleep Board Tip #3

Congenital Central Hypoventilation Syndrome (CCHS) is linked to mutations in the homeobox gene Phox2B.
In some families CCHS exhibits autosomal dominant transmission.

Sleep Board Tip #2

End Tidal CO2 is often used to aid in the diagnosis of OSA in children.

Various parameters are listed in the literature. The one that will probably appear on the boards is:
ETCO2> 50 mm Hg for >10% TST is abnormal

Sleep Board Tip # 1

The new sleep boards are coming up in mid-November. Here is something that will probably appear on the exam:

Shy-Drager Syndrome ( a subset of Multiple System Atrophy) is a Parkinsonian syndrome with prominent autonomic failure.
Respiratory dysrhythmias during sleep are common in Multiple System Atrophy (and are even more common in Shy-Drager syndrome), especially NOCTURNAL STRIDOR, which can be fatal. This is a result of vocal cord dysfunction- Posterior Cricoarytenoid Muscles- the abductors of the vocal cords. Treatment includes obligatory cpap or tracheostomy. Respiratory dysrhythmias due to Shy-Drager syndrome can also result in nocturnal awakenings, sleep disruption, and hypersomnia.

(This info was covered during the AASM 2007 Chicago Board Review course)

Thursday, October 18, 2007

Fish can get Insomnia too

Yahoo News reports that Zebrafish lacking a hypocretin receptor sleep 30% less than fish without this mutation:
LOS ANGELES (Reuters) - Fish might not have eyelids, but they do sleep, and some suffer from insomnia, scientists reported on Monday.

California scientists studying sleep disorders in humans found that some zebrafish, a common aquarium pet, have a mutant gene that disrupts their sleep patterns in a way similar to insomnia in humans.

Zebrafish with the mutant gene slept 30 percent less than fish without the mutation. When they finally drifted off they remained asleep half as long as the normal fish, the researchers at the Stanford University School of Medicine said.

The mutant fish lacked a working receptor for hypocretin, a neuropeptide that is secreted in normal fish by neurons in the region of the brain that controls hunger, sex and other basic behaviors.

The researchers, led by Emmanuel Mignot, said they would look for fish that have a mutation that causes them to oversleep or never sleep in the hope of discovering if sleep-regulating molecules and brain networks developed through evolution.

The study was published in Tuesday's edition of the Public Library of Science-Biology.

Hypocretin is the neurochemical linked to the narcolepsy-cataplexy syndrome; human narcoleptics (with cataplexy) have a hypocretin deficiency. Disturbed, fragmented nocturnal sleep is a common, underrecognized symptom of narcolepsy.

Narcolepsy without cataplexy is a poorly understood condition and we sleep doctors have no idea what causes most cases of this condition.

Monday, October 15, 2007

The Uvula

A tribute to the uvula (via Kevin MD).

Today (10/22), Dr. Rob blogs about the pharynx, which is very important to sleep specialists.

Wednesday, October 03, 2007

Opioids and sleep apnea

Opioids such as methadone are well known to cause central sleep apnea. Sleep Review Magazine reports a high rate of obstructive and central sleep apnea in patients who use opioids for chronic pain:
Sleep-disordered breathing is very common in patients who use opioids for chronic pain conditions, according to a report issued online September 6th by the journal Pain Medicine.
Of the 147 patients
on chronic opioid therapy who agreed to undergo testing, 140 had data available for analysis, the report indicates.
"The biggest finding was an extraordinarily high prevalence of sleep-disordered breathing in opioid-treated chronic pain patients," Dr. Webster noted. "Obstructive and central sleep apnea syndromes occurred in the studied population at a far greater rate (75%) than is observed in the general population."
The most common type of sleep apnea, seen in 39% of all patients, was the obstructive type, followed by central sleep apnea in 24%, central and obstructive sleep apnea in 8%, and indeterminate type in 4%.
The apnea-hypopnea index was directly related to the daily dosage of methadone, but not to that of other opioids (p = 0.002). The central apnea index was directly linked to the daily dosage of both methadone (p = 0.008) and benzodiazepines (p = 0.004).
It is interesting that in this study methadone appeared to have a greater effect on sleep apnea than other opioids.
I run a
suboxone clinic to treat persons addicted to opioids. I'll have to increase my monitoring of their sleep.