sleep apnea

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Cognitive and Structural Gray Matter Deficits Linked to OSA

Laurie Barclay, MD

November 16, 2010 — Cognitive and structural gray matter deficits linked to

obstructive sleep apnea (OSA) may be reversible with continuous positive

airway pressure (CPAP), according to the results of a study reported online

October 29 in the American Journal of Respiratory & Critical Care Medicine.

" OSA patients demonstrate several neuropsychological impairments, but

current knowledge of the brain structures affected by OSA is limited, " said

corresponding author Vincenza Castronovo, PhD, clinical psychologist at the

Sleep Disorders Center, Vita-Salute San Raffaele University and San Raffaele

Scientific Institute in Milan, Italy, in a news release. " This study

provides the first evidence that structural brain abnormalities exist in

regions

susceptible to hypoxemia, and they can change with treatment. "

The goal of the study was to assess the cognitive deficits and the

corresponding brain morphologic changes in OSA and changes after treatment,

using

combined neuropsychological testing and Voxel-Based-Morphometry in 17

treatment-naive patients with OSA and 15 age-matched healthy control subjects.

Sleep study, cognitive tests, and magnetic resonance imaging were performed

in all participants at baseline, and cognitive testing and magnetic

resonance imaging were repeated after 3 months of treatment.

Before CPAP treatment, patients with OSA had impairments in most cognitive

areas, as well as in mood and sleepiness, which were associated with focal

reductions of gray-matter volume in the left hippocampus (enthorinal

cortex), left posterior parietal cortex, and right superior frontal gyrus.

" We found reduced GM-[gray matter]volume in the OSA group when compared to

the non-OSA group in several key regions of the brain, " Dr. Castronovo

said. " Of particular note were the deficits in the left parahippocampal gyrus

and in the left posterior-parietal cortex. We found that these two regions

have significant bearing on abstract reasoning and executive function.

Deficits in the left posterior-parietal cortex were also shown to be associated

with daytime sleepiness. "

After treatment, there were significant improvements in memory, attention,

and executive functioning, and parallel increases in gray-matter volumes in

the hippocampal and frontal structures.

" These results suggest a scenario in which the hippocampus, due to its

sensitivity to hypoxia and innervation of small vessels, is the region that is

most strongly and quickly affected by hypoxic episodes, " Dr. Castronovo

said. " The mechanism of the observed brain changes could be either neurogenic

or vasogenic. We propose it to be vasogenic. "

Limitations of this study include failure to reevaluate healthy control

participants at 3 months and lack of generalizability to nonhypoxic sleepy

patients.

" Next, our group will focus on increasing our understanding of brain damage

and recovery, " Dr. Castronovo concluded. " We want to evaluate non-hypoxic

sleep disordered breathing in sleepy patients to assess the role of hypoxia

in structural brain involvement. "

Respironics Foundation, Pittsburgh, Pennsylvania, supported this study.

The study authors have disclosed no relevant financial relationships.

Am J Respir Crit Care Med. Published online October 29, 2010.

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